What Does an Eye
Examination Involve?
The assistant usually measures the curvature
of the cornea ("window"of the eye) with
an automated machine (auto-keratometer). The
optometrist first tests the patient's vision at
both distance and near. This is usually followed
by a test of muscle balance to detect any
tendency of the eyes to turn. While having the
patient see through 'fogged' lenses, the
optometrist then estimates the refractive state
of the eyes (for distance) using a retinoscope.
Then follows the "subjective refraction"
i.e. the tedious verification of the estimate
obtained above by asking the patient which of two
ways the vision is better.
The focusing power of the eyes
is then measured and the prescription for near
glasses is found. This often involves a further
subjective refraction at the near distance, as we
believe that the astigmatism at near can be different from that measured in
the distance.
A "slit-lamp"
microscope is often used to assess the
conjunctival membrane (on the white of the eye)
and also to assess the cornea and the lens within
the eye. Following this, the pressures in the
eyes are measured by first instilling anaesthetic
drops and then using a tonometer.
Dilating
Drops
In patients over 40 years of age, drops are
used to dilate the pupils of the eyes. The action
of these drops usually lasts for 3-4 hours.
During this time, patients are more sensitive to
daylight and some experience mild blurring of
their vision. For this reason, it would be
preferable if people over forty years could be
accompanied by another person if they are coming
by car. It would be useful to bring along
sunglasses also, to reduce glare in daylight.
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