A-SCAN BIOMETRY | What is A-Scan Biometry? How To Use It?
A-scan is the short form of amplitude scan.
This eye ultrasound gives details about the length of the eye.
A-Scan is an essential diagnostic tool used in ophthalmology.
The measurement of the eye’s axial length through an A-scan is necessary for placing an intraocular lens (IOL, artificial lens) during cataract surgery.
The total refractive power of the emmetropic eye is approximately 60D. Of this power, the cornea provides roughly 40D, and the crystalline lens 20 diopters.
When a cataract is removed, the lens is replaced by an artificial lens implant. By measuring both the length of the eye (A-scan Biometry) and the power of the cornea (keratometry).
It may also be used to assess vision abnormalities and other diseases involving the eye such as tumors.
A-scan techniques are based on the principles of ultrasonography. Sound travels in a wave pattern. For a sound to be heard by the human ear, the frequency must be between 20 and 20,000 Hz (20 kHz).
For an eye examination through A-scan, an ultrasound of frequency of around 10 MHz is used.
Keratometer is an ophthalmic instruments and has a very important role in optometry field specially for IOL power calculation, Contact lens fitting, to rule out corneal pathology and its progression ie Keratoconus, PMCD.
Detailed instumentaion and use of manual Lensometer and just a outline of automated lensometer.
I have used the picture of manual lensometer with out the parts describtion because i have explained orally by showing the picture..
Hope u all like it and may help you in learning better. :)
Keratometer is an ophthalmic instruments and has a very important role in optometry field specially for IOL power calculation, Contact lens fitting, to rule out corneal pathology and its progression ie Keratoconus, PMCD.
Detailed instumentaion and use of manual Lensometer and just a outline of automated lensometer.
I have used the picture of manual lensometer with out the parts describtion because i have explained orally by showing the picture..
Hope u all like it and may help you in learning better. :)
To know Humphrey visual field analyser
To know about various types of perimetry
To identify field defect
To recognize that field defect is due to glaucoma or neurological lesion
To know that field defect is progressive or not
Interpretation of HVFA
Describes the basic of applanation tonometry, the factors affecting it and also how to perform the ideal tonometry. The slide are borrowed but it gives complete idea of mastering Applanation tonometry.
If the original owner of the slides has an objection i shall take down the ppt with due apologies.
Accommodation/ Accommodation of Eye, Measurement of Accommodation of Eye (hea...Bikash Sapkota
CLICK HERE TO DOWNLOAD FULL PPT ❤❤ https://healthkura.com/measurement-of-accommodation-of-eye/ ❤❤
Dear viewers Check Out my other piece of works at ❤❤❤ https://healthkura.com ❤❤❤
Measurement of Accommodation of eye:
Amplitude, Facility,
Relative Accommodation, Fatigue, Lag,
Dynamic Retinoscopy
Presentation Layout:
-Introduction to accommodation of eye
-Mechanism
-Components
-Measurement of accommodation of eye
- Amplitude
- Facility
- Relative accommodation
- Lag
-Dynamic Retinoscopy
Accommodation
-dioptric adjustment of the crystalline lens of the eye
- to obtain clear vision for a given target of regard
-process by which the refractive power of eye is altered
- to ensure a clear retinal image
For further reading
-Clinical Procedures in Optometry by J.D. Bartlett, J.B. Eskridge, J.F. Amos
-Primary Care Optometry by Theodere Grosvenor
-Borish’s Clinical Refraction by W.J. Benjamin
-Clinical Procedures for Ocular examination by Carlson et al
-American Academy of Ophthalmology
-Optometric Clinical Practice Guideline by American Optometric Association
-Internet
Follow me to get in touch with optometric and ophthalmic updates
To know Humphrey visual field analyser
To know about various types of perimetry
To identify field defect
To recognize that field defect is due to glaucoma or neurological lesion
To know that field defect is progressive or not
Interpretation of HVFA
Describes the basic of applanation tonometry, the factors affecting it and also how to perform the ideal tonometry. The slide are borrowed but it gives complete idea of mastering Applanation tonometry.
If the original owner of the slides has an objection i shall take down the ppt with due apologies.
Accommodation/ Accommodation of Eye, Measurement of Accommodation of Eye (hea...Bikash Sapkota
CLICK HERE TO DOWNLOAD FULL PPT ❤❤ https://healthkura.com/measurement-of-accommodation-of-eye/ ❤❤
Dear viewers Check Out my other piece of works at ❤❤❤ https://healthkura.com ❤❤❤
Measurement of Accommodation of eye:
Amplitude, Facility,
Relative Accommodation, Fatigue, Lag,
Dynamic Retinoscopy
Presentation Layout:
-Introduction to accommodation of eye
-Mechanism
-Components
-Measurement of accommodation of eye
- Amplitude
- Facility
- Relative accommodation
- Lag
-Dynamic Retinoscopy
Accommodation
-dioptric adjustment of the crystalline lens of the eye
- to obtain clear vision for a given target of regard
-process by which the refractive power of eye is altered
- to ensure a clear retinal image
For further reading
-Clinical Procedures in Optometry by J.D. Bartlett, J.B. Eskridge, J.F. Amos
-Primary Care Optometry by Theodere Grosvenor
-Borish’s Clinical Refraction by W.J. Benjamin
-Clinical Procedures for Ocular examination by Carlson et al
-American Academy of Ophthalmology
-Optometric Clinical Practice Guideline by American Optometric Association
-Internet
Follow me to get in touch with optometric and ophthalmic updates
National Ocular Biometry Course (NOBC) 2015 An echoslide presentation Anis Suzanna Mohamad
This powerpoint presentation is basically about ocular biometry. Echo presentation is one of the method to deliver infomation that obtain from the course we attend to other staff in our Ophthalmology Department.
introduction into Biometry and it's formulas.pptxQusaiAbusleem1
Biometry is the practice of applying mathematics to biology .
With regard to ophthalmology , there are several biometric systems used for making precise measurements of ocular structures : ultrasound (A- and B-scan , pachymeter) , low coherence interferometry (OCT) , laser interferometry (IOL Master , Lenstar)
These systems are used in measurement of axial length ,keratometry , pachymetry , and retinal thickness , among other things .
The term biometry , as it relates to ophthalmology , typically refers to preoperative measurements made for IOL calculations.
Biometry explanation and the used formulas.pptxQusaiAbusleem1
Biometry is the practice of applying mathematics to biology .
With regard to ophthalmology , there are several biometric systems used for making precise measurements of ocular structures : ultrasound (A- and B-scan , pachymeter) , low coherence interferometry (OCT) , laser interferometry (IOL Master , Lenstar)
These systems are used in measurement of axial length ,keratometry , pachymetry , and retinal thickness , among other things .
The term biometry , as it relates to ophthalmology , typically refers to preoperative measurements made for IOL calculations.
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
The Roman Empire A Historical Colossus.pdfkaushalkr1407
The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
How to Create Map Views in the Odoo 17 ERPCeline George
The map views are useful for providing a geographical representation of data. They allow users to visualize and analyze the data in a more intuitive manner.
The Indian economy is classified into different sectors to simplify the analysis and understanding of economic activities. For Class 10, it's essential to grasp the sectors of the Indian economy, understand their characteristics, and recognize their importance. This guide will provide detailed notes on the Sectors of the Indian Economy Class 10, using specific long-tail keywords to enhance comprehension.
For more information, visit-www.vavaclasses.com
Model Attribute Check Company Auto PropertyCeline George
In Odoo, the multi-company feature allows you to manage multiple companies within a single Odoo database instance. Each company can have its own configurations while still sharing common resources such as products, customers, and suppliers.
Palestine last event orientationfvgnh .pptxRaedMohamed3
An EFL lesson about the current events in Palestine. It is intended to be for intermediate students who wish to increase their listening skills through a short lesson in power point.
The French Revolution, which began in 1789, was a period of radical social and political upheaval in France. It marked the decline of absolute monarchies, the rise of secular and democratic republics, and the eventual rise of Napoleon Bonaparte. This revolutionary period is crucial in understanding the transition from feudalism to modernity in Europe.
For more information, visit-www.vavaclasses.com
Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
Ethnobotany and Ethnopharmacology:
Ethnobotany in herbal drug evaluation,
Impact of Ethnobotany in traditional medicine,
New development in herbals,
Bio-prospecting tools for drug discovery,
Role of Ethnopharmacology in drug evaluation,
Reverse Pharmacology.
1.4 modern child centered education - mahatma gandhi-2.pptx
A scan biometry | How to Use A-scan? Types of A-Scan Biometry?
1. What, How & Types
Of A-Scan Biometry
OPTOM.Naeem Ahmad
2. A-scan is the short form of amplitude scan
• The Ultrasound gives details about the length of the eye.
• A-Scan is an essential diagnostic tool used in ophthalmology.
• The measurement of the eye’s axial length through an A-scan is necessary for placing an
intraocular lens (IOL, artificial lens) during cataract surgery.
2
3. The total refractive power of the emmetropic eye is
approximately 60D. Of this power, the cornea provides
roughly 40D, and the crystalline lens 20D.
• When a cataract is removed, the lens is replaced by an
artificial lens implant. By measuring both the length of
the eye (A-scan Biometry) and the power of the
cornea (keratometry).
• It may also be used to assess vision abnormalities
and other diseases involving the eye such as tumors.
• A-scan techniques are based on the principles of ultrasonography. Sound travels in a wave
pattern. For a sound to be heard by the human ear, the frequency must be between 20 and
20,000 Hz (20 kHz).
• For an eye examination through A-scan, an ultrasound of frequency of around 10 MHz is used.
3
4. a. Probe tip. Echo from the tip of the probe,
now moved away from the cornea and has
become visible.
b. Cornea. A double-peaked echo will show
both the anterior and posterior surfaces.
c. Anterior lens capsule.
d. Posterior lens capsule.
e. Retina. This echo needs to have sharp 90-
degree take-off from the baseline.
f. Sclera.
g. Orbital fat.
4
6. • In A-scan biometry, the sound travels through the solid cornea, the liquid aqueous, the solid lens, the
liquid vitreous, the solid retina, choroid, sclera, and then orbital tissue; therefore, it continually
changes velocity.
6
8. A-scan biometry by applanation requires that the
ultrasound probe be placed directly on the corneal
surface. This can either be done at the slit lamp, or by
holding the ultrasound probe by hand.
PROCEDURE: Hand-Held Method
• Explain the procedure
• Anesthetize the patient’s eye with a topical anesthetic
such as Proparacaine. Please refer to the
manufacturer’s instructions for proper use.
• Clean the probe
• A probe is placed on the patient‘s cornea.
• The probe is attached to a device that delivers adjustable sound waves.
• The measurements are displayed as spikes on the screen of an oscilloscope (Visual monitor).
• The appearance of the spikes and the distance between them can be correlated to structures
within the eye and the distance between them.
8
9. There are Five basic types of limitations are :-
1.Variable corneal compression.
2.Broad sound beam without precise localization.
3.Limited resolution.
4.Incorrect assumptions regarding sound velocity.
5.Potential for incorrect measurement distance.
9
10. • Preferred over applanation: With the immersion
A-scan
• Technique, the probe tip does not come into
contact with the cornea.
• Instead, the ultrasound beam is coupled to the
eye through the fluid(with saline). Because
there is no corneal compression, the displayed
result more closely represents the true axial
length.
• When the ultrasound beam is properly aligned
with the center of the macula, all five spikes
(cornea, anterior and posterior lens capsule,
retina and sclera) will be steeply rising and of
maximum height.
10
Note: Be sure to set your ultrasound machine
to immersion mode, if it doesn’t automatically
do so, or you will get meaningless readings
that are several mm too long.
11. • The immersion technique requires the use of a Prager
Scleral Shell (pictured at the top of this page), or a set
of Ossoinig or Hansen Scleral Shells.
• We have found that the Prager Scleral Shell is the
easiest to use, and gives very consistent readings.
• The patient lies supine, looking up at the ceiling and the
scleral shell is placed between the eyelids and
centered over the cornea. The scleral shell is then filled
with a 40-60 mixture of Goniosol and Dacriose and the
probe tip is placed into the solution. Align the
ultrasound beam with the macula by having the patient
look at the probe tip fixation light, then simply take your
readings as usual. 11
12. • Defined as the electronic amplification factor of
the sound waves received by the transducer, it is
measured in decibel (dB). Normal setting is
around 70% -75%. But it may be increased where
high echoes are inadequate (hard cataracts,
dense ocular opacities, high myopia). It is
decreased when artifacts are seen near the
retinal spikes (silicone filled eyes & in
pseudophakics).
12
13. • In cataract surgery or other lens-replacement
procedures, vision is improved by replacing the eye’s
natural lens with an intraocular lens (IOL).
• IOLs come in different powers and sizes to compensate
for each patient’s individual needs. For best vision after
cataract surgery, precise measurements must be taken
to determine which IOL to implant.
• The IOLMaster is a high-precision instrument
revolutionizing all previous techniques and setting a
new standard for IOL calculations, called optical
biometry.
• Optical biometry using IOLMaster does not subject our patients to any discomfort. No local anesthesia is required
and there is no risk associated with taking the measurements.
13
14. • The difference between good vision and great vision after
cataract surgery can be attributed to the diagnostic
technology used to calculate the appropriate IOL. This
technology provides our patients with the opportunity for
the best possible visual outcome.
• The IOLMaster is a great advancement in IOL calculation.
• The risk of confusing right and left eye measurements is
eliminated with this technology. The IOLMaster
automatically detects the right or left eye while taking the
measurement.
• Axis length, corneal radii and anterior-chamber depth of
the eye are measured with the IOLMaster. Three
instruments integrated into one location provides our
patients with a higher level of comfort.
• Measuring the eye with the IOLMaster takes less time
than using ultrasound, the traditional form of measurement
that requires anesthesia.
14
15. Sanders, Retzlaff, and Kraff developed the SRK formula which was widely used. Though now replaced with the newer
generation formulas, it is still useful for understanding the relation of the variables and A-constant to the IOL Power (P).
P = A-0.9K – 2.5 AL
• Where
• P= Power of the IOL in diopters
• A= A constant
• K= Average keratometry value in
diopters
• AL= axial length in mm
• This is rarely used to calculate IOL
power manually where other tools are
not available but should be avoided
whenever possible.
Accuracy of axial length by
different machine
15
16. 16
No matter how good the system is, people will
still make mistakes. Some reasons include:
Some common mistakes (collected from the UK
and overseas departments):
➢ People in a hurry
➢ Lack of training or accessible guidelines
➢ Reliance on others
➢ Technical failure (rarely)
➢ Human error (often).
➢ Wrong a-constant selected
➢ The wrong formula used
➢ Wrong k-readings entered by hand (90 degrees
out)
➢ Biometry print-out stuck in wrong patient’s notes
➢ Incorrectly labeled IOL
➢ Wrong patient in theatre
➢ Reversed IOL optic
➢ The wrong IOL implanted (25.5 D implanted
instead of 22.5 D or +30 D instead of +3.0 d).