In a normal eye, light rays will pass through the cornea and lens and come to a sharp focus on the retina. Anomalies in the shape or length of the eye will cause refractive errors which need to be corrected with glasses or contact lenses. There are three main types of refractive errors.
Myopia: commonly known as short-sightedness. A myopic eye is usually longer than normal, causing light rays to focus in front of the retina. This causes close objects to look clearer than distant objects.
Hypermetropia: commonly known as long-sightedness. A hypermetropic eye is usually shorter than normal, causing light rays to focus beyond the retina. This means objects which are further away appear clearer than those close at hand.
Astigmatism: In a normal eye, the cornea (front surface of the eye) is round like a basketball. In astigmatism, the cornea is curved more in one direction compared to the other, and is shaped more like a football. As a result, the image formed inside the eye is not all focused on the same plane.
Refractive surgery attempts to correct these errors of focusing using various techniques.
Photorefractive Keratectomy (PRK)
PRK describes the use of a computer controlled excimer laser to reshape the corneal curvature. In this procedure the surface layer of the cornea, the epithelium, is firstly removed by gentle scraping. The excimer laser is then applied to the exposed surface to change the curvature and hence the optical power of the cornea.
LASIK (Laser assisted in situ keratomileusis)
During a LASIK procedure a flap of cornea is firstly cut using an automated keratome blade. The flap is then folded back and the computer programmed excimer laser reshapes the exposed surface of deep corneal tissue. The flap is then replaced back in its’ original position without suturing.
This procedure involves reshaping the cornea to correct for astigmatism. It involves the placement of small incisions in the corneal periphery parallel to the limbus. The incisions are made perpendicular to the steepest meridian in a n attempt to flatten this meridian as the incisions heal.
This procedure is similar to a cataract extraction in that it involves removing the natural lens within the eye and replacing it with and an artificial intraocular lens (IOL). The power of the IOL is manipulated to provide the desired refractive result post operatively. This procedure is normally reserved for highly myopic patients.
Implantable Contact Lenses
Some patients, especially those with high myopia who are not amenable to refractive laser surgery, may be a candidate for implantable contact lens surgery. During this surgery an artificial lens is implanted inside the eye, without removal of the natural lens, to correct high myopia.
Who is suitable for refractive surgery?
To determine whether you are suitable for refractive surgery we will perform a variety of tests and a thorough eye examination to ensure there are no abnormalities which may influence the outcome of the procedure. Suitable candidates include people who do not want to depend on glasses or contact lenses. Factors that determine whether you are suitable include your occupation, hobbies, lifestyle and the amount of correction required. You should be over 18 years of age and not have had a change in glasses or contact lens prescription in the past twelve months.
Generally those with myopia of 1 to 4 dioptres are best suited to PRK, as this method offers the lowest risk and excellent accuracy and predictability. For those with higher degrees of myopia, astigmatism of hypermetropia the preferred treatment is usually LASIK.
What does the procedure involve?
PRK is performed as an outpatient procedure. You are required to lie flat in a motorised chair. The eye is anaesthetised with drops and a speculum is inserted to keep your eye open. The surface layer of the cornea, the epithelium, is initially removed. The excimer laser will then remove a pre-programmed amount of tissue from the underlying cornea. The actual treatment only lasts approximately 30 seconds and during this time you will need to keep you eye still and fixating a red light.
Following treatment by PRK the eye will be painful for the first 24 to 48 hours due to the removal of the corneal epithelium. Post-operative medications such as analgesics will be prescribed to help relieve the pain and discomfort. Keeping both eyes closed and minimising movement of the eye under the patch will also help ease discomfort.
The vision will not be completely clear for the first few weeks but will continue to improve over 1 to 2 months. It may take several months for the vision to stabilise.
LASIK is also performed as an outpatient procedure and you are required to lie flat. The eye will be anaesthetised with drops and a speculum inserted to keep your eye open. A suction ring is then placed on the eye, this helps prevent the eye from moving and flattens the cornea. The vision will appear dim at this point. The pressure from the suction ring and speculum is similar to a finger pressed firmly on your eyelid.
The automated microkeratome blade is attached to the suction ring. As it moves across the cornea you will hear a buzzing sound while it creates a hinged flap of corneal tissue. This flap is lifted and the laser is centred above your eye. You are required to look at a red fixation light during this part of the operation in which the laser makes a clicking sound. The laser is pre-programmed to sculpt a certain amount of corneal tissue according to your prescription and will last about 30 seconds. When the laser has finished reshaping your cornea the flap is replaced. There will then be a wait of five minutes as the flap adheres back onto its bed.
After the operation a see-through shield will be placed over your eye which will protect it for the first day. It is normal for the eye to feel a little irritated for a few hours. You should go home after the procedure and have a rest. You will be given some sedative tablets to help you sleep. In addition, you are required to use eye drops four times a day to help the healing and alleviate dryness.
Patients treated with LASIK will find that their vision improves dramatically over the first 24 to 48 hours, and vision will stabilise very quickly.
Refractive surgeries all have risks and complications which should be considered. It can sometimes lead to under-correction or over-correction. These problems can often be improved with glasses, contact lenses or additional laser surgery. Most complications can be treated without loss of vision. Permanent loss of vision is very rare, but there is a small chance that your vision may not be as good as before the surgery even with glasses or contact lenses. Temporary side effects include irritation, hazy vision, dryness, glare, haloes, light sensitivity and bruising of the white of the eye.
What is the cost of the surgery?
That depends on which procedure is suitable to you. You will be advised on the cost of surgery after your consultation. As Medicare classify this condition as a “cosmetic problem”, you will not be able to get any Medicare benefit for this surgery. Private health funds vary and although most funds will not contribute to the cost of the surgery, some do. Please check with your individual health fund.
Some of my friends had their surgery done overseas and they say it is cheaper than Australia?
The quality of care here is Australia is very high. We have seen patients who had their surgery performed overseas with good results but we also have seen other patients with complications that needed further surgeries to fix it.
Will I be able to read without glasses after the surgery?
As a general rule, if you are younger than 40 years of age, most likely yes. After the age of forty –whether you had the surgery before at some stage, you will more than likely need to wear glasses for reading. One way to eliminate the need to wear glasses for near work is to plan surgery on one eye to be good for distance and the other eye to be good for near work. This arrangement is referred to as “mono-vision”. This does not suit everyone. If you are considering this option, we strongly recommend you try it first with contact lenses –or glasses- for about 2 months before committing yourself to this surgical option.