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Rehab Measures: Dynamic Visual Acuity Test - Instrumented

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Get the DVAT-I from the NIH Toolbox 

Title of Assessment

Dynamic Visual Acuity Test - Instrumented 

Acronym

DVAT-I

Instrument Reviewer(s)

Matthew R Scherer PT, PhD, NCS

Jennifer L. Stoskus, PT, MSPT, DPT

Summary Date

5/9/2014 

Purpose

Provides an instrumented, objective, behavioral assessment of vestibulo-ocuar reflex (VOR) function in response to rotational or functional head movement stimuli. The Dynamic Visual Acuity Test (DVAT) assesses visual acuity during head movement relative to baseline static visual acuity. DVA has been used to assess gaze stability in all planes of head movement (i.e., yaw, pitch, roll, Right Anterior-Left Posterior, Left Anterior-Right Posterior) and has been reported in stationary as well as locomotor conditions. DVA can be assessed actively during self-generated rotations permitting the contribution of efference copy mediated signals in the form of “pre-programmed”, “compensatory”, or vestibular catch up saccades in the direction of the slow phase eye movement. DVA can also be assessed passively via unpredictable timing and direction, examiner-mediated impulses to isolate peripheral vestibular contributions to the VOR. The DVAT quantifies gaze stability by identifying the smallest computer optotype that a patient can accurately and consistently identify at head velocity thresholds which exclude non-vestibular mechanisms to gaze stability.

Description

Instrumented DVA is a test of gaze stability that uses a computer and a head-mounted rate sensor to trigger randomly oriented optotypes on a distant monitor when rotational head velocities exceed specified criteria for vestibular assessment (typically above 120 degrees/second). The test is considered behavioral (and not physiological) because correct identification and report of optotype orientation drives test scoring instead of direct measures of eye movement response kinematics. When performing the test, the participant is tasked to correctly identify the orientation of computer generated optotypes (e.g., a Landholt “C” an Irregular “E”) which randomly appear opening up, down, left, or right during head movements that exceed established criteria. DVA is established based on the smallest optotype size that a participant can consistently identify during head movements in the tested plane of head movement.

 

Visual acuity differences between static and head moving conditions are calculated separately for each plane of head movement. Within each plane, DVA values are further determined for each head impulse direction (e.g., left and right; up and down, left anterior-right posterior; and right anterior-left posterior).

 

Scoring:  Differences between static and dynamic visual acuity which correspond to levels of visual acuity “lost” on a clinical eye chart are commonly expressed in terms of the Log of the Minimum Angle Resolvable (LogMAR). LogMAR units describe the size of an image based on a ratio of its absolute size to its distance from the eye. 

 

Dynamic Visual Acuity Test (DVAT) Calibration Scale

Log MAR Visual Angle

MAR Visual Angle

(minutes of arc)

Visual Acuity

Size (inches)

at 20 feet

Size (inches) at 10 feet

- 0.3

0.50

20/10

0.18

0.09

- 0.2

0.63

20 / 13

0.22

0.11

- 0.1

0.79

20 / 15

0.28

0.14

  0.0

1.0

20 / 20

0.35

0.17

+ 0.1 

1.26

20 / 26

0.44

0.22

+ 0.2

16.0

20 / 32

0.56

0.28

+ 0.3

2.0

20 / 40

0.70

0.35

+ 0.4

2.51

20 / 50

0.88

0.44

+ 0.5

3.2

20 / 62

1.12

0.56

+ 0.6

4.0

20 / 80

1.40

0.70

+ 0.7

5.0

20 / 100

1.75

0.87

+ 0.8

6.4

20 / 130

2.24

1.12

+ 0.9

7.9

20 / 160

2.75

1.38

+ 1.0

10

20 / 200

3.50

1.75

 

Scoring: % Asymmetry

Some commercial DVA test versions provide % symmetry estimates (e.g., left vs. right or up vs. down).  Visual acuity differences for paired head movement directions are expressed as a percentage of asymmetry.

Area of Assessment

Vestibular; Vision & Perception 

Body Part

Head; Neck 

ICF Domain

Body Structure; Body Function 

Domain

Motor; Sensory 

Assessment Type

Performance Measure 

Length of Test

06 to 30 Minutes 

Time to Administer

10 Minutes (Yaw and Pitch rotational assessment)

Number of Items

Four most common testing conditions Yaw (Left, Right) and Pitch (up and down) (Herdman 1998, Schubert et al 2002) 

Equipment Required

Computerized Dynamic Visual Acuity system

  • Computer
  • Monitor
  • Head mounted rate sensor

Training Required

Training consists of familiarization with testing equipment and user’s manual. On the job training may be particularly useful. Specialized training is available for some systems if supported by the manufacturer.

Type of training required

reading an article/manual; training course; Reading an Article/Manual 

Cost

Not Free 

Actual Cost

Age Range

Child: 6-12 years; Adolescent: 13-17 years; Adult: 18-64 years; Elderly adult: 65+ 

Administration Mode

Computer 

Diagnosis

Acquired brain injury; Concussion; Traumatic Brain Injury; Vestibular Disorders 

Populations Tested

Healthy Adults (Herdman et al 1998, Vital 2010, Rine et al 2012)
Unilateral Vestibular Hypofunction (Herdman et al 1998, Herdman et al 2001, Vital 2010, Schubert 2002)
Heathy Pediatric Patients (Rine et al 2012)
Bilateral Vestibular Hypofunction, Adults (Herdman et al 1998, Herdman et al 2001, Vital 2010, Schubert 2002) 
Bilateral Vestibular Hypofunction, Pediatrics (Rine et al 2012)

Standard Error of Measurement (SEM)

Not Established

Minimal Detectable Change (MDC)

Not Established

Minimally Clinically Important Difference (MCID)

Not Established

Cut-Off Scores

Not Established

Normative Data

Healthy Adult Controls
(Herdman, 1998; n = 27; mean age= 39.3 (13.7) years). Active Yaw Head movement

Test-retest Reliability

Healthy Adult Controls

(Herdman, 1998; n = 27; mean age= 39.3 (13.7) years)

Excellent test retest reliability active yaw impulses, ICC: r = 0.87

Bilateral Vestibular Hypofunction and TBI, in healthy adult controls and pediatric patients (Rine et al 2012; n= 318: n = 301 healthy controls, n = 17; mean age age range 3-85) using HOTV, EDTRS, and Lea Optotypes.

Adequate to Good test-retest reliability for active yaw head movements: varies by age and optotypes selection

ICC = 0.55 for HOTV

ICC = 0.65 for ETDRS

ICC = 0.43 for Lea

Patients with vestibular deficits (UVH and BVH) and non-vestibular dizziness (Schubert et al 2002; N = 13 UVH; mean age= 54.6 (15.2) years; N = 11 BVH; mean age= 61.0 (11.9) years; N = 10 dizziness mean age 54.9 (20.4) years)

Excellent test-retest reliability for active pitch head movements, ICC: r = 0.94 (dizzy patients)

Excellent test – retest reliability for active pitch head movements, ICC: r = 0.89 (healthy control patients)

Unilateral and Bilateral Vestibular Hypofunction (UVH and BVH) (Herdman, 1998; N = 11; mean age = 68.7 (11.6) years)

Excellent test-retest reliability for active yaw impulses, ICC: r = 0.83

 

 

Interrater/Intrarater Reliability

Not Established

Internal Consistency

Not Established

Criterion Validity (Predictive/Concurrent)

Predictive Validity: Yaw, Active

Unilateral and Bilateral Vestibular Hypofunction (Herdman et al 1998)

·         Excellent Sensitivity (94.5%) for identifying vestibular hypofunction in patients vs. healthy controls.

·         Excellent Specificity (95.2%) for identifying vestibular hypofunction in patients vs. healthy controls.

·         Excellent Positive Predictive Value (96.3%)

·         Excellent Negative Predictive Value (93%)

 

 

Predictive Validity: Yaw Active and Passive

 

Unilateral and Bilateral Vestibular Hypofunction (Vital 2010; n= 100 healthy control participants; mean age = 45 (16) years) without otological and neurological disorders; n = 15 patients (mean age, 54 (13) years with unilateral or bilateral peripheral vestibular loss). Study investigators assessed participants at rotational velocities of 100 d/s and 150 d/s using active and passive yaw DVA and scleral search coil.

 

·        High Sensitivity (100%) for identifying unilateral or bilateral vestibular hypofunction in patients vs. healthy controls.

 

·        High Specificity (94%) for identifying unilateral or bilateral vestibular hypofunction in patients vs. healthy controls.

 

·        Passive impulses (z = 2.27) and faster rotational head movement testing velocity (at 150 d/s) (z = 2.08) significantly improved discrimination between control and patient participants; Best between groups discrimination occurred for rapid head movements under passive conditions (z = 2.72). 

 

Bilateral Vestibular Hypofunction and TBI, in healthy controls and pediatric patients (Rine et al 2012; n= 318: n = 301 healthy controls, n = 17; age range 3-85) using ETDRS optotype model.

·          Good Sensitivity = 73%

·          Good Specificity = 69%.

Predictive Validity: Active Pitch

 

Unilateral and Bilateral Vestibular Hypofunction (Schubert 2002)

·          Poor Sensitivity (23%) patients with UVH

·          Adequate Sensitivity (54.5%) patients with BVH

·          Excellent Specificity (90%) patients with UVH and BVH

 

Concurrent Validity

 

DVA and GST in older adults (Ward et al 2010; n = 40 (n =20 older adults mean age = 76.3 (5.3) years, n= 20 young controls mean age = 25.2 (3.2)

·          Good (Spearman’s r = -0.62) Active Yaw

·          Fair (Spearman’s r = -0.38) Active Pitch

 

DVA and Scleral Search Coil in healthy controls and patients with unilateral and bilateral vestibular loss (Vital 2010)

·         Excellent (r 2 = 0.72, p < 0.001)  Correlation of DVA loss and VOR gain (1 – gaze V/ head V) ) measured during quantitative passive head impulse testing (HIT)

vDVA and rotary chair in patients with vestibular deficits (UVH and BVH) and non-vestibular dizziness (Schubert et al 2002)

Distribution of patient subjects by positive and negative vertical dynamic visual acuity (vDVA) scores.

 

 

Positive Dx

Negative Dx

Total # Participants

Abnormal vDVA Score

DZ = 0

DZ = 1

 

UVH = 3

UVH =  0

 

BVH = 6

BVH = 0

 

Normal vDVA Score

DZ = 0

DZ = 9

n = 10

UVH = 10

UVH = 0

 

BVH = 5

BVH = 0

n = 15

Total

n = 24

N = 10

n = 34

Key: UVH- Unilateral Vestibular Hypofunction, BVH- Bilateral Vestibular Hypofunction, DZ- dizziness

 

Positive DX, positive diagnosis (positive caloric and rotary chair test result);

Negative DX, negative diagnosis (negative caloric and rotary chair test result);

Abnormal vDVA, vertical dynamic visual acuity Log-MAR score > 2 SD above the mean for age-matched normal subjects;

Normal vDVA, vDVA (LogMAR) score within 2 SD of the mean for age-matched normal subjects; DZ, nonvestibular dizziness; UVH, unilateral vestibular hypofunction; BVH, bilateral vestibular hypofunction.

 

Construct Validity (Convergent/Discriminant)

Not Established

Content Validity

Not Established

Face Validity

Passive, Yaw plane impulses can localize side of vestibular lesion as established by Caloric Assessment

Vestibular Disease (UVL, BVL) (Herdman 2001)

·          Unpredictable timing and direction head movements result in significantly degraded DVA relative to predictable (active) head movements toward the affected side with UVL (p < 0.001) and BVL (0.004).

·       Unpredictable head movements have a greater effect on DVA in older subjects than younger in patients with vestibular loss (p < 0.001) (Herdman 2001; Healthy n = 26; mean age = 39.6 (15.5) years; UVL n = 20; mean age = 66.7 (13.1) years; BVL n = 7; mean age = 63.4 (12.7) years).

 

Superior Canal plugging post dehiscence (Schubert 2006)

·       Passive, head thrust DVA in individual canal planes (Right Anterior, Left Posterior, Left Anterior, or Right Posterior) accurately quantifies gaze instability in patients with singular canal plane deficits.   (Schubert 2006; n = 19 healthy controls mean age = 34.4 (11.8) years, n = 5 pre SSCC plugging and 6 SSCC plugging mean age = 47 (9.1) years.

 

DVA while walking in normal and patients with BVH (Hillman 1998; n = 10 healthy controls mean age = 30.8; n = 5 with BVH, mean age = 40).

·      Gaze stability during treadmill locomotion in patients with BVH was significantly degraded relative to DVA in healthy control participants.

Floor/Ceiling Effects

Not Established

Responsiveness

Not Established

Professional Association Recommendations

  • Patient should be cleared of vascular and orthopedic contraindications (i.e. vertebral artery integrity and cervical stability) and demonstrate full, pain-free active range of motion in the plane of testing.
  • Passive DVA in which head impulses are administered by an examiner which are unpredictable in timing and direction, isolates peripheral vestibular contributions to gaze stability (independent of centrally mediated efference copy signals). Passive DVA should be characterized separately from active DVA to optimally characterize the head movement conditions in which a patient demonstrates deficient gaze stability.
  • Use of ETDRS optotypes appear superior to HOTV or Lea optotypes per NIH Toolkit guidelines. ETDRS eye charts are readily available and widely accepted used for visual acuity testing. See below site for graphic: http://www.precision-vision.com/index.cfm/category/34/etdrs-charts.cfm

Considerations

Bibliography

Hall, C. D., Schubert, M. C., et al. (2004). "Prediction of fall risk reduction as measured by dynamic gait index in individuals with unilateral vestibular hypofunction." Otol Neurotol 25(5): 746-751. Find it on PubMed

Herdman, S. J., Schubert, M. C., et al. (2001). "Role of central preprogramming in dynamic visual acuity with vestibular loss." Arch Otolaryngol Head Neck Surg 127(10): 1205-1210. Find it on PubMed

Herdman, S. J., Tusa, R. J., et al. (1998). "Computerized dynamic visual acuity test in the assessment of vestibular deficits." Am J Otol 19(6): 790-796. Find it on PubMed

Rine, R. M., Roberts, D., et al. (2012). "New portable tool to screen vestibular and visual function--National Institutes of Health Toolbox initiative." J Rehabil Res Dev 49(2): 209-220. Find it on PubMed

Schubert, M. C., Herdman, S. J., et al. (2002). "Vertical dynamic visual acuity in normal subjects and patients with vestibular hypofunction." Otol Neurotol 23(3): 372-377. Find it on PubMed

Schubert, M. C., Migliaccio, A. A., et al. (2008). "Mechanism of dynamic visual acuity recovery with vestibular rehabilitation." Arch Phys Med Rehabil 89(3): 500-507. Find it on PubMed

Schubert, M. C., Migliaccio, A. A., et al. (2006). "Dynamic visual acuity during passive head thrusts in canal planes." J Assoc Res Otolaryngol 7(4): 329-338. Find it on PubMed

Tian, J. R., Shubayev, I., et al. (2001). "Dynamic visual acuity during transient and sinusoidal yaw rotation in normal and unilaterally vestibulopathic humans." Exp Brain Res 137(1): 12-25. Find it on PubMed

Vital, D., Hegemann, S. C., et al. (2010). "A new dynamic visual acuity test to assess peripheral vestibular function." Arch Otolaryngol Head Neck Surg 136(7): 686-691. Find it on PubMed

Ward, B. K., Mohammad, M. T., et al. (2010). "The reliability, stability, and concurrent validity of a test of gaze stabilization." J Vestib Res 20(5): 363-372. Find it on PubMed

Year published

1998 

Instrument in PDF Format

No 
Approval Status Approved 
 
Attachments
Created at 5/9/2014 10:46 AM  by Jason Raad 
Last modified at 5/12/2014 12:32 PM  by Jason Raad