Teacher: Susan Wall
I am one of the three persons in my family that is near-sighted. I always
wondered why I was the first person among my siblings to develop myopia. Then,
we were told that sitting too close to the television would damage our eyes,
however we did not heed to this warning. As I was the only child to express the
trait, the fact that I sat near the television did not seem, to me, to be the
sole cause of my imperfect vision. I know now, that myopia is a complex trait
and its development is influenced by the interaction of multiple genes and
multiple environmental factors (Myopia, 2005).
The eye growth is induced by signals which originate from the retina. Hence
neurotransmission in the retina is required to control eye growth. Recently,
twenty-four new loci were found to contain genes which play vital roles in
neurotransmission in the retina. An important gene is GJD2 which connects
neuronal cells in the retina, aiding the transfer of molecules and ions. The
mechanisms through which these genes stimulate eye growth are not fully
understood, but it is known that the more risk alleles an individual possesses,
the greater the tendency to develop myopia (Genome wide meta-analyses, 2013).
An environmental factor that affects myopia is the amount
of time spent outside. Natural light provides between 28,000
to 130,000 lux of light, while light intensity in a house is
said to be less than 1,000 lux. Bright, natural light from
the sun activates the release of a neurotransmitter in the
retina, dopamine, which reduces undesirable growth in the
eye, hence limiting the elongation of the eye (Morgan, G.