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Biomedical subjects

R D Yee

Publications and source records attributed to R D Yee.

At least 37 records · Page 2Linked to original sources
PubMed1994

Current practices for monitoring ocular toxicity related to hydroxychloroquine (Plaquenil) therapy.

OBJECTIVE: Growing interest in aggressive early management of rheumatoid arthritis (RA) with hydroxychloroquine (alone or in combination with other immunomodulating drugs) is reason to review current practices for monitoring ocular toxicity in patients who take antimalarial therapy. METHODS: We surveyed by mail all ophthalmologists and rheumatologists in the State of Indiana about their practices in this regard. RESULTS: Twenty-nine of 31 rheumatologists (94%) responded. All but one recommended ophthalmologic examinations every 6 months and 41% would leave the choice of testing procedures to the ophthalmologist. Fifty percent had discontinued hydroxychloroquine because of a patient's failure to make and/or keep an appointment with the ophthalmologist. Of 213 ophthalmologists surveyed, 150 (70%) responded. Seventy-nine percent recommended semiannual examinations. Funduscopy, visual acuity, and color vision tests were reported to be performed routinely. Eleven of 13 retina specialists (85%), but only 25% of 127 general ophthalmologists, would obtain macular photographs (p < 0.001). Forty-two percent of general ophthalmologists, compared with 8% of retina specialists, would perform computerized perimetry (p < 0.001). Recognition of retinal hyperpigmentation as a classic sign was surprisingly low in both groups. Concurrent review of the medical records of 24 patients with RA or systemic lupus erythematosus showed extremely variable followup intervals for ophthalmologic examination; 7 of the 24 patients had no record of an ophthalmologic evaluation. CONCLUSION: As interest in the early, aggressive management of RA continues to grow, significant education needs to be devoted to the monitoring and diagnosis of ocular toxicity of hydroxychloroquine by both rheumatologists and ophthalmologists.

Adult↗
PubMed1993

Visual loss and performance in blind athletes.

We examined the relationship between visual loss and athletic performance and evaluated the visual classification system used in the 1988 United States Association of Blind Athletes (USABA) Summer Games. Athletes were asked about their age, sex, training, years of participation in organized competition, age at onset of blindness and were given an ophthalmologic exam that included Snellen acuity, contrast sensitivity, and visual fields. In the speed track events, visual class,* sex, age, hours of training, and years participating were found to have a positive correlation with performance. Visual class and sex were significant predictors of performance in the intermediate distance events; visual class was the only significant predictor of performance in the long distance events. Visual class, sex, age, and hours of training were correlated with performance in the track and field (throwing) events. Weightlifting performance was influenced by age and sex. The most consistent predictor of performance in the swimming events was the number of hours training per week. Our results indicate that the current classification system for visual loss is useful for grouping athletes for competition.

Blindness↗
PubMed1992

Abnormal eye movements in Gerstmann-Sträussler-Scheinker disease.

Gerstmann-Sträussler-Scheinker disease is a familial disorder of progressive ataxia and dementia in adulthood with extrapyramidal signs in some families. Neuro-ophthalmic examinations and eye movement recordings were performed in members of a large Indiana kindred. Five affected members and 11 members at risk were studied. Eye movements were recorded with videotape, electro-oculography, and/or magnetic scleral search coil. All affected members had abnormal eye movements characteristic of extrapyramidal diseases and cerebellar disorders. Nine members at risk had normal eye movements, but two others had slightly abnormal eye movements. Neuro-ophthalmic examination and eye movement recordings might be helpful in detecting early signs of Gerstmann-Sträussler-Scheinker disease in persons at risk.

Adolescent↗
PubMed1991

Analysis of electro-oculographic artifact during vertical saccadic eye movements.

The analysis of vertical saccades by electrooculography (EOG) is limited by the presence of waveform artifacts that occur with both upward and downward saccades. The artifacts have been shown to increase the calculated velocities of upward saccades. For better evaluation of the nature of these artifacts, voluntary vertical saccades were recorded by EOG and magnetic search coil in five normal subjects and by EOG only in two patients who had previously undergone enucleation. All subjects demonstrated peaked EOG artifacts during vertical saccades. The amplitude of these artifacts was decreased but not completely eliminated by eyelid or eyeball fixation during the attempted saccade. Peak saccadic velocities were also decreased by eyelid fixation, but EOG measurements were generally less accurate than those obtained by search coil. There is evidence that these artifacts may be the result of a combination of eyelid electrical activity and resistance effects.

Electrooculography↗
PubMed1991

Electrooculography and discriminant analysis in Duane's syndrome and sixth-cranial-nerve palsy.

Eye-movement recordings may be helpful in the differentiation of Duane's syndrome from sixth-cranial-nerve palsy. Voluntary horizontal saccades were recorded and quantitated by electrooculography in 18 patients with unilateral type I Duane's syndrome and in 25 patients with sixth-nerve palsy. When ranges of abduction were matched, the peak velocities of abducting saccades in affected eyes were decreased equally in both groups. However, the peak velocities of adducting saccades in sound eyes were slowed in patients with Duane's syndrome. Because the standard deviations in saccadic velocities are large, computer-based, stepwise discriminant analyses were performed to identify the variables that proved to be useful in differentiating the two disorders. By entering these variables into the discriminant functions that were created, we could distinguish Duane's syndrome from sixth-nerve palsy in a statistically significant manner.

Abducens Nerve↗
PubMed1991

Vertical saccades in superior oblique palsy.

Vertical saccadic velocities in 10 patients who had unilateral superior oblique muscle palsy and 14 normal subjects were measured with the magnetic scleral search coil. The authors sought to determine whether downward saccades in patients who had superior oblique palsy are slow. Peak velocities of 10 degrees and 20 degrees saccades performed in the superior and inferior fields of the orbit, and 10 degrees, 20 degrees, and 30 degrees saccades performed across the center of the orbit were recorded with the eye in center gaze, 30 degrees of adduction, and 30 degrees of abduction. Paired t-tests did not show statistically significant differences between upward and downward saccades in patients with superior oblique palsy; no effects of orbital field or position of horizontal gaze were found (P greater than 0.01). Comparison of similar saccades between normal subjects and patients with superior oblique palsy by two-sample t-tests did not show significant differences between the two groups (P greater than 0.01).

Adult↗
PubMed1990

Visual motion response properties of neurons in dorsolateral pontine nucleus of alert monkey.

1. In this study we sought to characterize the visual motion processing that exists in the dorsolateral pontine nucleus (DLPN) and make a comparison with the reported visual responses of the middle temporal (MT) and medial superior temporal (MST) areas of the monkey cerebral cortex. The DLPN is implicated as a component of the visuomotor interface involved with the regulation of smooth-pursuit eye movements, because it is a major terminus for afferents from MT and MST and also the source of efferents to cerebellar regions involved with eye-movement control. 2. Some DLPN cells were preferentially responsive to discrete (spot and bar) visual stimuli, or to large-field, random-dot pattern motion, or to both discrete and large-field visual motion. The results suggest differential input from localized regions of MT and MST. 3. The visual-motion responses of DLPN neurons were direction selective for 86% of the discrete visual responses and 95% of the large-field responses. Direction tuning bandwidths (full-width at 50% maximum response amplitude) averaged 107 degrees and 120 degrees for discrete and large-field visual motion responses, respectively. For the two visual response types, the direction index averaged 0.95 and 1.02, indicating that responses to stimuli moving in preferred directions were, on average, 20 and 50 times greater than responses to discrete or large-field stimulus movement in the opposite directions, respectively. 4. Most of the DLPN visual responses to movements of discrete visual stimuli exhibited increases in amplitude up to preferred retinal image speeds between 20 and 80 degrees/s, with an average preferred speed of 39 degrees/s. At higher speeds, the response amplitude of most units decreased, although a few units exhibited a broad saturation in response amplitude that was maintained up to at least 150 degrees/s before the response decreased. Over the range of speeds up to the preferred speeds, the sensitivity of DLPN neurons to discrete stimulus-related, retinal-image speed averaged 3.0 spikes/s per deg/s. The responses to large-field visual motion were less sensitive to retinal image speed and exhibited an average sensitivity of 1.4 spikes/s per deg/s before the visual response saturated. 5. DLPN and MT were quantitatively comparable with respect to degree of direction selectivity, retinal image speed tuning, and distribution of preferred speeds. Many DLPN receptive fields contained the fovea and were larger than those of MT and more like MST receptive fields in size.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Internuclear ophthalmoplegia in the Chiari type II malformation.

We describe 3 cases of Chiari type II malformation presenting with bilateral internuclear ophthalmoplegia (INO). Although prominent, the INO was not an isolated sign in any of the patients; superimposed abduction paresis was present in 2, and deficits in smooth pursuit, optokinetic nystagmus, and vestibulo-ocular responses were present in 3. Two had hydrocephalus: 1 was clinically unchanged without therapy after 5 years; the other did not improve with shunting. Findings in our 3 patients, along with the 4 previously reported, confirm that INO is 1 manifestation of widespread brainstem or cerebellar dysfunction. Its origin is probably multifactorial, related to hydrocephalus, vascular compromise, direct neuronal distortion, or congenital neural malformation.

Adult↗
PubMed1989

Gerstmann-Sträussler-Scheinker disease. I. Extending the clinical spectrum.

We present the clinical findings in affected members of a large kindred with Gerstmann-Sträussler-Scheinker disease. Sixty-four patients exhibited progressive ataxia, dementia, and parkinsonian features. Inheritance appears to be autosomal dominant. Impaired smooth-pursuit eye movements, defective short-term memory, clumsiness of the hands, and ataxia of gait develop in the late 30s to early 60s. Eye movement abnormalities are characteristic of cerebellar dysfunction. Dementia progresses gradually over several years. Later, rigidity and bradykinesia appear and, at this stage, there is often psychosis or severe depression with rapid weight loss. Death occurs in 6 months to 2 years after onset of rigidity. Magnetic resonance imaging in 2 affected individuals showed cerebellar atrophy. There is decreased T2 signal in the basal ganglia, consistent with iron deposition.

Adult↗
PubMed1989

Downbeat nystagmus: characteristics and localization of lesions.

Clinical examinations and eye movement recordings of 91 consecutive patients with DBN were analyzed to describe the characteristics of DBN and to localize the lesions producing this abnormality. Horizontal and vertical eye movement recordings were made with EOG and/or magnetic search coil. The most frequent causes were infarction, cerebellar and spinocerebellar degeneration syndromes, MS and developmental anomalies affecting the pons and cerebellum. Toxicity from anticonvulsant drugs probably caused nystagmus in a few patients. Clinical examinations, excluding electronic eye movement recordings, were used to localize lesions. Localizations included the cerebellum in 88% of the patients. However, localizations to structures outside of the cerebellum were made in several patients. The effects of DBN of gaze position, convergence, blockage of fixation, and positioning of the head and body were observed. Almost all patients had DBN in some position of gaze while sitting and fixating a distant target. A few patients demonstrated DBN only with convergence, in the dark, or with positioning of the head and body. Horizontal gaze increased DBN in most patients. The nystagmus slow components usually had constant-velocity or increasing-velocity waveforms. The effects of vertical gaze on DBN were variable. In general, statistically significant differences in the frequencies of these effects among the various causes and localizations of lesions were not found. Horizontal eye movements were electronically recorded in DBN patients, in a group of normal subjects, and in a group of patients with isolated cerebellar atrophy who did not have DBN. The pattern of abnormal horizontal eye movements characteristic of damage to the midline structures of the cerebellum (impaired pursuit, impaired OKN, and inability to suppress VOR) was found in almost all DBN patients (99%), including patients with lesions localized to structures outside the cerebellum by clinical examination. DBN is usually produced by lesions in the cerebellum that also damage pathways that control horizontal tracking and visual-vestibulo-ocular interactions.

Adolescent↗
PubMed1989

Spontaneous vertical nystagmus.

We reviewed the clinical and oculographic features of 106 patients with spontaneous vertical nystagmus evaluated at the UCLA Eye Movement Laboratories over the past 10 years. Downbeat nystagmus typically occurred with lesions involving the caudal midline cerebellum whereas upbeat nystagmus was most often associated with lesions of the central medulla. Since the vestibular systems is the main source of tonic input to the oculomotor neurons and since the up and down vestibulo-ocular pathways separate beginning at the level of the vestibular nuclei asymmetric involvement of these pathways can explain spontaneous vertical nystagmus.

Brain Diseases↗
PubMed1988

Ultralow vestibuloocular reflex time constants.

We report detailed oculomotor studies in 3 patients with central nervous system lesions and markedly decreased time constants (less than 2 seconds) of the vestibuloocular reflex (VOR). In 1 patient with Chiari type I malformation, serial measurements over 3 years documented a progressive decrease in the duration of postrotatory nystagmus (100 deg/sec steps, acceleration 140 deg/sec2) until finally there was no sustained nystagmus. At this time, the patient had no response to caloric stimulation or to sinusoidal rotation below 0.2 Hz but normal gain (peak slow-phase eye velocity/peak chair velocity) above 0.4 Hz (phase lead increased). Gaze holding, saccades, smooth pursuit, and optokinetic nystagmus were normal, but optokinetic-after-nystagmus disappeared. The other 2 patients (combined brainstem-cerebellar atrophy) had impaired gaze holding, abnormal smooth pursuit and optokinetic nystagmus, and absent optokinetic-after-nystagmus. VOR gain to step and high-frequency sinusoidal stimuli was increased. The neural mechanism that normally prolongs the VOR time constant may have reduced it in our patients.

Adult↗
PubMed1988

Eye movements induced by linear acceleration on a parallel swing.

1. Horizontal and vertical eye movements were induced in normal human subjects by sinusoidal linear acceleration on a parallel swing. The swing frequency was 0.3 Hz and the peak horizontal and vertical acceleration ranged from 0.17 to 0.48 and 0.03 to 0.34 g, respectively. Eye movements were recorded with the scleral search coil technique. 2. With the subjects seated in the dark to stimulate the otolith-ocular reflex, swing displacement along the interaural axis induced horizontal eye movements with a mean sensitivity to translation (ST) (peak eye velocity/peak swing velocity) of 3.8 to 4.7 degrees/m and a mean phase shift (eye velocity re swing velocity) of -152 to -160 degrees. Vertical eye movements had ST and phase values comparable to those of the horizontal eye movements. When the subjects sat facing forward so that the horizontal linear accelerations occurred in the occipitonasal axis, almost identical vertical but no consistent horizontal eye movements were induced. In each case the horizontal and vertical eye movements were proportional to the horizontal and vertical displacement of the swing. 3. With the subject seated in the light looking to an earth-fixed target (synergistic visual-vestibular interaction), the gain (peak eye velocity/peak target velocity) of induced eye movements was near 1, and the phase was compensatory (i.e., approximately -180 degrees) for all stimuli (even at target velocities at which the pursuit gain was less than 1). Subjects were able to suppress the otolith-ocular responses by fixating on a target attached to the swing. The ST decreased by an order of magnitude compared with measurements in the dark without a fixation target. 4. Subjects were able to augment the ST (horizontal and vertical) by imagining an earth-fixed target. Halving the distance of the imagined target approximately doubled the ST. 5. In two of three subjects tested, the ST measured with mental alerting in the dark adaptively increased (approximately doubled) after 20 min of continuous synergistic visual-vestibular interaction. The subject who did not show an adaptive increase in ST began with the highest value of the 10 normal subjects. 6. We conclude that during linear accelerations of the head the otolith signal is correctly interpreted as head movement and not rotation of the gravity vector. The otolith-ocular reflex interacts with the visual pursuit system to improve ocular stability during translational head movements.

Adult↗
PubMed1988

Periodic alternating nystagmus.

Horizontal jerk nystagmus is indicative of a disorder involving the vestibular system. Periodic alternating nystagmus is a form of spontaneous nystagmus with a specific pattern. It is identified by the presence of spontaneous nystagmus in the primary direction of gaze, which beats in one direction for 1 or 2 minutes, followed by a null period, and then reappearance of the nystagmus in the opposite direction for a similar length of time. It may be congenital or acquired, and may be seen in association with vestibular-cerebellar disease or loss of vision. Recent case reports indicate that some forms of periodic alternating nystagmus may respond favorably to baclofen therapy.

Baclofen↗
PubMed1988

A comparison of the dynamics of horizontal and vertical smooth pursuit in normal human subjects.

We compared horizontal and vertical smooth pursuit recorded with a scleral contact lens technique at multiple sinusoidal frequencies (0.2-1.6 Hz) and peak velocities (12.5-100 degrees.s-1) in 10 normal subjects. The gain was significantly higher (p less than 0.05) and the harmonic distortion significantly lower (p less than 0.05) for horizontal pursuit compared to vertical pursuit for all stimuli except the lowest frequency and peak velocity. Both horizontal and vertical pursuit exhibited a phase lag that was minimal at lower frequencies but reached a mean of about 37 degrees at 1.6 Hz. This difference between horizontal and vertical pursuit could be explained by current models of the smooth pursuit system if one postulates a lower saturation level of retinal error velocity for vertical pursuit compared to horizontal pursuit.

Adult↗
PubMed1988

Contact-lens correction of aphakic infants and children: early behavioral and VEP results.

We studied 11 infants and young children fitted with contact lenses for correction of unilateral or bilateral aphakia. The visual-acuity estimates obtained from behavioral cues (alternate-cover test and central-fixation monitoring) were compared with results obtained from pattern-reversal visual-evoked potentials (VEP). We conclude that VEP may be more sensitive than behavioral observation for monitoring the visual progress in certain aphakic children.

Aphakia↗