Posters

The importance of the posterior corneal surface in biometry

Poster Details

First Author: G. Negretti UNITED KINGDOM

Co Author(s):    N. Davies                    

Abstract Details

Purpose:

Null Hypothesis: Accurately measuring corneal power with anterior segment OCT does not influence refractive accuracy post cataract surgery.

Setting:

Chelsea and Westminster NHS Foundation Trust, London, United Kingdom

Methods:

1. The anterior and posterior corneal curvature was measured using OCT for 100 patients and the degree of variation in the ratio between them was analysed. 2. 20 patients underwent conventional pre-operative biometry using Zeiss IOL Master. Anterior Segment OCT was also performed. Refraction 6 weeks post cataract surgery of the 20 patients. Investigation of whether refractive accuracy could be improved if corneal power derived from AS OCT was used rather than the estimated corneal power used by conventional biometry.

Results:

1. Minimal variation in the ratio between anterior and posterior corneal curvature in the 100 eyes analysed. 2. Patients who had large refractive errors post-operatively did not tend to have large errors in their corneal power estimation using the Dunne ratio, Gullstrand ratio or the reduced refractive index of 1.3333 as used by SRK/T.

Conclusions:

1. Null hypothesis not rejected. 2. Despite the posterior to anterior corneal curvature not being completely constant. This variability, in reality, does not seem to matter in terms of refractive outcome when using conventional biometry. 3. There is no indication for anterior segment OCT on all pre-operative cataract patients. It is extremely useful in those post laser refractive surgery however.

Financial Disclosure:

NONE