The human body temperature is a good health indicator. All objects emit thermal radiation as a function temperature and wavelength for all wavelengths. The wavelength of infrared rays lies between visible and microwave radiations ranging between 700 nm to 0.1 mm. Infrared (IR) imaging is relatively inexpensive, noninvasive and harmless. Nowadays, it is widely used in the medical field for diagnosis. In this work, we have applied image processing techniques on the IR images of the eye for the analysis of the ocular surface temperature (OST) of the normal subjects of three categories (young, middle and old ages). In our study, 67 IR normal images were analyzed. Two parameters, average ocular temperature and the temperature deviation were proposed to study the variability of OST in different normal category subjects. Our study shows that, the two parameters proposed, show distinct ranges for different groups with 'p' values less than 0.05.