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What Is Refractive Surgery?
Refractive surgery includes several surgical procedures designed to eliminate or reduce the need for glasses or contact lenses. These procedures correct refractive errors by changing the focus of the eye. Common procedures such as LASIK and PRK do this by reshaping the curve of the cornea (the clear front window of the eye) to move the point at which light is focused onto the retina (light-sensitive tissue lining the back of the eye). Procedures such as Conductive Keratoplasty (CK) use radio frequency energy to bend the cornea, and Phakic Intraocular Lenses (IOLs) place an artificial lens inside the eye to more accurately focus light onto the retina.
The History of Refractive Surgery
Ophthalmic surgeons have been performing refractive surgery for the treatment of myopia (nearsightedness), hyperopia (farsightedness), and astigmatism (irregular shaped cornea) for approximately 100 years, but the past decades have produced rapid change and growth by means of refined techniques and the emergence of laser vision surgery.
In 1978 a refractive procedure called Radial Keratotomy (RK) was introduced in the United States. RK involves making of a number of cuts in the cornea to change its shape and correct refractive errors. Following the introduction of RK, doctors routinely corrected nearsightedness, farsightedness, and astigmatism using various applications of incisions on the cornea.
In the 1980s a new type of laser called the excimer laser was developed. Though originally used to etch computer chips, ophthalmologists began using the excimer laser successfully in refractive surgery techniques to remove very precise amounts of tissue from the eye's surface. Excimer lasers revolutionized refractive surgery by providing a degree of safety and precision that was previously unattainable with other techniques.
History of Refractive Errors :
Refractive Errors i.e. Myopia, Hyperopia and Astigmatism is an inherent human trait prevalent since early civilization. This may be inherited or develops during growth and may be considered a variation of normal just like tall or short people are. However, since it proves to be a handicap for daily life, it is important to find a solution if not cure, to resolve this problem. Spectacles have been used since early 14th century followed by more sophisticated contact lenses to help the afflicted population.
Now for the first time patients are being offered 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.
TYPES OF REFRACTIVE SURGERIES
- Radial Keratotomy
- Excimer Laser
a) PRK (Photo Refractive Keratectomy)
b) LASIK
- ICL (Implantable Contact Lens Surgery)
K : RADIAL KERATOTOMY
This technique was invented by a Russian scientist Prof. Fyodorov way back in 1970. It involves the use of 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. More the error, more the number of cuts required to flatten the central part of the cornea to neutralise it.
However this technique is not very safe & predictable and has the following disadvantages.
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- Glare / intolerance to bright light
- Infection
- Permanent weakening of the eyeball
- Rupture of the globe with minor injuries
- Under/over correction
- Inability for good night driving
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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 nearsightedness, farsightedness and astigmatism.
The excimer laser is an ultraviolet 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.
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.
PRK : PHOTO REFRACTIVE KERATECTOMY
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 outpatient procedure, which takes around 15-20 minutes for one eye. This is the procedure in which the first layer of the cornea (Epithelium) is scraped with the help of a spatula followed by the application of laser energy on the bed of the cornea to reshape it. The eye is patched thereafter for 3 days. The healing process differs from person to person according to one’s healing response.It takes 3-4 weeks for the cornea to become normal.
The disadvantages of this procedure are:
- It requires patching of the eye and daily dressing for 3-4 days
- There is severe post-operative pain, watering and foreign body sensation in the eye for 3-5 days.
- 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 glasses number.
- The visual outcome is largely dependent on the healing response of the patient.
- There is need for use of steroid drops for upto 6 months resulting in steroid induced side-effects on the eye in some individuals
- Frequent follow-up visits are necessary for 4-6 months.
LASIK - MOST SAFE & EFFECTIVE TREATMENT
In contrast, the LASIK procedure is more advanced since the laser energy is given under a hinged corneal flap and this flap is placed back after the laser procedure. This 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 corneal flap is raised with the help of a special instrument called the Microkeratome. The entire procedure takes 20 minutes with actual laser time varying between 15-145 secs. The procedure is done under topical anaesthesia (use of drops) and it is painless.
[Top]IMPLANTABLE CONTACT LENS SURGERY
Implantable Contact lens has been the latest breakthrough in Eye Surgery & Eye cares practice.
This revolutionary device is beneficial to persons having myopia between (-) 18 to (-) 30 Diopter & Hyperopia between (+) 6 to (+) 15 D. It can change the lives of millions of people transforming them from visual cripples to visually normal people.
Q 1 What is Implantable Contact Lens?
A 1 ICL is made of highly biocompatible flexible polymer – "Collamer" The polymer material is soft, Elastic and hydrophillic. It has a high refractive index and a thin profile.
Q 2 How does ICL correct high myopia?
A 2 ICL can correct myopia more than – 18 D. The ICL is inserted in the eye through a 3mm incision. It is placed and positioned behind the iris. No sutures are necessary, as the opening is self-healing. However 2 weeks prior to the ICL surgery, two small openings are made in the iris called "iridotomy" With N-d Yag & Argon laser.
Q 3 Is the patient required to stay in the hospital?
A 3 This surgery is carried out as an out – patient surgical procedure and is performed by using topical anesthetic drops. It does not require general anesthesia. The patient does not have to stay in the hospital.
Dr. David (M.D.) eye specialist at Eye Centers of Florida calls this procedure a "walk-away procedure, because once you get the implant in successfully, the patients vision is restored immediately".
Q 4 What is criteria for selection of patient?
A 4 The patient selection is:
- Age must be 20yrs & above
- Indication – myopia – 18D to – 30D
- Indication – hyperopia +6D to + 15D
- For high myopia, a combined LASIK & ICL procedure may be indicated.
Q 5 What is the post – operative care to be taken?
A 5 The patient has to put steroid antibiotic drops for 1-2 weeks after the ICL surgery.
Q 6 What has been the experience of the ICL surgery abroad?
A 6 The ICL has been developed by Staar Surgical AG of Switzerland & has been used for 2years in Europe and Latin America. Food & Drug Administration have also approved clinical trials in USA. Several hundreds of ICL surgeries have been done Internationally.
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