The use of Argus® II Retinal Prosthesis to Identify Common Objects in Blind Subjects with Outer Retinal Dystrophies

Abstract

 

Purpose

 

To determine the usefulness of the Argus® II Retinal Prosthesis in assisting blind subjects (from outer retinal dystrophies) to identify a range of common real-life objects.

 

Methods

 

Eight subjects with light perception vision received the Argus® II implant. Internally controlled, closed-set, forced-choice tests on identification of eight common objects (as chosen by the subjects) were performed. The objects were first presented in the solid form (see Figure 1), then in the outlined form (see Figure 2). The tests were performed with the Argus® II device set in one of the 3 conditions: a) device on (standard mode), b) device in "scrambled” mode (positive control); and c) device off (negative control).

 

Results

 

For Solid Objects, the mean % of correct identification ± S.D: 1. Device on = 32.8 ± 15.7% 2. Device in "scrambled mode" = 26.2 ± 12.5% 3. Device off = 12.5 ± 6.7% (P = 0.02, Friedman Test) For Outlined Objects, the mean % of correct identification ± S.D: 1. Device on = 41.4 ± 17.7% 2. Device in "scrambled mode" = 20.7 ± 12.4% 3. Device off = 9.4 ± 7.5% (P = 0.005, Friedman Test) The mean % of correct identification of device on versus device in “scrambled mode” was only significant for Outlined Objects, but not for Solid Objects. (P = 0.002 and 0.193 respectively, Wilcoxon Signed Rank Test)

 

Conclusions

 

The Argus® II system allowed blind subjects to identify common real-life objects more accurately with the device on than off. This accuracy could be improved by enhancing the outlines of the objects. This finding has practical implications in terms of modifying the subjects’ environment, and allowing future development in image processing to maximize the subjects’ performance with the device.

 

 

Figure 1: Eight solid objects (as chosen by the study subjects) were presented on a black felt surface for object recognition testing.

 

 

Figure 2: These 8 objects were partially covered by black cardboard cut-outs to give them well-delineated outlines (i.e. Outlined Objects). They were then presented again to the subjects for object recognition testing.

 

Keywords: 689 retina: distal (photoreceptors, horizontal cells, bipolar cells) • 762 vitreoretinal surgery • 753 vision and action