Yes a large non-reactive or poorly reactive pupil is common after retinal detachment surgery especially if encircling bands are placed around the eye. The mechanism is damage to the long nerves that bring the contricting impulses to the pupil. These run in the white part of the eye and these cannot be identified and may be damaged by cryopexy, diathermy, sutures, constricting the eye. A blown pupil can really occure with most any type of eye surgery including cataract and corneal transplants.
Some improvment may occur with time but my experience is that at 6 months if it hasn't got better it isn't going to improve anymore. Options include using weak solutions of pilocarpine to constrict the pupil. That will make it smaller (usually but not always) but it won't react (get bigger or smaller).
If totally incapacitation there are special contact lens that contain an artifical iris and a small pupil. There is a surgical procedure that can stitch the pupil smaller bt it won't dilate and makes the back of the eye hard to see. There is a special artifical pupil that is used in cases where the eye is born without an iris (aniridia) but I do not know if it will help moderately dilated pupils.
JCH III MD
By "blown pupil" I understand that to mean a pupil that remains dilated. In June I had a vitrectomy for a detached retina. In September I had another vitrectomy to remove the silicone oil. My doctor says my dilated eye is a side effect of the surgery and "maybe" in time (read: real loooooong time) the iris will return to normal. After the silcone oil was out, the iris closed slightly by a centimeter, but my eye remains dilated. I'm just grateful to have any eyesight in that eye, so if it remains dilated for the rest of my life, it wouldn't bother me. I have noticed that the eye is not as sensitive to light as it was months ago. Maybe the retina in that eye is adapting. BTW, I now await cataract surgery in that eye because of the silicone oil. ~Paul