LASIK expands to laser-assisted in situ keratomileuses. This is an eye surgery done to correct errors in vision such as near-sightedness, far-sightedness, and astigmatism. All these errors are due to the improper focusing of light by the eye. The surgery involves using a laser beam to shape the cornea of the eye. The cornea is the transparent area with refractile properties at the front of the iris. By reshaping the cornea, the light passing into the eye can be focussed appropriately on the retina.
LASIK is an elective procedure, generally performed for cosmetic reasons to avoid wearing glasses or contact lenses. It is often done by personnel wishing to join the military or by competitive athletes for whom their profession requires a certain visual acuity unaided by glasses or contact lenses.
Refractive errors which can be corrected by LASIK
- Myopia or Near-sightedness: In this type of error, light rays are focussed too much in relation to the retina, resulting in the image falling in front of the retina. This makes objects present further away seem blurry. This may occur due to excessive curvature of the cornea or an eyeball that is longer than normal.
- Hyperopia or Far-sightedness: In this type of error the light rays are not focussed enough, and the image falls behind the retina. This causes blurring while viewing objects present close to the eye. Reading becomes difficult. Correction using convex lenses to converge light rays are used. This may occur due to an abnormally flattened cornea or an eyeball that is shorter than normal.
- Astigmatism: This condition arises due to the uneven surface of the cornea making it difficult to view things clearly in different planes. Both near and distant vision is affected. Reading and drawing become especially difficult
Conditions unfavorable for LASIK surgery
- Very severe near-sightedness
- Keratoconus: a disease with severe coning of the cornea
- Thin cornea
- Presbyopia: age-related weakening of vision
- Persistent dry eyes
- Weak immune system
- Ongoing infection in the eye
Preparing for LASIK Surgery
A thorough history and physical examination are done along with a detailed examination of the eye. If contact lenses are regularly worn, these are to be removed prior to evaluation as they can temporarily distort the structure of the cornea.
- Refraction testing of the eyes to confirm the nature of the error
- Tonometry: to measure the pressure within the eyeball
- Fundus examination: This examines the retina
- Corneal topography: which records the thickness of the cornea helping to plan the amount of tissue to be removed during surgery.
Preparing the eye
The eyes are to be kept clean. Special solutions may be prescribed to use in the days leading up to surgery to clean the eyelids and lashes. Avoid eye makeup as this can also increase the risk of infection.
The LASIK procedure
This is a relatively short procedure taking only 30 minutes to an hour which is done on an outpatient basis. You will be made to lie on your back for the procedure. Your eyes will be numbed using local aesthetic drops after which a clamp is used to hold the eye open.
During the procedure, you will feel a sudden pressure on the eye which is from the suction ring, This is used to prevent the eye from moving out of position. An excimer laser is used to cut around the cornea to raise a flap. The flap is pulled back and the necessary corneal tissue is removed using the same excimer laser.
After the appropriate amount of corneal tissue is removed, the flap is replaced. This heals on its own without any sutures.
After the LASIK procedure
In the immediate moments after the surgery, there may be discomfort in the eyes. Vision remains blurry and it may be difficult to see in bright lights. It would take a few hours to feel comfortable. Shades or patches to cover the eyes for a few hours is recommended.
Over the next few days to weeks, vision progressively improves to reach a stable level after a few months.
Risks and complications of LASIK Surgery
Like any procedure, there are potential for certain risks, but these are minimal. The most common post-procedure complication is dry eyes which resolve over time. Individuals may be concerned for vision loss although, this is very rare.
- Dry Eyes: Drying occurs temporarily following any eye surgery. In some individuals, it may take up to 6 months to resolve. In most situations, dry sensation is perceived due to healing. It is recommended to use eye drops during the period preceding and following surgery.
- Double vision, glares, and halos around objects: This is most noticeable around bright lights at night. This discomfort generally resolves within a few days to weeks. However, some residual halos may persist, especially at night.
- Astigmatism: Uneven reshaping of the cornea following surgery can introduce astigmatism even in those without the problem. This may require a second surgery to correct
- Under correction: If inadequate tissue is removed from the cornea, the error is not corrected. This is more common in those with near-sightedness. A second surgery is required, which is generally done a year later.
- Overcorrections: There is a rare possibility that excess tissue may be removed from the cornea leading to overcorrection. This is harder to correct, though a second surgery may help.
- Infection of the cornea: Lack of strict asepsis during and following surgery can introduce infection into the eye leading to infections. Infections immediately following surgery can delay healing.
- Problems with the flap: Inadequate healing of the flap can lead to problems in the vision, with potential for infections and excess tissue growth around the flap.
- Vision loss: Rarely, errors in the surgery can damage the eyes and cause vision loss. Scarring of the cornea from infections or improper healing can also affect vision.
Long term Results after LASIK
In most individuals, there is an improvement in the vision with the resolution of visual acuity to 20/25 or better providing adequate vision without the need for glasses or contact lenses. However, there is variation in results depending on the type of error. Severe near-sightedness and astigmatism do not always have good results.
Occasionally, some people may experience a return of their original vision over time. This may be because of some other underlying condition for the worsening vision which would need to be evaluated and addressed appropriately.