[Rice Catalyst Issue 14]

Comparing Electrode and
Optogenetic Solutions
for Artificial Sight
KATHERINE WU
ABSTRACT
Electrode-based systems and optogenetics
are two distinct methods that address
blindness by developing artificial vision.
Optogenetics is a rapidly evolving field that
involves the use of light to control the activity
of cells in living tissue, typically neurons.
Some current areas of research include
designing smaller and more efficient
optogenetic devices, developing new ways
to target specific cell types, and using optogenetics
to study and treat a wider range of
brain disorders. By comparison, electrode-based
solutions for restoring vision
involve implanting an array of electrodes
to bypass a damaged retina and stimulate
remaining cells in the visual pathway, allowing
people with certain retinal diseases to
regain some level of visual perception. This
review discusses the effectiveness of both
electrodes and optogenetics in producing
artificial vision.
INTRODUCTION
Vision loss can have a profound impact on
an individual’s quality of life, affecting their
ability to engage in daily activities, maintain
independence, and participate in society.
Aging populations around the world are
beginning to experience greater rates of
age-related vision reduction, presenting
as macular degeneration, glaucoma, and
cataracts. Although an important public
health issue, the issue at hand necessitates
costly assistive devices and long-term
care. Therefore, continued research and
development in technologies to restore
and improve vision is an important area for
future investment.
OPTOGENETIC SOLUTIONS
Optogenetics is a technique that uses light
to control and study the activity of cells
Optogenetics is a technique
that uses light to control and
study the activity of cells in
the brain and other tissues,
allowing researchers to better
understand and potentially
treat neurological disorders.
in the brain and other tissues, allowing
researchers to better understand and
potentially treat neurological disorders.
Optogenetics uses a genetic tool called
the LoxP system to selectively control the
expression of specific genes in cells. LoxP
is a specific DNA sequence recognized by
a protein called Cre recombinase, which is
commonly used to manipulate the expression
of genes in cells. Cell genomes can be
edited by light-activated enzymes called Cre
recombinases that localize to flanking LoxP
sites at specific locations to either activate
or silence gene expression in a precise and
reversible manner. By selectively activating
or silencing gene expression optogenetics
can achieve gain-of-function or loss-of-function
of specific cells of living tissue [1].
Optogenetics uses light to control specific
neurons by introducing a protein into the
neurons that responds to light; when light
is shone on these neurons, the protein activates
or deactivates the neuron, allowing
researchers to study the effects of specific
neural activity on behavior or physiology. In
optogenetics, two proteins are commonly
introduced into neurons. The first are opsins.
Opsins are light-sensitive proteins that
respond to different wavelengths of light,
and they can be used to activate or inhibit
neural activity depending on the type of
opsin used. The second protein is enzymes.
Enzymes are proteins that can be activated
by light to perform specific chemical reactions,
and they can be used to manipulate
various signaling pathways or biochemical
processes within neurons. By introducing
these proteins into neurons, researchers
can control the activity of the neurons with
light, allowing them to better understand
how neural activity contributes to behavior
and disease [Figure 1].
Manipulating gene expression of specific
cells using proteins and light allows
individuals to experience a phosphene,
which is a sensation of light without any
light actually entering their eyes. These
FIGURE 1: Shining intense red (635nm) light
opens the rhodopsin, allowing ions to flow
into the neuron. The result is neuronal
activation and specific behavior. In optogenetics,
rhodopsins are used to activate
neurons by allowing the influx of positively
charged ions into the cell in response to
light. This causes the neuron to depolarize
and fire an action potential, allowing
researchers to control the activity of the
neuron with light.
2022-2023 C A T A L Y S T | 2 5