Orthokeratology or Ortho-K is a non-surgical method for correcting refractive errors in vision like nearsightedness or myopia, astigmatism, and even farsightedness or hyperopia to a lesser extent. It involves wearing specially designed contact lenses to reshape the cornea temporarily. These lenses are rigid and gas-permeable. They are worn during sleep and removed during waking hours. The fact that Ortho-K is a non-surgical or non-invasive refractive correction method makes it an ideal alternative to invasive procedures.
Understanding Orthokeratology: A Definitive Guide to the Advantages and Disadvantages of Ortho-K
Notable Advantages: Specific Applications and Benefits
Refractive errors cause blurred vision and occur when the eye does not bend light correctly. The most common method to solve these vision problems is to wear prescription glasses and contact lenses. Other methods involve invasive procedures like implanting lenses or reshaping the cornea through laser surgeries like Lasik. The cornea provides primary refraction or focusing power, and reshaping it is considered a more long-lasting method.
Studies in tissue growth and propagation indicate that foreign materials influence the growth and orientation of epithelial cells and tissues. These are found in the outer layer of the cornea. This is the general principle behind orthokeratology. The proximity of Ortho-K lenses to the cells creates a proximal pressure that then changes the shape of the cornea. This makes orthokeratology a more appealing alternative to invasive and higher-risk procedures.
Below are the advantages of Ortho-K:
• Non-Surgical and Temporary Effect: One of the main advantages of Ortho-K is that it is a non-surgical method for refractive error correction. This means that it is less risky than invasive procedures like Lasik and lens implants. The effects are also temporary. This can also be an advantage for patients who factor in reversibility.
• Freedom From Wearing Glasses or Contacts: Individuals have clear vision throughout their waking hours after wearing the lenses during their sleeping hours without needing to wear their prescription glasses or contacts. This is suitable for individuals who have active lifestyles. Examples include athletes and outdoor workers.
• Alternative to Laser Eye Surgery: This method is considered an alternative option to those who either do not want to undergo laser eye surgery or are not qualified to get one. These include people who are too young, those who have thin corneas or large pupils, or have known predispositions like certain autoimmune conditions.
• Slows Myopia Progression in Children: Clinical studies show that orthokeratology can moderate the progression of nearsightedness in children and teenagers. These groups are not suitable for invasive procedures because of their age. Ortho-K has essentially been positioned as an alternative to prescription or corrective glasses.
• No Waketime Dry-Eye Problems: Another key advantage of Ortho-K, particularly when compared to prescription contact lenses, is that patients are free from dry-eye issues during their waking hours. Contacts can cause dryness. Persistent dry eyes can lead to irritation and make wearing contact lenses more uncomfortable.
Data from 101 orthokeratology studies and 88 control subjects, which were collected and analyzed in a study by J. Santodomingo-Rubido, S. W. Cheung, and C. Villa-Collar, revealed that wearing Ortho-K lenses provided a clinically and statistically significant reduction in the axial elongation of the eyes of children with myopia or nearsightedness over two years. The rate of slowdown in myopia progression was better than that of spectacle lens wearers.
The study of J. Gispets et al. also showed that 88.7 percent of children and 95.9 percent of adults who wore Ortho-K lenses for at least a year had a predictable refractive outcome. Instances of microbial infection were also rare at 6.8 cases per 10000 patients. The researchers concluded that Ortho-K is a safe and predictable long-term refractive error-correction procedure in children and adults with a low risk due to its low incidence of serious adverse effects.
Main Disadvantages: Limitations and Critical Risks
It is important to underscore the fact that the effects of Ortho-K are temporary. This might not be ideal for individuals who want a more permanent or long-lasting solution to their vision problems or refractive error issues. Moreover, considering the fact that it requires regular wearing, habit formation is a determining factor for its positive outcomes. This method for correcting refractive errors also shares some of the disadvantages of prescription contact lenses.
Another notable drawback of orthokeratology, which is related to the fact that its vision correction effects are not permanent, is the cost. There is an initial upfront cost and an ongoing or recurring cost for replacements. Note that the initial cost could rival procedures like Lasik, and the overall or total cost over the next 5 years of continuously undergoing orthokeratology can be 6 times to 8 times higher than more long-term alternatives like refractive surgeries.
Below are the disadvantages of Ortho-K:
• Temporary Vision Correction Effects: Patients must wear the Ortho-K lenses every night or at least regularly to maintain clear vision. The entire process should be regular and part of a routine. Visual acuity often reverts to its original state within a day or two because the effects last for at least 24 hours and 72 hours at most.
• Initial Discomfort and Adaptation: Those who are not used to wearing contact lenses or have not worn a pair might find wearing orthokeratology lenses uncomfortable. It is also worth noting that these lenses are more uncomfortable than soft contacts because they are rigid gas-permeable. It can take a few days to weeks to adapt.
• Effects Are Also Not Instantaneous: Note that vision will not improve after wearing Ortho-K lenses during a single sleep time. Some experience some improvements after two to three days, while better vision can take two to three weeks in most cases. Vision may also fluctuate in the first few days until corneal reshaping stabilizes.
• High Upfront and Maintenance Costs: One of the main disadvantages of orthokeratology is its high upfront cost of between USD 1000 and USD 4000. This depends on the level of the refractive error. This cost comes from the fact that each lens is custom-made. The lenses also need to be replaced every one to two years.
• Requires Strict Cleaning and Handling: Patients should follow a strict cleaning routine and handling procedure to avoid infection. It is also worth mentioning that wearing lenses overnight can increase the risk of corneal infections. A serious condition called microbial keratitis can occur. This can even lead to vision loss.
Orthokeratology is also not for everyone. The state study of J. Santodomingo-Rubido et al. also noted that about 40 percent of children and 25 percent of adults experienced high levels of myopia progression. This could be due to severe refractive errors in which the cornea could not be reshaped enough to give clear vision. Ortho-K is ideal for mild to moderate myopia of up to 6.00 diopters, astigmatism of up to -1.75 diopters, and occasionally low hyperopia.
Certain corneal conditions also make orthokeratology either ineffective or unsafe. Some examples include keratoconus, scarring, irregular cornea curvature, dry eye syndrome, and chronic allergies and autoimmune conditions affecting corneal health. These issues prevent the lens from fitting properly or increase the risk of complications like infection or discomfort. A thorough screening is needed to ensure that the treatment is safe and effective.
In Addition: Background on Orthokeratology
Ortho-K is also known as night lenses, overnight vision correction, corneal refractive therapy, and cornea corrective contacts, among others. The foundational principle behind this method can be traced back to the 1940s when doctors discovered that glass lenses can reshape the cornea. The first orthokeratology design is credited to optometrist George Jessen who made contacts from acrylic glass. But this generally had inconsistent results.
It was in the 1980s when the first-ever reverse-zero contacts design was developed and introduced by optometrists Richard Wlodgya and Philip B. Hanisch and contact lens innovator Nick Stoyan. Their particular reverse-zero or reverse-geometry design was a leap forward in orthokeratology because it enabled controlled corneal reshaping when worn overnight. This was promising but was not practical due to technological and procedural setbacks.
However, after the arrival of computerized corneal topography in the 1990s, it has become possible to create precise and patient-specific designs based on the surface curvature of the cornea. These designs demonstrated repeatable results. Further developments resulted in the identification of better materials for rigid gas permeable lenses, the utilization of modern imaging techniques, and the deployment of newer and better manufacturing processes.
FURTHER READINGS AND REFERENCES
- Gispets, J., Yébana, P., Lupón, N., Cardona, G., Pérez-Corral, J., Pauné, J., and Cortilla, B. 2022. “Efficacy, Predictability and Safety of Long-Term Orthokeratology: An 18-year Follow-up Study.” Contact Lens and Anterior Eye. 45(1): 101530. DOI: 1016/j.clae.2021.101530
- Santodomingo-Rubido, J., Cheung, S.-W., and Villa-Collar, C. 2024. “A New Look at the Myopia Control Efficacy of Orthokeratology.” Contact Lens and Anterior Eye. 47(5): 102251. DOI: 1016/j.clae.2024.102251