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Biomedical subjects

Ronald J Tusa

Publications and source records attributed to Ronald J Tusa.

6 recordsLinked to original sources
PubMed2003

Recovery of dynamic visual acuity in unilateral vestibular hypofunction.

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.

Adult↗
PubMed2003

Dizziness.

There are several causes of dizziness, each of which requires a different form of management. Virtually all causes of dizziness can be treated with medication, diet, or physical therapy. This article discusses the most common causes of dizziness and management. Case examples are used extensively.

Acute Disease↗
PubMed2002

Vertical dynamic visual acuity in normal subjects and patients with vestibular hypofunction.

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.

Adult↗
PubMed2002

Animal models for visual deprivation-induced strabismus and nystagmus.

The development of gaze-stabilizing systems depends on normal vision during infancy. Monkeys reared with binocular lid suture (BLS) for the first 25-40 days of life have strabismus, optokinetic nystagmus deficits, latent nystagmus, and decreased binocular cells in the visual cortex and nucleus of the optic tract. When BLS is extended to 55 days, pendular and congenital nystagmus also occurs. Eyelids in infant monkeys are hairless and thin, but BLS still degrades sensory fusion, motion, and form perception. To determine to what extent these visual properties are critical in the development of normal gaze stabilization, we examined infant monkeys reared with one opaque contact lens over one eye, alternated to the fellow eye every other day (AMO); and monkeys reared in a 3-Hz strobe environment. Monkeys reared with AMO develop strabismus, but have normal optokinetic nystagmus and no spontaneous nystagmus. Area 17 is monocular, but the medial temporal area and the nucleus of the optic tract are binocular. Monkeys reared in strobe light develop pendular nystagmus but not strabismus. We were puzzled by the results of the AMO monkeys until we examined infant monkeys with BLS that were prevented from seeing form through the lids. This was done by leaving the tarsal plate intact behind the eyelid. They developed similar to the AMO monkeys. These results suggest that disruption of sensory fusion during infancy (BLS, AMO) causes strabismus. If strabismus occurs while the monkeys have some form vision from each eye (BLS without tarsal plate), then the nucleus of the optic tract becomes monocular, which causes optokinetic nystagmus deficits and latent nystagmus. Infant monkeys reared without visual motion develop pendular nystagmus.

Animals↗