Vision may be restored by doctors, to at least six of 20 people blinded by botched free cataract surgery in northern India, a government official said on Saturday.
Authorities have suggested poor surgical hygiene may be to blame for the loss of sight after what are normally considered low-risk operations, in the latest scandal to highlight poor medical care in parts of India.
Authorities in India's Punjab state reported 20 confirmed cases of blindness after a medical charity conducted free cataract operations on 157 people in November in Amritsar.
Local media reports, however, say the number of people blinded could range from 30 up to as much as 60.
The cases have raised fresh concerns about the hygiene standards in India's severely stretched health-care services.
The incident comes just weeks after the deaths of 13 women following sterilisation surgery at a camp in central India.
Government officials blamed tainted drugs for the deaths, but an independent report said the women had suffered septicaemia that could have been caused by lack of hygiene.
In the case of those having eye surgery, the organiser of the camp has been arrested on accusations of allegedly running the camp without government permission, police said, while the doctor who performed the cataract operations has been been held for questioning.
"Our preliminary enquiries have indicated the doctor performed more than 30 operations in a single day," Manvinder Singh, a senior Punjab police official, told AFP.
"Technical teams are questioning him (the doctor) on different aspects," Singh said.
Punjab police were seeking to trace every patient operated on at the camp to ascertain the total number of victims.
A government doctor who treated the latest victims on Friday said they had contracted infections after undergoing the cataract surgery on November 4.
"They came to us in a very bad condition... the infection had already spread," Karanjeet Singh told India's NDTV news channel, adding "chances of restoring their eyesight" are as a result much lower.
Volunteer groups and government authorities regularly hold medical camps to treat tens of thousands of poor Indians each year for various ailments.
Authorities said the problem first came to light when victims began coming forward earlier in the week.
Police said there could be more arrests in the cataract case.
"Our police team is leaving for Mathura in neighbouring state of Uttar Pradesh, where the NGO (non-governmental organisation) has its headquarter," Singh said.
"In Mathura, we hope to get the names of all the other people directly responsible for this illegal camp," he said.