水凝胶复曲面棱镜压载隐形眼镜不同位置的氧气透过率。

Oxygen transmissibility at various locations in hydrogel toric prism-ballasted contact lenses.

作者信息

Eghbali F, Hsui E H, Eghbali K, Weissman B A

机构信息

Jules Stein Eye Institute, UCLA School of Medicine, USA.

出版信息

Optom Vis Sci. 1996 Mar;73(3):164-8. doi: 10.1097/00006324-199603000-00007.

DOI:10.1097/00006324-199603000-00007

PMID:8725017

Abstract

PURPOSE

Corneal metabolism is known to be adversely affected by anterior surface hypoxia. It has been demonstrated that contact lens (CL) oxygen transmissibility (Dk/L in cmmL O2/s mL mm Hg) is a direct function of the oxygen permeability (Dk in cm2 ml O2/mm Hg mL mm Hg) of the plastic divided by the thickness of the lens (L in cm). It has also been shown recently that the cornea should be sensitive to the Dk/L of that portion of a CL immediately overlying the tissue, in the absence of tear exchange and mixing; such is the case for all hydrogel CLs. Because hydrogel toric CLs are known to have anisomorphically variable thickness profiles, we have measured lens thickness along the vertical meridian and calculated local oxygen transmissibilities (Dk/L) for a series of hydrogel CLs.

METHODS

Thickness was measured at 5 locations along the vertical meridian of 16 different prescription toric hydrogel CLs of each of 6 brands (5 prism-ballasted design and 1 double-slab off design) and 12 different prescription spherical CLs of 2 brands (controls). Dk (at 38 degrees C) was calculated for each material from the nominal water content by a known relation.

RESULTS

We found that the average Dk/L for all lenses was greatest from the center (mean +/- SD of 8 +/- 4 x 10(-9)) to the superior portion (12 +/- 2 x 10(-9) at 6 mm from the CL center and 13 +/- 4 x 10(-9) at 3 mm from the CL center) of prism-ballast design toric CLs, and least in the lower portions (4 +/- 2 x 10(-9) at 6 mm from the lens center and 6 +/- 1 x 10(-9) at 3 mm from the CL center) of these CLs. Analysis of covariance showed that the effect of location for the prism-ballasted CLs is statistically significant (F = 203.11, p < 0.00005). One nonprism ballast toric CL design and the spherical designs showed minimal differences across the vertical meridian. We therefore conclude that clinicians should carefully monitor the physiological hypoxic response of the cornea, in particular the inferior area, during wear of prism-ballasted hydrogel lenses.

摘要

目的

已知角膜代谢会受到前表面缺氧的不利影响。业已证明，隐形眼镜（CL）的氧气透过性（以cmmL O2/s mL mmHg为单位的Dk/L）是塑料的氧气透过率（以cm2 ml O2/mm Hg mL mmHg为单位的Dk）除以镜片厚度（以cm为单位的L）的直接函数。最近还表明，在没有泪液交换和混合的情况下，角膜应该对紧邻组织的CL部分的Dk/L敏感；所有水凝胶CL均是如此。由于已知水凝胶复曲面CL具有各向异性变化的厚度分布，我们沿垂直子午线测量了镜片厚度，并计算了一系列水凝胶CL的局部氧气透过率（Dk/L）。

方法

对6个品牌的16种不同处方的复曲面水凝胶CL（5种棱镜稳定设计和1种双片旁位设计）以及2个品牌的12种不同处方的球面CL（对照），沿垂直子午线的5个位置测量厚度。根据已知关系，由标称含水量计算每种材料在38摄氏度时的Dk。

结果

我们发现，对于所有镜片，棱镜稳定设计的复曲面CL从中心（平均值±标准差为8±4×10⁻⁹）到上部（距CL中心6 mm处为12±2×10⁻⁹，距CL中心3 mm处为13±4×l0⁻⁹）的平均Dk/L最大，而在这些CL的下部（距镜片中心6 mm处为4±2×10⁻⁹，距CL中心3 mm处为6±1×10⁻⁹）最小。协方差分析表明，棱镜稳定CL的位置效应具有统计学意义（F = 203.11，p < 0.00005）。一种非棱镜稳定复曲面CL设计和球面设计在垂直子午线上的差异最小。因此，我们得出结论，临床医生在佩戴棱镜稳定水凝胶镜片期间，应仔细监测角膜的生理性缺氧反应，尤其是下部区域。