Eye Care Blog

It is known that because of inheritance not everyone will have eyes of the same size and optical power, that some eyes will fail to achieve ‘normal’ functional standards. Thus at least 15 per cent of us will have developed some degree of short-sightedness by the age of twenty-five, owing to the eye not growing in balance with the rest of the optical system seen as a whole. But this statistic applies only to post-industrial populations. The incidence of short-sightedness is much less among preindustrial peoples, and so it cannot be hereditary factors alone that are at work. The correlation is between short-sightedness and socio-industrial development, not necessarily between short-sightedness and race. There are as many short-sighted Japanese as there are short-sighted Europeans. It could be argued that where pre-industrial conditions still exist the mechanics of natural selection have ‘weeded out’ congenital short sight, but it seems much more likely that a tendency-towardsshort-sight-given-certain-conditions is inherited, and inheritable, among all peoples.

In tribal societies a child’s education involves learning just as much as it does in post-industrial societies. What differs is the technique of knowledge acquisition. While there are no exact figures as to the number of separate bits of knowledge a member of a tribe must learn, it must nevertheless be considerable and compare with what a ‘civilized’ child must learn. But this is done by word of mouth and by example, not through books. It is also most usually, in terms of a teacher—student ratio, a one-to- one process. Children learn from their parents or tribal elders all they need to know about survival, and they are told, either directly or through ritual, about their culture. The ‘civilized’ child must complete a very different course. Oral and performative instruction still occurs, and perhaps to a much greater degree than some modern pedagogues are ready to admit, but the emphasis is on book-learning, both as regards developing survival skills, and as regards culturization. The cultural background studies require proof of acquisition of knowledge by memorizing reading matter. Thus from an early age children of our times will probably find themselves reading print, and progressively smaller print, for several hours a day. This accommodation to close vision, together with sustained convergence of the eyes, will, in some instances, not relax sufficiently when the reading period is over. The power of the eyes remains set for close vision, and if this continues as an habituation the child will develop near sight. This is slightly simplified, but essentially it is what may happen. Also to be taken into account is the effect near-focusing has on the internal system of eye pressures, and the effect those pressures in turn have on the length of the eye. Children who read too much, or read in circumstances where they have constantly to ’strain’ the eyes, are likely to increase the physical length of the eye artificially, and, this is the main cause of short sight. But it does not happen to alt children who thus use, or overuse their eyes, and so such ‘acquired’ short sight needs to be seen as the result of an interaction between genetic composition (tendency) and environment.

Cause and effect are simple in theory. But explanations become more complicated as we increase the number of factors that are taken into consideration. Primitive society is less well equipped to detect small degrees of short-sightedness, and this in itself may be one reason why there are more people with short sight in post-industrial communities. There may even be a problem of language involved. It is possible, for example, that in some bygone societies the difference between being a ‘good hunter’ and being an average or even bad one may have been a difference, inter alia, in visual performance without actually being referred to as such. Again, it may be that certain children have an innate desire for the acquisition of knowledge, or at least looking at small objects, while other children may be naturally more extrovert. The questions arise: are personality traits inherited? and, are there more important considerations than short-sightedness? Some people will only become short-sighted if the pattern of close work is present, while others (a small minority) will become short sighted whatever the circumstances. (Acquired short-sightedness cannot of course be passed on, but a hereditary tendency to become short-sighted is eminently likely.) Yet the acquisition of knowledge from books is related to intelligence. No two children, given the same set of materials to read, are likely to ‘learn’ identically. (But there again, by the time a child is able to read, he or she has already been sufficiently socially conditioned to make it very hard indeed to judge how much intelligence is innate, and how much has been developed through environmental influence.) Furthermore, among social groups more given to reading than others (teachers for instance) interbreeding is likely, again making it difficult to distinguish between genetic factors and environmental influence.

Possibly related posts: (automatically generated)
Short-sightedness and the Environment part 1

• Short-sightedness and the Environment part 3
• Your Eyes and their Care, the Media of the Eye, and Glaucoma part 2
• Short-sightedness and the Environment part 2
• Uncomfortable Eye, Computers and Eyestrain
• Eyeglasses / Spectacle Wearers, Eye Make-up Tips
• Eye Sight, Short- and Long-Sightedness
• Eye-Strain, might need Vision Test
• Eye Sight, Short- and Long-Sightedness continued
• The Appearance of Contact Lenses part 1
• Exercising Eye Visual Memory and Vivid Imagination