June 2015
Volume 56, Issue 7
Free
ARVO Annual Meeting Abstract  |   June 2015
Study of fusional convergence using eye tracking: preliminary results on subjects with normal binocular vision
Author Affiliations & Notes
  • Michela Fresina
    DIMES, Ophthalmology Service, Bologna, Italy
  • Laura Cercenelli
    DIMES, Laboratory of Bioengineering, Bologna, Italy
  • Cecilia Benedetti
    DIMES, Ophthalmology Service, Bologna, Italy
  • Emilio C Campos
    DIMES, Ophthalmology Service, Bologna, Italy
  • Barbara Bortolani
    DIMES, Laboratory of Bioengineering, Bologna, Italy
  • Brunella Merante
    DIMES, Laboratory of Bioengineering, Bologna, Italy
  • Piera Versura
    DIMES, Ophthalmology Service, Bologna, Italy
  • Emanuela Marcelli
    DIMES, Laboratory of Bioengineering, Bologna, Italy
  • Footnotes
    Commercial Relationships Michela Fresina, None; Laura Cercenelli, None; Cecilia Benedetti, None; Emilio Campos, None; Barbara Bortolani, None; Brunella Merante, None; Piera Versura, None; Emanuela Marcelli, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science June 2015, Vol.56, 2917. doi:
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      Michela Fresina, Laura Cercenelli, Cecilia Benedetti, Emilio C Campos, Barbara Bortolani, Brunella Merante, Piera Versura, Emanuela Marcelli; Study of fusional convergence using eye tracking: preliminary results on subjects with normal binocular vision. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2917.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract 
 
Purpose
 

In the field of ophthalmology, vision researchers use eye tracking to study oculomotor behavior, cognitive visual function and vision deficiencies. Fusional vergence is a disjunctive movement of the eyes that is made in order to obtain single vision with two eyes. Fusional vergence disorders are often associated with the most common forms of strabismus. The aim of the study was to characterize fusional convergence response in subjects with normal binocular viewing by using an eye tracking system.

 
Methods
 

Base-out horizontal prisms of 4 and 6 diopters were used to elicit fusional convergence of the right eye in 11 subjects with normal binocular vision. Eye movements were continuously recorded using the Viewpoint infrared video eye tracker (Arrington Research, Scottsdale, AZ, USA) and custom software was developed to automatically analyze off-line the saccadic response (gaze angle and angular velocity). The Fusional Convergence Amplitude (FCA) was calculated by subtracting the baseline position of the right eye (i.e. before the introduction of the prism) from the maximum saccadic excursion of the right eye during the disconjugate eye movements in the vergence phase (Figure 1.a).

 
Results
 

The typical eye-movement response in subjects achieving the fusional convergence was a preliminary saccadic movement of both eyes (version phase) followed by a convergence movement with the eyes moving towards each other to achieve single vision (vergence phase) (Figure 1). Eye tracking recordings showed that 2 patients were not able to achieve fusion with neither 4 nor 6 diopters prisms. Fusion was achieved in 8 subjects when using the 4 diopters prism and only in 6 subjects when using 6 diopters prism. One patient was excluded from the analysis because the saccadic movements were highly affected by blink artifacts. The FCA varied from 2.2°±0.2 to 3.0°±0.2 when increasing prism diopters from 4 to 6 (Figure 2).

 
Conclusions
 

The fusional convergence can be accurately studied and evaluated using an eye tracking system. Preliminary results on subjects with normal vision showed that when increasing the prism diopters the fusional convergence ability decreases.  

 

 
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