Development of Ocular Refraction:
Lessons from Animal Experiments
Frank Schaeffel, Howard C. Howland
From:
PEDIATRIC OPHTHALMOLOGY, NEURO-OPHTHALMOLOGY, GENETICS
Essentials in Ophthalmology, 2006
A discussion of research on myopia. Two strategies to control myopia development are also noted: one, reducing "critical visual experience" (discussed in this paper), and using more "individually adapted" glasses, and two, using atropine to inhibit axial eye growth (though more research is needed for long term use).
From the text:
"In summary, these studies demonstrate
convincingly that refractive development
is also controlled by visual experience in
humans (not a trivial statement, after all).
They further show that the treatment with
reading glasses is worthwhile, at least in a
subgroup of children."
"That reading at poor illumination increases
the risk of myopia development is only
suggested by experiments in chickens.
Despite the lack of other evidence, it is still
advisable to use appropriate illumination.
Reading distance is a critical factor and
reading should occur at sensible distances
(i.e., 30 cm). There is no evidence that computer
work is more myopigenic than reading
a book at the same distance, but the
computer is more attractive, increasing
the “dose” of near work."
"If the observations in animal models (see
Sect. 1.2.4) are applicable to human myopia,
interruption of reading for only short periods,
and looking at a distance, should effectively
inhibit the growth signal for the eye.
More research is necessary in the monkey
model and in children to find out whether
temporary wearing of positive lenses could
further strengthen this inhibitory signal for
axial eye growth."
"The older the eye, the less important the
input of visual experience is. The most
sensitive period is the phase with the fastest
growth.However,myopia can still be
induced in adult animals and humans."
From the text:
"Core messages:
* There is overwhelming evidence in both
animal models and humans that refractive
development and axial eye growth are
under visual control
* The retina can analyze the sign and amount
of defocus over time and control the
growth of the underlying sclera
* Myopia is generally increasing in the
industrialized world, in particular in the
Far East
* Although genetic factors modulate the
predisposition to become myopic, the high
incidence of myopia in the industrialized
world is likely to be due to environmental
factors
* There are two major strategies to interfere
with myopia development: (1) reducing
“critical visual experience” (which is about
to be defined).More individually adapted
spectacle corrections may be a way since
they can reduce progression of myopia by
up to 50% in selected children. (2) inhibiting
axial eye growth pharmacologically.
Atropine is effective, but the mechanism
of its action is not understood and its side
effects preclude prolonged application."
http://www.uak.medizin.uni-tuebingen.de/frank/pdf/01_Lorenz_Schaeffel.pdf
