Corneal Sensitivity in Tear Dysfunction and its Correlation With Clinical Parameters and Blink Rate

To compare corneal sensitivity in tear dysfunction due to a variety of causes using contact and noncontact esthesiometers and to evaluate correlations between corneal sensitivity, blink rate, and clinical parameters.

Comparative observational case series.

Ten normal and 33 subjects with tear dysfunction (meibomian gland disease [n = 11], aqueous tear deficiency [n = 10]-without (n = 7) and with (n = 3) Sjögren syndrome (SS)-and conjunctivochalasis [n = 12]) were evaluated. Corneal sensitivity was measured with Cochet-Bonnet and air jet esthesiometers and blink rate by electromyography. Eye irritation symptoms, tear meniscus height, tear break-up time (TBUT), and corneal and conjunctival dye staining were measured. Between-group means were compared and correlations calculated.

Compared with control (Cochet-Bonnet 5.45 mm, air esthesiometer 3.62 mg), mean sensory thresholds were significantly higher in aqueous tear deficiency using either Cochet-Bonnet (3.6 mm; P = .003) or air (11.7 mg; P = .046) esthesiometers, but were not significantly different in the other groups. Reduced corneal sensitivity significantly correlated with more rapid TBUT and blink rate and greater irritation and ocular surface dye staining with 1 or both esthesiometers. Mean blink rates were significantly higher in both aqueous tear deficiency and conjunctivochalasis compared with control. Among all subjects, blink rate positively correlated with ocular surface staining and irritation and inversely correlated with TBUT.

Among conditions causing tear dysfunction, reduced corneal sensitivity is associated with greater irritation, tear instability, ocular surface disease, and blink rate. Rapid blinking is associated with worse ocular surface disease and tear stability.