Image processing for a high-resolution optoelectronic retinal prosthesis

Alon Asher*, William A. Segal, Stephen A. Baccus, Leonid P. Yaroslavsky, Daniel V. Palanker

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


In an effort to restore visual perception in retinal diseases such as age-related macular degeneration or retinitis pigmentosa, a design was recently presented for a high-resolution optoelectronic retinal prosthesis having thousands of electrodes. This system requires real-time image processing fast enough to convert a video stream of images into electrical stimulus patterns that can be properly interpreted by the brain. Here, we present image-processing and tracking algorithms for a subretinal implant designed to stimulate the second neuron in the visual pathway, bypassing the degenerated first synaptic layer. For this task, we have developed and implemented: 1) A tracking algorithm that determines the implant's position in each frame. 2) Image cropping outside of the implant boundaries. 3) A geometrical transformation that distorts the image appropriate to the geometry of the fovea. 4) Spatio-temporal image filtering to reproduce the visual processing normally occurring in photoceptors and at the photoreceptor-bipolar cell synapse. 5) Conversion of the filtered visual information into a pattern of electrical current. Methods to accelerate real-time transformations include the exploitation of data redundancy in the time domain, and the use of precomputed lookup tables that are adjustable to retinal physiology and allow flexible control of stimulation parameters. A software implementation of these algorithms processes natural visual scenes with sufficient speed for real-time operation. This computationally efficient algorithm resembles, in some aspects, biological strategies of efficient coding in the retina and could provide a refresh rate higher than fifty frames per second on our system.

Original languageEnglish
Pages (from-to)993-1004
Number of pages12
JournalIEEE Transactions on Biomedical Engineering
Issue number6
StatePublished - Jun 2007


  • Biomedical image processing
  • Macular degeneration
  • Retinal prosthesis
  • Retinitis pigmentosa


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