Higher Order Aberrations

"We used to not pay much attention to higher order aberrations because we couldn’t fix them." - Raymond Applegate, OD, PhD

"When I began doing wavefront research in the late 1980s, I realised that refractive surgery was increasing the aberrations of the eye and was causing a loss of best-corrected acuity." - Raymond Applegate, OD, PhD

Source: Eurotimes

J Refract Surg. 1997 May-Jun;13(3):295-9. Related Articles, Links

Refractive surgery, optical aberrations, and visual performance.

Applegate RA, Howland HC.

Department of Ophthalmology, School of Medicine, University of Texas Health Science Center at San Antonio, USA.

Visual optics is taking on new clinical significance. Given that current refractive procedures can and do induce large amounts of higher order ocular aberration that often affects the patient's daily visual function and quality of life, we can no longer relegate the considerations of ocular aberrations to academic discussions. Instead, we need to move toward minimizing (not increasing) the eye's aberrations at the same time we are correcting the eye's spherical and cylindrical refractive error. These are exciting times in refractive surgery, which need to be tempered by the fact that after all the research, clinical, and marketing dust settles, the level to which we improve the quality of the retinal image will be guided by the trade-off between cost and the improvement in the quality of life that refractive surgery offers.

American Journal of Ophthalmology

Volume 127, Issue 1 , January 1999, Pages 1-7

Comparison of corneal wavefront aberrations after photorefractive keratectomy and laser in situ keratomileusis.

Oshika T, Klyce SD, Applegate RA, Howland HC, El Danasoury MA.

Department of Ophthalmology, University of Tokyo School of Medicine, Japan. oshika-tky@umin.ac.jp

PURPOSE: To compare changes in the corneal wavefront aberrations after photorefractive keratectomy and laser in situ keratomileusis. METHODS: In a prospective randomized study, 22 patients with bilateral myopia received photorefractive keratectomy on one eye and laser in situ keratomileusis on the other eye. The procedure assigned to each eye and the sequence of surgery for each patient were randomized. Corneal topography measurements were performed preoperatively, 2 and 6 weeks, 3, 6, and 12 months after surgery. The data were used to calculate the wavefront aberrations of the cornea for both small (3-mm) and large (7-mm) pupils. RESULTS: Both photorefractive keratectomy and laser in situ keratomileusis significantly increased the total wavefront aberrations for 3- and 7-mm pupils, and values did not return to the preoperative level throughout the 12-month follow-up period. For a 3-mm pupil, there was no statistically significant difference between photorefractive keratectomy and laser in situ keratomileusis at any postoperative point. For a 7-mm pupil, the post-laser in situ keratomileusis eyes exhibited significantly larger total aberrations than the post-photorefractive keratectomy eyes, where a significant intergroup difference was observed for spherical-like aberration, but not for coma-like aberration. This discrepancy seemed to be attributable to the smaller transition zone of the laser ablation in the laser in situ keratomileusis procedure. Before surgery, simulated pupillary dilation from 3 to 7 mm caused a five- to six-fold increase in the total aberrations. After surgery, the same dilation resulted in a 25- to 32-fold increase in the photorefractive keratectomy group and a 28- to 46-fold increase in the laser in situ keratomileusis group. For a 3-mm pupil, the proportion of coma-like aberration increased after both photorefractive keratectomy and laser in situ keratomileusis. For a 7-mm pupil, coma-like aberration was dominant before surgery, but spherical-like aberration became dominant postoperatively. CONCLUSIONS: Both photorefractive keratectomy and laser in situ keratomileusis increase the wavefront aberrations of the cornea and change the relative contribution of coma- and spherical-like aberrations. For a large pupil, laser in situ keratomileusis induces more spherical aberrations than photorefractive keratectomy. This finding could be attributable to the smaller transition zone of the laser ablation in the laser in situ keratomileusis procedure.