EOGSTUDIO

A Software Platform for Processing Electrooculography Recordings

R. A. Becerra-García

, R. V. García

, F. Rojas

, J. González

, B. San Román

and L. Velázquez

University of Holguín “Oscar Lucero Moya”, Holguín, Cuba

University of Granada, Granada, Spain

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

 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

Start

MiddlePoint

MaxSac

End

MiddlePoint

MaxSac

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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