Nystagmus duration after caloric irrigations.

Objective: To measure nystagmus duration after warm and cool caloric water irrigations, with the aim of providing preliminary evidence for the optimum interval between irrigation onsets; and to compare nystagmus durations between warm and cool irrigations, in addition to maximum slow phase velocity (SPV).Design: Participants underwent up to four caloric irrigations during routine appointments. Nystagmus was recorded to minimal levels (within 2°/s of subject's baseline). The nystagmus duration and maximum SPV were measured.Study Sample: 52 vestibular assessment patients (99 ears).Results: The mean nystagmus duration was 183.9 s (seconds) (3:04 min) from irrigation onset, and nystagmus became minimal after 264.8 s (4:25 min) in 97.5% of this sample. The population mean is within ±6.7 s of the sample mean (p = <0.001). There was no significant difference between warm and cool irrigation durations, and correlation and linear regression analysis showed duration cannot reliably be predicted by maximum SPV.Conclusions: Mean nystagmus duration (3 min after irrigation onset) and nystagmus duration for 97.5% of patients (<4.5 min) were substantially less than the BSA recommended 7 min between irrigations. These findings provide preliminary evidence for shortening of intervals between stimulus onsets, regardless of irrigation temperature or maximum SPV, to reduce caloric testing time and improve clinical efficiency.

Age Is a Greater Influence on Small Saccades Than Target Size in Normal Subjects on the Horizontal Video Head Impulse Test.

Objective: This study sought to investigate whether the size of the target used in the horizontal vHIT has an effect on the saccade profile of healthy subjects, and to expand upon previous work linking age to the existence of small vHIT saccades. Methods: Forty eight participants were recruited between 18 and 77 years of age, with no history of vestibular, oculomotor or neurological conditions and a visual acuity of at least 0.3 LogMAR. Participants underwent four consecutive horizontal vHIT trials using the standard target size and three smaller targets. VOR gain and metrics for saccadic incidence, peak eye velocity and latency were then extracted from results. Results: Target size was a statistically significant influence on saccade metrics. As target size increased, saccadic incidence decreased while peak eye velocity and latency increased. However, a potential order effect was also discovered, and once this was corrected for the remaining effect of target size was small and is likely clinically insignificant. The effect of age was much stronger than target size; increasing age was strongly positively correlated with saccadic incidence and showed a medium size correlation with peak velocity, though not with saccadic latency. Conclusion: While this study suggests that target size may have a statistically significant impact on the vHIT saccade profile of normal subjects, age has a greater influence on the incidence and size of small vHIT saccades.