The "purse string suture" is used to make large, non-reacting pupils smaller, in people who are greatly disturbed by excess light (photophobia) and whose eyes are suitable for this surgery and patients that accept the risks of the surgery (infection, bleeding, increased difficulty of seeing the retina, macula, cornea damage, unequal pupils). The pupil does not react and of course is NOT the same size as the other pupil. It is not good for diabetics, people with retina pathology where good visualization of the retina is needed. It is an infrequent operation and most eye surgeons have no experience with it. Each large community or university usually has a cornea/refractive/cataract/IOL surgeon that specializes in post operative complications you will need to find that person