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Keratoconus and management


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Keratoconus and management

  1. 1. Dr. Mohd Najmussadiq Khan
  2. 2. Disease Keratoconus is a degenerative non-inflammatory disease of the cornea where the central or paracentral cornea undergoes progressive thinning and steepening causing irregular astigmatism.Etiology Etiology is unknown. However, it is associated with atopy, Down’s Syndrome, Leber’s congenital amaurosis, and Ehler’s Danlos/connective disorders. The hereditary pattern is neither prominent nor predictable, but positive family histories have been reported. The most common presentation of keratoconus is as a sporadic disorder, in which only a significant minority of patients exhibit a family history with autosomal dominant or recessive transmission The incidence of keratoconus if often reported to be 1 in 2000 people. Dr. Mohd Najmussadiq Khan 11/7/2012 2
  3. 3. Risk Factors Eye rubbing, associated with atopy Sleep apnea Floppy Lid Syndrome Dr. Mohd Najmussadiq Khan 11/7/2012 3
  4. 4.  Based on severity of curvature ◦ Mild : less than 45.00D ◦ Moderate : 45.00 to 52.00D ◦ Advanced : 52.00 to 62.00D ◦ Severe : more than 62.00D Based on shape: ◦ Nipple cones (Small size 5mm ) ◦ Oval cones (larger (5-6mm) ellipsoid) ◦ Globus cones (Largest >6mm ,may involve over 75% of cornea. ) Dr. Mohd Najmussadiq Khan 11/7/2012 4
  5. 5.  Retinitis Pigmentosa Leber’s Congenital Amaurosis Microcornea Aniridia Corneal Degeneration Congenital Cataract Ectopia lentis Lenticonus Macular coloboma Retinal dysplasia Floppy eyelid syndrome Dr. Mohd Najmussadiq Khan 11/7/2012 5
  6. 6. Dr. Mohd Najmussadiq Khan 11/7/2012 6
  7. 7.  Down’s syndrome Ehlers-Danlos syndrome Osteogenesis Imperfecta Mitral valve prolapsed Dr. Mohd Najmussadiq Khan 11/7/2012 7
  8. 8. General Pathology --Keratoconus can show the following pathologic findings Deposition of iron in the basal epithelial cells, forming the Fleischer ring—a pigmented ring that results from the accumulation of ferritin particles in the cytoplasm of epithelial cells and widened intercellular spaces. Breaks in Bowmans membrane, filled with cells, collagen, and PAS-positive material. Dr. Mohd Najmussadiq Khan 11/7/2012 8
  9. 9. Dr. Mohd Najmussadiq Khan 11/7/2012 9
  10. 10.  thinning of stroma and overlying epithelium abnormal keratocyte morphology, and endothelial polymorphism folds or breaks in Descemet’s membrane (Vogts striae) variable amounts of diffuse corneal scarring. Dr. Mohd Najmussadiq Khan 11/7/2012 10
  11. 11. Dr. Mohd Najmussadiq Khan 11/7/2012 11
  12. 12. Dr. Mohd Najmussadiq Khan 11/7/2012 12
  13. 13. Pathophysiology Histopathology studies demonstrate breaks in or complete absence of Bowman’s layer, collagen disorganization, scarring and thinning. The etiology of these changes is not known, though some suspect changes in enzymes that lead to breakdown of collagen in the cornea. While a genetic predisposition to keratoconus is suggested, a specific gene has not been identified. Dr. Mohd Najmussadiq Khan 11/7/2012 13
  14. 14. Biochemical abnormalities:-- Studies in patients with keratoconus have demonstrated an increased activity by proteases that breakdown the collagen cross- linkages in the corneal stroma. There is a simultaneous reduced expression of protease inhibitors. The ratio of keratin sulfate to dermatan sulfate is altered in the stromal matrix when compared to normal corneas. Patients with keratoconus have also shown enzymatic changes in the epithelium with increased expression of lysosomal and proteolytic enzymes. Dr. Mohd Najmussadiq Khan 11/7/2012 14
  15. 15. Primary prevention No preventive strategy has been proven effective to date. Some feel that eye rubbing or pressure (e.g. sleeping with the hand against the eye) can cause and/or lead to progression of keratoconus, so patients should be informed not to rub the eyes. In some patients, avoidance of allergens may help decrease eye irritation and therefore decrease eye rubbing. Dr. Mohd Najmussadiq Khan 11/7/2012 15
  16. 16. Diagnosis Diagnosis can be made by slit-lamp examination and observation of central or inferior corneal thinning. Computerized videokeratography is also useful in detecting early keratoconus and allows following its progression. Ultrasound pachymetry can also be used to measure the thinnest zone on the cornea. New algorithms using computerized videokeratopgraphy have been devised which now allow the detection of subclinical or suspected keratoconus. These devices may allow better screening of patients for prospective refractive surgery. Dr. Mohd Najmussadiq Khan 11/7/2012 16
  17. 17. Dr. Mohd Najmussadiq Khan 11/7/2012 17
  18. 18. Dr. Mohd Najmussadiq Khan 11/7/2012 18
  19. 19. History The majority of cases of keratoconus are bilateral, and often asymmetric. The less affected eye may show a high amount of astigmatism or mild steepening. Onset is typically in early adolescence and progresses into the mid-20’s and 30’s. However, cases may begin much earlier or later in life. There is variable progression for each individual. There is often a history of frequent changes in eye glasses which do not adequately correct vision. Another common progression is from soft contact lenses, to Toric or astigmatism correcting contact lens, to rigid gas permeable contact lenes. Dr. Mohd Najmussadiq Khan 11/7/2012 19
  20. 20. Dr. Mohd Najmussadiq Khan 11/7/2012 20
  21. 21. Physical examination A thorough and complete eye exam should be performed on any patient suspected of having keratoconus. The general health of the eye should be assessed and appropriate ancillary tests should be done to assess corneal curvature, astigmatism and thickness. The best potential vision should also be evaluated. Many of the potential exam components are listed below: Proper history, including change in eye glass prescription, decreased vision, history of eye rubbing, medical problems, allergies, sleep patterns Dr. Mohd Najmussadiq Khan 11/7/2012 21
  22. 22.  Assessment of relevant aspects of the patient’s mental and physical status. Measurement of best corrected visual acuity with spectacles and hard or gas permeaable contact lenses (with refraction when indicated) Measurement of pinhole visual acuity External examination (lids, lashes, lacrimal apparatus, orbit) Examination of ocular alignment and motility Assessment of pupillary function Measurement of intraocular pressure (IOP) Slit-lamp biomicroscopy of the anterior segment Dilated examination of the lens, macula, peripheral retina, optic nerve, and vitreous Keratomety/Computerized Topography//Ultrasound Pachymetry Dr. Mohd Najmussadiq Khan 11/7/2012 22
  23. 23. Symptoms Progressively poor vision not easily corrected with eye glasses.Clinical diagnosis Diagnosis is made based on history of changing refraction, poor best spectacle corrected vision, abnormalities in keratometry, corneal topography and corneal thinning. Dr. Mohd Najmussadiq Khan 11/7/2012 23
  24. 24. Dr. Mohd Najmussadiq Khan 11/7/2012 24
  25. 25.  Asymmetric refractive error with high or progressive astigmatism Keratometry showing high astigmatism and irregularity (axis that do not add to 180 degrees) Scissoring of the red reflex on ophthalmoscopy or retinoscopy. Inferior steepening, skewed axis, or elevated keratometry values on K reading and computerized corneal topography Dr. Mohd Najmussadiq Khan 11/7/2012 25
  26. 26.  Corneal thinning, especially in inferior cornea. Maximum corneal thinning corresponds to the site of maximum steepening or prominence. Rizutti’s sign or a conical reflection on nasal cornea when a penlight is shone from the temporal side Fleischer ring, an iron deposit often present within the epithelium around the base of the cone. It is brown in color and best visualized with a cobalt blue filter Vogt’s striae, fine, roughly vertically parallel striations in the stroma. These generally disappear with firm pressure applied over the eyeball and re-appear when pressure is discontinued. Dr. Mohd Najmussadiq Khan 11/7/2012 26
  27. 27.  Munson’s sign, a protrusion of the lower eyelid in down gaze. Superficial scarring • Break’s in Bowman’s membrane Acute hydrop’s, a condition where a break in Descemet’s membrane allows aqueous into the stoma causing severe corneal thickening, decreased vision and pain. Stromal scarring after resolution of acute hydrops, which paradoxically may improve vision in some cases by changing corneal curvature and reducing the irregular astigmatism. Dr. Mohd Najmussadiq Khan 11/7/2012 27
  28. 28. Dr. Mohd Najmussadiq Khan 11/7/2012 28
  29. 29. Dr. Mohd Najmussadiq Khan 11/7/2012 29
  30. 30.  Differentiation is made between a “quiet” type of keratoconus (“forme fruste”) and progressive keratoconus. “Forme fruste” occurs 10 times more often than progressive keratoconus. Normally it produces no symptoms and has only to be observed. If the condition remains stable, there is no need for treatment. Dr. Mohd Najmussadiq Khan 11/7/2012 30
  31. 31.  Progressive keratoconus is aggressive and can begin at a very early age. With progression of the disease, correction of visual acuity with glasses becomes more difficult because protrusion of the cornea develops unevenly. Hard contact lenses are a good solution because they put pressure on the cornea, thus correcting irregularities. Dr. Mohd Najmussadiq Khan 11/7/2012 31
  32. 32. Diagnostic procedures • Ophthalmic history, including family eye history, heritable disease, history of allergies, etc • Slit-lamp examination • Hard or gas permeable contact lens trial because good vision with lenses eliminates other sources of poor vision, including amploypia • Measurement of K values • Ultrasound Pachymetry • Computerized corneal topography Dr. Mohd Najmussadiq Khan 11/7/2012 32
  33. 33. Dr. Mohd Najmussadiq Khan 11/7/2012 33
  34. 34. Dr. Mohd Najmussadiq Khan 11/7/2012 34
  35. 35. Dr. Mohd Najmussadiq Khan 11/7/2012 35
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  37. 37. Dr. Mohd Najmussadiq Khan 11/7/2012 37
  38. 38. Dr. Mohd Najmussadiq Khan 11/7/2012 38
  39. 39. Laboratory test--Assessment of heritable diseases including • Down’s Syndrome • Leber’s congenital amaurosis • Ehlers Danlos/connective disorder. • Other medical conditions including sleep apneaDifferential diagnosis • Keratoconus . Pellucid marginal degeneration • Keratoglobus • Contact lens induced corneal warpage • Coneal Ectasia post excimer laser treatment Dr. Mohd Najmussadiq Khan 11/7/2012 39
  40. 40.  In 1963, scientists found that the initial changes of KC were related to degradation (break down) of the cornea s basement membrane. They found that over time, a cascade of events occurred, leading to alterations in the layers of the cornea and resulting in the thinning of the stromal layer. This weakened the structural integrity of the cornea and in turn resulted in a bulging, cone- like distortion of the normally spherical cornea. Dr. Mohd Najmussadiq Khan 11/7/2012 40
  41. 41. Dr. Mohd Najmussadiq Khan 11/7/2012 41
  42. 42.  Investigators found that the enzyme activities of the KC corneas were increased compared to normal corneas. In addition, there was a significant reduction of inhibitors for these enzymes. The cornea is responsible for approximately 80% of the absorption of ultraviolet B (UVB) light that enters the eye. UV light generates free oxygen radicals, high energy molecules, which if unchecked, can damage tissue. Dr. Mohd Najmussadiq Khan 11/7/2012 42
  43. 43. Typically, the free radicals are removed fromthe cornea via antioxidants (such as superoxidedismutase, catalase and glutathione reductase).Those that are not removed undergo reactionsthat form aldehydes, which can be destructiveto the tissue Dr. Mohd Najmussadiq Khan 11/7/2012 43
  44. 44.  Normally, the cornea protects itself from these aldehydes with an enzyme called aldehyde dehydrogenase (ALDH) which detoxifies these aldehydes. ALDH is a major protein within the cornea. (Approximately 78% of the ALDH within the eye is found in the cornea.). In the KC cornea there is decreased activity of ALDH enzyme. Dr. Mohd Najmussadiq Khan 11/7/2012 44
  45. 45. These peroxynitrites are also harmful to tissues and canbe identified by using antibodies to nitrotyrosine.KC corneas have an increased amount of nitroytrosinestaining compared to normal corneasThis increased staining in KC corneas suggests that theyhave additional destructive substances in the tissue. Dr. Mohd Najmussadiq Khan 11/7/2012 45
  46. 46.  Normally, the human cornea has very little apoptosis occurring. Dr. Wilson demonstrated that KC corneas have apoptosis occurring in the anterior stroma and epithelium, especially in the areas of breaks in Bowmans layer. Dr. Mohd Najmussadiq Khan 11/7/2012 46
  47. 47.  KC corneas produce a unique enzyme that is not found in normal corneas or corneas with other diseases. This enzyme is called leukocyte common antigen related protein (LAR). LAR in KC corneas also supports the notion of apoptosis in KC corneas because other investigators have shown in other systems that LAR expression plays a role in apoptosis. Dr. Mohd Najmussadiq Khan 11/7/2012 47
  48. 48.  The goal of future research studies is to understand the biochemical and molecular changes and possible genetic influences that occur in KC corneas. Intervention at one of these steps might be the key factor needed to block the progression of keratoconus. Dr. Mohd Najmussadiq Khan 11/7/2012 48
  49. 49. General treatment --The goal of treatment is primarily to provide functional visual acutiy. More recently attention has been directed to halting changes in the corrneal shape. Initially, spcetacles or soft toric contact lenses in mild cases can be used. Dr. Mohd Najmussadiq Khan 11/7/2012 49
  50. 50. Dr. Mohd Najmussadiq Khan 11/7/2012 50
  51. 51. Dr. Mohd Najmussadiq Khan 11/7/2012 51
  52. 52.  Patients with very mild disease may initially be corrected with glasses or soft contact lenses. However the vast majority of patients need rigid contact lenses for adequate vision correction. The very latest contact lens for treating keratoconus is the “synergize hybrid contact lens” which is rigid in the middle and soft on the edges. Dr. Mohd Najmussadiq Khan 11/7/2012 52
  53. 53.  Needed in the majority of cases to neutralize the irregular corneal astigmatism. It resurfaces the irregular cornea & the intervening fluid and corrects the irregular astigmatism to provide good quality of vision. However the disadvantage with these lenses is that they have standard lens design with fixed optical zones and do not give an ideal fit in patients with keratoconus The majority of patients that can wear hard or gas-permeable contact lenses have a dramatic improvement in their vision. Dr. Mohd Najmussadiq Khan 11/7/2012 53
  54. 54. Dr. Mohd Najmussadiq Khan 11/7/2012 54
  55. 55.  Many patients find their contact lenses uncomfortable and can only tolerate their contact lenses for a short period of time. The reason is that the cornea steepens and rubs against the lens causing an abrasion and light sensitivity .
 Another reason is patients with keratoconus often have very dry eye and as the eye dries out there is no lubricating barrier between the lens and the cornea contributing to the patient being uncomfortable. Dr. Mohd Najmussadiq Khan 11/7/2012 55
  56. 56.  RoseK-- The Rose-k lenses are made with complex geometry to fit any type of cone. The optical zone is reduced to snugly fit the cone & the peripheral curve is computer designed to fit the rest of the irregular cornea. Dr. Mohd Najmussadiq Khan 11/7/2012 56
  57. 57.  piggy back lens-- they are known as piggy back because a RGP Lens is fitted on top of a soft contact lens. These lenses provide excellent comfort and good vision. Dr. Mohd Najmussadiq Khan 11/7/2012 57
  58. 58.  Scleral Contact Lenses: They are made of a special polymer called Itaflurocon. They characteristically vault over the cornea and limbus and are supported entirely by the sclera. The fluid lens smoothens the irregular cornea and provides good vision. It also prevents desiccation due to its very high oxygen permeability. The small pores on the lens provide adequate exchange of tears. The disadvantage with these lenses is that they are difficult to use. They are large lenses which are cumbersome to the patients. Dr. Mohd Najmussadiq Khan 11/7/2012 58
  59. 59.  Boston Scleral Contact lenses (BSLP): BSLP lenses are made of Flurosilicone Acrylate Polmers with DK values of 87 and 130. Its diameter ranges from15.5mm to 20mm. The space created over the cornea is filled with non-preserved, buffered sterile saline. The limitation to the use of these lenses is that the fitting process is skill intensive and time consuming. Dr. Mohd Najmussadiq Khan 11/7/2012 59
  60. 60. Those patients that become contact lensintolerant or do not have acceptable vision,typically from central scaring, can proceed tosurgical alternatives Dr. Mohd Najmussadiq Khan 11/7/2012 60
  61. 61. Medical therapy—for acute corneal hydrops involves a cycloplegic agent sodium chloride 5% ointment or eye drop Lubricating eye drop Steroid drops can be used if the eye is congested a pressure patch After the pressure patch is removed patients may still need to continue sodium chloride drops or ointment for several weeks to months. Patients are advised to avoid vigorous eye rubbing Dr. Mohd Najmussadiq Khan 11/7/2012 61
  62. 62. Dr. Mohd Najmussadiq Khan 11/7/2012 62
  63. 63.  It takes 3 - 4 months for the corneal edema to resolve, following which a standard full thickness keratoplasty is required to restore corneal clarity and visual improvement. It this situation lamellar surgery is not recommended Thermokeratoplasty has been tried and believed to shrinkage of the collagen with resultant flattening of the hydrops which helps in early healing of the ruptured DM. Dr. Mohd Najmussadiq Khan 11/7/2012 63
  64. 64.  Patients are usually followed on a 6-month to yearly basis to monitor the progression of the corneal thinning, steepening, the resultant visual changes, and to re-evaluate contact lens fit and care. Patients with hydrops are seen more frequently until it resolves. Dr. Mohd Najmussadiq Khan 11/7/2012 64
  65. 65.  When patients become intolerant or no longer benefit from contact lenses, surgery is the next option. Surgical options can include: INTACS, Anterior lamellar keratoplasty, penetrating keratoplasty. Non- FDA approved treatments, which typically have less evidence based information available on safety and efficacy, include use of UV/riboflavin collagen cross-linking of the cornea to stiffen the cornea and possibly prevent progressive changes in shape. This treatment has also be experimentally combined with excimer laser treatment, conductive keratoplasty, and/or INTACS. Some surgeons will use phakic IOLs to address high myopia and some of the asitigmatism. Dr. Mohd Najmussadiq Khan 11/7/2012 65
  66. 66. Dr. Mohd Najmussadiq Khan 11/7/2012 66
  67. 67.  The most promising technology for treating Keratoconus called collagen crosslinking (CXL) with UVA is currently being introduced It is undergoing Phase 1 FDA clinical trials in the United States. It has been demonstrated to be safe and effective if performed, with the epithelium removed, and has the potential to stop the progression of Keratoconus. Dr. Mohd Najmussadiq Khan 11/7/2012 67
  68. 68.  This treatment is recommended for individuals with progressive Keratoconus or Ectasia following LASIK to stabilize the cornea. It can be performed with our without INTACS. Dr. Mohd Najmussadiq Khan 11/7/2012 68
  69. 69. CORNEAL COLLAGEN CROSS-LINKING (C3R/CXL): The basic problem in keratoconus is the weakness of the cross links which act as anchors between the collagen fibrils. UV-A irradiance of the cornea after sensitization with riboflavin, augments these cross-links, and hence recovers some of the corneal mechanical strength in keratoconus. This treatment modality stabilizes the collagen scaffold and increases the stiffness of the cornea against the action of proteolytic enzymes. Riboflavin/UVA light causes increase in the corneal stiffness of the anterior 200-250 μm. Deeper structures like the lens and endothelium do not get damaged. The progression of keratoconus or keratectasia can be stopped. Dr. Mohd Najmussadiq Khan 11/7/2012 69
  70. 70.  This results in cross linking of the collagen fibres of the cornea, thereby increasing its physical strength by up to 300%. Thus further progression of keratoconus can be arrested, and in 15 -20% cases regression has also been noted. Longest follow-up duration following this treatment is for 7 years. Dr. Mohd Najmussadiq Khan 11/7/2012 70
  71. 71. Dr. Mohd Najmussadiq Khan 11/7/2012 71
  72. 72. Dr. Mohd Najmussadiq Khan 11/7/2012 72
  73. 73.  The top layer of the cornea is removed under local anesthesia. Vitamin drops are soaked into the cornea until they penetrate the entire corneal and evidence of penetration into the anterior chamber of the eye is demonstrated by slit-lamp evaluation. Once this is confirmed the patient’s eye is put under a specialized lamp, which emits UV A light at a predetermined wavelength for approximately 30 minutes. During this process the cross links, which link the fibers of the cornea, are increased thereby stiffening the whole cornea. A bandage contact lens is then put on the eye and patients are given antibiotics and anti-inflammatory drops and follow up on a regular basis with their physicians for several months. Dr. Mohd Najmussadiq Khan 11/7/2012 73
  74. 74. Dr. Mohd Najmussadiq Khan 11/7/2012 74
  75. 75. Dr. Mohd Najmussadiq Khan 11/7/2012 75
  76. 76.  During the post-operative period flurometholone and artificial tears are applied for a period of one month. In the pilot study done on 23 eyes and followed up to 4 years Wollensak et al found a mean reduction in steepening of 2.01 D. Other investigators such as caporossi et al and Krumeich et al reported a similar result. The improvement in vision after cross-linking is caused by a decrease in astigmatism and corneal curvature as well as topographical homogenization of the cornea as a result of the increased rigidity in the cross- linked cornea. In addition tolerance to contact lenses improved. Cross-linking is a practical outpatient treatment, which is minimally invasive and cost-effective. Dr. Mohd Najmussadiq Khan 11/7/2012 76
  77. 77. Dr. Mohd Najmussadiq Khan 11/7/2012 77
  78. 78.  A method for flattening the cornea that is too steep and making a patient more contact lens tolerant is the insertion of INTACS into the cornea. This procedure is good for patients who are contact lens intolerant and who want to avoid a corneal transplant and whose K readings are not in excess of 58 Diopters. (INTACS ) have been approved for the treatment of mild to moderate keratoconus in patients who are contact lens intolerant. Dr. Mohd Najmussadiq Khan 11/7/2012 78
  79. 79.  In these cases, patients must have a clear central cornea and a corneal thickness of > 450 microns where the segments are inserted, approximately at 7 mm optical zone. Intrastromal corneal ring segments (Intacs Addition Technology Inc) have crescent shaped two 150-degree PMMA segments that are surgically placed in the peripheral cornea at two- thirds corneal depth. Intacs comes in thickness ranging from 0.25 to 0.45 mm in 0.05 mm increments. Intacs correct the myopia and irregular astigmatism by producing a mechanical flattening of the central cone. Dr. Mohd Najmussadiq Khan 11/7/2012 79
  80. 80.  The advantage of INTACS is that they require no removal of corneal tissue, no intraocular incision, and leave the central cornea untouched. Most patients will need spectacles and/or contact lenses post-operatively for best vision, but will have flatter corneas and easier use of lenses. If a patient does not gain the expected results, the INTACS can be removed and then other surgical options can be considered Dr. Mohd Najmussadiq Khan 11/7/2012 80
  81. 81. Dr. Mohd Najmussadiq Khan 11/7/2012 81
  82. 82.  Femtosecond laser technology allows realization with very high accuracy of individualized shape and size of corneal tunnel depending on the surgical need. Intrastromal cuts from the inner to the outer parts of the cornea can be performed easily. During surgery, stress to the cornea is minimal, because only moderate pressure is exerted on the eye. The risk of infection is significantly reduced. Dr. Mohd Najmussadiq Khan 11/7/2012 82
  83. 83.  Kera rings are tiny plastic semicircular rings surgically implanted into the cornea to flatten the corneal surface and improve vision. Inserts can improve contact lens wear in most patients. They are not suitable for all patients with keratoconus. Implantation does not affect the central optic zone, does not involve the removal of any tissue, and can be reversed if vision changes. Dr. Mohd Najmussadiq Khan 11/7/2012 83
  84. 84. Imagine your cornea asa tent with a curved top.If you push out the sidesof the tent, the topflattens.Similarly, when Kerarings are placed in thesides of the cornea, theyflatten it. Dr. Mohd Najmussadiq Khan 11/7/2012 84
  85. 85. Combined KERARINGS insertion and CXL can be performed safely in one ortwo sessions. However, the same-session procedure appears to be moreeffective regarding the improvement in the corneal shape. Br J Ophthalmol.2011 Jan;95(1):37-41. Epub 2010 Jun 28. Dr. Mohd Najmussadiq Khan 11/7/2012 85
  86. 86.  Laser may now be used to treat keratoconus. The technique is similar to the Lasek laser done for short sight etc, but uses a cornea topographer to guide the laser. The laser reduces the keratoconic protrusion, significantly improving vision. When controlled by a topographer only a few microns of cornea need be removed, greatly enhancing safety. The technique is effective for mild-to-moderate keratoconus. To stabilize the cornea after laser, collagen cross linking is done. Only the most sophisticated lasers, such as the Alcon Wave light EX500 excimer laser can be used Dr. Mohd Najmussadiq Khan 11/7/2012 86
  87. 87. Dr. Mohd Najmussadiq Khan 11/7/2012 87
  88. 88.  It is the newest procedure under investigation for the treatment of keratoconus. It is non-incisional and reshapes the cornea without removing any tissue. It is currently under clinical investigation in Europe for treating myopia and keratoconus. It involves the delivery of a single low energy microwave pulse lasting less than one second to the cornea. Energy is applied to the cornea using a dielectrically shielded microwave emitter which contacts the epithelial surface. Through capacitive coupling, the single pulse raises the temperature of the selected region of corneal stroma to approximately 65°C, forming a doughnut-shaped area of collagen shrinkage in the upper 150 microns of the stroma. Dr. Mohd Najmussadiq Khan 11/7/2012 88
  89. 89.  The lesion created during Keraflex is intended to flatten the central cornea both to decrease the cone in keratoconus and to achieve myopic correction. In order to improve the stability of the cornea with Keraflex, Keraflex KXL includes focal corneal collagen crosslinking. After the actual Keraflex procedure, riboflavin drops are administered over the treatment area, a mask is applied to protect the central and peripheral areas of the cornea, and ultraviolet light is admistered to crosslink the collagen. Dr. Mohd Najmussadiq Khan 11/7/2012 89
  90. 90.  Corneal Transplants are the only option for patients who have scarring in the center of the cornea or who are contact lens intolerant because their corneas are too steep. The results of corneal transplants are excellent in keratoconus patients with an over 97% success rate. Patients can have LASIK or PRK on their transplants and become relatively independent of glasses or contact lenses. Recently the Femtosecond Laser was approved for performing Corneal Transplants Dr. Mohd Najmussadiq Khan 11/7/2012 90
  91. 91.  It involves replacement of the central anterior cornea, leaving the patient’s endothelium intact. The advantages are that the risk of endothelial graft rejection is eliminated, and there is less risk of traumatic rupture of the globe in the incision, since the endothelium and Descemet’s and some stroma are left intact, and faster visual rehabilitation. Dr. Mohd Najmussadiq Khan 11/7/2012 91
  92. 92.  There are several techniques utilized including, deep anterior lamellar keratoplasty (DALK) and big bubble keratoplasty(BBK) to remove the anterior stroma, while leaving Descemet’s layer and endothelium untouched. However, the procedures can be technically challenging requiring conversion to a penetrating keratoplasty Post-operatively there is the possibility of interface haze leading to a decrease in BCVA It is not clear if astigmatism is better treated with anterior vs penetrating keratoplasty. Dr. Mohd Najmussadiq Khan 11/7/2012 92
  93. 93. Dr. Mohd Najmussadiq Khan 11/7/2012 93
  94. 94. Dr. Mohd Najmussadiq Khan 11/7/2012 94
  95. 95.  In DALK the bottom layer of the cornea is spared this results in less chance of rejection. It should be remembered however that in some instances the separation of the bottom layers of the cornea and the upper parts might be uneven which would result in poorer visual outcomes. Dr. Mohd Najmussadiq Khan 11/7/2012 95
  96. 96. Dr. Mohd Najmussadiq Khan 11/7/2012 96
  97. 97. Descemets exposedDALK(deepanteriorlamellarkeratoplasty Dr. Mohd Najmussadiq Khan 11/7/2012 97
  98. 98.  It has a high success rate and is the standard surgical treatment with a long track record of safety and efficacy. Risks of this procedure include infection and cornea rejection and risk of traumatic rupture at wound margin. Many patients after PK may still need hard or gas- permeable contact lenses due to residual irregular astigmatism Any type of refractive procedure is considered a contraindication in keratoconic patients due to the unpredictability of the outcome and risk of leading to increased and unstable irregular astigmatism. Dr. Mohd Najmussadiq Khan 11/7/2012 98
  99. 99. Dr. Mohd Najmussadiq Khan 11/7/2012 99
  100. 100. 10Dr. Mohd Najmussadiq Khan 11/7/2012 0
  101. 101. 10Dr. Mohd Najmussadiq Khan 11/7/2012 1
  102. 102.  Following any corneal surgical procedure, patients need to be followed to complete visual rehabilitation. Most patients still require vision correction with spectacles or contact lenses, and often hard or gas permeable lenses are required if high levels of astigmatism are present. All surgical patients need to be followed to ensure wound healing, evaluation for infection, suture removal and other routine eye care, such as testing for glaucoma, cataracts and retinal disease. Graft rejection can occur after penetrating keratoplasty, requiring prompt diagnosis and treatment to ensure graft survival. 10 Dr. Mohd Najmussadiq Khan 11/7/2012 2
  103. 103. Complications Infection poor wound healing cornea transplant rejection corneal neovascularization Glare irregular astigmatism high refractive error 10 Dr. Mohd Najmussadiq Khan 11/7/2012 3
  104. 104. Prognosis The prognosis for penetrating keratoplasty in a keratoconic patient is excellent, with most patients able to return to an active lifestyle and the pursuit of personal goals. Intrastromal corneal ring segments (such as Intacs) can provide long-term success for patients with keratoconus, but this is typically in conjunction with contact lens use, and some may ultimately require corneal transplant to reach their goals of visual rehabilitation. "Progression" of keratoconus, even after corneal surgery, has been reported, but it is not clear how common or to what extent this can occur 10 Dr. Mohd Najmussadiq Khan 11/7/2012 4
  105. 105.  The donor stromal lenticule was created using the femtosecond laser (Intralase). The diameter of the lamellar cut was 9 mm. The laser parameters were set to cut the first lamellar interface at a depth of 400 μm posterior to the epithelial surface. A side cut was then performed creating a tapered edge to the lenticule. Then, a second superficial lamellar cut was made at a depth of 150 μm posterior to the epithelial surface. This produced a 250-μm donor corneal lamellar disc. 10 Dr. Mohd Najmussadiq Khan 11/7/2012 5
  106. 106.  Next, a stromal pocket was formed in the host cornea at a depth of 250 μm using the Intralase. The diameter of the pocket was 9.5 mm, with a 3.0-mm exit incision at the 12 o’clock position The patient was then taken to the operating room where prepared with povidone-iodine 10% solution The donor lamellar lenticule was folded and inserted into the host stromal pocket through the anterior incision. The donor lenticule was centered and smoothed with a cyclodialysis spatula. The wound was closed with a single 10-0 nylon suture. 10 Dr. Mohd Najmussadiq Khan 11/7/2012 6