A Correlation Between Ocular Discomfort as Induced by the Controlled Adverse Environment (CAE) and Corneal Sensitivity

Abstract

Abstract: : Purpose: It has been suggested that sensory nerves to the cornea become less sensitive with advancing age and ocular surface disorders. The purpose of this study was to investigate the relationship between corneal sensitivity and the onset of ocular symptoms during exposure to an adverse environment in a dry eye population. Methods: Thirty-six (36) subjects diagnosed with dry eye underwent baseline examinations including a slit-lamp biomicroscopy evaluation, tear film break-up time (TFBUT) measurement, corneal / conjunctival staining assessment, Schirmer’s and corneal sensitivity tests. Corneal sensitivity was determined with a Luneau Cochet Bonnet Aesthiometer (model # 8305). Subjects were then exposed to a Controlled Adverse Environment (CAE) which regulates humidity (<5% RH), temperature (76±6°F), airflow (constant, non-turbulent) and visual tasking (watching a movie) for 90 minutes. Ocular discomfort was recorded using a standardized 0-4 point scale upon entering the CAE and every 5 minutes thereafter. After the CAE exposure, a slit-lamp biomicroscopy, TFBUT and corneal / conjunctival staining were re-evaluated. Results: Subject eyes were grouped as having either Low Corneal Sensitivity (LCS) (defined as ≤ 4), n = 32 (mean = 2.7), or Normal Corneal Sensitivity (NCS) (defined as > 4), n = 40 (mean = 5.75). Mean time to reporting an ocular discomfort score of ≥ 3+ during the CAE exposure was 38.5 minutes in LCS eyes and 22.7 minutes in NCS eyes (p = 0.036). Mean TFBUT was 3.15 seconds in LCS eyes and 4.10 seconds in NCS eyes (p = 0.065). Mean Schirmer’s value was 5.7 mm in LCS eyes and 8.1 mm in NCS eyes (p = 0.058). No notable differences between groups in corneal and conjunctival staining were observed. Conclusions: The data shows that eyes with low corneal sensitivity take longer to become symptomatic than those with normal corneal sensitivity when exposed to an adverse environment.

Keywords: cornea: tears/tear film/dry eye • cornea: clinical science • clinical (human) or epidemiologic studies: tre