Please helppp ...need fast
Dear Student,
a) Astigmatism is an eye condition with blurred vision as its main symptom. The front surface of the eye (cornea) of a person with astigmatism is not curved properly - the curve is irregular - usually one half is flatter than the other - sometimes one area is steeper than it should be.
Cause
When light rays enter the eye they do not focus correctly on the retina, resulting in a blurred image. Astigmatism may also be caused by an irregularly shaped lens, which is located behind the cornea.
Presbyopia is a common defect of vision, which generally occurs at old age. Presbyopia is the defect of eye in which a person cannot see further as well as nearer objects clearly. A presbyopic eye has its near point greater than 25 cm and it gradually increases as the eye becomes older.
Cause
1. weakening of the ciliary muscles
2. reduction in the flexibility of the eye lens
Correction
A person with presbyopia cannot read letters without spectacles. It may also happen that a person suffers from both myopia and hypermetropia. This type of defect can be corrected by using bi-focal lenses. A bifocal lens consists of both convex lens (to correct hypermetropia) and concave lens (to correct myopia).
Regards
a) Astigmatism is an eye condition with blurred vision as its main symptom. The front surface of the eye (cornea) of a person with astigmatism is not curved properly - the curve is irregular - usually one half is flatter than the other - sometimes one area is steeper than it should be.
Cause
When light rays enter the eye they do not focus correctly on the retina, resulting in a blurred image. Astigmatism may also be caused by an irregularly shaped lens, which is located behind the cornea.
Correction
Astigmatism can be corrected with glasses, contact lenses, refractive laser surgery and Implantable contact lenses.
Astigmatism can be corrected by soft contact lenses as well as hard contact lenses. Contact lenses for astigmatism are known as toric lenses.
Presbyopia is a common defect of vision, which generally occurs at old age. Presbyopia is the defect of eye in which a person cannot see further as well as nearer objects clearly. A presbyopic eye has its near point greater than 25 cm and it gradually increases as the eye becomes older.
Cause
1. weakening of the ciliary muscles
2. reduction in the flexibility of the eye lens
Correction
A person with presbyopia cannot read letters without spectacles. It may also happen that a person suffers from both myopia and hypermetropia. This type of defect can be corrected by using bi-focal lenses. A bifocal lens consists of both convex lens (to correct hypermetropia) and concave lens (to correct myopia).
Regards