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Central corneal thickness and correlation to optic disc size: a potential link for susceptibility to glaucoma

¹ Wilmer Ophthalmological Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
² Department of Medicine, University of California, San Francisco, California, USA
³ Ophthalmology Research Center, Shahid Beheshti Medical University, Tehran, Iran

Correspondence to:
Correspondence to:
Dr C F Parsa
Wilmer Ophthalmological Institute, Wilmer 233, Johns Hopkins Hospital, 600 North Wolfe Street, Baltimore, MD 21287-9028, USA; cparsa{at}jhmi.edu

ABSTRACT
Aims: To evaluate a possible relationship between central corneal thickness (CCT) and optic disc area in patients with primary open-angle glaucoma (POAG).

Methods: Patients with POAG underwent eye examination, optic disc imaging with the Heidelberg Retina Tomograph II (HRT II) and ultrasound corneal pachymetry. Exclusion criteria were prior ocular surgery and low-quality HRT II images (HRT standard deviation (SD) >50). Pearson’s correlation coefficients were calculated to assess the associations between CCT and optic disc area.

Results: 212 eyes of 137 patients with POAG were examined. In all, 66 (48%) subjects were women, 104 (76%) were Caucasian, 26 (19%) African-American and 7 (5%) other races. 72 eyes remained after excluding those with prior intraocular surgery and low-quality HRT II images. In a univariate analysis of this group, CCT was inversely correlated with optic disc surface area (Pearson’s correlation coefficient r = –0.284, p = 0.036, n = 72). Mean (SD) disc area was 2 (0.53) mm² (n = 160). Caucasians had significantly smaller discs (p<0.001) than other races (Caucasian 1.9 (0.47) mm² (n = 119), African-Americans 2.4 (0.54) mm² (n = 31), other races 2.3 (0.45) mm² (n = 10)).

Conclusion: CCT is inversely correlated to optic disc area. Although thicker corneas have been recognised to cause slight overestimation of true intraocular pressure (IOP), they may also indicate the presence of a substantially smaller, and thus more robust, optic nerve head. People with thinner corneas which slightly underestimate the true IOP may also have larger and more deformable optic discs.

Abbreviations: CCT, central corneal thickness; POAG, primary open-angle glaucoma; HRT II, Heidelberg Retina Tomograph II

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