Audiovisual perception in adults with amblyopia: a study using the McGurk effect.

Purpose: The effects on multisensory integration have rarely been examined in amblyopia. The McGurk effect is a well-established audiovisual illusion that is manifested when an auditory phoneme is presented concurrently with an incongruent visual phoneme. Visually healthy viewers will hear a phoneme that does not match the actual auditory stimulus, having been perceptually influenced by the visual phoneme. This study examines audiovisual integration in adults with amblyopia.

Methods: Twenty-two subjects with amblyopia and 25 visually healthy controls participated. Participants viewed videos of combinations of visual and auditory phonemes, and were asked to report what they heard. Some videos had congruent video and audio (control), whereas others had incongruent video and audio (McGurk). The McGurk effect is strongest when the visual phoneme dominates over the audio phoneme, resulting in low auditory accuracy on the task.

Results: Adults with amblyopia demonstrated a weaker McGurk effect than visually healthy controls (P = 0.01). The difference was greatest when viewing monocularly with the amblyopic eye, and it was also evident when viewing binocularly or monocularly with the fellow eye. No correlations were found between the strength of the McGurk effect and either visual acuity or stereoacuity in subjects with amblyopia. Subjects with amblyopia and controls showed a similar response pattern to different speakers and syllables, and subjects with amblyopia consistently demonstrated a weaker effect than controls.

Conclusions: Abnormal visual experience early in life can have negative consequences for audiovisual integration that persists into adulthood in people with amblyopia.