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Eleni Papageorgiou, Gregor Hardiess, Hanspeter A. Mallot, Ulrich Schiefer; Gaze Patterns Predicting Successful Collision Avoidance In Patients With Homonymous Visual Field Defects. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3882.
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© ARVO (1962-2015); The Authors (2016-present)
(i) To identify gaze-related parameters predicting successful collision avoidance in patients with homonymous visual field defects (HVFD) under virtual reality (VR) conditions, and (ii) to compare them with those of normal subjects.
Thirty patients (age range: 19-71 yrs) with HVFD due to vascular brain lesions and 30 group-age-matched normal subjects performed a collision avoidance task in an intersection with cross traffic under VR conditions. Eye and head movements were measured with eye and head tracking systems. Performance was assessed as the number of collisions. Based on their performance, patients were assigned to either an "adequate" (HVFDA) or "inadequate" (HVFDI) subgroup by means of the median split method. Fourteen patients and 19 normal subjects were finally evaluable, after excluding participants with insufficient eye and head tracking data. Saccades, fixations, number of gaze shifts, scanpath length and the "area under the curve", defined as the area scanned by eye and head movements, were calculated. Analysis of variance with Bonferroni correction was applied for normally distributed data. The Kruskal-Wallis test was used for non-normally distributed data.
The following gaze-related parameters differed significantly between HVFDA patients (N1=5) and HVFDI patients (N2=9): (mean) number of gaze shifts (13.5 vs 9.4, p<.0001), saccadic amplitude towards the affected side (19 vs 15.6 deg, p<.0001), saccadic amplitude towards the intact side (23.2 vs 17.3 deg, p<.0001), number of fixations/sec on vehicles (3.32 vs 3.07, p=0.0029), number of straight-ahead fixations/sec (0.48 vs 0.77, p<.0001), scanpath length (1126 vs 793 deg, p<.0001) and area under the curve of the scanpath (21355 vs 16297 pixel, p<.0001). Scanpath length and number of gaze shifts were similar between HVFDA patients and normal subjects (N=19).
A subgroup of patients with HVFD sufficiently compensates for their visual deficit by exploratory gaze (eye and head) movements, becoming manifest by a higher number of gaze shifts, larger saccades, longer scanpaths and larger area under the curve, compared to HVFD subjects with impaired compensation.
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