The Short Version
This claim is a widely debunked myth. Multiple credible medical and optometric sources — including the Canadian Association of Optometrists, Prevent Blindness, and University of Utah Health — confirm that reading in low light may cause temporary eye strain, discomfort, or headaches, but does not cause permanent damage to eyesight. These symptoms resolve with rest. No credible clinical evidence supports the idea that dim-light reading leads to lasting structural harm to the eyes.