AMD Basics
Our eyes operate like complex machines and include several
structures:
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At the front of the eye is the cornea, which is
responsible for letting in light and bending its rays toward the
retina.
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The retina lines the inside of the eye and is
responsible for converting light into signals that the brain can
see as visual images.
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The layer under the retina is the choroid, which
carries the blood supply necessary to nourish the eye's internal
structures.
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The central layer of tissue in the retina is
called the macula, which is responsible for central vision.
Photoreceptors
The retina contains a layer of light-receiving photoreceptor cells
that are directly connected to the brain by the optic nerve. If you
think of the eye as a camera receiving images, then the retina is
the film where those images are recorded.
There are two types of photoreceptor cells in the retina: cone cells
and rod cells. Densely packed within the macula, cone cells are
responsible for central vision and color perception. Rod cells are
found outside the macula and are mainly responsible for peripheral
and night vision.
In the retina, the cone and rod cells convert light
into electrical impulses that travel to the optic nerve. The optic
nerve then carries these electrical impulses to the visual cortex of
the brain, where 'seeing' actually occurs.
When you have macular degeneration, the central part of the retina
deteriorates, affecting the cone cells. This causes problems with
central vision.