Orthokeratology or Ortho-k lenses are a special type of contact lenses that are used to correct refractive error. Unlike conventional contact lenses, they don’t work when they’re in the eye. Rather, they are put before bed and are taken off during the day. It reshapes the cornea while the patient sleeps and thus reduces the refractive error. The effect is reversible but can be maintained with regular use.
The first model of Orthokeratology lenses was created in 1960 by George Jessen after noticing the phenomenon of spectacle blur. Further research was done by Holden and Mertz in 1980 on contact lens-induced corneal oedema during the day and night. This helped to create contact lenses that are made of materials that are safe for ocular health without causing significant oedema.
The Ortho-K lenses have been approved for daily wear and overnight wear by FDA in the USA in 2002.
Other names of Orthokeratology Lenses
Orthokeratology is also known as Ortho-K, Corneal Refractive Therapy, Accelerated Orthokeratology, Vision Shaping Treatment, Gentle Vision Shaping System, Gentle Molding and Overnight Corneal Reshaping.
How Ortho K Lens works
The refractive errors are caused when the eye is unable to refract and focus the light on the retina. The cornea is responsible for approx. 2/3rd of the refractive power of the eye. So, any change in the corneal curvature massively impacts the refractive error.
Orthokeratology uses specially designed Rigid Gas Permeable (RGP) contact lenses that sit on the cornea overnight. The corneal epithelial cells adjust their growth depending on the form of the lenses, hence effectively reshaping the cornea. Even small changes in corneal curvature can bring noticeable changes.
Every 6μm change in corneal thickness brings about a 1 Diopter change in refractive power
Ortho-K lenses are used to correct myopia, Hypermetropia and astigmatism. It can correct up to -6.00 D Spherical of myopia and -1.25 D Cylindrical power of astigmatism, but the extent of correction varies depending on the case and ocular profile of patients.
In the initial phase of treatment, the patient will observe changes in vision and is asked to wear soft contact lenses during the day for the initial two weeks. After that, the lenses can be worn only at night and removed during the day. The patient will have a clear vision without any corrective lenses.
Who can use Ortho-K lenses
Any patient with mild to moderate myopia and astigmatism can opt for Ortho-K lenses. They’re also actively used to control myopia progression in children. There is no set age limit, children as young as 5 years old can use these lenses if they are compliant. For adults, the best result can be seen up to the age of 40.
They are also used by athletes and TV personalities whose occupation do not allow them to wear spectacles and contact lenses.
Unlike LASIK or LASER Surgery the changes made by these lenses aren’t permanent. The cornea returns to its original shape owing to the elasticity of the cells. But many studies have shown that orthokeratology can effectively slow the myopia progression with regular and compliant usage. Furthermore, it also slows the axial length elongation which is one of the major causes of pathological myopia. Many research studies have proved that Orthokeratology is one of the safest and most effective methods of myopia control which reduces the progression of myopia in children’s youth.
Who cannot use them
Patients with dry eye syndrome, large pupil size, irregular cornea, corneal ectasia and high refractive error aren’t good candidates for orthokeratology. The ortho-k lens is contraindicated in acute or subacute inflammation or infection of the eye, Cases with decreased corneal sensitivity. A complete ocular examination is required to know if you’re eligible for orthokeratology treatment.
What are the advantages of Ortho-K?
- Non-surgical refractive error correction
- Painless procedure
- Cheap as compared to refractive surgery
- It slows down the myopia increment in children.
- Reversible procedure
What are the disadvantages of Ortho-K?
- It’s not a permanent vision correction method
- Frequent follow up is needed, prepare for 4-6 visits over 3-6 months.
- The success rate is higher but not guaranteed in all cases.
Like any contact lenses, Orthokeratology lenses pose a risk of corneal infection and corneal oedema. But with proper hygiene maintenance, regular monitoring and good compliance, this risk is greatly reduced. Cleaning and disinfecting the lenses after each removal is critical.
Orthokeratology side effects
Other minor side effects are occasional watering, irritation, redness, pain and visual distortion, but they are usually temporary and will go away when lenses are removed.
The cost of orthokeratology lenses in Nepal depends upon quality, contact lenses parameter, dk/t values. Contact lenses having high High Dk/t value (Oxygen permeability) are costly than contact lenses having lower Dk/t. There are very limited eye clinics and eye care professionals providing orthokeratology services in Nepal. The official distributor for SEED Japan Breath O Correct Ortho K Lens is Eagle eye ophthalmic enterprises, you can contact them for further details of orthokeratology lenses availability in Nepal. You can directly send message to SEED Nepal | Facebook.
Article By: Manashwi Karki, Optometrist, Nepal