Posterior synechiae is something I see very commonly in patients who have inflammation in their eye (called iritis).
When the fluid in the eye becomes inflamed, it can also become sticky.
What happens now is the iris (the colored part of the eye) can start to stick to the front surface of the lens. As the pupil dilates and the iris starts to pull away from the stuck part on the lens, small fragments of the iris can be left behind like in this photo.
If iritis or inflammation in the eye is present, your doctor will usually put in a dilating eye drop. This is to dilate your eye and pull the iris away from the front of the lens so that it can’t get stuck.
I usually use atropine or homatropine, but to get the patient started, I will use cyclopentolate 1% because this is what I have in the office. Then they can pick up their Rx for the longer lasting eye drop.
If you’ve ever had an inflamed eye and wondered why your doctor dilated your eye, now you know!