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Abstract #15344 Published in IGR 1-3
Central corneal thickness in low-tension glaucoma
Emara BY; Tingey DP; Probst LE; Motolko MACanadian Journal of Ophthalmology 1999; 34: 19-24
BACKGROUND: It is possible that the intraocular pressure (IOP) is underestimated in eyes whose central cornea is thinner than normal. The objective of this study was to determine and establish the significance of central corneal thickness in patients with low-tension (normal-tension) glaucoma compared with those with chronic open-angle glaucoma (COAG) or ocular hypertension, and healthy eyes. METHODS: The study was carried out from February 1998 to May 1999. Central corneal thickness was measured by ultrasonic pachymetry and IOP was measured by Goldmann applanation tonometry in 25 patients with low-tension glaucoma (untreated IOP of less than 21 mmHg with evidence of optic nerve head damage and corresponding visual field loss on automated perimetry), 80 patients with COAT (untreated IOP of 21 mmHg or greater with evidence of optic nerve head damage and corresponding visual field loss on automated perimetry), 16 patients with ocular hypertension (untreated IOP of 21 mmHg or greater, with normal optic nerve head and no history of glaucoma or elevated IOP, and normal visual field on automated perimetry), and 50 control subjects (untreated IOP of less than 21 mmHg with normal optic nerve head and no history of glaucoma or elevated IOP). Analysis with Pearson's product-moment correlation was performed to determine the correlation of IOP and central corneal thickness, and one-way analysis of variance was used to compare corneal thickness between groups. RESULTS: The central cornea was significantly thinner in the low-tension glaucoma group (mean 513.2 μm (SD 26.1 μm)) than the COAG group (mean 548.2 μm (SD 35.0 μm)) and the control group (mean 556.7 μm (SD 35.9 μm)) (p < 0.001. No significant difference in corneal thickness was found between the COAG and control groups. The ocular hypertension group had significantly thicker corneas (mean 597.5 μm (SD 23.6 μm)) than the other three groups (p < 0.001). INTERPRETATION: Patients with low-tension glaucoma may have thinner corneas than patients with COAG and healthy subjects. This results in underestimation of their IOP. Corneal thickness should be taken into account when managing these patients, to avoid undertreatment.
Dr. L.E. Probst, Department of Ophthalmology, St Joseph's Health Centre, 268 Grosvenor Street, London ON N6A 4V2; Canada
Classification:
2.2 Cornea (Part of: 2 Anatomical structures in glaucoma)
6.1 Intraocular pressure measurement; factors affecting IOP (Part of: 6 Clinical examination methods)
9.2.4 Normal pressure glaucoma (Part of: 9 Clinical forms of glaucomas > 9.2 Primary open angle glaucomas)
