Refractive Surgery

Refractive Surgery

The surgical alternative to glasses or contact lenses?

Today, thanks to modern developments, several effective refractive surgical procedures are performed to reduce or eliminate myopia, hyperopia and astigmatism. Most refractive errors can now be reduced or totally eliminated with the newest techniques and modern specialised equipment.

WHAT REFRACTIVE SURGERY CAN AND CANNOT DO
People who had refractive surgery are usually very satisfied with the results, providing they had realistic expectations before surgery. There are very few people in the world that are born with natural perfect vision, but the amount of refractive imperfections present in many eyes is not enough to require correction to see naturally well. It is realistic to expect a dramatic improvement in natural vision from any of the operations performed. In many cases where the refractive problems are not severe, it may also be realistic to expect normal vision after surgery. But it is not realistic to expect the surgery to provide perfect vision since, it is virtually impossible to produce an eye that is completely free of refractive imperfections. Refractive surgery is very predictable, yet it is not perfect.

a_refsurgery HOW DOES THE EYE FUNCTION?
There are three basic elements that determine the eye’s refractive characteristics.

THE ELEMENTS OF GOOD VISION
The human eye functions like a camera. Light enters from the front of the eye through the cornea. These parallel rays of light are refracted (bent) by the cornea and the lens of the eye so that they form a sharply focused image on the retina at the back of the eye. This image is translated into nerve impulses and sent to the brain by the optic nerve. How clear and sharp an image is formed on the retina determines how well you can see.

WHAT IS MYOPIA?
Myopia is the medical term for nearsightedness. People with myopia cannot focus clearly on objects at a distance. It is probably the most common eye disorder in the world today. Myopia is traditionally corrected by the use of glasses or contact lenses.

Myopia is generally caused by the curvature of the cornea of the eye being too steep relative to the distance to the back of the eye. This condition causes parallel rays of light to focus in front of the retina. The result is a blurry, indistinct view of objects seen at a distance.

In the condition known as astigmatism the curvature of the cornea is not uniform. Instead, the cornea is shaped somewhat like the back of a spoon with one part being more curved than another. This results in no clear focus at any point.

a_myopia

Myopia ( Nearsightedness) affects one in four people in the world. It is generally characterised by an eyeball that is too long in relation to the rest of its parts. Light rays converge before they reach the retina and the brain receives a blurred image. These people can usually see better close up than at a distance.

Hyperopia ( Farsightedness) is characterised by an eyeball that is too short. The light rays do not have enough space to converge on the retina and so reach it without being focused.

Astigmatism is the inability of the eye to focus clearly at any distance because the cornea is not symmetrical. The cornea is more curved in the one meridian than the other. It is shaped like a rugby ball in stead of a soccer ball. Few eyes are perfectly round, but if it is too much the brain cannot receive a clear image. Astigmatism is often associated with hyperopia or myopia.

Presbyopia must not be confused with the above. When you go past the age of 40-50, the lens inside your eye loses its elasticity and cannot accommodate any more. For this you normally need reading glasses.

WHO IS SUITABLE FOR REFRACTIVE SURGERY?
In general, to be a candidate you must:

  • be over 20 years old
  • have stable vision for at least one year
  • have healthy eyes, free from retinal or corneal scars or diseases
  • have a legitimate reason for having the operation
  • be prepared to pay the cost of the surgery as medical insurance do not cover the full expense.

Refractive surgery is not for everyone. If a person is suitable, the impact on one’s lifestyle can be truly dramatic – a new freedom that was not possible before these modern developments. Glasses are versatile and will always have an important role of being a reliable, supplementary aid to vision when other methods of correction are not adequate. But they often limit activities. Distortion, the weight of the frame with lenses and poor peripheral vision can be a problem. So, as good as they are, glasses still leave many searching for a better alternative. Contact lenses are very popular and they work well, but they require meticulous care and cannot correct the full range of refractive problems. Many people have eyes that are too dry or too sensitive to tolerate them. As with glasses there are many occupations and types of sport where the wearing of these are impossible.

BENEFITS OF REFRACTIVE SURGERY
Refractive surgery normally enhances people’s lives by giving them more freedom through natural vision. Some people have difficulty adjusting to glasses or contact lenses. This can be for a variety of reasons such as the shape of their eyeball, nose or face. It can also be because of the lubrication of their eyes, living or working environment, or the type of work or sport they participate in. It takes away the fear that you might be visually handicapped and embarrassed when you lose your glasses or contact lenses.

WHERE IS THE PROCEDURE DONE
Being a microsurgical eye operation, it has to be done in a sterile theatre that is suitable equipped for these types of operations.

WHO DOES THE PROCEDURE

These procedures are done by Ophthalmic surgeons suitably qualified to perform these procedures. Your final visual outcome is going to depend on the special training and experience of the surgeon you choose. The surgeon will decide which one of the various procedures will be most suitable in your specific case and discuss this with you.

TYPES OF REFRACTIVE SURGERY
Usually both eyes are operated on at the same time. This is more comfortable for the patient, and it settles down sooner.

RK (Radial keratotomy) Radial keratotomy was developed by Dr. Fyodorov in Russia in the early 1970’s. The surgery is performed by making radial incisions in the cornea with a micro-adjustable diamond blade. This flattens the central cornea. Different degrees of correction are achieved by varying the depth, length and number of incisions. It is an older procedure and is not done anymore.

AK (Astigmatic keratotomy) This is a variation of the RK procedure and can be done on it’s own if only astigmatism is present or along with radial incisions if myopia is also present This is done by making curved transverse incisions on the cornea. This alters the shape and makes the cornea more symmetrical. This procedure has been replaced with the much more effective Lasik procedure.

PRK (Photo-refractive keratoplasty) The shape of the surface of the cornea is changed with the excimer laser. The laser beam vaporises away microscopic layers of tissue to reshape the cornea and correct focusing problems.

MLK (Microlamellar keratoplasty) Keratomileusis is the oldest form of refractive surgery, but has been much refined and improved upon with new instrumentation. It was started by Dr. Barraquer in Bogota. A microkeratome is used to cut into the central cornea plane. This area is then hinged over and the refractive procedure can be performed in the central cornea with the same instrument. This procedure is not performed anymore, Lasik and PRK has replaced it.

Lasik (“Laser Assisted” In-situ Keratomileusis) Here the refractive reshaping in the “bed” under the flap is done with the excimer laser. The treated area is covered with the original flap. This combined procedure has the ability to correct high and complicated refractive errors. It is virtually painless with good vision within days and an operation mark that is almost invisible even with a microscope. There are not many surgeons in the world with adequate training and experience to perform this procedure with success. With the new generation excimer laser machines, astigmatism and hyperopia can now be corrected as well.

Femtosecond and Intralase are the newest refractive kids on the block. This would be the ideal way to perform any kind of refractive surgery. Because this laser can make intra-stromal cuts the blade is eliminated and you en up with a much better procedure that has no open wounds, less corneal tissue loss and a wider range of treatable refractive errors. The newest lasers are solid state rather than gas dependant and will be even better.

Topography driven lasers are now also coming onto their own. Combining this with Intralase is what we always hoped for, a tailor made personal procedure for every patient.

H-Lasik is the name given to Lasik that is done on hyperopic patients. This is a procedure that can now  be done successfully with the new small flying spot excimer lasers. PRK or Intralase is better suited for this procedure than Lasik.

Lasek is an alternative for people who cannot have Lasik because their corneas are too thin or their eyes are to small or too deep to perform Lasik safely. The epithelium flap is thinner and more shallow than Lasik and heals much faster and better than PRK. Apart from the flap the rest of the procedure is exactly the same as Lasik.

LTK (Lamellar Thermo Keratoplasty) This procedure was performed with the Holmium laser for people that are hyperopic (farsighted). This procedure was replaced with Lasik, since the new generation excimer laser machines give more consistent good results.

Phacic Lens Implants work well for larger refractive errors. For people with higher errors outside these groups there is another procedure where a lens is implanted into the eye between the cornea and the normal lens. The Artisan lens is the best of these lenses on the market today. It is used for the correction of severe hyperopia, myopia or aphacia with or without astigmatism. Where the refractive error is too large to be corrected with other methods. 

Prelex is an option for moderate farsighted people to reduce their dependency on glasses or contact lenses especially when they are over 40 years of age and are having problems with close up reading (presbyopia). There are now better procedures available.

 Accommodative and multifocal lenses. This was a very exciting new procedure where it is hoped that the implanted lens can actually accommodate. It works very well for some people especially those over the age of 50, makes them less dependant on glasses for reading or distance, but, you do lose some contrast and quality pf vision.

Bioptics This is the new alternative for very large refractive errors where it cannot be corrected with one procedure alone and use is made of a combination of procedures to correct the vision.

ACS (anterior ciliary sclerotomy) With this procedure tiny relaxing incisions are made in the sclera. This procedure increases the circumference of the eye and improves the accommodation of people over the age of 50 and so makes them less dependant on reading glasses. It wasn’t a very successful procedure.

Intacs (intra corneal ring segments) This is a surgical treatment for keratoconus and myopia. These intracorneal rings stabilize and strengthens the cornea. In so doing it makes the shape of the cornea more regular and it is easier for keratokonus patients to wear contact lenses or glasses again without the need for a cornea transplant. The recovery period is much shorter than after a cornea transplant. With the advent of the new solid state Intralase machines the Intacs would probably get a new life again, because the groove can be made much more accurately.

SSK (sutureless synthetic keratophakia). This is a procedure to treat hyperopia. A hinged corneal flap is made similar to the one in Lasik, but tissue is added in the form of a tiny lens-disc made of synthetic material. This gives significant improvement in the vision of some hyperopic patients, but, it isn’t a very popular procedure. There are better ways to get to the same outcome.

Artificial Cornea The artificial corneas will hopefully be the answer for those patients that have suffered repeated cornea transplant rejections or those with vascularised corneas, but it is still experimental.

Cross-Linking is a very successful procedure, that has proven itself well over the last couple of years. It strengthens the cornea and therefore works very well for patients with keratoconus. It can also be combined with most of the other surgical refractive procedures.

The Future
There are many other experimental refractive procedures still under investigation. As the technology stands at the moment we are able to correct most refractive errors with great predictability and accuracy. Technology is however always improving. It is almost like deciding to buy a new computer….well knowing that it will at some stage be replaced by a newer technology in future. If your needs are such as to require surgery today and you are a candidate then there is no need to wait for the next generation. If you however have any doubts then wait.

 

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