This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Conjunctiva, Subject name: Ophthalmology
What is the most common problem following surgical treatment of pterygium? 
Select and explain. 
A. Recurrence, B. Corneal ulceration, C. Astigmatism, D. Scleral scarring
A: Recurrence
Answer: A: Recurrence 
Explanation: Recurrence of the pterygium after surgical excision is the main problem (30-50%). However, it can be reduced by any of the following measures: Transplantation of pterygium in the lower fornix (McReynold's operation) is not performed now. Postoperative beta irradiations (not used now). Postoperative use of antimitotic drugs such as mitomycin-C or thiotepa. Surgical excision with bare sclera. Surgical excision with free conjunctival graft taken from the same eye or other eye is presently the preferred technique. In recurrent recalcitrant pterygium, surgical excision should be coupled with lamellar keratectomy and lamellar keratoplasty. ref: A K KHURANA OPHTALMOLOGY,E4, Page-81