Visual Field and Optic Disc Progression in Glaucoma. The Role of Central Corneal Thickness.

Abstract

Abstract: : Purpose: To determine whether central corneal thickness is a significant predictor of visual field and optic disc progression in open–angle glaucoma. Methods: Our sample contained 82 eyes of 43 patients with a mean baseline age of 55.9 ± 9.9 years who were followed for a mean of 9.8 ± 0.8 years in a prospective cohort study on the relationship between functional and structural progression. Visual field and optic disc examinations were performed every six months with the full threshold 30–2 programme of the Humphrey Field Analyser and the Heidelberg Retina Tomograph respectively. Central corneal thickness (CCT) measurements were obtained by ultrasound pachymetry. Progression was determined using a trend analysis called "evidence of progression" (EOP) in which ordinal scores based on the significance of regression coefficients of threshold and rim area deviations respectively over time are summed over sectors, yielding values between 0 (no evidence of progression) to 16 (very high evidence of progression). Visual field progression was also determined with an event analysis based on total and pattern deviation probability maps using criteria of 2, 3 and 4 "black triangles" over 3 consecutive examinations. Results: There was a weak, but statistically significant inverse correlation between CCT and the EOP field score (Spearman’s r = –0.44; P = 0.001), but not EOP disc score (r = –0.01; P = 0.923). In a multivariate regression analysis, the only independent variable (including a variety of IOP summary measures during the follow–up) even marginally related to the EOP field score was CCT (P = 0.049). In the event–based analyses, the mean CCT in eyes classified as progressing was always less than that of those non–progressing, with a maximum group difference of < 20 µm. These differences were statistically significant only with the least conservative progression criteria. Conclusions: There was a weak, but consistent, trend suggesting that decreasing CCT is related to visual field, but not optic disc, progression. These relationships appeared to be independent of IOP.

Keywords: visual fields • optic disc • clinical (human) or epidemiologic studies: risk factor assessment