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vision loss in dogs can be due to problems in one of three areas: the
retina, the optic nerve or in the brain.
SARDs - sudden acquired retinal degeneration syndrome
loss may occur over a few days to several weeks.
may occur in dogs of all ages.
dogs may have a history of increased thirst, urination and/or appetite
and may have gained weight. Some dogs with SARDs also have Cushing’s
Disease, a hormonal disease whereby the adrenal produces too much cortisol.
Blood tests with your local veterinarian will help to diagnose this
condition or rule it out.
retina is normal on examination early in the disease, but may show signs
of degeneration months after the vision loss has occurred.
cause of SARDs is unknown and there is no treatment
Cases of SARDs usually have a reduced PLR (pupillary light response).
can be confirmed by ERG (electroretinogram) which is flat showing no
Retinal Inflammation and Retinal Detachments.
examination of the retina, inflammation is seen as subtle to marked
changes in many cases whilst in others the retina appears normal. Retinal
detachments are usually clearly visible.
cause of this condition is unknown, however is suspected to be immune-mediated.
of this condition involves the use of oral cortisone tablets.
50% of cases respond to cortisone.
Optic Neuritis = inflammation of the optic nerve
loss in these cases is usually very sudden and in many cases both eyes
condition may affect any breed, but appears to be more common in Maltese.
pupils are usually very dilated and not responsive to light.
examination of the optic nerve, signs of inflammation may or may not
be seen depending on what part of the nerve is affected (into the eye
versus behind the eye).
cause is suspected to be immune-mediated inflammation, however some
cases may be related to an inflammatory condition of the brain called
GME = Granulomatous Meningoencephalitis.
(electroretinogram) is normal in cases of optic neuritis.
is oral cortisone tablets.
50% of cases respond and some vision is regained. This may only be in
one eye, suggesting that the inflammation was present in one eye first.
there is no improvement with cortisone, further tests can be performed
including imaging of the brain (CT scan or MRI).
Tumour at the optic chiasm
tumours can grow in a position that affects the crossover point of the
tumour may extend from the nasal cavity or surrounding structures and
compress the optic nerves. In such cases other signs may be seen (eg
nasal discharge or sneezing).
pupils are usually dilated and non-responsive, and ERG is normal.
of this condition is by skull and
brain imaging techniques (Xrays and scans).
of central blindness include:
2. Brain haemorrhage
3. Inflammation of the brain
4. Liver shunts In cases of central blindness, the pupils are usually normally
responsive to light and ERG testing is normal.
of such conditions is via brain imaging techniques (CT or MRI) Liver shunts
are most common in younger animals and affected animals usually show other
neurological signs. Diagnosis of this condition is via blood tests etc.
is very beneficial in differentiating different causes of sudden
vision loss. This can be important with respect to possible cortisone
therapy, as this may be contraindicated in some animals.