Surgical methods of correcting vision defects

Surgical methods of correcting vision defects are about direct interference with the eye tissue to reshape it and get a normal optical condition allowing for clear vision without the need to use "prostheses" such as glasses or contact lenses.

RK (radial keratomi) - cut in the cornea
The cornea refracts the incoming light about double as much as the lens of the eye. Even the liquid in the chamber and vitreous body helps to refract the light. If the cornea is irregular bend, you have astigmatism (refraction error). It's the cornea that is treated with an eye laser.

Attempts to reshape the eye surface - more specifically the cornea, which plays the most important role in the optical system of the eye - has been made since 1939. The method was pioneered by Mr. Sato of Japan, who made radiant incisions on the edge of the cornea thus flattening it successfully in the centre.

The true progress in development of surgical methods for correction of vision defects, especially short-sightedness, is associated with the Moscow-based ophthalmologist Prof. S. Fyodorov. Taking from experiences of his predecessors, he refined the surgical technique of radiant cuts around the cornea and developed detailed procedures thus making the method, known as radial keratomy, a safe, effective and widely used method of treating short-sightedness. The procedure flattens the cornea in its centre thus weakening the refractive power of the cornea and helping short-sighted patients (by analogy, the same effect is produced by minus lenses in eyeglasses).

The method has a number of constraints - it can be used for treating short-sightedness ranging from -2 D up to -11 D. The method becomes very complicated in treating vision defects combined with astigmatism and its effects are frequently unsatisfactory. The bigger the defect, the less predictable the treatment effects and the more intra- and post-operations complications (cornea damage, permanent scars). This said, it is quite an aggressive surgical method and its effects depend on the surgeon's technique and precision in making the cuts and selection of an operating plan by the doctor (length, depth and number of incisions).

Laser therapy to correct vision defects
It is the most precise and safest surgical method of correcting vision defects. The computer-assisted laser directly reshapes the cornea flattening it in the centre in the case of short-sightedness or making it more convex in the case of far-sightedness. Since no incisions are required, as opposed to the radial keratomy, there is no risk of damaging the cornea during the procedure by an imprecise cut. The final effect depends on the laser's performance characteristics and precision is assured by a computer, which assist the laser.

Eximer laser
The cornea reshaping by the excimer laser was pioneered by Dr M. McDonald in 1989 in the United States and several millions of such procedures have been performed around the world since then. The excimer laser allows for treating short-sightedness far-sightedness, astigmatism and complex mixed defects. It is also used for treading cornea inflammatory diseases and degenerative disorders not qualified for conservative treatment (drops, ointments). The laser beam clears the affected area with precision.

The Eximer laser treats short-sightedness, far-sightedness, astigmatism and more complex vision defects. It's also used to treat inflammatory diseases in the cornea and genetic diseases that cannot be treated with normal treatment (eye drops, ointments).

The Eximer laser is a pulse gas laser which during the operation of the cornea produces a beam of 193 nm's way length. Its name comes from the terms "excited" and "dimers".

Aescleopion laser is the latest generation of Eximer laser which is designed to operation on the cornea. It's equipped with a system for active co-operation with the patient, algorithms control the amount of removed tissue and can reshape the cornea based on the measurements from the Cornea Mapping.

Advantages with the Eximer laser:

	Precision	The laser is controlled by a computer programme customized for the patient's needs (1 impulse = 1 micrometer change in the shape)
	Sterile environment	Sterile conditions in the laser's operating field
	Security	the procedure is performed on the strictly defined area, the neighbouring tissues are not damaged, microscopic control by the doctor.
	Short time of treatment	Less than 20 minutes
	Performed in out-patient mode	Prior to the procedure the eye is numbed by drops, the patient comes back home after the procedure

Following laser treatments are today available;

	PRK	(Photo Refractive Keratoplasty)
	LASIK	(Laser ASsisted In situ Keratomileusis)
	LASEK/ELSA	(Laser ASsisted Epitheal Keratomileusis))/ ELSA (Excimer Laser Subepithelial)

Stastistic on eye laser treatments

Effects - The research is based on observation of over 500 000 patients
30% of patients - good result (1D)
60% of patients - very good results
10% of patients - Significally reduced vision defect (more than 1.0D)

This means that of 10 patients
6 patients do not need glasses any more
3 patients need glasses only for certain activities (driving, watching television)
1 patient needs much weaker glasses.

NOTE! In keeping with the vision physiology, patients older than 45 years need glasses to read depending to their age.