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Subha's Ophthalmic Page
search information related to IOL, biometry, corneal topography, etc.
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How the Barrett Universal II formula works - impression from a user
The following video content is an impression of how the Barrett Universal II formula works. Barrett Universal II is an unpublished...
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Jul 27, 20241 min read
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Calculator for deriving corneal power with true indices and radius of curvature of anterior and posterior cornea
This calculator will help you to calculate the power of cornea from the radius of curvature
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Jul 25, 20241 min read
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Difference between labelled IOL power and actual power of the IOL
A common notion amongst clinicians is that the labelled power (diopter) on the IOL box is precisely the power of the IOL. That is, the...
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Jul 3, 20246 min read
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Find : Diameter of central Bull's Eye of diffractive multifocal IOL and to which focal point this light is dedicated to
Objective: This tool helps you to find following things: What is the true size of the diameter of the central bull's eye of the diffractive multifocal IOL Where is the light passing through the bull's eye dedicated to How to Use: A. Enter the add power of the diffractive IOL B. Enter the wavelength of light ( usually 550 or 555 nm of light is the industry standard) Example: A diffractive multifocal IOL of 3.75 add power claiming its central bull's eye zone to be .769 should d
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May 21, 20241 min read
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Why present day IOL box A constant based on thin optics concept needs to be reworked to improve IOL power prediction with thick lens formulae
Objective of this article: In this article I am proposing a method that helps manufacturers as well as users adapt IOL box A constant to...
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Apr 23, 20247 min read
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Calculation of IOL power and location of principal planes based on thick lens formula
This tool helps you to calculate the lens power based on thick lens formula. It also helps locate principal plane in the optic
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Apr 16, 20240 min read
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Understanding Angle Alpha & Angle Kappa- the finer aspects
Optical axis of the eye is a theretical concept. Clinically, if a point source of light was projected to the eye, then all reflexes from the
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Feb 24, 202411 min read
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Why some patients land up with unexpected refractive surprise after IOL implantation.
The refraction shown against target IOL Power in the biometry page is not emmetropia but a spherical equivalent.
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Dec 28, 20235 min read
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Guide to Extended Depth of Focus (EDOF) IOL optics
At the end of the reading, you will get an understanding of the design of the Extended Depth of Focus (EDOF) IOLs in the market, and how the
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Nov 12, 202314 min read
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Understanding the Point Spread Function and Strehl Ratio of a lens system
Point spread Function gives us an understanding of the resolution of an optical system.
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Oct 4, 202312 min read
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Pin hole Test - Interpretation
Interpreting a pin hole test for vision testing.
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Sep 21, 20232 min read
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Haigis L Formula for Post-LASIK IOL Power
This tool will help you to use Haigis L formula for post lasik patients. As first step it helps you to convert K readings.
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Sep 4, 20231 min read
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Shammas post Lasik A-constant and Corneal reading conversion
This allows you to convert post Lasik corneal reading and IOL constant to Shammas post lasik formula with no history method
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Aug 23, 20231 min read
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