Most important Disorders that occur in eye are:
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1. Myopia or Nearsightedness:
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In this case, the eyeball is antero-posteriorly elongated so that the image of distant objects is formed in front of retina. The defect can be removed by using concave glasses.
2. Hypermetropia or Long sightedness:
The person can see distant objects clearly, but not those which are closer. This is due to antero-posterior shortening of the eyeball, so that the image is formed behind the retina. The defect can be overcome by using convex glasses.
3. Presbyopia:
A common defect in old age people due to the loss of elasticity of lens and reduced power of accommodation the disorder can be compensate with reading glasses, bifocal, trifocais or contact tenses.
4. Astigmatism:
The disorder due to rough curvature of cornea or lens which can be corrected by the use of cylindrical glasses during this, instead of the rays of light converging on the retina as points they converge as lines which results in blurry images.
5. Cataract:
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Also called ‘safaid motia’ in Hindi. The sight is impaired due to the lens becoming opaque. The defect can be cured by surgical removal of the defective lens. (Cataract means waterfall in Latin)
6. Trachoma:
It is eye infection caused by Chlamydia trachomatis .It is a form of bilateral keratoconjunctivitis which causes corneal scarring. At its onset, it resembles conjunctivitis with symptoms of tearing, photophobia,
pain, swelling of the eyelids, and superior keratitis; as it passes through four stages, the conjunctival tissues become follicular, heal, and finally scar.
Lacrimal glands and ducts are often affected as well; the upper lid may turn inward and the lashes then abrade the cornea; corneal ulceration results, becomes infected, and ultimately scars. When Scarring is extensive, blindness results
7. Glaucoma:
It is an eye defect in which intra-ocular pressure becomes more, may be due to blockage of the canal of Schlemm [a venous channel at the junction between the iris and the cornea (anterior chamber angle)].