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Background: Unilateral peripheral vestibular hypofunction can result in symptoms of dizziness, gaze and gait instability, and impaired navigation and spatial orientation. These impairments and activity limitations may negatively impact an individual's quality of life, ability to perform activities of daily living, drive, and work. There is strong evidence supporting vestibular physical therapy for reducing symptoms, improving gaze and postural stability, and improving function in individuals with vestibular hypofunction. However, there is great variability in clinical practice with regard to the type of interventions and only weak evidence to guide optimal exercise dosage. It is important to identify the most appropriate interventions and exercise dosage to optimize and accelerate recovery of function and to decrease distress. The objective of this systematic review is to determine which interventions and which doses are most effective in decreasing dizziness or vertigo, improving postural control, and improving quality of life in adults with unilateral peripheral vestibular hypofunction., Methods: The literature will be systematically searched using the following online databases: PubMed/MEDLINE, EMBASE, Web of Science (Science and Social Science Citation Index), Cumulative Index for Nursing and Allied Health Literature (CINAHL), and The Cochrane Library (Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials [CENTRAL], Cochrane Methodology Register). The review will include randomized controlled trials (RCTs), including cluster RCTs, to assess the beneficial effects of the interventions. Assessment of methodological quality and risk of bias will be performed by two independent, blinded reviewers using the PEDro scale and Cochrane Risk of Bias version 2, respectively. The primary outcome measure will be change in self-perceived handicap related to dizziness from baseline to the end of the study, measured using the Dizziness Handicap Inventory. Other relevant outcome measures will include self-reported change in symptoms (to include severity, frequency, and duration) such as verbal or visual analog scales for dizziness. Tertiary outcome measures will include questionnaires related to disability and/or quality of life., Discussion: This systematic review will identify, evaluate, and integrate the evidence on the effectiveness of physical therapy interventions for unilateral peripheral vestibular hypofunction in an adult population. We anticipate our findings may inform individualized treatment and future research. Clinical recommendations generated from this systematic review may inform vestibular physical therapy treatment of individuals with unilateral peripheral vestibular hypofunction., Trial Registration: In accordance with the guidelines, our systematic review protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO) on 06 August 2021 (registration number CRD42021266163 ). In the event of protocol amendments, the date of each amendment will be accompanied by a description of the change and the rationale., (© 2023. BioMed Central Ltd., part of Springer Nature.)

Dizziness is very common, but it is never normal. Dizziness can make performing daily activities, work, and walking difficult. Inner ear balance problems can make people dizzy when they turn their head, which can cause problems during walking and make people more likely to fall. Most of the time dizziness is not from a life-threatening disease. Often, dizziness is related to a problem of the vestibular (or inner ear balance) system. Vestibular disorders can be caused by infections in the ear, problems with the immune system, medications that harm the inner ear, and rarely from diabetes or stroke because of a lack of blood flow to the inner ear. Stress, poor sleep, migraine headaches, overdoing some activities, and feeling anxious or sad can increase symptoms of dizziness. Updated guidelines for the treatment of inner ear disorders are published in this issue of the Journal of Neurologic Physical Therapy. The guideline recommends which exercises are best to treat the dizziness and balance problems commonly seen with an inner ear problem., Competing Interests: The authors declare no conflict of interest., (Copyright © 2021 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of Academy of Neurologic Physical Therapy, APTA.)

Background: Uncompensated vestibular hypofunction can result in symptoms of dizziness, imbalance, and/or oscillopsia, gaze and gait instability, and impaired navigation and spatial orientation; thus, may negatively impact an individual's quality of life, ability to perform activities of daily living, drive, and work. It is estimated that one-third of adults in the United States have vestibular dysfunction and the incidence increases with age. There is strong evidence supporting vestibular physical therapy for reducing symptoms, improving gaze and postural stability, and improving function in individuals with vestibular hypofunction. The purpose of this revised clinical practice guideline is to improve quality of care and outcomes for individuals with acute, subacute, and chronic unilateral and bilateral vestibular hypofunction by providing evidence-based recommendations regarding appropriate exercises., Methods: These guidelines are a revision of the 2016 guidelines and involved a systematic review of the literature published since 2015 through June 2020 across 6 databases. Article types included meta-analyses, systematic reviews, randomized controlled trials, cohort studies, case-control series, and case series for human subjects, published in English. Sixty-seven articles were identified as relevant to this clinical practice guideline and critically appraised for level of evidence., Results: Based on strong evidence, clinicians should offer vestibular rehabilitation to adults with unilateral and bilateral vestibular hypofunction who present with impairments, activity limitations, and participation restrictions related to the vestibular deficit. Based on strong evidence and a preponderance of harm over benefit, clinicians should not include voluntary saccadic or smooth-pursuit eye movements in isolation (ie, without head movement) to promote gaze stability. Based on moderate to strong evidence, clinicians may offer specific exercise techniques to target identified activity limitations and participation restrictions, including virtual reality or augmented sensory feedback. Based on strong evidence and in consideration of patient preference, clinicians should offer supervised vestibular rehabilitation. Based on moderate to weak evidence, clinicians may prescribe weekly clinic visits plus a home exercise program of gaze stabilization exercises consisting of a minimum of: (1) 3 times per day for a total of at least 12 minutes daily for individuals with acute/subacute unilateral vestibular hypofunction; (2) 3 to 5 times per day for a total of at least 20 minutes daily for 4 to 6 weeks for individuals with chronic unilateral vestibular hypofunction; (3) 3 to 5 times per day for a total of 20 to 40 minutes daily for approximately 5 to 7 weeks for individuals with bilateral vestibular hypofunction. Based on moderate evidence, clinicians may prescribe static and dynamic balance exercises for a minimum of 20 minutes daily for at least 4 to 6 weeks for individuals with chronic unilateral vestibular hypofunction and, based on expert opinion, for a minimum of 6 to 9 weeks for individuals with bilateral vestibular hypofunction. Based on moderate evidence, clinicians may use achievement of primary goals, resolution of symptoms, normalized balance and vestibular function, or plateau in progress as reasons for stopping therapy. Based on moderate to strong evidence, clinicians may evaluate factors, including time from onset of symptoms, comorbidities, cognitive function, and use of medication that could modify rehabilitation outcomes., Discussion: Recent evidence supports the original recommendations from the 2016 guidelines. There is strong evidence that vestibular physical therapy provides a clear and substantial benefit to individuals with unilateral and bilateral vestibular hypofunction., Limitations: The focus of the guideline was on peripheral vestibular hypofunction; thus, the recommendations of the guideline may not apply to individuals with central vestibular disorders. One criterion for study inclusion was that vestibular hypofunction was determined based on objective vestibular function tests. This guideline may not apply to individuals who report symptoms of dizziness, imbalance, and/or oscillopsia without a diagnosis of vestibular hypofunction., Disclaimer: These recommendations are intended as a guide to optimize rehabilitation outcomes for individuals undergoing vestibular physical therapy. The contents of this guideline were developed with support from the American Physical Therapy Association and the Academy of Neurologic Physical Therapy using a rigorous review process. The authors declared no conflict of interest and maintained editorial independence.Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A369)., Competing Interests: All members of the Guideline Development Group and Advisory Board completed conflict of interest forms, which included information about grant funding, royalties, device/company shares, legal assistance, patents, device consultant/advocacy, publications, presentations, and clinical practice related to the Clinical Practice Guideline (CPG) topic. Forms were submitted to the Academy of Neurologic Physical Therapy (ANPT) Evidence-Based Documents Committee, who monitored and managed any identified perceived conflicts of interest. All recommendations were written as a group per standard CPG methodology. Therefore, no one individual made all the decisions. These recommendations are intended as a guide to optimize rehabilitation outcomes for individuals undergoing vestibular physical therapy. The contents of this guideline were developed with support from the American Physical Therapy Association and the Academy of Neurologic Physical Therapy using a rigorous review process. The authors declared no conflict of interest and maintained editorial independence., (Copyright © 2021 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of Academy of Neurologic Physical Therapy, APTA.)

Objective: The purpose of this study was to determine factors associated with rehabilitation outcomes following vestibular rehabilitation (VR)., Methods: In this prospective cohort study, 116 patients who completed at least 2 supervised sessions participated. Patient characteristics and comorbidities were recorded. Initial and discharge measures included symptom intensity, balance confidence, quality of life, percent of time symptoms interfere with life, perceived benefits of VR, gait speed, fall risk, visual acuity during head movement, and anxiety/depression. Intention-to-treat analyses were performed to determine outcomes at discharge. Bivariate correlations between independent (group characteristics and baseline measures) and dependent (discharge measures) variables were determined. Logistic regressions were performed to identify factors associated with whether a patient would have a normal score or meaningful change at discharge., Results: There was a large effect of VR with significant improvement for the group as a whole on each outcome measure. For each outcome measure, most patients improved. Based on preliminary logistic regression, 2 patient characteristics were associated with outcome: number of therapy visits predicted meaningful improvement in gait speed, and falls after the onset of the unilateral vestibular hypofunction (UVH) predicted meaningful change in the percent of time symptoms interfered with life. Initial Activities-Specific Balance Confidence Scale (ABC) and Dynamic Gait Index scores predicted normal ABC scores at discharge, and initial ABC scores predicted recovery of Dynamic Gait Index scores. Preliminary prediction models were generated for balance confidence, impact of dizziness on life, dynamic visual acuity, gait speed, and fall risk., Conclusions: Therapists may use these findings for patient education or to determine the need for adjunct therapy, such as counseling., Impact: Not all people with UVH improve following VR, but there is little research examining why. This study looked at multiple factors and identified number of visits and falls after onset of UVH as patient characteristics associated with outcomes following VR; these findings will help therapists create better predictive models., (© The Author(s) 2020. Published by Oxford University Press on behalf of the American Physical Therapy Association. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Background: Uncompensated vestibular hypofunction results in postural instability, visual blurring with head movement, and subjective complaints of dizziness and/or imbalance. We sought to answer the question, "Is vestibular exercise effective at enhancing recovery of function in people with peripheral (unilateral or bilateral) vestibular hypofunction?", Methods: A systematic review of the literature was performed in 5 databases published after 1985 and 5 additional sources for relevant publications were searched. Article types included meta-analyses, systematic reviews, randomized controlled trials, cohort studies, case control series, and case series for human subjects, published in English. One hundred thirty-five articles were identified as relevant to this clinical practice guideline., Results/discussion: Based on strong evidence and a preponderance of benefit over harm, clinicians should offer vestibular rehabilitation to persons with unilateral and bilateral vestibular hypofunction with impairments and functional limitations related to the vestibular deficit. Based on strong evidence and a preponderance of harm over benefit, clinicians should not include voluntary saccadic or smooth-pursuit eye movements in isolation (ie, without head movement) as specific exercises for gaze stability. Based on moderate evidence, clinicians may offer specific exercise techniques to target identified impairments or functional limitations. Based on moderate evidence and in consideration of patient preference, clinicians may provide supervised vestibular rehabilitation. Based on expert opinion extrapolated from the evidence, clinicians may prescribe a minimum of 3 times per day for the performance of gaze stability exercises as 1 component of a home exercise program. Based on expert opinion extrapolated from the evidence (range of supervised visits: 2-38 weeks, mean = 10 weeks), clinicians may consider providing adequate supervised vestibular rehabilitation sessions for the patient to understand the goals of the program and how to manage and progress themselves independently. As a general guide, persons without significant comorbidities that affect mobility and with acute or subacute unilateral vestibular hypofunction may need once a week supervised sessions for 2 to 3 weeks; persons with chronic unilateral vestibular hypofunction may need once a week sessions for 4 to 6 weeks; and persons with bilateral vestibular hypofunction may need once a week sessions for 8 to 12 weeks. In addition to supervised sessions, patients are provided a daily home exercise program., Disclaimer: These recommendations are intended as a guide for physical therapists and clinicians to optimize rehabilitation outcomes for persons with peripheral vestibular hypofunction undergoing vestibular rehabilitation.Video Abstract available for more insights from the author (see Video, Supplemental Digital Content 1, http://links.lww.com/JNPT/A124).

Background: Vestibular rehabilitation (VR) improves symptoms and function in some but not all patients with bilateral vestibular hypofunction (BVH)., Objective: The purpose of this retrospective study was to examine change following vestibular rehabilitation and to identify factors associated with rehabilitation outcome in patients with BVH., Methods: Data from 69 patients with BVH were analyzed. Factors studied included patient characteristics, subjective complaints and physical function. Outcome measures included symptom intensity, balance confidence, quality of life, gait speed, fall risk, and dynamic visual acuity. Bivariate correlations were used to examine relationships of patient characteristics and baseline measures with outcome measures. One-way ANOVAs were used to compare outcomes in patients with BVH versus unilateral vestibular hypofunction (UVH)., Results: As a group, patients with BVH improved in all outcome measures except disability following a course of vestibular rehabilitation (VR); however, only 38-86% demonstrated a meaningful improvement, depending on the specific outcome measure examined. Several factors measured at baseline - age, DGI score, gait speed and perceived dysequilibrium - were associated with outcomes. For example, greater age was related to higher DVA scores at discharge; lower initial DGI scores were related to higher Disability scores at discharge. Compared to patients with UVH, reported previously [9], a smaller percentage of patients with BVH improve and to a lesser extent., Conclusion: Consideration of baseline factors may provide guidance for setting patient goals. Further research is needed determine what factors predict outcome and to develop more effective treatment strategies for those patients who do not improve.

Purpose of Review: This review examines the research from 2011 through 2012 on treatment efficacy in two common vestibular disorders - vestibular hypofunction and benign paroxysmal positional vertigo (BPPV)., Recent Findings: Significant numbers of randomized controlled trials now support the use of specific exercises for the treatment of patients with unilateral peripheral vestibular hypofunction. We do not know if some treatment approaches are more effective than others. There is preliminary evidence that head movement may be the component critical to recovered function and decreased symptoms. Some patient characteristics and initial assessment results appear to predict treatment outcome but the evidence is incomplete. Treatment of posterior canal BPPV canalithiasis is well established. New evidence supports certain treatments for horizontal canal BPPV., Summary: Treatments for unilateral vestibular hypofunction and for posterior canal BPPV are effective; however, there are many as yet unanswered questions such as why some patients with vestibular hypofunction do not improve with a course of vestibular exercises. We also do not know what would be the best treatment for anterior canal BPPV or for multiple-canal involvement BPPV.

Background: Not all individuals with unilateral vestibular hypofunction (UVH) have fewer subjective complaints and improved function after vestibular rehabilitation., Objective: To identify factors and/or combinations of factors that are strongly associated with rehabilitation outcome in patients with UVH and that ultimately can be used to develop models to predict outcome., Methods: Data from 209 patients with UVH were analyzed. All patients participated in similar vestibular rehabilitation (5 weeks of home exercises and once-weekly clinic visits). Outcome measures included intensity of oscillopsia and dysequilibrium, balance confidence, perceived disability, percentage of time symptoms interfered with activities, gait speed, fall risk, and dynamic visual acuity (DVA). Bivariate correlation and regression analysis were used to determine relationships between baseline (pretherapy) measures and outcome at discharge., Results: No baseline measure of subjective complaints (eg, symptom intensity) predicted improvement of physical function (eg, gait speed). Similarly, no baseline measure of physical function predicted improvement of subjective complaints. Certain patient characteristics, such as gender and time from onset, were not related to any outcomes. Most comorbidities did not affect outcome; however, anxiety and/or depression were associated with lower balance confidence and higher percentage of time for which symptoms interfered with activities at discharge. Baseline DVA and gait speed were associated with DVA and gait speed at discharge, respectively. Dynamic gait index (DGI) at discharge was affected by age, baseline DGI, and history of falls., Conclusion: These results provide insight into recovery of patients with UVH. Therapists can use this information in the development of expectations for patient outcome and treatment priorities.

Specific criteria have been developed based on computerized dynamic posturography (CDP) to assist clinicians in identifying patients with psychogenic balance problems (Cyr and Cevette, 1993; Cevette et al., 1995; Goebel et al., 1997; Gianoli et al., 2000). Patients with known spinocerebellar ataxia (SCA) meet several of the criteria for psychogenic balance problem and risk being misclassified as having imbalance of psychogenic origin. However, our research shows that patients with SCA may be distinguished from patients with psychogenic balance problems in several ways. We compared test performance on CDP and the observation of specific behaviors that are associated with psychogenic balance problems in patients with SCA (n = 43) and patients with known psychogenic balance problems (n = 40). Chi-square analysis was used to determine if there were significant differences between the groups for the frequency of each criterion for psychogenic CDP and Observed Behaviors. Level of significance was Bonferroni corrected for multiple comparisons. Sensitivity, specificity, and positive likelihood ratios were calculated for each criterion. Hierarchical cluster analysis was used to examine whether the two patient groups demonstrated similar groupings of criteria. Comparison of the results of these analyses identified two criteria that were significantly more frequent in the psychogenic group than in the SCA group: regular periodicity of sway and circular sway. Sensitivity, specificity, and positive likelihood ratios identified two additional criteria, inconsistent motor responses and large lateral sway that also seem to suggest a psychogenic component to a person's imbalance. Prospective studies are needed to validate the usefulness of these findings.

This work reports the use of a head-motion monitoring system to record patient head movements while completing in-home exercises for vestibular rehabilitation therapy. Based upon a dual-axis gyroscope (yaw and pitch, ± 500-degrees/sec maximum), angular head rotations were measured and stored via an on-board memory card. The system enabled the clinician to document exercises at home. Several measurements were recorded in one patient with unilateral vestibular hypofunction: The total time of exercise for the week (118 minutes) was documented and compared with expected weekly exercise time (140 minutes). For gaze stabilization exercises, execution time of 60 sec was expected, and observed times ranged from 75-100 sec. An absence of rest periods between each exercise instead of the recommended one minute rest period was observed. Maximum yaw head velocities from approximately 100-350 degrees/sec were detected. A second subject provided feedback concerning the ease of use of the HAMMS device. This pilot study demonstrates, for the first time, the capability to capture the head-motion "signature" of a patient while completing vestibular rehabilitation exercises in the home and to extract exercise regime parameters and monitor patient adherence. This emerging technology has the potential to greatly improve rehabilitation outcomes for individuals completing in-home gaze stabilization exercises.

Background and Purpose: The purpose of this study was to determine whether the addition of gaze stability exercises to balance rehabilitation would lead to greater improvements of symptoms and postural stability in older adults with normal vestibular function who reported dizziness., Methods: Participants who were referred to outpatient physical therapy for dizziness were randomly assigned to the gaze stabilization (GS) group (n = 20) or control (CON) group (n = 19). Dizziness was defined as symptoms of unsteadiness, spinning, a sense of movement, or lightheadedness. Participants were evaluated at baseline and discharge on symptoms, balance confidence, visual acuity during head movement, balance, and gait measures. The GS group performed vestibular adaptation and substitution exercises designed to improve gaze stability, and the CON group performed placebo eye exercises designed to be vestibular neutral. In addition, both groups performed balance and gait exercises., Results: There were no baseline differences (P > .05) between the GS and CON groups in age, sex, affect, physical activity level, or any outcome measures. Both groups improved significantly in all outcome measures with the exception of perceived disequilibrium. However, there was a significant interaction for fall risk as measured by Dynamic Gait Index (P = .026) such that the GS group demonstrated a significantly greater reduction in fall risk compared with the CON group (90% of the GS group demonstrated a clinically significant improvement in fall risk versus 50% of the CON group)., Discussion and Conclusions: This study provides evidence that in older adults with symptoms of dizziness and no documented vestibular deficits, the addition of vestibular-specific gaze stability exercises to standard balance rehabilitation results in greater reduction in fall risk.

Objective: To determine the effect of vestibular exercises on the recovery of visual acuity during head movement in patients with bilateral vestibular hypofunction (BVH)., Design: Prospective, randomized, double-blinded study., Setting: Outpatient clinic, academic setting., Patients: Thirteen patients with BVH, aged 47 to 73 years., Intervention: One group (8 patients) performed vestibular exercises designed to enhance remaining vestibular function, and the other (5 patients) performed placebo exercises., Main Outcome Measures: Measurements of dynamic visual acuity (DVA) during predictable head movements using a computerized test; measurement of intensity of oscillopsia using a visual analog scale., Results: As a group, patients who performed vestibular exercises showed a significant improvement in DVA (P = .001), whereas those performing placebo exercises did not (P = .07). Only type of exercise (ie, vestibular vs placebo) was significantly correlated with change in DVA. Other factors examined, including age, time from onset, initial DVA, and complaints of oscillopsia and disequilibrium, were not significantly correlated with change in DVA. Change in oscillopsia did not correlate with change in DVA., Conclusions: Use of vestibular exercises is the main factor involved in recovery of DVA in patients with BVH. We theorize that exercises may foster the use of centrally programmed eye movements that could substitute for the vestibulo-ocular reflex., Trial Registration: clinicaltrials.gov Identifier: NCT00411216.

Objective: To determine the effect of vestibular rehabilitation on reduction of fall risk in individuals with unilateral vestibular hypofunction and to identify those factors that predict fall risk reduction., Study Design: Retrospective chart review., Setting: Tertiary referral center., Patients: Forty-seven patients with unilateral vestibular hypofunction, aged 28 to 86 years, who were at risk for falls on initial assessment., Intervention: All patients underwent vestibular rehabilitation including adaptation exercises, designed to improve gaze stability, and gait and balance exercises., Main Outcome Measures: Fall risk (Dynamic Gait Index), visual acuity during head movements (Dynamic Visual Acuity), and subjective complaints were measured initially, at 2-week intervals, and at completion of physical therapy., Results: As a group, the patients had significantly reduced risk for falls (p <0.001) after rehabilitation. Time from onset of symptoms did not affect the efficacy of vestibular rehabilitation. Both older (> or = 65 yr) and younger (< 65 yr) adults showed significant reductions in fall risk with vestibular rehabilitation (p <0.001). However, a significantly greater proportion (Chi2= 0.016) of older adults remained at risk for falls at discharge compared with young adults (45% versus 11%). Initial Dynamic Gait Index and Dynamic Visual Acuity scores predicted fall risk reduction in patients with unilateral vestibular hypofunction. A model was developed using initial Dynamic Gait Index and Dynamic Visual Acuity scores to predict fall risk reduction., Conclusions: Vestibular rehabilitation is effective in significantly reducing fall risk in individuals with unilateral vestibular deficit. The model predicts fall risk reduction with good sensitivity (77%) and specificity (90%).

Background and Purpose: The head thrust test (HTT) is used to assess the vestibulo-ocular reflex. Sensitivity and specificity for diagnosing unilateral vestibular hypofunction (UVH) in patients following vestibular ablation is excellent (100%), although sensitivity is lower (35%-39%) for patients with nonsurgically induced UVH. The variability of the test results may be from moving the subject's head outside the plane of the lateral semicircular canals as well as using a head thrust of predictable timing and direction. The purpose of this study was to examine sensitivity and specificity of the horizontal HTT in identifying patients with UVH and bilateral vestibular hypofunction (BVH) when the head was flexed 30 degrees in attempt to induce acceleration primarily in the lateral semicircular canal and the head was moved unpredictably., Subjects: The medical records of 176 people with and without vestibular dysfunction (n=79 with UVH, n=32 with BVH, and n=65 with nonvestibular dizziness) were studied., Methods: Data were retrospectively tabulated from a de-identified database (ie, with health information stripped of all identifiers)., Results: Sensitivity of the HTT for identifying vestibular hypofunction was 71% for UVH and 84% for BVH. Specificity was 82%., Discussion and Conclusion: Ensuring the head is pitched 30 degrees down and thrust with an unpredictable timing and direction appears to improve sensitivity of the HTT.

Objective: To determine whether the cervico-ocular reflex contributes to gaze stability in patients with unilateral vestibular hypofunction., Study Design: Prospective study., Setting: Tertiary referral center., Patients: Patients with unilateral vestibular hypofunction (n = 3) before and after vestibular rehabilitation and healthy subjects (n = 7)., Interventions: Vestibular rehabilitation., Main Outcome Measures: We measured the cervico-ocular reflex in patients with unilateral vestibular hypofunction before and after vestibular rehabilitation and in healthy subjects. To measure the cervico-ocular reflex, we recorded eye movements with a scleral search coil while the trunk moved at 0.3, 1.0, and 1.5 Hz beneath a stabilized head. To determine whether the head was truly stabilized, we measured head movement using a search coil., Results: We found no evidence of cervico-ocular reflex in any of the seven healthy subjects or in two of the patients with unilateral vestibular hypofunction. In one patient with chronic unilateral vestibular hypofunction, the cervico-ocular reflex was present before vestibular rehabilitation only for leftward trunk rotation (relative head rotation toward the intact side). After 5 weeks of placebo exercises, there was no change in the cervico-ocular reflex. After an additional 5 weeks that included vestibular exercises, cervico-ocular reflex gain for leftward trunk rotation had increased threefold. In addition, there was now evidence of a cervico-ocular reflex for rightward trunk rotation, potentially compensating for the vestibular deficit., Conclusion: The cervico-ocular reflex appears to be a highly inconsistent mechanism. The change of the cervico-ocular reflex in one patient after vestibular exercises suggests that the cervico-ocular reflex may be adaptable in some patients.

Objective: To determine the effect of vestibular exercises on the recovery of visual acuity during head movement in patients with unilateral vestibular hypofunction., Study Design: Prospective, randomized, double-blind study., Setting: Ambulatory referral center., Patients: Twenty-one patients with unilateral vestibular hypofunction, aged 20 to 86 years., Intervention: One group (13 patients) performed vestibular exercises designed to enhance the vestibulo-ocular reflex, and the other group (8 patients) performed placebo exercises. The placebo group was switched to vestibular exercises after 4 weeks., Outcome Measures: Measurements of dynamic visual acuity (DVA) during predictable (DVA-predictable) and unpredictable (DVA-unpredictable) head movements by means of a computerized test and measurement of intensity of oscillopsia by means of a visual analog scale., Results: As a group, patients who performed vestibular exercises showed a significant improvement in DVA-predictable (P<.001) and DVA-unpredictable (P<.001), while those performing placebo exercises did not (P =.07). On the basis of stepwise regression analysis, the leading factor contributing to improvement was vestibular exercises. This reached significance for DVA-predictable (P =.009) but not DVA-unpredictable (P =.11). Other factors examined included age, time from onset, initial DVA, oscillopsia, and duration of treatment. Changes in oscillopsia did not correlate with DVA-predictable or DVA-unpredictable., Conclusions: Use of vestibular exercises is the main factor involved in recovery of DVA-predictable and DVA-unpredictable in patients with unilateral vestibular hypofunction. Exercises may foster the use of centrally programmed eye movements that could substitute for the vestibulo-ocular reflex. The DVA-predictable would benefit more from this than would DVA-unpredictable.

Objective: This study was designed to measure visual acuity during active vertical head movement and to examine its relationship to subjective reports of oscillopsia., Study Design: This was a prospective, clinical study., Setting: The study was performed in a tertiary, ambulatory referral center., Patients: Thirty normal subjects, 13 patients with unilateral vestibular hypofunction, 11 patients with bilateral vestibular loss, and 10 patients with nonvestibular dizziness were examined. Vestibular loss was confirmed with caloric or rotary chair testing., Intervention: Diagnostic., Main Outcome Measure: Reliability, sensitivity, and specificity of a computerized test that measures visual acuity during active vertical head movement. Subjective complaint of oscillopsia was measured by use of a visual analog scale., Results: The active vertical head movement test was reliable both for normal subjects (intraclass correlation coefficient, r = 0.89) and for patients with dizziness (intraclass correlation coefficient, r = 0.94). Age contributed significantly to active vertical head movement in normal subjects and in patients with dizziness over the age of 46 years but not in younger subjects. Older subjects had a decrement in active vertical head movement compared with younger subjects. Subjective reports of oscillopsia did not correlate positively with active vertical head movement., Conclusion: The active vertical head movement test is a reliable measure of visual acuity during active vertical head motion. The effect of age on active vertical head movement may reflect the physiologic impact of neuronal loss with aging. The poor correlation between active vertical head movement and reports of oscillopsia may be caused by the predictability of head movements during the active vertical head movement test compared with the unpredictability of head movements during walking.

Identification of fall risk for patients with known vestibular hypofunction is important because it affects the management and the level of independence of these patients. Patients with bilateral vestibular loss, overall, have a greater incidence of falls than the general community-dwelling population over the age of 65 years. In younger patients, the incidence of falls may be related to severity of vestibular loss and to overconfidence or a lack of caution in activities. Preliminary reports suggest that vestibular rehabilitation can reduce the fall risk in patients with vestibular loss.

Objective: To determine the contribution of central preprogramming of eye movements to dynamic visual acuity (DVA) during head movement in patients with vestibular hypofunction., Study Design: Prospective, clinical study., Setting: Tertiary care, academic hospitals., Participants: Twenty-six healthy subjects and 20 patients with unilateral (UVL) and 7 with bilateral vestibular loss (BVL) (age range, 20-86 years)., Interventions: Diagnostic interventions, including caloric and rotational chair testing., Main Outcome Measure: Measurements of DVA during predictable (DVA-predictable) and unpredictable (DVA-unpredictable) head movements using a computerized test., Results: There was a difference between DVA-predictable and DVA-unpredictable scores in all groups (P<.02). The difference between DVA-predictable and DVA-unpredictable scores for the BVL group was significantly greater than that for the other groups (P<.005). Age was a significant factor in DVA-unpredictable scores for the healthy subjects (P<.001) and UVL group (P<.02). Comparisons of DVA between groups were significant (P<.03), with the following exceptions: UVL group for head movements toward the unaffected side for DVA-predictable and DVA-unpredictable scores, compared with healthy subjects, and UVL group for head movements toward the affected side for DVA-predictable scores, compared with the BVL group., Conclusions: Unpredictable head movements cause a greater decrement in visual acuity than do predictable head movements. This suggests that central programming of eye movements and/or efference copy contributes to gaze stability during predictable head movements in healthy subjects and patients with vestibular hypofunction. Patients with BVL use central programming of eye movements to maintain gaze stability more than do healthy subjects or patients with UVL.

Objective: To determine to what extent patients with vestibular hypofunction experience falls., Study Design: Prospective clinical study., Setting: Outpatient tertiary care facility in a university., Patients: Patients with unilateral (n = 70) and bilateral (n = 45) vestibular hypofunction, confirmed on vestibular function testing, aged 24 to 89 years., Intervention: None., Main Outcome Measure: Incidence of falls., Results: There was a significant difference in the incidence of falls reported since the onset of the vestibular deficit by patients with unilateral (UVL) and bilateral (BVL) vestibular hypofunction. The incidence of falls for BVL was significantly greater than that for UVL. The incidence of falls for UVL was not different from that expected in a community-based population when age was considered. The incidence of falls for BVL was significantly greater than that reported for the general population aged 65 through 74 years (51.1% for BVL, 25% for community-dwelling individuals) but was significantly less than expected for persons aged > or =75 years (18.2% for BVL, 49% for community-dwelling individuals). The lower incidence of falls in patients with BVL aged > or =75 years may be related to the use of assistive devices and to a decrease in risky behavior. All patients with serious injury were from the UVL group, and all were >65 years old. The incidence of fall-related injuries requiring medical attention among patients with UVL was similar to that in community-dwelling individuals., Conclusions: Falls are an important consequence of bilateral vestibular hypofunction, and patients should be counseled about the increased risk of falling. Assistive devices should be considered, especially for persons aged >65 years with BVL.

Objective: Patients with benign paroxysmal positional vertigo (BPPV) often experience postural instability as well as brief episodes of vertigo. The purpose of this study was to determine whether successful resolution of the episodic vertigo, through use of the canalith repositioning treatment, would be accompanied by improvement in postural stability., Study Design: Prospective clinical study., Setting: Outpatient tertiary care facility in a university., Patients: Thirty-three patients with a diagnosis of the canalithiasis form of BPPV affecting the posterior canal unilaterally. All patients had complete remission of the positional vertigo after treatment. Patients with abnormal caloric or rotary chair test results were excluded from the study., Intervention: The posterior canal BPPV was treated by the canalith repositioning treatment., Main Outcome Measures: Postural stability was assessed by computerized dynamic posturography before and 1 to 2 weeks after treatment. Six different subtests were used., Results: A significant number of patients had abnormal stability, as measured with computerized dynamic posturography, before treatment. After treatment there was a significant increase in the number of subjects with normal results on the different subtests; however, not all patients had normal postural stability. Younger subjects were more likely to show improved stability., Conclusions: Treatment of BPPV using the canalith repositioning treatment results in improved postural stability in patients with BPPV. Not all patients have normal stability after treatment, however, and assessment and treatment of the balance problems may be necessary.

Since the initial introduction of exercises as a treatment for patients with vestibular deficits, there have been numerous clinical reports on the benefits of treatment. Clinical reports, however, are of limited use as a basis for treatment because, without a control group, they offer only interesting descriptions of the patient populations. Fortunately, several prospective, randomized studies on the treatment of patients with vestibular hypofunction or with benign paroxysmal positional vertigo have been published recently, adding to the small number of previous publications. This review will examine the information provided by those studies. Advances in the use of outcome measures, assessment of otolith function and treatment of related balance problems are also presented.

Purpose: Modern immunosuppressants have improved the success of kidney transplantation for renal failure patients. They also may induce neurotoxic effects including tremor. We report two cases of pseudonystagmus and oscillopsia in transplant patients caused by immunosuppressant-induced head tremor and gentamicin-induced vestibulotoxicity., Methods: Case reports. Head tremor, static visual acuity, and dynamic visual acuity were measured. Vestibular function was evaluated with ice water calorics., Results: Both patients had significant head tremor and pseudonystagmus. Head stabilization improved static visual acuity. Dynamic visual acuity revealed a 4-line and 10-line loss of visual acuity, respectively., Conclusions: These findings of pseudonystagmus and oscillopsia are likely to become more prevalent as more renal failure patients receive transplants. Improvement may be seen with reduction of immunosuppressant, reduction of stimulant intake, use of medications to reduce head tremor, and vestibular rehabilitation.

Benign paroxysmal positional vertigo (BPPV) is one of the most common and treatable causes of vertigo. We examined BPPV types and the effectiveness of physical therapy in each type. BPPV is caused by a utricular statoconium that blocks the semicircular canal. Statoconia can block any of the semicircular canals, but they generally affects the posterior canal. Diagnosis is based on a typical history and characteristic eye movements elicited by the Dix-Hallpike test. Treatment involves a physical maneuver designed to mobilize the free calcium particles from the semicircular canal to the utricle. Canalith repositioning is the mainstay of treatment. The maneuver is illustrated in detail and other forms of treatment and their indications are discussed.

Objective: The study was designed to measure dynamic visual acuity (DVA) during head movement as an assessment of the functional impact of vestibular deficits., Study Design: The study design was a prospective, clinical study., Setting: The study was performed in a tertiary, ambulatory referral center., Patients: Forty-two normal subjects, 29 patients with unilateral vestibular loss, and 26 patients with bilateral vestibular hypofunction who were 19-87 years of age were examined., Intervention: Diagnostic intervention was performed., Main Outcome Measure: Main outcome measures included the reliability, sensitivity, and specificity of a computerized test that measures visual acuity during head movement in normal subjects and in patients with vestibular deficits., Results: The computerized DVA test was reliable in both normal subjects (intraclass correlation coefficient [ICC] r=0.87) and in patients with vestibular deficits (ICC r=0.83). The sensitivity of the DVA test was 94.5% and the specificity was 95.2%. The positive predictive value (individuals who test positive on the DVA test who will have a vestibular deficit) was 96.3%. The negative predictive value (individuals who test negative on the DVA test who will not have a vestibular deficit) was 93%., Conclusions: The computerized DVA test is reliable and is able to distinguish among normal subjects and patients with vestibular deficits.

Recovery of gaze and postural stability in human beings with vestibular deficits is well documented. The mechanisms that contribute to this recovery form the basis for the exercises used in the rehabilitation of these patients. These mechanisms include the central preprogramming of eye movements and of postural responses, the potentiation of the cervico-ocular reflex, modification of saccadic eye movements, and the substitution of visual and somatosensory cues for the lost vestibular cues. The mechanism most successful in contributing to recovery, however, is probably adaptation of the vestibular system itself. Understanding the various compensatory mechanisms and their limitations for improving gaze and postural stability should lead to more effective treatment of these patients.

Computerized dynamic platform posturography is defined in this technology assessment. The review discusses what computerized dynamic platform posturography measures, what the reliability and validity of the information are, and the uniqueness of the information provided. The clinical contribution and indications for testing are discussed. There are comments on future directions for research on computerized dynamic platform posturography and a summary and conclusion.

This article discusses the pathophysiology, evidence of treatment efficacy, and factors that contribute to improved treatment outcome in three different vestibular disorders. In patients with unilateral and bilateral vestibular loss, recent research suggests that customized, supervised exercises facilitate recovery of postural stability. These exercises are based on knowledge of normal vestibular function as well as on our understanding of the various compensatory mechanisms that can contribute to recovery. Recognizing the limitations of these compensatory mechanisms as substitutes for lost vestibular function is important in establishing treatment goals. Treatment of patients with benign paroxysmal positional vertigo (BPPV) is based on the identification of the specific canal involved and the anatomy of the labyrinth. Although patients with BPPV primarily experience brief episodes of vertigo, this disorder is also associated with postural instability, which may not resolve with remission of the positional vertigo.

We have examined to what extent the vertical semicircular canals contribute to the nonlinearity of the horizontal VOR imposed by the driving of primary vestibular afferents into inhibitory cutoff at high velocities of head rotation (Ewald's second law). The gain (eye velocity/head velocity) of the horizontal component of the VOR with the head pitched down 30 degrees and pitched up 30 degrees was examined during constant-velocity rotations in normal subjects and patients following unilateral vestibular nerve section. In normal subjects, VOR gain decreases as chair velocity increases from 60-300 degrees/s when the head is pitched up, but VOR gain remains constant when the head is pitched down. This finding implies that the mechanism by which the gain of the horizontal VOR gain remains constant at all velocities of rotation depends upon the pattern of labyrinthine stimulation. Following unilateral nerve section, we found that the directional preponderance (DP) in horizontal VOR depends upon whether the head is pitched up 30 (mean asymmetry = 5%) or pitched down 30 degrees (mean asymmetry = 20%). This is what is expected based on the degree to which the lateral and vertical semicircular canals sense horizontal head acceleration with the head in different degrees of pitch. Hence, following unilateral vestibular lesions, the DP of horizontal VOR gain is most easily elicited at high velocities of head rotation and with the head pitched down 30 degrees. Evidence for DP at the bedside using the "head-shaking nystagmus" technique may be optimally elicited with the head pitched down 30 degrees.

Purpose: To determine whether people with central visual field loss (CFL) show a smaller visual contribution to posture stabilization than people with normal vision and to determine the visual factors that predict the magnitude of visual stabilization in people with central visual field loss., Methods: Posture information was recorded in 19 subjects with CFL and in 20 subjects with normal vision. Data were collected as the subject stood in a dark environment and also as he or she viewed a stationary visual display. In both conditions, somatosensory feedback was concurrently altered. The central visual fields of the subjects with CFL were measured by static perimetry with the confocal scanning laser ophthalmoscope. Binocular visual acuity and contrast sensitivity were measured on all subjects using the ETDRS and Pelli-Robson charts, respectively. Image-displacement thresholds were measured in a subset of the subjects., Results: On average, subjects with central field loss showed a smaller visual contribution to posture stabilization than subjects with normal vision. The reduction in sway caused by visual stimuli was only 29% for the subjects with CFL compared to 41% for the subjects with normal vision. Displacement thresholds accounted for 45% of the variance in the visual stabilization magnitude of the subjects with CFL. No other visual factor significantly increased the coefficient of determination., Conclusions: The visual self-motion cues generated by small body oscillations may be undetectable and, thus, unusable as cues to postural sway by people with central field loss.

Objective: To describe the conversion of benign paroxysmal positional vertigo involving the posterior canal into benign paroxysmal positional vertigo involving the anterior or horizontal canals after treatment using the canalith repositioning maneuver., Design: Retrospective study of outcome., Setting: Outpatient clinic., Patients: Consecutive sample of 85 patients diagnosed as having benign paroxysmal positional vertigo affecting the posterior canal. Identification of posterior canal involvement was based on the observation of the direction of the vertical component of nystagmus after the Hallpike-Dix maneuver., Intervention: Canalith repositioning maneuver., Main Outcome Measure: Eye movements were observed about 1 week after the treatment. The direction of nystagmus elicited after movement of the patient into the Hallpike-Dix position indicated which canal was involved in the patients who had not responded to treatment., Results: Of the 85 patients studied who originally had posterior canal benign paroxysmal positional vertigo, five (6%) had anterior canal (n=2) or horizontal canal (n=3) positional vertigo after undergoing this maneuver., Conclusion: Careful observation of the direction of the nystagmus is necessary for correct identification of which canal is involved in patients who do not respond to the initial treatment using the canalith repositioning maneuver.

The use of exercises in the treatment of patients with vestibular deficits has become increasingly popular, and evidence exists that these exercises are beneficial in patients with chronic vestibular deficits. The question as to whether patients with acute unilateral vestibular loss would benefit from vestibular adaptation exercises is particularly compelling, however, because animal studies have demonstrated that the acute stage after unilateral vestibular loss is a critical period for recovery. Deprivation of visuomotor experience during that period can delay the onset of recovery as well as prolong the recovery period. Patients often avoid movement during the early stage because, with movement, they experience an increase in dysequilibrium and nausea. We examined the recovery of postural stability in patients during the acute stage after resection of acoustic neuroma to determine whether vestibular adaptation exercises facilitate the onset of recovery and improve the rate of recovery. The results suggest that vestibular adaptation exercises result in improved postural stability and in a diminished perception of dysequilibrium.

Background: Postural instability is one of the important contributors to falling in observers aged 65 years and older. In this study we examine the role of vision in the relation between postural stability and falling, as well as in the relation between postural stability and the fear of falling., Methods: Community-dwelling adults 65 years and older were administered a questionnaire about their history of falls and fear of falling (N = 185). Postural sway was measured in the same subjects with eyes open and eyes closed. Visual function was assessed by measures of visual acuity and contrast sensitivity., Results: The 29 subjects who reported falling in the last year showed less of a visual contribution to posture stabilization than those who reported no falls. Controlling for age and gender, there is a 2.13-fold increase in the likelihood of reporting falling for a 0.1 decrement in the visual stabilization index when it is measured within the context of reliable somatosensory feedback. Those who reported a fear of falling and those who reported no fear showed similar visual stabilization. Contrast sensitivity was significantly associated with visual stabilization when it was measured within the context of reliable somatosensory feedback., Conclusions: The visual contribution to postural stabilization is significantly greater in nonfallers compared to fallers, and it is significantly associated with contrast sensitivity.

Previous reports have indicated that optokinetic afternystagmus (OKAN) becomes asymmetric after the occurrence of unilateral peripheral vestibular lesions, and suggested that OKAN may be used for localizing the side of the lesion. These studies did not take into account spontaneous nystagmus. We compared OKAN in 12 subjects with unilateral vestibular loss after resection of acoustic neuroma to OKAN in 30 normal subjects. After offsetting the data for spontaneous nystagmus, we calculated the initial amplitude, the time constant, and the slow-phase cumulative eye position (SCEP) parameters of OKAN. The directional asymmetry of parameters to rightward and leftward stimulation were also calculated. The mean SCEP, initial amplitude, and time constant parameters were reduced significantly in the patients, and each also showed a directional asymmetry, such that they were greater for stimulation toward the side of the lesion. The directional preponderance of the SCEP parameter had the highest sensitivity for the side of the lesion, being abnormally elevated in 58.3% of patients with unilateral loss. We conclude that OKAN might be useful in combination with other subtests of a battery, but that by itself OKAN is only moderately sensitive to unilateral peripheral vestibular loss.

Postural stability in patients with bilateral vestibular deficits from aminoglycoside toxicity was characterized by examining their ability to use different sensory cues to maintain balance and by recording their automatic postural responses to sudden translational and rotational (pitch) perturbations of the support surface. We found our patients had increased sway on sensory tests in which either visual or somatosensory cues were altered and were unable to maintain their balance when both visual and somatosensory cues were altered compared to age-matched normal subjects. The amount of vestibular loss, as inferred from the VOR Tc, accounted for a significant amount of A-P sway on test 4 in which somatosensory cues were altered. The frequency response of anterior-posterior sway in the BVL group suggests that they use more hip movements than do normal subjects to maintain postural stability. The responses of BVL patients to sudden translations of the support surface did not differ from those of normal subjects. More BVL patients lost their balance, however, on the initial trial of the toes-up rotational perturbation of the support surface than did normal subjects.

Purpose: To investigate the relationship between retinitis pigmentosa (RP) progression and the visual contribution to posture stabilization; to examine the extent to which visual-field diameter affects the visual contribution to posture stabilization., Methods: Posture information was recorded in 35 subjects with well-characterized RP and in 20 subjects with normal vision. Data were collected as each subject stood in a dark environment and as each subject viewed a stationary visual display. In both conditions, somatosensory feedback was concurrently altered. Data were also collected on 10 additional subjects with normal vision wearing field-restricting goggles (visual-field diameters ranged from 26.5 down to 6 degrees)., Results: RP progression is accompanied by a steady decrease of the visual stabilization of posture, from normal values at the onset of the disease to the absence of visual stabilization and, eventually, to visual destabilization of posture. Decreasing visual field diameter in the subject with normal vision resulted in a linear decrease of the visual stabilization of posture. However, subjects with RP with comparable visual-field loss showed significantly lower visual stabilization than normal subjects with artificially restricted fields. Moreover, subjects with normal vision with restricted visual fields as small as 6 degrees failed to show visual destabilization of posture., Conclusions: Most likely, the additional reduction in the visual stabilization of posture shown in subjects with RP, as well as the visual destabilizing effect manifest in the late stages of RP, is caused by anomalous processing of visual information in the remaining visual field.

Objective: To determine the effectiveness of two different physical therapy approaches for benign paroxysmal positional vertigo., Design: Randomized study., Setting: Outpatient clinic., Patients: Consecutive sample of 60 patients with benign paroxysmal positional vertigo., Intervention: Patients received either a single treatment based on the hypothesis that the vertigo and nystagmus of benign paroxysmal positional vertigo are due to debris adhering to the cupula of the posterior semicircular canal (cupulolithiasis) or a single treatment based on the hypothesis that the debris is free floating in the long arm of the posterior canal (canalithiasis). Patients were reevaluated 1 to 2 weeks after the treatment and again 4 to 6 months later., Outcome: Treatment outcome was classified as either asymptomatic, more than 70% improved as rated by the patient, or no change., Results: The treatment designed for cupulolithaisis resulted in remission of vertigo and nystagmus in 70% of the patients and in improvement of the symptoms in another 20%. The treatment designed for canalithiasis resulted in remission of vertigo and nystagmus in 57% of the patients and in improvement in another 33%. There was no statistically significant difference between treatments., Conclusions: These single-treatment approaches are equally effective treatments for benign paroxysmal positional vertigo. Further studies are needed to look at the long-term effectiveness of these treatments.

Vestibular rehabilitation is based on the use of adaptive and compensatory mechanisms already existing in the human brain. Research using animals provides a great deal of information on the neural mechanisms responsible for these functions and suggests strategies that should be helpful in rehabilitation of patients with disequilibrium and balance disorders. Research in animals and human beings suggests that rehabilitation should be specifically designed, depending on the patients' deficits. It also suggests that to be effective it needs to be started soon after impairment and that vestibulosuppressive medication may reduce recovery. Studies are now underway to evaluate the effectiveness of vestibular rehabilitation on several groups of patients and to answer some fundamental questions about the mechanisms and the effectiveness of these treatment methods. Current information suggests that vestibular rehabilitation is an effective method of therapy for many patients with disequilibrium and balance disorders and that for some patients it is the best therapy available.

We characterized postural stability in patients with Huntington's disease (HD) by examining their ability to use different sensory cues to maintain balance and by recording their automatic postural responses to externally applied perturbations. Our HD patients, like normal subjects, depended more on proprioceptive than on visual cues to maintain balance. HD patients, however, developed more sway than normal subjects when proprioceptive cues, or when proprioceptive cues and vision, were altered. Thus, HD patients showed a defect in using vestibular information alone to maintain normal postural stability. The onset of compensatory motor responses in the lower extremities following sudden translations of the support surface was delayed by 30 to 60 msec in HD patients as compared with normal subjects. HD patients also had more sway and falls during unexpected rotations of the support surface, although they could appropriately reduce their motor responses on the next trial.

To understand to what extent visual-pattern deprivation during infancy results in strabismus and nystagmus, the authors examined the long-term consequences of this type of deprivation in monkeys during the first 50 days of life. Three cynomolgus and three rhesus monkeys had the eyelids sutured closed within 24 hr of birth. At 25 days of age, the eyelids were opened, and the eyelids of the fellow eye were sutured closed for an additional 25 days (reverse-eyelid suture). When the eyelids were opened at 50 days of age, each monkey was found to have 20-30 delta of exotropia and nystagmus, which persisted for the duration of the study (1 yr). The cynomolgus monkeys developed a monocular 8-10 Hz pendular nystagmus in the eye sutured first. The rhesus monkeys developed a conjugate nystagmus with both jerk and pendular components. The slow phases often had velocity-increasing profiles. The rhesus monkeys also had a superimposed latent component to the nystagmus found during monocular viewing. One additional rhesus monkey was examined after 55 days of binocular-eyelid suturing. This monkey also developed exotropia and nystagmus resembling that of the other rhesus monkeys. These findings suggest that early pattern vision in monkeys is necessary for the development of normal ocular alignment and gaze-holding ability.