Retinal Prosthesis Dissertation - Student Home Pages

Young and Hermann von Helmholtz, by proposing four hue primaries: red, green,
yellow, and blue, instead of the traditionally accepted
three: red, green, and blue.”[232]
A biomedical smart sensor for the visually
impaired
“The main advantage of the epi-retinal implant is the greater ability to dissipate heat
because it is not embedded under tissue. This is a significant consideration in the retina.
The normal temperature inside the eye is less than the normal body temperature of 98.6º
Fahrenheit. Besides the possibility that heat build-up from the sensor electronics could
jeopardise the chronic implantation of the sensor, there is also the concern that the
elevated temperature produced by the sensor could lead to infection, especially since the
implanted device could become a haven for bacteria” [106]
Subretinal versus Epi-retinal
Typically the subretinal implant is embedded `underneath’ the retina and uses
photodiodes to replace damaged photoreceptors, relying on natural sunlight for power.
However as the retina uses Ewald Herings theory[42] in which in 1878 he wrote:
"Yellow can have a red or green tinge, but not a blue one; blue can have only either a
red or a green tinge, and red only either a yellow or a blue one. The four colours can
with complete correctness therefore be described as simple or basic colours, as
Leonardo da Vinci has already done." Whereas at the optic nerve ganglion cells act on
the trichromacy theory[93] i.e. red, green and blue this implies a conversion between
one form to the other. As an epiretinal implant effectively replaces the retinal function
such a conversion can be avoided.