Contact Lens and Visual Optics Laboratory, School of Optometry and Vision Science, Queensland University of Technology, Australia.
Contact Lens and Visual Optics Laboratory, School of Optometry and Vision Science, Queensland University of Technology, Australia.
Cont Lens Anterior Eye. 2019 Feb;42(1):63-69. doi: 10.1016/j.clae.2018.07.003. Epub 2018 Jul 13.
To examine the influence of centre thickness upon miniscleral lens flexure and the association between the magnitude of in-vivo lens flexure and scleral toricity.
In-vivo lens flexure was measured using a videokeratoscope in 9 healthy young participants (25 ± 4 years) with normal corneae fitted with ICD 16.5 miniscleral lenses (hexafocon B material) with centre thicknesses of 150, 250, and 350 μm. Scleral toricity was determined from sagittal height data over a 15 mm chord obtained from a corneo-scleral topographer.
On average, lens flexure increased with decreasing centre thickness, but remained <0.50 D (mean increase <0.25 D, p = 0.63). Scleral toricity was positively correlated with in-vivo flexure for the 150 μm (r = 0.77, p = 0.02) and 250 μm (r = 0.72, p = 0.03) lenses. Using a group mean split, eyes with >200 μm scleral toricity exhibited greater in-vivo flexure than eyes with <200 μm (0.40 D more, averaged across all lenses, p = 0.02), and this effect was greatest for the 150 μm lens (0.61 D more, p = 0.04).
Decreasing the centre thickness from 350 μm to 150 μm resulted in <0.25 D increase in lens flexure for a high Dk and low modulus material. Scleral toricity >200 μm was associated with more in-vivo lens flexure. When intentionally reducing scleral lens centre thickness to enhance oxygen transmissibility, customised back surface designs may be required to minimise in-vivo flexure in eyes with >200 μm scleral toricity at a 15 mm chord.
研究中心厚度对巩膜镜弯曲度的影响，以及活体镜片弯曲度与巩膜扭转之间的关系。
在 9 名健康年轻参与者（25 ± 4 岁）中，使用角膜地形图仪测量活体镜片弯曲度，参与者的角膜正常，佩戴的是中心厚度为 150、250 和 350μm 的 ICD 16.5 巩膜微透镜（六氟康 B 材料）。通过角膜-巩膜地形图在 15mm 弦长上获得的矢状高度数据确定巩膜扭转度。
平均而言，镜片弯曲度随中心厚度的降低而增加，但仍<0.50 D（平均增加<0.25 D，p=0.63）。巩膜扭转度与 150μm（r=0.77，p=0.02）和 250μm（r=0.72，p=0.03）镜片的活体弯曲度呈正相关。使用组平均分割，扭转度>200μm 的眼睛比扭转度<200μm 的眼睛表现出更大的活体弯曲度（所有镜片平均增加 0.40 D，p=0.02），而对于 150μm 的镜片，这种影响最大（增加 0.61 D，p=0.04）。
对于高 Dk 和低模量材料，从 350μm 降低到 150μm 的中心厚度会导致镜片弯曲度增加<0.25 D。扭转度>200μm 与活体镜片更大的弯曲度相关。当有意降低巩膜透镜的中心厚度以增强氧气透过率时，在 15mm 弦长处，对于扭转度>200μm 的眼睛，可能需要定制背面设计以最小化活体弯曲度。
