Health Notes, February 21st 2010, by Sarah Stacey

Pros and cons of laser eye surgery

A shortsighted reader asks for information about laser eye surgery.  Does it work – and for which vision problems? Is it safe?  What happens?  How do you find a good practitioner?  So I turned to consultant ophthalmic surgeon Professor Charles Clark for information. 

He explains that to see clearly we need to focus light on to the retina at the back of the eye.  This is achieved by two powerful mechanisms: the cornea (the ‘window’ on the front of the eye) and the lens inside the eye.  

The length of the eye from the front of the cornea to the back wall of the ‘sclera’ affects its ability to focus.  The normal eye is about 24mm in length.  If it’s slightly longer, you’re short-sighted, which means you can see clearly close-up but need glasses for distance.   If the eye is slightly smaller than 24mm, you’re long-sighted. 

You obviously can’t change the size of the eye but you can change the way it focuses using a laser which re-shapes the cornea by shaving a tiny area from the centre.  This changes the power of the eye to see and, according to the advertising, may allow you to throw away your glasses or contact lenses. 

There are several different types of lasers – and the technology is constantly evolving – but the most common technique commercially available is called Lasik, which stands for ‘laser in-situ keratomileusis and has been practised in the UK since 1995.  Basically a series of very detailed contour maps are made of the surface of the eye, then a computer calculates the exact amount that needs to be shaved.  The trained surgeon lifts a very thin flap from the surface of the eye to allow the laser to shave a tiny amount, then the flap is replaced.  The laser part takes a fraction of a second, and the whole procedure only a few minutes. 

There are complications in about five per cent of cases.  This can involve over or under correction, so the patient will still have to use glasses or contact lenses.  Many patients have dry eyes after the procedure and need eye-drops for about six months, others may experience hazy vision or a slight ‘halo’ effect with a ring of light around lights at night (this may be long term).   

It’s important to realise that the laser will not correct vision permanently because the lens in the eye changes with age, so as you grow older (particularly after 40), it’s likely you will need glasses or lenses again. 

Laser surgery cannot correct squints (an imbalance of eye muscles so the eyes do not appear straight) but can in some cases correct astigmatism (a slight curvature of the cornea which results in the shape being slightly oval - ‘rugby ball’ - rather than round - ‘football’). 

The laser only affects the cornea and will not protect you other eye conditions.  Short-sighted people are particularly at risk of cataracts, glaucoma and retinal detachment and regular eye checks are vital. 

Laser eye surgery is generally not available on the NHS as it’s not considered an essential medical procedure.  However, some Health Trusts have their own private clinics with appropriately qualified surgeons.  A list is available from the Royal College of Ophthalmology, or your GP may well know local surgeons. 

The Royal College of Ophthalmology has produced a Patients Guide to Excimer Laser Refractive Surgery which gives detailed information on all the options.  Professor Clark recommends reading this carefully. 

(It’s a bit difficult to find so here is the link.)

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