Visual Sensory Devices
Retinal prostheses are neurosensory devices intended to stimulate the degenerate retina in blind patients to elicit sensations of light termed “phosphenes” to provide useable vision. Little is known about what levels of electrical and optical stimulation are safe for the degenerate retina. The mission of this laboratory is to develop metrics to evaluate safer and more effective methods of retinal cell stimulation by prosthetic devices. We have developed a novel transparent tube stimulation electrode method which when combined with optical coherence tomography (OCT), allows us to study neurons and retinal tissue directly under stimulus electrodes in real time during pulse train stimulation.
Optical coherence tomography and transparent electrodes allow accurate measurement of electrode access resistance with retinal proximity.
Confocal reconstruction of an alpha retinal ganglion cell recorded in the isolated live retina.
Example of the use of optically transparent stimulus electrodes to study in real time the effects of overstimulation of the retina directly under the stimulus electrode.
Current projects include:
- Optical evaluation of the relation of the stimulus electrode pulse waveform to electrode-retina proximity.
- Evaluation of microglia cells as indicators of retinal damage from overstimulation.
- Evaluation of neurotoxins in real time on retinal tissue using an optically transparent microapplicator tubes and OCT. (CDRH/CDER)
The results of these projects have provided FDA with a better understanding of how the retinal layers are activated by electrical stimulation pulses and determine what levels of electrical stimulation are safe for retinal tissue. Our projects support the regulatory review mission of the Agency, as the measurement of access resistance with tissue proximity may allow the evaluation of more efficacious electrode to target placement directly in implanted patients.
For more information, visit www.artificialvision.org.
Current funding sources
Ethan Cohen, Ph.D.
Anant Agrawal, Ph.D.
Daniel X. Hammer, Ph.D.
T. Katherine Shea
- Leica upright laser confocal physiology microscope
- Patch clamp slice Normarski imaging workstation
- Patch clamp retinal photostimulation with Normarski imaging workstation
- Photomicrography fluorescence workstation
Relevant standards & guidances
Selected peer-review publications
- Iacono et al., MIDA: A Multimodal Imaging-Based Detailed Anatomical Model of the Human Head and Neck
- Majdi et al., The use of time-lapse optical coherence tomography to image the effects of microapplied toxins on the retina
- Iacono et al., A computational model for bipolar deep brain stimulation of the subthalamic nucleus. Conf Proc
- Johnson et al., A novel high electrode count spike recording array using an 81920 pixel transimpedance amplifier-based imaging chip
- Minnikanti et al., Quasi-static analysis of electric field distributions by disc electrodes in a rabbit eye model
- Fohlmeister et al., Mechanisms and distribution of ion channels in retinal ganglion cells: Using temperature as an independent variable
- Cohen et al., Effects of high level pulse train stimulation on retinal function
- Cohen et al., Prosthetic interfaces with the visual system: biological issues