Keratometry measurements, corneal astigmatism and irregularity in a normal population: the Tehran Eye Study.

PURPOSE: To determine the mean corneal power, astigmatism, and irregularity in a sample from the population of Tehran.

MATERIALS AND

METHODS

Four hundred and forty-two people residing in the first four municipality districts of Tehran were selected through a random stratified cluster sampling approach, 410 of which met the inclusion criteria and were enrolled in the study to have Orbscan II acquisitions between 9:00 am and 7:00 pm. The values obtained for keratometry, corneal astigmatism, and corneal irregularity were studied.

RESULTS

The mean keratometry reading was 44.39 diopter (D) [95% confidence interval (CI): 44.22-44.57]. Age, spherical equivalent and corneal diameter were significantly correlated with mean keratometry reading in the multivariate model. Mean corneal astigmatism was 0.98 D (95% CI: 0.89-1.06), also significantly correlated with spherical equivalent in the multivariate model. Mean corneal irregularity in the central 3 mm zone was 1.25 D (95% CI: 1.20-1.29); this was significantly correlated with age.

CONCLUSIONS

In a sample of the Tehran population, we found higher values of mean corneal power, astigmatism, and irregularity compared to other reports. Considering the high prevalence of cases of suspect keratoconus in the studied population, it is important to pay more attention to corneal indices in keratorefractive surgery.