Decreased Corneal Sensitivity in Dry Eye Patients

Abstract

Abstract: : Purpose: To explore changes in corneal sensitivity developed by dry eye patients and the relationship between sensibility and severity of the dry eye disease. Methods: Experiments were performed in 44 dry eye patients and 42 healthy individuals. Corneal sensitivity was measured using the Belmonte non–contact gas esthesiometer. Mechanical (air jets at flow rate from 0 to 200 ml/min), thermal (air at subthreshold flow rates reaching the cornea at temperatures between 40º to 60°C), and chemical stimuli (air containing 0 to 50% CO₂ at subthreshold flow rate) were applied to the center of the cornea to determine the sensitivity threshold for each stimulus modality. The clinical state of the ocular surface was additionally explored measuring the fluorescein tear break–up time, the degree of corneal staining with fluorescein and Lissamine green, and tear production with the Schirmer test. Results: Both in control and dry eye patients, corneal threshold for mechanical chemical and thermal stimulation increased with age. Moreover, threshold for the three modalities of stimuli were significantly higher in dry eye patients in comparison with control subjects. In both groups, individual values of mechanical, chemical and thermal thresholds were significantly correlated. Also, high threshold values in dry eye patients were correlated with the intensity of fluorescein and Lissamine green corneal staining but not with the values of Schirmer’s test. Conclusions: Dry eye patients exhibit corneal hypoaesthesia to mechanical, thermal, and chemical stimulation that appears to be related to the damage of corneal sensory innervation.

Keywords: innervation: sensation • cornea: tears/tear film/dry eye • cornea: clinical science