As more Singaporeans buy their spectacles - sight unseen - on the Internet, the Government has issued tighter rules on who can do so.

Only those aged 16 and above can make the purchase, and they must have a valid prescription from an optometrist registered with the Optometrists and Opticians Board.

The new guidelines for online sales of prescription glasses, announced on the board's website on Tuesday, are to "ensure that proper assessment and management are in place to safeguard the interest of the public against dubious sources of sales". Previously, there were no restrictions.

The board, an official governing body in the Ministry of Health, also issued advisories for optical practitioners, retailers and consumers.

To get a prescription that will allow one to buy glasses online, a consumer has to be aged 16 and above, with myopia of below 600 degrees and astigmatism below 200 degrees.

A valid prescription has to include, among other conditions, the consumer's date of birth and identity card number, the date the prescription expires - usually not longer than two years - and a written assessment that the consumer does not have any existing organic eye disease or systemic medical condition that will affect vision.

Online retailers must be a business registered in Singapore, with a physical outlet that provides after-sales services such as adjustment of spectacles.

Practitioners who do not follow these guidelines may be subject to disciplinary action, as it may be regarded as professional misconduct, said the board.

The Singapore Optometric Association, an industry body of optometrists, said it had raised concerns to the board over the growing trend of consumers purchasing spectacles and contact lenses online.

These carry risks such as the absence of appropriate eye exams and reviews, and the lack of after-sales care, said one of the association's councillors, Ms Chui Wen Juan.

A comprehensive eye exam can determine if visual and eye health problems exist due to refractive error - blurred vision due to light not being focused correctly on the eye - or because of eye disease or developmental issues, said Ms Chui.

Retailers said the guidelines may not be practical. "Some optometrists might not be too keen to issue patients with their prescriptions, especially if they know the patients are going to make their spectacles with other companies," said Mr Edwin Tay, business manager of Mimeo The Optical Shop.

Online optical shops may also have difficulties validating the authenticity and accuracy of the prescription provided by the patients, he said. "At the moment, information sharing among different optical shops may not be liberal due to business interests," he added.

Optical chain Owndays, which does not sell spectacles online, said it is exploring how it can do so while keeping to the guidelines.

"The guidelines help to uphold the standard and professionalism of the optical industry," said its managing director, Mr Umiyama Takeshi.

A report by Euromonitor International found that last year, only 2 per cent of spectacles sold here were bought online. But this is expected to grow as people seek novelty and competitive prices, it added.

Mr Bernard Yang, managing director of Nanyang Optical, said a bigger problem is the sale of contact lenses online. "The sale of contact lenses is more of a real problem since they are placed directly onto the eye," he said.