Influence of lens removal on total astigmatism

Poster Details

First Author: H.Tamura JAPAN

Co Author(s):    Y. Sano              

Abstract Details

Purpose:

To investigate the rate of corneal astigmatism and internal astigmatism (in particular, lenticular astigmatism) in preoperative cataract patients by using the KR-1 Wave-Front Analyzer and to examine the control of astigmatism to improve postoperative visual function.

Setting:

Two hundred and seventy eyes of 154 patients (98 eyes of 57 men and 172 eyes of 97 women; mean age, 73 years) who underwent cataract surgery in the Tamura Ophthalmologic Clinic between March 29, 2011 and December 6, 2011.

Methods:

Ocular aberrations measured using a Hartmann-Shack Wavefront Sensor and corneal aberrations measured using a corneal topographer were examined using the KR-1 Wave-Front Analyzer (Topcon Corporation, Tokyo, Japan) before and after surgery. Anterior corneal astigmatism was determined using the corneal topographer, and internal astigmatism was calculated by subtracting corneal aberrations from ocular aberrations. Internal astigmatism mainly consists of lenticular astigmatism but also includes posterior corneal astigmatism.

Results:

Measurements could be obtained in 106 of the 270 eyes examined, and these measurements were analyzed. The results were as follows: - Forty-seven percent of patients whose anterior corneal surface had against-the-rule astigmatism also had against-the-rule internal astigmatism; this was the most common case.?? - The absolute cylinder before and after surgery was 2.00 and 1.33, respectively; the difference was statistically significant ?????????(P< 0.01? -No patient with with-the-rule anterior corneal astigmatism had with-the-rule internal astigmatism. -Forty-one percent of patients had with-the-rule anterior corneal astigmatism and against-the-rule internal astigmatism. - The absolute cylinder before and after surgery was 0.94 and 0.99, respectively; the difference was not statistically significant. - Twelve percent of patients had against-the-rule anterior corneal astigmatism and with-the-rule internal astigmatism. - The absolute cylinder before and after surgery was 1.59 and 1.70, respectively; the difference was not statistically significant. - The absolute cylinder when a toric lens was used before and after surgery was 2.30 and 0.97, respectively; the difference was statistically significant.(p<0.01)

Conclusions:

In this study, 47% of patients showed parallel forms of corneal astigmatism and internal astigmatism (both being against the rule). This result suggests that lenticular astigmatism is eliminated by lens removal, which may lead to weakened total astigmatism in some patients. Our results showed that the absolute cylinder before and after surgery was 2.00 and 1.33, respectively, and the difference was statistically significant (P < 0.01). Fifty-three percent of patients showed astigmatism that was offset by orthogonality between anterior corneal astigmatism and internal astigmatism. This result suggests that if lenticular astigmatism that had offset anterior corneal astigmatism is eliminated by lens removal during cataract surgery, total astigmatism might become stronger after the surgery in some patients. This study showed no statistically significant difference in the absolute cylinder before and after surgery. However, it should be considered that our results might be influenced by corneoscleral incision-induced astigmatism. The absolute cylinder in 10 cases in which a toric lens was used was 2.30 and 0.97 before and after surgery, respectively; this difference was statistically significant.(p<0.01) We think that in cases of less preoperative total astigmatism and strong anterior corneal astigmatism, the preferred treatment for aggressively reducing astigmatism is the use of a toric intraocular lens. FINANCIAL DISCLOSURE?: No