Correlation Between Corneal Thickness and Visual Field Indexes in Glaucoma Patients

Abstract

Abstract: : Purpose:To verify whether there was a significant correlation between central corneal thickness (CCT) and visual field indices. Methods:86 eyes of 43 patients with primary open angle glaucoma (POAG) were consecutively recruited.Patients were classified as glaucomatous based on visual field and optic nerve head (ONH) damage. Each patient underwent a Goldmann applanation tonometry, a Humphrey perimetry, (program 30–2, SITA Standard) and measurement of CCT with ultrasonic contact pachimetry. Then the patients with a visual field damage were splitted in three subgroups depending on the central corneal thickness: group I from 400 µm to 515 µm, group II from 515 µm to 550 µm and group III from 550 µm to 650 µm. The data were analyzed with the T–test and linear regression. Results:In the entire group CCT was 540.07 µm ± 47.84 (mean ± standard deviation);mean deviation (MD) was –6.43 dB ± 7.32; pattern standard deviation ( PSD) 5.25 ± 3.75; intraocular pressure (IOP)17.5 ± 3.78 mmHg . Then the patients were divided in three subgroups mean and standard deviation were calculated as above. In group I CCT was 482 µm ± 41.2; MD was –14.23 dB ± 9.13; PSD was 7.41 ± 385; IOP was 17.5 mmHg ± 5.03. In group II CCT was 528.75 µm ± 8.24; MD was –8.51 dB ± 5.45; PSD was 7.46 ± 3.91; IOP was 20.31 mmHg ± 3.87 for. In group III CCT was 575.31 µm ± 27.04; MD was –5.19 dB ± 1.79; PSD was 4.95 ± 2.54; IOP was 17.68 mmHg ± 3.84. A significant difference was found among the three subgroups for MD and between group III and the other groups for PSD.Linear regression analysis showed a significant correlation between CCT and PSD and a tendency between CCT and IOP. Conclusions:Our data showed that patients with a thinner cornea had a worse MD and PSD. Since a thinner central cornea thickness causes an underestimation of the true intraocular pressure there may be a delay in the diagnosis of POAG or an inadequate target pressure and therefore a progression of the glaucoma damage despite low IOP applanation values .

Keywords: intraocular pressure • visual fields • perimetry