special Report: Laser eye surgery – A shortsighted solution

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).

Contrast sensitivity is also a major concern for PRK patients. Researchers at Moorfield’s Eye Hospital in London reported that 30 per cent of its PRK patients suffered a loss of contrast sensitivity within two years of surgery (Refractive Surgery Symposium, London 2001) – and the same symposium heard that half of all LASIK patients suffered a similar loss, one year after surgery.

The LASIK technique can cause the cornea to weaken in up to 40 per cent of all cases (Lancet, 2003; 361: 1225-6) and, sometimes, the weakened cornea resumes its original shape – so the myopia returns.

One study reported on a variety of complications following LASIK surgery. Of the 24 cases, 13 of the complications occurred during the procedure, and the rest afterwards. The technique, the researchers concluded, could result in serious complications that can lead to visual loss (Eur J Ophthalmol, 2003; 13: 139-45).

Patients may also have to go through a second, corrective operation. In one study of 1306 LASIK patients, over 10 per cent had to have a second operation, a likelihood that increases with age, the degree of initial correction and the extent of astigmatism (Ophthalmology, 2003; 110: 748-54).

As with PRK, postoperative infection is also a concern for the LASIK patient. One study found that keratitis could occur up to 450 days after surgery, and was serious enough to threaten vision (Ophthalmology, 2003; 110: 503-10).

The US Food and Drug Ad-ministration (FDA) is equally unsure of the LASIK technique. According to its website (www. fda.gov), LASIK is ‘an option for risk takers’.

LASEK is a newer technique, so there are fewer studies into its efficacy and safety. However, one recent study from Japan urges caution. After studying the progress of 42 LASEK patients, the researchers reported postoperative complications such as pain, delayed recovery of visual sharpness and corneal haze (Nippon Ganka Gakkai Zasshi, 2003; 107: 249-56).

Compared with PRK, LASEK may result in less discomfort in the early postoperative period, faster visual recovery and less haze, but these claims, made by LASEK proponents, need to be vindicated in long-term trials, say researchers at the University of Washington (Semin Ophthalmol, 2003; 18: 2-10).

In general, complications that can develop after any of these three procedures have included:

* Eye infections (Ophthalmology, 2003; 110: 743-7; J Cataract Refract Surg, 2002; 28: 722-4; J Cataract Refract Surg, 2001; 27: 471-3)

* Dry eye with compromised tear function (Am J Ophthalmol, 2001; 132: 1-7)

* Strabismus (‘cross-eyes’) (Yonsei Med J, 2000; 41: 404-6)

* Detached retina (Am J Ophthalmol, 1999; 128: 588-94)

* Macular damage (Am J Ophthalmol, 2001; 131: 666-7)

* Vision disturbance due to optic nerve damage (Am J Ophthalmol, 2000; 129: 668-71)

* Irregular astigmatism (a misshapen cornea, causing blurred or distorted vision) caused by surgical complications (Rev Optom, May 1999)

* Impaired night vision and loss of contrast sensitivity, making it hard to see objects against a similarly coloured background (Med Post, 8 June 2000)

* Long-term weakening and thinning of the cornea, leading to a risk of further myopia (Ophthalmology, 2001; 108: 666-72).

Corneal weakening and corneal distortion are ‘serious’ complications, according to Dr Jory. They cause myopia that, in some cases, becomes progressively worse. ‘No one knows the rate of risk or the timescale,’ he says.

With more and more ‘walk-in’ laser-surgery centres opening up, the emphasis is on the benefits; very few mention the possible risks either in their advertisements or during the face-to-face consultations before the operation.

The Advertising Standards Authority, the UK’s advertising watchdog, upheld complaints against misleading advertising for LASIK surgery which had been produced by Boots, Maxivision and Optimax, some of the leading players in this lucrative field.

Such a misleading approach was a major concern of the patients, according to a poll conducted by HealthWhich? earlier this year. Some complications that doctors deemed ‘minor’ can seriously affect people’s lives and jobs. One patient complained she could no longer drive and now fails to recognise people who are just 10 feet away. But because she can still read an eye chart, her problem is not considered significant, the poll said.

Some patients whose lives have been ruined by eye surgery have taken on the task of providing a health warning to potential patients, and also provide help to those already affected. The Surgical Eyes Foundation (website: http://www.surgicaleyes.org) is a US-based support group for people with ‘longer-term complications from refractive surgery’. Their aim is ‘to restore quality of life to the thousands who suffer from complications of . . . refractive surgeries’.

Others are much more militant. In the UK, the Medical Defence Union, the biggest insurer of British doctors, said claims against surgeons performing laser eye operations are soaring – mainly because the expectations of the patients don’t match their results. The MDU said doctors needed to warn patients of the possibility of an ‘imperfect result and other complications’ before obtaining the appropriate consent for the procedure (The Guardian, 26 May 2003).

Unrealistic expectations, or perhaps expectations that have been put in the patient’s mind by advertisements or during the preoperative discussions, could be at the heart of the issue. Even if you are among those who suffer no reactions or complications after surgery, you are still likely to need to wear glasses for some tasks, eye surgeon David Gartry told the BBC News (26 May 2003).

Quality of treatment can vary enormously from one clinic to another. Yet, this information is rarely, if ever, made available to patients choosing where to have their treatment.

Extraordinarily, any currently registered doctor can offer laser eye surgery without the need for any special, formal qualifications. In the main, surgeons receive just two or three days of training at best – and then go on to develop and perfect their skills on you, the patient. Britain’s Royal College of Ophthalmologists recommends that refractive surgeons should be fully trained ophthalmologists and should have undergone additional specialist training; they suggest that prospective patients should ask about this when enquiring about surgery. Laser eye surgery is an immature technique that is still being developed, and one that is being carried out by surgeons who are still learning their craft.

Surgery: what’s involved
Lasers have been used in eye surgery for some time, but they have only been in widespread use since the beginning of the 1990s. Before that time, the eye surgeon needed supreme skill and confidence with a scalpel.

When lasers are used to treat myopia (shortsightedness), the shape of the cornea is finely sculpted to allow the eye to focus better. The central part of the cornea is flattened, which brings the focal point of the eye closer to the retina, allowing distance vision to be improved. The surgery removes microscopic amounts of tissue from the outer surface with a cool, computer-controlled ultraviolet beam of light. The beam is so precise that it can cut notches in a strand of human hair without breaking it. Each pulse can remove 39 millionths of an inch of tissue in 12 billionths of a second.

All eye surgery is carried out under local anaesthetic, given as eyedrops. It is an outpatient procedure that takes just a few minutes to perform. Patients are typically able to return to their daily routines within one to three days – if all goes according to plan.

Before the procedure begins, the patient’s eye is measured to determine the degree of visual problem, and a map of the eye’s surface is constructed. The required corneal change is calculated based on this information, and is then entered into the laser’s computer.

Patients who elect for LASIK surgery rarely feel pain during the procedure. The doctor will have you lie down, then make sure the eye is directly under the laser. (One eye is operated on at a time.) A kind of retainer is placed over your eye to keep your eyelids open. This has a suction ring that keeps your eye pressurised, which is important in LASIK for allowing the surgeon to cut the corneal flap. The surgeon uses an ink marker to indicate where the flap should be. The cut is then made with the microkeratome. During the procedure, you won’t see the flap being cut as it is very thin.

The surgeon uses a computer to adjust the laser to your particular prescription. You will be asked to look at a target light for a short time while he/ she watches your eye through a microscope and the laser sends pulses of light to your cornea. With some lasers, it is critical that your eye remains fixated on the target light to obtain the best results. Other lasers are equipped with a special tracking device that follows your eye even if it moves.

The laser light-pulses will then painlessly remove tissue. You’ll hear a steady clicking sound when the laser is in operation. You’re also likely to smell a mildly acrid odour from the tissue being removed. The higher your prescription, the more time the operation takes. The surgeon has full control of the laser and can turn it off at any time.

When the procedure is finished, you will rest for a little while. If you’re having both eyes done on the same day, the surgeon will probably do the other eye after a short period of time. Some people choose to have their second eye done a week later.

The doctor may prescribe medication for any postoperative pain, but many people feel no more than mild discomfort after LASIK, whereas painkillers are often prescribed after a PRK procedure.

After the procedure, you will be advised to take proper rest. What occurs after the surgery can affect your vision just as much as the operation itself.

You may be able to go to work the next day, but many doctors advise a couple of days of rest instead. They also recommend no strenuous exercise for up to a week afterwards, as this can traumatise the eye and affect healing. Avoid rubbing your eye as there is a chance of dislodging the corneal flap.

Laser eye surgery is costly and, at present, not normally available on the National Health Service in the UK or under most health-insurance schemes in the US.

A straw poll of clinics revealed variable prices – most charging upwards of £1200 per eye, or more in the small number of centres offering the more advanced wavefront technology (see box, p 3). In the US, the Los Angeles Times reports a typical price of between $1500 and $2000 per eye. Potential patients need to check whether the prices include aftercare, and any necessary repair or retreatment in case of disappointing results.
Heather Welford, with additional reporting by Bryan Hubbard

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Written by What Doctors Don't Tell You

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