Laser refractive
surgery aims to improve the focus of the eyes so there is no longer a dependence
on glasses or contact lenses. In some cases glasses may still be required for
tasks such as night driving or reading. There
are a number of procedures to change the refractive state of the eye. PRK
(photorefractive keratectomy) is laser ablation on the corneal surface after the
epithelial cells have been removed. The patient wears a contact lens for 72 hours
after the procedure until the epithelium has healed. PRK gives excellent results
in correction of myopia up to 4 dioptres. LASIK
(laser insitu keratomilieusis) is laser ablation under a hinged flap of
corneal tissue. Lasik is used to correct myopia and hypermetropia together with
associated astigmatism. ASTIGMATIC
KERATOTOMY - both LASIK and PRK are capable of correcting small and medium
range astigmatism but for large amounts of astigmatism corneal cuts are used alone
or in combination with LASIK
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Normal Eye
Distant objects are seen clearly and accommodation
allows near objects to been seen as well.
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Hypermetropia (long
sight)
The image falls behind the retina although extra
effort may enable distant and near objects to be seen clearly.
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Myopia (short
sight)
The image of distant objects falls in front
of the retina although near objects maybe been clearly.
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Astigmatism
The optical elements of the eye have different
powers at different angles, resulting in a blurred or distorted
image.
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Presbyopia
Reduced accommodating power of the eye prevents
near objects being seen clearly even if distant objects are.
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