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Clinical and Computerized Test of Dynamic Visual Acuity
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Supplemental: Sport-related Concussion (SRC) Subacute (after 72 hours to 3 months) and Persistent/Chronic (3 months and greater post concussion)
Exploratory: Sport-related Concussion (SRC) Acute (time of injury until 72 hours)
Short Description of Instrument
Provides a “low-tech”, objective, behavioral measure of vestibulo-ocular reflex (VOR) function in response to examiner generated (i.e., “passive”) rotational head movement stimuli. The DVAT NI provides a functional, low-cost assessment of gaze stability that can be administered in any clinical environment. This measure is used to screen for and characterize the severity of gaze instability (quantified as “lines lost” on an eye chart) and is commonly administered in conjunction with other “bed-side” clinical tests of vestibular function like the Head Impulse Test or the Head Shaking Nystagmus Test in the absence of more sophisticated assessment techniques.  
The non-instrumented Dynamic Visual Acuity Test (DVAT NI) assesses gaze stability during sinusoidal, examiner mediated head rotations relative to head-stationary visual acuity.  To administer this test, visual acuity is first assessed under static head movement conditions (i.e., no head movement). The patient is instructed to wear prescription lenses if needed for distance viewing and then seated a specified distance before an optometric eye exam chart (e.g., 4 meters for the commonly used Early Treatment of Diabetic Retinopathy Study (ETDRS) chart or 20 feet for a standard optometric Snellen Chart).  The patient is instructed to read the lowest line recognizable and to keep reading until he or she can no longer identify all the letters on a given line. The examiner should take note of the last line where all letters were correctly identified and the total number of letters correctly identified.  
For the dynamic component of the test, the examiner should stand behind the patient and firmly grasp the patient’s head with both hands just above the ears. For testing in the yaw plane, the patient’s head should be flexed forward ~ 30 degrees to bring the horizontal semicircular canals into the plane of testing (i.e., the horizontal plane). Next, the examiner will oscillate the head at a magnitude of 20–30 degrees from mid line about a vertical axis taking care to restrict range for patients with corrective lenses.  Frequency of rotation should occur at 2 Hz (i.e., 2 cycles per second) to achieve adequate stimulus intensity to drive a hypofunctional vestibular end organ into inhibitory cutoff. The patient will read the letters on the lowest line of the eye chart possible until he or she can no longer correctly identify them. The examiner should note this line and record the number of optotypes incorrectly identified. A loss of three or more lines of visual acuity relative to one’s static visual acuity is regarded as clinically significant and suggestive of possible vestibular dysfunction.
Time to administer: 3 minutes
Cost: Free
Age range: Preschool child 3–5 years; Child 6–12 years; Adolescent 13–17 years; Adult: 18–64 years; Elderly adult: 65+
Clinical and Computer Equipment required: Eye Chart (e.g., ETDRS, Lighthouse, E or Snellen)
Performance measure
Dannenbaum E, Paquet N, Hakim-Zadeh R, Feldman AG. Optimal parameters for the clinical test of dynamic visual acuity in patients with a unilateral vestibular deficit. J Otolaryngol. 2005;34(1):13–19.  
Dannenbaum E, Paquet N, Chilingaryan G, Fung J. Clinical evaluation of dynamic visual acuity in subjects with unilateral vestibular hypofunction. Otol Neurotol. 2009;30(3):368–372.
Longridge NS, Mallinson AI. The Dynamic Illegible E-test: A Technique for Assessing the Vestibulo-ocular Reflex. Acta Otolaryngol. 1987;103(5-6):273–279.  
Longridge NS, Mallinson AI. A discussion of the dynamic illegible "E" test: a new method of screening for aminoglycoside vestibulotoxicity. Otolaryngol Head Neck Surg. 1984 Dec;92(6):671–677.  
Rine RM, Braswell J. A clinical test of dynamic visual acuity for children. Int J Pediatr Otorhinolaryngol. 2003;67(11):1195–1201.
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