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Myopia
The eye defect where a person can see near by objects distinctly but cannot see the objects at a distance.
Hypermetropia
The eye defect where a person can see distant objects Clearly but can't see nearby objects clearly.
Presbyopia
This is an eye defect which happens with aging, in this eye defect a person can't see neither distant objects nor objects that are nearby.
Lens in the eye
Convex or converging
Corrective lens for myopic eye
Concave lens or diverging lens
Corrective lens for hypermetropic eye
Convex lens or converging lens
Cataract
The crystalline lens people at old age becomes milky and cloudy which causes partial or complete loss of vision.
Cataract defect can be cured by
Cataract surgery
Corrective lens for presbyopia is
Bi focal lens
Lens forbi focal lenses
Upper portion is concave lens and lower portion is convex lens
Length of diameter of the eyeball
2.3
The lens system of human eye forms an Image on a light sensitive screen which is a delicate membrane having enormous number of light-sensitive cells called
Retina
Light enters the eye throught a thin membrane called
Cornea
Refraction of light rays entering the eye occurs at
The outer surface of the Cornea
A dark muscular diaphragm that controls the size of pupil is called
Iris
Which part of the eye regulates and controls the amount of light entering the eye
Pupil
Near point for the normal eye
25 cm
Farthest point for normal eye
Infinity
The farthest point upto which the eye can objects Clearly is called
Far point of the eye
The minimum distance at which objects can be seen most distinctly without strain is called
Near point of the eye
When light is very bright
The iris contracts the pupil to allow less light to enter the eye
When the light is dim
The iris expand the pupil to allow more light to enter the eye
The ability of eye lens to adjust its focal length is called
power of accommodation
When the Ciliary muscle are relaxed
The lens becomes thin,the curvatureof eye lens decreases and the focal length increases
When the ciliary muscles contract
The lens becomes thick, the curvature of eye lens increases and the focal length decreases
The cells in retina that respond to brightness or intensity of light
Rod shaped cell
The cells in retina that respond to colour of light that enables us to distinguish between different colors
Cone shaped cells
Reasons for myopic defect
Increase in the length of eye ball/ distance of retina and eye ball Increases
Decrease in the focal length in the eye lens when the eye is fully relaxed
In myopia the image forms
Infront of retina
In hypermetropia the image forms
Behind the retina
Cause for hypermetropic defect
Eye ball is too small
the focal length of the eye lens is too long
The eye lens forms which type of image
Real and inverted
Function of vitreous humour
Maintain the shape of the eye ball
Note 
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