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Accelerated Orthokeratology
Accelerated Orthokeratology (A-OK) is a safe, non-surgical process that uses rigid gas permeable (RGP) contact lenses to reshape the cornea. The cornea is a clear dome of tissue on the outer surface of our eye that contributes to the eye's focussing power. Light must be focussed directly on the retina at the back of the eye for us to see clearly, otherwise a "refractive error" such as myopia (near-sightedness), hyperopia (far-sightedness) or astigmatism (irregular shape) exists. Reshaping the cornea will change the focussing power of the eye, and if accurately controlled, can reduce or eliminate refractive errors to dramatically improve a person's natural, unaided vision.
Historically, orthokeratology was first used in the 1960's. The contact lenses were made of an old-fashioned hard contact lens material called PMMA. It took many lens changes over a period of months or years to accomplish because each lens flattened the cornea only a small amount.
The contact lenses used today for the A-OK procedure are a special "reverse geometry" design that are able to reshape the cornea much more quickly than previously. The central portion of the contact lens fits closer to the eye than a standard contact lens - exerting a gentle pressure. It doesn't touch the cornea as there is a tear layer protecting the eye. The pressure of the contact lens on the tear layer shifts the outer layer of the central cornea - the epithelium - more peripherally, thus flattening the cornea and reducing myopia. Astigmatism is also naturally reduced as the cornea becomes more spherical in shape. The contact lenses used are highly oxygen permeable, making them safe for overnight wear while you are sleeping, and therefore more convenient than in the past.
WHAT DOES THE PROCEDURE INVOLVE?
Initially, a complete eye examination is required to assess the prescription and health of the eyes to determine if you are a good candidate for the procedure. A computerized instrument (corneal topographer) is used to perform a non-invasive scan of the eye to accurately determine and map out the shape of the corneal surfaces. Using this information, an initial pair of A-OK lenses are ordered, designed specifically for you. Once we ensure that the lenses fit well, you will wear the lenses overnight and return the following day to the office. The corneal shape and reduction in prescription are assessed. You will continue to wear lenses on a nightly basis over the following week. It may be necessary to make minor modifications in the contact lenses at this stage, depending on the examination results.
Many people will see a rapid improvement in their natural vision after just one night of wear. However, in the first few days, the effect will wear off gradually throughout the course of the day. After about one week, vision should be stable enough for most patients to be without glasses or contact lenses for the entire day.
Once the desired result is obtained, the current lenses are kept as "retainers" that will be worn regularly to maintain the new corneal shape. How often the retainer lenses are required to be worn varies with each individual - most continue nightly or every other night wear. The retainer lens may be required less frequently over time. It is highly recommended to always have an extra pair of retainer lenses. In the event of loss or breakage, your vision will regress to pre-treatment levels while waiting for a new lens to arrive!
WHO IS A CANDIDATE? (Indications)
People of any age who have low to moderate amounts of myopia (up to -4.00 D) or astigmatism (up to -1.00 D).
WHO IS NOT A CANDIDATE? (Contraindications)
Your A-OK specialist is the best individual to determine your candidacy for the procedure, but some general contraindications include anyone who has:
· Inflammation or infection of the cornea or anterior segment of the eye
· Eye disease, injury or abnormality that affects the cornea, conjunctiva or eyelid
· Severe insufficiency of tears (dry eyes)
· Corneal hypoesthesia (reduced corneal sensitivity)
· Systemic disease that may affect the eye or be exacerbated by wearing contact lenses
· Allergic reactions which may be induced or exacerbated by wearing contact lenses or use of contact lens solutions
ADVANTAGES OF A-OK
· Good vision without spectacles or contact lenses for most of the day.
· It is not a surgical procedure.
· It is reversible.
· It is non-invasive.
· It is modifiable - if there is a prescription change with time, the retainer lenses may be modified to correct this!
· It does not hurt.
· There are very few risks.
DISADVANTAGES OF A-OK
· You must be prepared to allow for 4-10 visits over 3-6 months, and continue regular contact lens check-ups at least annually.
· Retainer lens wear is essential or the cornea will revert to its original shape.
· The degree of success is high but cannot always be guaranteed.
· The rate of improvement varies from one person to the next. You must follow instructions implicitly for the best results.
