Method and apparatus for predicting and controlling the percepts induced by a visual prosthesis
Here we present the first model that quantitatively predicts the apparent spatial position and shape of percepts elicited by retinal electrical stimulation in humans based on the known anatomy of the retina. This model successfully predicts both the shape of percepts elicited by single electrode stimulation and the shape and relative positions of percepts elicited by multiple electrode stimulation. Model fits to behavioral data show that sensitivity to electrical stimulation is not confined to the axon initial segment, but does fall off rapidly with the distance between stimulation and the initial segment. Using the model, it is possible to compensate, preferably with a look up table, to match percepts to a desired image.
1. A method of inducing the perception of light with a visual prosthesis comprising:
observing the location of an electrode array of the visual prosthesis as it relates to axonal patterns, including observing which of two or more electrodes are across a single axon, which of the two or more electrodes is closest to the raphe, or which electrodes are not over axons;
applying a formula predictive of percept shapes to said observations; and
altering stimulation patterns based upon said observations and said formula.
2. The method according to claim 1 , further comprising storing results of the step of applying a formula in a look up table, and wherein the step of altering stimulation patterns includes altering stimulation patterns based upon the look up table.
3. The method according to claim 1 , wherein the step of altering stimulation patterns includes not stimulating electrodes that fall within an induced percept of another electrode.
4. The method according to claim 1 , wherein the method is performed by an automated process using a photographic image of the array on the retina.
5. The method according to claim 4 , wherein photographic image is a fluorescent angiography.
6. The method according to claim 1 , wherein the step of observing is by fluorescent angiography.
7. The method according to claim 1 , wherein the steps of observing and applying are completed by computer which is detachable from a visual prosthesis and the step of altering is performed by the visual prosthesis.