Recovery of Visual Acuity in People With Vestibular Deficits

• Change in Visual Acuity During Head Movement From Baseline to Discharge [ Time Frame: pre-intervention and at discharge ]

  visual acuity is measured using a computerized system first with the head stationary and then with the head moving in yaw plane. Head velocity is measured using a rate sensor and optotype is displayed only when head velocity is between 120 and 180 degrees per second.

  The change in visual acuity was calculated from subtracting the discharge measurement from the baseline measurement (pre-intervention).

  
  
• Subjective Complaints: (All Pre- and Post-intervention): [ Time Frame: pre-intervention, 2 weeks, 4 weeks and at discharge ]
  questionnaire
  
  

• Disability Scale [ Time Frame: pre-intervention, 2 weeks, 4 weeks and at discharge ]
  questionnaire
  
  
• Activities Specific Balance Confidence Scale [ Time Frame: pre-intervention, 2 weeks, 4 weeks and at discharge ]
  questionnaire
  
  
• Symptoms Intensity for Dizziness, Oscillopsia, Disequilibrium [ Time Frame: pre-intervention, 2 weeks, 4 weeks and at discharge ]
  visual analoque scales
  
  
• Balance and Gait [ Time Frame: pre-intervention, 2 weeks, 4 weeks and at discharge ]
  gait speed
  
  
• Fall Risk (Dynamic Gait Index) [ Time Frame: pre-intervention, 2 weeks, 4 weeks and at discharge ]
  performance test
  
  
• Eye Movements: Scleral Search Coil [ Time Frame: pre- and post-treatment ]
  eye movements are measured by having the participant sit within an electromagnetic field while wearing a scleral coil (like a contact lens but only in contact with the sclea, not the cornea); te coil moves with eye movement and distorts the electrimagnetic field
  
  

Decrements in visual acuity during head movement in patients with vestibular hypofunction are potentially serious problems. This deficit could contribute to decreased activity level, avoidance of driving with resultant diminished independence and, ultimately, limited social interactions and increased isolation. Oscillopsia occurs because of inadequate vestibulo-ocular reflex (VOR) gain and suggests that compensation for the vestibular loss has not occurred. The purpose of this study was to examine the effect of an exercise intervention on visual acuity during head movement in patients with unilateral and bilateral vestibular hypofunction. We hypothesized that 1) patients performing vestibular exercises would have improved visual acuity during head movement compared to patients performing placebo exercises; 2) there would be no correlation between dynamic visual acuity (DVA) and the patients' subjective complaints of oscillopsia; and 3) improvement in DVA would be reflected by changes in residual vestibular function as indicated by an increase in VOR gain.

Patients are assigned randomly to either the vestibular exercise or placebo exercise group. The randomization schedule is generated using a computer program for 2-sample randomization. The sequence was not concealed from the investigator who obtained consent from the subjects and supervised the exercises (SJH). The group assignment (vestibular exercise or placebo exercise) was concealed from the participants and from the investigator who performed the outcome measures.

The vestibular exercise group practiced exercises that consisted of adaptation exercises and eye-head exercises to targets (Table 1), which were designed to improve gaze stability 16. They also performed gait and balance exercises. The placebo exercise group performed exercises designed to be 'vestibular-neutral'.