Brien Holden Institute of Optometry and Vision Sciences, L V Prasad Eye Institute, Hyderabad, Telangana, India.
Prof Brien Holden Eye Research Centre, Hyderabad Eye Research Foundation, L V Prasad Eye Institute, Hyderabad, Telangana, India.
J Vis. 2023 Mar 1;23(3):14. doi: 10.1167/jov.23.3.14.
Optical defocus in human eyes is seldom steady during naturalistic steady-state viewing. It fluctuates by 0.3 to 0.5 diopters (D) from accommodative microfluctuations and by 1.5 to 2.5 D in dysfunctions such as spasm of near reflex, both with ≤2 Hz low-pass frequency spectra. This study observed losses in monocular visual acuity of cyclopleged adults who encountered varying amplitude (0.25-2.0 D) and temporal frequency (0.25-2.0 Hz) combinations of sinusoidal defoci induced using an electrically tunable lens. Visual acuity, recorded for 300-ms flashes of Sloan optotype presentation using the method of constant stimuli, deteriorated with defocus amplitude at a rate steeper for lower than higher temporal frequencies. A template matching model of acuity, incorporating optical and neural low-pass filters, neural noise, and a cross-correlated decision operator, showed the best match with empirical data when acuity was governed by the minimum defocus available during optotype display. This criterion minimized acuity loss for higher temporal frequencies due to the increased probability of zero-defocus encounters within the presentation duration. Other decision criteria such as defocus averaging across the entire or parts of the presentation duration yielded less satisfactory results. These results imply that vision loss in humans encountering broadband time-varying defocus is dictated by the dominant low frequencies, with higher frequencies largely compensated using the least defocus decision strategy.
人眼的离焦在自然状态下很少保持稳定。它会因调节微波动而波动 0.3 到 0.5 屈光度（D），因近反射痉挛等功能障碍而波动 1.5 到 2.5 D，两者都具有≤2 Hz 的低通频谱。本研究观察了使用电调谐透镜诱导的正弦离焦的不同幅度（0.25-2.0 D）和时间频率（0.25-2.0 Hz）组合对单眼视觉成年人的影响。使用恒定刺激法记录了 Sloan 视力表呈现 300 毫秒闪光时的视力，随着离焦幅度的增加，视力下降的速度在较低时间频率下比在较高时间频率下更快。视力的模板匹配模型，结合了光学和神经低通滤波器、神经噪声和交叉相关决策算子，当视力由视力表显示期间可用的最小离焦度决定时，与经验数据的匹配最佳。由于在呈现期间内零离焦的出现概率增加，该标准最小化了较高时间频率的视力损失。其他决策标准，如在整个呈现期间或部分呈现期间对离焦进行平均，会产生不太令人满意的结果。这些结果表明，人眼在遇到宽带时变离焦时的视力损失由主导的低频决定，较高频率主要通过使用最小离焦决策策略来补偿。
