What Can Cause a Fixed Pupil?

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 the pupil — or one of the pathways in the brain which controls it. Occasionally, this occurs after intraocular surgery such as cataract removal and corneal transplant and even following retinal procedures. If the injury is in the head, eyedrops 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. See your ophthalmologist for a thorough examination and possible trial prescription. Colored contact lenses are often useful in this condition, and may be covered by insurance if this is caused by an injury or disease.

Finally, there are operations available to improve the 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. A purse-string suture can be used and, more recently, a colored "artificial iris" can be placed inside the eye.