PRODUCT PROFILE
Moving boundaries in myopia control Myopia is a significant global public health and socioeconomic problem and has been steadily increasing in recent decades, writes Andy Sanders It is estimated that by 2050, around 50 per cent of the world’s population will be myopic1. With increased myopia, the risk of sight-threatening conditions increases almost exponentially – with even lower levels of myopia being of concern. Research suggests that ocular diseases potentially leading to sight impairment or blindness is doubled with a refractive error as low as -2.00D (Table 1)2. Historically, practitioners have focused on correcting myopia with standard spectacles or contact lenses that correct the refractive state of the eye, but don’t manage the progression of myopia which typically increases from around six years of age to adulthood. Large segment bifocals have been prescribed with some success in cases where children are esophoric at near. Additionally, short corridor progressives and more recently low add boost lenses have been utilised,
Figure 2: MiYOSMART lenses have a honeycomb-like structure
which are clearly cosmetically more appealing but appear to have relatively low efficacy3. There are several theories as to the aetiology of myopia, however, the mechanisms involved in the onset and progression remain unclear. These proposed theories include mechanical tension, accommodation lag and peripheral refraction or relative peripheral hypermetropic defocus theory (RPHD). Each of these theories may not be exclusive of each other and, in addition, there are complex physiological and biological processes involved which are affected by environmental and genetic factors3.
CLINICALLY-PROVEN TREATMENT The novel MiYOSMART spectacle lens is a collaborative development between the prestigious Hong Kong Polytechnic University and Hoya Vision Care (Figure 1). This innovative, non-invasive spectacle lens design features Defocus Incorporated Multi Segment (DIMS) Technology and has been clinically proven, via a two-year randomised controlled trial with a one-year follow-up, to be safe and effective in the management of myopia; on average reducing myopia progression by 60 per cent4. The MiYOSMART spectacle lens features a clear central hexagonal area measuring 9.4mm in diameter, giving the patient the prescribed myopic correction. This is surrounded by a treatment zone of 33mm consisting of micro-lenslets, each with
-1.00 to -3.00D
-3.25 to -5.00D
-5.25 to -7.00D
Over -7.00D
Myopic maculopathy
2x
10 x
41 x
127 x
Retinal detachment
3x
9x
22 x
44 x
PSC cataract
2x
3x
6x
Data not available
Glaucoma
2x
3x
3x
Data not available
Table 1: Estimated odds ratio of ocular diseases as a function of myopia2
20 Vision Now October 2021
Figure 1: A novel, non-invasive spectacle lens design
3.50D defocus power measuring 1.03mm in diameter distributed exactly 1.5mm centre to centre. Unlike standard spectacle lenses, which produce peripheral hypermetropic defocus, which is hypothesised to drive eye growth myopia progression5, the MiYOSMART spectacle lens creates peripheral myopic defocus reducing the progression trigger. The honeycomb type structure of the defocus zone (Figure 2) gives an average ratio of myopic correction to defocus of 50:50, so when the patient looks directly through the defocus zone, visual acuity remains almost unchanged4. It should be noted that the lenslets, whilst having a power of 3.50D, do not represent or perform like a bifocal addition. This description might well conjure up images of a compound eye type appearance but in Hoya’s view, nothing could be further from the truth. The technological beauty of this lens remains invisible – only becoming apparent when the lens is moved around as if trying to find progressive lens markings. This is partly because the lenslets have a peak of less than 0.8 microns and the lenses come as standard with a special easy clean anti-reflection coating.
PRESCRIBING TOOLS AND SUPPORT Being made of polycarbonate the lens is impact resistant and safe for the rough and tumble of daily life children may experience, additionally providing UV protection. Prescribing the lenses is straightforward and they are measured in the same way as progressive lenses. First, an appropriate frame needs to be selected that has a B size of more than 25mm allowing at least 12mm above pupil centre.
