If the pupil is dilated, approximately how much more light can enter the eye?

If the pupil is dilated, approximately how much more light can enter the eye?

• A. 2x
• B. 10x
• C. 100x
• D. 1000x

Answer: (C)

Light entering the eye is determined by the size of the pupil, which acts like an aperture. The amount of light that can pass through isn’t just about the width; it’s about the area of the opening. Area grows with the square of the diameter, so when the pupil dilates, the light entering increases roughly with the square of that change. If the dilation expands the diameter by about tenfold, the area—and thus the light entering—goes up by about 100 times. So, approximately a hundredfold more light can enter the eye with substantial dilation. Smaller increases in diameter yield smaller multipliers, like 2x or 4x, rather than such a large jump.

Light entering the eye is determined by the size of the pupil, which acts like an aperture. The amount of light that can pass through isn’t just about the width; it’s about the area of the opening. Area grows with the square of the diameter, so when the pupil dilates, the light entering increases roughly with the square of that change. If the dilation expands the diameter by about tenfold, the area—and thus the light entering—goes up by about 100 times. So, approximately a hundredfold more light can enter the eye with substantial dilation. Smaller increases in diameter yield smaller multipliers, like 2x or 4x, rather than such a large jump.