When shining a light in your eye, doctors are evaluating your eye’s response to the light. In healthy eyes, the pupils will maintain their round shape, but should shrink when stimulated by the light (via WebMD). Additionally, the light will allow your doctor to get a better look at the color of your eyes. According to experts at the University of Rochester Medical Center, red eyes may indicate possible irritation or infection, and eyes that are yellow in color can be a symptom of other health conditions, such as liver issues.
Shining a light in your eye through the use of different tools allows an optometrist to further assess your health by looking for any possible blockages in the eye (via Progressive-Glasses.com). Any traces of cloudiness in the eye where it should otherwise appear clear can indicate abnormalities, such as a cataract. This information can be helpful for a doctor in determining a proper course of treatment. Some people experience improvement in their vision following a glasses prescription, while others may require surgery.
Should any problems be detected during the course of the exam, doctors will want to identify any other possible health conditions. WebMD states that an abnormal reaction to the light test could be an indication of diabetes or glaucoma, while the University of Rochester Medical Center suggests nerve communication between the brain and the eye could also potentially be the source of the problem.