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Biomedical subjects

R D Yee

Publications and source records attributed to R D Yee.

At least 19 recordsLinked to original sources
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↗
PubMed1979

Modification of constant optokinetic nystagmus by vestibular stimuation.

Experiments were conducted to quantify the effect of a vestibular stimulation of known magnitude on a constant optokinetic nystagmus (OKN). Ten normal human subjects were tested with varying magnitudes of vestibular stimuli that were superimposed on a constant 30 degrees optokinetic stimulus. The gain of the vestibular system in the dark was 0.42 +/- 0.11, and the gain in the light during superimposition testing was 0.12 +/- 0.02. From these results, predictions were made that the degree of vestibular imbalance necessary to produce an asymmetric OKN would generate a spontaneous nystagmus in the dark, which would be equivalent to 20 to 30 degrees. Data from a large group of patients were used for corroboration of the results.

Adult↗
PubMed1979

Opticociliary veins in a primary optic nerve sheath meningioma.

A 59-year-old man developed painless visual loss in his left eye over a one-year period, with rapid progression to blindness over three months. Ocular examination of the left eye revealed proptosis, marked optic disk pallor, dilated retinal veins, and congeries of vessels at the disk margin (opticociliary veins). His right eye was unremarkable. Fluorescein angiography and histopathologic examination confirmed the presence of opticociliary veins communicating between branches of the central retinal vein and the adjacent choroidal vasculature. Primary orbital optic nerve meningioma associated with opticociliary veins was diagnosed.

Cranial Nerve Neoplasms↗
PubMed1979

Uniocular nystagmus in monocular visual loss.

Uniocular nystagmus was studied by electro-oculography in ten patients with monocular visual loss caused by ocular and optic nerve lesions. In these patients, visual loss was congenital or acquired in childhood or adult life. In all patients the oscillations were present in the primary position of gaze and were vertical, pendular, and of variable and low frequency (less than, or equal to, 1.0 HZ) and amplitude (usually less than 5 degrees). Refixation saccades, smooth pursuit, optokinetic nystagmus, and vestibuloocular responses to rotation in the horizontal and vertical planes were within normal limits. The irregularity, low frequency, and low amplitude of this form of nystagmus cause it to often be missed during casual clinical examination, but easily differentiate it from other causes of uniocular nystagmus.

Adolescent↗
PubMed1979

Visual-vestibular interaction and cerebellar atrophy.

The vestibular and optokinetic ocular control systems were studied in 10 patients with cerebellar atrophy and in 10 normal subjects using (1) constant velocity optokinetic stimulation, (2) sinusoidal rotation in the dark, and (3) sinusoidal rotation in the light with a surrounding fixed optokinetic drum. The gain (maximum slow component velocity/maximum head or drum velocity) of induced nystagmus was calculated from electro-oculographic recordings. Optokinetic nystagmus was abnormal in seven patients and the average optokinetic gain in the patients was significantly (p less than 0.01) less than that of the normal group. Three patients with "clinically pure" cerebellar atrophy had increased vestibular responses, and one patient with clinical signs of peripheral neuropathy had decreased responses, probably due to associated vestibular nerve disease. The average vestibulo-ocular reflex gain in patients did not differ significantly from controls (p greater than 0.05). Three patients had normal vestibular and optokinetic responses when tested independently, but had abnormal visual-vestibular interaction. These patients probably had selective disorders of the midline cerebellar pathways that mediate visual-vestibular interaction. By studying each system, both independently and during interaction, all patients were identified as abnormal, and a more precise anatomic localization of the atrophy was obtained.

Adolescent↗
PubMed1979

Slow build-up of optokinetic nystagmus associated with downbeat nystagmus.

Eye movement recordings in two patients with downbeat nystagmus demonstrated an unusual finding of severely impaired smooth pursuit and relatively unimpaired optokinetic nystagmus (OKN). OKN was characterized by a remarkable, slow build-up of slow-component velocity, similar to that found in afoveate animals. Optokinetic after-nystagmus (OKAN), or transient persistence of nystagmus after cessation of visual stimulation, typical of the optokinetic response of normal human subjects, was also preserved in these patients. These observations suggest that the normal contribution of smooth pursuit to the ocular motor response to rotation of the visual environment can be selectively removed by a lesion at the level of the craniocervical junction.

Adult↗
PubMed1978

Internuclear ophthalmoplegia. I. Saccades and dissociated nystagmus.

Saccades (horizontal and vertical) and dissociated nystagmus were quantitatively assessed in four patients with internuclear ophthalmoplegia. Two patients had bilateral medial longitudinal fasciculus (MLF) lesions associated with multiple sclerosis and two had unilateral lesions associated with brain stem vascular disease. Adducting saccades made on the side of an MLF lesion were slowed in each patient (P less than .01). At the same time, abducting saccades in the contralateral eye had normal velocity, but consistently overshot the target. After the overshoot, the eye returned to the target with an exponentially decaying course. With large angular deviations (usually more than 15 degrees), the abducting eye developed nystagmus characterized by slow components that moved toward the midposition with an initially high velocity followed by a segment of slower velocity. The adducting eye had either no nystagmus or a low-amplitude nystagmus characterized by a rounded junction between the fast and slow component. The saccade abnormalities and waveform of the dissociated nystagmus can be explained by a pulse-step mismatch at the agonist motoneurons.

Adult↗
PubMed1978

Internuclear ophthalmoplegia. II. Pursuit, optokinetic nystagmus, and vestibulo-ocular reflex.

Smooth pursuit, optokinetic nystagmus (OKN) and the vestibulo-ocular reflex (VOR) were studied in four patients with internuclear ophthalmoplegia (two with bilateral and two with unilateral lesions). Horizontal smooth pursuit by an adducting eye on the side of a medial longitudinal fasciculus (MLF) lesion was normal in three of four patients; vertical pursuit was abnormal in all four. The horizontal VOR gain of slow components made by an adducting eye on the side of an MLF lesion was normal in all four patients. The vertical VOR gain was decreased in the two patients tested. It is concluded that either there are pathways independent of the MLF for horizontal pursuit and vestibular signals that are not available to vertical signals, or vertical pursuit and vestibular eye movements require a higher rate of oculomotor neuron firing than equal-velocity horizontal eye movements.

Adult↗
PubMed1978

Histochemistry and acetylcholine receptor distribution in normal and denervated monkey extraocular muscles.

In monkey extraocular muscles (EOM), a battery of histochemical reactions delineates three muscle fiber types, coarse, fine, and granular. Normal EOM are compared with EOM denervated by intracranial oculomotor nerve section. The experimentally denervated EOM fibers did not show the constellation of histologic responses typical of denervated limb muscle, making a diagnosis of a denervation process in EOM muscle very difficult. Although the denervated fine and granular fibers (but not the coarse fibers) develop diffuse extrajunctional acetylcholine receptors (AChR) following experimental denervation, this is not a reliable criterion of denervation because not all of those fibers developed it and they did not show it beyond a 12-week period following nerve section; moreover, myopathic mechanisms have previously been shown capable of provoking diffuse extrajunctional AChR in limb-muscle fibers.

Acetylcholine↗
PubMed1978

Eye movements in ataxia-telangiectasia.

The spectrum of eye movement disorders in six patients with ataxia-telangiectasia at different stages of progression was assessed quantitatively by electrooculography. All patients demonstrated abnormalities of voluntary and involuntary saccades. The youngest and least involved patient had significantly increased reaction times of voluntary saccades, but normal accuracy and velocity. The other patients demonstrated increased reaction times and marked hypometria of horizontal and vertical voluntary saccades. Saccade velocity remained normal. Vestibular and optokinetic fast components (involuntary saccades) had normal amplitude and velocity but the eyes deviated tonically in the direction of the slow component. We conclude that patients with ataxia-telangiectasia have a defect in the initiation of voluntary and involuntary saccades in the earliest stages. These findings are distinctly different from those in other familial cerebellar atrophy syndromes.

Adolescent↗
PubMed1978

Linear model for visual-vestibular interaction.

The results of experiments are evaluated in terms of a simple model for the interaction of eye movement responses to simultaneous optokinetic and vestibular stimuli. The model predictions agree with the results of these experiments and explain many clinical observations concerning the effect of vision on nystagmus. The model accounts for the dominance of the visual system's response over the vestibular system's response at low frequencies. It also accounts for the inability of patients with decreased smooth pursuit system response to suppress the vestibulo-ocular reflex during simultaneous optokinetic and vestibular stimulations. The model provides useful information for the design of combined optokinetic and vestibular stimuli for test vestibulo-ocular reflexes.

Eye Movements↗
PubMed1978

Vestibular-optokinetic interactions in normal subjects and in patients with peripheral vestibular dysfunction.

The vestibulo-ocular reflex (VOR) during rotation, optokinetic nystagmus (OKN), and interactions between the vestibulo-ocular and optokinetic systems were studied quantitatively in 10 normal human subjects, 15 patients with unilateral horizontal semicircular canal paralysis (UP), and 11 patients with bilateral horizontal semicircular canal paralysis (BP). The OKN gain (eye velocity/drum velocity) was not significantly different between the normal subjects and the patient groups. During tests in which rotatory and visual stimuli were presented simultaneously, the contribution to the observed eye movements by the VOR was only one-fourth to one-third of its gain during rotation in the dark in the normal subjects and UP patients. These interactive tests did not differentiate UP patients from normal subjects but did separate BP patients from normal subjects.

Adult↗
PubMed1977

Optic nerve compression due to aneurysmal bone cyst.

A 10-year-old boy developed loss of central vision in both eyes due to compression of the optic nerves by a mass arising from the sphenoid and ethmoid sinuses. Histopathologic examination of biopsy specimens showed a fibrous matrix composed of spindle-shaped cells interspersed with small and large channels, characteristic of an aneurysmal bons cyst. One year after partial excision of the intracranial and extracranial portions fo the lesions, vision had returned to nearly normal levels. Aneurysmal bone cysts rarely involve the orbits or other cranial bones to produce ocular signs and symptoms. However, since this lesion probably represents reactive proliferation of bony tissues, rather than neoplasia, the prognosis for vision and life is good.

Bone Cysts↗
PubMed1977

Abnormal saccades in paralytic strabismus.

Saccadic eye movements were measured in ten patients with unilateral limitation of function of an extraocular muscle. With the paretic eye fixating, there were a series of saccades when refixating in the direction opposite to the paralysis. Between each saccade, the eye drifted back toward the starting position; the drift rate decreased as the eye moved into the field of action of the strong agonist muscle. In one patient, the normal (covered) eye was immobilized during attempted refixations. In this case, the abnormal pattern of saccades made by the paretic eye persisted. Thus, the central nervous system uses innervation or efference to calculate the position of the eye in the orbit for saccadic eye movements.

Eye Movements↗