Posters

Wavefront-guided versus wavefront-optimized photorefractive keratectomy: visual and military task performance

Poster Details

First Author: K.Bower USA

Co Author(s):    D. Ryan   R. Sia   R. Stutzman   J. Pasternak   C. Howell   T. Maurer

Abstract Details

Purpose:

To compare the visual performance, military task performance, and threshold target identification of participants undergoing using 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, Virginia and the Night Vision and Electronic Sensors Directorate, Fort Belvoir, Virginia, USA. 54 participants, age 21 or over with myopia up to -10.0 diopters (D) and astigmatism up to 4.0D were randomized to undergo either WFG (27 participants, 54 eyes) or WFO (27 participants, 54 eyes) PRK. Pre- and postoperative vision testing as well as surgery and clinical examinations were performed at the Warfighter Refractive Eye Surgery Program and Research Center, while all night firing and human performance testing were performed at the Night Vision and Electronic Sensors Directorate. Subjects were followed for up to 12 months (M) postoperatively.

Methods:

Visual performance was assessed using the Rabin Super Vision Test high contrast ( SVT HC) and contrast sensitivity (SVT CS) chart (PrecisionVision, La Salle, Illinois), and 25% contrast acuity with night vision goggle (NVG) filter (25% NV) preoperatively and at 1M, 3M, 6M and 12M. The change from baseline of SVT HC, SVT CS, and 25% NV was calculated at each timepoint and compared between groups. 27 participants (13 WFG, 14 WFO) underwent additional evaluation of marksmanship performance with M16-A4 rifle under three test conditions: (1) iron sight in low light (simulating 'dusk'); (2) NVG with weapon mounted aiming light; and (3) weapon-mounted forward-looking infrared (FLIR) thermal sight, the latter two in conditions simulating 'starlight'. Range scores without correction at 6W and 6M were compared to baseline scores with correction. Finally, 27 participants (14 WFG, 13 WFO) were evaluated in a series of visual tasks designed to test subjects' ability to (1) identify vehicles at different ranges using thermal signatures; (2) discriminate handheld objects of military interest; and (3) search for human targets in a high clutter infrared scene. Threshold target identification was evaluated testing the probability of identification of varying target sets preoperatively and at 6M for each participant.

Results:

Fisher's exact test showed significant difference in SVT HC between WFG and WFO at 1M with 66.7% WFG vs. 90.7% WFO demonstrating either no change or a gain in one line of acuity (P<0.01). There was no significant difference in SVT CS at any time point. There was a significant difference in 25% NV at 1M with 61.1% WFG vs. 83.3 WFO demonstrating either no change or a gain of one or more lines (P= 0.02). Firing range scores using the iron sight were equal or better than baseline in 69.2%WFG vs. 71.4% WFO at 6W (P=0.99) and 62.5% WFG vs. 63.6% WFO at 6M (P=0.99). NVG scores were equal or better than baseline in 61.5% WFG vs. 85.7% WFO at 6W, which was not statistically significant (P=0.21). At 6M there was no difference between groups: 77.8% WFG vs. 72.7% WFO (P=0.99). FLIR scores were equal or better than baseline in 46%WFG vs. 64.3% WFO at 6W (P=0.49) and 44.4% WFG vs. 81.8% WFO at 6M (P=0.16). There was no significant difference between treatment groups in their ability to identify combat vehicles (P=0.99), discriminate handheld objects (P=0.99), or search for human targets in high clutter environment (P=0.99).

Conclusions:

WFO was superior to WFG PRK at 1M in terms of SVT HC and 25% NV. SVT HC, SVT CS, and 25% NVG were otherwise comparable over time. There was an overall improvement following both WFG and WFO treatment with no significant degradation in visual outcomes in either group. Firing performance was comparable at each time point, with a significant percentage in both treatment groups performing as well or better without corrective lenses after surgery than they scored before surgery with correction. Although there was a trend toward superiority of WVO over WFG with the NVG at 6W and the FLIR at both 6W and 6M, this did not reach statistical significance. Overall, for each respective treatment group, the postoperative target task performance was retained or improved after surgery with no significant difference between treatment groups. We conclude that both WFG and WFO PRK provide comparable results when assessed with rigorous quality of vision tests, including vision-dependent functional task performance measures. FINANCIAL INTEREST: NONE