Figure 5: Typical SPD recommended for 1.00pm-4.00pm/350 Lux @ desk height
Discussion
Growth of the human eye is a perfectly normal event from the age of two years (rapid eye growth) to nine (slow eye growth). By the age of nine years, the human eye should have reached emmetropia and normalization of axial length. Under normal day/night exposure and provided with adequate sunlight rich in indigo-blue wavelengths of ~480nm for at least a part of the solar day, the eyes will naturally maintain a state of emmetropia or ‘no visual error’; that is no optical correction will be necessary to render an in-focus retinal image.
It is a complex process and quite remarkable given that that there is wide variation in the optical properties, particularly focal lengths, of the cornea and crystalline lens that require precise adjustment of eye-length to achieve a clear retinal image.
In the hands of the author, the prescribing of multi-focal spectacles and historically before that, bifocal spectacles, helped to slow the progression of myopia in the eyes of younger patients most often followed for the period of their schooling and sometimes beyond. These approaches have some merit however they are an attempt to remedy the problem post-onset. These interventions are also costly and in the case of atropine eye drops, not without side -effects.
The prior research of Read and Hua, following on from Rose and Morgan, revealed that once an adequate dose of light was provided myopia was lessened in both progression (Read) and incidence (Hua). The work of Hua was outstanding as it showed that simply increasing room illumination offered a remedy in the context of prior research targeting the beneficial effects of sunlight. Consider also that Hua deployed fluorescent lights which caused a positive outcome.