Punita Christopher, Fred K Chen, Varalakshmi Wuyyuru, Jose Sahel, The Argus II epiretinal prosthesis system allows letter and word reading and long-term function in patients with profound vision loss Lyndon da Cruz, Brian F Coley, Jessy Dorn, Francesco Merlini, Eugene Filley, Punita Christopher, Fred K Chen, Varalakshmi Wuyyuru, Jose Sahel, Paulo Stanga, Mark Humayun, Robert J Greenberg, Gislin Dagnelie, for the Argus II Study Group The Argus II epiretinal prosthesis system allows letter and word reading and long-term function in patients with profound vision loss Lyndon da Cruz,1 Brian F Coley,2 Jessy Dorn,3 Francesco Merlini,2 Eugene Filley,4 Punita Christopher,3 Fred K Chen,1,5 Varalakshmi Wuyyuru,3 Jose Sahel,6 Paulo Stanga,7 Mark Humayun,3,8 Robert J Greenberg,3 Gislin Dagnelie,9 for the Argus II Study Group Br J Ophthalmol 2013;0:1–5. doi

Overview Clinical Problem : RP Overview of Retinal Prosthesis Argus II Basic Design and function Aim Methods Results Discussion Challenges/Limitations Conclusion Questions

Retinitis Pigmentosa Retinitis pigmentosa is a condition that can be caused by a myriad of different gene defects (about 90 for isolated RP and RP that occurs in syndromes), with different ways of inheritance (20% autosomal-dominant [50% of children of parents who carry the defect will get RP], 20% autosomal-recessive [25% of carrying parents], 10% x-linked [mothers pass it on to sons only], and 50% spontaneous without family inheritance). It affects about one in 4000 humans, and about one in 100 are carriers. Some syndromes show RP together with other symptoms, most often hearing loss. What happens in a nutshell is that dark pigments are deposited in the retina, mostly in the area of the rods, which die off by apoptosis, so the earliest symptoms tend to be increasing loss of night vision, and the development of tunnel vision. Here’s an image of a normal retina, and one with retinitis pigmentosa :

Retinal Prosthesis History Charles LeRoy in 1755 discharged a large capacitor through the head of a blind person, who described “flames descending downwards” (Marg, 1991)

Retinal Prosthesis Concept

Retinal Prosthesis Options Argus II Visual Cortical Implant Virtual Retinal Display (VRD) Microsystem-based Visual Prosthesis (MIVIP) Artificial Silicon Retina (ASR) Tübingen MPDA Project Alpha IMS Implantable Miniature Telescope Dobelle Eye

The external equipment The external equipment includes glasses, a video processing unit (VPU) and a cable.

How Is Argus® II Designed To Produce Sight?

Testimonials The F.D.A. Approves a Bionic Eye: Argus II Device Helps the Blind – YouTube Argus II, Manchester User Testimonial - Artificial Retina - Bionic Eye - YouTube

Aim To determine whether a group of patients blinded by outer retinal dystrophies and fitted with the Argus II system, could identify letters and words on a computer screen. (effective spatial resolution, in the context of a device that is stable, portable and capable of long-term function)

Subjects

Methods Test I: letter identification Test II: letter size reduction Test III: word recognition Conditions : System off and both eyes unpatched; system on in ‘scrambled’ mode with eyes patched and unpatched; and system in standard mode with eyes patched and unpatched

Results

Figure 2 Figure 2 Box and whisker graphs illustrating the median percentage correct and quartiles for Test I letter Groups A, B and C comparing the device on and off. For Groups A, B and C, n=21, 19 and 20, respectively. (** <0.001 Wilcoxon signed rank test). Outliers, shown as black dots, are data with values beyond the ends of the whiskers.

Figure 3 Figure 3 A graph showing the mean and SEs of the total number of letters identified correctly in two test runs of letter size reduction using the Argus II retinal prosthesis system. (*p<0.05).

Challenges Safety Surgery Effectiveness Suitability Cost Contraindications Electrodes packaging

Conclusion Multiple blind subjects fitted with the Argus II system consistently identified letters and words using the device, indicating reproducible spatial resolution. This, in combination with stable, long-term function, represents significant progress in the evolution of artificial sight.

Questions What is Argus II ? What are advantages of Argus II? Argus II has therapeutic potential for what other types of retinal diseases? Argus II vs. other Retinal Prosthesis What experiments would you suggests to further test effectiveness of Argus II?