Safety - Laser Eye Surgery Guide

What are the risks of laser eye surgery?

All surgery carries a small amount of risk and laser eye correction is no exception. It is a tried and tested procedure which gives great results and for many people, means no more glasses or contact lenses.

But no procedure is 100% safe. Complications are rare but they do occur and you need to be aware of these before making a decision. These occur in less than 1% of cases although higher numbers than these have been reported.

There are risks which apply to all laser and non-laser procedures; plus there are complications inherent to a particular procedure.

Risks inherent to all procedures include:

  • Under or over correction of a refractive error: every patient is different and this equally applies to their eyes. They all heal at different rates and in different ways.

    This means that some patients can experience an under or over correction of their eye problem. This can mean a second procedure or ‘enhancement’ or the wearing of glasses or contact lenses in certain situations.

  • Imbalance in refractive error between the two eyes: this is also known as ‘anisometropia’. It can occur if just the one eye is operated on. The patient may need to wear glasses or contact lenses to balance the vision between the two eyes.
  • Ptosis: this is the name given to drooping of the upper eyelid. This can happen in the first few weeks after surgery but tends to disappear after that time.

    It can also happen to patients who have undergone eyelid cosmetic surgery or ‘blepharoplasty’.

  • Presbyopia: this is the name given to the condition in which the patient requires reading glasses to see objects close to. This tends to happen when we reach our early or mid forties and is caused by a stiffening of the eye muscles.

    This is not usually a problem for short-sighted people as their problem is with distance vision. If they are wearing glasses then all they have to do is to remove these if they wish to read anything close up. Their ability to view objects close to them is not affected.

  • Reduction in low light or night vision: this shows itself as ‘haloes’, ‘starbursts’ and glare. These effects can be seen around objects in dim light or at night.

    For some patients this can cause problems with driving at night or even daytime activities. The effects can be temporary and last from 4 to 6 weeks.

    Research has found that a few patients can experience these side effects on a long term basis.

  • Eye sensitivity: the eye can feel more sensitive when touched although this tends to be a temporary situation. This is a common enough occurrence in the first few months after surgery. Severe symptoms are rare.

    Less than 1% of patients report long term problems.

  • Contact lens difficulties: the patient may need to wear contact lenses following surgery although this may be difficult due to a change in the shape of the cornea.
  • Retinal Detachment: there can be an increased risk of retinal detachment for short-sighted patients. This risk remains even after laser eye surgery.

Risks inherent with PRK and LASEK:

  • Scarring and haze: all patients will develop a slight corneal haze following surgery. It tends to be at its worse during the first 2 to 3 months and usually disappears after 6 months to a year following treatment.
  • Thinning of the cornea: the cornea becomes thinner by as much as 20% following LASEK and PRK. It is not, however, weakened in any way and so is unlikely to be at risk from any trauma.
  • Reduction in eyesight: in a small minority of cases patients have reported a reduction in their eyesight or ‘visual acuity’. This can mean being unable to read a line or two lower down on the standard eye test chart.

    This can happen in less than 4% of patients with mild to moderate short-sightedness (-0.5 to -6.00 D).

  • Infection: this is a problem common to all types of surgery. With laser vision surgery there is a tiny risk of infection as the surface of the cornea has been removed. This is rare and happens in less than 0.1% of cases.

Risks inherent with LASIK (or LASIX):

  • Haze: lasik involves cutting the cornea which means less recovery time and a reduced risk of hazing following surgery.
  • Corneal instability: if too much tissue is removed (cutting) during this procedure than this can cause a weakening of the cornea itself. This can lead to a condition called ‘Ectasia’ in which the centre of the cornea appears to ‘bulge’ outwards leading to poor quality sight.

    LASIK is a more complex procedure than LASEK or PRK and can a thinning of the cornea as well as instability.

  • Reduction in vision: also known as ‘BCVA’ (Best Corrected Visual Acuity’). This can shows itself as an inability to read one or two lines on a standard eye chart.
  • Dry eye: this happens in the majority of cases and is caused by the cutting of surface nerves in the eye. These nerves take around 6 months to regrow.

    Eyedrops can be used to ease dry eyes during this time.

  • Corneal flap problems: LASIK involves the cutting of the outer layer of the cornea or epithelium before lasering the cornea itself. A special ‘corneal flap’ is created during this procedure which lifted and folded back whilst the cornea is reshaped and then placed back in position once this is completed.

As a result of this there are a small amount of risks involved with this flap such as:

  • Wrinkling
  • Extensive damage of loss of this flap
  • The flap has broken free (requires stitches to fix it in place)
  • Epithelia growth under the flap
  • Insufficient cut of the flap (requires a repeat procedure)
  • Retinal bleeding
  • Penetration of the eye by the microkeratome (special device used for this procedure).
  • Possible loss of the eye due to bleeding or infection (very rare).

What are the success rates?

Success rates are excellent in people with mild refractive errors. Around 99.5% of patients achieve unaided driving standard levels of vision following this surgery. This means that they are able to drive without the use of glasses or contact lenses.

Success rates are equally good in patients with moderate refractive errors and come in at 95%.

Even those patients with severe refractive errors report around 90% success rates.

Note: these are ‘driving standard’ levels. Driving standard is defined as being able to read the 5th line down on the eye test chart.

The remainder of patients may need to wear glasses or contact lenses for optimal vision.

Success rates tend to be higher for short-sighted patients.

Patients aged over 40 will require reading glasses after this surgery – if they have had both eyes operated on.

What if something goes wrong?

This a major concern for people as our eyes are very precious and the last thing anyone wants is problems with their vision.

There are risks with laser eye surgery but these are very small. In some cases further treatment or ‘retreatment’ is required.

Aftercare is a vital part of your treatment process and so it is important that you attend your aftercare check ups.

Complications are rare but if you do notice any problems with your sight following surgery then contact your ophthalmic surgeon.

Will I get perfect eyesight?

You will get what is called ‘20/20’ or normal vision. That is the 2nd line from the bottom on a standard eye test chart. The majority of patients can expect to achieve this good level of vision.

This applies to patients with a mild refractive error.

This can mean no more glasses or contact lenses unless you had a moderate to severe refractive error. In these cases you will still have to use either of these.

Even better, it means that you are able to drive without having to wear glasses or contact lenses. Driving standard vision is defined as being able to read the 5th line down on a standard eye test chart.

Perfect vision (known as ‘20/20’ vision in the US) is a comparison between what you and normal sighted people can see at this distance. It is measured at 6 metres in the UK (‘6/6’).

As with any procedure you need to have realistic expectations about what this surgery can achieve.