Abstract
Abstract: :
Purpose Excimer laser surgery (LASIK and PRK) has proven effective for correction of refractive error, and holds great promise for widespread application in military environments. While service members typically achieve normal post-operative visual acuity and satisfy military retention standards, less is known about performance in operational settings, particularly at night. Our purpose is to conduct a prospective evaluation of night vision goggle (NVG) and night firing performance in soldiers treated with LASIK and PRK. We report initial (1-month) findings in nine soldiers. Methods 9 subjects underwent surgery for naturally occurring myopia or myopic astigmatism using the ALCON LADARVision laser system. Night Firing Range performance with the M-16A2 was measured preoperatively and at 1 month after surgery under the following conditions (corrected and uncorrected): 1) NVG and aiming light under simulated starlight, and 2) iron sight under low light (simulated dusk). Targets were scored using a standard system. Before and after surgery scores were compared for the iron sight and NVG sight. Results A comparison of post-operative performance without correction to pre-operative performance with correction is the most relevant for military operations. In nine subjects tested thus far, 1-month post-operative night firing score (without optical correction) was not significantly different from pre-operative performance with best correction for either the iron sight or NVGs (p>0.4). Interestingly, mean post-operative firing with NVGs (but without optical correction), was slightly higher than mean pre-operative NVG firing performance (with best correction), and this difference approached significance (p=0.08). Conclusions Despite reports of reduced night vision following laser refractive surgery, performance of one important military task, firing a weapon in low light setting, improved in this study. Initial results indicate that, by 1-month after surgery night firing performance without optical correction is equal to or slightly better than pre-operative performance with best correction. The trend toward improved post-operative firing performance with NVGs may reflect the lack of intervening spectacle correction between NVG and observer, which can impede performance by increasing reflections, distortion, and weight. The finding of enhanced performance through NVGs is consistent with our previous study of NVG visual acuity (Bauer at al, ARVO 2001 Abstract 3266).
Keywords: refractive surgery • contrast sensitivity • visual cortex