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There are
times when we are so absorbed in a good book that we do not notice that
the light has faded. Or we read books while travelling in a dimly lit
bus or train. With the availability of tablets and e-readers, many
people now have the habit of reading at bedtime with the lights off.
When we were kids, most of us have sneaked a torch inside the bed covers
to read an interesting book. We have been told by our parents that
reading in dim light will affect our vision and make us get spectacles.
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Is good lighting while reading very crucial? Can reading in insufficient
light cause any long-term adverse impact on our vision? Read on to know
the answer.
Dark Adaptation: Compensatory mechanism of the eye in the dark
Our eyes have two types of photoreceptors (light sensors) in the retina,
called as cones and rods. Cones are responsible for vision in higher
levels of light (photopic vision) and colour vision. Rods are
responsible for vision in low light levels (scotopic vision).
When we move from a well-lit area to a dark area, or when the light
around us reduces suddenly, certain changes occur in our eyes that help
us adjust to this new light setting:
The sensors in the retina both the rods and cones start producing more
light-sensitive chemicals. The cones make this sensitivity adjustment
over a short period, while rods increase their sensitivity over an
extended time range.
The iris muscle relaxes to make the central opening (pupil) larger to
allow more light to enter the eye.
Reading in dim light can cause eye strain
When you read, the eye has to focus an image of the words onto the
retina. When you are looking at a nearby object, the muscles that
control the shape of the lens (known as ciliary muscle) contracts and
makes the lens bulge and become rounder (increasing the focusing power).
When the light is low, focusing becomes a difficult task as the contrast
between the printed words and the paper is not that great, and this
decreases the eye’s ability to distinguish visual detail. The eyes have
to work harder to distinguish the words from the page, which can strain
the eye muscles.
When there is eye strain for a prolonged duration, the eye muscles
become tired. This strain can cause some symptoms like pain in the eyes,
headache, back pain, neck pain and blurring of vision. You can also
experience dryness of eyes as you tend to blink less often when you
focus intently on an object. These symptoms of strain last for a short
duration and eventually go away.
Dim-light damaging vision is not proven
There are no research studies that have studied the long-term effects of
reading in dim light. However, the consensus of a majority of
ophthalmology specialists is that reading in dim light does not damage
the eyes. It causes discomfort which is completely harmless and goes
away with rest. If the symptoms persist once you stop straining your
eyes, then consult an eye doctor. You may have an underlying refractive
error, which might be the cause of the persistent symptoms.
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Follow these simple tips while reading in dim
light to reduce the strain on the eyes:
Adjust the available light such that it falls directly on the book or
e-reader screen without causing a glare.
Blink often while reading.
Focus on something at a distance or across the room every 15- 20
minutes.
Take brief breaks every hour or so when reading for a long duration. |