CENTRAL CORNEAL THICKNESS IN LOW-TENSION GLAUCOMAS
I.M. Velten, M. Wisse, A. Jünemann
Background: It is known that applanation intraocular pressure (IOP) depends on central corneal thickness and on corneal rigidity. Several studies in the past have shown that in patients with ocular hypertension central corneal thickness is statistically increased compared with normals and primary and secondary open angle glaucomas. It was the purpose of the present study to compare central corneal thickness in a larger group of patients with low-tension glaucomas, open-angle glaucomas with a maximum IOP above 21 mmHg and normals.
Methods: The central corneal thickness was determined in 134 subjects (57 normals, 7 primary and secondary open-angle glaucomas with a maximum IOP above 21 mmHg, and 30 low-tension glaucomas, AL 1000 Pachymeter (Tomey), 10 measurements per eye). The results of the three study groups were compared (only one eye per subject included, statistics: unpaired t-test). The age of the participants did not differ significantly among the three groups. In all participants, refractive status, keratometry, and actual IOP were additionally studied.
Results: The central corneal thickness of eyes with low-tensions glaucomas (542 ± 32 µm) was significantly lower (p < 0.05) than that of normal controls (561 ± 34 µm) or that of eyes with primary and secondary open-angle glaucomas with a maximum intraocular above 21 mmHg (559 ±28 µm). The latter two groups did not differ significantly for central corneal thickness. There was no statistically significant difference for refractive status and keratometry among the three groups.
Conclusions: Decreased central corneal thickness can lead to artificially low estimations of applanation IOP. This should be taken into account in differential diagnosis of low-tension glaucomas.
Supported by "Deutsche Forschungsgemeinschaft, Sonderforschungsbereich Glaukome (SFB 539) ".
Augenklinik mit Polinik der Universität Erlangen-Nürnberg, Schwabachanlage 6, D-91054 Erlangen