Table 1.

Summary of neuronal optical stimulation schemes

Optical stimulation scheme	Pros	Cons
Retinal implants
External light capturing device	– Mature technology – High charge injection – Variable stimulation patterns	– Low spatial resolution – Wiring – Invasive – Rigid
Photodiodes	– Mature technology – Compact – Large electrode array – Variable stimulation patterns	– Wiring – Invasive – Rigid
Light directed neuronal stimulation
Optogenetics	– High temporal and spatial resolution – Cell specificity – Minimally invasive	– Long-term expression of light sensitive proteins – Immune system response
Caged glutamate	– High spatial resolution – Minimally invasive	– Low temporal resolution – Poor cell selectivity – Need for repeated injection of neurotransmitters
Infrared light	– High spatial resolution – Noninvasive	– Light source should be at close proximity – Thermal tissue damage – Technical difficulty in realizing high density prosthesis
Photoactive surfaces
Photoconductive silicon	– High spatial resolution – Simple	– Limited temporal resolution – Limited stability – Wiring – Invasive – Rigid
Conducting polymers	– High spatial resolution – Simple fabrication and deposition – Flexible	– Low stability upon continuous stimulation – Toxic polymerization residues – Invasive
Quantum dots	– High efficiency – Stable – Flexible	– Toxic – Invasive