Contrast Sensitivity With a Subretinal Prosthesis and Implications for Efficient Delivery of Visual Information

Area of Science:

• Neuroscience
• Biomedical Engineering
• Ophthalmology

Background:

• Degenerative retinal diseases cause vision loss by damaging photoreceptors.
• Subretinal prostheses aim to restore vision by electrically stimulating the remaining retinal neurons.

Purpose of the Study:

• To evaluate the contrast sensitivity of a degenerate retina stimulated by a photovoltaic subretinal prosthesis.
• To assess how low contrast sensitivity impacts visual information transmission.

Main Methods:

• Ex vivo measurement of contrast sensitivity in healthy and degenerate rat retinas stimulated by a subretinal prosthesis (>20 Hz).
• Simulation of eye movement effects on retinal ganglion cell (RGC) activity using a linear-nonlinear model.

Main Results:

• Retinal ganglion cells showed transient responses to light changes with prosthetic stimulation.
• Prosthetic vision exhibited significantly reduced contrast sensitivity (65% changes) and dynamic range compared to natural vision (3-7% changes).
• A model predicted insufficient contrast sensitivity for triggering RGC activity via fixational eye movements.

Conclusions:

• Prosthetic vision has 10x lower contrast sensitivity and 2x lower dynamic range than natural vision.
• Low contrast sensitivity and absence of OFF responses limit visual information delivery via subretinal prostheses.