Eye movements and psychophysics in patients with phoria by Mr. Bernhard Blum given during the 15th Congress of the European Federation of Neurological Societies powered by - MULTIWEBCAST

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Introduction:
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.

Objectives:
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.

Results:
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.

Conclusions:
Already in normals visual acuity is significantly deteriorated after asymmertrical saccades. Comparison to patient data will be presented on the poster.

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