Normal corneal sensitivity and its changes with age in Tehran, Iran.

BACKGROUND: The present study sets out to determine normal corneal sensitivity in five corneal regions and its changes with age in an Iranian population.

METHODS: The corneal sensitivity of the centre of the cornea and at four corneal regions, namely, nasal, inferior, temporal and superior at 2.0 mm from the limbus of the right eye of 596 subjects aged 15 to 81 were measured using a Cochet-Bonnet aesthesiometer. All measurements were performed by the same examiner at 18 degrees centigrade and 35 per cent humidity between 2:00 and 5:00 pm. The subjects were divided into six age groups of 15 to 25 years, 26 to 35, 36 to 45, 46 to 55, 56 to 65 and over 65 years, respectively. Since the measurement outcomes were not continuous, the data was analysed using non-parametric statistics.

RESULTS: The frequency of corneal sensitivity of 60 mm in all corneal regions was decreased with advancing age after 35 years (χ(2) p < 0.001). The strongest correlation between age and corneal sensitivity was for the centre of the cornea (-0.52), followed by nasal (-0.49), temporal (-0.48), inferior (-0.47) and superior (-0.46) regions of the cornea, which had significant negative correlations (p < 0.001). The five different corneal regions showed significant differences of corneal sensitivity (p < 0.001). In different age groups, the difference was seen in the three lower age groups of 1, 2 and 3, while in the three older age groups of 4, 5 and 6, there were no differences in corneal sensitivity among five corneal regions (p > 0.05).

CONCLUSION: Based on the findings of the current study, all regions of the cornea showed a faster reduction in sensitivity with age in this sunny environment compared to the results of previous studies.