| How does
a visual field loss happen? |
| |
| Why do I have a visual field loss
even though my eyes are fine? |
The light rays of an object are gathered
through the optical apparatus (cornea, aqueous fluid,
lense, vitreous body) and appear upside down and smaller
on the retina. The visual impression is then transferred
into electrical impulses. These are then routed via the
optical nerve, the visual pathway and the visual cortex
to the anterior cerebral cortex. Here the processing of
sight information is carried out: colours, shapes, proportions
or patterns are recognised here.
The information is transferred from the visual centre
to many other regions of the cerebral cortex. This is
how familiar persons or objects are recognised, reading,
finding the correct way und the correct control of hand
movements is carried out. |
| |
 |
| |
| If there is nerve damage (lesions)
on the path between the retina to the visual centre or
in the visual centre itself then the original "picture"
can only be partially transferred or processed. In the
unprocessed part the affected person is blind – he
or she has a visual field loss in that area. |
| |
| I. |
optic nerve
= Nervus opticus |
| II. |
optic chiasm
= Chiasma opticum |
| III. |
optic tract
= Tractus opticus |
| IV. |
primary visual
centre (lateral geniculate body) = Corpus
geniculatum laterale |
| V. |
optic radiation
= Radiation optica |
| VI. |
visual cortex
= kortikales Sehzentrum |
|
 |
|
| |
| As a result of damage to the visual
centre in the right hemisphere both eyes but only the
left visual field are affected,. the affected person is
unable to see anything left of centre through either eyes.
This type of visual impairment is called a "left-sided
hemianopia". |
| |
 |
