Pupillary Offset in Keratoconus and its Relationship with Clinical and Topographical Features

To evaluate the change in the location of pupillary center with corneal tomography in keratoconic patients, and determine the correlation of pupillary offset with clinical and topographical features of keratoconus.

Ninety-one eyes of the 54 patients with keratoconus in different stages and 39 eyes of 39 refractive surgery candidates with normal corneas were included in our study. Ocular aberrations and the pupillary offset parameters (x-offset and y-offset) over a 5 mm (undilated) pupil were measured with a Sirius corneal tomographer. A correlation analysis among the pupillary offset parameters and the possible determinative variables (topographical and tomographical parameters, corneal aberrations and best corrected visual acuity) was performed.

The mean pupillary offset was significantly greater in the keratoconic eyes compared with the controls (p = 0.003), and the difference was mostly due to the y-offset (p = 0.03). There was no significant difference between the groups in the mean horizontal pupillary offset value (p = 0.07). Both the vertical and the total pupillary offset values correlated significantly (p < 0.0001) with the keratoconus stage (r = 0.58 and r = 0.51, respectively). They also correlated with the corneal aberrations, and negatively correlated with the visual acuity.

The pupillary offset seems to correlate with the clinical and topographic features of keratoconus. It may be important to quantify its magnitude and direction in order to ensure correct centralization of the corneal procedures.