iols & biometry alireza peyman, md isfahan university of medical sciences

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Multifocal IOLs

IOLs & BiometryAlireza Peyman, MDIsfahan University of Medical Sciences

Sir Nicholas Harold Lloyd Ridley10 July 190625 May 2001

First IOL manufactured using Perspex on 29 November 1949 at St Thomas' Hospital, by the Rayner company.

Approved for use in the USA by the Food and Drug Administration in 1981

Ridley used ECCE techniqueNo gloves or microscope was availabel20% failure rate

Sir Harold Ridley kneels as he receives knighthood from Queen Elizabeth II of England on February 9, 2000

IOLsPhakicAngle supportedIris clawSulcus

Aphakic

IOLsPMMAFoldableHydrophilicHydrophobicsiliconPlate haptic, C loop, 3piece, 1piece,..Spherical, Aspheric, ..Blue light filtering, UV filteringMultifocal, AccommodativeToric,

Multifocal Refractive IOLsReZoom intraocular lens, are designed with several optical zones

Apodized Diffractive Multifocal IOLAcrysof ReSTOR intraocular lens

Accommodative IOLCrystalens intraocular lens

IOL power selection is more important than IOL brand

IOL power calculation

History of IOL power calculationBefore 1975 the formula for iris-supported IOL power calculation was: P= 18 + (1.25*Ref)

Errors of more than 1D occurred in over 50%Some large errors occurred

First IOL power formula was published in 1967 by Fyodorov and Kolonko.Subsequent formulas from Colenbrander, Hoffer, and Binkhorst incorporated ultrasound dataIn 1978 first regression formula published, this formula later evolved to SRK II in 1980

Regression formulasRegression formulas are derived empirically from retrospective analysis of data on many patients who have undergone surgery

SRK is the most popular regression formula:

Resultant refractory errorP is power for emmetropiaI is inserted power

A change of 1.5 diopter implant power produces a change of approximately 1 D in final refraction.

3rd and 4th generation formulasSRK/THoffer QHolladay I

HaigisHolladay II

Formulas are for in the bag IOL

Which formula should used?

AL < 22 short eyeAL > 25 long eye

My opinionAxial LengthFormula 24.5SRK/T

28mmOptimized Haigis, Holladay II

For normal range all formulae are acceptable, the SRK/T is more popular

For short eyes (hyperopic) use Hoffer QFor long eyes (myopic) use SRK/T

In extreme cases Optimized Haigis, and Holladay II should utilized

Accurate biometry

Accurate AL measurement and keratometry is far more important than which calculation formula is used

SNRSNR > 2 is good if repeatableSNR 1.6 2 is borderline, considered OK if repeatable