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Is surgically-induced astigmatism predictable following a 3.00 mm clear corneal cataract incision?

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Session Details

Session Title: Cataract Surgery Outcomes

Session Date/Time: Tuesday 16/09/2014 | 08:00-10:30

Paper Time: 08:12

Venue: Capital Hall A

First Author: : H.Ali UK

Co Author(s): :    S. Perera   J. Hoffman           

Abstract Details


It is generally assumed that a clear corneal 3.00mm section induces astigmatism of about 0.5D and most commercially available toric lens power calculators use this figure for their calculations. This study is an attempt to look at the validity of this assumption and to analyse the incidence of Surgically Induced Astigmatism (SIA) identified following long-term follow up.


Hospital Practice


30 patients who had cataract surgery by the same surgeon using the same technique with a clear corneal section enlarged to 3.00mm for lens insertion were included in the study. The keratometric readings in the operated eye were repeated at least one year later. Automated keratometry readings taken from the IOL master at the pre-operative assessment and the post-operative assessment were used to calculate the SIA using the vector analysis method.


The mean time between cataract surgery and keratometric measurements was 4 years (range 1-9 yrs). The pre-operative and post- operative mean K’s were 43.33D and 43.25D respectively. The SIA ranged from 0.11-1.03D (SD 0.32). Twenty percent of patients had a SIA between 0- 0.25D, 40% between 0.26-0.50D, 7% between 0.51-0.75D and 33% between 0.76-1.00D.


This study, with long-term follow up results, show that the SIA for the same surgeon using the same technique is highly variable and unpredictable. Using a specific value for SIA when calculating the lens power for implanting toric lenses may not give the accuracy we desire.

Financial Interest:


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