Distribution of angle kappa measurements with Orbscan II in a population-based survey

To determine the mean angle kappa and its determinants in the population of Tehran, Iran.

In a cross-sectional survey with random cluster sampling, a total of 442 participants aged >14 years were selected from 4 municipality districts of Tehran for Orbscan acquisitions. Exclusion criteria were history of eye surgery for refractive errors, cataract or glaucoma, and use of topical medication or any type of contact lens at the time of the study. Mean angle kappa in different age and gender groups and its association with other factors was assessed. Considering the high correlation between the right and left eyes, only results of the right eyes are presented.

After applying exclusion criteria, 800 eyes (399 right eyes and 401 left eyes) were examined. Mean participant age was 40.6±16.8 years (range: 14 to 81 years), and 38.8% of eyes were from men. Mean angle kappa was 5.46±1.33° in total; 5.41±1.32° in men and 5.49±1.34° in women (P=.558). It decreased significantly with age; 0.015°/year (P<.001). In individuals with myopia, emmetropia, and hypermetropia, the mean value was 5.13±1.50°, 5.72±1.10°, and 5.52±1.19°, respectively (P=.025); the post-hoc test indicated this was due to the difference between emmetropes and myopes.

According to our results, angle kappa reduces with age, and the inter-gender difference is not significant. Largest angle kappas were seen among individuals with emmetropia. Angle kappas were larger in the hypermetropic population compared to the myopic population.