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Biomedical subjects

R D Yee

Publications and source records attributed to R D Yee.

At least 73 records · Page 4Linked to original sources
PubMed1984

Low and high frequency sinusoidal rotational testing in patients with peripheral vestibular lesions.

We found a consistent pattern of response to low and high frequency sinusoidal rotational testing in patients with chronic compensated unilateral and bilateral peripheral vestibular lesions. Gain (peak slow phase eye velocity/peak chair velocity) was decreased and phase lead increased at low frequencies but both measurements approached normal at high frequencies. Asymmetries in gain, when present, were approximately the same in the low and high frequency range. These changes can be explained by a simple first order linear model of the vestibulo-ocular reflex if one assumes that the goal of the compensation process is to maintain gain in the high frequency range.

Electrooculography↗
PubMed1983

Analysis of characteristic eye movement abnormalities in internuclear ophthalmoplegia.

Quantitative electro-oculographic recording techniques were used to analyze four characteristic eye movement abnormalities in 21 patients with internuclear ophthalmoplegia (INO). The frequency of each of the abnormalities was determined to suggest a pattern that is the most sensitive in detecting the syndrome of INO. Slowing of the adducting saccade was the most frequently found abnormality, being present in all patients. The other characteristic eye movement disorders were found less frequently: dissociated nystagmus at 30 degrees of eccentric gaze, dysmetria of the abducting eye, and limitation of adduction. The most sensitive pattern for detecting an INO seems to be slowing of the adducting saccade combined with either dissociated nystagmus or dysmetria of the abducting eye. Limitation of adduction was seen much less frequently.

Adult↗
PubMed1983

Influence of vestibulo-ocular reflex gain on human optokinetic responses.

In 15 patients with severe bilateral vestibular impairment (mean vestibulo-ocular reflex (VOR) gain less than 0.05), constant velocity optokinetic nystagmus (OKN) gain, optokinetic after nystagmus (OKAN) initial velocity, and OKAN duration were significantly (p less than 0.0025) lower than in 20 normal subjects of similar age. In the normal subjects VOR gain was significantly correlated (p less than 0.05) with OKAN initial velocity but not with OKAN duration or OKN gain. The results of this study provide additional evidence for the existence in human subjects of an optokinetic pathway whose function, like that of the subcortical optokinetic pathway in animals, varies with VOR gain.

Adult↗
PubMed1983

Acquired immune deficiency syndrome. Ocular manifestations.

The acquired immune deficiency syndrome (AIDS) is a recently described disorder of cellular immunity in homosexuals, intravenous drug abusers, and Haitians. Manifestations include Kaposi's sarcoma, Pneumocystis carinii pneumonia, and other opportunistic infections. Ophthalmic and autopsy examinations of 30 patients at UCLA revealed frequent ocular abnormalities. Findings included cotton-wool spots (16 patients), cytomegalovirus retinitis (eight patients), conjunctivitis and keratitis (four patients), conjunctival Kaposi's sarcoma (three patients), Mycobacterium avium intracellulare choroidal granulomas (one patient), and retinal periphlebitis (one patient). We feel that the presence of cotton-wool spots in patients with this syndrome indicates a poor prognosis. Immunologic and electronmicroscopic studies of cotton-wool spots revealed no infectious agents or immunoglobulin deposition. Cytomegalovirus retinitis always was associated with a fatal outcome. The retinitis was characterized by an acute inflammatory reaction in 50% of patients. Ophthalmologists should be aware of the syndrome and its ocular manifestations.

Acquired Immunodeficiency Syndrome↗
PubMed1983

Fatal intracranial extension of an orbital umbrella stab injury.

We examined a patient with an orbital stab injury with fatal intracranial extension in whom the initial emergency examination did not reveal the extent of damage. Ophthalmologic consultation showed an afferent pupillary defect (Marcus-Gunn pupil), which prompted radiologic studies. Orbital tomograms and computerized tomography demonstrated an optic canal fracture and penetration to the contralateral right ventricle. Diabetes insipidus and thermal irregularity developed, and death occurred seven days later.

Adult↗
PubMed1983

The dynamics of vertical eye movements in normal human subjects.

We studied the dynamics of horizontal and vertical slow eye movements (vestibular, optokinetic, pursuit, and visual-vestibular) in 10 normal human subjects. Several differences between horizontal and vertical eye movements were found. The time constant (time required for the slow-phase eye velocity to decay to 37% of the peak value) of vertical postrotatory nystagmus (PRN) was, on average, 50% as long as the time constant of horizontal PRN; the mean phase lead of per-rotatory nystagmus during low-frequency sinusoidal rotation in the vertical plane was approximately twice the mean phase lead of per-rotatory nystagmus at the same frequency in the horizontal plane. Vertical optokinetic after-nystagmus (OKAN) was minimal compared to horizontal OKAN. Asymmetries in the dynamics of vertical eye movements were also noted. The mean time constant of PRN with upward slow phases was consistently longer than the mean time constant of PRN with downward slow phases and vertical OKAN only occurred when the optokinetic stimulus moved upward. Upward pursuit was better than downward pursuit and upward slow phases of vestibular nystagmus were poorly inhibited with fixation while downward slow phases were normally inhibited.

Electrooculography↗
PubMed1983

Effect of eccentric gaze on pursuit.

The effect of eccentric gaze on pursuit eye movements was studied with electro-oculography in normal human subjects and a patient with defective pursuit. Sinusoidal target trajectories were centered about the primary position of gaze and eccentric, horizontal positions of gaze. Eccentric gaze decreased pursuit gain (eye velocity/target velocity) when the eyes moved farther eccentrically in the orbits and increased pursuit gain when the eyes moved toward the centers of the orbits. The magnitude of these effects increased with increasing eccentricity of gaze, increasing peak target velocity, and decreasing pursuit gain during tracking of target trajectories centered about the primary position. These effects can be caused by the elastic forces of the extraocular muscles, globe and other orbital tissues. The pursuit subsystem cannot compensate for these factors at high target velocities, or when it is impaired by pathologic lesions.

Cerebellar Diseases↗
PubMed1983

Effects of an optokinetic background on pursuit eye movements.

The effects of an optokinetic background on pursuit eye movements was studied in four normal human subjects and seven patients with impaired pursuit and/or optokinetic nystagmus (OKN). Eye movements were recorded by DC electro-oculography and eye movement velocity was analyzed by a digital, microprocessor system. Tracking of a small laser target was performed against a featureless, white screen, a stationary OKN background that filled the entire visual field and an OKN background moving at constant velocity. The OKN background significantly affected pursuit in all subjects. The stationary background or background moving in the direction opposite to that of the laser target impaired pursuit; whereas, the background moving in the same direction as that of the target improved pursuit. The effects of the background on pursuit were greater in subjects with lower pursuit gains during tracking against the screen. An algebraic summation of independently induced pursuit and OKN eye movements could not account for all of the experimental observations.

Eye Movements↗
PubMed1982

Familial, congenital paralysis of horizontal gaze.

Eye movements were studied in a sister and brother with familial, congenital paralysis of horizontal gaze. Horizontal and vertical eye movements were recorded with DC electro-oculography and analyzed with a laboratory computer. All horizontal, conjugate eye movements were absent (saccades, pursuit, optokinetic nystagmus, vestibulo-ocular response, and visual-vestibular responses). Voluntary vergence eye movements were preserved and were used to track visual targets. An involuntary, horizontal, pendular nystagmus was found to represent disconjugate, smooth, vergence eye movements. Vertical saccades and vestibulo-ocular responses were normal. However, vertical pursuit, optokinetic nystagmus, and suppression of the vestibulo-ocular response by fixation were impaired. A developmental anomaly affecting motor neurons and interneurons in the abducens nuclei is suggested to be the cause of the absence of conjugate, horizontal eye movements.

Abducens Nerve↗
PubMed1982

Clinical manifestations and radiologic findings in craniopharyngiomas in adults.

The clinical and histopathologic findings in two adults with craniopharyngioma emphasized the wide age range and diverse initial manifestations of this tumor. A retrospective clinical review of 49 additional patients substantiated these points and disclosed that over 40% were initially examined by ophthalmologists. The initial manifestations fell into four broad categories: (1) visual system abnormalities (77% of the cases), (2) headache (67%), (3) endocrinologic abnormalities (57%), and (4) mental status abnormalities (19%). The frequency of these manifestations varied slightly among different age groups. The radiologic features in the two patients described (a 75-year-old man and a 38-year-old woman) included a distinct appearance on computed tomographic scans. These craniopharyngioma were not calcified and were isodense without contrast but enhanced densely and uniformly with contrast, simulating an aneurysm of the circle of Willis.

Adolescent↗
PubMed1982

Ocular disorders associated with a new severe acquired cellular immunodeficiency syndrome.

Among the prominent features of a newly described acquired cellular immunodeficiency syndrome that affects previously healthy male homosexuals are multiple opportunistic infections and Kaposi's sarcoma. Immunosuppression induced by cytomegalovirus infection may play a major role in the pathogenesis of this disorder. We have performed ophthalmic examinations on seven such patients and found ocular abnormalities in all cases. Six patients were examined during the course of their illness and one patient at autopsy only. Each patient had several cotton-wool spots in the affected eye. Other ocular findings included cytomegalovirus retinitis, severe retinal periphlebitis, and conjunctival Kaposi's sarcoma (one case each).

Candidiasis, Chronic Mucocutaneous↗
PubMed1981

Eye movement abnormalities in rod monochromacy.

Eye movements were studied quantitatively using electro-oculography in seven patients with rod monochromacy. Attention was given to eye movement abnormalities that could help to differentiate rod monochromacy from other forms of congenital nystagmus. Horizontal nystagmus in center gaze had pendular and jerk waveforms with much lower amplitude than that in patients with other forms of congenital nystagmus and visual acuity of 20/200-20/400. Slow build-up of slow component velocity over many seconds and directional asymmetry of optokinetic nystagmus (OKN) were observed during monocular optokinetic stimulation. The directional asymmetry of OKN was characterized by a higher OKN gain (eye velocity/OKN drum velocity) during rotation of the OKN drum in the temporal-to-nasal direction in the visual field, than that during drum rotation in the nasal-to temporal direction. Similar directional asymmetry and slow build-up are found in afoveate animals, such as the rabbit, during monocular optokinetic stimulation, but are not found in normal human subjects or in patients with other forms of congenital nystagmus.

Adolescent↗
PubMed1981

Eye movements in patients with Wallenberg's syndrome.

We studied electro-oculographic and videotape recordings of eye movements in six patients with Wallenberg's syndrome. With fixation, all patients had a spontaneous rotatory nystagmus with the fast phase directed toward the intact side. With loss of fixation, the patients' eyes deviated tonically toward the side of the lesion. Voluntary and involuntary saccades had larger amplitude when directed toward the side of the lesion than away from it. The spontaneous nystagmus predictably interacted with all slow eye movements, producing asymmetric smooth-pursuit, optokinetic, and vestibular responses. In addition, smooth-pursuit and optokinetic responses were decreased significantly in both directions compared to normal subjects. Fixation suppression of vestibular nystagmus also was impaired in both directions. We concluded that two different types of oculomotor bias were present in these patients--a velocity bias and a position bias. The former resulted from damage to the caudal lateral vestibular nuclei, and the latter from interruption of cerebellopontine pathways.

Adult↗
PubMed1981

A study of congenital nystagmus: vestibular nystagmus.

The vestibulo-ocular response (VOR) to rotatory stimuli was studied by electro-oculography in 41 patients with congenital nystagmus. The pattern of the VOR and the gain of the slow component velocity (peak eye velocity/peak chair velocity) were normal in 55 per cent of the patients. In 10 per cent of patients an abnormal pattern of the VOR in which the eyes deviated tonically in the direction of the slow component of the VOR was found. In these patients a mild defect in the generation of vestibular fast components might be present since the slow component velocity (SCV) appeared to be normal, but the amplitude and frequency of fast components were decreased. Thirty-two per cent of patients demonstrated persistence of an intense nystagmus with eyes opened in the dark. However, summation of the smooth movement velocity of the nystagmus and the SCV of a probably normal VOR could be demonstrated. The VOR was basically normal in patients with congenital nystagmus with or without associated ocular lesions.

Electrooculography↗