Laser Eye Surgery Procedures

LASIK and PRK
VISX Advanced CustomVue Procedure
Refractive Lens Exchange
Monovision

Lasik & PRK The basis for all laser vision correction is to reshape the cornea so that it changes the focal point of the eye. Usually, the focal point is changed so that an image focuses perfectly on the retina. For a nearsighted (myopic) person the cornea is reshaped to a flatter curvature to improve vision. For a farsighted (hyperopic) person a ring shaped treatment is done to increase the central curvature, thus changing vision. To treat astigmatism, more treatment is needed across one axis of the cornea than the other. There are two main types of laser vision correction: LASIK and PRK. Both use the same laser, and both have essentially the same end visual result. The reshaping of the cornea must be performed on the second layer, the thickest layer, called the stroma. Laser treatment cannot be done on the outermost layer (epithelium) as this layer is constantly regenerating. It fills back in over time, so changes to this layer would not remain constant. We can get to the second layer in 2 ways:

LASIK (Laser Assisted In-situ Keratomileusis): A thin flap is created that consists of the first layer (epithelium) and a small amount of the second layer (stroma). The flap is gently folded back by the surgeon to expose the majority of the stromal layer, which is then reshaped with the laser to change a person’s prescription. During laser treatment, which usually takes 10 to 60 seconds, any fine eye movements are tracked with a sophisticated tracking system, and there is no sensation of pain or discomfort. The flap is then laid back into place. Because most of the surface layer of cornea is replaced in its original position, very little surface area needs to "fill in" and recovery is rapid. Most people see well the day after surgery.

The cornea is reshaped under a protective flap Nearsightedness Farsightedness Astigmatism

PRK (Photorefractive Keratectomy or Advanced Surface Ablation): The second layer of the cornea (stroma) is exposed for laser treatment by removing the first layer (epithelium) over the area to be treated. Laser pulses are then applied to the surface of the stromal layer to reshape the cornea. Sophisticated alignment and tracking systems guide the laser during treatment, which usually take between 10 and 60 seconds. A thin soft bandage contact lens covers the cornea for approximately four days as the epithelium regenerates. After the contact lens is removed, patients notice a day by day improvement in vision, usually reaching driving levels of vision within a few more days. Although PRK patients need more time to heal, the end result is identical to the LASIK procedure. PRK provides less risk due to its simplicity and the fact that it does not require a flap to be made.

The excimer laser removes tissue less than the thickness of a human hair The reshaped cornea causes images to focus more directly on the retina

RLE (Refractive Lens Exchange): Although not technically a laser surgery, refractive lens exchange surgery (RLE) is also done at Kelowna Laser Vision to reduce dependency on glasses or contact lenses. Unlike laser surgery, in which the cornea at the front of the eye is reshaped to change vision, RLE changes vision by replacing the natural lens inside the eye. The implant lens has a power that incorporates the prescription previously worn as glasses. RLE may sometimes be followed by PRK to give the best possible clarity of vision. This may be the best option for people with early cataracts, high prescriptions, or corneas that are not thick enough for laser surgery alone.

Monovision: All people experience a loss of near focusing power as they age. This is known as presbyopia. The natural lens inside the eye was once flexible, which allowed it to change shape easily to focus for reading. With age, the lens gradually loses flexibility resulting in a decreased ability to focus at close range. Although there is no way to stop this process from happening, there are methods to improve near vision, including reading glasses, bifocals, progressive lenses, and monovision.

Monovision can be done with LASIK, PRK, or RLE. It involves adjusting the amount of laser treatment done on a person’s non-dominant eye. This eye is treated to have a closer focal distance, better for reading, but not as good for distance vision. The other, dominant eye is treated normally to be as clear as possible for distance vision. When both eyes are used together, people can see both distance and near.

Candidates for Monovision are usually over 40 years of age, as this is when presbyopia starts to become noticeable. They have 20/20 corrected vision in each eye, and have realistic expectations about what monovision will be like. You will find out if you are a candidate at your laser surgery consultation.

There is an adjustment period for monovision, which is usually from days to months. Most people adapt quite naturally, but are aware of the difference between the two eyes at first. When the brain adapts, this sensation goes away. Early on, people may have some symptoms such as tired feeling eyes, fatigue, and halos around lights at night. Patients should relax and use both eyes simultaneously to give their brain a chance to adapt.

It is important to understand that monovision is a way to decrease dependence on glasses, but it may not eliminate them altogether. Monovision allows people to see at near for most tasks, but extra magnification may still improve vision for very fine print or for prolonged reading periods. This may become more noticeable as the natural lens of the eye continues to lose focusing power, however, near vision will always be better with monovision than without. Most patients see well for distance vision without glasses, but if needed, vision can be improved for demanding distance vision tasks (eg. night driving) with use of occasional distance glasses.