The patient underwent a second operation to remove the object.

Dr Loretta Yam, chief executive of Hong Kong East group of hospitals, said it was a 'very rare accident' which had not involved any human blunder.

During the surgery on June 18, she said, doctors had applied six sponges soaked in anti-cancer liquid medicine on the incision in the eye for a few minutes.

It was a common practice to reduce the chance of growth of scar tissue.

All procedures had been followed to account for all objects used during the surgery.

'We suspect that the object we found in the patient's eye was a tiny part of the sponge, which somehow dropped off during the surgery and was hidden somewhere in her eye,' Yam said. 'It's too small to be spotted with the naked eye.'

The patient had not experienced any discomfort, had accepted the hospital's apology and had been discharged on June 20.

The sponge involved in the accident was commonly used in local public hospitals. Although the incident was the first of its kind known to the authority, Yam said different replacements had been sought overseas in a bid to prevent the accident from happening again.

In addition, the hospital had reminded all frontline staff to be wary when using such sponges.

Secretary for Food and Health York Chow Yat-ngok said surgeons, doctors and other medical staff should not only follow all required procedures, but needed to follow every step with great care.

The latest issue of 'Hospital Authority Risk Alert', an authority publication aimed at strengthening reporting and monitoring of adverse incidents in public hospitals, details recent incidents.

They include laser treatment given to the wrong patient, insertion of a chest drain into the wrong baby, extraction of a wrong tooth and disconnection of portable ventilators during transport of critically ill patients.

However, Chow said transparency in dealing with medical accidents had improved.

'The Hospital Authority has a set of guidelines in this area,' he said. 'It aims to help citizens and patients to understand the risks in medical treatment. Yet more importantly, it is to urge relevant medical staff and hospital management to take up responsibility.

'I believe we are capable of handling medical accidents effectively with the management culture we have today.'

The Hong Kong East group of hospitals revealed yesterday its plan for the 2009/10 year, announcing an expansion of daytime chemotherapy services to treat more cancer patients and set up a psychiatric triage clinic to shorten waiting times for non- urgent psychiatric patients.

With rapidly growing demand for chemotherapy services, the Pamela Youde Nethersole Eastern Hospital is to open two more rooms dedicated to daytime chemotherapy infusion, which will begin operations within the first quarter of next year. By then, the hospital will be able to treat 26 cancer patients a day, five more per day than this year.

In terms of psychiatric services, the public hospital group has adopted the idea of a triage clinic, a new method to deal with the increasing number of psychiatric patients who do not require urgent treatment.

At the triage clinic, doctors will offer four consultations to non- urgent patients before referring them to general outpatient clinics, psychiatric outpatient clinics or allied health clinics for follow-up attention.

The psychiatric triage clinic, which began operation in August, has reduced waiting times for non-urgent patients before they receive psychiatric treatment from 49 weeks in May to 44 weeks in September.