Retinal Prosthesis Dissertation - Student Home Pages

Num. of: Num. of: f pixel T pixel_allocation @1fps @25fps @50fps @100fps
rows columns pixel_numbers T (pixel) {secs} f aer_pkt f aer_pkt f aer_pkt f aer_pkt
1 2 2 5.00E-01 2 50 100 200
2 2 4 2.50E-01 4 100 200 400
4 4 16 6.25E-02 16 400 800 1600
8 8 64 1.56E-02 64 1600 3200 6400
16 16 256 3.91E-03 256 6400 12800 25600
32 32 1024 9.77E-04 1024 25600 51200 102400
64 64 4096 2.44E-04 4096 102400 204800 409600
128 128 16384 6.10E-05 16384 409600 819200 1638400
256 256 65536 1.53E-05 65536 1638400 3276800 6553600
512 512 262144 3.81E-06 262144 6553600 13107200 26214400
1024 1024 1048576 9.54E-07 1048576 26214400 52428800 104857600
Table 1 Correlation between fps and AER packet frequency
1.3 Sub retinal 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. The retinal processing can be described using 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 [34, 54, 88,
94-128].
1.4 Introduction to stimulators
The stimulator (microstimulator) circuitry [53, 54, 57, 129] forms the post
processing stage of current retinal implants (sub and epi) and will also be required as
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