Save Sight Institute, Discipline of Ophthalmology, University of Sydney, Sydney, Australia.
Retinal Unit, Sydney Eye Hospital, Sydney, Australia.
Ophthalmic Physiol Opt. 2021 Jan;41(1):157-164. doi: 10.1111/opo.12743. Epub 2020 Oct 16.
Two-colour computerised perimetry is a technique developed for assessing cone- and rod-function at fixed background luminances in retinal disease. However, the state of adaptation during testing is unknown but crucial in the interpretation of results. We therefore aimed to determine the adaptational state of rod- and cone-mechanisms in two-colour perimetry.
Sensitivity to 480 nm (blue) and 640 nm (red) Goldmann size V targets was determined for 10 normal subjects aged 16 to 46 years at 17 locations in the central 60 degrees of the visual field under scotopic conditions and then from -1.5 log cd m to 2 log cd m (white background) in 0.5 log unit steps. Data were fitted with threshold versus intensity (tvi) functions of the form logT = logT + log ((A + A )/A ) .
No clear rod-cone break was observed for 640 nm stimuli. For 480 nm stimuli, transition from rod-detection to cone-detection occurred at mesopic illumination levels, where rod adaptation approached Weber behaviour. Cone detection mechanisms did not display Weber-like adaptation until the background luminance approached 1 log cd.m . Diseases resulting in a "filter effect" - including disorders of the photoreceptors - are therefore predicted to affect sensitivity when rod function is probed with short-wavelength targets under scotopic conditions, but less so under mesopic conditions. Filter effects are similarly anticipated to affect cone function measured using long-wavelength targets under mesopic conditions (e.g., during microperimetry), but less so under photopic conditions.
Asymmetries in adaptation in automated two-colour perimetry are predicted to artefactually favour the detection of losses in rod sensitivity under scotopic conditions and cones under mesopic conditions.
双色电脑视野计是一种用于评估视网膜疾病中固定背景亮度下视锥和视杆功能的技术。然而，测试过程中的适应状态是未知的，但对结果的解释至关重要。因此，我们旨在确定双色视野计中视杆和视锥机制的适应状态。
在暗适应条件下，10 名年龄在 16 至 46 岁的正常受试者在中央 60 度视野的 17 个位置测定对 480nm（蓝色）和 640nm（红色）Goldmann 大小 V 目标的敏感性，然后在 0.5 对数单位的步骤中从 -1.5 对数 cd m 到 2 对数 cd m（白色背景）。数据采用阈值与强度（tvi）函数拟合，形式为 logT=logT+log((A+A)/A)。
对于 640nm 刺激，未观察到明显的视杆-视锥转换。对于 480nm 刺激，在中间光水平下，从视杆检测到视锥检测的转换发生，此时视杆适应接近 Weber 行为。直到背景亮度接近 1 对数 cd.m，视锥检测机制才显示出 Weber 样适应。因此，预计包括光感受器疾病在内的导致“滤光效应”的疾病会影响在暗适应条件下用短波目标探测视杆功能时的敏感性，但在中间光条件下则影响较小。类似地，预计滤光效应会影响在中间光条件下（例如，在微视野计中）用长波目标测量的视锥功能，但在明适应条件下影响较小。
在自动双色视野计中，适应的不对称性预计会人为地有利于在暗适应条件下检测视杆敏感性的丧失和中间光条件下视锥敏感性的丧失。
