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Investigation of keratometry axis repeatability on astigmatic reduction with toric IOLs

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Session Details

Session Title: Pseudophakic IOLs: Toric

Session Date/Time: Tuesday 10/10/2017 | 08:30-10:30

Paper Time: 09:46

Venue: Room 4.4

First Author: : C.Hamer UK

Co Author(s): :    N. Habib   H. Buckhurst   N. Mandour   C. Purslow   P. Buckhurst        

Abstract Details

Purpose:

Correcting corneal astigmatism with a toric IOL requires accurate alignment of the lens with the steepest corneal meridian. This is reliant upon the accurate assessment of the steepest corneal meridian. Rotation or misalignment of the IOL from the required position will reduce the effective correction. The study aims to investigate the repeatability of keratometry axis determination and to model its effect on a toric IOL correction.

Setting:

Plymouth University, Peninsular Allied Health Centre, UK and the Royal Eye Infirmary, Plymouth, UK

Methods:

A prospective interventional study recruited 79 participants (44 females, 35 males, aged 75.11 ± 9.71) with corneal astigmatism between 1.00-3.00DC. All subjects underwent routine cataract surgery with a 2.8mm clear corneal incision. Scheimpflug tomography, topography and autokeratometry were conducted pre-operatively and at 3-6 months post-operatively. Vector analysis was used to predict the axis shift and then compared to the actual postoperative keratometry readings (AK) to the predicted keratometry readings (PK) and manifest refraction (MR) results. Additionally the instruments axis readings were compared to the MR axis readings to determine the level of disagreement and loss of effective correction.

Results:

The median residual astigmatism predicted when comparing PK and AK for Autorefractor, Scheimpflug and Topographer was 1.53D (IQR 1.00, 2.18), 1.97D (IQR 1.26, 2.46) and 0.55D (IQR 0.40, 0.68) respectively. When comparing the PK to MR the median residual astigmatism for the same instruments was 0.78D (IQR 0.63, 1.98), 0.63D (IQR 0.37, 1.08) and 1.98D (IQR 1.32, 2.63). The discrepancy in MR axis readings ranged from 7.7- 14.9 (Loss of effective correction 26 – 57%).

Conclusions:

The discrepancy between keratometry axis determination and that from MR indicated a resultant significant error with toric IOL placement. Repeated measures and comparison of instruments axis readings are needed to achieve a more accurate assessment of corneal axis. This indicates that the source of post-operative astigmatism axis error needs to be explored in further detail.

Financial Disclosure:

NONE

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