How LASIK works - Goal, procedure, function and outcome

How LASIK works

What is LASIK?
LASIK (laser in situ keratomileusis) is an outpatient surgical procedure used to treat nearsightedness, farsightedness, and astigmatism. With about one million surgeries being performed each year in US alone, it is also the most common laser eye surgery done worldwide.

Why is LASIK done?
A LASIK surgery is generally intended to minimize a person's dependence on spectacles or contact lenses by permanently changing the shape of the cornea (the clear covering of the front of the eye) using an excimer laser. The objective is to modify the focusing ability of the eye, and, hence, enhancing a person's ability to see objects more clearly.

What happens during LASIK?
LASIK is performed in an outpatient surgical setting. With LASIK, the ophthalmologist (Eye M.D.) uses a laser to reshape the cornea, which is located at the front of the eye. This improves the way the eye focuses light rays onto the retina, at the back of the eye, allowing for better vision. First, your eye is made numb with a few drops of topical anesthetic. An eyelid holder, called a speculum, is placed between the eyelids to keep them open and prevent you from blinking. A suction ring placed on your eye lifts and flattens the cornea and prevents your eye from moving. You may feel pressure from the eyelid holder and suction ring, similar to a finger pressed firmly on your eyelid. From the time the suction ring is placed on your eye until it is removed, vision appears dim or goes black. The surgeon then creates a hinged flap of paper-thin corneal tissue using an automated microsurgical device, either a laser or an instrument called a microkeratome blade. The corneal flap is lifted and folded back. The excimer laser, which has been preprogrammed with measurements specifically for your eye, is then centered above your eye. You will look at a special pinpoint of light (called a fixation light or target light) while the laser sculpts the exposed corneal tissue. After the laser has reshaped your cornea, the surgeon replaces the flap in position and smoothes the edges without placing any stitches.

How LASIK works?
If performed correctly, lasik allows many people to perform most of their everyday tasks without wearing corrective lenses. However, those hoping to achieve perfect vision and become completely free of the need to wear eyeglasses or contacts.

In a comprehensive report published by the American Academy of Ophthalmology Web site and which involved findings from 64 LASIK studies done since 2000, the following vision-related findings were shown:

People with low to high myopia: According to the data compiled from 22 studies, as many as of 94 percent of eyes achieved 20/40 or better vision after surgery and did not require correction with glasses or contact lenses.

People with low to moderate myopia: According to the same data compiled from those 22 studies, as many as of 99 percent of eyes achieved 20/40 or better vision after surgery and did not require correction with glasses or contact lenses.

People with high myopia: The same studies showed that about 89 percent of the people with high myopia did not require correction with glasses or contact lenses after LASIK.

What LASIK doesn't do?
Lasik is not about being perfect or having perfect vision. If perfection is your goal, you may be disappointed with your result. After Lasik, your vision may not be always as sharp as it is today with your glasses or contact lenses. Nonetheless, your vision should be excellent and you likely will not need correction. This independence from wearing corrective lenses, rather than perfection, is the main motivation for patients. Also, Lasik does not cure the normal aging process called presbyopia, which usually occurs in the late 40's, at which time you may need reading glasses for fine print. This process has nothing to do with the curvature of the cornea, but rather is due to an increasing inflexibility of the human lens. If you are already in your mid forties or beyond, you will likely need readers relatively soon after the procedure.

All in all, based on the above discussion, the vast majority of LASIK patients has no complications and maintains their visual quality as judged by visual acuity, contrast sensitivity and intraocular straylight after LASIK. With advanced ablation techniques, there seem to be even a potential to have improved visual quality post operatively. Therefore, it can be concluded that various advances in refractive surgical techniques have resulted in a higher proportion of patients achieving functional unaided vision following surgery. Thus, it can be said that the modern LASIK procedure is safe and effective. However, it is essential that practitioners incorporate suitable tests into their assessment in order to obtain a full picture of any visual problems and hence select the correct management strategy.

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