With increasing clinical and research activity in myopia control comes the important push for practitioners to get started in myopia management. If you are getting started, though, what equipment do you need? What are the essentials?
As discussed in the International Myopia Institute (IMI) Clinical Management Guidelines Report,1 there are some key pieces of equipment to have on board, and some others that are not crucial but helpful to have.
Measuring acuity and refraction
Our key role in primary eye care is to measure and correct vision. Don't forget, however, that in myopia we're not just looking for a minus refraction. Hyperopia which is too low for a child's age can indicate pre-myopia. The biggest risk factor for future myopia is being +0.50 or less at age 6-7 years, and can indicate the initial phase of progression into myopia.2 Read more about this in our blog How to identify and manage pre-myopes.
A key aspect of the refraction is managing accommodation in children. This may be especially critical in younger children or those with apparent large changes in their refraction. Show caution when using autorefractors for the same reason.
The IMI Clinical Management Guidelines Report does not necessitate cycloplegia for all myopic refractions in a clinical setting, but explains it is an important tool to use 'as indicated'. 'As indicated' allows for the fact that cycloplegia may not be available or suitable for that child, or may not be needed if 'ocular accommodation is relaxed', as per the IMI Defining and Classifying Myopia Report.3
For more information on measuring acuity and refraction, techniques and cycloplegia, read our blog How to achieve accurate refractions for children. A helpful tip? Retinoscopy is best. It is the best screening tool for detection of refractive error in children and is recommended by numerous professional organizations. Non-cycloplegic retinoscopy using contralateral eye fogging has also been found to be within 0.30D accuracy of cycloplegic retinoscopy.4
Equipment you need: a child-suitable acuity chart and a retinoscope.
Binocular Vision Assessment
The IMI Clinical Management Guidelines Report,1 describes accommodation and vergence testing as an important component of the myopia picture. For more information on the link between myopia and binocular vision function, read our blog Four Reasons Why Binocular Vision Matters in Myopia Management. Recently published, the IMI Accommodation and Binocular Vision in Myopia Development and Progression Report provides a scientific exploration for the relationships between accommodation (specifically accommodative lag), retinal blur, closer working distance and potential mechanisms of myopia development and progression.
On the clinical front, while there is no agreed or 'gold standard' methodology for assessing binocular vision, the IMI Clinical Management Guidelines Report1 includes two tables which describe the various accommodative function and vergence function tests used in clinical studies. Rarely would a clinical study include each one of these tests - the recommendation was that tests of both systems be employed at baseline and the same tests at follow-up consultations.
Accommodative function:
- Accommodative accuracy (lag or lead) - open field autorefractors, retinoscopy techniques, photorefractors and non-clinical methods such as aberrometers.
- Accommodative amplitude - minus lens technique or push up test
- Accommodative facility - measured with plus / minus flippers.
Vergence function:
- Distance and near heterophorias - Risley prism and Maddox rod, Von Graefe method, alternating cover test, Howell near phoria card, Saladin near point balance card
- Near fixation disparity - Saladin near point balance card
- AC/A ratio - Calculated method and gradient technique.
If you're not feeling confident about binocular vision measurement, you can learn a lot more from the Expand my clinical skills portal on this website. There are also freely available videos on accommodation and vergence measurement techniques, and a one-hour lecture entitled 'Binocular Vision - easier than you think' on the Myopia Profile YouTube channel.
To take the next steps, our Binocular Vision Fundamentals online course simplifies how to assess, diagnose and manage BV disorders with easy to follow video instructions, demonstrations and downloadable reference infographics. The first hour of this comprehensive six hour course can be trialled for free.
Equipment you need: methods for measurement of accommodation and vergence. A retinoscope, plus/minus flippers and a prism bar will cover most aspects of binocular vision assessment.
Corneal Topography
Topography is essential for safe and accurate orthokeratology fitting.5 Regarding patients in other corrections or treatments, the IMI Clinical Management Guidelines1 recommend corneal topography "if indicated (for example, for contact lens fitting)".
A noteworthy aspect of childhood myopia is that while myopia progression in children is typical, astigmatism progression is not. Multiple large studies in various ethnicities6-8 have indicated that astigmatism increases alongside myopia increases are rare. In children aged 6-12 years, progression of 0.50DC or more over three years is unusual. If you observe this, measurement of keratometry and/or corneal topography is useful to rule out corneal ectasia.
Of course, an irregular corneal reflex on Retinoscopy also necessitates further examination of the cornea - retinoscopy has high sensitivity for detection of even early stages of keratoconus.9
Equipment you need: a way to measure corneal curvature and shape where indicated - for orthokeratology and/or contact lens fitting, in cases of progressive astigmatism or where an irregular retinoscopy reflex is noted. If access to this equipment is limited for you, consider referral and co-management pathways with primary eye care colleagues and/or ophthalmologists.
Axial length measurement
Axial length measurement is a crucial element of myopia control research studies, and interferometry measurement techniques can be 10 times more accurate than refraction for detecting myopia progression.10
Clinically, axial length measurement is not yet widely employed in primary eye care, with newer instrumentation and research outcomes guiding the way for this to likely become a standard of care.
The IMI Clinical Management Guidelines Report1 states that "at this point, there are no established criteria for normal or accelerated axial elongation in a given individual." Axial length measurement is recommended "Where available, [and] measurement with a noncontact device is ideal."
As an absolute measure, axial length appears to be the key indicator for the lifelong eye health risks brought by higher levels of myopia. An axial length greater than 26mm is a key threshold for risk,11 so a single measure of a child's axial length (even if it's not possible to be repeated regularly) can give an indication of risk and hence how proactive a myopia management strategy should be.
As a relative measure, from exam-to-exam, how much does axial length typically change? Axial length increases normally throughout childhood emmetropization. Again from the IMI: "Increases of about 0.1 mm/yr have been shown to be associated with normal eye growth, whereas 0.2 to 0.3 mm/yr is associated with increasing myopia, although myopia progression can occur with smaller AL changes in an individual."1
Judgement of axial length measures in future will likely involve comparison of the measure against validated percentile growth charts - examples for Chinese and Dutch children have been published. This would mean taking a child’s axial length measurement, comparing it against a chart specific to their age, ethnicity and gender, and determining what percentile of eye length they currently represent. The 50th percentile represents the mean, and early research on this is indicating that children in the 75th percentile or higher are at greatest risk of future high myopia.12 Over time, if a child’s percentile decreases with time, this would indicate a successful myopia management strategy. Read more about this latest science in A tale of two studies measuring change to axial length in myopia.
Equipment you need: ideally, a way to access axial length measurement for your myopic patients, and non-contact (interferometry) methods are most accurate. Consider co-management with suitably equipped colleagues and/or ophthalmologists to gain measurements, even if only annually, as this extra data can indicate long-term eye health risk and influence management.
Retinal examination and imaging
The IMI Clinical Management Guidelines Report1 recommends "examination of the central and peripheral retina [through dilated pupils], annually in high myopes and in others as indicated. If retinal findings are noted, optical coherence tomography (OCT) images and/or fundus photos may be taken to objectively document retinal features and/or abnormalities."
Retinal examination competency and equipment access varies in primary eye care by country and practice setting. If access to this technology is typical in your country, it could be considered standard of myopia care. If not, follow your scope of practice guidelines to ensure that the retinal health of your young myopes is reviewed annually for high myopes of any age (5D or more) and as indicated by your professional standards for others. It would be good practice to ensure all myopes have an annual eye health examination, where possible.
Equipment you need: it will depend on your scope and setting of practice. Whether you are undertaking the retinal health examination or referring to ophthalmology, ensure your high myopes have a full retinal health examination annually, and low-to-moderate myopes as indicated by your professional standards.
Don't let equipment be a barrier to getting started
There is more than enough evidence now that doing nothing to control myopia - continuing to fit single vision corrections in progressing childhood myopes - is not the standard of care. While you may not have all of the equipment, clinical competencies or processes to adopt all aspects of myopia testing and management described above, pathways are available when working with colleagues, ophthalmology and within professional standards in your region. Remember that every dioptre matters in controlling myopia, so stay up to date and get started using the tools and guidance available to you.
About Cassandra
Cassandra Haines is a clinical optometrist, researcher and writer with a background in policy and advocacy from Adelaide, Australia. She has a keen interest in children's vision and myopia control.
About Kate
Dr Kate Gifford is a clinical optometrist, researcher, peer educator and professional leader from Brisbane, Australia, and a co-founder of Myopia Profile.
This content is brought to you thanks to an unrestricted educational grant from
References
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- Zadnik K, Sinnott LT, Cotter SA, Jones-Jordan LA, Kleinstein RN, Manny RE, Twelker JD, Mutti DO; Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study Group. Prediction of Juvenile-Onset Myopia. JAMA Ophthalmol. 2015 Jun;133(6):683-9. (link)
- Flitcroft DI, He M, Jonas JB, Jong M, Naidoo K, Ohno-Matsui K, Rahi J, Resnikoff S, Vitale S, Yannuzzi L. IMI - Defining and Classifying Myopia: A Proposed Set of Standards for Clinical and Epidemiologic Studies. Invest Ophthalmol Vis Sci. 2019 Feb 28;60(3):M20-M30. (link)
- K.(2007) Cycloplegic refraction and non-cycloplegic refraction using contralateral fogging: a comparative study, Journal of Modern Optics, 54:9, 1317-1324 (2007). (link)
- Cho P, Cheung SW, Mountford J, White P. Good clinical practice in orthokeratology. Cont Lens Anterior Eye. 2008 Feb;31(1):17-28. (link)
- O'Donoghue L, Breslin KM, Saunders KJ. The Changing Profile of Astigmatism in Childhood: The NICER Study. Invest Ophthalmol Vis Sci. 2015;56(5):2917-2925. (link)
- Huynh SC, Kifley A, Rose KA, Morgan IG, Mitchell P. Astigmatism in 12-Year-Old Australian Children: Comparisons with a 6-Year-Old Population. Invest Ophthalmol Vis Sci. 2007;48(1):73-82. (link)
- Tong L, Saw S-M, Lin Y, Chia K-S, Koh D, Tan D. Incidence and Progression of Astigmatism in Singaporean Children. Invest Ophthalmol Vis Sci. 2004;45(11):3914-3918. (link)
- Al-Mahrouqi H, Oraba SB, Al-Habsi S, et al. Retinoscopy as a Screening Tool for Keratoconus. Cornea. 2019;38:442-445. (link)
- Wolffsohn JS, Kollbaum PS, Berntsen DA, Atchison DA, Benavente A, Bradley A, Buckhurst H, Collins M, Fujikado T, Hiraoka T, Hirota M, Jones D, Logan NS, Lundström L, Torii H, Read SA, Naidoo K. IMI - Clinical Myopia Control Trials and Instrumentation Report. Invest Ophthalmol Vis Sci. 2019;60(3):M132-M160. (link)
- Tideman JW, Snabel MC, Tedja MS, van Rijn GA, Wong KT, Kuijpers RW, Vingerling JR, Hofman A, Buitendijk GH, Keunen JE, Boon CJ, Geerards AJ, Luyten GP, Verhoeven VJ, Klaver CC. Association of Axial Length With Risk of Uncorrectable Visual Impairment for Europeans With Myopia. JAMA Ophthalmol. 2016;134(12):1355-1363. (link)
- Klaver C, Polling JR; Erasmus Myopia Research Group. Myopia management in the Netherlands. Ophthalmic Physiol Opt. 2020 Mar;40(2):230-240. (link) [Link to Myopia Profile Science Brief]
