Lasik, PRK Surgery Victoria BC
Myopia
Hyperopia
Astigmatism
Presbyopia
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1(877) 551-2020

Phone:
1(877) 551-2020
 

 

What is a Refractive Error?

"Refraction" refers to the bending of light as it passes from one medium to another. The way your eye refracts light determines your capacity to focus, and depends on several factors:

  • The curvature of the cornea, which determines most of the eye's refractive power
  • The power of the lens, which focuses light directly onto the retina
  • The length of the eye

When one or more of these factors is irregular, the eye cannot focus light onto the retina correctly, the electrical signals sent to the brain are unclear and vision is therefore blurred. Such refractive errors fall into one of four categories: myopia, hyperopia, astigmatism and presbyopia.

At Victoria Corneal Laser Centre, our eye surgeons perform a range of vision correction procedures to correct the following refractive errors for our LASIK Vancouver and Edmonton patients.

 

Myopia (Nearsightedness)

Myopia is the most common refractive problem, affecting one in four North Americans. It is the condition characterized by eyes with too much focusing power, either because the cornea is excessively curved or the eyeball is abnormally long. As a result, light rays entering the eye are focused in front of the retina. Near objects, which require the most focusing power, can be seen clearly, but distant objects appear blurry.

 

Hyperopia (Farsightedness)

Hyperopia is the condition of the eye with too little focusing power. It is caused by insufficient curvature of the cornea, or too little length of the eyeball. Light rays entering the eye come into focus behind the retina, sending a blurred message to the brain. Distant objects, requiring less focusing power, can be seen clearly, but near objects are blurred.

 

Astigmatism

A normal eye is spherical and symmetrical in shape, so that a single focal point is created for the light rays entering the eye. The astigmatic eye is shaped like a football, instead of a basketball. This results in multiple focal points in the eye. Because some parts of the cornea have too much curvature, and other parts are too flat, objects both near and far appear blurred.

 

Presbyopia

Presbyopia is a condition caused by decreasing flexibility of the lens with age. Normally, the lens has the power to "accommodate" to objects viewed closer than 20 feet. That is, it bulges forward in order to increase the focusing power of the eye.  Between 40 and 50 years of age, the lens becomes less flexible and less able to bulge forward, so that it can become difficult to focus on objects that are very close at hand. It is important to understand that even though you may have another refractive problem (myopia, hyperopia, or astigmatism) surgically corrected, you may still experience presbyopia with age, in which case you would still need to use glasses for detailed, close work.