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Risks involved in Laser Eye Surgery


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If you are considering laser eye surgery and would like further information, complete the form on the right hand side and an advisor will contact you.

As with any operation, there is always a risk that something can go wrong, however with today’s technology this is rare. It is important that you understand any possible risks and side effects of laser eye surgery, before you proceed with any laser procedure.

Below is a list of possible risks and information about each one:

Loss of part of your vision

Thankfully the risk of this occurring is very low, however it does sometimes still occur. This can be due to problems during the procedure, such as ineffective corneal shaping or damage to the eye with the laser. It may also occur if you are allergic to the anaesthetic eye drops, however it is more likely that this will just cause some redness and irritation in your eye. People who have had the procedure and now have problems due to loss of vision report that it only affects part, not all of their vision, for example they cannot read a few lines on a newspaper. Unfortunately, this problem is permanent and can’t be corrected by any other type of corrective eye ear such as contact lenses or glasses.

It is estimated that out of every 10,000 people who have laser eye surgery 1 person will have this problem.

Laser surgery can produce higher order aberrations

Higher order aberrations are symptoms that occur quite commonly in people of old age. The most common types are:

  • Halo's - a glowing ring is seen around light sources.
  • Starbursts – rays of light radiate out from a light source, like a star.
  • Ghosting or Double Vision – you can see two of every object.

Studies have shown that having laser eye surgery (most predominantly LASIK) can induce these problems, with approximately 5-10 people per 1000 exhibiting these symptoms.

These higher order aberrations tend to occur mostly at night or in darkened rooms such as cinemas. It is thought these problems are caused either as light hits the boundary between the corrected and non-corrected parts of the cornea, or the place where the flap was cut. This leads to light ‘scattering’ into the eye, producing the image of rays or a halo. During the day when it is bright, the pupil constricts and prevents any of this ‘scattered’ light from entering the eye, however at night when the pupil dilates these problems become more evident. People with larger pupils are thought to be at an increased risk of developing higher order aberrations post correction. This is why procedures such as wavefront LASIK that make thinner cuts are advocated.

These visual defects can be very debilitating and may prevent you from watching the TV at night, going to the cinema and even driving. They usually cannot be corrected.

Your vision may be under or over corrected

The aim of corrective eye surgery is to restore your vision so that you do not need to wear corrective eyewear anymore. In doing so, sometimes the surgeon may not remove enough of your cornea (under correction) or may remove too much (over correction). If under corrected, you will notice that you still can’t see perfectly and may still get the same problems, albeit milder, than before the surgery. However if the opposite occurs and you become over corrected, you will find that you now have the opposite type of vision, e.g. if short sighted before, following laser correction you will be long sighted.

In these circumstances some people may be able to have another round of corrective surgery. This all depends on the thickness of the cornea following the first surgical procedure. It is likely that you may still be required to wear either glasses or contact lenses if the problem cannot be resolved.

You may develop chronic dry, red and itchy eyes

Sometimes laser eye surgery can damage part of the eye, preventing tears from being produced adequately. This causes your eyes to become very dry and irritable, leading to problems with your vision such as blurring and clouding. You may also notice that your eye becomes infected more than it used to, as tears are responsible for killing bacteria.

In some people this problem can decrease over time, however some cases can be permanent, requiring you to use artificial tears for life.

Your sight may not be corrected as well as possible

It is known that patients who have a more severe visual defect, i.e. severe myopia are less likely to have their vision fully corrected. This is due to the size and shape of the cornea being inadequate to undergo the reshaping that is required. In these cases, following the surgery you will still have to wear either glasses or contact lenses.

If you are worried this may happen to you, please consult your local ophthalmologist who will be happy to let you know what you can expect from laser eye surgery.

Your vision correction can decrease with age

If you are long sighted, the results of your laser eye surgery can sometimes decrease with age. This condition, also known as presbyopia, is due to the natural ageing process of your eye and may require you to wear glasses. It may also be corrected using surgery to replace the lens in your eye with a new, synthetic one.

You may get a sub-conjunctival haemorrhage

The conjunctiva is a clear lining over the front of the sclera, the white bit of the eye. When applying the suction cap to immobilise the eye, or cutting the corneal flap some very small blood vessels in the conjunctiva can break. The blood from these vessels then flows into the space between the 2 layers, making part of the front of your eye look red. This is known as Sub-conjunctival Haemorrhage.

This common problem usually resolves after a few weeks and will give you very few symptoms, however if it persists you should consult your ophthalmologist.

Your eye may become infected

Sometimes, either during or after surgery, your eye may become infected and swell. Whilst not to severe a problem if treated well, if left untreated this problem can lead to permanent blindness. Your ophthalmologist will look after your eye following the surgery so this doesn’t happen.

You may get debris in your eye

In some rare cases, little bits of debris can become trapped under the flap in your cornea. This can cause little ‘spots’ to appear in your vision. This can resolve spontaneously, but in some cases may require further surgery.

You may develop astigmatism

Astigmatism is a condition where parts of your vision are in focus, whilst other parts aren’t. laser eye surgery can correct this procedure, however sometimes it can also cause it. When removing corneal tissue, if the wrong amount is removed, i.e. too little or too much, this can give rise to errors in focussing. As the semi-corrected cornea is not uniform how it should be, different areas of the same object may look in and out of focus.

This problem can be corrected buy further surgery, however it depends on the thickness of your cornea after the first procedure. If it is too thin, you may be required to wear contact lenses or glasses.

You may get a slipped corneal flap

This is more common in laser correction procedures that take longer, allowing the flap to dry out. This can be prevented by adequate sleep and rest following the laser procedure.

You may develop corneal ectasia

Corneal ectasia basically means ‘expansion of the cornea’ and occurs if the cornea has become to weak following surgery. This problem is most common after LASIK vision correction, however it is still a rare occurrence. The aim of LASIK is to remove tissue from under a flap in the cornea. If the flap is too thick, or too much tissue is removed the cornea becomes weakened. Normally, the cornea is strong enough to resist the pressure within the eye, however if weakened the pressure in the eye causes the cornea to bulge outwards. This leads to problems with vision, as your eye will no longer be able to focus images correctly.

To correct this problem, some people find rigid contact lenses can help, however it is more than likely you would need a corneal transplant to replace your weakened cornea with a new, strong one.

You may just be unlucky

As with all types of operation, sometimes things go wrong. During the operation the laser may malfunction, the microkeratome may break along with many other things. The occurrences of these types of mechanical error are extremely rare thanks to very stringent safety checks prior to surgery.

Even though these risks seem serious, in the hands of an experienced and competent surgeon it is likely that you will experience brilliant results following your laser eye surgery. Please however bear in mind that things can go wrong. It is important that you understand the risks involved and you alone, not anyone else make the choice to have the surgery as at the end of the day it is your eye being operated on.

Severe complications in laser eye surgery are thankfully very rare, however they do still occur. Some of these problems can be treated to allow your vision to return to normal, sadly however, some may not. It is important that you understand what the surgery and recovery period entails, along with any possible side effects and complications before you agree to have the surgery. Any questions or worries you may have will be addressed by your ophthalmologist.

Even though the risks to your eyesight are very rare when having laser eye surgery, it is still important that you are prepared should they happen to you. Even if you don’t experience any of the more serious problems, it is likely that you may develop some side effects from the surgery itself. The side effects that can occur including when they may start and what can be done to treat them is detailed in the next few sections.


« Long-term Effects of Laser Eye Surgery Side Effects of Laser Eye Surgery »





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