Lei H, Schuchard R A
Department of Ophthalmology, University of Missouri Kansas City School of Medicine, Kansas City 64108-2634, USA.
Invest Ophthalmol Vis Sci. 1997 Aug;38(9):1812-8.
Using a scanning laser ophthalmoscope, it was found that some patients with relative central scotomas reliably used two different preferred retinal loci (PRLs) at different stimulus illuminances. This article describes adaptations in a patient's PRL for fixation when dimming the stimulus increased the relative scotoma size.
Twenty-eight patients with macular diseases had their dense and relative macular scotoma borders mapped with the scanning laser ophthalmoscope. The high-illuminance PRL (PRLhi) and low-illuminance PRL (PRLlo) were operationally defined as the PRLs that patients used to fixate a high or low illuminance stimulus, respectively. The PRLs' abilities to do visual tasks and their characteristics at the corresponding illuminances were assessed.
The PRL consistently shifted between the PRLhi and the PRLlo as the stimulus illuminance was changed. Brightness permitting, the visual system prefers to use the PRLhi with generally better performance in visual function such as fixation stability. There were no significant differences between the PRLhi and the PRLlo in pursuit and saccadic abilities, when assessed by subjective ratings. The illuminances that induced shifting ranged from 106 to 3437 trolands. The PRLhi was always located within an area of relative scotoma, usually at the fovea or just outside a dense scotoma. The PRLlo was located in relatively healthy retinal area, and usually below or to the left of the PRLhi in the visual field.
In the visual system, two well-defined PRLs can develop when visual function is adapting to maculopathy, with the use of each depending on the brightness of objects used in visual tasks. Rehabilitation and treatment strategies should consider the existence of multiple PRLs.
通过扫描激光检眼镜发现，一些患有相对性中心暗点的患者在不同的刺激照度下可靠地使用两个不同的 Preferred retinal loci（PRL，最佳视网膜位点）。本文描述了在刺激光变暗导致相对暗点大小增加时，患者用于注视的PRL的适应性变化。
使用扫描激光检眼镜对28名黄斑疾病患者的致密性和相对性黄斑暗点边界进行了测绘。高照度PRL（PRLhi）和低照度PRL（PRLlo）在操作上分别定义为患者用于注视高照度或低照度刺激的PRL。评估了PRL执行视觉任务的能力及其在相应照度下的特征。
随着刺激照度的变化，PRL在PRLhi和PRLlo之间持续切换。在亮度允许的情况下，视觉系统更倾向于使用PRLhi，其在诸如注视稳定性等视觉功能方面通常表现更好。通过主观评分评估时，PRLhi和PRLlo在追踪和扫视能力方面没有显著差异。导致切换的照度范围为106至3437托兰。PRLhi始终位于相对性暗点区域内，通常位于中央凹或致密暗点之外。PRLlo位于相对健康的视网膜区域，在视野中通常位于PRLhi的下方或左侧。
在视觉系统中，当视觉功能适应黄斑病变时，可以形成两个明确的PRL，每个PRL的使用取决于视觉任务中物体的亮度。康复和治疗策略应考虑多个PRL的存在。
