Biomedical Engineering Reference
In-Depth Information
Prosthetic Vision Simulation in Fully
and Partially Sighted Individuals
Matthias Walter
1
, Liancheng Yang
2
and Gislin Dagnelie
2
1
Biomedical Optics and Ultrafast Lasers, Kirchhoff Institute für Physik, Ruprecht Karls
Universität
2
Department of Ophthalmology, Johns Hopkins University School of Medicine
Abstract:
This article examines performance and learning under conditions of
simulated prosthetic vision, using the tasks of counting white squares on
modified checker boards, and placing black checkers on these squares. Aim
of our study was to determine how much environmental information people
would be able to obtain from crude pictures without tactile feedback. For
this, we used video camera images which were convolved by a dedicated
computer program in real time to represent phosphene vision as future chip
implants might be able to do. The resolution was equivalent to a vision
of 20/2400. The program allowed us to vary a broad set of variables such
as contrast, number of gray levels, number of phosphenes per column and
row, etc. In our tests we used a matrix of 6
10 dots with Gaussian intensity
profile. Test subjects varied in age, gender, and educational background.
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Introduction
Human vision is mediated by one of the most highly developed sensory systems
found in nature. The capacity to combine high spatial resolution near the center
of fixation with a wide peripheral field of view, accurate depth perception,
color discrimination, and light-dark adaptation over 12 orders of magnitude is
unparalleled [1]. The information from over 100 million photoreceptor cells is
pre-processed in subsequent layers of retinal neurons, so that 1 million fibres in
the optic nerve are sufficient to transport the information to the visual cortex,
where further information processing takes place.
The most common causes of adult visual impairment in North America
and Western Europe include age-related macula degeneration (AMD), retinitis
pigmentosa (RP), and diabetic retinopathy. AMD is caused by a combination of
genetics and environmental and other individual factors, and is characterized by
progressive loss of central vision. Six million Americans are affected, and it is
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