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April 15, 2024
By Dr. Andrew Brauer
OrthoK is challenging to master, but leveling up your topography skills will enable you to achieve clinical results that wow your patients and make them want to tell their friends.
Orthokeratology is exploding in popularity, and a recent survey, The Fitting of Orthokeratology in the United States (FOKUS), suggests that this trend will only continue.1 If you’re already providing this fantastic treatment to your patients, great! Or, if you’re feeling intimidated and don’t know where to start, that’s okay! Just know, there’s never been a better time to start your OrthoK practice. But let’s not get ahead of ourselves — you can’t master OrthoK, or any corneal GP fitting for that matter, without knowing your way around the cornea.
Embrace the Corneal Topographer
If you’re fitting OrthoK lenses, a topographer (or tomographer) is absolutely essential. In fact, the AAOMC (American Academy of Orthokeratology and Myopia Control) puts topography in their fellowship requirements.2 Modern topographers can collect thousands of data points and allow the optometric physician to display that map data in a variety of helpful ways.3 To name just a few, you’ll look at elevation maps to determine whether you need a spherical, toric, or free-form lens. The tangential maps will be used to evaluate the treatment position on the eye, and the axial maps provide information on the treatment area, how large, smooth, and even treatment area you’re achieving. Some lens design platforms, like one we’ll talk briefly about later, will automatically display subtractive maps using the data for you by default.
Quality Data is Key
Corneal topography, like many things in life, follows a simple equation: garbage in = garbage out. For this reason, you’ll need to scrutinize your data heavily. Because most of the devices in current use are placido-based systems, they don’t actually measure the cornea, but rather the reflections off the tear film.4 Knowing this is key to capturing and utilizing clean maps for your lens design. An irregular tear film can masquerade as an irregular cornea, and designing a lens with poor baseline data can lead to a lot of heartache.
You Are Now Entering the Tangent Zone
Speaking of lens design, it’s a good time to review the basics of the OrthoK concept. An OrthoK lens is engineered to produce a specific tear film pattern (thin centrally and thick mid-peripherally), and that’s the brilliance of its design. The tangent zone, at the more peripheral part of the cornea, is the only place where the lens and the cornea actually touch. A key point here: auto keratometers will typically measure the central 3 mm, so if you’re designing an OrthoK lens the old-fashioned way with just the keratometry values and refraction, you’re literally guessing on the most important part! The tangent zone allows the lens to align on the cornea. Then, you have the reverse curve that, in conjunction with the base curve, creates the pressure gradient and encourages distribution of the epithelial layer. Think of your tangent zone as the foundation for everything else, and make absolutely sure that you’re building it on solid topographical ground.
Good Topography Data is the Foundation You Build On
To that end, it’s important to remember that just because you managed to capture topography data (even if your reliability indices are high), that doesn’t mean your data is good. Recall that in most cases, we’re measuring tear film reflections, and that can have major implications.5 If the tear film is irregular or you’re scanning a blinker, consider instilling an artificial tear to normalize the tear film and make it easier for the patient to keep their eyes open. You can use a cotton-tipped applicator to lift the upper lid and a thumb to pull down on the cheek to get the lid aperture as wide open as possible. If you find yourself needing more hands, don’t be afraid to enlist some help. Resist the urge to rush this part — an excellent baseline topography scan in OrthoK is one of the most irreplaceable measurements we take. Capture several scans and look for consistency. If one doesn’t look like the others, there’s probably an error in the outlier. Discard it. You know that OrthoK lenses land around an 8 mm chord, so at minimum, you’ll need good data to be about 4 mm in every direction from the corneal apex. The bigger the map, the better. The next step is to turn off the color map and just look at your Placido rings. This will make it easier to spot abnormalities, like those caused by transient mucous strands, dry spots, excessive lacrimal lakes, or even punctate corneal erosions. With our best maps in hand, it’s time to design the lens.
Using Your Topographer for Orthokeratology Fitting
The modern optometric physician has a wealth of OrthoK lens choices. One that I’d like to highlight is the ACUVUE Abiliti Overnight. Johnson & Johnson MedTech intended it to harness the awesome power of your topographer and to help simplify the process. Fitabiliti, the lens fitting software, seamlessly imports all the topography data you worked so hard to capture and will help guide you through the fitting process. The topography maps will also be key in monitoring your patient at the subsequent follow-up visits. The fitting consultants, or Advanced Lens Support, have been helpful when fitting guidance is needed.
OrthoK is challenging to master, but leveling up your topography skills will enable you to achieve clinical results6 that wow your patients and make them want to tell their friends. Join the movement. Your future patients will thank you.
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Dr. Andrew Brauer works for his wife Nicole in a private practice in the Chicago suburb of Westmont, where he specializes in OrthoK, myopia management, and scleral lenses. He enjoys collaborating with industry partners and helping colleagues incorporate specialty lenses into their own practices. Away from work, he loves spending time with his amazing wife, three fantastic kids, and best friend Thunder (a black lab mix). |
References:
- Lipson, M. J., & Curcio, L. R. (2022). Fitting of Orthokeratology in the United States: A Survey of the Current State of Orthokeratology. Optometry and vision science: official publication of the American Academy of Optometry, 99(7), 568–579.
- “How To Apply.” AAOMC | Orthokeratology and Myopia Management; https://aaomc.org/how-to-apply/
- Wilson SE, Klyce SD. Advances in the analysis of corneal topography. Surv Ophthalmol. 1991 Jan-Feb;35(4):269-77. 2.
- Greenwald MF, Scruggs BA, Vislisel JM, Greiner MA. Corneal Imaging: An Introduction. EyeRounds.org. Posted October 19, 2016; Available from: https://eyerounds.org/tutorials/corneal-imaging/index.
- Kojima, R. (2007, July 1). Validating corneal topography maps. Contact Lens Spectrum.
- Vincent, SJ et al. CLEAR – Orthokeratology. Cont Lens Anterior Eye. 2021;44(2):240-269
Important Safety Information
ACUVUE Abiliti Overnight Therapeutic (tisilfocon A) Contact Lenses are indicated for use in the management of myopia. They are indicated for overnight wear for the temporary reduction of myopia and should only be disinfected using a chemical disinfection system. As with any contact lens, eye problems, including corneal ulcers, can develop. Some wearers may experience mild irritation, itching or discomfort. These lenses should not be prescribed if patients have any eye infection or experience eye discomfort, excessive tearing, vision changes, redness, other eye problems or if patients have any allergy to any ingredient in a solution that is to be used to care for these lenses. Complete information is also available from Johnson & Johnson Vision Care, Inc. by calling 1-877-334-3937 option 4, or by visiting www.seeyourabiliti.com.
Disclosure: Johnson & Johnson Vision, Inc. does not engage in the practice of medicine, and any clinical tips within this presentation are not a substitute for appropriate medical education and training or for the exercise of independent medical judgment. Each medical situation should be considered unique to each patient, and all treatments individualized accordingly based on the respective physician’s medical judgment. Johnson & Johnson Vision, Inc. does not (1) warranty the accuracy or completeness of any of the clinical tips or (2) endorse or recommend any particular technique unless and to the extent such technique is expressly stated in the product labeling.
This promotional education activity is brought to you by Johnson & Johnson Vision, Inc. and is not certified for continuing medical education. Dr. Brauer is presenting on behalf of Johnson & Johnson Vision, Inc. and must present information in accordance with approved product claims.
2024PP06947
