Orthokeratology involves the use of contact lenses to re-mould the Cornea; this is done for the sole purpose of reducing or correcting Myopic (short-sightedness) and Astigmatic (irregular-surface) effects in the eye. The practice is comparable to using dental braces by Orthodontists in straightening crooked teeth. The key dissimilarity is that, if the arrangement of teeth is corrected for a long while, the teeth will stick in the corrected new position.
On the other hand, the Cornea is extremely stretchy, and will always return to its normal shape. Because of this, lenses are used every night or once the desired cornea shape has been acquired. The lenses are removed at daybreak giving a faultless visualization, consequently ruling out the need for eyeglasses or contact lenses. This process is hence applied as a substitute to spectacles, refractive surgery, or for individuals who choose not to use contact lenses during daytime hours.
The latter is mostly a result of discomfort from operating in air-conditioned or dusty surroundings, from extensive computer use that reduces blinking rates and tear-film production or from disarticulation and failure in sporting activities. This paper will therefore explain how Orthokeratology works, explain the long-term effects it has on the cornea, show the latest advances in Orthokeratology technology, weigh this process versus laser surgery, and then show prime candidates to Orthokeratology.
“Orthokeratology is the reduction, modification or elimination of refractive error by the programmed application of contact lenses or other non-invasive procedures” (Bloom, 2010). It is also known as Ortho-K, OVC (Overnight Vision Correction), and CRT (Corneal Refractive Therapy). “Marketed under brand names like “Dream-Lens”, “i-GO OVC”, “GOV”, “Wake and See”, “CRT” and “Emerald”, this process involves the use of rigid gas-permeable contact lenses, normally worn only at night, to improve vision through the reshaping of the cornea” (Bloom, 2010).
The design of visualization correction by reshaping the cornea has been practiced for a long time. Medical practitioners realized the re-shaping phenomenon of glass lenses in 1940. The discovery of this process has the contributions done by Jessen, Ziff, Nolan, Paige, Gates, May, Grant, Fontana, Tabb, Freeman, Shed, Kerns, and Binder to the usage of contact lenses for myopia decrease.
George Jessen for example, produced what was most likely the initial Orthokeratology design in 1960. He prepared it from PMMA substances that were marketed as Orthofocus. The designs were commonly unpredictable in their resultant effects. Because of this, there was a belief that practical Orthokeratology was a practice based on luck and not approved science. A lot of groups and persons are alleged to be, the brains behind the initial development of current Orthokeratology solutions. However, Dr. Richard Wlodyga, in particular, is by and large accredited for coming up with the initial reverse-zone-lens designing in 1980.
Before the process of Ortho-K is initiated, a preliminary appraisal appointment consisting of a full Sight-Test and a CCTS (Computerized Corneal Topographical Scan) is done. “This offers the doctor the chance of assessing the general situation and healthiness of the patient’s eyes while discussing the likely effects of the process in the patient’s own case” (Kerns, 2008). Trial contact lenses are then given to the patient for an overnight trial, from which the patient will be assessed the next day. The next day another sight-test and scanning are done where the alteration in the corneal shape and decrease in remedy is evaluated. If at all the fit isn’t approved, then one more overnight trial might be considered necessary.
Once the desired fit is recognized, and the myopia can be reduced where a patient will be able to attain normalized vision, Ortho-K lenses will then be prepared. When the lenses are prepared, the fit is evaluated and then the patient is given the lenses for wearing every night for seven days. Exceptional visualization and comfort are usually maintained when wearing the Ortho-K lenses. “An assessment is done after seven days where if any modification is required, another pair of Ortho-K lenses might be ordered” (Kerns, 2008).
“This series of Ortho-K Contact Lenses, made from High Oxygen Permeable Rigid Material, gently reshape the Cornea towards less curvature and a more spherical shape. This reduces Myopia and Astigmatism whilst dramatically improving unaided eyesight” (Kerns, 2008). Most of the visualized transformations occur fast in the initial few days, and processes for stabilizing these effects follow at slow paces for a number of months. The program’s time span normally differs, it is always between three to six months depending on the level of visual error. “When the maximum results are achieved, the final pair of lenses is worn to stabilize the new corneal shape” (Kerns, 2008).
The ultimate wearing-time depends on a lot of variables, but the healing aim is considered to be high-quality un-aided vision on majority of waking hours, where Ortho-K Lenses are worn the whole night. Most patients are able to put on these Lenses each night. It is alleged that Ortho-K Lenses used in this procedure re-shape the cornea by affecting/moving epithelia-cells covering the cornea surface. Some research on this subject has indicated that these epithelial cells are compacted in some specific positions as well as re-located.
A general misunderstanding in designing these lenses is that, the lenses press the cornea, as a result flattening eyes. “In fact, the belief is that, the forces generated by the reverse curve cause the redistribution of the epithelial cells, and not pressure on the eye. Properly designed lenses do not touch the user’s cornea” (Binder, 2001).
Orthokeratology is beneficial if carried out properly and professionally. Conversely, there are side effects and problems when one chooses inexperienced doctors or contact lenses. “The most serious problems, including vision loss, usually arise from improper lens care, poorly fitted lenses dispensed by unqualified/inexperienced people, or lenses made from dated lens materials that limit oxygen transmission and compromise corneal physiology (causes corneal hypoxia)” (Efron, 2000). Long-term blinding complications are also realized as a result of Orthokeratology.
The latest technology in Orthokeratology involves the usage of computer-controlled accuracy lathes meaning that, designing of lenses is done to sub-micron levels of precision. This offers the prospects of the best quality designs bringing about better results. Because most technological advancement in this method is based on lens designs, a number of high-quality lenses have been made available. These are, “SMART Study (Stabilizing Myopia by Accelerated Reshaping Technique) created by the “Vision Shaping Treatment” (VST) program to collectively market a number of Ortho-k lenses, designs manufactured using Bausch & Lomb base material, and CRT (Corneal Refractive Therapy) lenses” (Peabody, 2005).
Orthokeratology is an excellent alternative if an individual suffers from dried-out eyes. Research shows that, this state is sometimes made worse by surgery. Unlike laser surgery, Orthokeratology is reversible. If one tries re-shaping contact lenses then later on decides to undergo laser surgery as an alternative, he/she can do that. But patients need to terminate the usage of contact lenses, as they wait for some time prior to surgery (probably months), to permit the cornea to completely revert to its normal shape.
Orthokeratology is better than surgical procedures because, high-quality vision is achieved without the use of glasses or contact lenses during daytime, is reversible, can be modified, and does not include an operation therefore it doesn’t hurt.
A lot of physicians consider the prime candidates for Orthokeratology remedy are individuals with no more than – 4 D of myopia and modest to no astigmatism. Non-surgical cornea re-shaping with contact-lenses, can be done on individuals of all ages, so long as, they have healthy eyes. Orthokeratology holds particular appeal for individuals who take part in sporting activities, and those employed in sandy, polluted environments that can bring about setbacks for normal contact lenses.
Since Orthokeratology presents comparable gains to LASIK, it also appeals to young persons and teenagers, who might not be qualified for LASIK. “However, there are some concerns about corneal infections in young people who are fitted with Ortho-k lenses, so it’s wise to discuss this with an eye care practitioner who is experienced in treating this age group” (Binder, May, & Grant, 2001).
Orthokeratology is most suitable for patients, who don’t like wearing spectacles or contact lenses during the daytime each day but do not mind using contact lenses at night, or rarely during the daytime. If the patient’s primary objective is to decrease reliance on spectacles or contacts-lenses during the daytime, then Orthokeratology is the best alternative. On the other hand, if the patient wants to get rid of the trouble of dealing with contact lenses in general, then corneal refractive therapy is not expected to suit this situation.
References
Binder, PS. 2001. An overview of extended wear. Perspective Ophthalmol, 4 (2), pp. 51-67.
Binder, PS., May CH., & Grant, SC. 2001. An Evaluation of Orthokeratology. Ophthalmology, 87 (1), pp. 729-744.
Bloom, Basil. 2010. Orthokeratology. Sidney: University of New South Wales Press.
Efron, N. 2000. Overnight Orthokeratology. Journal of the American Academy of Optometry, 77 (12), pp. 627-628.
Kerns, RL. 2008. Research in Orthokeratology. J Am Optom Assoc, 49 (1), pp. 308-314.
Peabody, R. 2005. Orthokeratology. Epitomes–Ophthalmology, 37 (12), 131-138.