Laser eye surgery was supposed to be the great saviour for all glasses-wearers, and was science’s answer to most of the common sight problems. But, already, the hype and hope are giving way to growing concerns over the safety and effectiveness of the various techniques, and patients are proving to be somewhat elusive just as the surgery is being offered on every high street.
In the US, a growing number of consumers is questioning the procedure, and its popularity is apparently waning. At its peak in 2000, 1.42 million Americans underwent the surgery, but figures for the following two years saw a significant drop to 1.31 million in 2001 and 1.15 million in 2002. Profits and share prices of the medical chains performing the operation tumbled as a result (International Herald Tribune, 31 January 2003). In the UK, around 100,000 people undergo the procedure each year.
Nevertheless, patients’ concerns are well placed. Researchers at the New Jersey Medical School discovered that as many as one in five of the patients in their study of 1306 patients needed to undergo retreatment to repair or enhance the first one (Ophthalmology, 2003; 110: 748-54).
One of the major concerns of ophthalmologists is the sudden loss of contrast sensitivity - the ability to distinguish objects in poor light - after surgery. This problem surfaced in 1996 when researchers at Tubingen University in Germany reported that three-quarters of the patients who had undergone photorefractive keratectomy (PRK) surgery for myopia over the previous 10 years had such poor contrast sensitivity that they failed federal German night vision standards (ASCRS Symposium, June 1996).
The London Centre for Refractive Surgery has reported similar problems. After hearing of the German findings, the centre recalled all patients treated with an Excimer laser and found that 56 per cent (36 of 54 patients) also had greatly reduced contrast sensitivity (Lancet, 2003; 361: 1225-6).
This loss of sensitivity appears to be permanent and untreatable, says Dr William Jory, consultant ophthalmologist at the London Centre for Refractive Surgery.
These findings have been supported by a further German study (ESCRS, Brussels, 2000) and one from Canada (Can J Ophthalmol, 2000; 35: 192-203). The Canadian federal government in Ottawa has now advised all provincial governments to test patients’ night vision after surgery before a driver’s licence is issued.
Advocates of laser eye surgery argue that many of these safety issues relate to the PRK technique, which has since been superseded by LASEK (laser subepithelial keratomileusis), a modification of PRK, and by LASIK (laser in situ keratomileusis), now probably the most popular form of laser eye surgery (Semin Ophthalmol, 2003; 18: 2-10).
With PRK, the surgeon applies the laser beam directly to the cornea (the transparent tissue covering the front of the eye), and ‘shaves’ and reshapes it. LASIK uses a special knife to lift a flap of tissue from the surface of the cornea to reveal the corneal bed (stroma). The laser works on this tissue, then the flap is replaced. The LASEK technique detaches the outermost layer (epithelium) of the cornea, and reshapes the corneal surface with the laser. The epithelium is then returned to its normal position.
There has been a range of concerns about the PRK technique, but one that is rarely aired is the possibility of postoperative infection. One study reviewed the records of 12 PRK patients who developed infectious keratitis, which can result in corneal ulceration. The researchers recommended that just-in-case antibiotics be given to all PRK patients before surgery (Ophthalmology, 2003; 110: 743-7).