Laser surgery is one of the latest treatments developed for a number of conditions, such as short or long sight. It works by reshaping the eye to correct visual defects. It can literally cure a problem in minutes, and be carried out as a day patient procedure.

The benefits and features of the new surgical techniques are 

• Immediate improvements  - in the vast majority of cases restoration of vision within days
  
• No pain
  
• No injections
  
• The procedure literally takes only minutes
  
• No overnight stay in hospital
  

Laser eye treatment can be offered to most adults with healthy eyes  who suffer from short-sight. long-sight or astigmatism. 

The outer surface of the eye is its clear, transparent layer called  the cornea. The cornea is responsible for bending the light rays which enter the eye and bringing them to a clear focus. In normal vision this clear image is formed on the retina, the layer of the eye that detects light. 

When you have your eyes tested your optician will give you a written prescription with numbers recorded as follows:

SPH (short for Sphere) indicates the roundness of the cornea. The value of the numbers in the SPH box is recorded in dioptres and indicates how short-sighted or long sighted you are.

CYL (short for Cylinder) indicates the regularity of the corneal shape. The values in the CYL box are recorded in dioptres and indicate the degree of astigmatism. 

AXIS refers to the angle of any astigmatism. The angle in the AXIS degrees from 0 to 180.

In short sight, also known as myopia and nearsightedness, the eyeball is slightly longer than normal and e curvature of the cornea is therefore too steep. This causes the light r: distant objects are blurred and close objects appear sharp and clear.

Short-sightedness is represented on your prescription as a minus sign  : -2.00 or 2.00

Long Sight is also known as Hyperopia or Farsightness is the opposite of short sightedness. It  is caused by a slightly shorter (long-sight) eyeball shape than normal. The cornea brings light to a focus behind the retina causing blurring.           

Long-sightedness is represented on your prescription as a plus sign written in front of, or above the numbers e.g.: +3.00 or 3.00

If the curvature of the cornea varies over its surface then the eye is described as astigmatic. This means the curvature of the cornea is steeper along one axis than another. Again this leads to focusing problems where, for example, the image may be in focus horizontally whilst distorted vertically.

 Astigmatism may be present alone or in addition to myopia or hyperopia.

There are a number of procedures, using laser, microsurgery, conventional surgery and combinations that can treat the conditions discussed above.

The advent of very high powered computers and flexible and controllable laser instruments has made it possible to develop safe procedures that can be provided at a reasonable cost. There are two main types of laser treatment, PRK and LASIK.  

PRK (PhotRefractive Keratectomy ) - this is the older type of treatment  which is has been commonly available in the UK  from around 1991. It is only suitable for mild short sight (-1D to -3D).  

PRK is a technique which uses an excimer laser to reshape the cornea. It can be used to treat mild short-sight only.

With PRK, only one eye is treated per session, the other eye being covered with a patch. 

The whole treatment takes around 15 minutes.  The treatment is carried out as an outpatient procedure, the whole visit to the clinic will be no more that one and a half hours. 

Surgeons often recommend a mild sedative before the procedure to relax the patient. Local anesthetic is given using eye drops (no injections are necessary); there is no pain during the treatment. 

Antibiotic drops or ointment will be placed in the eye and a patch applied. As the effect of the anaesthetic wears off, it is likely that some discomfort or pain are experienced. Rarely,  the pain is quite severe although it does usually persist beyond the first day. The patient is given a supply of pain-relieving tablets, eye drops and instructions. 

The patient attends the clinic for an aftercare visit within the first week, and regular check ups are recommended for around four weeks after the operation. 

The effects of PRK take a number of weeks to develop as the cornea is slow to heal. Vision in the treated eye is initially poor. The healing processes is usually complete within three months, although it may be longer until the full result is achieved.

The average time between the  treatment of the first and second eyes is six to twelve  weeks.

The degree of corneal healing  cannot be completely determined, so PRK is not entirely predictable, some under- or over-correction may occur, but the vast majority of treatments result in a prescription within one dioptre (ID) of the target (the target is usually zero prescription). Even after treatment of small degrees of myopia, it may still be necessary to wear a corrective lens to achieve the sharpest vision, although this is very unlikely.

Overall PRK is very successful for the treatment of milder short-sight and has been widely practised since 1989. Over a million people world-wide have been treated. It has been deemed to be safe and effective by the FDA in North America.

PRK has largely been replaced by LASIK which can treat a greater range of eye defects, and achieves its results instantaneously. However, LASIK is more expensive and requires greater skill on the part of the surgeon.

 LASIK is the most modern form of treatment, which can be used to treat mild to severe  Short sight, long sight and astigmatism. 

	It uses a combination of Microsurgery using a special high precision instrument called a keratome to lift a thin layer of cells to form a flap in the outer layer of the cornea then an Excimer Laser to reshape the cornea.	The Keratome is used to create a flap in the cornea
	The Excimer Laser can very accurately re-shape the cornea. Minute quantities of tissue are precisely removed by the computer-controlled laser, which is programmed to the individual prescription required for each patient. This causes little or no damage to the surrounding tissue, and due to the way the laser operates, there is no danger that the laser can damage the interior of the eye.	The Excimer Laser reshapes the cornea
	Once the cornea has been accurately reshaped, the flap of tissue is replaced.	The flap is replaced

The whole treatment takes around 20 minutes; the laser part of the treatment takes no more than two minutes. The treatment is carried out as an outpatient procedure. The visit to the clinic will be no more that two hours. 

Surgeons often recommend a mild sedative before the procedure to relax the patient. Local anesthetic is given using eye drops (no injections are necessary); there is no pain during the treatment. All that can be felt is some pressure from a special ring that is used to create a slight vacuum to cause the eye to bulge slightly to allow the accurate application of the keratome.  

Antibiotic drops are placed in the eye after treatment. A special protective lens called a ‘bandage contact lens’ is sometimes inserted to protect the eye while it heals.  When the anesthetic wears off, there may be some mild discomfort. The patient is provided with a supply of painkillers and eye drops and is free to leave. The majority of patients will be able to see well enough to satisfy the standard for driving within 24 to 48 hours.  

The surgeon removes the bandage Iens on the first aftercare visit. The patient is provided with a plastic eye guard to be worn at night for the first month. Protective goggles should be worn for contact sports or if there is any risk of debris entering the eye. The patient must not swim or wear eye make up for one month after treatment.   

There can be a feeling of irritation after treatment and a sensitivity to glare for some time, but pain is uncommon. There is a very low risk of infection and this may require eye drops. Irregular astigmatism or detachment of the corneal flap are possible but very unlikely.       

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Last modified: 26-Oct-2005 19:28:59