I
have a cat that is a year old and for the last few
months I've noticed his pupils don't respond to
light that well. His pupils are very large at night
and barely shrink when he's in light. When I shine
light into he squints like it hurts his eyes and his
pupils shrink only a little bit. I have another
older cat and his pupils are no where near that big
even in the darkest rooms. I know there pupils get
much larger at night but even in the sunlight they
are medium sized . Could this be PRA? (Missy Tomas,
Ontario)
You
have obviously done your research and suggested with
good cause that this might be Progressive Retinal
Atrophy (PRA). The indications are strong that your
cat maybe be beginning to suffer from this largely
hereditary disease. When a cat suffers from PRA, the
eye develops normally as a kitten but throughout
adulthood the photorececeptors will degenerate,
leading to total blindness at the age of 3 to 5
years. The outward appearance of the eye will
usually be normal, although pupils will be
noticeably more dilated (as you mention with your
cat) and will reflect more light from the interior.
Only in rare cases does the eye lens become opaque
or cloudy. One of the first problems a cat will
experience is night blindness.
You should take your cat to the vet, who can
refer you to a veterinary opthalmologist for a
decisive diagnosis. Unfortunately there is neither
any way to slow the progression of this disease or
to cure it. However, the outlook for blind cats is
reasonably good, with cats being highly adaptive due
to their reliance on hearing and smell. See the
article below for more information.
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only and is not meant to replace an appointment with a registered
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are only able to answer several questions per week so not everyone gets a
published answer. And, unfortunately we can't answer by email.
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I
have a cat that is a year old and for the last few
months I've noticed his pupils don't respond to
light that well. His pupils are very large at night
and barely shrink when he's in light. When I shine
light into he squints like it hurts his eyes and his
pupils shrink only a little bit. I have another
older cat and his pupils are no where near that big
even in the darkest rooms. I know there pupils get
much larger at night but even in the sunlight they
are medium sized . Could this be PRA? (Missy Tomas,
Ontario)
You
have obviously done your research and suggested with
good cause that this might be Progressive Retinal
Atrophy (PRA). The indications are strong that your
cat maybe be beginning to suffer from this largely
hereditary disease. When a cat suffers from PRA, the
eye develops normally as a kitten but throughout
adulthood the photorececeptors will degenerate,
leading to total blindness at the age of 3 to 5
years. The outward appearance of the eye will
usually be normal, although pupils will be
noticeably more dilated (as you mention with your
cat) and will reflect more light from the interior.
Only in rare cases does the eye lens become opaque
or cloudy. One of the first problems a cat will
experience is night blindness. 
