What can my child see now?
If your child has a total cataract your child may be able to
see just light and dark and maybe some colours. Not all
congenital cataracts are totally opaque (like a sheet of thick
paper rather than like tissue paper), some babies can still see
movement and large shapes. Rarely the cataract affects vision
very little, at least early in life, especially if the cataract
is like a cloud of tiny dots in the lens rather than a white
sheet
If he or she has a partial cataract, what they can see could
vary between seeing everything normally and not being able to
see much detail or much in the distance, or being able to see
less when it's bright. Bright light may be dazzling in
cataracts due to a cloud of tiny dots in the lens as these
scatter the light. This is like trying to see the view through
frosted glass of a bathroom on a sunny day as compared to a
dull day, or to trying to read a street sign when an oncoming
car has their lights on high beam.
‘Cataract’ means that part or all the lens is
cloudy or opaque. In general, if the opaque area is in the
centre of the lens in the pupil, particularly in the posterior
(back) part of the lens this will stop the lens focusing and be
more ‘visually significant’. If the opacities are
towards the front pole of the lens, affects only the edges, or
are less dense, they are likely to block vision and are less
‘visually significant’.
How are a baby's eyes tested?
The ophthalmologist will usually assess your child's vision
using a method appropriate for age and compare the result with
the usual result for this age. If your baby is very young they
may be sleepy at the time you see the doctor. If the doctor
knows from experience and from the type and density of the
cataract that this will seriously impair vision, further
testing of vision behaviour may not be necessary when deciding
whether your baby will need a cataract operation.
Vision is tested qualitatively by watching what a baby looks
at and what they will track (follow with their head and eyes).
A parent's or grandparent's input is often valuable as they
compare with their other children at the same age.
The doctor looks for abnormal flickering or roving eye
movements and notes whether the two eyes move together.
Quantitative tests of vision (with numbers like 6/60) are
much harder to perform in a very young child or if the child
has developmental delay. The tests used are either
‘preferential looking’ tests or
‘electrodiagnostic tests’. Preferential looking
tests rely on a child's interest in patterns from an early age
and a stripy black and white pattern is shown to them on a grey
card with the same brightness as the stripy pattern if it is
blurred. The baby will only look at the pattern if they see the
detail. The tester will know they are seeing by watching their
eyes and varying whether the pattern is on their right or left
and by moving the pattern and seeing if the baby's eyes
follow.
Electrodiagnostic tests are only available in a few
specialist centres and can be helpful if the doctor is not
certain how much a partial cataract is impairing a baby's
vision and if the cataract is becoming denser.
The Ophthalmologist can work out how much the cataracts are
likely to be affecting your child's vision from all this
information. They will when deciding when and whether to
recommend surgery take into account other eye conditions and
other conditions your child may have. They will examine you and
ask about other members of the family who have had early
problems with their eyes. They will then advise whether the
cataract should be removed now, or later, or to wait and see
whether they grow (‘progress’).
Young babies with normal eyesight do not see as clearly as
an adult or an older child so if your newborn, for example,
gets a result that is poorer than 6/60 (they are able to see at
six metres what an adult with normal vision is able to see
at sixty metres), this may be a normal result for their age;
the test results aren't adjusted for age although the type of
test that's done is. Babies' vision usually develops so they
are able to see almost as much detail as an adult (6/6 or
20/20) by around their third birthday. Vision continues to
develop until the child is about eight years old, so if your
child is a late starter learning to see (after cataract surgery
for example) they may not develop their best vision until they
are a lot older than usual.
An older child who has suffered an eye injury that has
caused a cataract has already done their learning to see and
their eye has developed normally so it is much easier for the
older child in this situation to get really good visual results
after the surgery if there aren't any other problems with the
eye. A newborn baby must be able to see a reasonable amount
within the first weeks and months of life or he or she will
never be able to learn to see well, if at all because their
eyes and brain needed the stimulation during that time
window, but there are no hard and fast rules and children's
visual development can vary a lot even in the same situation.
Children also vary a lot in how well they use the vision they
have.
Why won't the ophthalmologist tell me more?
Many Ophthalmologists will not tell you very much about
what your child is likely to be able to see, especially if
you've just been told about the cataract(s). While your child
is very young, they are not able to get clear test results and
his or her vision is still developing.
Many of us need time to get used to the situation before
asking for more information. You may need to explain that you
would rather have another appointment later when you will be
better able to take in information (although this might be
more difficult if you need to make a quick decision about
surgery, it should be possible). Or you might need to explain
that you really want to know as much as possible in order to
know what help your child might need and to get access to the
best help and services as soon as possible. You may need to
accept that there aren't definite, clear-cut answers to every
question.
Checked for medical accuracy by Miss Isabelle
Russell-Eggitt, Consultant Paediatric Ophthalmologist, Great
Ormond Street Hospital, London
Last updated: 28/02/08
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Childhood Cataract Network
