Denise S. Ryan

The U.S. Army Surface Ablation Study: comparison of PRK, MMC-PRK, and LASEK in moderate to high myopia.

PURPOSE To compare visual outcomes following photorefractive keratectomy (PRK), PRK with mitomycin C (MMC-PRK), and LASEK in moderate and high myopia in military personnel. METHODS This prospective, randomized contralateral eye study included 167 patients 21 years or older with manifest spherical equivalent -5.99 ± 1.40 diopters (D) (range: -3.88 to -9.38 D) randomized to either MMC-PRK or LASEK treatment in their dominant eye and conventional PRK without MMC in the fellow eye. All procedures were performed using the LADARVision 4000 Excimer Laser System (Alcon Surgical Inc., Ft. Worth, TX). High- and low-contrast visual acuities, manifest refraction, endothelial cell count, and corneal haze were evaluated up to 12 months postoperatively. RESULTS At 12 months postoperatively, visual outcomes were comparable among the treatment groups. Corneal haze of any grade was less common in MMC-PRK compared to PRK at 1 month (21.4% vs 31.0%; P < .01) and 3 months (12.8% vs 35.9%; P = .03) postoperatively; it was also less common in MMC-PRK compared to LASEK at 1 month (21.4% vs 55.9%; P < .01), 3 months (12.8% vs 42.4%; P < .01), and 6 months (12.2% vs 36.4%; P = .03) postoperatively. Haze rate (grade 0.5 or higher) was comparable between LASEK and PRK. Clinically significant haze (grade 2 or higher) developed after PRK (4 eyes) and LASEK (2 eyes), but not after MMC-PRK. CONCLUSIONS MMC-PRK showed some benefits in minimizing corneal haze formation. One year after surgery, there was no discernible difference in the postoperative refractive outcomes among the three methods.

Alcohol versus brush PRK: Visual outcomes and adverse effects†‡§¶‖

A smooth corneal surface prior to laser ablation is important in order to achieve a favorable refractive outcome. In this study, we compare PRK outcomes following two commonly used methods of epithelial debridement: Amoils epithelial scrubber (brush) versus 20% ethanol (alcohol).

Night Vision and Military Operations

Nighttime military operations include challenges encountered in daylight but also introduce unique visual and cognitive demands characteristic of a low-light environment. Because the majority of human sensory input is visual, and successful performance of military tasks is largely dependent on visual performance, it is critical for personnel operating in settings with reduced visual capability to maximize the abilities and strategies they retain. While military image intensification devices (e.g., night vision goggles, NVGs) significantly enhance visual performance, equipment can malfunction, batteries expire, and mission-specific combat loads may preclude utilization of all available aids. Hence the availability of optical aids should not undermine the importance of optimally corrected unaided night vision. This chapter discusses some of the important factors contributing to night vision and their influence on performance on commonly encountered tasks during military operations.

Wavefront-Guided Versus Wavefront-Optimized Photorefractive Keratectomy: Visual and Military Task Performance

PURPOSE To compare visual performance, marksmanship performance, and threshold target identification following wavefront-guided (WFG) versus wavefront-optimized (WFO) photorefractive keratectomy (PRK). METHODS In this prospective, randomized clinical trial, active duty U.S. military Soldiers, age 21 or over, electing to undergo PRK were randomized to undergo WFG (n = 27) or WFO (n = 27) PRK for myopia or myopic astigmatism. Binocular visual performance was assessed preoperatively and 1, 3, and 6 months postoperatively: Super Vision Test high contrast, Super Vision Test contrast sensitivity (CS), and 25% contrast acuity with night vision goggle filter. CS function was generated testing at five spatial frequencies. Marksmanship performance in low light conditions was evaluated in a firing tunnel. Target detection and identification performance was tested for probability of identification of varying target sets and probability of detection of humans in cluttered environments. RESULTS Visual performance, CS function, marksmanship, and threshold target identification demonstrated no statistically significant differences over time between the two treatments. Exploratory regression analysis of firing range tasks at 6 months showed no significant differences or correlations between procedures. Regression analysis of vehicle and handheld probability of identification showed a significant association with pretreatment performance. CONCLUSIONS Both WFG and WFO PRK results translate to excellent and comparable visual and military performance.

Corneal and Corneoscleral Injury in Combat Ocular Trauma from Operations Iraqi Freedom and Enduring Freedom

OBJECTIVES To examine the incidence and the etiology of corneal and corneoscleral injuries in the setting of combat ocular trauma, and to determine what effect these injuries have on overall visual impairment from combat ocular trauma. METHODS Retrospective, noncomparative, interventional case series, analyzing U.S. service members who were evacuated to the former Walter Reed Army Medical Center (WRAMC). Primary outcome measures were types of corneal injuries, length of follow-up at WRAMC, globe survival, and anatomical causes of blindness. Secondary outcome measures included surgical procedures performed, use of eye protection, source of injury, and visual outcomes. RESULTS Between 2001 and 2011, there were 184 eyes of 134 patients with corneal or corneoscleral injuries. The average age was 26 years (range, 18-50); 99.3% were male, 31.9% had documented use of eye protection. The average follow-up was 428.2 days (3-2,421). There were 98 right-eye and 86 left-eye injuries. There were 169 open-globe and 15 closed-globe injuries with corneal lacerations occurring in 73 eyes with injuries to Zone I. Most injuries were attributable to an intraocular foreign body (IOFB; 48%), followed by penetrating (19.6%) and perforating (16.3%) injuries. The most common presenting visual acuity was hand motion/light perception (45.7%), yet, at the end of the study, visual acuity improved to 20/40 or better (40.8%). The majority of injuries in eyes with visual acuity worse than 20/200 involved the cornea and retina (58%). Injuries solely to the cornea accounted for only 19% of all injuries sustained. CONCLUSIONS Ocular injuries in military combat have led to significant damage to ocular structures with a wide range of visual outcomes. The authors describe corneal and corneoscleral injuries in combat ocular trauma by classifying injuries by the anatomical site involved and identifying the main source of decreased visual acuity. In combat ocular trauma, corneal or corneoscleral injuries are not the sole etiology for poor vision. A cohesive approach among multiple ophthalmic subspecialties is needed when treating combat ocular trauma.

Development of VIPER: a simulator for assessing vision performance of warfighters

Background: When evaluating vision, it is important to assess not just the ability to read letters on a vision chart, but also how well one sees in real life scenarios. As part of the Warfighter Refractive Eye Surgery Program (WRESP), visual outcomes are assessed before and after refractive surgery. A Warfighter’s ability to read signs and detect and identify objects is crucial, not only when deployed in a military setting, but also in their civilian lives. Objective: VIPER, a VIsion PERformance simulator was envisioned as actual video-based simulated driving to test warfighters’ functional vision under realistic conditions. Designed to use interactive video image controlled environments at daytime, dusk, night, and with thermal imaging vision, it simulates the experience of viewing and identifying road signs and other objects while driving. We hypothesize that VIPER will facilitate efficient and quantifiable assessment of changes in vision and measurement of functional military performance. Study Design: Video images were recorded on an isolated 1.1 mile stretch of road with separate target sets of six simulated road signs and six objects of military interest, separately. The video footage were integrated with customdesigned C++ based software that presented the simulated drive to an observer on a computer monitor at 10, 20 or 30 miles/hour. VIPER permits the observer to indicate when a target is seen and when it is identified. Distances at which the observer recognizes and identifies targets are automatically logged. Errors in recognition and identification are also recorded. This first report describes VIPERs development and a preliminary study to establish a baseline for its performance. In the study, nine soldiers viewed simulations at 10 miles/hour and 30 miles/hour, run in randomized order for each participant seated at 36 inches from the monitor. Relevance: Ultimately, patients are interested in how their vision will affect their ability to perform daily activities. In the military context, in addition to reading road signs, this includes vision with night sensors and identification of objects of military interest. Once completed and validated, VIPER will be used to evaluate functional performance before and after refractive surgery. Results: This initial study was to prove the principle, and its results at the time of this publication were very preliminary. Nine Soldiers viewed visible-day and IR-day VIPER simulations with civilian and military targets, separately, at 10 and 30 miles/hour. Analyses were performed separately for visible and IR, and also aggregated. Only the civilian targets are discussed in this report. At 10 miles/hour, the population detected civilian road signs at an aggregated average of 90.11 ± 64.20 m, and identified them at 26.93 ± 22.27m. At 30 miles/hour, the corresponding distances were 103.03 ± 58.81 and 26.26 ± 8.55, respectively. Conclusion: This preliminary report proves the principle and suggests that VIPER could be a useful clinical tool in longitudinal assessment of functional vision in warfighters.