Mr Kerr is one of the optometrists who are opposed to selling contact lenses by mail order. The General Optical Council(GOC) recently successfully prosecuted the company Vision Direct for selling them in this way The company was ordered to pay pounds 50,000.
The case has provoked controversy, with optometrists arguing that selling contact lenses by post could potentially damage people's eyes, and others arguing that opticians are wanting to protect their own mark-up rather than provide cheaper lenses. In several countries, such as the US and Denmark, mail order lenses have been operating for years - with, say supporters, no increase in eye problems.
Steffan Rygaard, of Vision Direct, has said that he intends to keep on selling cut-price lenses, though he may have to sell through an American website, outside the jurisdiction of the GOC.
"The consumer demand is unbelievable," he says. "Every 15 minutes someone is ringing me up with an order. I've turned down pounds 7,000-worth ... since the court case."
Rygaard supplied lenses to customers who already had prescriptions. "I would send them reminders twice a year to say `go for an eye test and send us a copy of your prescription and then we can carry on'."
But consultant ophthalmologists fear that mail order lenses will lead to laxity in the supervision of contact lens wearers, resulting in more infections which, though rare, can have devastating consequences.
About five in every 10,000 wearers of soft lenses, the most popular kind, require treatment each year. This rises to 20 per 10,000 for extended- wear lenses.
"There is a very small number of complications," said Lyndon Jones, an optometrist who has published research papers on disposable lenses. "The problem is, they are generally the sort of complications you are given no warning over until it is too late. If you have regular check- ups, complications can be picked up. The major problems include ... the blood vessels travelling from the white of the eye to the cornea being starved of oxygen. They end up growing into the cornea, interfering with vision."
Infection and oxygen deprivation are the principal problems for contact lens wearers. The soft lenses cover most of the cornea (the transparent surface of the eye) preventing air getting to it. An ill-fitting lens can aggravate the problem of oxygen deprivation.
"In the most extreme cases - which are rare - you could end up with acanthamoeba keratatis, which causes scarring of the cornea and can result in the need for a corneal graft," says Mr Kerr.
But Mr Rygaard questions whether going to an optician provides any more protection than buying his lenses by mail order. "If you are buying lenses for the first time you are told how to use them and you have your eyes tested, but for repeat purchases that's not the case. You pick them up from the receptionist and walk out of the shop. Then if you have any problems you go back ... We don't do anything different from that. The other thing is, the optician gives you a box of lenses. You don't test each and every one of them before you go out of the shop."
Mr Kerr, on the other hand, says: "I sincerely believe that potential problems are greatly increased if there is not clinical supervision.
"We are all a bit careless," he adds. "With medical compliance only 50 per cent of us take a full course of tablets. So with lenses; people may not change them at the correct intervals, or wear them much longer than they should, or forget how to clean them properly - and thus end up with a problem which may be asymptomatic, but ends up causing ocular damage."
Mr Jones agrees, saying that the number of people suffering complications would increase if lenses were sold by post.
Mr Rygaard, on the other hand, believes that eventually the GOC will have to acknowledge that mail order lenses cannot be outlawed.
"You can't stop it happening," he says. "The GOC may have beaten me in court, but they haven't won."