Central corneal thickness, tonometry, and ocular dimensions in glaucoma and ocular hypertension

Purpose: To assess possible correlations between central corneal thickness, tonometry, and ocular dimensions. Patients and Methods: One hundred seventeen eyes of 117 patients who were n ot taking any intraocular pressure-lowering medications were studied prospe ctively. Forty-one patients had ocular hypertension; 13 patients had primar y open-angle glaucoma; and 10 patients had normal-pressure glaucoma. Twenty -three healthy eyes were included. Thirty glaucoma suspects (10 patients mo nitored for possible normal-pressure glaucoma and 20 patients with intermit tent ocular hypertension) were included for correlation analysis. Tonometry was performed with Goldmann applanation and pneumotonometry. and central c orneal thickness, anterior chamber depth, lens thickness, and axial length were measured ultrasonically. Results: Central corneal thickness was lowest in eyes with normal-pressure glaucoma (538 +/- 51 mum), highest in eyes with ocular hypertension (570 +/ - 32 mum), and intermediate and similar in eyes with primary open-angle gla ucoma and healthy eyes (547 +/- 34 mum and 554 +/- 32 mum, respectively). T hese differences were significant (P = 0.028). Goldmann applanation tonomet ry and central corneal thickness were weakly correlated (r = 0.12, P = 0.20 5), with a 0.2-mm Hg change per 10-mum variation in central corneal thickne ss. Pneumotonometry measurements were more strongly correlated with central corneal thickness (r = 0.21, P < 0.05). Lens thickness was strongly correl ated with age (r = 0.57, P < 0.001). Anterior chamber depth was negatively correlated with lens thickness and age (r = -0.29, P < 0.005 and r = -0.25, P < 0.01). Axial length was correlated with anterior chamber depth and age (r = 0.5, P < .001 and r = -0.19, P < 0.05). Conclusion: Eyes diagnosed as having ocular hypertension have thicker corne as and eyes labeled as having normal-pressure glaucoma have thinner corneas , when compared with healthy eyes or eyes with primary open-angle glaucoma. The effect of central corneal thickness on Goldmann applanation tonometry accuracy appears to he small and usually not clinically relevant. When corn eal thickness is markedly different from normal, the clinician may need to factor this into diagnosis and management.