Lakshmi Marella Bhagya, Conway Miriam L, Vaddavalli Pravin K, Suttle Catherine M, Bharadwaj Shrikant R
Brien Holden Institute of Optometry and Vision Sciences, L V Prasad Eye Institute, Road 2 Banjara Hills, Hyderabad 500034, Telangana, India; Prof. Brien Holden Eye Research Centre, L V Prasad Eye Institute, Road 2 Banjara Hills, Hyderabad 500034, Telangana, India; Centre for Applied Vision Research, City, University of London, Northampton Square, London EC1V 0HB, United Kingdom.
Centre for Applied Vision Research, City, University of London, Northampton Square, London EC1V 0HB, United Kingdom.
Vision Res. 2024 Nov;224:108486. doi: 10.1016/j.visres.2024.108486. Epub 2024 Sep 18.
Contrast demodulation and phase distortions are exaggerated in retinal images blurred by the higher-order wavefront aberrations of keratoconic eyes. While the performance loss from the former parameter is well understood, little is known about the impact of the latter on visual functions in this disease condition. The present study investigated the impact of phase distortions on the monocular logMAR visual acuity, letter discriminability and random-dot stereoacuity of seventeen visually healthy adults (ten for visual acuity and letter discriminability; ten for stereoacuity and three common to both experiments) using images that were computationally blurred by four different higher-order wavefront aberration profiles of keratoconic eyes that showed significant distortions in the phase spectrum. Participants viewed these images through 2 mm artificial pupils to negate their native ocular wavefront aberrations. The results showed progressive losses in visual acuity and stereoacuity with increasing blur, a third of which could be recovered following phase nullification. Letter discriminability also improved following phase nullification, more so for smaller than larger optotypes. Stereoacuity loss and, consequently, its recovery following phase nullification was more prominent for profiles simulating unilateral asymmetric keratoconus than for profiles simulating bilateral symmetric keratoconus. These results agree with previous reports obtained from blur induced with lower-order aberrations and indicate that a similar trend may be observed for more complex patterns of blur like keratoconus. Overall, both contrast demodulation and misalignment of the local features of the blurred image may contribute to losses of spatial and depth vision in keratoconus. Phase nullification may partially mitigate these losses, thereby allowing the processing of finer spatial details and veridical disparity estimations for improved depth perception.
在圆锥角膜患者高阶波前像差导致模糊的视网膜图像中，对比度解调及相位畸变会被放大。虽然我们对前一个参数导致的性能损失已有充分了解，但对于后者在此疾病状态下对视觉功能的影响却知之甚少。本研究使用通过模拟圆锥角膜患者四种不同高阶波前像差轮廓而经计算模糊处理的图像，这些像差轮廓在相位谱中显示出明显畸变，研究了相位畸变对17名视力正常成年人单眼对数最小分辨角视力、字母识别能力和随机点立体视锐度的影响（其中10名用于视力和字母识别能力测试；10名用于立体视锐度测试，3名参与两个实验）。参与者通过2毫米的人工瞳孔观察这些图像，以消除其自身眼波前像差。结果显示，随着模糊程度增加，视力和立体视锐度逐渐下降，其中三分之一在相位消除后可恢复。相位消除后字母识别能力也有所提高，对于较小视标而言提高幅度大于较大视标。模拟单侧不对称圆锥角膜的像差轮廓相比模拟双侧对称圆锥角膜的像差轮廓，立体视锐度损失及其在相位消除后的恢复更为显著。这些结果与先前关于低阶像差引起的模糊所获得的报告一致，并表明对于像圆锥角膜这样更复杂的模糊模式可能会观察到类似趋势。总体而言，对比度解调以及模糊图像局部特征的错位都可能导致圆锥角膜患者空间和深度视觉的丧失。相位消除可能会部分减轻这些损失，从而允许处理更精细的空间细节并进行准确的视差估计以改善深度感知。
