Department of Optometry and Visual Science, School of Health and Psychological Sciences, City, University of London, Northampton Square, London, United Kingdom.
Brien Holden Institute of Optometry and Vision Sciences, L. V. Prasad Eye Institute, Banjara Hills, Hyderabad, Telangana, India.
Transl Vis Sci Technol. 2023 Dec 1;12(12):21. doi: 10.1167/tvst.12.12.21.
The purpose of this study was to determine changes in spatial and depth vision with increasing severity of keratoconus and to model the structure-function relationship to identify distinct phases of loss in visual function with disease severity.
Best-spectacle corrected, monocular high-contrast visual acuity, contrast sensitivity function (CSF) and stereoacuity of 155 cases (16-31 years) with mild to advanced bilateral keratoconus was determined using standard psychophysical tests. Disease severity was quantified using the multimetric D-index. The structure-function relationship was modeled using linear, positive exponential, negative exponential, and logistic nonlinear regression equations.
The logistic regression model explained the highest proportion of variance for spatial vision, without bias in the residual plots (R2 ≥ 66%, P < 0.001). Visual acuity showed a distinct ceiling phase and a steeper loss rate with increasing D-index (1.8 units/D-index) in this model. The area under the CSF lacked this ceiling phase and had a shallower loss rate (0.28 units/D-index). Stereoacuity loss with D-index was poorly explained by all models tested (P ≤ 0.2). Cases with lower and bilaterally symmetric D-index had better stereoacuity (181.6-376 arc seconds) than those with higher D-index (>400 arc second); both were significantly poorer than controls (approximately 30 arc second).
Vision loss in keratoconus varies with the visual function parameter tested. Contrast sensitivity may be an earlier indicator of spatial vision loss than visual acuity. Depth perception is significantly deteriorated from very early stages of the disease.
The study outcomes may be used to forecast longitudinal vision loss in keratoconus and to apply appropriate interventions for timely preservation/enhancement of vulnerable visual functions.
本研究旨在确定圆锥角膜严重程度增加时空间和深度视力的变化，并建立结构-功能关系模型，以确定疾病严重程度与视觉功能丧失之间的不同阶段。
使用标准心理物理测试，对 155 例（16-31 岁）轻至重度双侧圆锥角膜患者的最佳矫正单眼高对比度视力、对比敏感度功能（CSF）和立体视锐度进行了测定。使用多指标 D 指数量化疾病严重程度。使用线性、正指数、负指数和逻辑非线性回归方程对结构-功能关系进行建模。
逻辑回归模型解释了空间视觉的最大比例方差，残差图无偏差（R2≥66%，P＜0.001）。在该模型中，视力表现出明显的上限阶段和随着 D 指数增加而更快的损失率（1.8 个单位/D 指数）。CSF 的面积没有这个上限阶段，损失率较浅（0.28 个单位/D 指数）。所有测试模型对立体视锐度损失的解释都较差（P≤0.2）。D 指数较低且双侧对称的病例立体视锐度（181.6-376 弧秒）优于 D 指数较高的病例（＞400 弧秒）；两者均明显低于对照组（约 30 弧秒）。
圆锥角膜的视力损失因所测试的视觉功能参数而异。对比敏感度可能是视力丧失比视力更早的指标。从疾病的早期阶段开始，深度知觉就会明显恶化。
研究结果可用于预测圆锥角膜的纵向视力丧失，并适时应用适当的干预措施来保护/增强脆弱的视觉功能。
