Lenticular astigmatism in tilted disc syndrome

Abstract

Purpose To evaluate whether an abnormal optic disc shape in patients with tilted disc syndrome (TDS) is associated with an abnormal configuration of the crystalline lens measured as lenticular astigmatism. Setting Department of Ophthalmology, Inönü University Medical Faculty, Turgut Özal Medical Center, Malatya, Turkey. Methods This cross-sectional masked case-control study comprised 32 eyes of 32 patients with established TDS (13 men, 19 women; mean age 21.31 years ± 7.05 [SD]) and 20 age- and sex-matched healthy control subjects (8 men, 12 women; mean age 22.65 ± 7.11 years) with a comparable amount of myopic astigmatism (spherical equivalent) without TDS. The optic disc was morphometrically analyzed by planimetric evaluation of optic disc photographs. The total refractive and keratometric corneal astigmatism was obtained, and lenticular astigmatism was calculated by vector analysis. The Mann-Whitney U test was used for statistical analysis; 1 eye of each patient was evaluated in both groups. A P value less than 0.05 was considered statistically significant. Results The mean spherical equivalent refraction was comparable in TDS patients (−4.73 ± 1.12 diopters [D]) and controls (−4.28 ± 1.29 D) ( P = .210). The mean total astigmatism was higher in TDS patients (−2.96 ± 1.04 D) than in the controls (−2.51 ± 1.09 D), but the difference was not significant ( P = .151). The mean corneal astigmatism was comparable in TDS patients (−2.07 ± 0.83 D) and controls (−2.28 ± 0.87 D) ( P = .454), but the calculated mean lenticular astigmatism was significantly higher in TDS patients (−1.31 ± 0.98 D and −0.20 ± 0.35 D, respectively) ( P < .001). Twenty-nine of 32 TDS patients (90.6%) had lenticular astigmatism; in 16 (50%), it was greater than −1.00 D. Lenticular astigmatism was present in 7 controls (35%); in 2 (10%), it was greater than −1.00 D. The mean keratometry was significantly higher in TDS patients (43.84 ± 1.06 D) than in the controls (42.75 ± 1.45 D) ( P = .011). Conclusions Clinically significant lenticular astigmatism was present in TDS patients. If an abnormal optic disc shape is found on ophthalmoscopy, lenticular astigmatism as well as corneal astigmatism should be carefully evaluated to prevent an unsatisfactory refractive outcome, especially in refractive surgery candidates.