New nonlinear multivariable model shows the relationship between central corneal thickness and HRTII topographic parameters in glaucoma patients

Purpose: In this paper a new nonlinear multivariable regression method is presented in order to investigate the relationship between the central corneal thickness (CCT) and the Heidelberg Retina Tomograph (HRTII) optic nerve head (ONH) topographic measurements, in patients with established glaucoma. Methods: Forty nine eyes of 49 patients with glaucoma were included in this study. Inclusion criteria were patients with (a) HRT II ONH imaging of good quality (SD < 30 mu m), (b) reliable Humphrey visual field tests (30-2 program), and (c) bilateral CCT measurements with ultrasonic contact pachymetry. Patients were classified as glaucomatous based on visual field and/or ONH damage. The relationship between CCT and topographic parameters was analyzed by using the new nonlinear multivariable regression model. Results: In the entire group, CCT was 549.78 +/- 33.08 mu m (range: 484-636 mu m); intraocular pressure (IOP) was 16.4 v 2.67 mmHg (range: 11-23 mmHg); MD was -3.80 +/- 4.97 dB (range: 4.04 -[-20.4] dB); refraction was -0.78 +/- 2.46 D (range: -6.0 D to + 3.0 D). The new nonlinear multivariable regression model we used indicated that CCT was significantly related (R-2 = 0.227, p < 0.01) with rim volume nasally and type of diagnosis. Conclusions: By using the new nonlinear multivariable regression model, in patients with established glaucoma, our data showed that there is a statistically signifi cant correlation between CCT and HRTII ONH structural measurements, in glaucoma patients.