Ocular counter-rolling in scuba divers with motion sickness.

OBJECTIVE

Motion sickness (MS) is a familiar condition to scuba divers. The purpose of this study was to compare otolith organ function of scuba divers who have MS to those without MS.

METHOD

Video-oculography (VOG) goggles were used to measure video ocular counter-roll (vOCR) in 50 healthy scuba divers with no vestibular pathology. Divers with MS (n = 30) had Graybiel motion sickness (GMS) scores of ≥1 point, and divers without MS (n = 20) had GMS scores of 0. Divers with MS also completed the Motion Sickness Susceptibility Questionnaire short form (MSSQs). For all divers, otolith-ocular function of both ears was tested separately via vOCR testing, which was performed during 30° head tilt. An R-L side asymmetry ratio for vOCR values (%OCRA) was compared to divers' static OCR.

RESULTS

MSSQs and %OCRA scores differed significantly (p<0.01and p<0.001, respectively) between divers with MS and divers without MS. Their %OCRA scores and severity of MS were significantly correlated. Female divers were more susceptible to MS. ROC analysis for %OCRA revealed that the AUC for divers with MS and divers without MS was 0.8967 (95% CI, 0.8114 to 0.9819), the specificity was 1.000, and the sensitivity was 0.700, with a cutoff value of 45.946.

CONCLUSION

Physiological differences between R-L otolith organ function could affect the severity and susceptibility to MS. Female hormones may also increase susceptibility to MS. Thus, MS may be a physiological phenomenon induced by functional ear differences in the absence of pathology. As MS is caused by multiple factors, otolaryngologists need to consider various causative factors beyond those related to otolith organ function in scuba divers with MS.