Corneal topography patterns in the Tehran eye study: warning about the high prevalence of patterns with a skewed radial axis

ABSTRACT

The purpose of this study is to determine the distribution of corneal topography patterns in Tehran. In this population-based study, a total of 442 individuals were randomly selected by cluster sampling for complete ophthalmologic examination. A total of 404 [788 eyes] met the inclusion criteria and were enrolled in this study. Orbscan II [Bausch and Lomb Surgical, Salt Lake City, USA] was used to determine the anterior segment indices and axial power maps for each eye. On the basis of the axial power maps, the symmetric bowtie [SB] [29.0%] and asymmetric bowtie with inferior steepening [16.7%] patterns were the most prevalent and the irregular [3.3%] and superior steepening [1.5%] patterns the least prevalent. Asymmetric bowtie pattern with a skewed radial axis [AB-SRAX] was seen in 7.6% of eyes. These cases had both thinner and steeper corneas compared with round and SB ones [P < 0.014 and P< 0.006]. Maximum anterior elevation in 5 mm zone, of AB-SRAX corneas were higher; than other patterns [P< 0.01] except for superior steepened and inferior steepened ones. The distribution of corneal topographic patterns in Iranians seems like other Asian population on the whole. The 7.6% prevalence of AB-SRAX patterns may be a warning on keratoconus prevalence in our population. This is in line with recent regional reports