Ocular vestibular evoked myogenic potentials in different types of amblyopia.

Clinical Relevance: The visual system plays an important role in the development of the vestibular-ocular reflex (VOR). In clinical practice, the ocular vestibular evoked myogenic potential (oVEMP) test is used to assess contralateral VOR.
Background: This study sought to compare the oVEMP in patients with anisometropic, strabismic, and mixed amblyopia using unilateral and bilateral (simultaneous binaural) stimulation.
Methods: Forty-two amblyopic patients (20 males and 22 females) with a mean age of 10.48 ± 4.00 years (range: 5 - 20 years) were examined. The Titmus stereopsis test, alternate cover test, and best-corrected visual acuity were evaluated. Patients were divided into three groups: anisometropic, strabismic, and mixed amblyopia. The oVEMP responses including the amplitude of electrical activity (n1-p1 complex) and the latencies (n1 and p1) of the VOR responses were recorded under unilateral and bilateral stimulations.
Results: In the anisometropic and strabismic group, n1 latency was significantly faster in the non-amblyopic eyes compared to amblyopic eyes (Z = -2.04, p  = 0.042, andZ = -2.54, p  = 0.024 respectively). Mean p1 latency was significantly faster in the non-amblyopic eyes compared to the amblyopic eyes of the strabismic group (Z = -2.31, p  = 0.011)In all groups, the p1 latency was faster in the non-amblyopic eye compared to bilateral stimulation (all, p  < 0.05). In all groups, the n1-p1 amplitude was not significantly different between the two eyes, and between each eye and bilateral stimulation (all, p  > 0.05). No significant correlation was found between the depth of amblyopia and n1 and p1 responses (all, p  > 0.05). In all groups there was no significant difference in the latency of n1 and p1 between the amblyopic eye and bilateral stimulation (all, p  > 0.05).
Conclusion: Regardless of its type, amblyopia affects vestibular-ocular reflex responses. Further research is warranted to clarify the effect of the disease and its treatment on the ocular-vestibular system.