Objectives The aim was to quantify oculomotor performance in hemianopic patients and in healthy controls during saccadic and fixation tasks, and to detect potential spontaneous adaptive mechanisms in the patients.
Methods Eye movements were recorded in 33 hemianopic patients (15 right, 18 left, disease duration 0.2-29 years) and 14 healthy subjects by Scanning Laser Ophthalmoscope allowing determination of the absolute fovea position relative to the stimulus without calibration. Landing accuracy of saccades was determined for 5° saccades, indicated by the number of dysmetric saccades (DS), and fixation stability (FS) after landing. Furthermore, during continuous fixation of a central cross, FS and distribution of fixational eye movements (FEM) were measured. Size of macular sparing was determined using custom microperimetry software (stimulus grid 0.5°).
Results Landing accuracy was decreased, indicated by significantly more DS (hypo- and hypermetric) to the blind side compared with the seeing side. Their number was more increased in macular sparing <4°. DS were not correlated with age and disease duration.. FS after landing was lower after saccades to the blind side. Distribution of FEM during continuous fixation was asymmetrically shifted to the blind side, especially in macular sparing <4°.
Conclusions Number of DS was not correlated with disease duration indicating insufficient spontaneous long-term adaptation. Increased number of DS and decreased FS after landing in patients with small or absent macular sparing stresses the importance of intact parafoveal vision. Asymmetric FEM during continuous fixation indicate an advantageous adaptive mechanism to shift the visual field border towards the hemianopic side.