Abstract
Abstract: :
Purpose: Previous studies have shown a dramatic decrease in corneal sensitivity to touch as a function of corneal eccentricity. The purpose of study was to examine the eccentricity variation in human corneal sensitivity to mechanical and cooling stimulae delivered by a non–contact Belmonte pneumatic esthesiometer. Methods: 15 healthy subjects (9 males and 6 females, age from 21 to 46 years) participated in the study. Corneal thresholds of right eye of each subject were measured at five locations of the cornea, i.e. central (C), nasal and temporal mid–peripheral (N2 and T2, on pupil edge) and nasal and temporal peripheral corneal (N1 and T1, within 1mm of limbus). Stimulus temperature was 20°C and 50°C and was delivered by a computer controlled Belmonte esthesiometer in two separate sessions. The method of constant stimuli was used to determine the threshold at each location of the cornea. Results: The mechanical and cooling thresholds (±se, ml/min) for each location are listed in the table. A significant difference in threshold was found between locations regardless of temperature (ANOVA F(4,56)=5.98, P=0.000). Threshold at T1 was significantly lower than at T2, N1 and N2 (post–hoc tests all p<0.05) while the difference between C and N2 was also marginally significant (post–hoc test p=0.05).
Conclusions: This study demonstrated variation of sensitivity across horizontal meridian of the cornea with cooling and mechanical stimuli. The pattern of variation in corneal sensitivity measured by pneumatic esthesiometry is different to that obtained by Cochet–Bonnet esthesiometry.
Keywords: innervation: sensation • cornea: basic science