Eye shapes play a crucial role in vision.
The cornea and crystalline lens focus light in the eye. Light passes through the vitreous humor, a clear gel inside the eye, and strikes the retina at the back. The retina’s rods and cones pick up light and send a clean image to the optic nerve and brain’s visual cortex if everything is working properly. The cornea and lens concentrate light based on the eye’s shape and the distance from the lens to the retina. These shapes produce myopia, hyperopia, and astigmatism.
Myopia or Nearsightedness
Myopia, the most common vision problem across the world, is caused by abnormal eye shape. Generally, myopic eyes are longer than normal—the distance from the cornea to the retina is greater than in a normal eye. This causes light to converge in focus too soon, before hitting the retina, so by the time it hits the retina it is blurry. Nearsighted patients can usually see close objects clearly but have poor distance vision.
Hyperopia or Farsightedness
Hyperopia is the opposite of myopia—the eye is too short. The point where light would converge in focus in the eye is behind the cornea, so the light does not have enough distance to travel. This prevents farsighted patients from clearly focusing on close objects.
While hyperopia and myopia are caused by overall eye shapes, astigmatism is caused by the shape of the cornea itself. Normal corneas are curved equally in all directions, like a section of the outside of a ball. Astigmatic corneas are curved irregularly, like the surface of a football. This prevents light in the eye from focusing at a single point and causes distorted vision.
LASIK and Eye Shapes
LASIK treats these problems not by reshaping the eye, but rather by reshaping the cornea to make up for the shape of the eye. For myopic eyes, the cornea is flattened, causing light to converge at the cornea instead of before it. LASIK for hyperopia does the opposite—the curvature of the cornea is increased to focus light closer. For astigmatism, the curve is simply evened out to provide a clear focus.
The shape of your eyes determines how good your vision is naturally. Fortunately, LASIK can correct irregularly shaped eyes.
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