Corneal Nerve Structure and Function in Patients With Non-Sjogren Dry Eye: Clinical Correlations

PURPOSE. To evaluate the relationship between the in vivo confocal microscopic (IVCM) morphology of subbasal corneal nerves, corneal sensitivity, and clinical parameters in patients with non-Sjogren dry eye disease (NSDD). METHODS. Forty-three patients with NSDD and 14 healthy age-and sex-matched control subjects were included. Each patient underwent an evaluation of ocular surface disease symptoms using the Ocular Surface Disease Index (OSDI); tear film break-up time (TBUT); corneal and conjunctival staining (Oxford scale); the Schirmer test; corneal sensation testing using the Cochet-Bonnet esthesiometer; and corneal subbasal nerve analysis with IVCM. One eye of each subject was included in the study. RESULTS. Mean corneal sensitivity was significantly lower in the NSDD group as compared with the control group (P = 0.014). Corneal subbasal nerves showed significant changes in NSDD patients as compared with normal subjects: lower density (P < 0.001); increased tortuosity (P < 0.001); number of beadings (P < 0.001); and width (P = 0.041). In patients with NSDD, corneal subbasal nerve density was correlated to age (r = -0.352, P = 0.021); the Oxford scale (r = -0.486, P = 0.01); and central corneal sensitivity (r = -0.383, P 0.041). The maximum length of nerve fibers within a frame (MaxL) was correlated to the OSDI (r = -0.265, P = 0.019) and the Oxford scale (r = -0.307, P = 0.039). In multivariate analysis after adjustment for age, corneal subbasal nerve density remained correlated to the Oxford score (P < 0.001). The Oxford score was also correlated to central corneal sensitivity (r = -0.304, P = 0.042). CONCLUSIONS. NSDD patients have both structural and functional alterations of subbasal corneal nerves and these changes are related to the severity of dry eye.