Eye movements and psychophysics in patients with phoria
Mr. Bernhard Blum
Disclosure : This project was supported by funds from the German Federal Ministry of Education and Research under the Grant code 01 EO 0901.
The authors bear full responsibility for the content of this publication.
10 slide(s) – English – 2011-09-10
Phoria, a latent misalignment of the eyes, is common in unselected populations. If decompensated it often results in symptoms of asthenopia: headache, dizziness and fatigue. It is still not understood why such decompensation of phoria occurs.
To investigate the specific challenges phoria induces for binocular saccadic coordination we recorded asymmetrical saccades in subjects with (de-)compensated phorias and compared saccades and stability of fixations to age-matched normals. Furthermore we measured visual acuity to estimate possible consequences of post-saccadic binocular misalignment on visual processing.
Material and methods:
Eye movements were recorded using the EyeSeeCam video-oculography system in darkness. Baseline visual acuity was determined in a forced choice task by optotypes (Landolt C) that flashed for 100 ms on a central screen at 4 m distance. In the saccade paradigm subjects then performed asymmetrical saccades between two lateral near-targets (50 cm distance, 10° left/right) and the screen. Post-saccadic visual acuity was measured by optotypes that flashed on screen immediately after saccades.
Experiment recordings in 10 normal adult subjects (7 male, 3 female, 30 +/- 7.75 years) showed significant differences (ttest: p < 0.001) between visual acuity at baseline (mean +/- sd: 1.90\' +0.29\'/-0.25\') and post-saccadic acuity (8.19\' +2.73\'/-2.05\'). Vergence movements clearly continued during post-saccadic optotype presentation: With velocities of 13 +/- 5.16°/s the eyes diverged from 2.5 +/- 1.42° vergence at optotype onset to 1.21 +/- 1.18° at offset.
Already in normals visual acuity is significantly deteriorated after asymmertrical saccades. Comparison to patient data will be presented on the poster.