Establishing the normal range of corneal sensitivity in an Indian Population using the Cochet–Bonnet esthesiometer

Abstract

Background: The human cornea is the most densely innervated tissue, and the corneal sensitivity is a measure of its function and an indicator of the integrity of the protective mechanism. Corneal sensitivity plays a vital role in the protection and maintenance of corneal health and is known to vary with race, age, region, climate, environment, and the time of the day. The study was aimed to quantify and establish the range of corneal sensations in different age groups in an Indian population using the Cochet–Bonnet Esthesiometer (CBE). Materials and Methods: This was a cross-sectional study done at a tertiary care center in South India, between January and April 2018. One hundred and fifty patients (30 patients stratified by age into five groups) were enrolled after informed consent. The corneal sensations were measured using CBE by a single examiner in a specified period of a day over five regions and the data analyzed. Results: The average measured corneal sensitivity was 58.36 (21–30 years), 57.96 (31–40 years), 56.43 (41–50 years), 56.40 (51–60 years), and 54.84 (>60 years) mm, respectively. The frequency of having maximal measurable sensations (60 mm) in all the tested regions dropped with increasing age from 46.67% to 16.67%. All regions showed a sensitivity drop with an increase in age, the maximum in the nasal quadrant and the least drop in the central region. No statistically significant difference in the corneal sensitivity was found between the genders. Conclusions: An inverse linear correlation between the corneal sensitivity and age was evident. The central and the superior regions are the most and least sensitive regions of the cornea, respectively, in our study population. The varied pattern of change in corneal sensations in different populations highlights the importance of establishing normal ranges of corneal sensitivity in patients from different ethnic and geographical backgrounds.