The Eye and its Working
The eyes are the photoreceptor organs. They are located in the eye orbits formed by skull bones. It is about 2.5 cm in diameter and weighs 6 to 8 grams. It has three layers:1) outer fibrous coat ca...
Defects of Vision
1) Conjunctivitis/Pink eye: It is the inflammation of the conjunctiva.
2) Myopia/Short-sightedness: It is a defect in which a person can see only those objects that are close to his/her eye. It produces blurred vision. It is caused due to elongation of the eyeball or thickened lens.
3) Hypermetropia/Far-sightedness: It is a defect in which a person cannot see nearer objects clearly but can see farther objects.
4) Astigmatism: It is a defect in which light rays do not converge at the retina and the vision becomes blurred. It is caused due to irregular lens or irregular retina.
5) Cataract: It is a disease in which the eye lens becomes opaque.
6) Glaucoma: It is a disease in which intraocular pressure is raised above normal level and loss of vision occurs gradually.
7) Presbyopia: It is a defect in which the lens is not able to focus images of nearer objects due to old age.
8) Colour blindness: It is the inability to recognize one or more colors due to deformity in cone cells.
