Myopia (near sightedness), Hypermetropia (Long/far sightedness), Astigmatism, Bifocal lenses.?
Myopia (, also called near- or short-sightedness, is a refractive defect of the eye in which collimated light produces image focus in front of the retina when accommodation is relaxed. Those with myopia see nearby objects clearly but distant objects appear blurred. With myopia, the eyeball is too long, or the cornea is too steep, so images are focused in the vitreous inside the eye rather than on the retina at the back of the eye. The opposite defect of myopia is hyperopia or “farsightedness” or “long-sightedness” — this is where the cornea is too flat or the eye is too short. Hyperopia, also known as far-sightedness, long-sightedness or hypermetropia, is a defect of vision caused by an imperfection in the eye (often when the eyeball is too short or when the lens cannot become round enough), causing inability to focus on near objects, and in extreme cases causing a sufferer to be unable to focus on objects at any distance. As an object moves toward the eye, the eye must increase its po
Far-sightedness, or far-sighted and hyperopia. Rays of light relected off objects in front of the eye are focused behind the retina as shown above. Such persons can see well in the distance provided they are young and the refractive error is not large. This error of refraction is corrected by a “+” (convex) lens. The earliest symptoms of uncorrected hypermetropia are “eye-strain”, “watering”, “redness” of the eyes, and often headaches in the later part of the day. Presbyopic persons complain of blurring of text specially after some time. Young children with significant hypermetropia can also develop a convergent squint Short-sightedness or short-sight, because the person affected is able to perform near work without correction, and has difficulty defining distance objects. Rays reflected off an object in front of the eye focus in front of the retina. A “-” or concave lens is needed for correction of this refractive state. Why does it occur? In the great majority of cases the cause of m
