What Can Cause a Fixed Pupil?
JAN 19, 2024
Question:
What type of trauma can cause a fixed pupil? Can it be repaired?
Answer:
Trauma to the brain or eye can cause a fixed pupil. Usually this is blunt closed trauma which damages the iris sphincter muscle, which constricts or narrows the pupil in bright light.
Sometimes the pupil may become misshapen or demonstrate decreased movement after intraocular surgery such as cataract removal and corneal transplant and even following retinal procedures from direct manipulation of the iris during the surgery.
If the fixed pupil is due to trauma to the head, eye drops such as pilocarpine can be used to make the pupil smaller. This can be for cosmetic purposes or to improve night vision or daytime glare. Colored contact lenses are often useful in this condition, and may be covered by insurance if this is caused by an injury or disease.
There are operations available—such as a purse-string suture and a colored "artificial iris"—to improve dilation, but none really restore the natural function. We need a mobile pupil to dilate at night to let in more light and constrict during the day to prevent excess light from entering the eyes.
This question was originally answered on July 11, 2013.