Intrasubject Difference in CCT among POAG versus Normal Individuals

Purpose To evaluate intrasubject asymmetry in central corneal thickness (CCT) among patients with primary open-angle glaucoma (POAG) as compared with that of normal subjects and to determine whether the eye with thinner cornea has more severe glaucomatous visual field damage. Methods In this case-control study, CCT of both eyes was measured using an ultrasonic pachymeter (UP-1000; Nidek Technologies, Gamagori, Japan) among POAG patients and normal subjects. The intrasubject difference in CCT was calculated and compared between the study groups; correlations between CCT and intraocular pressure (IOP), vertical cup–to–disc ratio (VCDR), and visual field defects were also evaluated. Results A total of 62 patients with bilateral POAG and 56 normal subjects were included. There was no significant difference between the study groups in terms of age, sex, and ocular parameters except for visual acuity, IOP, and VCDR. The POAG patients demonstrated significantly greater intrasubject asymmetry in CCT (8 ± 7 μm vs. 5 ± 3 μm; p = 0.041) and a higher prevalence of significant (>10 μm) intrasubject CCT difference (30.6 vs. 5.4%; p < 0.001) as compared with normal subjects. Although each higher level of glaucomatous damage was associated with 4-μm thinner CCT, the correlation was not statistically significant (95% confidence interval, −8 to 1 μm; p = 0.117; GEE analysis). No significant correlation was observed between CCT and IOP or VCDR (p = 0.302 and 0.137, respectively). Conclusions Patients with POAG demonstrate a larger amount of intrasubject difference in CCT as compared with normal subjects.