The surgeries were performed last week at a mass surgery organised by a charity in Haryana state's Ambala district.
Officials said the patients realized they were blind after they removed the bandages from their eyes.
Ambala's chief medical officer Vinod Kumar Gupta said the organisation, Sarv Kalyan Sewarth Samithi, did not have government permission to hold the surgery.
"We are on the ground right now to inspect the hospital and our medical teams are collecting details from the patients," Gupta told AFP.
"So far we only know of 15 patients who were operated on and their surgeries botched. We know that when they came to the government hospital they had lost vision in the eye which had been operated upon."
This type of incident is not uncommon in India. A few days ago, 14 people also lost their sight after undergoing the same procedure in western India because hospital staff failed to sterilise the equipment properly.