Imayasu M, Petroll W M, Jester J V, Patel S K, Ohashi J, Cavanagh H D
Department of Ophthalmology, University of Texas Southwestern Medical Center at Dallas 75235-9057.
Ophthalmology. 1994 Feb;101(2):371-88. doi: 10.1016/s0161-6420(94)31326-1.
To assess adverse effects of contact lens-induced hypoxia on the rabbit cornea in vivo and determine the relation between binding of Pseudomonas aeruginosa and oxygen transmissibility for rigid and hydrogel lenses.
Six rigid lenses with Dk/Ltotal values between 0 and 97 x 10(-9) (cm/second) (ml O2/ml mmHg) and four hydrogel lenses (Dk/Ltotal 9, 20, 39, 51) were tested. All lenses had 14.0-mm diameters and a thickness (parallel) of 0.12 or 0.15 mm. Tear lactate dehydrogenase activity and tandem scanning confocal microscopy determinations were performed after the lens was worn for 24 hours. Binding of P. aeruginosa then was separately determined by the colony-forming unit method. Scanning electron microscopy was used to confirm in vivo tandem scanning confocal microscopy findings.
Lens oxygen transmissibility determines binding of P. aeruginosa to the cornea after the lens is worn for 24 hours; epithelial damage produced by lenses of lower Dk/Ltotal appears to be the dominant biologic factor for P. aeruginosa binding and not lens rigidity.
These results suggest that the risk of P. aeruginosa keratitis developing with overnight wear will be enhanced significantly for contact lenses with Dk/Ltotal values less than 50 x 10(-9) (cm/second) (ml O2/ml mmHg) (human equivalent oxygen percentage < or = 15%), and this risk will increase with further decreases in oxygen transmissibility. Because no hydrogel lenses approved by the Food and Drug Administration are available with oxygen transmission at this level, patients should be made aware of the increased risk of infectious keratitis associated with the overnight wear of current extended wear hydrogel lenses. Results of this study also demonstrate that quantitative clinical tandem scanning confocal microscopy imaging and tear lactate dehydrogenase activity measurements can provide prospective, noninvasive methods for assessing the ongoing interaction between contact lens and cornea in vivo.
评估隐形眼镜引起的缺氧对兔角膜的体内不良反应，并确定铜绿假单胞菌的黏附与硬性和水凝胶镜片的氧透过率之间的关系。
测试了6片Dk/Ltotal值在0至97×10⁻⁹（厘米/秒）（毫升氧气/毫升毫米汞柱）之间的硬性镜片和4片水凝胶镜片（Dk/Ltotal分别为9、20、39、51）。所有镜片直径均为14.0毫米，（平行）厚度为0.12或0.15毫米。佩戴镜片24小时后进行泪液乳酸脱氢酶活性测定和串联扫描共聚焦显微镜检查。然后通过菌落形成单位法分别测定铜绿假单胞菌的黏附情况。使用扫描电子显微镜确认体内串联扫描共聚焦显微镜检查结果。
镜片的氧透过率决定了佩戴镜片24小时后铜绿假单胞菌与角膜的黏附；Dk/Ltotal较低的镜片产生的上皮损伤似乎是铜绿假单胞菌黏附的主要生物学因素，而非镜片的硬度。
这些结果表明，对于Dk/Ltotal值小于50×10⁻⁹（厘米/秒）（毫升氧气/毫升毫米汞柱）（人体等效氧百分比≤15%）的隐形眼镜，过夜佩戴时发生铜绿假单胞菌性角膜炎的风险将显著增加，并且这种风险会随着氧透过率的进一步降低而增加。由于美国食品药品监督管理局批准的水凝胶镜片目前没有达到此水平的氧透过率，应让患者了解与当前过夜佩戴的延长佩戴型水凝胶镜片相关的感染性角膜炎风险增加。本研究结果还表明，定量临床串联扫描共聚焦显微镜成像和泪液乳酸脱氢酶活性测量可为评估隐形眼镜与角膜在体内的持续相互作用提供前瞻性、非侵入性方法。
