Refractive Surgeries

History of refractive errors :
People have suffered from refractive errors i.e. myopia, hypermetropia and a stigmatism since early civilization. Refractive errors may be inherited or may develop during growth. Since it proves to be a handicap for daily life, it is important to find a solution, if not a cure, to this problem. Since the fourteenth century, spectacles were the common way to resolve this problem. The advent of the contact lens was the first major advancement in vision correction methodology.

Beyond spectacles and contacts:
Now for the first time patients have at hand a permanent solution for their refractive error problems, may it be short-sightedness or astigmatism.

Laser surgery for correction of refractive errors is a new revolution in Ophthalmic practice.

An introduction to refractive surgeries:
Refractive surgeries are procedures that treat the refractive errors of the eye, like myopia, hypermetropia, and astigmatism.
There are various types of refractive surgeries currently available. Procedures such as LASIK and PRK, are based on reshaping the cornea with the use of an Excimer laser. Another means of vision- correction is the insertion of implantable contact lenses. This lens replaces the natural lens of the eye, and offers patients clearer vision.

Types of refractive surgeries:

Radial Keratotomy (RK)
Excimer Laser
a) Photo Refractive Keratectomy (PRK)
b) LASIK
Implantable Contact Lens Surgery (ICL)

Radial Keratotomy (RK):
A Russian scientist, Prof. Fyodorov invented this technique in 1970.

Methodology:

It involves the use of a diamond knife to make radial cuts on the surface of the cornea 95% deep in order to alter its shape.
The number of cuts on the cornea varies according to the refractive error.
When the error is greater, neutralizing it requires an incremental number of cuts to flatten the central part of the cornea.

However this technique is not very safe and predictable and has the following disadvantages

Glare or intolerance to bright light
Infection
Permanent weakening of the eyeball
Rupture of the globe with minor injuries
Under/over correction
Handicap for people who drive in the night.

EXCIMER LASER :
In the mid-1980s, a few scientific working groups worldwide investigated the potential of Excimer laser and its interaction with the tissue of the eye. Researchers found that IBM's Excimer laser (which was initially used for etching computer chips) also had medical applications.

Today, the technologically advanced Excimer laser has added a tremendous amount of precision, control and safety in etching the cornea and treating near-sightedness, far-sightedness and astigmatism.

Methodology:

The Excimer laser is an ultra-violet laser, and utilizes gases (argon and fluorine) to create a non-thermal, cool beam of laser light.
This light breaks molecular bonds in a process commonly referred to as photo ablation.
To put it simply, directing the laser beam on the cornea is like placing the curvature from your glasses or contact lenses onto the front surface of the eye, thus allowing one to see without the need for corrective lenses.

High precision laser:
The most important aspect of the Excimer laser is that it is remarkably precise:
It is able to remove:

0.25 microns of tissue in a single pulse; that is:

1/200th of a human hair,
1/40th of a human cell,
1/28th of a red blood cell, or
39 millionths of an inch in 12 billionths of a second.

PHOTO REFRACTIVE KERATECTOMY (PRK):
It is a more conventional method of refractive error correction, which involves application of Excimer laser energy on the surface of the cornea. This is an out-patient procedure, which takes around fifteen to twenty minutes for one eye.

Methodology:

In this procedure, the first layer of the cornea (Epithelium) is scraped with the help of a spatula.
Next, laser energy is applied on the bed of the cornea to reshape it.
The eye is patched thereafter for three days.

The healing process differs from person to person according to one’s healing response. It takes three to four weeks for the cornea to become normal.

The disadvantages of this procedure are:

It requires patching of the eye and daily dressing for three to four days.
There is severe post-operative pain, watering and foreign body sensation in the eye for three to five days.
There are high chances of infection due to open epithelial wound.
There is possibility of fluctuation of vision which lasts for few months.
There is possibility of permanent corneal opacity and recurrence of refractive error.
The visual outcome is largely dependent on the healing response of the patient.
There is need for use of steroid drops for up to six months resulting in steroid- induced side-effects on the eye in some individuals.
Frequent follow-up visits are necessary for four to six months.

LASIK – the safest and most effective treatment:
In contrast to PRK, the LASIK procedure is a more advanced and popular means to correct refractive errors.

Methodology:

It is painless as the procedure is carried out under topical anaesthesia (use of drops).
A special instrument called the Microkeratome raises the corneal flap of the eye.
In Lasik surgery, a precise amount of laser energy is delivered under a hinged corneal flap.
This effectively reshapes the cornea and corrects the refractive error.
This flap is placed back after the laser procedure.
The flap is self-healing and does not require any suturing.
In this procedure, the Bowman's layer of the cornea is left intact which makes the technique safer and more predictable.
The entire procedure takes twenty minutes with actual laser time varying between 15-145 seconds.

IMPLANTABLE CONTACT LENS SURGERY (ICL):
Implantable Contact Lens is the latest breakthrough in eye surgery and vision-correction practice.

This revolutionary device is beneficial to persons having:

Myopia between (-) 18 to (-) 30 Diopter and
Hypermetropia between (+) 6 to (+) 15 Dipoter.
It can change the lives of millions of people transforming them from visual cripples to visually- normal people.