Orthokeratology (Corneal Reshaping) Application of sequentially
flatter PMMA hard contact lenses to flatten the cornea and thereby
reduce the myopic refractive error.
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In the 1990s, there was a resurgence using highly gas-
permeable rigid contact lenses for temporary corneal reshaping. In
this technique, patients with myopia are fitted with reverse
geometry rigid gas permeable contact lenses that are used only
during sleep. The center of the contact lens is deliberately fitted
flatter than central corneal curvature to transiently induce
central corneal flattening, which will reverse myopia during the
day when the lens is not worn. The contact lens must be used every
1 to 2 nights in order to maintain the effect. Food and Drug
Administration approval has been granted for the use of this
technique for temporary reduction of up to 6.0 D of myopia (in eyes
with up to 1.75 D of astigmatism). Several other orthokeratology
contact lenses are available
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The FDA has approved Paragon CRT corneal refractive therapy
lenses for the treatment of up to -6.00 diopters (D) of myopia; VST
overnight ortho-k lenses are approved for up to -5.00 D.
Astigmatism also can be treated: up to -1.75 D with Paragon CRT,
and up to -1.50 D with VST.
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Disadvantage Upon discontinuation of contact lens wear, the
corneas of patients who have undergone orthokeratology tend to
revert to their original shape. Earlier attempts to predict which
patients will respond to orthokeratology based on ocular
biomechanical or biometric parameters have not been successful, and
the effects of orthokeratology were unpredictable and poorly
controlled
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Complications The complications of orthokeratology overlap
those of rigid contact lens wear. Corneal pigmentation rings have
been reported, but these are reversible. Patients may also note a
decreased quality of vision especially under low illumination
conditions due to an increase in higher order aberrations. The most
serious complication that has been associated is microbial
keratitis, first reported in 2001.As with any overnight contact
lens modality, orthokeratology is associated with an increased risk
of microbial keratitis