Using the Freiburg Acuity and Contrast test to measure visual performance in USAF personnel after PRK
Using the Freiburg Acuity and Contrast test to measure visual performance in USAF personnel after PRK
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DOI：
10.1097/00006324-200407000-00013
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发表时间：
2004-07-01
影响因子：
1.4
通讯作者：
Thompson, WT
中科院分区：
文献类型：
--
作者：
Dennis, RJ;Beer, JMA;Thompson, WT
目的。光屈光性角膜切除术（PRK）可能是美国空军（USAF）机组人员佩戴眼镜和隐形眼镜的替代方案，并且可能在作战情况下提供一些明显的优势。然而，PRK残留的任何角膜薄雾或疤痕形成都可能加剧明亮眩光源对复杂视觉任务的致残作用。美国空军最近完成了一项关于PRK对视觉表现的长期影响的纵向临床评估，包括上述实验。收集基线数据后，20名非飞行现役美国空军人员接受了PRK。然后在PRK后6、12和24个月测量视觉表现。视觉敏锐度（VA）和对比敏感度（CS）数据通过弗莱堡敏锐度和对比度测试（FrACT）收集，受试者通过聚碳酸酯挡风玻璃观看一半的跑步。实验在三种眩光条件下完成：无眩光源，在Landolt C刺激周围有宽带或绿色激光（532 nm）眩光环（亮度类似于6090 cd/m(2)）。相对于基线，PRK对VA的系统性影响尚未确定。然而，与宽带眩光源相比，激光眩光源的VA几乎差了2个完整的斯伦线。在无眩光和宽带眩光条件下，PRK后的CS性能显著下降；无论有没有挡风玻璃，情况都是如此。与VA一样，激光眩光对CS性能的影响比宽带眩光更大。PRK似乎没有影响VA，但CS的变化可能代表了视觉表现的真正下降。与宽带眩光相比，激光更大的破坏性影响可能是由于激光刺激周围的相干空间噪声（散斑）增加了掩蔽。
Purpose. Photorefractive keratectomy (PRK) may be an alternative to spectacle and contact lens wear for United States Air Force (USAF) aircrew and may offer some distinct advantages in operational situations. However, any residual corneal haze or scar formation from PRK could exacerbate the disabling effects of a bright glare source on a complex visual task. The USAF recently completed a longitudinal clinical evaluation of the long-term effects of PRK on visual performance, including the experiment described herein.Methods. After baseline data were collected, 20 nonflying active duty USAF personnel underwent PRK. Visual performance was then measured at 6, 12, and 24 months after PRK. Visual acuity (VA) and contrast sensitivity (CS) data were collected by using the Freiburg Acuity and Contrast Test (FrACT), with the subject viewing half of the runs through a polycarbonate windscreen. Experimental runs were completed under 3 glare conditions: no glare source and with either a broadband or a green laser (532-nm) glare annulus (luminance similar to6090 cd/m(2)) surrounding the Landolt C stimulus.Results. Systematic effects of PRK on VA relative to baseline were not identified. However, VA was almost 2 full Snellen lines worse with the laser glare source in place versus the broadband glare source. A significant drop-off was observed in CS performance after PRK under conditions of no glare and broadband glare; this was the case both with and without the windscreen. As with VA, laser glare disrupted CS performance significantly and more than broadband glare did.Conclusions. PRK does not appear to have affected VA, but the changes in CS might represent a true decline in visual performance. The greater disruptive effects from laser versus broadband glare may be a result of increased masking from coherent spatial noise (speckle) surrounding the laser stimulus.