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3.5 distinguish between myopia and hyperopia and outline how technologies can be used to correct these conditions
distinguish between myopia and hyperopia and outline how technologies can be used to correct these conditions
- Myopia is short-sightedness. A person with myopia sees objects that are close clearly but objects in the distance are out of focus. Rays from distant objects are focused in front of the retina rather than on the retina. The usual cause of myopia is that the eyeball is too long. Some forms of myopia improve with age.
- Hyperopia is long-sightedness. A person with hyperopia sees objects that are in the distance clearly but close objects are out of focus. Rays from distant objects are focused behind the retina rather than on the retina. The usual cause of hyperopia is that the eyeball is too short or that the lens gradually hardens with age, reducing its power of accommodation.
- Technologies used to correct these conditions include eyeglasses or spectacles, contact lenses or surgery. Myopia can be corrected with concave lenses worn for distance viewing. These lenses cause parallel rays to diverge slightly before they enter the eye so that the lens can focus them on the retina.
- Hyperopia can be corrected with convex lenses worn for viewing close objects. These lenses cause parallel light rays to converge slightly before entering the eye so that the lens can then converge the rays to a point on the retina.
- Refractive surgery may also be used to treat both myopia and hyperopia. A thin flap of the cornea is cut and folded back. A laser is used to reshape the cornea to a more suitable shape. The fold of skin is then folded back into place.A good website that explains refractive errors
Wikipedia.