Does the Stage of Keratoconus Affect Optical Coherence Tomography Measurements?

Purpose: To employ optical coherence tomography (OCT) to examine the relationship of changes in the retinal nerve fiber layer (RNFL) and macular thickness as well as ganglion cell (GC) parameters with the stage of keratoconus (KC), and to compare these changes with a control group. Methods: A total of 84 eyes of 68 patients with KC and 29 eyes of 29 normal age-matched subjects underwent RNFL, macular thickness measurements, and ganglion cell analysis using Cirrus high-definition (HD) OCT. Patients with KC were classified according to the Amsler-Krumeich Classification. The measurements were analyzed in all quadrants for each KC stage and compared with control subjects. Results: All RNFL, macular thickness, and ganglion cell parameters varied significantly among the groups (all p<0.001, analysis of variance). An increase in the stage of KC was correlated with decreased RNFL thickness, macular thickness, and ganglion cell parameters. Conclusions: RNFL, macular thicknesses, and ganglion cell parameters in all KC stages were lower than those in the control group. The RNFL, macular thickness, and ganglion cell parameters of the Grade 1 KC group were most similar to those of the control group. The severity of irregular astigmatism at the same stages of KC had a significant effect on OCT measurements. It may therefore be beneficial to know the amount of change/deviation in OCT measurements in keratoconus patients and to report which parameters exceed the standards so that OCT can be used to correlate the stage of keratoconus with the extent of the ocular disorder.