IOLs & Biometry Alireza Peyman, MD Isfahan University of Medical Sciences

Sir Nicholas Harold Lloyd Ridley 10 July 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 technique No gloves or microscope was availabel 20% failure rate

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

IOLs Phakic –Angle supported –Iris claw –Sulcus Aphakic

IOLs PMMA Foldable –Hydrophilic –Hydrophobic –silicon Plate haptic, C loop, 3piece, 1piece,.. Spherical, Aspheric,.. Blue light filtering, UV filtering Multifocal, Accommodative Toric, …

Multifocal Refractive IOLs ReZoom™ intraocular lens, are designed with several optical zones

Apodized Diffractive Multifocal IOL Acrysof® ReSTOR® intraocular lens

Accommodative IOL Crystalens™ intraocular lens

IOL power selection is more important than IOL brand

IOL POWER CALCULATION

History of IOL power calculation Before 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 data In 1978 first regression formula published, this formula later evolved to SRK II in 1980

Regression formulas Regression 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 error “P” is power for emmetropia “I” is inserted power –A change of 1.5 diopter implant power produces a change of approximately 1 D in final refraction.

3 rd and 4 th generation formulas SRK/T Hoffer Q Holladay I Haigis Holladay II

Formulas are for in the bag IOL

WHICH FORMULA SHOULD USED?

AL < 22 short eye AL > 25 long eye

My opinion Axial LengthFormula <22 mmHoffer Q 22 – 24.5 mmSRK/T, Holloday I, and Haigis (mean) > 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 Q For 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

SNR SNR > 2 is good if repeatable SNR 1.6 – 2 is borderline, considered OK if repeatable <1.6 is ERROR Repeat measurement at least 5 times

ضمن عرض پوزش بدلیل حجم بالای LECTUER ادامه اسلایدها امکان پذیر نمیباشد در صورت نیاز به ادامه لطفا به واحد سمعی و بصری مرکز آموزشی درمانی فیض مراجعه و یا با شماره تلفن داخلی 392 تماس حاصل نمائید با تشکر