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Off or on axis incision: does it really matter?

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Session Details

Session Title: Pseudophakic IOLs: Toric, Multifocal, Accommodative

Session Date/Time: Monday 09/10/2017 | 14:30-16:00

Paper Time: 14:42

Venue: Room 4.1

First Author: : G.Verroiopoulos UK

Co Author(s): :    V. Kit   S. Perera                 

Abstract Details


Cataract incisions can affect the corneal curvature. Some surgeons place their incision on the steeper axis (on axis) in order to reduce the surgically induced astigmatism (SIA). Corneal curvature is shown to change over time. This study aims to clarify if there is any significant long term difference between SIA caused by an on axis incision and SIA caused by an off axis incision.


Prince Charles Eye Unit, Royal Berkshire NHS Foundation Trust, Windsor, UK


117 patients who had cataract surgery by multiple surgeons, had automated corneal keratometry done by IOL Master device both preoperatively and postoperatively 1-8 years later(mean 4 years). All surgeons used a keratome to make a clear corneal 2.2mm incision, which was enlarged to 2.4-2.5mm for lens insertion. If the axis of the main incision had a deviation of 15 degrees or less, compared to the steeper axis, the incision was considered as on axis (29 patients), otherwise it was considered as off axis (88 patients). SIA was calculated using the vector analysis method from the preoperative and postoperative K readings.


The mean SIA in the on axis group was 0.5197D (SD 0.3199) with a range of 0.05-1.11D, while the mean SIA in the off axis group was 0.5281D (SD 0.4106) with range 0-1.99D. Both groups passed the Kolmogorov-Smirnov normality test with p>0.05. The mean difference of 0.008413D in the SIA between the two groups was not significant with p=0.92. The t test also suggested that the difference between the two SDs was not significant with p>0.05.


This study suggests that there is no long term statistically significant difference in SIA between on axis and off axis incisions.

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