Comparison of central and peripheral corneal thicknesses between normal subjects and patients with primary open angle glaucoma, normal tension glaucoma and pseudoexfoliation glaucoma

BACKGROUND: While many comparative data are available about central corneal thickness in different types of open angle glaucoma, peripheral corneal thickness has been much less investigated up to now. Thus, the aim of this study was to compare the central and peripheral corneal thicknesses in patients with primary open angle glaucoma (POAG), normal tension glaucoma (NTG) and pseudoexfoliation glaucoma (PEXG) to values of normal subjects. PATIENTS: 104 patients with POAG, 20 patients with NTG, 23 patients with PEXG and 127 normal subjects were investigated with the Orbscan II. The central corneal thickness and the peripheral corneal thickness at 3 mm distance from the centre were determined in 4 quadrants. The acoustic equivalent factor of 0.92 was not used. Patients with eye diseases, patients who had undergone eye surgery or wearers of contact lenses were excluded. Differences were analysed with the Bonferroni-adjusted Mann-Whitney U Test for statistical significance. RESULTS: The median central corneal thickness in POAG was 600 +/- 35 microm, in NTG 577 +/- 31 microm, in PEXG 603 +/- 25 microm and in the control group 606 +/- 38 microm. The difference between NTG and the control group was statistically significant (p = 0.01). Superiorly the peripheral corneal thickness was lower in POAG (670 +/- 47 microm) and NTG (639 +/- 37 microm) compared to the control group (686 +/- 46 microm). Nasally the peripheral corneal thickness was lower in POAG (656 +/- 48 microm), NTG (658 +/- 55 microm) and PEXG (642 +/- 47 microm) compared to the control group (677 +/- 46 microm). Temporally and inferiorly there were only small differences compared to the control group. The differences in peripheral corneal thickness were not statistically significant. DISCUSSION: In accord with literature data the central corneal thickness was lower in patients with normal tension glaucoma compared to normal subjects. Superiorly and nasally the peripheral corneal thickness was lower in patients with open angle glaucoma than in normal subjects which was, however, not statistically significant. To what extent these characteristics of the corneal architecture are relevant for the pathogenesis of open angle glaucomas has to be clarified in further larger trials.