Retinal nerve fiber layer and physiological central corneal thickness

Purpose: To determine the relationship between central corneal thickness and the measurement of retinal nerve fiber layer thickness around the optic nerve head using a confocal scanning laser polarimeter such as the Nerve Fiber Analyzer (GDx). Methods: Forty-four eyes were recruited for this study. Each patient had a normal visual field and a healthy optic nerve head, which was assessed by slit-lamp biomicroscopy with a 90-diopter lens and by a scanning laser ophthalmoscope (Heidelberg Retina Tomograph). Using the GDx, retinal nerve fiber layer thickness was calculated from 1.75 disc diameters together with some standard GDx parameters, including the number, symmetry, superior ratio, inferior ratio, maximum modulation, and ellipse modulation. Corneal thickness was measured with the DGH-1000 ultrasonic pachymeter. Descriptive analysis was used and Pearson's r coefficient of correlation was calculated. Results: Corneal thickness was not significantly correlated to retinal nerve fiber layer thickness, but it was significantly (P < 0.05) correlated to the other GDx parameters. Conclusion: From these data, peripapillary retinal nerve fiber layer thickness is shown not to be significantly correlated to the corneal thickness, even if for the standard GDx parameters a significant correlation was found.