At the absolute threshold of vision, Hecht, Shlaer and Pirenne estimate that 5–14 photons are absorbed within a retinal area containing ~500 rods. Other estimates of scotopic threshold vision based on stimuli with different durations and focal areas range up to ~100,000 photons. Given that rod density varies with retinal eccentricity and the magnitude of the intrinsic noise increases with increasing stimulus area and duration, here we determine whether the scotopic threshold estimates with focal stimuli can be extended to full-field stimulation and whether summation explains inter-study differences. We show that full-field threshold vision (~1018 mm², 10 ms duration) is more sensitive than at absolute threshold, requiring the absorption of ~1000 photons across ~91.96 million rods. A summation model is presented integrating our and published data and using a nominal exposure duration, criterion frequency of seeing, rod density, and retinal area that largely explains the inter-study differences and allows estimation of rods per photon ratio for any stimulus size and duration. The highest signal to noise ratio is defined by a peak rod convergence estimated at 53:4:1:2 (rods:rod bipolar cells:AII amacrine cells:retinal ganglion cells), in line with macaque anatomical estimates that show AII amacrine cells form the bottleneck in the rod pathway to set the scotopic visual limit. Our model estimations that the rods per photon ratio under full-field stimulation is ~3000X higher than at absolute threshold are in accordance with visual summation effects and provide an alternative approach for understanding the limits of scotopic vision.

在视觉的绝对阈值处，Hecht、Shlaer 和 Pirenne 估计在包含约 500 个视杆的视网膜区域内吸收了 5-14 个光子。基于具有不同持续时间和焦点区域的刺激的其他暗视阈值估计范围高达约 100,000 个光子。鉴于视杆密度随视网膜偏心率而变化，并且固有噪声的幅度随着刺激面积和持续时间的增加而增加，在这里我们确定是否可以将具有焦点刺激的暗​​视阈值估计扩展到全场刺激，以及求和是否解释了研究间的差异. 我们展示了全视野阈值视觉（~1018 mm ², 10 ms 持续时间）比绝对阈值更敏感，需要在约 9196 万个棒上吸收约 1000 个光子。提出了一个总和模型，整合了我们和已发布的数据，并使用了标称暴露持续时间、标准视觉频率、视杆密度和视网膜面积，这在很大程度上解释了研究间的差异，并允许估计任何刺激大小和持续时间的每光子比率的视杆. 最高信噪比由估计为 53:4:1:2 的峰值杆收敛定义（杆：杆双极细胞：AII 无长突细胞：视网膜神经节细胞），与显示 AII 无长突细胞形成的猕猴解剖估计一致视杆通路中的瓶颈设置暗视极限。