Refractive eye surgery is a procedure that is carried out to correct refractive errors in vision (where light rays do not focus properly on the retina due to defects in the eyeball).

The methods of correction are varied and depend on the type and extent of the refractive errors. They range from simple implantation of ring-like material or a semi-hard contact lens to reshape the cornea (a clear, dome-shaped layer that covers the front of the eyes), to more sophisticated methods such as lasers, heat, radio-wave frequency or microsurgery.

This article focuses mainly on LASIK (laser assisted in situ keratomileusis), one of the most widely available methods of refractive eye surgery.

What does refractive eye surgery do?

The purpose of the procedure is to restore or improve the visual acuity (sharpness of vision) of people with short-sightedness (near-sightedness or myopia), long-sightedness (far-sightedness or hyperopia), age-related visual problems (presbyopia), or astigmatism (a refractive error caused by irregular curvature of the cornea, which leads to distorted vision).

The idea behind laser eye surgery is to produce small changes in the surface layers of the cornea, which will in turn produce significant changes in the way the eye focuses light. This should eliminate the need to wear glasses or contact lenses.

To correct short-sightedness the cornea needs to be made flatter. This can be achieved by removing microscopic amounts of tissue from the centre of the cornea. To correct long-sightedness, the centre of the cornea needs to be made steeper by removing tissue from a circular area surrounding, but not including, the centre of the cornea.

To correct astigmatism, the shape of the cornea needs to be altered to a more spherical form. The laser can be programmed to alter the pattern of the beam to remove more tissue in certain areas.

Before refractive eye surgery

Before deciding whether or not you are a suitable candidate for LASIK, an ophthalmologist will normally carry out an initial consultation and a thorough eye examination. The doctor will also ask you about your medical, allergy and medication history.

If you wear contact lenses, it is advisable to stop wearing them and switch to glasses at least two to three weeks prior to your first consultation. Contact lenses change the shape of your cornea and depending on the type of lenses you use, this change may last for a few weeks after you remove them.

This can distort the measurement of your cornea. Check with your ophthalmologist regarding their protocol in this regard.
It is advisable not to wear any make-up or facial cream for a few days before surgery, as these will increase the risk of contracting infection during and after surgery. You may need to arrange transportation for the initial consultation and on the day of surgery, as the doctor may give you some eye drops that will cause blurred vision.

What happens during the surgery?

Laser eye surgery is a day case procedure, and normally takes about 30 minutes. You will be seated on a reclining chair and special eye drops will be given to you to numb your eye. After that the area around your eye will be cleaned and an instrument called a lid speculum will be used to hold your eyelids open.

A small vacuum device will hold your cornea, while the doctor makes a flap in it using a special instrument. The flap is lifted and your doctor will ask you to look at a light source to get your eye into the correct position. Once your doctor is happy with the position, he or she will start the laser. The laser makes a ticking sound and as the heat removes corneal tissue you might experience a smell similar to burning hair.

A computer controls the amount of laser that is delivered to your eye. Before the start of surgery, your doctor programmes the computer to vaporise a particular amount of tissue based on the measurements taken at your initial evaluation. After the pulses of laser energy vaporise the corneal tissue, the flap is put back into position.

Some ophthalmologists encourage patients to have operations on both eyes on the same day, whereas others prefer to do them on separate days.

Aftercare

You will be given eye drops to moisturise your eyes. It generally takes 24 to 48 hours for the flap to re-attach securely to the cornea. During that time, you should not rub your eye at all. Some ophthalmologists provide you with an eye-shield to prevent accidents during the first few nights. Sunglasses might also provide some protection from glare or dust, especially during summer months.

Most patients see great improvement in their vision within the first few days. However, immediately after the procedure, you might experience some blurred vision. After the procedure, have as much rest as possible, do not go swimming and avoid getting water or shampoo in your eyes.
You should contact your doctor immediately and not wait for your scheduled follow-up visit if you experience severe pain, or if your vision or other symptoms get worse instead of better.

What are the risks?

Most patients are very pleased with the outcome of laser eye surgery. However, like any medical procedure, there are risks involved. It is very important to discuss your expectations about the surgery with your doctor, and to try to understand the limitations and possible complications from the procedure.

Complications can vary from itch or dry eye syndromes and glares (especially at night), to infection and even loss of vision in very rare cases.
If you are considering surgery, do not base your decision solely on cost. Consider other factors such as good follow-up, and get some information about the clinic you plan to attend.

You can also discuss the procedure with your general practitioner, who may have some knowledge of the procedure from talking to other patients.

Photorefractive keratectomy

Photorefractive keratectomy (PRK) is a very similar procedure to LASIK, but the ophthalmologist does not create a flap in the cornea, so the postoperative healing time is longer and you will need to see the doctor for a follow-up appointment sooner than you would after LASIK