This document discusses keratorefractive surgeries. It begins by describing the anatomy of the cornea, including the epithelium, Bowman's layer, stroma, Descemet's membrane, and endothelium. It then provides a brief history of keratorefractive surgeries and classifications including location, addition, subtraction, relaxation, and compression techniques. Common keratorefractive surgeries discussed include PRK, LASEK, LASIK, epikeratophakia, keratophakia, and excimer laser procedures. Complications, indications, and the role of techniques like corneal topography and wavefront analysis are also summarized.
Intracorneal ring segments, such as INTACS, are thin plastic rings that are implanted into the corneal stroma to flatten the cornea and reduce myopia. They are placed in a lamellar channel using either a mechanical or laser procedure. Thicker rings provide greater flattening and myopia correction. Potential risks include visual disturbances and complications requiring removal. Intracorneal rings have been used off-label to treat conditions like post-LASIK ectasia and keratectasia with some success in improving vision.
Sir Harold Ridley was the first to successfully implant an intraocular lens in 1949 using polymethylmethacrylate (PMMA). Early intraocular lenses had high complication rates of dislocation and glaucoma. The evolution of intraocular lens design led to foldable lenses made of silicone and acrylic materials that are implanted in the capsular bag for better stability and lower complication rates. Modern multifocal and toric intraocular lenses provide patients with independence from glasses by correcting presbyopia and astigmatism. Precise biometry and surgical technique are important for optimal outcomes with premium intraocular lenses.
The document describes the use of various Pentacam maps and indices for screening patients for keratoconus, including:
1) The standard 4-map composite report, keratoconus map, Holladay report, and Belin/Ambrosio Enhanced Ectasia Display.
2) Key features to examine on each map include anterior and posterior elevation maps, pachymetry maps, curvature maps, and indices values.
3) The Belin/Ambrosio Enhanced Ectasia Display aims to improve sensitivity by calculating an "enhanced" best fit sphere reference surface that excludes the thinnest corneal region, highlighting differences between normal and ectatic corneas.
This document discusses the corneal endothelium and techniques for assessing its health and function. The corneal endothelium is a single layer of hexagonal cells that maintains corneal clarity by pumping fluid out of the stroma. Assessment techniques described include specular microscopy, which allows analysis of endothelial cell density, morphology, and patterns under high magnification; confocal microscopy; anterior segment OCT; and ultrasound pachymetry to measure corneal thickness as an indicator of endothelial function. Common indications for assessment include pre- and post-operative evaluation, and evaluation of donor corneas for transplantation.
The Implantable Collamer Lens (ICL) is a soft, flexible, posterior chamber phakic intraocular lens made of collagen-copolymer material called Collamer. Studies have shown ICL implantation is safe and effective for correcting myopia between -3 to -25 diopters and astigmatism up to -6 diopters. It provides stable refractive results with few complications over 4 years. Toric ICL models were found to be superior to LASIK in safety, efficacy, predictability and stability for high myopic astigmatism. The procedure is reversible and preserves corneal tissue, reducing risks compared to LASIK.
This document discusses various vitreous substitutes and intraocular gases used to replace the vitreous humor after surgery. It describes the anatomy and composition of the natural vitreous and ideal properties for substitutes. Common substitutes discussed include gases like air, sulfur hexafluoride and perfluorocarbons; liquids like silicone oil, perfluorocarbon liquids and semi-fluorinated alkanes; and experimental polymers and implants. The document compares different options and provides details on how each works, associated complications, and appropriate uses.
The cornea is the main refractive element of the eye, contributing 70% of the eye's refractive power. Even minor changes to its shape can significantly alter the image formed on the retina. The cornea has an elliptical anterior surface and a circular posterior surface. It varies in thickness from center to periphery. Corneal topography is used to map the shape of the cornea using various techniques such as Placido disk, elevation-based, and Scheimpflug imaging. Topography provides quantitative data on corneal curvature, thickness, and irregularities that aid in diagnosing conditions like keratoconus.
Intracorneal ring segments, such as INTACS, are thin plastic rings that are implanted into the corneal stroma to flatten the cornea and reduce myopia. They are placed in a lamellar channel using either a mechanical or laser procedure. Thicker rings provide greater flattening and myopia correction. Potential risks include visual disturbances and complications requiring removal. Intracorneal rings have been used off-label to treat conditions like post-LASIK ectasia and keratectasia with some success in improving vision.
Sir Harold Ridley was the first to successfully implant an intraocular lens in 1949 using polymethylmethacrylate (PMMA). Early intraocular lenses had high complication rates of dislocation and glaucoma. The evolution of intraocular lens design led to foldable lenses made of silicone and acrylic materials that are implanted in the capsular bag for better stability and lower complication rates. Modern multifocal and toric intraocular lenses provide patients with independence from glasses by correcting presbyopia and astigmatism. Precise biometry and surgical technique are important for optimal outcomes with premium intraocular lenses.
The document describes the use of various Pentacam maps and indices for screening patients for keratoconus, including:
1) The standard 4-map composite report, keratoconus map, Holladay report, and Belin/Ambrosio Enhanced Ectasia Display.
2) Key features to examine on each map include anterior and posterior elevation maps, pachymetry maps, curvature maps, and indices values.
3) The Belin/Ambrosio Enhanced Ectasia Display aims to improve sensitivity by calculating an "enhanced" best fit sphere reference surface that excludes the thinnest corneal region, highlighting differences between normal and ectatic corneas.
This document discusses the corneal endothelium and techniques for assessing its health and function. The corneal endothelium is a single layer of hexagonal cells that maintains corneal clarity by pumping fluid out of the stroma. Assessment techniques described include specular microscopy, which allows analysis of endothelial cell density, morphology, and patterns under high magnification; confocal microscopy; anterior segment OCT; and ultrasound pachymetry to measure corneal thickness as an indicator of endothelial function. Common indications for assessment include pre- and post-operative evaluation, and evaluation of donor corneas for transplantation.
The Implantable Collamer Lens (ICL) is a soft, flexible, posterior chamber phakic intraocular lens made of collagen-copolymer material called Collamer. Studies have shown ICL implantation is safe and effective for correcting myopia between -3 to -25 diopters and astigmatism up to -6 diopters. It provides stable refractive results with few complications over 4 years. Toric ICL models were found to be superior to LASIK in safety, efficacy, predictability and stability for high myopic astigmatism. The procedure is reversible and preserves corneal tissue, reducing risks compared to LASIK.
This document discusses various vitreous substitutes and intraocular gases used to replace the vitreous humor after surgery. It describes the anatomy and composition of the natural vitreous and ideal properties for substitutes. Common substitutes discussed include gases like air, sulfur hexafluoride and perfluorocarbons; liquids like silicone oil, perfluorocarbon liquids and semi-fluorinated alkanes; and experimental polymers and implants. The document compares different options and provides details on how each works, associated complications, and appropriate uses.
The cornea is the main refractive element of the eye, contributing 70% of the eye's refractive power. Even minor changes to its shape can significantly alter the image formed on the retina. The cornea has an elliptical anterior surface and a circular posterior surface. It varies in thickness from center to periphery. Corneal topography is used to map the shape of the cornea using various techniques such as Placido disk, elevation-based, and Scheimpflug imaging. Topography provides quantitative data on corneal curvature, thickness, and irregularities that aid in diagnosing conditions like keratoconus.
UBM and ASOCT provide high-resolution cross-sectional images of the anterior segment including the cornea, anterior chamber, angle, and iris. ASOCT uses optical coherence tomography with a wavelength of 1310nm for improved penetration and reduced retinal damage compared to posterior segment OCT. It allows high-speed imaging of dynamic structures. ASOCT has applications in assessing corneal diseases and procedures, glaucoma (including angle anatomy and iridotomy evaluation), and intraocular lens implantation. Measurements of angle width parameters help evaluate angle closure risk. While valuable for objective angle assessment, ASOCT cannot image all anatomical structures involved in glaucoma.
Intraocular lenses have evolved significantly from the early rigid lens designs implanted in the 1950s. Modern intraocular lenses are classified based on location, design, and material. Premium lens options include multifocal lenses that provide multiple focal points for both distance and near vision, toric lenses that correct astigmatism, and accommodating lenses designed to restore the eye's ability to focus on near objects. Proper patient selection is important for multifocal lenses, considering an individual's lifestyle and visual needs.
The document discusses various formulas used for calculating intraocular lens (IOL) power, including SRK, SRK2, Holladay, Haigis, and Holladay 2. It explains the factors these formulas account for such as axial length, corneal power, anterior chamber depth, and how they have evolved over generations to improve accuracy. Special considerations for calculating IOL power in cases involving prior refractive surgery, silicone oil filling, posterior staphyloma, and using optical biometry devices are also summarized.
This document discusses the surgical management of Pellucid marginal degeneration (PMD), a non-inflammatory thinning of the cornea. It describes various surgical techniques used to treat PMD including INTACS inserts, eccentric penetrating keratoplasty, large diameter epikeratoplasty, lamellar crescentic keratoplasty, lamellar crescentic resection, and wedge resection. The goal of these surgeries is to reshape the cornea and reduce high astigmatism caused by PMD through techniques like inserting inserts, excising the thinned area, or using donor tissue grafts. Complications can include increased risk of rejection, vascularization, and long-term astigmatism changes.
The document discusses refractive surgeries and provides details on LASIK (Laser-Assisted In Situ Keratomileusis) specifically. It summarizes that LASIK combines lamellar corneal surgery using a microkeratome to create a corneal flap with excimer laser ablation of corneal stroma beneath the flap. The procedure involves creating a corneal flap using a microkeratome, ablating the stroma with an excimer laser according to a calculated profile, and repositioning the flap. Complications are minimized as the flap protects underlying tissues from the laser.
This document discusses the anatomy and development of the vitreous humor in the eye. It begins by describing the embryological origin of vitreous cells from surface ectoderm, neuroectoderm, and mesodermal tissues. During the primary vitreous stage, the vitreous body begins forming before closure of the choroidal fissure and appears as a fibrillated secretion filling the vitreous space. The document then covers the general features, structure including hyaloid layers, cortical and medullary regions, attachments, composition and transport processes of the mature vitreous humor. It concludes by describing the physicochemical properties and factors affecting expansion and contraction of the vitreous gel.
This document discusses biometry, which involves measuring the eye to determine the ideal intraocular lens power for cataract surgery. It notes that biometry errors are the second most common cause of claims in cataract malpractice cases. It describes various techniques for measuring the corneal curvature and axial length of the eye, including manual and automated keratometry, ultrasound A-scan, and optical biometers. It also discusses considerations for biometry in special cases and different intraocular lens calculation formulas.
Gonioscopy is a technique used to examine the anterior chamber angle of the eye using specialized lenses and prisms to evaluate structures like the trabecular meshwork, ciliary body band, and schleem's canal. Different classification systems are used to describe gonioscopic findings and the anatomical relationship between structures. Gonioscopy is useful for diagnosing and managing glaucoma as well as other angle abnormalities through examination of the angle.
This document provides guidelines for prescribing glasses in children. It discusses that the pediatric eye is different from the adult eye in terms of axial length, corneal curvature, and lens power. The goals of prescribing glasses in children are to provide a focused retinal image and achieve optimal balance between accommodation and convergence. It is more difficult to prescribe glasses for children due to lack of subjective response and poor attention. American guidelines provide recommendations on refractive errors that warrant correction at different ages. Factors like emmetropization, amblyopia risk, and presence of strabismus are considered. Frame selection depends on the child's condition and age, aiming for correct fit, comfort, safety, and not hindering nasal development.
Various laser lenses have been introduced following Goldmann 3- mirror and Goldmann fundus contact lens for retinal photocoagulation.
Below described some of the time-tested lenses in widespread use. Precise knowledge of these lenses is necessary for safe retinal photocoagulation.
Update knowledge about Muntifocal IOL made by Asaduzzaman
Working as Associate Optometrist in Ispahani Islamia Eye Institute &Hospita, Dhaka 1215
Email:asad.optom92@yaho. com
This document discusses surgical induced astigmatism following cataract surgery. It notes that astigmatism has a significant impact on vision and is influenced by surgical technique and incision size and type. Various factors can induce astigmatism including incision location and size, suture type and placement, and wound compression or gape. Evaluating astigmatism involves tools like retinoscopy, keratometry and corneal topography. Managing astigmatism may involve selective suture removal to reduce cylindrical error over time.
Vitreous substitutes are substances used during vitreoretinal surgery to re-establish intraocular volume, assist with separating membranes from the retina, and manipulate and flatten detached retina. They are also used postoperatively as long-term tamponading agents to maintain the retina in apposition. Common vitreous substitutes used include balanced salt solution, air, viscoelastic fluids, silicone liquid, and perfluorocarbon liquids. Gases such as air, SF6, and C3F8 are employed during retinal detachment surgery to provide internal tamponade and are chosen based on their duration, expansion properties, and buoyancy effects. Complications can include increased intraocular pressure, lens opac
Posterior vitreous detachment (PVD) occurs when the vitreous gel in the eye separates from the retina. It is a natural aging process that usually happens in people's 60s and 70s. PVDs are often asymptomatic, but can sometimes cause floaters, flashes of light, or a cobweb-like visual effect. While PVD itself does not affect vision, on rare occasions it can cause retinal tears or detachments, which require prompt treatment to prevent vision loss if left untreated. PVD is typically diagnosed via dilated eye exam but may also require tests like OCT or ultrasound. No treatment is needed for most PVDs but follow up exams are recommended to check for complications.
Choroidal neovascular membranes (CNVM)Md Riyaj Ali
Choroidal neovascularization (CNV) involves the abnormal growth of new blood vessels from the choroid layer of the eye through Bruch's membrane. This can cause vision loss and is a common cause of wet macular degeneration. CNV occurs due to alterations in Bruch's membrane and high levels of vascular endothelial growth factor. It is classified based on its location relative to the retinal pigment epithelium and fovea. Symptoms include sudden vision loss and visual distortions. CNV is diagnosed through imaging like optical coherence tomography and fluorescein angiography and treated with injections of anti-VEGF drugs to inhibit blood vessel growth.
The document discusses implantable contact lenses (ICL) for correcting high refractive errors. Key points include:
- ICL is preferred over LASIK for high myopia or thin corneas, as it has fewer risks of complications.
- ICL is made of a biocompatible collamer material and is implanted in the posterior chamber behind the iris.
- A clinical trial found nearly 60% of eyes achieved 20/20 vision and 95% achieved 20/40 vision or better after 3 years with ICL implantation.
- Complications are generally low but can include cataracts, increased eye pressure, damage to the natural lens, and other rare issues like infections. Most risks are
Keratoconus is a non-inflammatory, progressive thinning and protrusion of the cornea that results in irregular astigmatism and decreased vision. It typically presents after puberty with no gender or racial predilection. Diagnosis is made based on corneal thinning, Fleischer ring, Vogt's striae, and irregular astigmatism seen on keratometry and topography. Mild cases are managed with spectacles while more severe cases require rigid gas permeable contact lenses, Intacs, or corneal transplantation.
The Scheimpflug principle allows for imaging of the anterior eye segment with maximal depth of focus. Scheimpflug systems like the Pentacam and Orbscan use this principle to provide detailed tomography and topography maps of the cornea and anterior chamber. The Pentacam uses a rotating Scheimpflug camera combined with a static camera to construct a 3D model from 25,000 data points. It analyzes parameters like corneal thickness, curvature, astigmatism, and anterior chamber dimensions. The Orbscan uses slit scanning to create elevation maps of the anterior and posterior corneal surfaces and measure pachymetry. Both devices help evaluate conditions like keratoconus and guide refractive surgery planning.
This document describes different types of artificial anterior chambers used in corneal transplantation surgeries. It discusses reusable chambers like the Moria AAC and disposable chambers like the Barron Disposable AAC. The Moria ALTK system allows adjustment of the diameter of the donor corneal resection, while the Barron AAC maintains pressure on the donor cornea during lamellar dissection or trephination. Both systems involve placing the donor cornea on the chamber, adjusting intrachamber pressure, and then performing the corneal resection.
Specular microscopy is used to examine the corneal endothelium and analyze pathological changes. There are contact and non-contact types, with contact providing higher resolution but potential discomfort. The procedure involves placing the patient comfortably and using fixation to keep the eye still while obtaining images. Images are then analyzed to study normal endothelium morphology, diagnose corneal endothelial diseases, and monitor conditions like aging, diabetes, surgery, trauma, and compare surgical techniques. Specular microscopy can detect disorders like Fuchs' endothelial dystrophy and help with decisions like eye banking and surgery.
This document summarizes different types of corneal refractive surgery procedures. It describes the anatomy and physiology of the cornea, including its layers and shape. It then discusses various laser eye surgery procedures like LASIK, PRK, LASEK, Epi-LASIK, and intrastromal corneal ring implants. For each procedure, it provides a brief overview and lists the advantages and disadvantages. The goal of these surgeries is to correct refractive errors like myopia, hyperopia, and astigmatism by reshaping the cornea through ablation or incisions.
Current Trends in Refractive Surgery - Lecture given at Harvard by Emil Chynn...parkavenuelasek
Dr. Chynn graduated from Harvard's ophthalmology program, which is probably the most famous in the world.
As the only member of his graduating class to specialize in Refractive Surgery, and now an recognized authority, Dr. Chynn is frequently invited back to Harvard to give updates on the State of the Art in Refractive Surgery.
This slide show presentation was given to 100 eye surgeons who flew in from across the country to learn the latest advances in glaucoma, retina, cataract surgery--and laser vision correction (from Dr. Chynn).
The title of his talk reflects the movement in the US and worldwide from leading surgeons that is called "Back to the Surface." This means that surgeons are moving away from LASIK and IntraLase, to avoid flap complications and the # 1 problem causing lawsuits (iatrogenic keratoconus, or KC), and back to the surface.
For some doctors, this means going back to the original procedure, PRK, which has a lot of pain, delayed healing, and scarring.
For Dr. Chynn, this means performing an Advanced Surface Ablation, which is either a LASEK or epiLASEK. These are more advanced than PRK because they do not hurt, healing and recovery is quick, and there is no haze or scarring.
For example, Dr. Chynn performs over 1,000 LASEKs and epiLASEKs per year--he performed his last PRK in 1999.
Obviously, he moved away from PRK to LASIK, then to IntraLase, and now back to the safer LASEK and epiLASEK procedures.
View the following slide show to find out more, and call us with your questions--better yet, come in and meet with our MDs!
UBM and ASOCT provide high-resolution cross-sectional images of the anterior segment including the cornea, anterior chamber, angle, and iris. ASOCT uses optical coherence tomography with a wavelength of 1310nm for improved penetration and reduced retinal damage compared to posterior segment OCT. It allows high-speed imaging of dynamic structures. ASOCT has applications in assessing corneal diseases and procedures, glaucoma (including angle anatomy and iridotomy evaluation), and intraocular lens implantation. Measurements of angle width parameters help evaluate angle closure risk. While valuable for objective angle assessment, ASOCT cannot image all anatomical structures involved in glaucoma.
Intraocular lenses have evolved significantly from the early rigid lens designs implanted in the 1950s. Modern intraocular lenses are classified based on location, design, and material. Premium lens options include multifocal lenses that provide multiple focal points for both distance and near vision, toric lenses that correct astigmatism, and accommodating lenses designed to restore the eye's ability to focus on near objects. Proper patient selection is important for multifocal lenses, considering an individual's lifestyle and visual needs.
The document discusses various formulas used for calculating intraocular lens (IOL) power, including SRK, SRK2, Holladay, Haigis, and Holladay 2. It explains the factors these formulas account for such as axial length, corneal power, anterior chamber depth, and how they have evolved over generations to improve accuracy. Special considerations for calculating IOL power in cases involving prior refractive surgery, silicone oil filling, posterior staphyloma, and using optical biometry devices are also summarized.
This document discusses the surgical management of Pellucid marginal degeneration (PMD), a non-inflammatory thinning of the cornea. It describes various surgical techniques used to treat PMD including INTACS inserts, eccentric penetrating keratoplasty, large diameter epikeratoplasty, lamellar crescentic keratoplasty, lamellar crescentic resection, and wedge resection. The goal of these surgeries is to reshape the cornea and reduce high astigmatism caused by PMD through techniques like inserting inserts, excising the thinned area, or using donor tissue grafts. Complications can include increased risk of rejection, vascularization, and long-term astigmatism changes.
The document discusses refractive surgeries and provides details on LASIK (Laser-Assisted In Situ Keratomileusis) specifically. It summarizes that LASIK combines lamellar corneal surgery using a microkeratome to create a corneal flap with excimer laser ablation of corneal stroma beneath the flap. The procedure involves creating a corneal flap using a microkeratome, ablating the stroma with an excimer laser according to a calculated profile, and repositioning the flap. Complications are minimized as the flap protects underlying tissues from the laser.
This document discusses the anatomy and development of the vitreous humor in the eye. It begins by describing the embryological origin of vitreous cells from surface ectoderm, neuroectoderm, and mesodermal tissues. During the primary vitreous stage, the vitreous body begins forming before closure of the choroidal fissure and appears as a fibrillated secretion filling the vitreous space. The document then covers the general features, structure including hyaloid layers, cortical and medullary regions, attachments, composition and transport processes of the mature vitreous humor. It concludes by describing the physicochemical properties and factors affecting expansion and contraction of the vitreous gel.
This document discusses biometry, which involves measuring the eye to determine the ideal intraocular lens power for cataract surgery. It notes that biometry errors are the second most common cause of claims in cataract malpractice cases. It describes various techniques for measuring the corneal curvature and axial length of the eye, including manual and automated keratometry, ultrasound A-scan, and optical biometers. It also discusses considerations for biometry in special cases and different intraocular lens calculation formulas.
Gonioscopy is a technique used to examine the anterior chamber angle of the eye using specialized lenses and prisms to evaluate structures like the trabecular meshwork, ciliary body band, and schleem's canal. Different classification systems are used to describe gonioscopic findings and the anatomical relationship between structures. Gonioscopy is useful for diagnosing and managing glaucoma as well as other angle abnormalities through examination of the angle.
This document provides guidelines for prescribing glasses in children. It discusses that the pediatric eye is different from the adult eye in terms of axial length, corneal curvature, and lens power. The goals of prescribing glasses in children are to provide a focused retinal image and achieve optimal balance between accommodation and convergence. It is more difficult to prescribe glasses for children due to lack of subjective response and poor attention. American guidelines provide recommendations on refractive errors that warrant correction at different ages. Factors like emmetropization, amblyopia risk, and presence of strabismus are considered. Frame selection depends on the child's condition and age, aiming for correct fit, comfort, safety, and not hindering nasal development.
Various laser lenses have been introduced following Goldmann 3- mirror and Goldmann fundus contact lens for retinal photocoagulation.
Below described some of the time-tested lenses in widespread use. Precise knowledge of these lenses is necessary for safe retinal photocoagulation.
Update knowledge about Muntifocal IOL made by Asaduzzaman
Working as Associate Optometrist in Ispahani Islamia Eye Institute &Hospita, Dhaka 1215
Email:asad.optom92@yaho. com
This document discusses surgical induced astigmatism following cataract surgery. It notes that astigmatism has a significant impact on vision and is influenced by surgical technique and incision size and type. Various factors can induce astigmatism including incision location and size, suture type and placement, and wound compression or gape. Evaluating astigmatism involves tools like retinoscopy, keratometry and corneal topography. Managing astigmatism may involve selective suture removal to reduce cylindrical error over time.
Vitreous substitutes are substances used during vitreoretinal surgery to re-establish intraocular volume, assist with separating membranes from the retina, and manipulate and flatten detached retina. They are also used postoperatively as long-term tamponading agents to maintain the retina in apposition. Common vitreous substitutes used include balanced salt solution, air, viscoelastic fluids, silicone liquid, and perfluorocarbon liquids. Gases such as air, SF6, and C3F8 are employed during retinal detachment surgery to provide internal tamponade and are chosen based on their duration, expansion properties, and buoyancy effects. Complications can include increased intraocular pressure, lens opac
Posterior vitreous detachment (PVD) occurs when the vitreous gel in the eye separates from the retina. It is a natural aging process that usually happens in people's 60s and 70s. PVDs are often asymptomatic, but can sometimes cause floaters, flashes of light, or a cobweb-like visual effect. While PVD itself does not affect vision, on rare occasions it can cause retinal tears or detachments, which require prompt treatment to prevent vision loss if left untreated. PVD is typically diagnosed via dilated eye exam but may also require tests like OCT or ultrasound. No treatment is needed for most PVDs but follow up exams are recommended to check for complications.
Choroidal neovascular membranes (CNVM)Md Riyaj Ali
Choroidal neovascularization (CNV) involves the abnormal growth of new blood vessels from the choroid layer of the eye through Bruch's membrane. This can cause vision loss and is a common cause of wet macular degeneration. CNV occurs due to alterations in Bruch's membrane and high levels of vascular endothelial growth factor. It is classified based on its location relative to the retinal pigment epithelium and fovea. Symptoms include sudden vision loss and visual distortions. CNV is diagnosed through imaging like optical coherence tomography and fluorescein angiography and treated with injections of anti-VEGF drugs to inhibit blood vessel growth.
The document discusses implantable contact lenses (ICL) for correcting high refractive errors. Key points include:
- ICL is preferred over LASIK for high myopia or thin corneas, as it has fewer risks of complications.
- ICL is made of a biocompatible collamer material and is implanted in the posterior chamber behind the iris.
- A clinical trial found nearly 60% of eyes achieved 20/20 vision and 95% achieved 20/40 vision or better after 3 years with ICL implantation.
- Complications are generally low but can include cataracts, increased eye pressure, damage to the natural lens, and other rare issues like infections. Most risks are
Keratoconus is a non-inflammatory, progressive thinning and protrusion of the cornea that results in irregular astigmatism and decreased vision. It typically presents after puberty with no gender or racial predilection. Diagnosis is made based on corneal thinning, Fleischer ring, Vogt's striae, and irregular astigmatism seen on keratometry and topography. Mild cases are managed with spectacles while more severe cases require rigid gas permeable contact lenses, Intacs, or corneal transplantation.
The Scheimpflug principle allows for imaging of the anterior eye segment with maximal depth of focus. Scheimpflug systems like the Pentacam and Orbscan use this principle to provide detailed tomography and topography maps of the cornea and anterior chamber. The Pentacam uses a rotating Scheimpflug camera combined with a static camera to construct a 3D model from 25,000 data points. It analyzes parameters like corneal thickness, curvature, astigmatism, and anterior chamber dimensions. The Orbscan uses slit scanning to create elevation maps of the anterior and posterior corneal surfaces and measure pachymetry. Both devices help evaluate conditions like keratoconus and guide refractive surgery planning.
This document describes different types of artificial anterior chambers used in corneal transplantation surgeries. It discusses reusable chambers like the Moria AAC and disposable chambers like the Barron Disposable AAC. The Moria ALTK system allows adjustment of the diameter of the donor corneal resection, while the Barron AAC maintains pressure on the donor cornea during lamellar dissection or trephination. Both systems involve placing the donor cornea on the chamber, adjusting intrachamber pressure, and then performing the corneal resection.
Specular microscopy is used to examine the corneal endothelium and analyze pathological changes. There are contact and non-contact types, with contact providing higher resolution but potential discomfort. The procedure involves placing the patient comfortably and using fixation to keep the eye still while obtaining images. Images are then analyzed to study normal endothelium morphology, diagnose corneal endothelial diseases, and monitor conditions like aging, diabetes, surgery, trauma, and compare surgical techniques. Specular microscopy can detect disorders like Fuchs' endothelial dystrophy and help with decisions like eye banking and surgery.
This document summarizes different types of corneal refractive surgery procedures. It describes the anatomy and physiology of the cornea, including its layers and shape. It then discusses various laser eye surgery procedures like LASIK, PRK, LASEK, Epi-LASIK, and intrastromal corneal ring implants. For each procedure, it provides a brief overview and lists the advantages and disadvantages. The goal of these surgeries is to correct refractive errors like myopia, hyperopia, and astigmatism by reshaping the cornea through ablation or incisions.
Current Trends in Refractive Surgery - Lecture given at Harvard by Emil Chynn...parkavenuelasek
Dr. Chynn graduated from Harvard's ophthalmology program, which is probably the most famous in the world.
As the only member of his graduating class to specialize in Refractive Surgery, and now an recognized authority, Dr. Chynn is frequently invited back to Harvard to give updates on the State of the Art in Refractive Surgery.
This slide show presentation was given to 100 eye surgeons who flew in from across the country to learn the latest advances in glaucoma, retina, cataract surgery--and laser vision correction (from Dr. Chynn).
The title of his talk reflects the movement in the US and worldwide from leading surgeons that is called "Back to the Surface." This means that surgeons are moving away from LASIK and IntraLase, to avoid flap complications and the # 1 problem causing lawsuits (iatrogenic keratoconus, or KC), and back to the surface.
For some doctors, this means going back to the original procedure, PRK, which has a lot of pain, delayed healing, and scarring.
For Dr. Chynn, this means performing an Advanced Surface Ablation, which is either a LASEK or epiLASEK. These are more advanced than PRK because they do not hurt, healing and recovery is quick, and there is no haze or scarring.
For example, Dr. Chynn performs over 1,000 LASEKs and epiLASEKs per year--he performed his last PRK in 1999.
Obviously, he moved away from PRK to LASIK, then to IntraLase, and now back to the safer LASEK and epiLASEK procedures.
View the following slide show to find out more, and call us with your questions--better yet, come in and meet with our MDs!
The document provides an introduction to refractive surgery, describing different types of refractive errors and methods used to correct them. It discusses procedures like LASIK, PRK, and lens implants. LASIK involves creating a corneal flap then sculpting the cornea with an excimer laser. PRK removes the outer corneal layer then applies the laser. Lens implants are for higher refractive errors or when other methods don't work. The risks, recovery times, and potential outcomes are outlined for each procedure.
This document provides information on various refractive surgery techniques and technologies, including LASIK, PRK, and SMILE. It discusses the goals of refractive surgery in reducing dependence on glasses or contacts and the importance of patient evaluation to determine the best technique. It also covers topics like the eye's refractive power, different refractive errors, the LASIK procedure steps, pre-operative testing including topography and pachymetry, risk factors, and the evolution of excimer laser technologies.
Penetrating keratoplasty by pushkar dhirPushkar Dhir
This document provides information about keratoplasty procedures. It begins with definitions of keratoplasty and different types including penetrating keratoplasty and lamellar keratoplasty. Common indications for keratoplasty are then outlined for optical, tectonic/reconstructive, therapeutic, and cosmetic purposes. Details are provided about donor tissue selection, storage, and contraindications. The preoperative evaluation of recipients is described. Finally, the key steps of the penetrating keratoplasty procedure are summarized, including trephination of the donor and recipient corneas and suturing techniques. Postoperative treatment and potential complications are also mentioned.
Available options for keratoconus managementAmr Mounir
This document discusses various treatment options for managing keratoconus, including glasses, hard contact lenses, corneal collagen cross-linking (CXL), intracorneal ring segments, and keratoplasty. It provides details on the types of intracorneal rings (e.g. kerarings and myoring) and guidelines for when each treatment option is most appropriate based on the severity and progression of the condition, the patient's age, and corneal parameters. Key points emphasized are that keratoconus is a progressive disease, treatment requires customization for each patient, and the goal is to delay or avoid keratoplasty through stabilization and regularization of the cornea.
Describes the procedure of ReLEx smile, and illustrates why it is likely to replace excimer laser LASIK over time. For more details, visit www.newvisionindia.com
This document summarizes various corneal surgery procedures:
1. Penetrating keratoplasty is used to treat optical, tectonic, therapeutic, or cosmetic corneal issues and involves excision of the host corneal tissue and fixation of donor tissue.
2. Keratoprosthesis involves insertion of an artificial lenticule into the corneal stroma for patients with bilateral blindness from conditions like ocular pemphigoid.
3. Refractive surgeries like radial keratotomy, photorefractive keratectomy, laser in-situ keratomileusis, and non-contact laser thermal keratoplasty are used to treat refractive errors by reshaping the cornea using techniques like exc
This document discusses different types of keratoplasty procedures including penetrating keratoplasty, lamellar keratoplasty, and Descemet stripping endothelial keratoplasty. Penetrating keratoplasty involves replacing the entire diseased cornea and is used for conditions involving all corneal layers. Lamellar keratoplasty replaces only partial layers of the cornea. Deep anterior lamellar keratoplasty removes tissue to the level of Descemet's membrane while Descemet stripping endothelial keratoplasty only replaces the diseased endothelium and Descemet's membrane through a small incision.
This document summarizes refractive eye surgery procedures and techniques. It discusses different types of refractive errors like myopia, hyperopia, and astigmatism. It describes procedures like LASIK, PRK, lens extraction, and implantable lenses. It highlights developments in customized laser treatments using wavefront technology and multifocal intraocular lenses. The document aims to help general practitioners better understand the scope of refractive eye surgery options and ongoing advances in the field.
The document discusses corneal refractive surgery using femtosecond lasers. It begins by describing common vision problems like myopia, hyperopia, and astigmatism. It then discusses the history and development of refractive eye surgery using excimer lasers. Different types of laser eye surgery procedures are described such as LASIK, LASEK, PRK. The document outlines the procedure for femtosecond laser surgery, the interaction of femtosecond laser pulses with corneal tissue, and examples of refractive corrections that can be achieved. It concludes by discussing the advantages of laser eye surgery over non-laser surgeries and potential risks.
The document provides an introduction to refractive surgery. It discusses different vision conditions like myopia, hyperopia and presbyopia. It explains how these conditions can be corrected through glasses, contact lenses or refractive surgery options like LASIK and PRK. It addresses common myths about refractive surgery, discussing the safety, effectiveness and long-term outcomes of these procedures.
The document summarizes key aspects of contact lens fitting and evaluation. It discusses the anatomy relevant to contact lenses including the tear film and cornea. It then covers common contact lens materials and parameters like oxygen permeability. The document outlines a typical contact lens examination including case history, fitting evaluation, and patient education on proper lens care.
Laser Vision Clinic Central Coast results for 2013 and Presbyopia management ...presmedaustralia
This document contains data from a study analyzing outcomes of laser vision correction surgery. It includes:
- Demographic data on 227 eyes that underwent surgery
- Pre-operative and 1-month post-operative refractive data
- Visual acuity outcomes showing high percentages of eyes achieving 6/6 or better vision
- Comparisons to outcomes from a large study in Singapore showing results are on par or better
- A trial using software to induce spherical aberration to increase depth of field for presbyopia treatment
- Questions about optical characteristics of the cornea and strategies for presbyopia treatment
This document discusses corneal surgery, including corneal refractive surgery and corneal transplant surgery. It describes the different types of corneal refractive surgery, which include flap surgery techniques like LASIK and surface procedures like PRK. Corneal transplant surgery, also called keratoplasty, is described as replacing damaged corneal tissue with healthy donor tissue. The common techniques used are penetrating keratoplasty and lamellar keratoplasty. The document outlines the donor corneal preparation and storage methods, as well as the surgical techniques and potential complications of corneal transplant surgery.
Corneal topography and wavefront analysis are imaging tools used to evaluate the cornea and refractive errors. Corneal topography measures the shape and curvature of the corneal surface using reflected placido rings, while wavefront analysis captures aberrations of the entire optical system using a Hartmann-Shack device. Both tools are useful for screening refractive surgery candidates and managing conditions like astigmatism and ectasia. Key information provided includes corneal curvature maps, aberration measurements via Zernike polynomials, and detection of irregularities like keratoconus.
LASIK or Lasik (laser-assisted in situ keratomileusis), commonly referred to as laser eye surgery or laser vision correction, is a type of refractive surgery for the correction of myopia, hyperopia, and an actual cure for astigmatism, since it is in the cornea. LASIK surgery is performed by an ophthalmologist who uses a laser or microkeratome to reshape the eye's cornea in order to improve visual acuity. For most people, LASIK provides a long-lasting alternative to eyeglasses or contact lenses.
The planning and analysis of corneal reshaping techniques such as LASIK have been standardized by the American National Standards Institute, an approach based on the Alpins method of astigmatism analysis. The FDA website on LASIK states,
"Before undergoing a refractive procedure, you should carefully weigh the risks and benefits based on your own personal value system, and try to avoid being influenced by friends that have had the procedure or doctors encouraging you to do so."
The procedure involves creating a thin flap on the eye, folding it to enable remodeling of the tissue beneath with a laser and repositioning the flap.
This document provides an overview of the anatomy of the cornea. It begins with definitions and then discusses the embryology, gross anatomy, histological structures, blood and nerve supply of the cornea. The histological structures section describes the layers of the cornea in detail, including the epithelium, Bowman's layer, stroma, Dua's layer, Descemet's membrane, and endothelium. It highlights the composition, structure, and clinical significance of each layer. The document emphasizes the parallel arrangement of collagen fibrils in the stroma, which allows for easy dissection during corneal transplant surgeries.
This document discusses various refractive surgery procedures used to correct refractive errors of the eye, including incisional keratotomy techniques, lamellar procedures, laser ablation procedures, corneal implants, and lens-based procedures. It provides details on common procedures like radial keratotomy, LASIK, PRK, and LASEK. It covers patient evaluation, surgical techniques, potential complications, and advantages of different approaches. Wavefront-guided customized excimer laser surgery is also introduced to correct higher-order aberrations in addition to spherical and cylindrical errors.
This document discusses contact lens fitting following various refractive surgeries. It begins with an introduction to refractive surgeries like radial keratotomy, PRK, LASIK, LASEK, SMILE, and others. It then discusses considerations and techniques for fitting contact lenses after different surgeries, focusing on fitting rigid gas permeable lenses, mini-scleral lenses, and hybrid lenses following procedures like radial keratotomy that can result in irregular astigmatism. The document provides guidance on lens parameters and fitting criteria to achieve a stable, comfortable fit while maintaining corneal health after refractive surgery.
Lamellar Keratoplasty in ophthalmologypratik mohod
Lamellar keratoplasty involves replacing only the diseased portion of the cornea, leaving the recipient's posterior stroma, Descemet's membrane, and endothelium intact. It is less invasive than penetrating keratoplasty. Deep lamellar endothelial keratoplasty (DLEK) and Descemet's stripping automated endothelial keratoplasty (DSAEK) specifically replace only the recipient's diseased endothelium with donor tissue. DLEK is performed through a large limbal incision while DSAEK strips off the recipient's Descemet's membrane through a small incision. Both techniques aim to provide faster visual recovery and avoid complications compared to penetrating keratoplasty.
This document summarizes corneal and refractive surgery procedures presented by various speakers. It discusses keratoplasty techniques like penetrating keratoplasty and lamellar keratoplasty. It also covers endothelial keratoplasty, limbal stem cell grafting, keratoprostheses, and refractive procedures like LASIK to correct refractive errors. Post-operative complications of various procedures and their management are also summarized.
Pachymetry is the measurement of corneal thickness. The central corneal thickness in normal eyes ranges from 0.49 to 0.56 mm. Thicker corneas can indicate endothelial decompensation. Several techniques are used to measure corneal thickness including ultrasonic pachymetry, specular microscopy, optical coherence tomography, and confocal microscopy. Measurement of corneal thickness is important for diagnosing and managing conditions like glaucoma, refractive surgery, and contact lens wear.
This document discusses the corneal endothelium and techniques for assessing its health and function. The corneal endothelium is a single layer of hexagonal cells that maintains corneal clarity by pumping fluid out of the stroma. Assessment techniques described include specular microscopy, which examines cell density, morphology, and patterns at high magnification; confocal microscopy and anterior segment OCT for in vivo imaging; and ultrasound pachymetry to measure corneal thickness as an indicator of endothelial function. Common endothelial diseases like Fuchs' dystrophy and conditions affecting assessment are also reviewed.
This document discusses the corneal endothelium and techniques for assessing its health and function. The corneal endothelium is a single layer of hexagonal cells that maintains corneal clarity by pumping fluid out of the stroma. Assessment techniques described include specular microscopy, which examines cell density, morphology, and patterns at high magnification; confocal microscopy and anterior segment OCT for in vivo imaging; and ultrasound pachymetry to measure corneal thickness as an indicator of endothelial function. Common endothelial diseases like Fuchs' dystrophy and conditions affecting assessment are also reviewed.
This document provides an overview of the pre-operative assessment for corneal laser procedures. It discusses evaluating patients for their suitability, including determining their refractive error and assessing their ocular health. Key parts of the examination are outlined, such as measuring vision, refraction, corneal thickness and topography. Contraindications like keratoconus or thin corneas are mentioned. The document emphasizes properly assessing risk factors to avoid complications like ectasia. A variety of imaging technologies are also described that can help evaluate the cornea and lens.
Refractive surgeries aim to correct refractive errors like myopia, hyperopia and astigmatism by altering the cornea or lens. Techniques include excimer laser ablation under a corneal flap (LASIK), surface ablation procedures like PRK, and newer procedures like ReLEx. Excimer and femtosecond lasers are commonly used to precisely reshape the cornea. Selection criteria consider factors like corneal thickness and pupillary size to minimize risks. Post-operative care and monitoring is important for stabilization and recovery.
This document discusses various corneal ectasias such as keratoconus. It describes the structure of the cornea and the pathophysiology of keratoconus. Symptoms include decreasing vision, irregular astigmatism. Diagnosis involves corneal tomography and biomechanical testing. Management includes contact lenses, corneal collagen cross-linking, and intrastromal corneal ring segments. The Dresden protocol is described for corneal collagen cross-linking using riboflavin and UV light.
This document provides information on penetrating keratoplasty (PKP), which involves replacing the full thickness of diseased corneal tissue with donor corneal tissue. It discusses the types of PKP including optical, therapeutic, and tectonic. The common indications for PKP include corneal scarring, infections, dystrophies, and thinning. Preoperative evaluation and obtaining a suitable donor corneal tissue is important. The surgical procedure involves trephination of the donor and host corneas followed by suturing the donor graft. Postoperative complications can include rejection, infections, glaucoma and astigmatism. Long term graft survival depends on the preoperative diagnosis and condition.
This document compares and contrasts AS-OCT (anterior segment optical coherence tomography) and ultrasound biomicroscopy (UBM) imaging techniques for evaluating the anterior eye segment.
It discusses that AS-OCT provides non-contact, high resolution cross-sectional imaging of the anterior segment structures without touching the eye. UBM uses high frequency ultrasound to generate detailed 2D images of the anterior segment, allowing visualization of structures like the iris and angle.
While both techniques allow qualitative and quantitative assessment of the anterior chamber angle and structures, AS-OCT has advantages of being non-contact, faster imaging, and less operator dependency compared to UBM. However, UBM can image deeper into the posterior iris and has greater penetration than
This document discusses various corneal laser surgeries and procedures. It describes corneal cross-linking, which uses UV light and riboflavin to increase corneal stiffness and halt keratoconus progression. It is less invasive than corneal transplantation. Intrastromal corneal rings are also discussed, which are implanted in the corneal stroma to decrease steepening and astigmatism in keratoconus. Refractive surgeries like PRK, LASIK, and SMILE are outlined that use lasers to reshape the cornea. Preoperative evaluation, cryotherapy, and potential complications of procedures are summarized as well.
This document provides an overview of keratoconus, including its etiology, signs and symptoms, classification, and management. Keratoconus is a non-inflammatory thinning of the cornea that results in a cone-shaped protrusion and irregular astigmatism. It typically onset in teenagers and progresses over time. Management includes rigid gas permeable contact lenses, collagen cross-linking to halt progression, and keratoplasty for advanced cases.
OCT provides high resolution cross-sectional images of the retina. It works by comparing the echo time delay of light reflected from retinal structures to a reference mirror. There are different OCT protocols that image the retina in various ways. When reading an OCT scan, clinicians examine the layer structure, reflectivity, and thickness to identify normal features and pathologies. Common retinal conditions like diabetic macular edema, retinal vein occlusions, and age-related macular degeneration have characteristic OCT findings that aid in diagnosis and monitoring treatment.
The anterior chamber angle structures and aqueous outflow system were summarized. The anterior chamber is bounded anteriorly by the cornea and posteriorly by the iris and lens. It contains aqueous humor and drains through the trabecular meshwork into Schlemm's canal and collector channels. Key angle structures include Schwalbe's line, trabecular meshwork, scleral spur, and ciliary body. Gonioscopy allows visualization and grading of the anterior chamber angle and is important for glaucoma evaluation and treatment planning.
The cornea has five layers - epithelium, Bowman's layer, stroma, Descemet's membrane, and endothelium. It is avascular and transparent. The epithelium regenerates every 7 days. The endothelium maintains dehydration via ion pumps. Diseases like keratoconus cause thinning. Examination uses a slit lamp to assess size, shape, surface, transparency, and vascularization. Stains like fluorescein detect erosions while rose bengal finds filaments. The cornea has high innervation and refractive power of 45 diopters.
UBM provides high resolution imaging of the anterior segment structures in a non-invasive manner. It can image structures like the ciliary body and zonules that
Promoting Wellbeing - Applied Social Psychology - Psychology SuperNotesPsychoTech Services
A proprietary approach developed by bringing together the best of learning theories from Psychology, design principles from the world of visualization, and pedagogical methods from over a decade of training experience, that enables you to: Learn better, faster!
Basavarajeeyam is an important text for ayurvedic physician belonging to andhra pradehs. It is a popular compendium in various parts of our country as well as in andhra pradesh. The content of the text was presented in sanskrit and telugu language (Bilingual). One of the most famous book in ayurvedic pharmaceutics and therapeutics. This book contains 25 chapters called as prakaranas. Many rasaoushadis were explained, pioneer of dhatu druti, nadi pareeksha, mutra pareeksha etc. Belongs to the period of 15-16 century. New diseases like upadamsha, phiranga rogas are explained.
ABDOMINAL TRAUMA in pediatrics part one.drhasanrajab
Abdominal trauma in pediatrics refers to injuries or damage to the abdominal organs in children. It can occur due to various causes such as falls, motor vehicle accidents, sports-related injuries, and physical abuse. Children are more vulnerable to abdominal trauma due to their unique anatomical and physiological characteristics. Signs and symptoms include abdominal pain, tenderness, distension, vomiting, and signs of shock. Diagnosis involves physical examination, imaging studies, and laboratory tests. Management depends on the severity and may involve conservative treatment or surgical intervention. Prevention is crucial in reducing the incidence of abdominal trauma in children.
8 Surprising Reasons To Meditate 40 Minutes A Day That Can Change Your Life.pptxHolistified Wellness
We’re talking about Vedic Meditation, a form of meditation that has been around for at least 5,000 years. Back then, the people who lived in the Indus Valley, now known as India and Pakistan, practised meditation as a fundamental part of daily life. This knowledge that has given us yoga and Ayurveda, was known as Veda, hence the name Vedic. And though there are some written records, the practice has been passed down verbally from generation to generation.
Recomendações da OMS sobre cuidados maternos e neonatais para uma experiência pós-natal positiva.
Em consonância com os ODS – Objetivos do Desenvolvimento Sustentável e a Estratégia Global para a Saúde das Mulheres, Crianças e Adolescentes, e aplicando uma abordagem baseada nos direitos humanos, os esforços de cuidados pós-natais devem expandir-se para além da cobertura e da simples sobrevivência, de modo a incluir cuidados de qualidade.
Estas diretrizes visam melhorar a qualidade dos cuidados pós-natais essenciais e de rotina prestados às mulheres e aos recém-nascidos, com o objetivo final de melhorar a saúde e o bem-estar materno e neonatal.
Uma “experiência pós-natal positiva” é um resultado importante para todas as mulheres que dão à luz e para os seus recém-nascidos, estabelecendo as bases para a melhoria da saúde e do bem-estar a curto e longo prazo. Uma experiência pós-natal positiva é definida como aquela em que as mulheres, pessoas que gestam, os recém-nascidos, os casais, os pais, os cuidadores e as famílias recebem informação consistente, garantia e apoio de profissionais de saúde motivados; e onde um sistema de saúde flexível e com recursos reconheça as necessidades das mulheres e dos bebês e respeite o seu contexto cultural.
Estas diretrizes consolidadas apresentam algumas recomendações novas e já bem fundamentadas sobre cuidados pós-natais de rotina para mulheres e neonatos que recebem cuidados no pós-parto em unidades de saúde ou na comunidade, independentemente dos recursos disponíveis.
É fornecido um conjunto abrangente de recomendações para cuidados durante o período puerperal, com ênfase nos cuidados essenciais que todas as mulheres e recém-nascidos devem receber, e com a devida atenção à qualidade dos cuidados; isto é, a entrega e a experiência do cuidado recebido. Estas diretrizes atualizam e ampliam as recomendações da OMS de 2014 sobre cuidados pós-natais da mãe e do recém-nascido e complementam as atuais diretrizes da OMS sobre a gestão de complicações pós-natais.
O estabelecimento da amamentação e o manejo das principais intercorrências é contemplada.
Recomendamos muito.
Vamos discutir essas recomendações no nosso curso de pós-graduação em Aleitamento no Instituto Ciclos.
Esta publicação só está disponível em inglês até o momento.
Prof. Marcus Renato de Carvalho
www.agostodourado.com
Does Over-Masturbation Contribute to Chronic Prostatitis.pptxwalterHu5
In some case, your chronic prostatitis may be related to over-masturbation. Generally, natural medicine Diuretic and Anti-inflammatory Pill can help mee get a cure.
Osteoporosis - Definition , Evaluation and Management .pdfJim Jacob Roy
Osteoporosis is an increasing cause of morbidity among the elderly.
In this document , a brief outline of osteoporosis is given , including the risk factors of osteoporosis fractures , the indications for testing bone mineral density and the management of osteoporosis
These lecture slides, by Dr Sidra Arshad, offer a quick overview of the physiological basis of a normal electrocardiogram.
Learning objectives:
1. Define an electrocardiogram (ECG) and electrocardiography
2. Describe how dipoles generated by the heart produce the waveforms of the ECG
3. Describe the components of a normal electrocardiogram of a typical bipolar lead (limb II)
4. Differentiate between intervals and segments
5. Enlist some common indications for obtaining an ECG
6. Describe the flow of current around the heart during the cardiac cycle
7. Discuss the placement and polarity of the leads of electrocardiograph
8. Describe the normal electrocardiograms recorded from the limb leads and explain the physiological basis of the different records that are obtained
9. Define mean electrical vector (axis) of the heart and give the normal range
10. Define the mean QRS vector
11. Describe the axes of leads (hexagonal reference system)
12. Comprehend the vectorial analysis of the normal ECG
13. Determine the mean electrical axis of the ventricular QRS and appreciate the mean axis deviation
14. Explain the concepts of current of injury, J point, and their significance
Study Resources:
1. Chapter 11, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 9, Human Physiology - From Cells to Systems, Lauralee Sherwood, 9th edition
3. Chapter 29, Ganong’s Review of Medical Physiology, 26th edition
4. Electrocardiogram, StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK549803/
5. ECG in Medical Practice by ABM Abdullah, 4th edition
6. Chapter 3, Cardiology Explained, https://www.ncbi.nlm.nih.gov/books/NBK2214/
7. ECG Basics, http://www.nataliescasebook.com/tag/e-c-g-basics
Local Advanced Lung Cancer: Artificial Intelligence, Synergetics, Complex Sys...Oleg Kshivets
Overall life span (LS) was 1671.7±1721.6 days and cumulative 5YS reached 62.4%, 10 years – 50.4%, 20 years – 44.6%. 94 LCP lived more than 5 years without cancer (LS=2958.6±1723.6 days), 22 – more than 10 years (LS=5571±1841.8 days). 67 LCP died because of LC (LS=471.9±344 days). AT significantly improved 5YS (68% vs. 53.7%) (P=0.028 by log-rank test). Cox modeling displayed that 5YS of LCP significantly depended on: N0-N12, T3-4, blood cell circuit, cell ratio factors (ratio between cancer cells-CC and blood cells subpopulations), LC cell dynamics, recalcification time, heparin tolerance, prothrombin index, protein, AT, procedure type (P=0.000-0.031). Neural networks, genetic algorithm selection and bootstrap simulation revealed relationships between 5YS and N0-12 (rank=1), thrombocytes/CC (rank=2), segmented neutrophils/CC (3), eosinophils/CC (4), erythrocytes/CC (5), healthy cells/CC (6), lymphocytes/CC (7), stick neutrophils/CC (8), leucocytes/CC (9), monocytes/CC (10). Correct prediction of 5YS was 100% by neural networks computing (error=0.000; area under ROC curve=1.0).
2. APPLIED ANATOMY OF CORNEA
• EPITEHLIUM: composed of non keratinized
startified squamous epithelium of 4 to 6 layers
thickness. BM (lamina densa & lamina lucida), wing
cells and flattened top cells having microvilli.
• BOWMAN’S LAYER: condensed superficial layer of
the stroma, consists of randomly dispersed collagen
fibrils.
• STROMA: 500m thick consists of collagen producing
fibroblasts keratocytes , matrix & collagen lamellae.
3. APPLIED ANATOMY OF CORNEA
• DESCEMETS MEMBRANE: strong well defined
sheet in between stroma & endothelium.
• ENDOTHELIUM: plays an major role in active
transport & maintenance of normal stroma.
4. HISTORY
• In 1978 bore,myers & cowden were first in
USA to perform radial keratotomy & report
there results.
• Lamellar surgery were evolving
simultaneously, Jose Barraquer was the first
to correct refractive error through lamellar
surgery.
5. CLASSIFICATION OF
KERATOREFRACTIVE Sx
LOCATION ADDITION SUBTRACTION RELAXATION COMPRESSION
SUPERFICIAL EPIKERATOPHA
KIA
1.PRK
2. LASEK
---------- CORNEAL
MOLDING
INTRASTOMAL 1.KERATOPHAK
IA
2.INTRACORNE
AL LENSES
3.PINHOLE
APERTURES
1.LASIK LAMELLAR
KERATOPLASTY
PERIPHERAL INTRACORNEAL
STROMAL RING
WEDGE
RESECTION
RADIAL
KERATOTOMY.
1.THERMOKER
ATOPLASTY.
2.COMPRESSIO
N SUTURES
9. Clinical significance of cornealClinical significance of corneal
topographytopography
• Indispensable tool for refractive
surgeons
– Preoperative screening
– Surgical planning
– Assessment of surgical outcomes
– Detection and management of complications
– Refinement and development of surgical
techniques
10. Principles of Corneal TopographyPrinciples of Corneal Topography
• Placido disc system
• Non-Placido disc system
–Scanning slit
–Rasterstereography
–Laser Holographic interferometry
11. FIGURE 2-17 BASIC CHARACTERISTICS OF AN AXIAL MAP
Simulated
keratometer
and astigma-
tism indicator
Statistical
index
indicators
Pupil size
indicator
Dioptric power
and radius
indicators
Vertex and
pupil distance
and location
indicators
1mm x 1mm
grid indicators
Center of map
(vertex) and
center of pupil
markers
Pupil marker
12.
13. KeratometryKeratometry
• Advantages
• Accessibility
• Ease of use
• Precision is good
• Low cost
• Adequate for most contact lens fitting
• Limitations
• Small area measured: periphery and apex not measured.
• Assumes that the cornea is a spherical surface: accuracy is
questionable
• Irregular topography not described specifically and sometimes
undetected
14. WAVEFRONT
• Discovered nearly 400 years ago by
christopher scheiner.
• He demonstrated a technique to measure the
refractive error of the eye using a device
known as Scheiner disc.
• Visual acuity measuring device takes into
consideration tear film, anterior corneal
surface, corneal stroma, posterior corneal
surface, anterior crystalline lens
15. • posterior crystalline lens surface, vitreous and
retina.
• Prior to the advent of wavefront-sensing
devices, clinical refraction consisted of three
data points for each eye: defocus (spherical
error, myopia, or hyperopia), astigmatism,
and axis.
16. Wavefront Technology
Diagnostic devices :
1. higher-order aberrations :
field curvature, distortion, diffraction,
spherical aberration, chromatic aberration,
coma
2.refraction vs. wavefront refraction (refractive
map)
cf. keratometry vs. topographic map
Wavefront-guided refractive surgery
17. Types of aberrometer
• Hartmann shack system outgoing reflection
aberrometry)
• Tscherring system
• Ray tracing system.
• Ingoing adjustable refractometry.
• Double pass aberrometry.
18. Note the loss of dots centrally in a “moth-eaten” appearance and the overall
irregularity
of horizontal and vertical alignment of the spots of this eye with significant aberration.
19. EPIKERATOPHAKIA
• Is an form of refractive surgery on the cornea for the
correction of keratoconus, aphakia & high myopes.
• Gasset and kauffman in 1968 tried with plastic lens,
glued over the cornea. Unfortunately glue made the
corneaq opaque.
• Werblin and kauffman later devised using lathe cut
donor corneal lenticule mainly in peadiatric aphakic
patients.
• With planopower lenticule was developed to treat
keratoconus like onlay lammellar keratoplasty.
20. EPIKERATOPHAKIA
• Corenal epithelium is thoroughly denuded by
rubbing with cellulose sponge.
• 7mm to 7.5mm trephine is used to incise the
patient’s cornea partially to the depth of 0.2
to 0.3mm.
• Rehydrated epikeartophakia lenticule is
sutured into the host cornea.
*
21. ALLOPLASTIC REFRACTIVE
KERATOPLASTY
• This technique involves intrastromal implantation of
hydrogel materials with specific curvature.
• Alloplastic material like polysulphone is placed
between epikeratophakia graft & BM alters the
refractive power by changing the refractive index of
stroma.
• Shape of lenticule is concave or convex depends on
refractive status of eye ie: myope/ hypermetrope
22. KERATOPHAKIA
Lenticule with predetermined power is made
from the donor cornea.
This lenticule is placed over the host prepared stroma
with convex surface anteriorly.
The previously removed stromal disk is sutured over
the lenticule.
Corneal decompensation may lead to postop
opacification, perforation & flattening of Ac may
occur. PK may require for the complication.
23.
24. EXCIMER
• Trokel, srinivasan & barren first suggested the
use of excimer for corneal surgery.
• Excimer derived from term excited dimer of
inert gases.
Leads to emission of high energy photon of UV
light having 6.4eV.
various excimer lasers are: argon fluoride
193nm,kypt cl 222nm, kypt fl 249, xenon cl
308, xenon fl 351.
25. Corneal tissue interaction
• Carbon- nitrogen bonds which forms the
peptide in proteins is broken by the highly
excited state of an inertgases.
• The photon induced molecular decomposition
results in abalative photo decomposition.
• The above mentioned process if precisely
controlled, restricted, gives optically smooth,
with minimal scarring with appro depth
abalation.
27. PREOPERATIVE EVALUATION
• Visual acuity with cycloplegic refraction
• Complete ophthalmic & medical history.
• Keratometry / topography / pachymetry
• Pupil size and diameter in dim light.
• Applation tonometry
• Test for dry eye & lacrimal examination
28. PRK
• Laser caliberation & prechecks
• Ppd & topical anesthesia
• Determination of optical centre.
• Removal of epithelium
• Stromal ablation
• Postop medication
• Placement of soft contact lens
• ***
29. COMPLICATIONS
• Intra OP: Error in laser programming.
Incompelete epithelial removal
Decentered ablation.
Post OP :
Early
Delayed wound
healing
Infection
NSAIDS infiltrates
AB precipitates
CORNEAL melts
INTERMED 2wk-6 mnth
Over/under corr
Regression
Streep corneal islands
Scars
Steriod induced
complicationss
LATE >6 months
Steriods induced
Scars
Halos/ glares
Visual fluctuations
Corneal haze
30. LASEK
• Laser subepithelial keratomileusis (LASEK) is a
relatively new refractive surgical technique that
purportedly combines the advantages of laser in-situ
keratomileusis (LASIK) and photorefractive
keratectomy (PRK).
• In 1996, Azar [8•] performed the first LASEK
procedure, which he called “alcohol-assisted flap
PRK.” Later it was renamed LASEK by Camellin, who
popularized his own version
31. LASEK
• LASEK is in essence a hybrid of PRK and LASIK that
may provide relatively quick visual recovery, while
eliminating virtually all flap-related complications.
• The LASEK procedure is based on chemically reducing
the corneal epithelial adhesion to the underlying
Bowman’s layer by the application of dilute ethanol.
• 8.0-mm diameter circular marker with an 80μm deep
cutting edge, designed to create a 270° superficial
punch cut in the epithelium.
32. LASEK
• The denuded corneal surface is then ablated with the
excimer laser as in standard PRK.
• flap is gently repositioned over the central cornea
with a blunt instrument, such as a Barraquer iris
sweep.
• A therapeutic soft contact lens is placed onto the
cornea.
33. LASIK
• Initially described by Pallikaris in1990.
• Preoperative consideration;
Patient selection.
Stability of refraction.
Fundus
Corneal thickness/ conus
Patients anxiety/ sedation.
34. LASIK procedure
• Anesthesia : topical with 1% proparacaine or
4% xylocaine.
• Corneal marking: ensure proper realignment.
• Suction ring: placed on the eye & centerd over
the limbus. IOP rises over 60mm hg.
• Microkeratome: when adequate pressure is
obtained surface is lubricated with anesthesia
not saline.
35. Microkeratome is slide over surface to raise the
epithelial flap.
• Excimer laser reshapes the cornea by
removing a pre-determined precise amount of
tissue.
• The corneal flap is repositioned iris sweep –
no stitch required.
• Fluence test.
• ***
36. CORNEAL BIOMECHANICS
• Layered corneal is permanently severed following
surgery.
• This reduces the tension in the remaining peripheral
segments allowing expansion of peripheral layers.
• Peripheral expansion results in higher order
aberrations.
• Topography allows to visualise actual change in
shape that occured following the ablation.
• Wavefront helps in to fully characterised shape
changes & resultant functional response.
38. Customized Refractive Surgery
Functional customization based on pt’s need
1. age
2. presbyopia
3. occupational and recreational needs
4. refraction
5. psychological tolerance
39. Customized Refractive Surgery
Anatomical customization
1. corneal diameter and thickness
2. pupil size
3. anterior chamber depth
4. anterior and posterior lens shape
5. axial length
41. Customized refractive surgery
1}SCANNING SPOT: spot size of 1mm or lesser to treat
4th
order aberrations with optical zone diameter of
6mm.
2}SCANNING SPOT SHAPE:
(a) Gaussian beam shape: it allows very smooth
overlape creation of ablation zone.
(b)Top HAT: gives rise to spikes & valleys in the
ablation profile.
3}SCANNING SPOT RATE: small spots utilise 200Hz
energy.
42. 4} SPOT PLACEMENT: spot is best when it is non-
sequential such that one spot is not placed
next to the precedding spot.
EYE TRACKING:
1) SAMPLING RATE.
2)LATENCY.
3) TRACKER TYPE.
4) CLOSE-LOOP VERSUS OPEN LOOP TRACKING.
43. Wavefront-Guided Refractive
Surgery
“ Super Vision ” ( 20 / 10 )
Eliminating surgically induced aberrations is the
first step to super vision.
Seiler T : increase in higher-order aberrations
after standard LASIK : 144 %
after wavefront-guided LASIK :
40 %
Adding wavefront informations is helpful in cases
within 0.25 D of the intended correction.
44.
45. FEMTOSECOND LASER
• The femtosecond laser is a mode-locked, diode
pump,neodynium-glass laser. It operates in the
infrared wavelength range, at 1053 nm. It uses a spot
size of less than 3 μm and produces tissue disruption
(Photodisruption) at a specified and precise level
within the corneal stroma. The laser produces
cavitation bubbles consisting of water and carbon
dioxide which are ultimately absorbed through the
corneal endothelium.
46. FEMTOSECOND LASER
• A unique feature of the femtosecond laser is its
ability to produce tissue disruption at very low
energy settings. This is due to the very short pulse
width, or pulse duration, associated with the laser
(600 to 800 fs), and to the very rapid pulse
repetition, or speed, of the laser (15,000 to 60,000
pulses per second).
47. FEMTOSECOND LASIK
• Femto laser has been devised to raise LASIK
flaps
MECHANICAL FEMTOLASER
Mechanism Cut from side to side with
globe pressure
Creates an interface cut
at predetermined depth
Flap Meniscus flap Planar flaps
Flap thickness Depends on suction ring
thickness,corneal
diameter & curvature
Independent of any such
parameters
Size & shape Makes an D shape flap Well centered flap is
created
Complications Free flap, button hole are
common
Light sensitivity,
photophobia common
but self limiting
48. FEMTOSECOND DISADVANTAGES
• Longer suction time
• More flap manipulation
• Opaque bubble layer may interfere with excimer
ablation
• Bubbles in the anterior chamber may interfere with
tracking and registration
• Increased overall treatment time
49. FEMTOSECOND DISADVANTAGES
• Difficulty lifting flap >6 months
• Increased risk of diffuse lamellar keratitis
• Increased cost
• Need to acquire new skills
• Delayed photosensitivity or good acuity plus
• photosensitivity (GAPP), which may require
• prolonged topical corticosteroid therapy
50. Contraindications of LASIK
• Pre existent anamolies- keratoconus.
• Inappropriate parameters; power/
pachymetry/ pupil size.
• Degenrative eye conditions: lupus/glaucoma/DR/
RA.
• Infections.
• Severe dry eye.
• RD
• Pregnancy/ lactating.
• AGE and change in refraction.
51. COMPLICATIONS OF LASIK
• Overcorrection: Myopic or hyperopic surface
ablation typically undergoes some degree of
regression for at least 3- 6 months.
• Undercorrection: Undercorrection occurs much
more commonly at higher degrees of ametropia
because ofdecreased predictability due to the
greater frequency and severity of regression.
• Central Islands: A central island appears on
computerized corneal topography as an area of
central corneal steepening
52. • Optical Aberrations :Some patients report optical
aberrations after surface ablat ion and LASIK,
including glare, ghost images, and halos
• Decentered Ablation
• Corticosteroid-Induced Complications
• Dry Eye and Corneal Sensation
• Infectious Keratitis
• Persistent Epithelial Defects
• Sterile Infiltrates
54. LASIK
1 Faster visual recovery –
1 day
2 No Post operative pain
3 Good for low and high
myopes
4 Predictable and stable
5 Not good for contact
sports
LASEK/PRK
1 Visual recovery – 1
week
2 Mild to Moderate post
op pain
3 Low myopia, thin
corneas
4 Less predictable,
modulation
5 Contact sports, military
55. EPI-LASIK
• Surface ablation in which a viable epithelial flap is
raised.
• The flap is raised at the level of the LAMINA DENSA,
the whole basement membrane remains attached to
the epithelium, increased survival of basal cells.
• Alcohol assited seperation occurs at the level of
lamina lucida and reduces survival of the epithelial
cells.
• ****
58. INTACSINTACS
• Intacs are small semicircular plastics rings of various
thickness inserted in the corneal stroma.
• They are used for the corrections of 1-3D.
• They work by flatting of central portion of the cornea
there by correcting myopic refractive error.
• They smoothen out corneal irregularities
which improves the quality of visison.
59. CORNEAL COLLAGEN CROSSCORNEAL COLLAGEN CROSS
LINKING with RIBOFLAVINLINKING with RIBOFLAVIN
• C3R is a procedure which uses RIBOFLAVIN as the
photosensitiser with UV rays of 365nm.
• UV light increases the number of collagencross
linking fibres which are the anchors within the
corneal stroma.
• RIBOFLAVIN drops are placed every 2 mins, 30 mins
prior to UV-A radiation.
• After the procedure bandage contact lens is used.
61. Laser thermal keratoplasty
• Thermal tissue necrosis gives rise to enhanced
corneal remodelling, thereby limiting effect &
causing regression.
• Ho: YAG laser uses wavelength of 2.13mm ,pulse
duration of 200-300ms laser is used to create
paracentral corneal coagulation & shrinkage in the
controlled manner
62. • Contact mode : fibr-optic probe to deliver
laser pulses to premarked points on the
cornea.
• NON- Contact mode: A slit lamp delivery
system is used to deliver pulses in an
octagonal pattern on the cornea
simultaneously.
Laser thermal keratoplasty
63. CONDUCTIVE KERATOPLASTYCONDUCTIVE KERATOPLASTY
• Utilises radiofrequency energy placed in the
periphery of the cornea to cause collagen shrinkage
& steepen the central cornea.
• 450 x 90 mm2 dimension tip radiofrequency is
delivered in the cornea causing thermal effect.
• +0.75 – +3.25D correction of cycloplegic refraction
with less then -0.75D of astigmatism.
• Age >40 yrs
64. RADIAL KERATOTOMY
• Radial incisions were made to modify the surface of
the cornea by Sato & his associates in 1894.
• To correct myopia, astigmatism & keratoconus.
• Radial incisions were made from periphery to the
paracentral area .
• However it was associted to many complications like
posterior extension leading to posterior keratotomy,
bullous keratopathy due to several of these
complications this procedure is rarely done now
66. Limbal Relaxing Incisions
• Limbal Relaxing Incisions (LRI) are a refractive
surgical procedure to correct minor astigmatism in
the eye.
• Incisions are made at the opposite edges of
the cornea, following the curve of the iris, causing a
slight flattening in that direction.
• They are simpler and less expensive than laser
surgery such as LASIK or photorefractive
keratectomy.
Today the filed of refractive surgery has evolved to include many modalities for the treatment of different refractive errors.
Motivation: detailed information, procedure xplained to the pt anxiety levels xplained. REFRACTION: stability of the refraction last 1 year is checked, >0.5D change accounts for unpredictable long term result. PUPIL SIZE: PUPIL SIZRE BOTH IN LIGHT & DARK should be measured,pupillometer can be used to measure pupil size, pts with larger pupil should be unstd glare & haloes Corneal thickness: topography to rule out keratoconus, its C/I in LASIK due to central corneal thinning, 250mm be left beneath a lamellar keractectomy in order tp prevent ectasia
Hartmann: small light projected to retina and reflected back and focused by lenselet arrey this recorded by video sensor and compared with theoritical aberration free sysytem.
For myopia conves portion is removed and for correction of hyperopia concave portion is removed
Refraction 0.5 spherical chnage / 0.25 cylindrical change / < 20 degree axis change in one year
The well is filled with 20% ethyl alcohol solution for 30 to 50 seconds. Longer times are recommended for young men, postmenopausal women, and long-time contact lens users, because the epithelial flaps in these groups of patients are generally more difficult to lift. At the end of the allotted time, an absorbent cellulose surgical spear is used to soak up the alcohol in the well.
Sampling rate: Rate refers to how frequently the tracker measures the eye position.varies from 60 Hz to 400 Hz Latency: time required to determined eye’s location, in close loop system such as laser radar based system gives continuous feedback occurs leads to zero latency. Its infrared camera based tracking systems. Tracker type: two types:::: video tracking: infrared light of iris against a dark pupildeviation of the eye is read & corrected. Laser radar: space stabilised image is maintained & eye position calculated continually. OPEN SYSTEM: new image is taken n compared with old image change in location is calculated. CLOSE: cont monitoring using a radar system.
They do not control progression of the keratokonus, just help for the fitting of the lens
Its not approved method still under trial, however riboflavin increases the absorption of the radiation & penetration to the deeper tissues, its increased structural integrity shows sucess in various studies of treating and progressing KCONUS.
Averg corneal penetration is 480-530 mm which is 80-90% of corneal thickness, effect was found to vary directly with the pulse energy & inversely with the distance from the centre of the cornea.
Error of application would be less in non contact mode, refractive stability & reproducibility is greater. Ho: YAG laser & the alignment of the burns, have shown that using more than one ring produces a greater refractive change & that applying the concentric rings. STATS: various studies shown improved vision between with 0.75 to 4.75D preoperatively of spherical, up to 3DS astigmatism less then 1DC.
80% depth of the cornea homogenously thermalenergy is deliveredless then 0.5D of difference in the manifest & cycloplegic refractions can be corrected. C/I: recent chnages in 1 yr, age <21 yr, dry eye, C dystrophies, glaucoma, herpes, keloid, keratoconus, DM, PREGnancy, autoimmue & vascular disorders.