ortho k travel kit

A Clinical Guide to Implementing Ortho-K in Your Practice

Ashley Wallace-Tucker, OD, FAAO, FSLS, Dipl ABO

Maria Liu, OD, PhD, MPH, MBA, FAAO

Learn the fundamentals of orthokeratology from two experts, with tips on how to identify the best candidates and speak with parents and potential patients.

• Patient selection criteria
• Study data on clinical efficacy
• Discussion points when speaking to potential candidates and their parents
• Tips on lens selection
• Marketing strategies
• Establishing an appropriate fee structure.

Candidate selection for orthokeratology lenses

Refractive error, motivation / parental support, contraindications and limitations.

• Severe dry eye syndrome or ocular surface abnormalities
• Active eye infections or inflammation
• Significant corneal abnormalities or scarring

The role of Ortho-K in myopia management

The mechanism of action of orthokeratology.

In summary:

The mechanism of the myopia-controlling effect of Ortho-K is likely multifactorial. Efforts for individual customization of lens design to optimize long-term efficacy need to consider factors such as age of onset, baseline level of myopia, pupil size and angle kappa, and corneal biomechanical properties to better predict topographical changes and subsequent optical impacts on the retina.

Studies on the efficacy and safety of orthokeratology

Long-term efficacy of orthokeratology.

• Age of myopia onset
• Level of myopia at baseline
• Lens design
• Lens decentration
• Also known as the compression factor, this value represents the extra power added to the target of Ortho-K lenses to counteract daytime regression, represented by the base curve of the lens that is flatter than the patient’s keratometry readings

Safety of Ortho-K Lens Wear

Microbial keratitis.

The safety profile of overnight Ortho-K is comparable to daytime soft contact lenses. The long-term success of this treatment relies on several key factors, including optimal lens fitting, strict adherence to lens use and care guidelines, regular follow-up appointments, and timely treatment of any complications.

Patient education and presenting Ortho-K to parents

Initial patient assessment for orthokeratology

• It helps to further rule out any corneal irregularity, such as corneal dystrophies or degenerations .
• It provides all the necessary corneal data to achieve the best contact lens design.

Orthokeratology lens selection

• Are the lenses designed through a diagnostic fitting, online calculator, or topography? What equipment is required to design these lenses?
• What is the turnaround time on lens manufacturing?
• How readily available is the consultation team?
• Manifest refraction
• Topography measurements
• Horizontal visible iris diameter (HVID)

Application and removal of Ortho-K lenses

Fitting and follow-up for orthokeratology

• Visual Acuity: Acuity with the lens on should closely match the patient’s best corrected visual acuity from the initial visit.
• Refraction Over the Lens (ROL): In order to achieve the best visual results, the ROL should be +0.50 to +1.00 to ensure neither over- or under-correction.
• Lens Fit Assessment: The lens should be well-centered with an appropriate “bull’s eye” fluorescein pattern.

Note that patients only need to wear their lenses into the office on the 1-day visit, but advise them to bring the lenses to each visit.

Handling complications from Ortho-K lenses

Marketing orthokeratology lenses, integrating ortho-k into existing services.

If a team member is particularly well versed in Ortho-K, they may be able to communicate the details in lieu of the doctor. This can be a significant time saver for physicians in busy practice settings.

Equipment considerations for Ortho-K lenses

Establishing a fee structure for orthokeratology, the final word.

• Hiraoka T, Okamoto C, Ishii Y, et al. Contrast sensitivity function and ocular higher-order aberrations following overnight orthokeratology. Invest Ophthalmol Vis Sci . 2007;48(2):550-556. doi: 10.1167/iovs.06-0914.
• Zlotnik A, Ben Yaish S, Yehezkel O, et al. Extended depth of focus contact lenses for presbyopia. Opt Lett . 2009;34(14):2219-21. doi: 10.1364/OL.34.002219.
• Erdinest N, London N, Lavy I, et al. Peripheral Defocus and Myopia Management: A Mini-Review. Korean J Ophthalmol . 2023;37(1):70-81. doi: 10.3341/kjo.2022.0125.
• Yang Y, Wang L, Li P, Li J. Accommodation function comparison following use of contact lens for orthokeratology and spectacle use in myopic children: a prospective controlled trial. Int J Ophthalmol . 2018;11(7):1234-1238. doi: 10.18240/ijo.2018.07.26.
• Liu YM, Xie P. The Safety of Orthokeratology--A Systematic Review. Eye Contact Lens . 2016;42(1):35-42. doi: 10.1097/ICL.0000000000000219.
• Huang Z, Zhao W, Mao YZ, et al. Factors influencing axial elongation in myopic children using overnight orthokeratology. Sci Rep . 2023;13(1):7715. doi: 10.1038/s41598-023-34580-3.
• Bullimore MA, Johnson LA. Overnight orthokeratology. Cont Lens Anterior Eye . 2020;43(4):322-332. doi: 10.1016/j.clae.2020.03.018.
• Lin MC, Graham AD, Fusaro RE, Polse KA. Impact of rigid gas-permeable contact lens extended wear on corneal epithelial barrier function. Invest Ophthalmol Vis Sci . 2002;43(4):1019-1024.
• Hiraoka T. Myopia Control With Orthokeratology: A Review. Eye Contact Lens . 2022;48(3):100-104. doi: 10.1097/ICL.0000000000000867.
• Gispets J, Yébana P, Lupón N, et al. Efficacy, predictability and safety of long-term orthokeratology: An 18-year follow-up study. Cont Lens Anterior Eye . 2022;45(1):101530. doi: 10.1016/j.clae.2021.101530.

Ashley Wallace-Tucker, OD, FAAO, FSLS, Dipl ABO, graduated from the University of Florida with a Bachelor of Science in microbiology and cell science before going on to graduate from the University of Houston College of Optometry (UHCO), where she earned her Doctorate of Optometry.

Dr. Tucker completed a cornea and contact lens residency at UHCO where she received extensive training and experience in the diagnosis and treatment of corneal diseases and in complex contact lens fits, including patients with keratoconus, corneal transplants, and refractive surgery. Currently, she is a partner at Bellaire Family Eye Care and The Contact Lens Institute of Houston and is the course master for the Ophthalmic Optics laboratories at UHCO.

Dr. Tucker has earned fellowships from both the American Academy of Optometry (AOA) and the Scleral Lens Education Society (SLES). She is honored to serve as a consultant for many companies, is on the advisory board for the Gas Permeable Lens Institute, is a council member for the Contact Lens and Cornea section of the AOA, and is the Community Outreach Chair for the Scleral Lens Education Society. Most recently, she was named a global ambassador for myopia management by the World Council of Optometry.

Maria Liu, OD, PhD, MPH, MBA, FAAO, is an associate professor of clinical optometry at UC Berkeley. The focus of her research and clinical expertise is the investigation and utilization of novel contact lens designs and pharmaceuticals in myopia control.

Dr. Liu is the founder and chief of the Myopia Control Clinic, the first of its kind in a teaching clinic; it now serves as a model for optometry schools across the country.

Originally from Beijing, Dr. Liu practiced as an ophthalmologist in China before relocating to the US in 2000. She obtained her MBA prior to her OD training at Pacific University, College of Optometry. She also completed an MPH and a PhD at UC Berkeley.

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Who are ideal candidates for orthokeratology?

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Spherical component of refraction, astigmatism, topography parameters, lifestyle and environment factors, dry eyes or soft contact lens discomfort, who is an ideal candidate for ortho-k.

The most important step in successful orthokeratology (ortho-k) fitting starts with identifying suitable candidates. From there, obtaining high-quality corneal topography maps, lens fitting, and adhering to an appropriate follow-up schedule define the process. If you're getting started in orthokeratology, it's a good idea to begin with a straightforward patient, such as those described below. This article will discuss who the ideal candidates are for ortho-k.

Ortho-k is well known for its robust evidence-base for myopia control, 1 and is a viable choice for patients that require correction of mild to moderate myopia. Ortho-k reliably corrects up to : beyond this, refractive and visual outcomes are less predictable. It is important to note that certain levels of refractive (myopia and astigmatism) correction will be on-label, or regulatory approved, for different ortho-k lens designs. Verifying the on-label range of an ortho-k lens design supports safe and effective practice - read more in our article on Understanding on- and off-label prescribing .

Refractive correction caused by overnight ortho-k can be attributed to the changes in corneal thickness it induces. The reverse-geometry design flattens the central cornea, inducing central corneal epithelial thinning. With high prescriptions, a greater amount of thinning is required in order to achieve full correction; hence, central corneal epithelial thickness limits the range of refractive error that is correctable via ortho-k. 2 The majority of studies on ortho-k in children set -0.50D to -0.75D of myopia as the lower limit of treatment. 1 

Although there have been some reported cases of fully corrected high myopia with ortho-k, 3 high myopes are not ideal candidates for ortho-k. The ideal levels of myopia range from -0.50D to -4.50D. 4-5 It is important to bear in mind, though, that every patient is unique and may not achieve full correction despite residing within this prescription range due to their own individual corneal anatomy and biomechanics.

Ortho-k has been shown to correct up to -3.50DC of astigmatism. 6 Spherical designs of ortho-k lenses can typically correct up to -1.50D of corneal astigmatism, so the ideal candidate would sit within this range for a straightforward ortho-k fit. Attempting to fit a spherical lens for patients with astigmatism upwards of -1.50DC will likely result in lens decentration and poorer visual outcomes. 7 With greater amounts of astigmatism through to -3.50DC, this would require a toric design for optimal fitting and refractive outcomes.

Selecting spherical versus toric ortho-k lens designs based on the 1.50DC limit comes with caveats: spherical ortho-k lenses typically fit and treat more effectively in cases of with-the-rule versus against-the-rule astigmatism. 8 It is also important to ensure that corneal astigmatism closely matches the amount of astigmatism measured during refraction. In cases of a mismatch, this may indicate the presence of lenticular astigmatism which ortho-k will not correct. This would result in residual astigmatism being present after ortho-k treatment.

One study revealed that adults older than 36 years exhibit a diminished anatomical and refractive response to ortho-k in comparison to younger adults ranging from 17 to 35 years, and children aged between 5 to 16 years. 9 While individuals over the age of 40 may still be suitable candidates for ortho-k, it is important to note that their response is likely to be reduced or delayed when compared to younger individuals using ortho-k. 9 The ideal candidate for ortho-k would be below 35 years old.

Regarding the youngest potential age for ortho-k, several studies have included children as young as 6 years old. 1 While ortho-k provides an excellent option for children, it is important to assess whether or not each individual child is suitable: are they able to handle the lenses? Are they comfortable being fit with ortho-k? Involving parents or caregivers is crucial, as they can monitor their child's lens use and hygiene practices. 1

In addition to corneal astigmatism, corneal eccentricity and apical corneal power are essential topography measures to assess at the initial lens fit. 10-11 These readings can tell you how effective ortho-k treatment will be in correcting myopia.

• Corneal eccentricity: corneal eccentricity (e-value) refers to the rate of flattening between the central and the peripheral cornea. A higher baseline corneal eccentricity is ideal as it means there is a greater difference between the central and peripheral corneal curvature, and a greater potential for change to the corneal profile. An eccentricity value of e=0.50 has been shown to correspond to an ortho-k treatment effect of approximately 2.50D; hence, ideal candidates would have an e-value of 0.50 or higher. 10 A lower e-value limits the treatment potential.
• Apical corneal power:  Higher baseline apical corneal power is associated with a greater refractive change achieved through ortho-k lens usage. When the cornea is steeper, it possesses a greater ability to undergo flattening 10-11 which is ideal in ortho-k. The corneal changes in ortho-k are more complex than just central flattening, though, so ideal baseline values for this metric are not defined in the literature and fits can be possible with a variety of values. 10,11

Ortho-k is the only non-surgical treatment option that provides freedom from daytime spectacle and soft contact lens wear. It is ideal for patients who are physically active, and especially in those that engage in water sports, which is a key risk factor for acanthamoeba infection in soft contact lens wearers. 12 Those that work in industrial occupations or dusty environments also benefit from having unaided clear vision, and so would be good candidates for ortho-k.

A patient who suffers from dry eye syndrome but does not want to wear spectacles may find that ortho-k is a viable solution. Soft contact lenses can cause or exacerbate pre-existing dry eye symptoms. 13  Ortho-k eliminates the need for daytime contact lens wear, allowing the eyes to rest from potential irritants and discomfort associated with soft contact lenses. A recent study found that overnight wear of ortho-k has minimal effects on meibomian gland function and tear film stability in children, 14 indicating that it would be a good option for those that experience soft contact lens discomfort.

Another study refit adults aged 18-45 years who had suffered ocular dryness and discomfort in soft contact lens wear into ortho-k. Around three-quarters were successfully refit, and showed improved symptoms and less conjunctival staining after 3 months of ortho-k wear. 15

Considering your patient's refractive, corneal and lifestyle factors will allow you to assess whether they are an ideal candidate for ortho-k, and streamline the fitting journey. Here is a summary of the candidate factors described above, describing the ideal candidate for ortho-k:

• Good ocular health suitable for contact lens fitting 1
• Up to 4.50D of myopia
• Up to 1.50D of astigmatism for a spherical ortho-k lens; up to 3.50D could be corrected with toric ortho-k
• Aged between 6 and 35 years. Adults older than this can wear ortho-k but treatment response may be reduced
• A higher corneal eccentricity (e-value) and higher apical corneal power can denote more treatment potential
• An active lifestyle for which the benefits of ortho-k are recognized, including water sports
• Those who are motivated to wear contact lenses but have suffered soft contact lens related dry eye symptoms

While there are software fitting systems available for ortho-k that can help you to assess topographical suitability of your patient's eyes and support lens design, 16 it is important to also assess a patient's individual, lifestyle and motivational factors to ensure success in ortho-k fitting.

Meet the Authors:

About Jeanne Saw

Jeanne is a clinical optometrist based in Sydney, Australia. She has worked as a research assistant with leading vision scientists, and has a keen interest in myopia control and professional education.

As Manager, Professional Affairs and Partnerships, Jeanne works closely with Dr Kate Gifford in developing content and strategy across Myopia Profile's platforms, and in working with industry partners. Jeanne also writes for the CLINICAL domain of MyopiaProfile.com, and the My Kids Vision website, our public awareness platform. 

This content is brought to you thanks to unrestricted educational grant from

• Vincent SJ, Cho P, Chan KY, Fadel D, Ghorbani-Mojarrad N, González-Méijome JM, Johnson L, Kang P, Michaud L, Simard P, Jones L. CLEAR - Orthokeratology. Cont Lens Anterior Eye. 2021 Apr;44(2):240-269.
• Alharbi A, Swarbrick HA. The effects of overnight orthokeratology lens wear on corneal thickness. Invest Ophthalmol Vis Sci. 2003 Jun;44(6):2518-23.
• Hiraoka T, Kakita T, Okamoto F, Takahashi H, Oshika T. Long-term effect of overnight orthokeratology on axial length elongation in childhood myopia: a 5-year follow-up study. Invest Ophthalmol Vis Sci. 2012 Jun 22;53(7):3913-9.
• Cho P, Cheung SW. Retardation of myopia in Orthokeratology (ROMIO) study: a 2-year randomized clinical trial. Invest Ophthalmol Vis Sci. 2012 Oct 11;53(11):7077-85.
• Santodomingo-Rubido J, Villa-Collar C, Gilmartin B, Gutiérrez-Ortega R. Myopia control with orthokeratology contact lenses in Spain: refractive and biometric changes. Invest Ophthalmol Vis Sci. 2012 Jul 31;53(8):5060-5.
• Chen C, Cheung SW, Cho P. Myopia control using toric orthokeratology (TO-SEE study). Invest Ophthalmol Vis Sci. 2013 Oct 3;54(10):6510-7
• Maseedupally VK, Gifford P, Lum E, Naidu R, Sidawi D, Wang B, Swarbrick HA. Treatment Zone Decentration During Orthokeratology on Eyes with Corneal Toricity. Optom Vis Sci. 2016 Sep;93(9):1101-11.
• Mountford J. Corneal and refractive changes due to orthokeratology. Orthokeratology - Principles and Practice. 2004. 175-203.
• Jayakumar J, Swarbrick HA. The effect of age on short-term orthokeratology. Optom Vis Sci. 2005 Jun;82(6):505-11.
• Mountford J, Pesudovs K. An analysis of the astigmatic changes induced by accelerated orthokeratology. Clin Exp Optom. 2002 Sep;85(5):284-93.
• Chan B, Cho P, Mountford J. Relationship between corneal topographical changes and subjective myopic reduction in overnight orthokeratology: a retrospective study. Clin Exp Optom. 2010 Jul;93(4):237-42.
• Carnt N, Stapleton F. Strategies for the prevention of contact lens-related Acanthamoeba keratitis: a review. Ophthalmic Physiol Opt. 2016 Mar;36(2):77-92.
• Markoulli M, Kolanu S. Contact lens wear and dry eyes: challenges and solutions. Clin Optom (Auckl). 2017 Feb 15;9:41-48.
• Ruan J, Zhang Y, Chen Y. Influence of overnight orthokeratology on tear film and meibomian glands in myopic children: a prospective study. BMC Ophthalmol. 2023 Apr 3;23(1):136.
• Duong K, McGwin G Jr, Franklin QX, Cox J, Pucker AD. Treating Uncomfortable Contact Lens Wear With Orthokeratology. Eye Contact Lens. 2021 Feb 1;47(2):74-80.
• Chan KY, Cheung SW, Cho P. Clinical performance of an orthokeratology lens fitted with the aid of a computer software in Chinese children. Cont Lens Anterior Eye. 2012;35(4):180-184.

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How to Add Ortho-K to Your Toolkit

This valuable service may require thorough education but will provide enormous benefits to your patients and practice..

 By Dan Fuller, OD

Practitioners have been called upon to adopt an unprecedented amount of flexibility due to the uncertainties caused by the COVID-19 pandemic. Business plans that were forward-looking into one-, three- or even five-year periods must now require significant revision. It may seem odd to discuss adding new services to your practice while trying to recover losses to your core business, but it is essential to address both the immediate needs and the growth of your practice. Looking for ways to capture new patients, offer new services to existing patients and grow your practice remain crucial aspects of your business even during a crisis.

In his venerable work Out of the Crisis , W. Edwards Deming presented 14 key management points. 1 The first of which is, “Create constancy of purpose toward improvement of product and service, with the aim to become competitive, to stay in business and to provide jobs.” You can leverage existing resources to add orthokeratology (ortho-K) to your practice without a large capital investment. This article offers both strategic and practical ideas on how to incorporate ortho-K into your business plan.

Setting up a comprehensive myopia management program includes considerations of behavioral changes (e.g., more outdoor time), anti-muscarinic agents (primarily low-dose atropine), soft multifocal contact lens and overnight ortho-K interventions. 2,3 

Ortho-K lenses are sometimes, although rarely, prescribed for use during the day. Our colleagues outside the United States have access to other options, including novel spectacle lens designs, which are projected to become available in the United States in 2022. 4-6 Even if you do not have access to, or choose not to offer, pharmacological or spectacle interventions, you can offer the contact lens options. Regardless, remain informed of approved and off-label technologies and future developments. If you don’t, your patients or their parents will.

Program Administration

When dealing with special populations such as pediatric patients, you must obtain informed consent from the parents and assent from the patient, if possible. This process varies across the globe, but informed consent must be provided verbally and in writing with signatures from the responsible parties. 7,8 Copies of these documents should be retained in the patient’s file. 

Provide the parent a packet of materials that includes the informed consent document, discussion of the procedure and device prescribed, schedule of visits, discussion of fees and what they cover, payment plans, warranties, how lost or damaged lenses will be replaced and cancellation policies. Also include training materials, a care kit, instructions for lens care and the handling and wearing schedule. Provide clear guidance on what to do if they experience an adverse event and provide your after-hours contact information.

Indications

Ortho-K lenses are enjoying a resurgence due to the worldwide myopia epidemic. They represent approximately 8% of the rigid contact lens market (0.7% of all contact lens fits) in the United States and 3% of all lens fits worldwide (range <1% to 30%). 9,10 The FDA requires optometrists to complete a certification course for each design before they can offer them in their practice ( Table 1 ). 11 The indications for ortho-K include the temporary reduction of myopia, slowing of myopia progression and as an alternative for soft contact lens wearers experiencing dry eye. 1,11,12  

(*VST includes a family of 15 different designs)

Ortho-K Candidates

Above all else, the patient and/or parent needs to be motivated to partner with you in their care over an extended period of time.Ortho-K does not permanently correct myopia, and clinicians must carefully assesss patient and parent expectations. Also, the effects regress after cessation of wear at variable rates for individual patients. Elimination or even slowing of myopia progression cannot be guaranteed, and adverse events (though uncommon) do happen. Patients with histories of non-compliance, allergies, preexisting lid or corneal disease may need to be treated to resolution prior to considering a fit. 13-19 The ability of the patient or family to comply with care, hygiene, handling and return visits, requires special consideration prior to embarking on any overnight wear of a contact lens. 

None of the currently FDA-approved designs have an age restriction. None of the designs approved in the United States possess an indication for myopia control. Outside the United States, the Bloom lens (Menicon) carries this indication. 20 Both adult and pediatric patients who have never worn a lens before may adapt faster than previous soft lens wearers who may be inclined to compare ortho-K designs with their habitual soft lenses. 

Patients who have reduced their wearing time due to dryness or discomfort as well as those who wish to temporarily reduce their myopia make great candidates. If the intent is to slow myopia progression, then the earlier you identify onset and progression of myopia, the earlier you can intervene. Research has found a more rapid progression of their myopia in the year prior to onset and a slower rate after onset in children between six and 14 years old. 21  

Evidence for Efficacy

The Blue Mountains Eye Study from Australia found myopic maculopathy increases with the amount of myopia, with 43% of cases occurring in myopes less than 5.00D. 22  This has led to the often-quoted statement that there is “no safe amount of myopia.” 23  Any amount of myopia reduction is important, with a 40% decrease in risk of maculopathy for each 1.00D reduction in progression. 24 

Clinicians must monitor axial length changes to accurately track progression since orthokeratology reshapes the corneal surface. The corneal epithelium under the treatment zone thins while the midperipheral area in the reverse curves thickens to create the effect. 25  A change in axial length of 0.1mm roughly equates to 0.20D to 0.25D. 1  

Comparisons of the safety and efficacy of ortho-K across studies is difficult because of variations in inclusion criteria, presence/absence of controls, lack of masking and methodological differences. Nonetheless, a summary of four representative meta-analyses reported remarkably consistent reductions in the progression of axial length in the range of -0.25mm to -0.27mm ( Table 2 ). 1,12,26-29 

Evidence for Safety

The risks associated with ortho-K are less well understood but are likely similar to those of other designs. Risk factors include overnight wear, use of tap water, and topping off solutions. 12,26 The majority of published reports come from Asia and ortho-K is more widely used, where conditions of sanitation may vary, and suggest causative organisms encountered are overwhelmingly Pseudomonas aeruginosa or Acanthamoeba . 17,30-32  

Incidence data on rates of microbial keratitis are elusive but may be similar to overnight soft lens wear—between 19.5 to 25.4 per 10,000 wearers. 12 Adverse events (corneal infiltrative events, including infection) in soft lenses appears to be comparable to adults and may be less in the eight- to 11-year-old age range. 33 It is not clear whether this is true of ortho-K. In a retrospective study of gas permeable (GP) lens wearers who experienced Acanthamoeba keratitis, 24% wore ortho-K lenses but no odds ratio could be calculated. 30 Research also shows that Pseudomonas aeruginosa binding to the corneal epithelium increases after overnight ortho-K wear. 34  

Initial Examination

The initial exam deviates only slightly from your usual standard routine for a contact lens wearer. There are a few additional tests that are important to facilitate the fit and track individual success, such as cycloplegic refraction, axial length, topography or tomography, pupil size and corneal diameter measurements. 35 Many devices are capable of collecting this information, including a number of combination instruments. These contemporary devices can easily upload data to your lab to further assist in fitting. Be consistent when using these devices for each visit because agreement varies significantly between instruments. 36,37  

Cycloplegic refraction decreases the likelihood of over-minusing the patient. Some consider this an optional step, but, since a baseline fundus evaluation is important, it can be easily incorporated into the first visit. Tracking changes in axial length over time is a more reliable measure than changes in refractive error that are influenced by the reshaping of the corneal surface. Assessing pupil size in both ambient and low light conditions helps ensure the treatment zone of the lens will be optimized to reduce risks of flare or glare. Assessing corneal diameter ensures the overall diameter of the lens will not exceed that of the cornea and improve lens centration.

Tomography, such as the Pentacam (Oculus), relies on a rotating Scheimpflug camera and not a reflection of a Placido disc. It is not subject to errors induced by an unstable tear film and measures true corneal height as well as elevation data. 38  

Placido disc topographers generally do not cover as large a region of the cornea as a tomographer, but there are some devices that allow you to stitch or tile together images from different fields of gaze to cover a larger surface area, such as the Medmont E300 (Medmont). This can be important when evaluating whether corneal astigmatism is confined to the central cornea or extends out toward the limbus, improving parameter and design selection. The two types of devices may offer the ability to model contact lens fits without putting a lens on the eye and may even generate simulated fluorescein patterns from the height data. 

The ability to create subtractive or comparative maps is an essential feature on both devices. Topographical findings that make ortho-K more challenging include irregular astigmatism, high astigmatism, limbus-to-limbus astigmatism, decentered corneal apex and asymmetries. 39 Topographical attributes that are positive indicators include well-centered apex near the geometrical center of the cornea, K values between 41.00D and 45.00D, with-the-rule astigmatism <1.50D and average corneal eccentricity between 0.25 and 0.80. 39 Axial maps are useful for comparing patients while obtaining a general overview, tangential maps provide more data on localized shape changes induced by ortho-K, and difference maps will allow you to track changes ( Figure 1 ). 39

The data you collect helps determine whether to select a diagnostic trial lens, employ a fitting nomogram, submit electronically to the lab or to empirically design the lens using software. 35 All are viable options ( Table 3 ). 40 As you gain more experience, you will likely want more control of the design process and may wish to use design software. Avoid using design software until you gain the deeper understanding of how to manipulate parameters to achieve a desired effect. Trial lenses can expedite the fitting process for anxious parents/patients, where empirically designed lenses can be more customized to topographical features. 

You want a well-centered lens, with an aligned area of approximately 4mm in the treatment zone, pooling in the return zone where the reverse curves are 1mm to 2mm wide, then an alignment zone of similar width and finally enough edge lift to create a band of pooling of 0.5mm and ensure adequate tear exchange. The lens should move on the blink but not to the point it moves outside the corneal diameter ( Figure 2 ). 35

Once the amount of flattening for the myopia + Jessen factor have been incorporated into the base curve, you will seldom need to modify this parameter unless you determine undertreatment. In that case, you may flatten the base curve or increase the diameter of the treatment zone. More commonly, you will find you may need to modify the reverse curve, or the toricity of the reverse or alignment curves. The reverse curve contributes to decreasing the myopia slightly as you flatten this curve, thereby reducing the sagittal depth and eliminating a central island identified by topography. But mostly the reverse curve improves lens centration by manipulating the sagittal depth of the lens. 

A low riding lens leaves a “frowny face” on your topography, and a high riding lens creates a “smiley face.” Modify the reverse curves and/or alignment curves by increasing or decreasing the sagittal depth, respectively. Smaller adjustments may be made by changing the landing zone angle on some lenses. In cases of corneal astigmatism that is limbus-to-limbus, these curves may need to be toric rather than spherical. 35

Ortho-K for hyperopia and presbyopia (monovision) is an option; however, it’s not as well studied as it is for myopia. Nonetheless, studies with GP designs with base curve radii fit 0.4mm to 0.7mm steeper than flat K have shown success and reversibility with up to 28 hours of wear. 40 The designs also have an impact on steepening of the treatment zone, flattening in the reverse zone and a positive shift in spherical aberration (as well as other HOAs). 40-43

Follow-up Scheduling

The timing of return visits after dispensing are dictated by the individual needs of the patient. A typical schedule would be the morning after the first overnight wear period, one week and then one, three and six months. 8 Once the desired effect is achieved, six-month intervals are fine. Assess the centration by topography and unaided visual acuities at every visit along with the ocular health, compliance and reinforce education. At one week, you will add a manifest refraction and you should be at or near your target of +0.50D to +0.75D of hyperopia. 37 At six months, include axial length measurements to assess progression.

Continue educating yourself and consider adding this valuable service to your practice. Understanding myopic progression and control should become part of every primary care practice. There are numerous opportunities to acquire the proper training on ortho-K through continuing education programs at major meetings, dedicated societies and manufacturer online certification courses. 

Adding ortho-K to your practice is a win for both patients and the economic health of your practice. It is immensely satisfying to change lives and reduce the risk of future morbidities through early intervention. You will also see how highlighting this service will benefit your practices.

Dr. Fuller is a professor and founding supervisor of the Cornea & Contact Lens–Refractive Surgery residency at The Eye Center at Southern College of Optometry. He is also a Diplomate of Cornea, Contact Lenses and Refractive Technologies for the American Academy of Optometry.

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