Effect of pterygia on refractive indices, corneal topography, and ocular aberrations

To investigate the effect of different sizes of pterygium on ocular aberrations along with corneal refractive changes, keratometry, and corneal topography.

Forty eyes of 34 patients who had different sizes of primary nasal pterygium and 40 eyes of 22 age- and sex-matched healthy subjects without a clinical diagnosis of pterygium or pinguecula were enrolled in this study. All patients underwent a measurement of uncorrected and best spectacle-corrected visual acuities, corneal topography, and ocular aberrations. The pterygia sizes were measured with a slit lamp by using a slit beam of light.

All indices (topographic/refractive spherical and astigmatic values and topographic/refractive spherical equivalent) were higher in the pterygia group than in the control group. Both horizontal length (Rho: 0.64 and P < 0.001) and width of pterygia (Rho: 0.68 and P < 0.01) were found to be correlated with corneal astigmatism. When the root mean square values of ocular aberrations were compared among the groups (control, small, medium, and large size pterygia), differences were found to be statistically significant regarding all parameters including total (P < 0.001), tilt (P < 0.001), higher order aberrations (P < 0.001), total coma (P < 0.001), total trefoil (P < 0.001), total tetrafoil (P < 0.001), total spherical aberrations (P = 0.004), and higher order astigmatism (P < 0.001). Moreover, the root mean square values of ocular aberrations seem to strongly correlate with both horizontal length and width of pterygia.

Pterygia, particularly with larger sizes, seem to be correlated with increased ocular aberrations. Moreover, increase of ocular aberrations may become one of the indications for surgical treatment if this association is supported by further investigations.