Near Work, Myopia and Astigmatism
In addition to choosing the appropriate (if
any) myopic correction for near work, the
eyecare professional should also ensure that he/she
prescribes for any amount of astigmatism that
the eyes may have when they are focused at near.
As this amount can be different from the amount
of astigmatism that the eyes have when focused at
distant objects, the practitioner should ideally
perform a separate test for the astigmatism while
the patient focuses at a near object.
The main reason for the change in astigmatism at near is related
to the presence of a separately innervated focusing mechanism for
the optical defect of astigmatism. This mechanism is often referred
to as meridional or astigmatic accommodation. Although
the presence of this separate control for astigmatism has been disputed
in the past, I have presented the necessary evidence at an international
optometic conference in 1997 in support of the presence of meridional
accommodation. A good understanding of the mechanism will enable
the eye care practitioner to prescribe proactively. That is, he/she
can then more confidently predict the way that the visual system
reacts to any visual correction, thus enabling the practitioner
to chose a prescription that will help the patient have better eyesight
in the long term. You may wish to refer any health professional
who is interested in reading this scientific paper to the "Eyecare
Professionals" division of this website or directly link to
Meridional (Astigmatic) Accommodation.
Wearing the appropriate amount of
astigmatic correction is important for
several reasons. If the prescription for
astigmatism is not optimal, this can lead to fatigue
or eye ache, especially when there is concurrent
long-sightedness of the eyes as well. Also, the
vision at near can become blurred due to
fatigue of the neuro-muscular system that is
involved in controlling the eye's astigmatism (i.e.
Meridional Accommodation system). To overcome
this slightly blurred vision, one often leans
forwards to see small print better from a closer
distance. This may happen without the
individual being conscious of it, and is
associated with some adverse effects. Firstly the
individual has to focus harder because of the
closer distances involved, leading to more rapid
fatigue and/or the development of myopia (short-sightedness).
Another adverse effect of leaning closer towards
small print on a VDU etc., is increased neck
tension, which in the long term may cause
more permanent neck problems and headaches.
An ideal yet simple way of keeping a good
distance from books or other printed
material is to use a reading stand.
This has several benefits. Firstly it will help
to prevent eye fatigue and myopia.
A reading stand enables printed material to be
presented at right angles to the line of sight
and also enables a greater reading distance. This
helps to prevent excessive focusing of the eyes
and allows the reader to more easily refocus onto
a distant object as he/she is already facing
almost straight ahead. (See Appendix I below for
benefits of regularly refocusing into the
Another benefit of a reading stand is that it
will allow the reader to rest his/her back on the
chair's back support and have the head
comfortably supported in a fairly erect posture.
This will minimise the strain on the spine and
its muscles, and help to prevent neck pain
and related headaches. In cases where the paper
is glossy, a reading stand can also help to minimise
glare caused by overhead lights.