|Cornea and Refractive Surgery|
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What is Refractive Surgery?
Refractive surgery refers to a family of new surgical procedures designed to produce better eye focus with less dependence upon glasses or contact lenses for near-sighted, far-sighted, and astigmatic individuals. This field is one of the most exciting and intensively studied within modern ophthalmology, offering patients the realistic prospect of safe, effective and significant visual improvement.
Historically, ophthalmologists have long performed refractive surgery. Procedures which have an influence on either of the eye's natural focusing elements--the cornea or the internal crystalline lens, will have an impact on how well the eye can focus. Cataract surgery and corneal transplantation are therefore also members of the family of refractive surgical procedures performed routinely by ophthalmologists every day.
There are two types of refractive procedures: incisional and laser. The major incisional procedures are known as radial and astigmatic keratotomy. The most common laser procedures are photo-refractive keratectomy and Laser Assisted In-Situ Kertomielusis (LASIK).
What are radial and astigmatic keratotomy?
Radial Keratotomy is the original and forefather of all incisional refractive surgical procedures. Modern developments in RK technology have made this procedure safer and much more predictable. Ultra thin diamond micrometer cutting instruments with blade depths set under microscopic guidance and several computer generated data bases to guide surgical decisions are now routinely used by refractive surgeons who have embraced Radial Keratotomy and offer it as one of a number of choices that exist for the myopic patient.
What is an Astigmatism?
Astigmatism refers to another focusing problem generated from the two prime lenses of the eye- the cornea (primarily) and the crystalline lens (occasionally). In this condition the eye does not focus to a point because the surface of the cornea (or lens) is not spherical or round in shape. Instead, the surface is ovoid or oval, having one axis of curvature which is steep and another flat. The net effect is a surface that is shaped much like the back of a spoon or a football. In using astigmatic keratotomy, the refractive surgeon aims to alleviate this anomaly in curvature through the placement of short, deep linear or arcuate (curved) incisions. The technique makes use of the same RK technology described above. The steep axis of the cornea is identified and precise incisions are placed to cause a predictable flattening effect and create a more spherical cornea.
These incisions are often placed at the same time that RK surgery is performed for those with combined myopic and astigmatic focusing problems.
What is Photo-refractive Keratectomy and LASIK surgery?
The patient is placed beneath the laser delivery system and a brief training session given in which the individual learns to fixate upon a light during the PRK procedure and the laser is briefly activated to acquaint the patient with the sound and sensation of the treatment. The eye is anesthetized with topical drops which render the procedure completely painless.
Once good alignment and training have been accomplished the operating surgeon will mark and central 7.00 mm zone upon the corneal surface and will manually remove the superficial corneal cells (epithelium) with a blunt polishing instrument. The laser is programmed and delivers the precise number of pulses required to achieve the amount of corneal flattening desired in 30 to 60 seconds . In many instances both eyes are treated consecutively in one sitting. After the photoablation is completed, the surgeon will place a bandage soft contact lens upon the eye and instill topical antibiotic and anti inflammatory drops. The patient leaves the treatment center without a patch.
The newest and perhaps the most exciting procedure in the field of refractive surgery is LASIK. The word LASIK is an acronym for the words Laser Assisted In-Situ Keratomielusis. This is the latest and most effective version of a procedure which was innovated by Dr. Juaquin Barraquer dating back to the 1970s.
In the LASIK procedure the excimer laser has been substituted to removed the refractive lenticle, or layer of corneal tissue required to flatten the cornea. This eliminated the need to use the microtome a second time--adding a new level of precision.
LASIK represents a new concept in laser vision correction . It allows the refractive surgeon to remove corneal tissue without disrupting the surface of the eye. Because of this, on the day following surgery, the eye is comfortable, the cornea clear and the visual result immediately appreciated by the patient. This is a considerable improvement over standard PRK myopia surgery in which patients can often experience discomfort and there can be a significant delay in visual recovery. Additionally, the period of post operative drop treatment can be reduced to 10-14 days in LASIK compared to several months with PRK surgery because the healing pattern is so different.Of note is the fact that there have been virtually no reports of visually significant corneal haze after LASIK surgery.
Patients must consult with an ophthalmologist who can provide the appropriate level of care necessary.
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