Distribution of Posterior Corneal Astigmatism and Aberration before Cataract Surgery in Chinese Patients

Abstract

Purpose : To study the prevalence of posterior corneal astigmatism (PCA) and aberration in Chinese eyes before cataract surgery.

Methods : We conducted a cross-sectional study in Eye and ENT Hospital of Fudan University, Shanghai. In all, we enrolled 1976 eligible eyes of 1976 cataract patients. The astigmatism and aberrations of anterior and posterior cornea were measured by the rotating Scheimpflug System (Pentacam HR, Oculus). Cataract was diagnosed using slit-lamp examination.

Results : The mean age of patients were 61.82±13.67 years old. Mean PCA was 0.28±0.16 (range 0-1.0) D and 87.04% eyes had PCA values <0.5D. WTR astigmatism predominated the anterior cornea astigmatism (43.1%); while ATR astigmatism predominated posterior (85.4%) and total corneal astigmatism (47.2%). We found a shift tendency of WTR to ATR with aging in anterior corneal astigmatism, while PCA remains ATR. A significant positive correlation between the magnitude of anterior and posterior corneal astigmatism (r²=0.089, P<0.001), especially in WTR anterior cornea astigmatism eyes (r²=0.298, P<0.001). Compared with total corneal astigmatism, anterior corneal measurements overestimated WTR astigmatism by a mean of 0.24±0.13 (D), underestimated ATR astigmatism and oblique astigmatism in most eyes. Furthermore, anterior corneal aberrations measurements overestimated the total corneal aberration in most eyes.

Conclusions : 12.96% of eyes had PCA ≥0.5D. The posterior surface remained ATR astigmatism in most cases with aging. Neglecting the posterior cornea would result in overestimation in WTR anterior corneal eyes and underestimation in ATR and oblique anterior corneal eyes. Also, the posterior corneal aberration was also essential in clinics.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

 

A. Distribution of anterior corneal astigmatism in each age group. B. Distribution of posterior corneal astigmatism in each age group. C. Distribution of total corneal astigmatism in each age group.(WTR: with the rule, ATR: against the rule).

 

A and B. Positive linear correlations between ACA and PCA in all eyes and eyes with WTR ACA (r²=0.089,N=1976 and r²=0.298,N=852, respectively). C. Weak negative linear correlations between ACA and PCA in eyes with ATR ACA (r²=0.014,N=719). D. Weak positive linear correlations between ACA and PCA in eyes with oblique ACA (r²=0.074,N=405) (ACA, PCA and TCA: anterior, posterior and total corneal astigmatism, WTR and ATR: with and against the rule).