Biomedical subjects

R D Yee

Publications and source records attributed to R D Yee.

At least 91 records · Page 5Linked to original sources

PubMed1980

Optokinetic nystagmus and parietal lobe lesions.

In an attempt to define better the mechanism of impaired optokinetic nystagmus (OKN) caused by parietal lobe lesions, we recorded the eye movements of two patients. One had a slowly enlarging parietal glioma, and the other, an infarction involving the parietal and occipital lobes. In both patients, ipsilateral foveal pursuit and full-field pursuit of a surrounding optokinetic drum were impaired while voluntary and involuntary saccades (fast components) were normal. Foveal pursuit was impaired more than full-field pursuit, suggesting the existence of two separate pathways by which visual signals for OKN slow phases reach the oculomotor centers in the brainstem. We conclude that the ipsilateral slow phase OKN deficit seen in our patients resulted from damage to the foveal pursuit pathway that runs from the occipitoparietal association area to the ipsilateral brainstem horizontal gaze center.

Adult↗

PubMed1980

Leukemic iris infiltration.

A 7-year-old boy with acute lymphocytic leukemia developed iris infiltration, blood-streaked hypopyon, and high intraocular pressure. A diagnostic anterior chamber paracentesis was performed, which provided a cytologic diagnosis. The aspirate was studied by both the millipore filter technique with Papanicolaou stain and a dried smear using the Wright's stain. Wright's stain provided more distinct cellular details. Irradiation of the anterior segment resulted in clearing of leukemic iris infiltration, hypopyon, and glaucoma.

Adrenal Cortex Hormones↗

PubMed1980

Identification of the location of vestibular lesions on the basis of vestibulo-ocular reflex measurements.

Quantitative analysis of electro-oculographic recordings of eye movement in response to precise visual and vestibular stimuli makes possible the differentiation of three categories of vestibular syndromes due to pathological changes in three different parts of the visual vestibulo-ocular reflex arc: (1) decreased vestibulo-ocular reflex gain (e.g., decrease in slow component velocity), but normal fast components and visual-vestibular interaction (labyrinth and eighth nerve); (2) normal slow component velocity but abnormal fast components to all stimuli (pontine or medullar reticular formation); and (3) normal slow component velocity to vestibulo-ocular stimulaton but abnormal visual-vestibular interaction as well as normal fast components (visual-motor pathways or cerebellum).

Cerebellar Diseases↗

PubMed1980

Study of congenital nystagmus: optokinetic nystagmus.

A severe defect of optokinetic nystagmus (OKN) was found in 46 patients with congenital nystagmus. Abnormal patterns of OKN, such as superimposition of pendular oscillations on the optokinetic slow component and inversion of OKN, were observed. Optokinetic gain (eye movement velocity/drum velocity) was decreased compared to that in normal subjects, and optokinetic after-nystagmus, or transient persistence of OKN after cessation of visual stimulation, was absent. These findings suggest that there is a defect in the subcortical optokinetic system in congenital nystagmus. Optokinetic responses did not clearly differentiate patients who had ocular lesions that impair vision, such as ocular albinism and opacities of the ocular media, from patients who did not have such lesions. Similar abnormal patterns of OKN were found in both groups of patients, although optokinetic gain tended to be lower in patients with ocular lesions than in those without lesions.

Electrooculography↗

PubMed1980

On-line analysis of eye movements using a digital computer.

We describe a microcomputer system for on-line analysis of eye movement recordings. Quantitative data from the patient and statistical comparison with normative data is available within seconds of test completion. Three types of eye movements are analyzed--voluntary saccades, smooth pursuit, and nystagmus. The first two are induced by a computer-controlled laser dot projected onto a screen and the third by a computer-controlled optokinetic drum, caloric infusion, and rotatory chair. The computer algorithm differentiates the eye position signal to yield an instantaneous eye velocity record. Saccades are identified based on their characteristic velocity profile. For pursuit and nystagmus. The first two are induced by a computer-controlled laser dot projected onto a screen and the third by a computer-controlled optokinetic drum, caloric infusion, and rotatory chair. The computer algorithm differentiates the eye position signal to yield an instaneous eye velocity record. Saccades are identified based on their characteristic velocity profile. For pursuit and nystagmus, the velocity record is modified by linearly interpolating across segments in which saccades occurred. The gain (output eye velocity/input eye velocity) is calculated after Fourier analysis of the data.

Computers↗

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↗