Masters of Health Magazine September 2018 - Page 21

Figure 2. Dopamine receptor activity within the retina controls eye growth

Particular laboratory approaches are known to cause myopia in birds and mammals. Form deprivation myopia (FDM) for example, which is shielding the eye of a laboratory animal with an opaque occluder; another is lens-induced-myopia (LIM), which consists of placing a spectacle mounted lens of known power before the tested eye to cause defocus of the retinal image.

These techniques cause reduced retinal dopamine release in the tested eye. However, the intra-vitreal injection of dopamine agonists (e.g. apomorphine) into the tested eye, inhibits both FDM and LIM. If restoring the dopamine signalling pathway with apomorphine counter-acts the dopamine inhibition effect of patching or optical defocus of the retinal image, the case for a dopaminergic pathway being central to eye-growth has effectively been made. The role of dopamine playing a key role in eye-growth has been reviewed extensively in many other publications.

Professor Scott Read from Queensland University of Technology equipped school aged children with light sensitive wrist bands that measured the daily exposure to ambient light (in lux). The results showed that moderate to high light exposure of ~ 800-1450 average lux per day had a positive effect on reducing axial elongation of the eye. Corroborating research by Prof. Hua in 2015 showed increasing the available luminance at desk height of school children aged 8-14 years, from ~100 lux to 500 lux had the effect of reducing the incidence of myopia measured over one year from 10% to 4%.

When considered collectively, this presented as an opportunity for an application for processor control of LED lighting that could provide the necessary wavelengths and luminance over time for required retinal dopamine responses to positively impact on reducing the frequency and progression of myopia.

The spectral-power distribution of a suitable luminaire must be tunable (processor controlled), emit white light and retain a blue peak at 480nm offering maximal opportunity to stimulate ipRGC/amacrine cell release of retinal dopamine in concert with preferably the diurnal cycle of the human experience of sunrise to sunset. Further, the blue peak of 480nm being higher of a morning is preferably reduced over the period of a day's exposure more or less linearly so that by late afternoon there is minimal radiation at the wavelength to which ipRGCs are most sensitive, i.e. 480nm. Whilst the governing parameters in this solution are based on wavelength and luminance over time, it is for convenience reasonable to describe it here in broad terms that this solution would display a higher CCT of a morning (~5000K) and a reduced CCT of an afternoon (~2700K).