Determining the ideal optotype size for pitch plane interventions: an exploratory study (Preprint)

BACKGROUND Clinicians prescribe vestibulo-ocular reflex (VOR) exercises when there is a deficit in gaze stability associated with vestibular hypofunction. The exercises aim to maintain focus on an object while the head is moving in the pitch and yaw planes. Many people who complete VOR exercises use progressive or bifocal lens. For multi-focal corrective lenses, the user must look through the correct part of their lens when viewing targets in the pitch plane. OBJECTIVE This study aimed to identify if healthy multi-focal corrective lens users had difficulty with VOR exercises in the pitch plane based on optotype size. METHODS Participants completed VOR exercises on the VestAid tablet, which can record both eye gaze compliance and head movement compliance. Participants completed pitch plane VOR exercises at 80 bpm with optotype sizes 14-, 16-, 18-, 20-, and 22-point fonts for 30 seconds in the seated position with no visual background. All participants then rated symptom severity (dizziness, nausea, headache, fogginess) and overall level of exercise difficulty. RESULTS Twelve healthy multi-focal correct lens users (seven progressive and three bifocal lens users) completed the study. All participants were 100% compliant with moving their head at the correct speed and 100% compliant with maintaining their eyes on the optotype during the exercises regardless of the optotype size. Participants rated all exercises as “extremely easy.” CONCLUSIONS There was no difference in optotype performance in healthy multi-focal corrective lens users when completing pitch plane VOR exercises. Additional work is needed to determine if optotype size makes a difference in gaze stability in persons with vestibular hypofunction.