Why are my pupils so naturally large?
SEP 06, 2023
I've always had larger pupils. They’re so large that they never have to be dilated to look behind when my eyes are examined. I have light sensitivity and without sunglasses on a sunny day I will get massive headaches. Will this cause harm in the long run? Is there a reason why I have this and no one else in my immediate family does?
The pupil size is closely regulated by muscles in the iris. They expand and contract constantly to allow a certain amount of light into the eye. Certain conditions and medications can alter the function of these muscles and lead to abnormally dilated or constricted pupils. In absence of these causative factors, a patient's normal pupillary size can range between 2mm and 8mm in size. A patient may be more light-sensitive if their natural pupillary size is very large and allows more light into the eye. Under normal conditions, more light entering the eye may be uncomfortable but it’s not harmful. Some people have taken this too far, for example staring at the sun during solar eclipses, and developed a blinding condition called solar retinopathy where the retina may be damaged.
This question was originally answered on Nov. 22, 2014.