If you have 20/20 vision in the day at night your vision is

• A. 20/20
• B. 20/100
• C. 20/40
• D. 20/80

Answer: (B)

In low light, vision becomes rod-dominated rather than cone-dominated. Rods are very sensitive to light but resolve details much less sharply, so acuity drops significantly when it’s dark. That’s why daytime sharpness isn’t maintained at night. A common way to express this drop is that your night vision can be around 20/100, meaning you can see at 20 feet what a person with normal daytime vision would need to be at 100 feet to discern. This level can vary with lighting and individual differences, but it reflects the typical decline in acuity after sunset. The other options imply only a small decline or no decline, which doesn’t match how much acuity usually deteriorates in dim conditions.