The use of Argus® II retinal prosthesis by blind subjects to achieve localisation and prehension of objects in 3-dimensional space

• Published in: Graefe's archive for clinical and experimental ophthalmology Vol. 253; no. 11; pp. 1907 - 1914
• Main Authors: Luo, Yvonne Hsu-Lin, Zhong, Joe Jianjiang, da Cruz, Lyndon
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-11-2015; Springer Nature B.V
• Subjects: Aged; Blindness - physiopathology; Blindness - rehabilitation; Female; Humans; Imaging, Three-Dimensional; Male; Medicine; Medicine & Public Health; Middle Aged; Ophthalmology; Pattern Recognition, Visual - physiology; Proprioception - physiology; Prospective Studies; Prosthesis Implantation; Psychomotor Performance - physiology; Psychophysiology; Retina - physiopathology; Retinal Disorders; Retinitis Pigmentosa - physiopathology; Retinitis Pigmentosa - rehabilitation; Visual Prosthesis; Retinal prosthesis; Psychophysical testing; Retinitis pigmentosa; Outer retinal degeneration; Artificial retina
• ISSN: 0721-832X; 1435-702X
• DOI: 10.1007/s00417-014-2912-z

Background
The Argus® II retinal prosthesis system has entered mainstream treatment for patients blind from Retinitis Pigmentosa (RP). We set out to evaluate the use of this system by blind subjects to achieve object localisation and prehension in 3-dimensional space.
Methods
This is a single-centre, prospective, internally-controlled case series involving 5 blind RP subjects who received the Argus® II implant. The subjects were instructed to visually locate, reach and grasp (i.e. prehension) a small white cuboid object placed at random locations on a black worktop. A flashing LED beacon was attached to the reaching index finger (as a finger marker) to assess the effect of enhanced finger visualisation on performance. Tasks were performed with the prosthesis switched “on” or “off” and with the finger marker switched “on” or “off”. Forty-eight trials were performed per subject. Trajectory of each subject’s hand movement during the task was recorded by a 3D motion-capture unit (Qualysis®, see
supplementary video
) and analysed using a MATLAB script.
Result
Percentage of successful prehension±standard deviation was: 71.3 ± 27.1 % with prosthesis on and finger marker on; 77.5 ± 24.5 % with prosthesis on and finger marker off; 0.0 ± 0.0 % with prosthesis off and finger marker on, and 0.00 ± 0.00 % with prosthesis off and finger marker off. The finger marker did not have a significant effect on performance (
P =
 0.546 and 1, Wilcoxon Signed Rank test, with prosthesis on and off respectively). With prosthesis off, none of the subjects were able to visually locate the target object and no initiation of prehension was attempted. With prosthesis on, prehension was initiated on 82.5 % (range 59–100 %) of the trials with 89.0 % (range 66.7–100 %) achieving successful prehension.
Conclusion
Argus® II subjects were able to achieve object localisation and prehension better with their prosthesis switched on than off.