LOGARITHMIC LIGHT INTENSIFIER FOR USE WITH PHOTORECEPTOR-BASED IMPLANTED RETINAL PROSTHETICS AND THOSE PROSTHETICS

Abstract: The invention is for directly modulating a beam of photons (102) onto the retinas of patients who have extreme vision impairment or blindness. The purpose is to supply sufficient imaging energy (108) to retinal prosthetics implanted in the eye which operates essentially by having light (external to the eye) activating photoreceptor. The invention supplies light amplification logarithmical (3).

Description: WO 00/56244 PCTtUSOO/05753 LOGARITHMIC LIGHT 1NTENSIFIER FOR USE WITH PHOTORECEPTOR- BASED IMPLANTED RETINAL PROSTHETICS AND THOSE PROSTHETICS. This application claims the benefit of U. S. Provisional Application No. 60/125,875, filed March 24. 1999. FIELD OF THE INVENTION This invention relates generally to retinal prosthetics and more particularly to a method and apparatus for enhancing retinal prosthetic performance. This invention relates to directly modulating a beam of photons of sufficient energy onto retinal prosthetic implants of patients who have extreme vision impairment or blindness. BACKGROUND OF THE INVENTION A healthy eye is has photosensitive retinal cells (e.g. rods and cones) which react to specific wavelengths of light to trigger nerve impulses. Complex interconnections among the retinal nerves assemble these impulses which are carried through the optic nerve to the visual centers of the brain, where they are interpreted. Certain forms of visual impairment are primarily attributable to a malfunction of the photosensitive retinal cells. In such cases, sight may be enhanced by a retinal prosthesis implanted in a patient's eye. Michelson (U.S. Patent No.4, 628,933) and Chow (U.S. Patent Nos. 5,016,633; 5,397.350; 5,556,423) teach a retinal implant, or implants, of essentially photoreceptors facing out of the eye toward the pupil, each with an electrode which can stimulate a bipolar, or similar, cell with an electrical impulse. This bipolar cell is acted upon by the electrical stimulus, to send appropriate nerve impulses essentially through the optic nerve, to the brain. This invention is postulated as a necessary complement to this type of prosthesis, because the photoreceptors do not appear to be sensitive enough to the ordinary levels of light entering the eye in that not enough current is produced to sufficiently stimulate the retinal cells. Consequently, a light amplifier, or "helper" device would be needed. That device is the invention herein described, which also includes special characteristic implants. Fumess. et al. teach a "virtual retinal display". U.S. Patent No. 5,659.327. where "The virtual retinal display...utilizes photon generation and manipulation to create a panoramic, high resolution, color virtual image that is projected directly onto the retina of the eye...there being no real or aerial image that is viewed via a mirror or optics." Richard, et al. teach, U.S. Patent No. 5.369,415. * '...a direct retinal scan display including the steps of providing a directed beam of light, modulating the beam of light to impress video information onto the beam of light, deflecting the beam in two orthogonal directions, providing a planar imager including an input for receiving a beam of light into the eye of an operator which involves a redirection diffractive optical element for creating a virtual image from the beam of light on the retina of the eye, and directing the beam of light scanned in two orthogonal directions and modulated into the input of the planar imager and the output of the planar imager into the eye of an operator." Sighted individuals can use these devices above for their intended uses. However, they appear unsuitable for use by blind individuals with implanted retinal prosthetics of the photoreceptor-electrode kind. It would seem that they do not provide enough light power. Moreover, light amplitude cannot be arbitrarily increased because according to Slinly and Wolbarscht, Safety with Lasers and Other Optical Sources, the retinal threshold damage is 0.4 Joules per square centimeter. SUMMARY OF THE INVENTION The present invention is directed to a method and apparatus for providing enhanced retinal prosthetic performance. More particularly, the invention is directed to a light amplifier and electrical circuitry for driving an implanted retinal prosthesis to maximize electrical stimulation of the retinal nerves or cells, while avoiding damage thereto. The invention is also directed to improved implanted retinal prostheses, which maximize the advantages of the light amplifier. In accordance with one aspect of the invention, light reflected from a viewed image (i.e.. input image) is passed through a light amplifier to produce an output image which is applied to the photoreceptor array of a retinal prosthesis. The gain (or "transfer function " ) of the light amplifier enables the photoreceptor array to drive output electrodes for producing retinal e impulses ot sufficient magnitude to enhance perceived sight In accordance with another aspect of the invention, the light amplifier preferably compresses the range of light intensity, e g . logarithmically, to enable maximum light amplification without overdm mg the prosthetic photoreceptors In accordance with another aspect of the invention, the electrical stimulation of the retinal nerves is preferably pulsed, 1 e . periodically interrupted to avoid any damage attributable to peak magnitude electrical signals Peπodic interruption can be implemented mechanically by a shutter periodically interrupting the light incident on the photoreceptor array and/or electrically via an appropπate wave shaping circuit In accordance with another aspect of the invention, the implanted prosthetic's electrodes generate a sequence of positive and negative pulses to avoid producing a net charge in the eye Successive pulses are preferably spaced m time by an interval Δt Four preferred embodiments are described In accordance with the first embodiment of the invention a single wavelength is relied upon to activate a combined photodetector-electronics-electrode implanted unit which then produces a negative pulse, followed by a time delay, followed by a positive pulse A photoreceptor implanted in the eye acts to produce an electrical stimulation with an equal amount of positive and negative charge A single light wavelength is received by the photoreceptor That single wavelength contains extractable energy It also contains information, which may be encoded by amplitude modulation, frequency modulation, phase shift methods or pulse width modulation, for example The photoreceptor activates an electrode with associated electronics The electronics produces a negative pulse followed by a time delay followed by a positive pulse A net charge of zero is introduced into the eye by the electrode-oπg ating electπcal pulses The preferred delay time is in the range 0 1 millisecond to 10 milliseconds, with the delay time of 2 milliseconds is most preferred When the retinal cell is not being electrically stimulated, it returns to a rest and recovery state It is then in a state, electrically, that it was in prior to stimulation by the first electπcal stimulation In accordance w ith the second embodiment, a first \\ a\ elength is used to stimulate a first set of "electronic" photoreceptoi s These photoreceptors are connected so that the stimulation oi the attached, or associated, electrodes results in a negative pulse This negativ e pulse pi ov ides retinal cell stimulation Then the shutter cuts in and stops light transmission to the eye The retinal cell is in a rest and recovery state so that it returns, electrically, to the state it was in pπoi to stimulation bv the first particular \\ avelength of light A second paπicular w a\ elength of light then stimulates a second set of photoreceptors which are sensitiv e to that wav elength of light, while the first set -. of photoreceptors are not affected This second set of photoreceptors is connected so that the stimulation of the attached, oi associated, electrodes results in a positive pulse The net charge introduced into the retinal cells must balance So the positive charge introduced by the positive pulse must equal the negative charge introduced by the negative pulse. Again, the shutter cuts in and stops light transmission. Again, the 10 retinal cells rest and recover and the process repeats An aspect of the second embodiment is using an electro-optic, electronic or mechanical shutter to provide a period of no electrical stimulation to the retinal cells targeted for electπcal stimulation. In accordance with a third embodiment, which is a cross, so to speak, between the first and second embodiments two different wavelengths and two different types of 15 diodes, each responsive to a corresponding wavelength are used In this embodiment, one wavelength is used to pump in a high constant level of light to supply power to the electronics component The other wavelength is used to send m information via amplitude, frequency, phase, pulse-width modulation, or combinations thereof. The stimulation pulse from the electronics to the electrode to the retinal cell is generated m 20 a fashion similar to the pulses generated in the first embodiment, with a single wavelength A fourth embodiment is that of the logarithmic light amplifier itself, without any special implantable photoreceptors. This last embodiment may require a low duty cycle when used with photoreceptors connected to a diode without any electronics It 25 may be able to rely sufficiently upon the intrinsic capacitance of an oxidizable electrode, which acquires capacitance with the buildup of an insulating oxidized layer toward the lonizable fluid present in the eye as vitreous fluid, or fluid directly associated with the eye An image receiver with a first convener for the image, converts the image into ^0 electrical signals The signals ai e amplified, basically logarithmically, so as to provide brightness compression for the patient An aspect of the embodiments of the inv ention is that an amplified electrical signal is converted by a second conv erter into a photon-based display, the photons of this display entei an eye through the pupil of the eye Moreov ei . while the embodiments ol the logarithmic ampli fier inv ention hav e sufficient output light power, advantageouslv . the output light lev el still remains at a safe lev el This aspect of the invention corresponds to aspects of the action of the ins, as w ell as the biochemistry of retinal cells, in the human eve in making possible sight over many oiders of magnitude of ambient bπghtness An aspect of the embodiments of the invention is incorporation of both optical and electronic magnification of the image, as for example, the incorporation of an optical zoom lens, as well as electronic magnification Consequently, it is feasible to focus in on items of particular interest or necessity With proper adjustment, proper threshold amplitudes of apparent bπghtness would obtain, as well as comfortable maximum thresholds of apparent brightness Therefore, to adjust for these, an adjustment aspect is incorporated in each embodiment, such that proper adjustment for the threshold amplitudes and maximum comfortable thresholds are made Another aspect of the invention, which may be incorporated in all embodiments, is oriented toward making color vision available, at least to a degree To the extent that individual stimulation sites (e g , retinal cells generally, bipolar cells specifically) give different color perceptions upon stimulation, the color of selected pixels of the viewed scene is correlated with a specific photoreceptor-electronics-electrode units located so as to electncally stimulate a specific type of bipolar cell to provide the perception of color vision In order to help implement both comfortable adjustment of threshold and maximum bπghtness, and color vision, the logarithmic light amplifier also incorporates within itself, a data processmg unit which, semi-autonomously. cycles through the various photodetector-electrode and combinations thereof, inteirogates the patient as to what the patient sees, the patient then supplies the answers, setting up proper apparent brightness, proper apparent color and proper perception This setup mode is done by the use of a keyboard, display, and auxiliary processor, which are plugged into the data processing unit of the logarithmic light amplifier during the setup proceduie A scanning laser feedback is provided in different embodiments of the invention to keep the scanner laser scanning the correct locations An imaging of the reflected scanning laser reflected back from the retinal implant is used to provide real-time feedback information, utilizing a second imager v iew ing into the eye and a data processor unit tied into the scanning laser scan control unit BRIEF DESCRIPTION OF THE DRAWINGS The above and other features and advantages of the invention will be more apparent from the following detailed description wherein: Figure 1 shows the logarithmic light amplifier with shutter, showing the incoming scene or view photons on the right and the eye on the left; Figure 2a shows a laser being modulated by a video signal and scanning the full extent of the implanted retinal prosthesis; Figure 2b shows a photoreceptor. associated electronics, and an associated electrode; Figure 2c shows the apparatus of Figure 2b but in a more rounded, smoother packaged form, likely more amenable for implantation into the eye; Figure 3 depicts tuned photodetectors on an implanted retinal prosthesis; Figure 4 shows a sample waveform possible with the apparatus shown in Figure 3; Figure 5 shows two different wavelengths, one to send in power, the other to send in information, to a single unit with two differently sensitive photoreceptors, one electronics package and one electrode; Figure 6 summarizes three embodiments as shown previously; Figure 7 shows the external logarithmic amplifier (as "glasses"), a portable computer with mouse and joystick as setup aids; Figure 8 shows an implant unit (old in the art) with a photoreceptor and an electrode; Figure 9a shows a light-electronic feedback loop for knowing location on implant being scanned; Figure 9b shows one of different possible fiduciary markings including here points and lines for aiding knowing location on implant being scanned. DESCRIPTION OF THE PREFERRED EMBODIMENTS The follow ing description is of the best mode presently contemplated for carrying out the in ention This description is not to be taken in a limiting sense, but is merely made for the purpose of describing the general principles of the inv ention The scope of the invention should be determined with reference to the claims This inv ention provides amplified light for artificial photoreceptors implanted in the eye of a patient who has lost the use of his/her normal photoreceptor retinal cells The purpose of this amplified light is to effectively stimulate the artificial photoreceptors The artificial photoreceptors. in turn, provide electrical stimulation through associated electrodes, usually via some electronics, to retinal cells, which are normally stimulated by living retinal photoreceptors such as cones and rods. The retinal cells, which get electncally stimulated by vvay of the artificial photoreceptors, are typically bipolar cells This stimulation to these non-photoreceptor retinal cells allows the patient to have at least some perception of what a normal eye would see In order not to damage the retinal cells, light is fed to the photoreceptor-electrode stimulators m the following ways Four preferred embodiments are descnbed In the first embodiment a single wavelength is relied upon to activate a combined photodetector-electronics-electrode implanted unit which then produces a negative pulse, followed by a time delay, followed by a negative pulse In the first embodiment, a photoreceptor implanted m the eye acts to produce an electncal stimulation with an equal amount of positive and negative charge A single light wavelength is received by the photoreceptor. The photoreceptor activates an electrode with associated electronics The electronics produces a negative pulse followed by a time delay followed by a positiv e pulse A net charge of zero is introduced into the eye by the electrode-originating electncal pulses The preferred delay time is in the range 0 1 millisecond to 10 milliseconds, with the delay time of 2 milliseconds is most prefened When he retinal cell is not being electrically stimulated, it returns to a rest and recovery state It is then in a state, electrically, it was in prior to stimulation by the first electrical stimulation Starting w ith the logarithmic amplifier, an image receiver with a first converter for the image, com erts the image into electrical signals The signals are amplified, basically logarithmically, so as to provide brightness compression toi the patient The amplified electrical signal is conv erted by a second conv erter into a photon-based display, w herein said photons of said display enter an eye through a pupil of said eye Photons ( 102) from a v le ed scene ( not shown ) enter the logarithmic amplifier ( 1000) bv w av of the lens ( 101 ) The light amplifier ( 1000) has an image receiv er ( 1 ). a first conv erter ( 1 03 ) of the image into electrical signals an amplifier (2) of said electrical signals w hereby the ov erall amplification of said electrical signal according to a definite functional relationship between input signal to the amplifier and an output signal fiom the amplifier, a second con erter ( 107) of said amplified electrical signal into a photon-based display (7), such that the of display photons ( 108) enter an eye (5) through the pupil ( 105) of the eye (5) In the case w here the imager ( 1 ) is a type of video camera, the image recei er and conv ersion to electrical signals may occur in a package (old in the art) A display (7) that is a source of photons such as a laser (coherent light source) (7), or a non-coherent source such as colored LEDs (7) or a plasma display (7), is used to send photons directly to an implant near the retina These displays (7) are made very bπght, but not such as to impact negativ elv on the ey e In our cases, the patient has sufficient retinal degeneration so as to be unable to see without the aid of a retinal prosthetic In the case where the display (photon source) is a laser (7), that laser is scanned over the implanted photodetector-electro cs-electrode array (Figure 2, (8) in accordance with the scene being displayed to the eye A scanning laser is a laser with scanning means (old in the art) Referencing Figure 2a, the video signal (6) is applied to a scanning laser (7), a scanning laser being a laser with scanning means (old in the art) The scanning laser (7) is scanned over the retinal prosthesis m a square or rectangular pattern or m a raster pattern with an exact fit to the prosthesis (8) The v ideo signal (6) supplies amplitude from the data processor (Figure 1 , (2)), and if desired (see Figure 1 ), color information, of the scene being viewed, from the individual color amplifiers (3) to the laser (7), which information is used to modulate the laser In a preferred mode, the light amplifier ( 1000) is a logaπthmic amplifier. In another preferred mode, the amplifier amplifies according to a different function than the logarithmic function or a modified logarithmic function, for example, an algebraic function such as a polynomial function multiplied bv the logarithmic function The imager or camera lens is sho n schematically as ( 101 ) The signal is logaπthmicallv amplified as a w hole at the electronic processor (2), or the individual RGB (led, green, blue) or RGBY (red. gieen. blue, v ellovv) color components are individuallv logarithmically amplified (3) Another color component mix of white light may be used The individual amplification ( 3) of separate color components allows for the relative super-amplification of one color to hich the photoreceptors are particularly sensitiv e If onlv a ' black-and-w hite" contrast image is displayed, the "white " part of that image is logaπthmicalK translated to the color. 1 e velength, to which the photoreceptors are most sensitiv e This feature includes shifting the wavelength toward oi to the near infrared 01 toward or to the near ultraviolet, according to what is needed to optimize the response of the implanted photosensitive elements Consequently, a mapping of the incoming image data to an appropriate output is possible This mapping could be complex, for example, producing bφhasic waveforms as shown Figure 4 by appropriate timing of two lasers operating at different wavelengths and photosensitive elements uniquely sensitive to these wavelengths In a preferred mode, individual RGB (red, green, blue) or RGBY (red, green, blue, yellow) color components are amplified separately (3), or amplified together (2) and separated out (3) after the amplification These color components may be used to stimulate particular photosensitive elements of the retinal ιmplant(s) For example, a cell ("blue-sensation") producing a sensation of blue color is stimulated when the scene being transmitted to the eye has blue, which in the projected (into the eye) scene would have blue in the vicinity of that blue-sensation cell The loganthmic amplification is necessary to compress the range of onginal bπghtness The normal eye does this automatically of closing down the pupil size, squinting and employing other electrochemical cellular mechanisms This light amplifier accomplishes this necessary task by electronic loganthmic light amplification The light amplifier also includes an adjustable transformer or magnification of image size A shutter or electronically turning the scanning laser on and off are not a necessary part of this embodiment In the second preferred embodiment of the light amplifier two or more wavelengths are used to communicate light energy to the eye to allow balanced biphasic stimulation with no net charge injection into the eye A first wavelength is used to stimulate a first set of photoreceptors These photoreceptors are connected so that the stimulation of the attached, or associated, electrodes results in a negative pulse This negative pulse provides retinal cell stimulation Then the shutter cuts in and stops light transmission to the eye The time of this light interruption is prefeπed in the range 0 1 millisecond to 10 milliseconds, with the time of 2 milliseconds most preferred The retinal cell is in a rest and recov ery state so that it returns, electrically to the state it was in prior to stimulation by the first particular wavelength of light \ second wavelength of light then stimulates a second set of photoi eceptors w hich ate sensiti e to that wavelength of light; while the first set of photoreceptors are not affected. This second set of photoreceptors is connected so that the stimulation of the attached, or associated, electrodes results in a positive pulse. The net charge introduced into the retinal cells must balance, or equal, the net charge introduced by the negative pulse. Again, the shutter cuts in and stops light transmission. Again, the retinal cells rest and recover and the process repeats. In the second preferred embodiment. Figure 3 A. two scanning lasers, (9) and (10), are supplied with video signals, with each laser operating at a different wavelength. Advantageously, two or more photoreceptors ( 13), ( 14) are on the implant. The two types of photoreceptors (13), (14), are tuned to different frequencies of light, each of the frequencies being that of one of the emitting frequencies of the external lasers (9), (10). Figure 3B shows two incoming frequencies of light, (301 ) and (302). The light sources for the dual light frequencies (301), (302) is a unit (304) which is downstream in the information flow from the imager (Figure 1 , ( 101 ), (1), (103)) and amplifiers (Figure 1 , (2), (3)). The final output from the amplification stages is connected electrically or electromagnetically to the dual light frequency sources (304), in particular, dual scanning lasers operating with different wavelengths of light output. Pairs (303) of different frequency (i.e., wavelength) photoreceptors are placed on the eye-implant, each pair associated with an electrode (not shown). Together, the two types of photoreceptors (e.g., photodiodes) give rise to a biphasic current (Figure 4) at each electrode (not shown). Initially the rest state appears (40). Next, one of the photoreceptors (13) has been activated by its corcesponding laser (9). The current amplitude is negative. (41). After a time (42), laser (9) and photoreceptor ( 13) shut down and the amplitude returns to zero. Next, the other laser (10) actives its corresponding (in light wavelength) photoreceptor ( 14) and the amplitude is positive by an amount (43) and for a duration (44). Nominally, in absolute value, (41 ) = (43), and (42) = (44). However, in the case this is not exact, then the parameters (44) and (43) can be altered such that (41 ) * (42) = (43) * (44), where * indicates multiplication. This can be accomplished by measuring (41 ) and (42) and then altering (43) or (44) or both to maintain charge balance. A shutter (4) is part of the second embodiment. The shutter (Figure 1. (4)) is of a mechanical design (old in the art), or an electronic shutter (4) (old in the art) or an electro-optical shutter (4) (old in the art). The shutter (4) cuts off light from the logarithmic light amplifier ( 1000) to the pupil ( 105) of the eye (5). This decreases the total time that light strikes the photoreceptors ( Figure 3a. ( 13) ( 14)) (Figure 3b. 303) Consequently, the time during w hich the bipolar, or similar cells, are stimulated is decreased Because the eye is not functioning as oπginallv intended the bipolar, or similar, cells are thought to need this "down-time " to continue to function properly * -> An aspect of this in ention is the use of two or more wavelengths to allow balanced biphasic stimulation with no net charge injection into the eye As long as a biphasic type of electπcal stimulation here equal amounts of positive charge and negative charge in the form of ionic carriers or electrons or other charge carriers, enter the vitreous fluid of the eye, the electπcal effect on the eye is not harmful If direct 0 current is supplied to the eye, internally a charge imbalance results This excess of charge has been found to be harmful to cells Consequently, direct current can harm the bipolar and other cells Advantageously, the biphasic electrical stimulation tends to avoid this harm to the cells because no excess charge accumulates 5 A third embodiment that is a cross, so to speak, between the first and second embodiments uses two different wavelengths and two different types of diodes, each responsive to a corresponding wavelength In this embodiment, one wavelength is used to pump in a high constant level of light to supply power to the electronics component The other wavelength is used to send in information via amplitude, frequency, phase, pulse-width modulation, or combinations thereof The stimulation pulse from the electronics to the electrode to the retinal cell is generated in a fashion similar to the pulses generated in the first embodiment, with a single wavelength The third embodiment uses two different wavelengths and two different types of diodes, each responsive to a corcesponding wavelength (See Figure 3b (301 ), (302)) In this embodiment, one wavelength (Figure 5, (501 )) is used to pump in a high constant level of light to supply power to the electronics component (502) The other wavelength (503) is used to send in information via amplitude, frequency, phase, pulse- width modulation or combinations thereof to the electronics component (502) The stimulation pulse from the electronics (502) to the electrode (504) to the retinal cell is generated in a fashion similar to the pulses generated in the first embodiment, with a single wavelength See Figure 6 Figure 6 summarizes in block form the preceding three embodiments In the first embodiment theie is one w avelength (601 ) input to a single diode (602) ith electronics (603) and electrode (604) Eithei digitallv or bv analogue means, old in the art a d c signal occurring after the absorption of photons by the photoreceptoi is converted by the electronics to a signal (600) of the type shown in Figure 4. at the electrode In the second embodiment for two diffei ent w avelengths (610), (61 1 ), both carrying pow er and information impinging on two different photoreceptors (612), (613). the electionics (6033), digital oi analogue, again produce the waveform (600) of Figure 4 at the electrode (604) In the third embodiment, for two different photoreceptors (620). (621 ). the first receiving a steady state power wavelength (622). the second receiving a signal wav elength (623), the electronics (6034). digital or analogue, produces the signal (600) of Figure 4 at the electrode (604) The electronic circuitry of (603), (6033) and (6034) may be different A fourth embodiment is that of the logarithmic light amplifier (1000) itself, without any special implantable photoreceptors This last embodiment may require a low duty cycle w hen used with photoreceptors (Figure 8, (81 )) connected to an electrode (82) ithout any electronics It relies upon the intrinsic capacitance of an oxidizable electrode, which acquires capacitance with the buildup of an insulating oxidized layer toward the lonizable fluid present in the eye as vitreous fluid, or fluid directly associated with the eye In a first set of embodiments, the addition of a shutter (Figure 1 , (4)) with an off time of from 0 5 ms to 10 ms, most preferably 2 ms provides a mechanism to provide that off time (Figure 4, (47), (48)) However, in a second set of embodiments, the time each laser is on can be controlled by electronic means (old in the art) within the laser to provide equal positive pulses and negative pulses, I e , equal with respect to total signed charge introduced into a retinal cell The first and second sets of embodiments may be completely or partially coincident Another aspect of all of the embodiments is incorporation of both optical and electronic magnification of the image, as for example, the incorporation of an optical zoom lens, as w ell as electronic magnification Optical magnification of the image (see Figure 1 ) is accomplished by use of a zoom lens for the camera lens ( 101 ) Electronic magnification is accomplished electronically in an electronic data processing unit (2) or (3) Consequentlv. it is feasible to focus in on items of particular interest or necessity With proper adjustment, proper threshold amplitudes of apparent bπghtness obtain, as ell as comfortable maximum thresholds of apparent brightness Therefore, to adjust for these, a sixth aspect is incorporated in all of the embodiments such that proper adjustment tor the threshold amplitudes and maximum comfortable thresholds can be made To makes coloi vision available, to a degree, another aspect is incorporated To the extent that indiv idual stimulation sites (e g . bipolar cells) giv e different color perceptions upon stimulation, the color of selected pixels of the v iew ed scene is correlated with a specific pan of photoreceptors located so as to electrically stimulate a specific type of bipolar cell to provide the perception of color v ision In order to help implement these last two aspects of the preferred embodiments of this invention, apparent bπghtness control and the presentment of apparent color, the logarithmic amplifier also incorporates within itself, a data processing unit which cycles electncal pulses of varying amplitude and/or frequency and/or phase and/or pulse width through the vanous photodetector-electrodes and spatial combinations thereof, and, interrogates the patient, who then supplies the answers, setting up proper apparent brightness and apparent color A different aspect of the embodiments utilizes a plug m accessory data processor (Figure 7, (71 )) with display (72) and data input device or devices such as a keyboard (73), mouse (74), or joystick (75) Figure 7 show the plug in unit (71 ) which plugs (76) into the loganthmic light amplifier (1000) to provide additional data processing ability as well as expanded data input and data display capability In order for the scanning laser to correctly scan the retinal implant prosthetic photoreceptors, it is helpful if some feedback is provided to it One aspect of the different embodiments is the presence of a feedback loop using some of the reflected light from the scanning laser itself One aspect of the feedback loop is to use regions of different reflectivity on the surface of the retinal implant which allow the location, or relative location, of the scanning laser light beam to be determined A scanning laser feedback is provided in the different embodiments of the invention An imaging (Figure 9a) of the retinal implant from the reflected (92) incoming scanning laser beam (91 ), see Figure 9a, (7), (Figure l and Figure 2a, (7)), (Figure 3a, (9,), ( 10)) reflected back from the retinal implant (Figure 9, (8)) can be used to provide real-time feedback information, utilizing a second imager (93) viewing into the eye (5) and a data processor unit (94) tied into the scanning laser's scan control unit (95) Another aspect of the embodiments (Figure 9b) utilizes multiple fiduciary reflectiv e or light absorptive points (96) and/or lines ( 97) on the retinal implant (8) such that the frequency and signal pattern, mote genei allv. (98). (99) ( 100) of the high reflectivity from these reflectiv e, or absorptive lines/point for a given rate of scanning by the scanning laser (7) can be used to correct the scanning direction from the different frequency patterns, some indicating correct scanning, others indicating an incorrect scanning. While the invention herein disclosed has been descnbed by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the mvention set forth in the claims.

Claims: What is claimed is 1 Apparatus for enhancing the performance of a retinal prosthesis implanted in a patient's eve, said prosthesis being comprised of an array of photodetectors and a plurality of electrodes for stimulating retinal nerves, said apparatus comprising a light amplifier mounted external to the eye and responsive to an input image for producing an output image related to said input image by a transfer function G, said light amplifier being positioned so that said output image is incident on said implanted photodetector array, said plurality of electrodes being responsive to said output image incident on said photodetector array for producing a sequence of negative and positive electrical pulses for application to said retinal nerves, and wherein successive pulses are spaced in time by an interval Δt 2 A light amplifier with photoreceptor-based implanted retinal prosthetics compnsing a an image receiver, b a first converter of said image into electπcal signals, c an amplifier of said electπcal signals, d an overall amplification of said electncal signal according to a definite functional relationship between input signal to the amplifier and an output signal from the amplifier, e a transformer of the image size, f a second converter of said amplified electπcal signal into a photon- based display, wherein said photons of said display enter an eye through a pupil of said eye, g w herein a photoreceptor implanted in the eye acts to produce an electrical stimulation with an equal amount of positiv e and negative charge, h w herein a single light w av elength is received by the photoreceptor. l w herein said photoreceptor activ ates an electiode with associated electronics; j. wherein said electronics produces a negative pulse followed by a time delay followed by a positive pulse; k. whereby a net charge of zero is introduced into the eye by the electrode-originating electrical pulses. 3. The light amplifier of claim 2 wherein the image receiver and the first converter of said image into electrical signals is a video camera. 4. The light amplifier of claim 2 wherein said amplifier logarithmically amplifies said electrical signal. 5. The light amplifier of claim 2 wherein the transformer of the image size is a magnifier of the image size. 6. The light amplifier of claim 5 wherein the magnifier of the image size is an electronic magnifier. 7. The light amplifier of claim 5 wherein the magnifier of the image size is an optical zoom lens. 8. A light amplifier with photoreceptor-based implanted retinal prosthetics comprising: a. an image receiver; b. a first converter of said image into electrical signals; c. an amplifier of said electrical signals; d. an overall amplification of said electrical signal according to a definite functional relationship between input signal to the amplifier and an output signal from the amplifier; e. a transformer of the image size; f. a second converter of said amplified electrical signal into a photon- based display; wherein said photons of said display enter an eye through a pupil of said eve; g. a periodic interrupter of the photon stream from said photon-based display; h. wherein a plurality of cxternal-to-the-eye wavelengths provides light stimulation to an equal number of types, as the number of the plurality of wavelengths, of appropriately tuned photoreceptors. implanted in the eye, which act to result in electrical stimulation from associated electrodes with an equal amount of positive and negative net charge, as measured by amount of charge introduced into the eye, whereby the net charge introduced is zero. 9. The light amplifier of claim 8 wherein the image receiver and the first converter of said image into electrical signals is a video camera. 10. The light amplifier of claim 8 wherein said amplifier logarithmically amplifies said electrical signal. 1 1. The light amplifier of claim 8 wherein the transformer of the image size is a magnifier of the image size. 12. The light amplifier of claim 1 1 wherein the magnifier of the image size is an electronic magnifier. 13. The light amplifier of claim 1 1 wherein the magnifier of the image size is an optical zoom lens. 14. The light amplifier of claim 8 wherein the interrupter of the photon stream is a mechanical shutter. 15. The light amplifier of claim 8 wherein the interrupter of the photon stream is an electronic shutter. 16. The light amplifier of claim 8 wherein the interrupter of the photon stream is an electro-optical shutter. 1 7. A light amplifier with photoreceptor-based implanted retinal prosthetics comprising: a. an image receiver; b. a first converter of said image into electrical signals; c. an amplifier of said electrical signals; d. an overall amplification of said electrical signal according to a definite functional relationship between input signal to the amplifier and an output signal from the amplifier; e. a transformer of the image size; f. a second converter of said amplified electrical signal into a photon- based display; wherein said photons of said display enter an eye through a pupil of said eye; g. a periodic interrupter of the photon stream from said photon-based display; h. wherein a plurality of external-to-the-eye wavelengths provides light stimulation to an equal number of types, as the number of the plurality of wavelengths, of appropriately tuned photoreceptors, implanted in the eye; i. wherein at least one of said plurality of wavelengths is used to transmit light power to at least one of said plurality of photoreceptors; j. wherein at least one of said plurality of wavelengths is used to transmit information to at least one of said plurality of photoreceptors. 18. The light amplifier of claim 1 7 wherein the image receiver and the first converter of said image into electrical signals is a video camera. 19. The light amplifier of claim 17 wherein said amplifier logarithmically amplifies said electrical signal. 20. The light amplifier of claim 1 7 wherein the transformer of the image size is a magnifier of the image size. 21 . The light amplifier of claim 20 wherein the magnifier of the image size is an electronic magnifier. 22. The light amplifier of claim 20 wherein the magnifier of the image size is an optical zoom lens. 23. A light amplifier for use with photoreceptor-based implanted retinal prosthetics comprising: a. an image receiver; b. a first converter of said image into electrical signals; c. an amplifier of said electrical signals; d. an overall amplification of said electrical signal according to a definite functional relationship between input signal to the amplifier and an output signal from the amplifier; e. a transformer of the image size; f. a second converter of said amplified electrical signal into a photon- based display; wherein said photons of said display enter an eye through a pupil of said eye. 24. The light amplifier of claim 23 wherein the image receiver and the first converter of said image into electrical signals is a video camera. 25. The light amplifier of claim 23 wherein said amplifier logarithmically amplifies said electrical signal. 26. The light amplifier of claim 23 wherein the transformer of the image size is a magnifier of the image size. 27. The light amplifier of claim 26 wherein the magnifier of the image size is an electronic magnifier. 28. The light amplifier of claim 26 wherein the magnifier of the image size is an optical zoom lens. 29 The light amplifier of claim 2 oi of claim 8 or of claim 17 or of claim 23 wherein a fust coloi of light to w hich the photoreceptors are particularly sensitive is amplified more than other color components, wherein the transmission into the eye of said first color more efficientlv stimulates said photoreceptors than a color other than the first color 30 The light amplifier of claim 2 or of claim 8 or of claim 17 or of claim 23 wherein only a black-and-white contrast image is displayed, wherein the white part of that image is logaπthmically translated to the color, I e , wavelength, to which the photoreceptors are most sensitive 31 The light amplifier of claim 2 or of claim 8 or of claim 17 or of claim 23 wherein said wavelength is shifted toward or to the near infrared or toward or to the near ultraviolet, according to what optimizes the response of the implanted photosensitive elements 32 The light amplifier of claim 2 or of claim 8 or of claim 17 or of claim 23 wherein the second converter display emits directed photons which are scanned mto the eye according to a pre-determined scan pattern, onto ultimately photoreceptor- activated electrodes, which stimulate retinal cells wherein knowledge of the color of the light originating from an external scene is used to stimulate one or more living retinal cells which produces an appearance of that corresponding color 33 A method for enhancing the performance of a retinal prosthesis implanted in a patient's eye, comprising the steps of implanting an arcay of photodetectors and a plurality of electrodes for stimulating retinal nerves, mounting a light amplifier external to the eye, responding to an input image, producing an output image related to said input image by a transfer function G, positioning said light amplifier so that said output image is incident on said implanted photodetector array; having said plurality of electrodes respond to said output image incident on said photodetector array producing a sequence of negative and positive electrical pulses for application to said retinal nerves; generating successive pulses spaced in time by an interval Δt. 34. A method for making a light amplifier with photoreceptor-based implanted retinal prosthetics comprising the steps of: a. acquiring an image by camera means; b. converting of said image into electrical signals; c. amplifying said electrical signal according to a functional relationship between input signal and output signal; d. transforming the image size by transforming means; e. converting the amplified electrical signal into a photon-based display; f. said photons of said display enter an eye through a pupil of said eye; g. implanting a plurality of photoreceptor with associated electronic elements and associated electrodes; h. receiving a single light wavelength by said plurality of photoreceptors and thereby activating said photoreceptors; i. activating a plurality of electrodes with associated electronics by said plurality of activated photoreceptors; j . producing a negative pulse followed by a time delay followed by a positive pulse by said electronics; k. introducing, thereby, a net charge of zero into the eye by the produced electrical pulses. 35. The method of claim 34 further comprising the steps of a. receiving said image with a video camera and; b. converting said image into electrical signals with said video camera. 36 The method of claim 34 further comprising the step of transforming the image size by magnification 37 The method of claim 34 further compπsmg the step of amplifying said electrical signal according to a logarithmic relationship between input signal and output signal 38 The method of claim 34 further comprising the step of transforming the image size by magnifying said image size 39 The method of claim 38 further compnsmg the step of electronically magnifying the image size 40 The method of claim 38 further compπsing the step of optically magnifying the image size 41 The method of claim 38 further compnsmg the step of optically magnifying the image size utilizing an optical zoom lens. 42. A method for making a light amplifier with photoreceptor-based implanted retinal prosthetics comprising the steps of a. acquiring an image by camera means; b converting of said image into electncal signals; c. amplifying said electrical signal according to a functional relationship between input signal and output signal, d transforming the image size by transforming means, e converting the amplified electrical signal into a photon-based display, f interrupting the photon stream, periodically, from said photon-based display for periodic set amounts of time, g stimulating appropriately tuned light receivers implanted in the eye. by means of a plurality of external-to-the-eye w avelengths of light. 11 h. shining on an equal number of types, as the number of the plurality of wavelengths, of said tuned light receivers; i. producing an equal amount of negative charge by one wavelength sensitive set of photoreceptors followed by a quiescent time produced by the cutting off of light by said shutter; producing an equal amount of positive charge by another wavelength sensitive set of photoreceptors followed by a quiescent time produced by the cutting off of light by said shutter: whereby no net charge is introduced into the eye by this method; j. dividing up the net produced charge so the net charge adds up to zero for the case of more than two wavelength sensitive photoreceptors. 43. The method of claim 42 further comprising the steps of a. receiving said image with a video camera and; b. converting said image into electrical signals with said video camera. 44. The method of claim 42 further comprising the step of transforming the image size by magnification. 45. The method of claim 42 further comprising the step of amplifying said electrical signal according to a logarithmic relationship between input signal and output signal. 46. The method of claim 42 further comprising the step of transforming the image size by magnifying said image size. 47. The method of claim 46 further comprising the step of electronically magnifying the image size. 48. The method of claim 46 further comprising the step of optically magnifying the image size. 49. The method of claim 48 further comprising the step of optically magnifying the image size utilizing an optical zoom lens. 50. The method of claim 42 further comprising the step of interrupting the photon stream periodically with a mechanical shutter. 51 . The method of claim 42 further comprising the step of interrupting the photon stream periodically with an electronic shutter. 52. The method of claim 42 further comprising the step of interrupting the photon stream periodically with an electro-optic shutter. 53. A method for making a light amplifier with photoreceptor-based implanted retinal prosthetics comprising the steps of: a. acquiring an image by camera means; b. converting of said image into electrical signals; c. amplifying said electrical signal according to a functional relationship between input signal and output signal; d. transforming the image size by transforming means; e. converting the amplified electrical signal into a photon-based display; f. interrupting the photon stream, periodically, from said photon-based display for periodic set amounts of time; g. wherein a plurality of external-to-the-eye wavelengths provides light stimulation to an equal number of types, as the number of the plurality of wavelengths, of appropriately tuned photoreceptors. implanted in the eye; h. wherein at least one of said plurality of wavelengths is used to transmit light power to at least one of said plurality of photoreceptors; i. wherein at least one of said plurality of wavelengths is used to transmit information to at least one of said plurality of photoreceptors. 54. The method of claim 53 further comprising the steps of a. receiving said image with a video camera and; b. converting said image into electrical signals with said video camera. 55 The method of claim 53 further comprising the step of amplifying said electrical signal according to a logarithmic relationship between input signal and output signal 56 The method of claim 53 further comprising the step of transforming the image size by magnifying said image size 57 The method of claim 56 further comprising the step of electronically magnifying the image size 58 The method of claim 56 further comprising the step of optically magnifying the image size 59 The method of claim 58 further compnsmg the step of optically magnifying the image size utilizing an optical zoom lens 60 A method for making a light amplifier for use with photoreceptor- based implanted retinal prosthetics compnsmg the steps of a acquinng an image by camera means, b converting of said image mto electrical signals, c amplifying said electrical signal according to a functional relationship between input signal and output signal, d transforming the image size by transforming means, e converting the amplified electπcal signal into a photon-based display, said photons of said display enter an eye through a pupil of said eye, 61 The method of claim 60 further comprising the steps of a receiv ing said image with a video camera and, converting said image into electrical signals with said v ideo camera 62. The method of claim 60 further comprising the step of amplifying said electrical signal according to a logarithmic relationship between input signal and output signal. 63. The method of claim 60 further comprising the step of transforming the image size by magnifying said image size. 64. The method of claim 63 further comprising the step of electronically magnifying the image size. 65. The method of claim 63 further comprising the step of optically magnifying the image size. 66. The method of claim 64 further comprising the step of optically magnifying the image size utilizing an optical zoom lens. 67. The method of claim 34 or of claim 42 or of claim 53 or of claim 60 further comprising the steps of amplifying a first color of light to which a plurality of photoreceptors implanted in an eye is particularly sensitive, more so than other color components; transmitting said first color into the eye; stimulating more efficiently said photoreceptors than would a color other than the first color. 68. The method of claim 34 or of claim 42 or of claim 53 or of claim 60 further comprising the steps of displaying only a black-and-white contrast image; translating logarithmically the white part of that image to the color, i.e., wavelength, to which the photoreceptors are most sensitive. 69. The method of claim 34 or of claim 42 or of claim 53 or of claim 60 further comprising the steps of shifting a first wavelength toward or to the near infrared or toward or to the near ultraviolet; optimizing, thereby, the response of the implanted photosensitive elements. 70. The method of claim 34 or of claim 42 or of claim 53 or of claim 60 further comprising the steps of emitting directed photons from said photon based display; scanning said photons into the eye according to a pre-determined scan pattern; activating ultimately photoreceptor-activated electrodes by said photons; utilizing knowledge of the color of the light originating from an external scene to determine said retinal cells to be stimulated; stimulating one or more living retinal cells which give an appearance of that corresponding color. 71. A retinal prosthetic scanning laser alignment apparatus comprising a scanning laser; an imager oriented to receive an image from the eye; wherein said imager receives an image of the scanning laser beam reflected from a retinal implant; said receiver image electrically connected to a data processing unit; said data processor unit processes information of said image; wherein said data processor provides, real- time feedback information to a scanning laser control unit. 72. A retinal prosthetic scanning laser alignment apparatus comprising fiduciary marks selected from a group consisting of variably spaced points and variably spaced lines; a scanning laser; a data processing unit; a scanning laser control unit; a reflected light detector which detects light and produces a corresponding electrical signal; wherein scanning over the fiduciary marks by the scanning laser results in a reflected beam of varying brightness; wherein said reflected light detector detects said beam of varying brightness; said reflected light detector is electrically connected to said data processing unit; wherein said data processing unit controls the scanning laser control unit to scan the laser correctly. 73. A method for retinal prosthetic scanning laser alignment comprising the steps of: scanning a scanning laser over a retinal implant; imaging reflected beam from the retinal implant with an imager; processing information of said image by a data processing unit: providing real-time feedback information from the data processor unit to a scanning laser control unit; correcting the movement of the scanning laser by the scanning laser control unit. 74. A method for retinal prosthetic scanning laser alignment apparatus comprising the steps of: placing fiduciary marks selected from a group consisting of variably spaced points and variably spaced lines on the retinal implant; scanning a scanning laser over the retinal implant; detecting the reflected light with a reflected light detector; wherein scanning over the fiduciary marks by the scanning laser results in a reflected beam of varying brightness; wherein said reflected light detector detects said beam of varying brightness; producing a corresponding electrical signal from the reflected light detector; sending the electrical signal to a data processing unit; processing the electrical signal by the data processing unit; extracting the appropriate feedback correction information by processing the electrical signal; sending the feedback corcection information to the scanning laser control unit; controlling the scanning laser control unit with the correction feedback information to scan the laser corcectly across the retinal implant.

Inventors: GREENBERG ROBERT J, SCHULMAN JOSEHPH H, SEIDMAN ABRAHAM N, GREENBERG, ROBERT, J., SCHULMAN, JOSEHPH, H., SEIDMAN, ABRAHAM, N.
Applicants: GREENBERG ROBERT J, SCHULMAN JOSEHPH H, SECOND SIGHT LLC, SEIDMAN ABRAHAM N, GREENBERG, ROBERT, J., SCHULMAN, JOSEHPH, H., SECOND SIGHT, LLC, SEIDMAN, ABRAHAM, N.
Application year: 2000
Main classification: A61F
IPC codes: A61F2, A61F9, A61N1