To study the relationship between the distribution of the ocular surface temperature and the nasal predominance in pterygium.

In order to identify the distribution of the ocular surface, the surface temperature was measured at four points on the eyelids and on the bulbar conjunctiva with a non-contact thermometer. The ocular surface temperature in the pterygium patient group was compared with that in a normal control group. The temperature difference at each point on the ocular surface was also examined.

In both of the patient and the normal groups, the surface temperature on the eyelid was at its lowest on the temporal lower eyelid, and highest on the nasal upper eyelid. On the bulbar conjunctiva, the surface temperature of the nasal conjunctiva was at its lowest, and at its highest on the upper conjunctiva. The most distinctive temperature difference between the patient and control groups was shown on the nasal and temporal bulbar conjunctivas, and statistically significant ( p <0.05).

Considering the temperature distribution over the ocular surface, we propose that an intrinsic factor that causes the nasal predominance of pterygium could be the comparatively low local temperature of the nasal bulbar conjunctiva.