PURPOSE: Historically, dynamic visual acuity (OVA) measurement relied on instruments that presented a moving target at a high velocity that was gradually slowed until the subject could correctly identify it (head stable, target moving). This type of testing, however, bears little resemblance to typical OVA stimuli encountered in daily life. The purpose of this project is to introduce preliminary normative data for a new device using a stationary stimulus viewed during calibrated head movements to measure OVA. This condition is much more representative of the OVA tasks encountered in everyday life.
METHODS: Fifty-four subjects aged 23-57 years were evaluated using the inVision™ system (NeuroCom® International, Inc.). The PC-based instrument presents a tumbling E stimulus when the subject achieves a given head movement velocity as monitored by a head-borne accelerometer. Subjects are instructed to move the head to and fro (as if to say "no") at differing velocities. When the target head velocity is reached, a tumbling E is presented on the computer monitor and the subject must make a forced choice regarding the orientation of the stimulus. Data were obtained for two protocols: OVA (head velocity is held constant and the stimulus size is gradually reduced) and gaze stabilization (stimulus size is held constant and head velocity is increased).
RESULTS: The inVision™ system demonstrated excellent testability, all fifty-four subjects were able to complete both test protocols. With increasing age, there appears to be a trend toward decreasing performance, but no statistical significant differences were found. Further testing involving older subjects is needed to uncover more definite trends with age. When the data were analyzed by refractive category, high myopes (>4.000) performed significantly poorer on the OVA test. There were no differences in this group based on static visual acuity, age, or type of correction.
CONCLUSION: While the inVision™ system is currently being used mostly in vestibular/ENT cl inical settings, it offers intriguing potential for utilization in optometric science. Previous studies have shown that OVA performance cannot be predicted by other tests commonly used in optometric patient evaluations, and our results suggest the same. Hence, this instrument may provide a unique new assessment tool to aid the clinician in the diagnosis and management of visual conditions that cannot be quantified using static methods of visual assessment.
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