Anisometropia in a tropical hospital

This was to determine the prevalence and distribution of anisometropia and to study the difference in refraction between the eyes of patients with anisometropia and look for evidence of laterality, if any.

A prospective study of 1819 consecutive new patients seen in our clinic with no other pathology except refractive error between November 1998 and December 2002 were included in the study. Information obtained included age, sex, visual acuity, type and degree of anisometropic error. Non-parametric statistical methods were used for analysis.

Of 1819 patients seen, 815 (44.81%) had anisometropia. There were 389 males and 426 females with a male to female ratio of 1.00 to 1.1 and a mean age of 35.15 (standard deviation 17.38). Of the 815 patients, 476 (58.40%) had spherical anisometropia and 339 (41.60%) had cylindrical anisometropia. Myopic anisometropia (253 (31.04%) was the most common. Of the spherical anisometropic errors excluding the mixed types, majority (245 (57.65%) had a difference of 0.25 dioptres and 28 (6.59%) had a difference of 2.00 dioptres and above. The highest difference of 8 dioptres was found in only one patient. The mean error degrees were higher on the left in both myopia and hypermetropia.

Anisometropia is quite common in this environment. There is a tendency for the left to be higher contrary to previous findings. In order to allow for data comparison between countries and give room for the occasional high difference between eyes, it may be better to use both eyes in data analysis contrary to previous impression.