To minimize higher-order optical errors, special efforts to center the ablation zone are necessary; for example, by eye-tracking systems that consider the visual axis.

To study the effects of photorefractive keratectomy on ocular optical aberrations and to establish correlations with glare vision and low-contrast vision. Methods: Preoperative ocular aberroscopy of 15 eyes undergoing photorefractive keratectomy was compared with aberroscopy at 3 months postoperatively by means of a newly developed automated aberroscope of the Tscherning type. The correlation of the wavefront errors with best spectacle-corrected visual acuity, low-contrast visual acuity, and visual acuity under glare conditions was analyzed. Results: In any individual treated, the total wavefront errorincreased.Onaverage,thetotalwavefronterrorincreased by a factor of 17.65; this increase was highly statistically significant (P = .001). Also, the correlation with bestcorrected visual acuity, low-contrast visual acuity, and glare visual acuity was statistically significant (P = .02, P = .001, and P = .03, respectively). The increase in ocular aberrations was significantly related with the virtual pupil size. Conclusions: Photorefractive keratectomy increases the ocular aberrations, impairing the visual performance of the eyes treated. In detail, scotopic visual measures such as low-contrast visual acuity and glare visual acuity suffer most from the myopia correction. Aberroscopyguided photorefractive keratectomy may avoid such effects.

Wavefront-guided LASIK is a promising technique that offers the potential to correct refractive errors, to improve visual acuity, and to increase the quality of vision, especially under mesopic conditions. Studies that include selective overcorrection of different Zernike components are needed to achieve better correction of the aberrations. Prospective controlled clinical studies must clarify the major benefits of wavefront-guided LASIK.

The use of active eye tracking appeared to improve the optical and visual outcomes but did not affect the refractive outcome after photorefractive laser surgery.

Both PRK and cataract surgery are operations which may considerably increase the ocular optical errors of higher order. These aberrations are not predictable and can affect the visual acuity despite optimal sphero-cylindrical correction, in particular under mesopic conditions.