Compensatory saccades in head impulse testing influence the dynamic visual acuity of patients with unilateral peripheral vestibulopathy1.
Both the dynamic visual acuity (DVA) test and the video head-impulse test (vHIT) are fast and simple ways to assess peripheral vestibulopathy. After losing peripheral vestibular function, some patients show better DVA performance than others, suggesting good compensatory mechanisms. It seems possible that compensatory covert saccades could be responsible for improved DVA.



To investigate VOR gain and compensatory saccades with vHIT and compare them to the DVA of patients with unilateral peripheral vestibulopathy.



VOR gain deficit and compensatory saccades were measured with vHIT. VOR gain was calculated for each trial as mean eye velocity divided by mean head velocity during 4 samples between 24 ms - 40 ms after peak head acceleration. DVA was then assessed. VHIT was analyzed for percentage of covert saccades and for cumulative overt saccade amplitude. Twenty-four patients with unilateral vestibular deficit were included. A control group of 113 healthy subjects provided normal data.



On the affected side, pathologic values for DVA (mean 0.83 logMAR±0.25 SD) and VOR gain (mean 0.16±0.13) were obtained, whereas the healthy side showed normal values (0.53 logMAR±0.15 for DVA and 0.89±0.18 for VOR gain). Yet, DVA performance on the affected side was significantly better in patients with higher covert saccade percentage (p = 0.012) and lower cumulative overt saccade amplitude (p < 0.001).



Compensatory covert saccades seen in vHIT correlate with improved performance of DVA-testing in patients with unilateral peripheral vestibular loss. Hence, in addition to testing peripheral vestibulopathy, our results indicate a way for assessing rehabilitatory compensation in such patients by DVA in addition to vHIT.
Department of Otorhinolaryngology, Head & Neck Surgery, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
V G
VG
Wettstein
Departments of Neurology and Ophthalmology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
K P
KP
Weber
Departments of Neurology, Ophthamology, and Otorhinolaryngology, Head & Neck Surgery, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
C J
CJ
Bockisch
Department of Otorhinolaryngology and Head & Neck Surgery, University Hospital Zurich, University of Zurich, Zurich Center for Integrative Human Physiology (ZIHP), Switzerland.
S C
SC
Hegemann
D000054:Acceleration; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D005133:Eye Movements; D005260:Female; D007839:Functional Laterality; D064087:Head Impulse Test; D006801:Humans; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000601:surgery; D011183:Postoperative Complications / Q000503:physiopathology; D012027:Reflex, Vestibulo-Ocular; D012438:Saccades; D015837:Vestibular Diseases / Q000175:diagnosis* / Q000503:physiopathology*; D014792:Visual Acuity; D055815:Young Adult
Vestibulopathy; compensatory saccades; dynamic visual acuity; head impulse test