For decades, orthokeratology (ortho-k) has been an outstanding option for patients seeking an alternative to refractive surgery or daytime correction. In more recent years, myopia has been elevated to “pandemic” status, meaning that if the current rate of myopia continues, 50% of the world’s population will be myopic by 2050 (Figure 1).¹ Consequently, the attraction to ortho-k has expanded from simple myopia correction to myopia management.

This article will travel through time, detailing the fascinating history of ortho-k and discussing how and why it has evolved into one of the most popular and effective options for myopia management. The article will delve into how to implement ortho-k in a clinical practice, from the basics of fitting and troubleshooting to creating and marketing a successful, comprehensive ortho-k program.

THE BEGINNING

In the 1960s, an innovative optometrist named George Jessen introduced the novel concept of “orthofocus” at the meeting of the International Society of Contact Lens Specialists in Chicago. “Orthofocus” consisted of daytime wear of polymethylmethacrylate (PMMA) lenses fit flatter than the corneal curvature by the amount of refractive myopia as a form of vision correction.² At the same meeting, Jessen’s mentor, Newton Wesley, OD, MD, ScD, PhD, proposed the alternative name of “orthokeratology,” which has remained the same despite the evolution of its exact definition over time.³ In 1976, Ronald Kerns, OD, defined ortho-k as “the reduction, modification, or elimination of a refractive error by the programmed application of contact lenses.”⁴ Interest in ortho-k grew over the next several years as a number of eyecare practitioners pursued further clarification and knowledge through a series of clinical studies. Most studies showed that, although ortho-k lenses were safe and resulted in reduction of myopic refractive error, the results were temporary, variable, and unpredictable.^5-9 Consequently, excitement diminished and ortho-k took a temporary back seat in the vision care community.

Throughout the 1980s and early 1990s, three innovations drastically changed the trajectory of ortho-k and caused a resurgence in its popularity:

• Development of higher GP rigid lens materials
• Introduction of reverse geometry designs
• Availability of computer-assisted videokeratography (now known as corneal topography)

After GP materials were developed and became readily available to practitioners, the significantly increased oxygen transmissibility (Dk/t) of these materials made it possible for ortho-k lenses to potentially be worn safely and effectively overnight. Hence, the more modern concept of “overnight orthokeratology” was introduced, in which ortho-k lenses are worn only during the night, providing a temporary reduction in refractive error and freedom from daytime correction.^10,11

Arguably the most notable development was the advent of reverse geometry lenses. Conventional rigid lenses are designed based on the natural shape of the cornea—a central base curve radius (BCR) aligned with the central cornea surrounded by a series of progressively flattening peripheral curves. In contrast, a reverse geometry lens is designed with the desired outcome of temporary corneal flattening—the BCR is flatter than the central corneal curvature and the peripheral radii are steeper than the BCR.¹² Over time, this basic ortho-k design has been modified and improved upon, resulting in more rapid, desirable, and predictable clinical results. It is also important to note that around this same time, computer-guided lathes were developed, allowing relatively simple fabrication of these sophisticated lens designs.

Corneal topography provides a wealth of information about an individual’s corneal structure and integrity. This tool is invaluable in screening for ortho-k candidacy, designing lenses, and troubleshooting undesirable outcomes. Prior to this technology, practitioners had to rely on much more rudimentary data like subjective interpretation of sodium fluorescein (NaFl) patterns and keratometry values for troubleshooting. Today, corneal topography is considered a necessary tool in clinical practice to successfully manage ortho-k patients.

THE ROLE OF ORTHO-K TODAY

Although ortho-k is still an attractive alternative to daytime correction, the allure of ortho-k has shifted beyond the temporary myopic refractive error reduction to include its efficacy in myopia management and control (slowing the progression of myopia). In 2010, the estimated global incidence of myopia was 28% and, as noted earlier, the incidence is predicted to skyrocket to 50% by the year 2050—the equivalent of 5 billion people worldwide.¹ Furthermore, approximately 10% of those individuals will have high myopia (-6.00D or more).¹ Due to these alarming predictions, interest in myopia management from both patients and practitioners has greatly escalated over the last decade.

There are two goals of myopia management: prevent/delay the onset of myopia and slow the progression of myopia. Realizing both of these goals will reduce an individual’s risk of ocular and retinal pathology. Myopia results from axial elongation. Axial length (AL) is defined as the sum of the anterior chamber depth, lens thickness, and posterior chamber depth and typically increases from 16.8mm in infancy to 23.6mm in adulthood.¹³ On average, the expected increase in AL for an emmetropic child aged 8 years or younger is approximately 0.20mm/year.¹⁴ However, the ALs of myopic children of the same age tend to elongate more quickly at approximately 0.34mm/year.¹⁵ The rate of elongation tends to decrease with age but can vary significantly.¹⁵

Axial elongation is directly correlated with myopes being at greater risk for developing primary open angle glaucoma, cataract, retinal detachment, and myopic maculopathy.¹⁶ The probability of developing one or more of these conditions increases greatly with the severity of myopia, furthering the importance of myopia management for the patient.¹⁷

Currently, there are several options for myopia management, including lifestyle changes (i.e., more outdoor time and increased near working distance), pharmaceutical therapy (i.e., anti-muscarinic agents—off-label), spectacles (currently not commercially available in the United States), soft contact lenses, and ortho-k. Although each of these options plays a significant role in the realm of myopia management, ortho-k presents an option with unique advantages.

1. Efficacy There is undeniable evidence that peripheral refractive error is a leading factor in axial elongation and thus myopia progression.¹⁸ Thus, in order for spectacles or contact lenses to be effective in myopia management, we now know that they must provide myopic defocus to the peripheral retina as opposed to hyperopic defocus driving AL elongation.¹⁸ The resultant shape of the cornea from the reverse geometry lenses utilized in ortho-k—central flattening and mid-peripheral steepening—imposes myopic defocus on the peripheral retina, decreasing the stimulus for axial elongation. The anatomical change to the cornea induced by ortho-k is unique when compared to any other form of myopia management. Ortho-k has been shown to slow AL elongation by approximately 0.25mm over a two-year period, which is equivalent to slightly less than 50% of the expected amount of growth in an age-matched population.^19-21
2. Convenience Ortho-k provides freedom from daytime correction, which is ideal for patients who lead an active lifestyle. Athletes of all kinds enjoy the benefit of excellent vision while playing sports without the burdensome need for daytime contact lenses or spectacles. In addition, parents of young children are particularly drawn to ortho-k; ortho-k allows the parent to be in control of application, removal, and care of the child’s contact lenses within the home until she is sufficiently mature to handle them on her own. This is all the more important, as it’s becoming increasingly common for children younger than the age of 8 years to present with mild to moderate myopia.²²
3. Vision Correction Ortho-k is used for the temporary reduction of myopia in patients generally manifesting up to –6.00D of myopia and –1.75DC of astigmatism. Recently, one ortho-k lens design has gained U.S. Food and Drug Administration (FDA) approval for myopia management and is indicated for patients who have up to –4.00D of myopia and –1.50DC of astigmatism. The only FDA-approved soft contact lens for myopia control is a multifocal design and is indicated for patients who have low astigmatism—typically up to –0.75DC. Thus, patients who have a mild to moderate level of corneal astigmatism will likely benefit optically from wearing ortho-k lenses instead of soft lenses due to the resultant astigmatism. It is important to note that there are several other contact lenses, including ortho-k designs, that are not FDA-approved but can be used off-label for myopia management. These may be beneficial as well for patients who have higher myopia and astigmatism.

CHOOSING AN APPROPRIATE PATIENT

In addition to having an appropriately eligible refractive error, a patient’s topography should ideally have a well-centered apex near the geometrical center of the cornea, vertical and horizontal symmetry, an average apical radius between 41.00D and 45.00D, with-the-rule astigmatism of less than –1.50DC, and an amount of eccentricity between 0.25 and 0.80.²³ Other considerations are pupil diameter of 6.00mm or less in dim illumination and normal lid anatomy and ocular health.

What age is appropriate for ortho-k? This is one of the most common questions among practitioners. Studies suggest that children between the ages of 6 and 9 years who experience an increase in AL of > 0.20mm per seven months and/or spherical equivalent of myopic progression of > 1.00D per year are ideal candidates for ortho-k lenses.^19,21 It may be equally appropriate to focus on the patient’s maturity level and the parent’s willingness to assist the patient, which could make virtually any age appropriate.

Patients should also demonstrate a commitment to ortho-k lens wear to ensure both consistent vision and proper myopia management. Compliance with the recommended care regimen is key to preventing adverse events and infections. These patient expectations, along with the necessary follow-up schedule, should be clearly delineated and agreed upon prior to onset of treatment. Consider creating an ortho-k contract to further solidify the commitment the patient makes to the process and the practitioner’s commitment to the patient, in addition to informed consent when working with minors and their parents, especially using off-label therapies.

BASIC FITTING GUIDELINES

Although practically every contact lens manufacturer has an ortho-k design with its own nomenclature and fitting nuances, the basic principles of fitting ortho-k lenses are consistent across all designs. Depending on the particular lens design or the practitioner’s fitting philosophy, an ortho-k lens can be created in a variety of ways, including in-office diagnostic fitting, manufacturer-specific fitting nomograms, topography-based fitting software, or empirical fitting. The ultimate goal, regardless of the method, is to create a well-centered lens with the following attributes observed with the slit lamp and NaFl:²³

• Treatment zone/BCR: approximately 4mm dark area of uniform central alignment, should be centered over the pupil indicating uniform fluid force
• Return zone/reverse curve: 1mm to 2mm ring of NaFl pooling under the lens, should have a consistent width of 360º, indicating an outward fluid force
• Alignment curve: 1mm to 2mm ring of 360º of uniform alignment, allowing for proper centration
• Landing zone: 0.5mm ring of uniform NaFl pooling at the periphery of the lens, ensuring adequate edge lift and tear exchange

This pattern is often referred to as a “bull’s-eye pattern”²³ (Figure 2). The lens should also demonstrate slight movement—no more than 1mm to 2mm upon blinking. Inadequate or excessive movement would warrant alteration of one or more of the lens parameters. It may also be important to see these patients for follow-up care early in the morning (particularly when newly fitted) to ensure that the lenses are not binding to the cornea during sleep.

PATIENT EDUCATION

The key to a successful ortho-k experience is compliance with lens wear and care instructions. It is our duty as practitioners to clearly communicate these details to the patient. Furthermore, providing written instructions for the patient to take home will further emphasize the importance of proper compliance.

When they are worn overnight, it is imperative that extra precautions are taken to ensure that no contaminants are introduced onto the lenses. First and foremost, proper handwashing prior to starting the application process is critical. Antibacterial soaps without oils or moisturizers are ideal to prevent lens deposits and/or ocular sensitivity; ensure that the hands are dried completely with a lint-free towel. In order to disinfect the lenses, it is advisable to follow the specific manufacturer’s guidelines but, in general, GP multipurpose solutions and peroxide-based systems are safe and effective. For patients who have a sensitivity to preservatives, the peroxide-based system is a better option. In addition, these patients may want to rinse their lenses with a preservative-free saline prior to lens application. Under no circumstances should patients use tap water to rinse or store their lenses.^23,24

For patients using a suction device to remove their lenses, advise them to disinfect it weekly with warm soapy water and replace it every six months. Be sure to provide the patient with extra devices to prevent overuse and to allow the patient to have backups when necessary. Additionally, contact lens cases should be cleaned daily, and allowed to air dry, and replaced every one to three months.²⁵

For application and removal training, it is very helpful for patients to have access to a training video in addition to having in-office one-on-one training to further encourage their success. Depending on the patient’s age and maturity level, a parent may be the initial person in charge of application and removal. In this instance, consider revisiting the idea of the patient taking charge of application and removal once he is more comfortable and confident with the process.

FOLLOW-UP CARE

Follow-up visits for ortho-k serve a dual purpose—assess the health of the cornea and ensure proper treatment. The recommended follow-up schedule is as follows: the morning after the initiation of treatment, one week after initiation, one month after initiation, three months after initiation, six months after initiation, and six months later for the annual examination. After the first year of treatment, if the desired results have been achieved, follow-up every six months is sufficient.²⁶ This schedule, of course, varies depending on each patient’s unique situation. If the patient requires a lens change, allow at least one week of treatment prior to seeing the patient back in the office.

Each follow-up visit should include:

• History: subjective assessment of visual acuity (quality and regression), update on application and removal success, amount of wear time, comfort of lenses, impact on sleep
• Visual acuity: check unaided monocular and binocular acuity
• Slit lamp evaluation: thoroughly assess ocular health with NaFl for signs of lens binding and other issues
• Corneal topography: assess treatment pattern and centration
• Manifest refraction: can oftentimes be difficult post-treatment but may provide helpful information for troubleshooting

Measuring AL is quickly becoming standard of care for myopia management. Manifest refraction is not valid for ortho-k patients in terms of myopia progression, so measuring AL is a more conclusive method of tracking progression. On average, 1D change in refractive error corresponds to 0.28mm increase in AL for children aged 6 to 7 years and 0.32mm for children aged 12 to 13 years.²⁷ This should be measured every six months.²⁵

At each visit, review proper wear and care instructions. Periodically, assess the integrity of the lens with a contact lens magnifier (loupe).

BASIC TROUBLESHOOTING TIPS

Although troubleshooting can be attempted without the use of a topographical map, it is highly recommended that one be obtained to determine the exact fitting issue and potential solution. In most cases, the need for troubleshooting will most likely commence with the patient reporting reduced or undesirable unaided vision.

Even though it may seem intuitive to simply flatten the BCR to obtain more myopic treatment, resist the urge to do so, especially before carefully assessing the patient’s topography. In most cases, undesirable vision is not simply a result of the BCR needing to be flattened. Typically, the appropriate amount of corneal flattening to offset the refractive myopia plus the Jessen factor (value added to allow for any potential regression of myopic refractive error during the day) is accounted for during the lens design process. In the event there is a myopic over-refraction during the fitting process or residual myopia during post-lens wear manifest refraction, flatten the BCR by the amount of under-correction.

More often, undesirable vision is due to a poorly fitting lens. Each of the following findings are best observed using the difference map (either tangential or axial), which can be used to compare a baseline map to any other reference map. The tangential map is especially useful when assessing centration of the treatment zone²³ (Figure 3).

Small Treatment Zone If the patient reports visual disturbances like haloes/glare, the treatment zone may be too small. Increase the treatment zone or decrease the sagittal depth by flattening the reverse and/or alignment curve.

Superior Decentration If the ortho-k lens is sitting high, the fit is too flat, and the resultant topographical map will appear as a “smiley face.” Increase the sagittal depth of the lens by steepening the reverse curve and/or alignment curve.

Inferior Decentration If the ortho-k lens is sitting low, the fit is too steep, and the resultant topographical map will appear as a “frowny face.” Decrease sagittal depth of the lens by flattening the reverse curve and/or alignment curve.

Lateral Decentration If the ortho-k lens is decentered either nasally or temporally, the overall diameter of the lens may be too small. The sagittal depth may also need to be increased or the patient may require toric reverse and/or alignment curves.

Central Island This appears when there is a small defined area of steepening within a flatter treatment zone. Decrease sagittal depth of the lens by flattening the reverse and/or alignment curve.

IDEAS FOR SUCCESSFUL IMPLEMENTATION AND MARKETING

Offering ortho-k as a form of myopia management in practice requires an extremely precious commodity—time. The number of myopic children is on a sharp incline but only 1 in 3 parents actually know the true definition of myopia.²⁸ Thus, there must be sufficient time to effectively and thoroughly educate the patient and parents on myopia and the importance of myopia management. For most practitioners, it is nearly impossible to achieve this during the time allotted for a normal examination; therefore, there are two options: schedule a consultation visit or have the patient meet with a trained team member.

A consultation is typically scheduled after the annual exam has been completed by either the routine eyecare practitioner or a referring practitioner. A consultation visit has many benefits, including a designated time for the physician and family to extensively discuss all options; questions can be answered in a non-rushed environment, and the practitioner has a prime opportunity to connect with the child and build rapport. Parents truly appreciate this one-on-one personalized visit. It is imperative that all options, not just ortho-k, be presented in order for the pros and cons of each method to be fully considered.

Alternatively, it may also be advantageous to capture the family while they are in the office for the annual examination in lieu of scheduling an additional visit. In this scenario, the topic of myopia management is fresh in the parents’ minds and the interest level is typically quite high. Having a well-trained myopia management advocate can be a game changer in situations when time is of the essence. This individual should essentially provide the same information that the practitioner would provide during a consultation visit. If possible, the practitioner should circle back around to the family when time permits and offer closing thoughts or answer any last-minute questions.

Finally, all myopic patients, regardless of whether they have shown interest in myopia management or not, should receive a packet of information on their way out of the office. This packet should include current literature about the benefits of myopia management, a summary of all their myopia management options, and the practitioner’s contact information, in case they have any additional questions. This packet serves a dual purpose: reinforcement of all that was discussed in office and a reminder of the importance of following through with one or more of the practitioner’s recommendations.

Although the concept of ortho-k is quite unique when comparing it to other forms of myopia management, it is actually simple to market. Word-of-mouth is often the biggest form of marketing. It only takes one successful patient to start spreading the word to their network of friends and family. Featuring ortho-k in an office newsletter and social media posts and having signage around the office is also effective in creating buzz about this service (Figure 4). Finally, reach out to sports groups, parent-teacher organizations, and school nurses and offer them written materials about ortho-k or request an opportunity to speak with them in person.

RESOURCES

The absolute best source of information about your chosen ortho-k lens is the manufacturer’s consultant. The consultants provide a plethora of expertise and can assist in troubleshooting virtually any issue with their lens design. When preparing for a discussion with a consultant, having the following information is immensely helpful: manifest refraction before and after treatment, over-refraction with the lens on the eye, assessment of the NaFl pattern of the lens, and assessment of the topography. For even better accuracy, sending a photo of the NaFl pattern and the topography to the consultant can save time and provide better feedback in the long run.

For more general information on ortho-k, there are several excellent options available for continuing education each year. Ortho-k has become a really hot topic, especially for myopia management; thus, you can find several lectures about it at essentially every major optometric meeting and local society meeting. For a more intensive track on ortho-k, consider attending the Global Specialty Lens Symposium or the Global Myopia Symposium. CLS

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