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Perfect or Emmetropic Eye
Light rays are brought to a single point of focus on the retina.
Objects will be seen clearly without spectacles or contact lenses.
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Myopia or shortsightedness
A myopic eye is longer than a normal eye and light rays are focused to a point in front of the retina. Close objects are seen clearly but distant objects appear blurred.
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Hyperopia or Farsightedness
In this condition the eye is usually shorter than normal and light rays are focused to a point behind the retina. Close objects are blurred and distant objects are clearer.
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Astigmatism
In this condition, the cornea does not have equal curvatures, like a basketball, but has unequal curvatures like a rugby ball. Objects at all distances appear blurred and distorted. Many people have some astigmatism in addition to being myopic or hyperopic.
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Presbyopia
Presbyopia is a normal ageing process and usually occurs around the age of 40. As the eye matures, the normally soft and flexible lens becomes stiff and has difficulty focusing on close objects.
Near vision becomes blurred and difficult. Bifocals and reading glasses, which aid the eye in focusing on close objects are used to correct presbyopia.
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