EOGSTUDIO
A Software Platform for Processing Electrooculography Recordings
R. A. Becerra-García
1
, R. V. García
1
, F. Rojas
2
, J. González
2
, B. San Román
2
and L. Velázquez
3
1
University of Holguín “Oscar Lucero Moya”, Holguín, Cuba
2
University of Granada, Granada, Spain
3
Center for the Research and Rehabilitation of Hereditary Ataxias, Holguín, Cuba
Keywords: Biomedical engineering, Medical applications, Electrooculography, Computational neuroscience, Computer
aided diagnosis.
Abstract: Analysis of saccadic eye movements is a fundamental task for the study of different neurological disorders.
The Center of Research and Rehabilitation of Hereditary Ataxias (CIRAH) located in Holguín, Cuba; uses
this technique in order to study the evolution of many different ataxias. Nevertheless, current available
software applications do not fill the requirements needed by the CIRAH’s staff to complete their processing
protocol, as they do not run in modern operating systems or are poorly usable. EogStudio was created with
the objective of filling the gap left by these applications. It is signal processing platform based on extensible
plugins that meet the requirements made by CIRAH’s researchers. For the processing and determination of
the significative points of the saccadic eye movements, soft computing techniques, such as independent
component analysis, were applied.
1 INTRODUCTION
The study of eye movements has been proved to be a
useful tool to diagnose and evaluate the patient
condition in many neurological disorders. In
particular, saccadic tests for clinical proposals are
usually applied in researches related to several
diseases, like ataxia, Parkinson, schizophrenia,
amongst many others (Jones and DeJong, 1971);
(Rivaud-Pechoux et al., 1998); (Schulze et al.,
2006).
Available embedded software in dedicated
equipment that records and analyzes eye
movements, behaves as a 'black box', since
manufacturers do not usually give information
related to the algorithms and mathematical methods
involved in the computing of variables concerning
the evaluation of the eye movements. Furthermore,
these systems in general terms lack of the necessary
extensibility, and very often the reports do not
accomplish the researchers’ requirements.
In this work, a software developed in the
University of Holguin, in Cuba, named EogStudio,
is described, together with its algorithms for saccade
detection and characterization.
All the experiments were carried out by the
medical staff of CIRAH. Each patient was placed in
a chair, with a head fixation device to avoid head
movements, the variables were collected by a two
channel electronystagmograph (Otoscreen, Jaeger-
Toennies, D-97204 Höchberg, Germany). Recording
conditions were set as follows: electrodes of silver
chloride placed in the external borders of right eye
(active electrode) and left eye (reference electrode),
high pass filtering 0.002 Hz, low pass filtering 20
Hz, sensitivity 200 µV/division, and sampling
frequency 200 Hz. For stimulus generation a black
screen CRT display showing a white circular target
with an angular size of 0.7º was used. The stimulus
and patient response data are automatically stored in
ASCII files by Otoscreen electronystagmograph.
This software reads the saccadic records from the
files generated by the electronystagmograph and
computes a set of significant variables, in order to
study neurological disorders. A main goal of the
developers of this software was the potential for
extension and upgrading adapting to researchers’
requirements. This goals was achieved through the
use of a plugin-based architecture model.
The software is intended for ataxia SCA-2
computer-aided diagnosis. SCA-2 is a disease that
347
A. Becerra-García R., V. García R., Rojas F., González J., San Román B. and Velázquez L..
EOGSTUDIO - A Software Platform for Processing Electrooculography Recordings.
DOI: 10.5220/0003678203470350
In Proceedings of the International Conference on Neural Computation Theory and Applications (NCTA-2011), pages 347-350
ISBN: 978-989-8425-84-3
Copyright
c
2011 SCITEPRESS (Science and Technology Publications, Lda.)
presents the international highest levels of
prevalence in Holguín, Cuba, where the Center of
Research and Rehabilitation of Hereditary Ataxias
(CIRAH for its Spanish acronym) is entirely
dedicated to study and treat this disease (García
Bermúdez, 2007, Velázquez-Pérez, 2001).
Medical staff of CIRAH contributed in the
process of selecting the variables to be studied,
collecting patient records and validating tests to the
software. CIRAH has been also the main user of the
software, which has been used in this centre in the
last two years.
2 DESIGN
Although there is some available software for
performing some of the tasks for which EogStudio is
intended, these programs are generally old and very
specific for the machine where they get the data
from. For instance, the equipment used at CIRAH to
make EOG recordings is the Otoscreen
electronystagmograph, which provides its own
software designed to run on machines with MS-
Windows 95 operating system. This software makes
very difficult to do certain tasks like saccadic point
editing and its usability is poor when running in
modern operating systems.
More modern software packages like EyeLink
Matlab Toolbox (Cornelissen and Peters, 2002) or
ILab (Gitelman, 2002) depends on other frameworks
like Matlab and are focused in a very specialized
audience.
The main intention of EogStudio is providing
medical staff with less computing background with a
tool were they are capable to manage and edit data
from EOG recordings as if they were using an office
suite application like Writer, Calc or MS-Word.
Thereby, the development team focuses in creating a
desktop application that helps users to detect
saccades automatically and to make corrections on
these data in a fast and easy way.
Other non-functional but not less important
requirements was that the software application must
be fast and run in all major platforms nowadays like
MS-Windows, Mac OS X and GNU/Linux. For this
requirement, the use of Qt Toolkit Libraries and the
C++ programming language was necessary.
EogStudio was created to be extensible through
plugins in order to support various file formats,
reports and processing algorithms. Its structure is
based on several libraries and plugins which separate
and organize the functionalities. Figure 1 illustrates
the overall system design.
3 WORKFLOW
EogStudio is centered in studies, where a study is
the document where all signals data and events are
stored.
The workflow steps to use EogStudio are
straightforward, and they can be split in the four
following steps:
1. Create a study from an existing recording like
Otoscreen CSV files.
Figure 1: EogStudio components design and dependencies.
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348
2. Detect saccades using the automatic saccade
detector.
3. Correct saccadic points using the saccadic editor.
4. Report study saccadic results for further analysis.
The first step consists of creating an study starting
from a recording file from Otoscreen or other
supported equipment. In the application, this stage
comprises a wizard that guides the user through the
process. After this, the study will be opened and the
application will show the saccade editor for the first
test.
The second step of this process allows us to get
an initial approximation of the saccades present in
the study. A detection algorithm proposed by
(García Bermúdez, 2007) was used to fulfill this
task.
The algorithm for saccade detection works as
follows:
1. Locate the stimulus transition points.
2. Find the middle point of each saccade.
3. Determine the start and end point of each
saccade.
The algorithm uses local polynomials to adjust the
saccade start and end points according to Equation 1.
(1)
Where ܶ
ௌ௧௔௥௧
and ܶ
ா௡ௗ
are the saccade start and end
points, respectively; and ܶ
ெ௔௫ௌ௔௖
is the maximum
duration of a saccade.
Once we have the first approximation of saccadic
points, we proceed to fix the saccades whose points
were not set well in the signal using a simple visual
editor provided in the application with facilities for
adding, removing and editing saccadic points
(Figure 2).
Figure 2: Saccades editor.
Once all saccades were corrected, study reports
can be generated to different formats like: tabulated
text (csv), Hypertext Markup Language (html) and
Open Document Format (odf). This report contains
all relevant data that the medical team may use for
their studies.
4 APPLICATION EXTENSION
THROUGH PLUGINS
Nowadays, software applications must include an
easy extension mechanism in order to simplify the
task of adding new functionalities. As it was shown
in the design section, EogStudio was built using a
plug-in based architecture, which facilitates the
previously mentioned task.
This architecture enables independency between
the application author and third parties developers.
The application provides four types of plugins
(Figure 3):
File Format Plugins: This module allows the
support of new type of equipment and storage
formats.
Report Format Plugins: It provides a simple
interface which supports new report presentation
formats.
Report Plugins: It brings the possibility of creating
new reports and not only the default formats
provided by the application.
Processing Plugins: It gives the chance to
implement new processing algorithms, for instance
detect other ocular events and not only saccades.
Figure 3: Installed plugins dialog window.
It is planned to release a Software Development
Kit (SDK) which facilitates the work of developers
who wants to extend the application. This kit would
consist of a set of well documented libraries used in
the development of EogStudio, and a set of plugins
T
Start
T
MiddlePoint
T
MaxSac
2
T
End
T
MiddlePoint
T
MaxSac
2
EOGSTUDIO - A Software Platform for Processing Electrooculography Recordings
349
for QtCreator, which it is the integrated development
environment (IDE) that was used to create the
application.
5 CONCLUSIONS
EogStudy has already been used at CIRAH for more
than one year, processing hundreds of records of
sick and control subjects in several drug clinical
experiments performed during this period. It was
also used in order to follow the evolution of many
patients.
This tool was conceived having in mind the
current status of neurophysiology, in relation with
characterization and evaluation of saccadic eye
movements, and it was adapted to fit CIRAH’s
requirements.
EogStudio answered the expectations and needs
of CIRAH’s researchers and it also can be used in
other medical institutions with similar needs due to
its plugin-based architecture model which facilitates
the extension and adaptation of the application.
ACKNOWLEDGEMENTS
This work has been supported by the Genil Start-up
Project for Young Researchers (http://genil.ugr.es)
“Processing and Classification of Electro-
oculography (EOG) Data for Ataxia SCA-2
Diagnosis” (PYR-2010-23) from the CEI BioTIC
GENIL (CEB09-0010) of the CEI Program from the
MICINN.
The authors would like to thank the rest of the
personnel in the Centre for the Research and
Rehabilitation of Hereditary Ataxias “Carlos J.
Finlay”, Holguín, (Cuba) for their support and
collaboration.
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