The effects of high altitude induced hypoxia on the visual acuity and quality of aircrew in soft contact lens wear

• Main Authors: Wang Shih-Lan, 王詩嵐
• Other Authors: 陳建同,李敏輝
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/39629563700256758720

碩士 === 國防醫學院 === 航太醫學研究所 === 97 === Introduction: At least 80% of all information acquired by aircrew in flight is vision. In order to maintain flight safety and flight performance, aircrew should have excellent visual function. However, hypoxia is the most aviation hazard to vision. Recently, the prevalence of refractive error is high in Taiwan, and wearing soft contact lens might be chosen to correct visual acuity in R.O.C. military in the future. The stability of visual acuity and flight performance might be affected when PO2 is lower than basic metabolism of cornea. Some studies indicate the new material - silicone hydrogel (SH) can provide higher O2 transmissibility and improve the symptoms of dryness and discomfort than that of the conventional hydrogel contact lens in most environments. The purpose of this study was to determine the efficacy and safety of SH contact lens wear under high altitude environment. Methods: Thirteen subjects wearing SH contact lens were exposed to 35,000 ft in hypobaric chamber (Type I chamber fly); six subjects were subjected to 18,000 ft in hypobaric chamber (Type VI chamber fly); and four subjects were tested to 8,000 ft in aircraft (Beech-1900)(In-flight). Vision performance and physiologic response were monitored by measurements of visual acuity, contrast sensitivity, visual function questionnaire(NEI-VFQ) and slit-lamp examinations. Results: All subjects ‘s questionnaire scores were not statistically different between before and after exposure(Type I chamber fly: pre-exposure scores is 96.75±0.63, post-exposure scores is 96.57±0.73; Type VI chamber fly: pre-exposure scores is 95.24±1.26, post-exposure scores is 95.24±1.26; In-flight: pre-exposure scores is 96.88±1.19, post-exposure scores is 95.09±1.54) and the slit-lamp examinations were unremarkable. The performance of night visual acuity and night contrast sensitivity were worse than day’s but still in the normal range. There were no statistically significant in visual acuity and contrast sensitivity neither in day nor night. Conclusions: Wearing SH contact lens in high altitude and hypoxia environment did not make eyes discomfort, cornea edema and cornea injury. Visual acuity and contrast sensitivity were normal. Therefore, SH contact lens may provide another choice of treatment to correct refractive error in military aircrew.