Aim: To evaluate the changes in correlations of higher order aberrations of the first corneal surface with halo phenomena, a form of image degradation, under night vision conditions measured objectively after successful LASIK surgery.
Methods: This is a prospective, observational, analytical study of 110 eyes that undergone successful LASIK surgery for myopia and astigmatism. Pre-operative sphere was -3.48±1.70 D [0 to -8.00 D] and pre- operative cylinder was -0.86±0.87 D [0 to -4.00 D]. Visual disturbance caused by halo phenomena with the Starlights v1.0 and pupil size with Colvard pupilometry were measured after adaptation to a dark environment (0.17 lux). Corneal aberrations were computed for a corneal diameter representative of the eye's entrance pupil under night vision conditions.
Results: The halo disturbance index increased in this study by a factor of 2.15 after successful LASIK surgery. Total RMS for monochromatic higher order aberration displayed a significant correlation with halo disturbance index (r=0.42; p<0.01). However, only secondary astigmatism (r=0.36; p<0.01) coma (r=0.25; p=0.02) and spherical aberration (r=0.40; p<0.01) were responsible for such behavior, with the remaining corneal aberrations until the 6th order not displaying any significant correlation when considered individually.
Conclusion: Patients undergoing LASIK procedures display an increase of halo phenomena around lights in night vision conditions, even when the results of the surgery are considered entirely satisfactory according to current international standards of predictability, efficacy and safety. Secondary astigmatism, coma and spherical aberration are the higher order aberrations until the 6th order that significantly correlated with halo disturbance index.
- corneal aberration
- halo phenomena
- higher order aberrations
- night vision disturbance