‘They will look but will not see’ – World Blind Day 2017
World Blind Day was marked on the 15th of October
2017.
To commemorate the day, I would like to focus on a variant
of blindness called cortical blindness which is of much interest to Neurologists
and afflicts many people worldwide. These are people ‘’who look but do not see’’.
In Nigeria, we may come across such individuals in our daily lives.
Cortical blindness is complete or partial visual loss
usually caused by a lesion in the occipital cortex affecting geniculo-calcarine
fibres of the visual pathway. It commonly results from vascular events (stroke
affecting the posterior cerebral artery territory) but may also be due to
cardiac surgery, brain surgery, post- cerebral angiography, traumatic brain
injury and seizures. Usually the structures of the eye are normal on
examination in cortical blindness.
Patients with cortical blindness may surprisingly be unaware
of this visual loss and deny such (Anton’s syndrome). Some present with
hallucinations and will also have other neurological deficits present. Cortical
blindness may coexist with other visual field defects such as hemianopias. A
proportion of patients with cortical blindness may be able to see moving
objects but not stationary ones.
Apart from the clinical work up, electroencephalograms (EEGs)
tend to show loss of posterior occipital alpha activity in cases of cortical
blindness while neuroimaging findings are quite characteristic. Both of these investigative modalities are
readily available for most Neurologists in major centres in Nigeria.
Prognosis is variable in cortical blindness. Full or partial
recovery of sight can occur. Studies have shown that while prognosis is worst
following a stroke, it tends to be better for those younger than 40 years,
those without the cerebrovascular disease risk factors of hypertension or
diabetes mellitus and in those without cognitive, communication or memory
difficulties.
So, how many people do you know that look but do not seem to
be seeing? They may need to ‘see’ the Neurologist.
Celebrate your sight.
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