[Impact of prostaglandin-F(2alpha)-analogues and carbonic anhydrase inhibitors on central corneal thickness -- a cross-sectional study on 403 eyes].

BACKGROUND

Histological changes of, in particular, collagen and extracellular matrix after administration of topical prostaglandin F(2alpha)(PGF (2alpha)) analogues have been reported. In view of this observation, we investigated the influence of PGF(2alpha) analogues on the central corneal thickness.

PATIENTS AND

METHODS

In a non-randomized, controlled, cross-sectional study, 403 eyes from 208 consecutive patients were examined: 149 eyes (normals/controls) and 79 with ocular hypertension (OHT), 119 eyes with primary open angle glaucoma (POAG) and 56 eyes with normal tension glaucoma (NTG). One experienced ophthalmologist measured the central corneal thickness (CCT) using ultrasound pachymetry (Tomey AL-2000, sequence of 5 measurements with an SD < 3 microm). The central corneal power was measured with the Zeiss keratometer. Depending on the topical treatment, the patients were classified into 4 groups: A) PGF(2alpha) analogues (n = 78), B) carbonic anhydrase inhibitors (n = 26), C) combination of PGF (2)(alpha) analogues and carbonic anhydrase inhibitors (n = 41), D) none of these drugs (n = 258). T tests and multiple linear regression analyses were used for statistical analysis.

RESULTS

CCT was decreased significantly (p < 0.01 each) in eyes treated with PGF(2alpha) analogues (group A: 529 +/- 34 microM), in comparison with the untreated and non-glaucomatous eyes (part of group D: 542 +/- 35 microM, n = 148), untreated glaucomatous/OHT eyes (part of group D: 563 +/- 37 microM, n = 110), eyes treated with carbonic anhydrase inhibitors (group B: 561 +/- 32 microm) and eyes with a topical application of both PGF (2)(alpha) analogues and carbonic anhydrase inhibitors (group C: 555 +/- 48 microM. No correlation was found between CCT and diagnosis (OHT, POAG, NTG, control), gender, central corneal power, and intraocular pressure in a multivariate analysis.

CONCLUSIONS

The present findings suggest that the topical application of prostaglandin F(2alpha) analogues onto the cornea reduces the central corneal thickness significantly. These changes might be attributed to effects of PGF(2alpha) analogues on the extracellular matrix of the corneal stroma via upregulation of matrix metalloproteinases. In clinical practice, corneal thinning under local PGF (2)(alpha) analogue treatment could result in underestimation of intraocular pressure levels as measured by applanation tonometry.