Most patients who are able to successfully wear glasses and contacts and are able to see with corrective lenses will be a candidate for LASIK. However, there are several conditions that can prohibit you from having LASIK surgery and risks that may cause you to have a poor result.
First, begin with what type of vision can be corrected with LASIK surgery. A person who needs glasses or contacts has a “refractive error”. There are four types of refractive error myopia, hyperopia, astigmatism and presbyopia. A person who has perfect eyesight and lacks a refractive error is called “emmetropic”.
In an eye without a refractive error, light rays enter through the cornea and focus directly on the retina at the back of the eye.
In the myopic eye, the cornea is often steep and light rays focus in front of the retina, causing distant objects to appear blurred.
In the hyperopic eye, the cornea is not steep enough and light rays focus behind the retina.
With astigmatism, the cornea has an irregular shape, which scatters light rays and causes both close-up and distant objects to appear blurred.
Presbyopia is a condition where a person progressively loses their lens elasticity and ability to accommodate (focus up close). This condition affects the ability to read at close ranges. The necessary corrective lenses are called reading glasses. Even people who have had perfect vision all of their lives will develop presbyopia in their mid-forties. The excimer laser has no effect on your focusing muscles. The excimer laser cannot help patients who are experiencing the effects of presbyopia, however, there are new techniques being developed for this condition. Ask your doctor if you are a candidate for these new procedures.
Some of the contraindications, or conditions, for which the surgery should be avoided:
Keratoconus – genetically cone-shaped cornea.
Pregnancy or lactation
Progressive myopia – vision should be stable at least one year prior to having lasik surgery.
Keloid formers or people with autoimmune or immunodeficient diseases.
Presence of cataracts.
You must be 18 years or older to have lasik surgery, under present FDA guidelines.
There are other conditions, which may affect the results of your surgery. Should you suspect you have any of these conditions, consult your doctor.
Corneal scars from previous injuries or surgeries (i.e. radial keratotomy)
Diabetes can cause abnormal healing; however, many diabetics have had laser vision surgery with results comparable to those of non-diabetics.
Use of medications. There are medicines that can cause corneal scarring, infiltrates, and some interfere with healing. Consult your doctor, he/she can tell you if you should discontinue medications prior to your procedure and resume shortly after surgery.
Large pupils 8mm or greater, this can cause significant night glare.
Before undergoing an eye examination for refractive surgery, you must be out of your contact lenses. Contact lenses alter the shape of your cornea and can affect the measurements necessary for having LASIK surgery. Patients wearing soft contact lenses should be out of their lenses for three to seven days. Soft-toric, Gas-permeable, and hard contact lens wearers, in contrast, take at least two to three weeks to stabilize the cornea. Talk to your doctor about your specific lenses and cornea shape.
With LASIK, is it important to have an adequate amount of tissue for removal for full correction. Excessive tissue removal can result in severe corneal instability in patients with thin corneas or those with normal thickness corneas with disproportionately high prescriptions. It may be best to under-treat and be left with some residual myopia rather than be fully treated with a small optical zone. It is important to understand the limitations of these procedures based upon your own prescription and eye characteristics.
Laser correction of certain visual problems is the most technologically advanced method available today for reducing your dependence on glasses and contact lenses. The outpatient procedure can correct nearsightedness, farsightedness, and astigmatism by gently reshaping the cornea of your eye with a cool, ultraviolet beam of laser light.
It is estimated that over one million laser procedures have been performed in 52 countries around the world. In fact, vision correction by laser is expected to become the most common procedure performed worldwide within the next five years.
Vision correction using the excimer laser can also dramatically improve your quality of life. From the simple pleasure of being able to see the alarm clock in the morning, to playing sports, and pursuing career-related opportunities, many patients are able to enjoy life with improved self-confidence and renewed enthusiasm.
A refractive procedure attempts to re-shape the cornea to allow light rays to focus directly on the retina. Myopia, hyperopia, and astigmatism all relate to the shape of the surface of the cornea and are therefore correctable with Laser Vision Correction – LASIK.
The reasons a person may not be a candidate to have LASIK vary greatly; however, most doctors offer a complimentary consultation to determine your candidacy for LASIK. Your doctor is the best person to determine if you are a good candidate Laser Vision Correction – LASIK.