Orthokeratology

 What Is Orthokeratology?

• ·               Temporary  correction of refractive power
• ·               Use of rigid gas permeable lenses.
• ·               Also known as corneal reshaping, Corneal Refractive Therapy (CRT), Vision Shaping Treatment (VST)

 

History

• ·       Early 1960s

§  “Orthofocus”

§  Average reduction 1.00-1.50D with large variability

• ·       Limitations

§  Lack of long term data

§  Keratometry reading only

§  Use PMMA lenses

§  Effects take weeks to months

§  Multiple lens treatment

• ·       Modern Day Ortho- K

§  FDA approval:2002

v Overnight wear and correction of myopia

§  Materials

v Hyper- DK materials for overnight wear

§  Myopia control

§  RGP Design

v Flatter conventional GP vs reverse geometry

§  Use of corneal topography

• ·       Reverse Geometry Design

§  Multi- zone design

v 3 or 4 curve design

v Secondary curve steeper than base curve

• ·       Improved treatment centration
• ·       Improved predictability

 

How does ortho-k work?

The cornea is a clear, dome-shaped window in the front of your eye that focuses light onto the retina and is responsible for most of the eye’s ability to focus. Its tissue is very flexible.

Your Optometrist (orthokeratologist) will map and measure the surface of your cornea using an instrument called a corneal topographer and then design a lens especially for your eye. The cornea map is created by reflecting light off the surface of the eye. The machine doesn’t touch your eye, and there is no pain. The corneal topography map shows your Optometrist (orthokeratologist) the shape and curves of your cornea.

The lenses work by flattening the center of the cornea, changing how light is bent as it enters the eye. Most orthokeratology lenses are worn overnight to flatten the cornea, then removed during the day. These overnight lenses are rigid, gas-permeable lenses that are sturdy enough to reshape the cornea, but also allow oxygen through so your eye stays healthy.

When ortho-k lenses are removed the cornea stays flattened for a while and vision is corrected without the need for glasses. If you stop wearing the lenses at night, your eyes will eventually go back to their original shape and the refractive error will return. You have to keep wearing the lenses regularly to keep the vision correction.

 

 

 

Mechanism

  

Who are the right candidates?

Ortho-k is mainly used to correct near-sightedness (myopia). This vision problem can also usually be corrected by eye glasses, regular contact lenses, LASIK or PRK (Refractive Surgeries). Orthokeratology is a surgery-free way for some people to leave their glasses behind and not have to wear contact lenses all the time.

Ortho-k is sometimes recommended to correct children’s vision. Vision can continue to change for some children into adulthood and their 20’s. Vision correction surgeries like LASIK are not recommended until vision is stable. There is no firm evidence that ortho-k can slow down the progression of myopia in children, but this is also being studied as a possibility.
 ETC

What can you expect from ortho-k?

It can take two weeks or longer to attain the maximum vision correction from orthokeratology, although some people experience significant vision improvement in days. In clinical studies of Food and Drug Administration-approved ortho-k lenses, most patients achieved 20/40 vision or better.

You may need a series of temporary ortho-k lenses to see properly until you reach the desired prescription. Typically, up to three pairs of orthokeratology lenses are used, one after the other, to achieve the best vision correction. Once you’ve reached the desired prescription, you’ll use the same shape of lens each night to maintain the correction.

Until you get used to them, you will probably feel the lenses on your eyes until you fall asleep. With time, they usually become more comfortable. Once your corneas have gotten the final desired curve, you will use a retainer lens as often as your optometrist (orthokeratologist) recommends to maintain your vision.

 

Is orthokeratology safe?

Ortho-k is associated with an increased risk of infection (microbial/bacterial keratitis). This risk is especially concerning for children and adolescents, who may be less able than adults to maintain good hand and contact lens hygiene.

Each year, nearly a million Americans go to the doctor because of eye infections. And the biggest risk factor for infections is contact lens wear. Eye infections can have serious consequences including lifelong vision impairment. For this reason, ortho-k may be more dangerous than glasses, which can be used to correct the same conditions. That’s one of the reasons it is important to consult with an ophthalmologist if you are considering ortho-k.

There is no limit to how long you can use orthokeratology lenses. You must see your ophthalmologist for regular check-ups. But if your eyes stay healthy and comfortable, ortho-k could be used for several years.

 

How much do orthokeratology lenses cost?

In most cases, orthokeratology would be an elective treatment. There are often other, cheaper and better-known methods for correcting refractive errors, like eye glasses. But there may be some cases where insurance would recommend and pay for ortho-k lenses. The cost of ortho-k, including follow-up care associated with fitting the lenses, can vary significantly depending on the type and degree of refractive error. Ortho-k prices generally range from approx

90000 NPR. Ongoing costs for replacement of lenses, lens care solutions and follow-up exams can varies for a year.