Orthokeratology

Orthokeratology, also referred to as Night lenses, Ortho-K, OK, Overnight Vision Correction, Corneal Refractive Therapy (CRT), Accelerated Orthokeretology, Cornea Corrective Contacts, Eccentricity Zero Molding, and Gentle Vision Shaping System (GVSS), is the use of gas-permeable contact lenses that temporarily reshape the cornea to reduce refractive errors such as myopia, hyperopia, and astigmatism.

However, Dr. Richard Wlodyga, Dr. Philip B. Hanisch and Nick Stoyan, in particular, are generally credited[3] with developing the first reverse zone lens design in the 1980s.

[3] However, it was not until computerized corneal topography became available during the 1990s that it became possible to apply the theory to create designs with repeatable results through being able to accurately map the surface curvature of the cornea using a non-invasive, painless imaging procedure.

Finally, the introduction of computer-controlled precision lathes meant that lens designs could be manufactured to sub-micrometer levels of accuracy thereby offering the prospect of high volume production becoming commercially viable.

[citation needed] Nightwear ortho-k solutions were available to consumers in many countries outside the US much earlier than within the US, due to international differences between regulatory controls and bodies.

[6] Multiple other research evidence suggest that the reduction in myopic progression is roughly 50%, comparable to that of 0.01% atropine treatment, with remaining uncertainty regarding possible rebound effect after the Ortho-K use is discontinued.

In South Africa, Australia and Taiwan, practitioners using the GOV orthokeratology system have achieved successful fits as high as −10.00D of myopia and +5.00D of hyperopia.

If these issues persist beyond this initial period, the cause may be due to lack of centration of the lens on the eye and/or overly large pupil size (in light or dark).

[citation needed] Orthokeratology showed few severe side-effects, according to a March 2004 report of a very small sample of cases in China where supply of lenses at that time was not subject to any regulatory regime covering safety and efficacy.

[14][15] Complications may also be due to relative corneal hypoxia (lack of oxygen) with prolonged or overnight contact lens wear in lenses made from the wrong material.

[citation needed] Safety advice applicable to most modes of contact lens wear, also applies to ortho-k night-time lenses.

Severe caution should be used before prescribing CRT lenses for children and informed consent should include potential sight-threatening corneal ulcers."

Although sight threatening corneal ulcers are rare, informed consent should routinely be obtained for all new contact lens wearers, whether worn overnight or not.

[citation needed] The Globe and Mail reported two cases in Canada in which Acanthamoeba infections during ortho-k treatment, possibly related to rinsing the lenses in tap water, led to temporary or permanent blindness.