Before you make a decision about LASIK eye surgery you should know how the eye functions. We will decide if you are an ideal candidate by assessing the health of your eye. Before laser vision correction can be done our surgeon will perform a detailed pre-operative examination.
How the Eye Functions
Your eye is like a camera. Your eye has:
- A variable opening called the pupil
- A lens system, which includes the transparent covering called the cornea and a spherical lens (LASIK eye surgery procedure is performed on the cornea)
- A reusable "film" called the retina
- Various sets of muscles (the muscles control the size of the opening, the shape of the lens system and the movements of the eye)
On the back of your eye is a complex layer of cells known as the retina. The retina reacts to light and conveys that information to the brain. The brain, in turn, translates all that activity into an image. Because the eye is a sphere, the surface of the retina is curved.
In the retina, sensory cells called rods and cones change the photons of light into electrical signals, which are then transmitted to and interpreted by the brain. The ability to focus the light on the retina depends on the shapes of the cornea and the lens, which are controlled by their inherent shapes, their stretchiness or elasticity, the shape of the eyeball and sets of attached muscles. So, when you look at something, muscles attached to the lens must contract and relax to change the shape of the lens system and keep the object focused on the retina, even when your eyes move; this is a complex set of muscle movements that is controlled automatically by your nervous system.
When you look at something, three things must happen:
- The image must be reduced in size to fit onto the retina.
- The scattered light must come together -- that is, it must focus -- at the surface of the retina.
- The image must be curved to match the curve of the retina.
The light passes through the cornea and pupil. It is bent (refracted) by the lens, and then comes to a point (focus) on the retina; this is where the image is formed. Light enters the eye and an image is focused on the retina. To do this, the eye has a lens between the retina and the pupil (the "peep hole" in the center of your eye that allows light into the back of the eye) and a transparent covering, or cornea (the front window), thus the lens and the cornea work together to focus the image onto the retina.
Most vision problems occur when the eye cannot focus the image onto the retina. The most common problems are known as Myopia (nearsightedness), Astigmatism, Hyperopia,(farsightedness) and Presbyopia. In most cases vision correction is achieved with LASIK eye surgery.
Before LASIK eye surgery can be performed, you must have a thorough Pre-Operative Eye Exam to ensure that you are an ideal candidate for the procedure. An ideal LASIK eye surgery candidate meets the following criteria:
- Vision correction - Your existing vision must fall within an acceptable correction range and must not have changed significantly within the last twelve months. You must have a vision correction problem. The differences in vision are measured in diopters, which are degrees of prescription on a range that scales from -12.00 diopters, for severe myopia, to +5.00 diopters for severe hyperopia.
- Here are the diopter ranges for vision correction procedure
- Myopia (up to -12.00 Diopters) (Spherical equivalent)
- Hyperopia (Up to +5.00 Diopters) (Spherical equivalent)
- Astigmatism (Most cases up to -9.00 Diopters)
- Cornea thickness - The cornea must have a total thickness of 500 microns or greater, depending on ablation depth (how deep and how round the reshaping needs to be) and diopter range treated. The "new" Bausch & Lomb Zyoptix XP microkeratome creates a flap that is 150 microns thick and each diopter treated results in the removal of approximately 10 microns. To be considered a healthy laser vision correction treatment, the laser must leave about 250 to 300 microns of posterior (behind the flap) thickness after the procedure.
- Pupil diameter - The diameter of the pupil ideally should be no more than 6.5 mm. However, advances in the laser vision correction can now work with diameters up to 9.5 mm.
- Age - You must be at least 18 years of age to have laser vision correction.
- Health - You must be in good overall health and have good eye health. There are certain diseases that may interfere with laser vision correction surgery they include auto-immune diseases such as rheumatoid arthritis, lupus), vascular disease, eye diseases (severe glaucoma, cataracts, ocular herpes simplex) and severe diabetes.
- Eye diseases - You must not suffer from glaucoma, cataracts, amblyopia, strabismus, kerataconus or other eye related illnesses.
- Pregnant – You cannot have vision correction surgery if you are pregnant or attempting to become pregnant
- Nursing - Nursing mothers should wait six months after before considering laser eye surgery.
- Certain drugs - Acutane (acne), immune-system medications could interfere with laser vision correction surgery.
The only definitive way to determine if you are an ideal candidate for LASIK eye surgery is to have a full Pre-Operative Eye Exam.
This website is designed to inform you about LASIK eye surgery and the services offered by LASIK Eye Centers. Find out if you’re a LASIK eye surgery candidate now.
Contact us at 604-682-4900 or 1-866-682-4900.
LASIK EYE CENTERS
2788-1177 West Hastings Street
Vancouver, BC Canada
V6E 2K3