A clinical test of dynamic visual acuity for children.

OBJECTIVE: Children with sensorineural hearing impairment (SNHI) and concomitant vestibular hypofunction demonstrate deficits in gaze stability that may affect reading. The objective of this study was to develop a reliable, valid clinical test of dynamic visual acuity (DVA) for children.
METHODS: Seventy-six typically developing children, 26 adults and 11 children with sensorineural hearing impairment participated. Visual acuity was tested under three conditions: (1) head stable (static acuity), (2) head tipped forward 30 degrees and passively rotated 30 degrees in the yaw plane at 2 Hz (horizontal dynamic acuity) and (3) head passively moved in the pitch plane 30 degrees at 2 Hz (vertical dynamic acuity, vDVA). The difference, in number of chart lines, between static dynamic acuity was calculated (dynamic acuity score). Based on normative data collected, results were scored as: (1) pass < or =2S.D. from the normative mean and (2) fail > or =2S.D. from normative mean. Children were grouped by age to enable examination of the effect of age on scores.
RESULTS: We found excellent test-retest and inter-tester reliability (ICC(2,2)=0.94 and ICC(3,2)=0.84) for the horizontal dynamic acuity (hDVA) test. Sensitivity, specificity, positive and negative predictive values were 100% to identify children with bilateral vestibular hypofunction (BVH). Although a statistical difference was found, the difference was not clinically significant (all achieved DVA scores <2 lines). The vertical dynamic acuity test was not tolerated by most children, precluding its usefulness.
CONCLUSIONS: The clinical test of horizontal dynamic acuity is a reliable test for children as young as 3 years. It is simple and inexpensive, and will enable identification of those for whom more extensive testing is warranted.