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Wavefront-guided versus wavefront-optimized photorefractive keratectomy: clinical outcomes, higher order aberrations and patient satisfaction

Poster Details

First Author: K.Bower USA

Co Author(s):    R. Sia   D. Ryan   J. Pasternak   R. Stutzman   J. Eaddy   L. Logan

Abstract Details



Purpose:

To compare visual outcomes between wavefront-guided (WFG) photorefractive keratectomy (PRK) with the VISX STAR S4 CustomVue Excimer Laser with iris registration (Abbott Medical Optics, Santa Ana, California) and wavefront-optimized (WFO) PRK with the Allegretto Wave Eye-Q 400 Hz Excimer Laser System (Alcon Surgical, Fort Worth, Texas).

Setting:

This prospective, randomized clinical trial was conducted at the Warfighter Refractive Eye Surgery Program and Research Center at Fort Belvoir, Fort Belvoir, Virginia, USA and the Ophthalmology Service, Walter Reed National Military Medical Center, Bethesda, Maryland, USA. Participants included 108 Active duty U.S. service members age 21 or over with myopia or myopic astigmatism up to -10.00 diopters (D) manifest spherical equivalent (MSE) and refractive cylinder up to 4.00 D who were randomized to undergo either bilateral WFG PRK (n=55 patients, 110 eyes) or WFO PRK (n=53 patients, 106 eyes). Participants were followed 12 months (M) postoperatively. Primary outcome measures were uncorrected (UDVA) and corrected distance visual acuity (CDVA), manifest spherical equivalent (MSE), and corneal haze. Secondary outcome measures included higher order aberrations, contrast sensitivity and patient satisfaction.

Methods:

UDVA, CDVA, MSE, slit lamp biomicroscopy, wavefront aberrometry, low-contrast visual acuity (LCVA), contrast sensitivity (CS), and subjective visual performance were assessed preoperatively and at 1M, 3M, 6M and 12M postoperatively. LCVA was performed using logMAR charts with 5% and 25% contrast (Precision Vision Inc. La Salle, Illinois). CS was measured using the Metropsis Visual Stimulus Generation Device (Cambridge Research Systems Ltd., Kent, UK) at five spatial frequencies (SF): 1.5, 3.0, 6.1, 13.1, and 19.7 cycles per degree (cpd). The two-alternative, forced-choice protocol used a 90º Gabor stimulus with mean luminance of 50 cd/m2. CS was analyzed at each SF over time and the change in area under the log contrast sensitivity function (AULCSF) was determined. Aberrometry was performed using the Complete Ophthalmic Analysis System (COAS, Abbott Medical Optics, Santa Ana, California). Aberrations were measured using 6-mm pupil and Zernike polynomial series was calculated. For analysis, the absolute root mean square (RMS) of each Zernike mode was determined and the amount of coma, trefoil, spherical aberration and total higher order aberrations (HOA) were calculated. A questionnaire was administered to determine visual difficulties and general satisfaction with postoperative vision using a 10-point scale ranging from 1 (none) to 10 (disabling symptoms).

Results:

UDVA >20/20 was comparable between groups at all timepoints. UDVA >20/15 was better for WFG at 1M (67.6% vs. 53.8%, P=0.05) but not at other timepoints. MSE ±0.50D was comparable at all time points (P>0.05). Three eyes in each group lost ≥2 lines CDVA at 1M (P=0.99). No eye lost ≥2 lines CDVA at other timepoints. Corneal haze ≥ grade 2 was comparable at 1M and 3M (P=0.33) and was not seen in either group at 6M or 12M. More WFG maintained or gained 5% LCVA at 3M (P<0.01), 6M (P=0.01) and 12M (P<0.01) compared to WFO. 25% LCVA was comparable at all timepoints (P>0.05). CS was comparable at all SF except 3.0 cpd where CS significantly decreased in WFO. At 12M the postoperative change in AULCSF was comparable between WFG and WFO (P=0.39). At 6M WFG increased spherical aberration (P<0.01) but reduced trefoil (P<0.01), whereas WFO induced significant coma (P<0.01), spherical aberration (P<0.01) and total HOA (P<0.01). The changes in coma (P<0.01), trefoil (P<0.01) and total HOA (P<0.01) were significant between WFG and WFO. There were no subjective questionnaire differences in terms of daily activities, dry eye, vision fluctuation, ghost images, glare, halo, vision expectations, and overall satisfaction (P>0.05).

Conclusions:

Standard clinical measures of efficacy, predictability and safety, including UDVA, MSE, CDVA, and corneal haze, were largely comparable between WFG and WFO PRK at all postoperative intervals out to 12M. The lone exception was the percent with UDVA > 20/15, which was better at 1M in the WFG group. 5% LCVA was superior in the WFG treated eyes but the groups were comparable in terms of 25% LCVA and contrast sensitivity. WFO treatment induced more wavefront aberrations than WFG treatment. There were no significant differences in patient reported quality of vision and satisfaction between WFG and WFO PRK. From the present study we conclude that while there are measurable advantages of WFG over WFO PRK in terms of objective quality of vision -- wavefront aberrations and to an extent contrast acuity -- there is no significant difference in clinical outcomes or subjective quality of vision. Further study is needed to determine the impact of postoperative changes in HOA on quality of vision and more importantly on vision-dependent task performance. FINANCIAL INTEREST: NONE

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