Myopia represents the most common cause of vision impairment worldwide, and many attempts have been made with spectacles, rigid lenses, therapeutics and other techniques to control its progression in children and young adults. The surge in prevalence seems to be associated with increasing educational pressures, combined with life-style changes, which have reduced the time that children spend outdoors.
In spite of a long history of study, as well as a noteworthy increase in research attention, the means of preventing the progression of myopia are still elusive. Environmental factors can influence the prevalence of myopia, which has been shown with intensive visual near work (such as reading, writing and close work at the computer).
Hence visual hygiene measures are often recommended, which include taking a break every 30 minutes when doing intensive near work, maintaining proper distance from the book while reading, keeping sufficient illumination, doing visual work using a relaxed upright posture and placing a limit on the time spent watching the television.
Outdoor activities as a preventive measure
Recent epidemiological research points to the fact that children who spend more time outdoors are less prone to the development of myopia – regardless of eventual genetic burden or how much near work they do. At the moment it is still uncertain if time outdoors can also halt the progression of the condition.
The suggested mechanism of the protective effect of outdoor activities involves light-stimulated release of the neurotransmitter dopamine from the retina, since increased dopamine levels appear to inhibit further axial elongation, which is the pathophysiological basis of myopia.
Experiments on animals have supported this hypothesis, since protective effects of bright light against the development of myopia have been replicated under laboratory conditions. Furthermore, it has been proven that the effect is (at least partially) mediated by dopamine, considering that the D2-dopamine antagonist spiperone reduces this protective effect.
Although certain inconsistencies are noted in the evidence, particularly limited inhibition by bright light of lens-induced myopia in laboratory monkeys, other mechanisms can also contribute when spending time outdoors; some of them are increased physical activity, relaxed accommodation, increased pupil constriction, more uniform dioptric space, exposure to ultraviolet light and changes in the spectral composition of visible light.
Clinical trials are now underway hoping to halt or reduce the development of myopia in children by increasing the amount of time they spend outside. More precise definition of thresholds for protection in terms of duration and intensity of light exposures are needed. Epidemiological studies are undoubtedly helpful, but questionnaires should be replaced with more precise measurement of exposures.
Controversial Bates eye method is an alternative therapy that can supposedly prevent and cure myopia and other refractive diseases of the eye with the use of specific exercises. The method is based on the work and theories of William Horatio Bates, who was a medical doctor and eye specialist practicing in the late 19th and early 20th centuries.
Bates claims that physiological characteristics of the eye are not responsible for the development of myopia, but the condition rather arises as a result of a combination of strain and incorrect habits of visual information processing. Hence central fixation, palming, visualization, swinging, shifting and sunning should significantly aid in the prevention of this condition.
Nevertheless, the principles behind the Bates technique vary greatly from conventional understanding of myopia. In addition, anecdotal reports of vision preservation and improvement have not been evaluated in trials. There is no clear scientific data published in the mainstream literature supporting the use of eye exercises to improve visual acuity, thus their use therefore remains controversial.
It is important to note that there is no scientific evidence that any of the commercial devices for myopia treatment can truly prevent and reduce myopia, or retard its progression. Adequate scientific studies are therefore necessary for any treatment modality or product prior to making unsubstantiated claims of myopia prevention.