Under Scotopic vision, visual acuity decreases to what value?

Under Scotopic vision, visual acuity decreases to what value?

• A. 20/40
• B. 20/20
• C. 20/60
• D. 20/200

Answer: (D)

Scotopic vision relies on rods, which are highly sensitive in low light but provide much poorer detail than cones. Many rods funnel into fewer ganglion cells, so the image they form has a larger receptive field and reduced spatial resolution. In bright light, vision is sharp (about 20/20). In dim lighting, acuity drops significantly, commonly to around 20/200, which is the threshold often used to describe legal blindness in low-light conditions. So, under Scotopic vision, the best way to describe the acuity is 20/200—the detail you can resolve at 20 feet in dim light is what a person with normal vision would resolve at 200 feet. The other values reflect sharper detail that isn’t maintained in very low light.

Scotopic vision relies on rods, which are highly sensitive in low light but provide much poorer detail than cones. Many rods funnel into fewer ganglion cells, so the image they form has a larger receptive field and reduced spatial resolution. In bright light, vision is sharp (about 20/20). In dim lighting, acuity drops significantly, commonly to around 20/200, which is the threshold often used to describe legal blindness in low-light conditions. So, under Scotopic vision, the best way to describe the acuity is 20/200—the detail you can resolve at 20 feet in dim light is what a person with normal vision would resolve at 200 feet. The other values reflect sharper detail that isn’t maintained in very low light.