MEMS restoring sight to the blind

by R. Colin Johnson
Contributing Editor, MEMS Investor Journal

Over a decade has passed since hope was raised worldwide that MEMS could make blindness a curable condition.  Now the long wait is finally over, with all the necessary tests and clinical trials clearing the final hurdles.  Last month, the U.S. Food and Drug Administration (FDA) approved the final clinical trials for the Argus II retina developed by the Department of Energy's (DoE)  Artificial Retina Project, based on the pioneering work of Mark Humayun at the Doheny Eye Institute of the University of Southern California and Second Sight Medical Products, Inc.  Also this month, a second and simpler implant, called the "Implantable Telescope" by its maker, VisionCare Corp., received final FDA approval, making millions of legally blind worldwide eligible for the sight-restoring implant.

Each artificial retina wafer created in the cleanroom at Lawrence Livermore National Laboratory (Calif.) holds a dozen MEMS electrode arrays which will be implanted into as many patient's eyes.

Artificial retina team member Terri Delima at Lawrence Livermore National Laboratory (Calif.) holds a thin film artificial retina and its attached MEMS electrode array.

Currently, over 50 patients worldwide already have either an earlier model Argus, or will soon have the latest 60-pixel Argus II retina implant in place.  The 60-pixel Argus II is the successor to the first generation 16-pixel retina that merely proved the concept of retinal implants as a cure for blindness.  The current 60-pixel Argus II enables patients to recognize doorways and windows as well as the edges in the environment that assist in everyday navigation.  The next generation 200-pixel Argus III, due by 2012, will likely restore the ability to read, and the final goal of a 1000-pixel Argus retina will restore to patients most of the abilities of normal sight. 
Sandia National Labs developed this MEMS application-specific integrated circuit (ASIC) for advanced artificial retinas by selectively etching away parts of the silicon chip to allow wiring of the electrical connections to pass through it.

Both the Argus and Telescope implants are aimed at curing blindness in patients suffering from macular degeneration, and similar conditions, wherein the electrical wiring to the brain is still intact, but where some of the retinal cells that sense the light and convert it into an electrical signal have stopped working – usually in a spreading central "blind spot".  The approaches taken by the two implants, however, are very different.

The implantable telescope is housed in a prosthetic device composed of three primary components: a fused quartz glass capsule that contains wide-angle micro-optical elements; a clear polymethylmethacrylate (PMMA) carrier; and a blue PMMA light restrictor. The sealed optical component is snap-fitted into the carrier plate.

A long-road approach was taken by the DoE researchers, who have enlisted the help of six national labs to perfect all of the complicated MEMS components required to make the system work.  The DoE implant uses a MEMS electrode array technology that receives signals on an attached antenna and then stimulates the nerve cells that send information to the brain.  Signals originate on a video camera mounted on a pair of eye glasses which is transmitted by radio frequencies (RF) to the antenna.

The DoE's Argus III will be ready soon -- the thin-film electrode array has already been fabricated and initial functional tests verify that the wireless power and data channels are operational.  The 200-pixel artificial retina will be ready for implantation in patients by the end of 2010.

The telephoto ocular prosthesis is about the size of a pea (3.6 mm diameter; 4.4 mm length) and is surgically placed inside the eye to render a magnified image on the remaining good retina cells of millions of legally blind Americans.

The just approved "Telescope" implant at VisionCare, on the other hand, took the short-road to FDA approval, since it contains no electrical circuitry.  The purely mechanical implant, invented by Isaac Liphitz, houses a 2.5-magnification telephoto lens measuring just 3.6-by-4.4 millimeter swhich is surgically implanted in the eye's capsular bag after its original lens is removed.  The telescope is contained inside a fused quartz glass capsule with micro optical elements made from polymethylmethacrylate (PMMA).  The telescope is aimed at the remaining working retinal cells thereby sidestepping the "blind spot" created by macular degeneration.

Copyright 2010 MEMS Investor Journal