Under low light conditions, do patients typically become more hyperopic or more myopic?

Under low light conditions, do patients typically become more hyperopic or more myopic?

• A. Hyperopic
• B. Myopic
• C. Emmetropic
• D. No change

Answer: (B)

In dim lighting, the pupil expands. A larger pupil lets in more peripheral light and amplifies optical aberrations, especially spherical aberration, while also reducing depth of field. This combination tends to shift the effective focal point forward on the retina for distant objects, producing a slight myopic shift known as night myopia. So, patients typically appear more myopic in low light. Hyperopic shift or no change isn’t supported by the optics of a dilated pupil, and emmetropia would imply no effective shift, which isn’t what happens with dim illumination.

In dim lighting, the pupil expands. A larger pupil lets in more peripheral light and amplifies optical aberrations, especially spherical aberration, while also reducing depth of field. This combination tends to shift the effective focal point forward on the retina for distant objects, producing a slight myopic shift known as night myopia. So, patients typically appear more myopic in low light. Hyperopic shift or no change isn’t supported by the optics of a dilated pupil, and emmetropia would imply no effective shift, which isn’t what happens with dim illumination.