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Shape factor variations: a mostly overlooked entity in IOL calculation

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Session Details

Session Title: Cataract Surgery Outcomes: IOL Power Calculations

Session Date/Time: Sunday 08/10/2017 | 14:30-16:00

Paper Time: 15:12

Venue: Meeting Center Room I

First Author: : P.Preussner GERMANY

Co Author(s): :                        

Abstract Details


To explain and quantitatively show the impact of power-level dependent IOL shape factor variations on postoperative refraction for different frequently implanted IOL models


University Eye Hospital Mainz, Germany


The deviation from biconvex or biconcave symmetry of a lens is described by the so-called 'shape factor'. Many frequently implanted IOLs are not biconvex / biconcave symmetric but have a non-zero shape factor that changes with the power level. This causes differences in the resulting refraction which cannot be adressed by 'IOL formula constants'. In fact, these 'constants' would be different for different IOL power levels. The said phenomenon can only be adressed with the original IOL manufacturing data as they are used in raytracing. Quantitatively, the variations are often negligible but can exceed 0.5D in some cases.


The impact of shape factor variations are graphically demonstrated for some frequently implanted IOL models.


When high accuracy is required in IOL calculation, also variations of the IOL shape factor should be adressed which requires raytracing based on original IOL manufaturer's data.

Financial Disclosure:

gains financially from product or procedure presented

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