How does convergence of many rod signals increase vision sensitivity outside the fovea?

Outside the fovea, vision sensitivity is increased through the convergence of many rod signals onto single bipolar and ganglion cells. This anatomical arrangement creates large receptive fields that allow for spatial summation, where the effects of light stimuli are cumulative.12

Because these signals converge, a weak light stimulus spread across approximately 1,000 rods becomes as effective as a stronger stimulus concentrated on a smaller area. This cumulative effect lowers the threshold required to trigger a response, making the retina significantly more sensitive to dim light in areas outside the fovea. While this convergence is essential for high sensitivity in low-light conditions, it also results in lower visual acuity, as the large size of the receptive field limits the ability to resolve fine detail.12