As eye care professionals we can make a real difference to the lives of our young myopic patients.
AG first presented to the practice aged seven. She had been diagnosed with myopic astigmatism at five, and had progressed by approximately one dioptre a year. Her father is a moderate myope, her mother emmetropic, but her paternal uncle suffers from high myopia (-12.00), and his two children – her cousins, also suffer from high myopia (> -10.00). AG struggled with her spectacles, and complained about becoming tired after prolonged reading.
At first presentation, AG’s spectacles were of prescription R -5.25/-2.75×177, L -5.00/-2.25×178. These spectacles were six months old.
Cycloplegic refraction: R -6.00/-2.75×178 (6/7.5=), L -5.50/-2.50×2 (6/7.5=).
Aside from its potential for controlling myopia, orthoK has been shown to be a safe, effective method for reducing refractive error…
Binocular vision testing was normal. Near phoria was 1 exo, and a lag of accommodation of +0.50DS was found.
AG’s ocular health was unremarkable.
Videokeratoscopy with the Medmont E300 revealed moderate with-the-rule cylinder in both eyes (Figure 1).
Understandably, AG’s parents were very concerned by the increase in her myopia, and were keen to delay any more progression. After lengthy discussion, she was prescribed custom, toric, reverse-geometry orthokeratology (orthoK) lenses.
Two years later, AG continues to wear these lenses on a nightly basis. During this time, she has had a modification to increase the target correction for her right contact lens by -0.50DS, but none for the left. Videokeratoscopy reveals well centred, albeit small central treatment zones (Figure 2).
Axial-length measurements with A-scan ultra-sound biometry measurements were as follows:
At presentation: R 24.13mm, L 24.08mm
After 12 months: R 24.35mm, L 24.07mm
After 24 months R 24.34mm, L 24.10mm.
Myopia is a growing problem throughout the world, with uncorrected myopia being the second most common cause of blindness globally. Presently, it is estimated that 22.9 per cent of the world suffer from myopia, with 2.7 per cent suffering from high myopia.1 Myopia rates are expected to continue to rise, and it is predicted that by 2050, 50 per cent of the world will suffer from myopia, and alarmingly, approximately 10 per cent will suffer from high myopia.1
Myopia is not just the need for spectacles, and high myopia is not simply thicker lenses. With myopia, there is an increased risk of pathology such as cataract, glaucoma, retinal detachment and myopic macular degeneration, with risks increasing with higher degrees of myopia.2
Consequently, myopia and how to control it has recently been a hot topic. Current methods that have been shown to be effective for myopia control include orthoK, multifocal soft contact lenses (MFSCL), atropine and progressive or bifocal spectacles.3
Myopia commonly develops around the ages of eight to 10 years, and progresses through the teenage years.4 The greatest risk for high degrees of myopia is younger age of onset of myopia and faster rates of myopic progression.5
A recent meta-analysis of studies measuring axial-length elongation with orthoK has shown a reduction in myopic progression by 45 per cent.6 MFSCLs with a centre-distance design have been shown to provide a 29 per cent reduction in myopia progression.7
It has been shown that single vision correction – whether it be spectacles, soft contact lenses or rigid contact lenses – does not affect the rate of myopia progression,8,9,10 and that under-correcting myopia actually increases the rate of myopic progression in children and teenagers.10
Bifocal and progressive spectacles have been shown to be effective at reducing myopia progression by 38 per cent in patients with a significant lag of accommodation or esophoria at near.11 We would not expect these to be effective for AG, given her normal binocular vision status.
Atropine is the most effective known treatment for reducing myopia progression,3 however as atropine causes mydriasis and cycloplegia, it has been less accepted by patients and practitioners. Furthermore, there has been reported ‘rebound’ i.e. a rapid increase in myopia progression following cessation of treatment. Recently, lower doses have been shown to be as effective at reducing myopic progression. Atropine 0.01 per cent has been shown to reduce myopia progression by 64 per cent, yet does not lead to clinically significant mydriasis and loss in accommodation, and does not lead to rebound following treatment cessation.12
AG is not a simple case: the young age of onset, the already high degree of myopia, the documented rapid progression, and the strong family history of myopia, make her a high risk case for continued myopic progression.
The efficacy, safety profile and difficulties with each mode of myopia control were discussed.
MFSCLs could be an option for AG as soft contact lenses afford good initial comfort, however these are less effective than orthoK for myopia control. Presently, only one contact lens manufacturer produces a disposable, centre-distance MFSCL, and the toric lens is only available in a monthly made-to order hydrogel material. Ideally, we would prefer AG to be wearing a lens which is more oxygen permeable, especially given her young age and potential to be wearing contact lenses for many more years. Her parents were also concerned about sending her to school with contact lenses because they would not be there to assist if issues with the lenses were to arise.
Even with its known greater rate of efficacy for myopia control, AG’s parents were hesitant to use a therapeutic agent in their child daily, despite the lesser profile of side effects with the low dose atropine. However, if we could not adequately delay AG’s myopic progression, we would reconsider using pharmacological agents in the future.
AG and her parents decided to proceed with orthoK. Aside from its potential for controlling myopia, orthoK has been shown to be a safe, effective method for reducing refractive error, allowing wearers to be spectacle-free.
AG’s refractive error presents a challenge for orthoK, because until recent years, high degrees of myopia and astigmatism were not adequately treatable with orthoK. Fortunately, with better understanding of corneal-reshaping, improved technology for measuring corneal shape and improved lathing of speciality contact lenses, the degree of prescriptions treatable with orthoK has increased.
In all honesty, I was initially hesitant to proceed, given AG’s high degree of myopia and astigmatism. However she and her parents were highly motivated and willing to accept top-up spectacles for correction of any residual myopia. This would be a reasonable option as it has been found that even partially correcting high myopia can lead to a significant reduction in myopic progression.13
Fortunately, AG manages exceptionally well with orthoK. While her unaided vision is slightly reduced compared to best corrected spectacle acuities pre-treatment, she reports more comfortable vision being spectacle-free, especially without the aberrations induced by spectacles of a high prescription. The main benefit is that we have been able to dramatically reduce her myopia progression, which is shown by the few changes to her contact lenses and her A-scan measurements.
Although there is a seemingly inevitable increase in the prevalence of myopia and high myopia, our understanding of myopia, its causative and risk factors, is continuing to expand, as are the resources available to help tackle the condition. We as eye care practitioners are at the forefront of treating myopia, and fortunately there are many, more appropriate options than to simply give a child a pair of spectacles.
Jessica Chi is the director of Eyetech Optometrists, an independent specialty contact lens practice in Melbourne. She is the current Victorian and past National President of the Cornea and Contact Lens Society, and an invited speaker at meetings throughout Australia and beyond. She is a clinical supervisor at the University of Melbourne, and has served on the continuing education committee for the Australian College of Optometry and the Therapeutics Advisory Board for the Optometry Australia