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Surgically-induced astigmatism of single plane clear corneal, biplanar clear corneal and scleral incisions in cataract surgery

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Session Details

Session Title: Cataract Surgery Outcomes / Femto

Session Date/Time: Monday 15/09/2014 | 08:00-10:30

Paper Time: 09:51

Venue: Auditorium

First Author: : N.Reus THE NETHERLANDS

Co Author(s): :    C. van der Sommen   S. Klijn   A. Sicam        

Abstract Details

Purpose:

To compare surgically induced astigmatism (SIA) of a single plane clear corneal incision (SPCCI) with that of a biplanar (grooved) clear corneal incision (BPCCI) and a scleral incision in cataract surgery.

Setting:

The Rotterdam Eye Hospital, Rotterdam, the Netherlands.

Methods:

Prospective observational cohort study. Automated keratometry was performed preoperatively and 4 weeks postoperatively in 66 eyes of 66 patients undergoing cataract surgery. Eyes with preoperative corneal astigmatism > 1.5 D were excluded. Thirty-three eyes received a scleral incision, twenty-two eyes received SPCCI, and 11 eyes received BPCCI. All incisions had a length of 2.2 mm and were placed in the 100 degrees meridian. A single surgeon (NJR) performed all surgeries. Keratometry was done with the Lenstar LS-900 (Haag-Streit, Koeniz, Switzerland) and included the flattest and steepest corneal radii and corresponding meridians. Astigmatic magnitudes were calculated with a keratometric index of 1.3375. For each measurement, the orthogonal components C0 and C45 on a Cartesian coordinate system were calculated. Individual SIA was then calculated as ΔC0 and ΔC45 (Δ indicating the difference between the preoperative and postoperative value). For each group, the distributions of ΔC0 and ΔC45 were tested for normality using the Kolmogorov-Smirnov test. Differences between groups were tested for statistical significance using Hotelling trace multivariate analysis of variance. P-values < 0.05 were considered statistically significant. In order to allow for clinical interpretation, averages and standard deviations (SD) of ΔC0 and ΔC45 were converted back to diopter (D) notation.

Results:

The distributions of ΔC0 and ΔC45 within each group were not significantly different from a normal distribution (P > 0.05). SIA was on average 0.40 D (SD, 0.37) for SPCCI, 0.20 D (SD, 0.23) for BPCCI, and 0.15 D (SD, 0.36) for scleral incision. The differences in SIA between the various types of incision were all statistically significant (SPCCI vs. BPCCI P < 0.01; SPCCI vs. scleral P < 0.01; BPCCI vs. scleral P = 0.04).

Conclusions:

We found that corneal as well as scleral 2.2-mm superior-located incisions induce (some amount of) SIA. Our results support findings by other researchers that clear corneal incisions induce more SIA than scleral ones. The variability in SIA is similar between the various incision types and may be of clinical significance, especially when implanting toric intraocular lenses. With regard to clear corneal incisions, our results show that biplanar (grooved) incisions have a statistically significantly lower SIA than single-plane incisions. This might be due to a difference in architectural stability.

Financial Interest:

NONE

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