Search PubMed⌕ Search

Biomedical subjects

R D Yee

Publications and source records attributed to R D Yee.

At least 55 records · Page 3Linked to original sources
PubMed1987

Alteration of the visual evoked potential by macular holes: comparison with optic neuritis.

Nine patients with maculopathy (macular holes, macular cysts, and lamellar holes) and ten patients with optic neuritis were examined in order to determine changes in the visual evoked potential (VEP) in response to pattern-reversal stimulation. Eyes with lamellar holes had normal P100 latency, but eyes with macular cysts and macular holes had prolonged P100 latency. Eyes with optic neuritis exhibited greater prolongation of the P100 latency than eyes with macular holes. In contrast, eyes with macular holes had a greater reduction in the steady-state VEP amplitude than eyes with optic neuritis. The prolonged latency occurring in maculopathy may be due to a peculiar amplitude summation noted with half-field VEP, rather than to a true conduction delay like that seen in eyes with optic neuritis. The amplitude slope, which is usually positive in normal controls, was negative for 85.7% of eyes with macular holes and 69.2% of eyes with optic neuritis. The negative amplitude slope may represent a subtle defect in retinal ganglion X cells. Eyes with significantly lower values for four or more of the nine central test points on quantitative automated perimetry had negative amplitude slopes and prolonged P100 latency.

Adult↗
PubMed1987

Saccadic eye movements in myasthenia gravis.

The peak velocities of horizontal saccades were measured in patients with myasthenia gravis (MG) to determine whether they can differentiate MG from other causes of ophthalmoplegia. Eye movements were recorded with electrooculography (EOG) or infrared scleral reflection (IR) in 42 patients with MG, 26 patients with sixth cranial nerve palsy (CNP), 19 patients with chronic progressive external ophthalmoplegia (PEO) and 28 normal subjects. Despite limitation of ductions in MG, the group means of velocities of 10 deg saccades recorded with IR were similar in MG and normal subjects. With EOG, small but statistically significant decreases in mean velocities of 10, 20 and 30 deg saccades were found in MG, compared to those in normal subjects. Twenty-one to 28% of MG patients had velocities outside of the normal range (outliers). In contrast, the group means in CNP and PEO were markedly lower than those in MG and normal subjects. The frequencies of outliers were 89 to 100% in CNP and 88 to 100% in PEO. Measurement of saccadic velocities can be helpful in differentiating MG from other causes of ophthalmoplegia.

Adolescent↗
PubMed1987

Eye movements in schizophrenia.

Smooth pursuit and other eye movements were quantitatively studied in patients with chronic schizophrenia to characterize the pattern and severity of eye movement abnormalities in this disorder. Twenty-one patients with schizophrenia, 13 patients with other psychiatric disorders (manic-depressive psychosis, schizoaffective disorder, depression and obsessive-compulsive disorder), and 19 normal subjects were studied. Horizontal eye movements were recorded with DC electro-oculography and analyzed by an online computer system. Eye velocity and closed-loop gain of pursuit, optokinetic nystagmus (OKN), vestibulo-ocular response (VOR) and visual-vestibular interactions were calculated. The latency, accuracy and peak velocity-amplitude relationships of voluntary saccades were measured. The group mean gains of pursuit and OKN of the schizophrenic patients were significantly lower than those of the normal subjects. Suppression of the VOR by fixation was impaired, and the latency of saccades was prolonged. However, the differences in group mean values were small in magnitude, and the frequencies of outliers among the schizophrenic patients were low. The patients with other psychiatric disorders had a similar pattern and severity of eye movement abnormalities. The frequency and severity of eye movement abnormalities in schizophrenic patients are lower than those indicated by previous studies that used different techniques of analysis.

Adolescent↗
PubMed1986

Magnetic resonance imaging of craniopharyngioma.

Craniopharyngiomas are common tumors located in the suprasellar region. Contrast enhancement, cyst formation, and calcification are the three characteristic features of craniopharyngiomas on computed tomographic scan. More than 90% of suprasellar craniopharyngiomas exhibit at least two of these three features, thus providing easy radiologic detection. We treated a 41-year-old man in whom a large suprasellar craniopharyngioma producing severe visual loss was not detected by computed tomography but was easily identified with magnetic resonance imaging. Thus, despite high-resolution computed tomographic scan, large suprasellar craniopharyngiomas can be missed. Magnetic resonance imaging may be superior to computed tomography in detecting these tumors.

Adult↗
PubMed1986

Sphenoid sinus mucocele (anterior clinoid variant) mimicking diabetic ophthalmoplegia and retrobulbar neuritis.

Two patients (two men, 56 and 59 years old) had sphenoid sinus mucocele originating in the anterior clinoid process. In one case the mucocele initially mimicked diabetic ophthalmoplegia with pupil-sparing palsy of the oculomotor (third) nerve. After resolution of the palsy, severe visual loss developed with minimal recovery of vision after surgery. The second patient had recurrent episodes of retrobulbar optic neuropathy with optic atrophy and decreased vision. Visual loss from sphenoid sinus mucoceles is usually associated with a poor prognosis if surgical treatment is delayed more than seven to ten days.

Diabetes Complications↗
PubMed1986

Vertical visual-vestibular interaction in normal human subjects.

Previous studies have described asymmetrical vertical eye movements when normal human subjects were rotated about a vertical inter-aural axis (with head rolled 90 degrees). We measured vertical eye movements induced by visual, vestibular and visual-vestibular stimuli with a magnetic scleral search coil technique while 10 normal subjects sat upright in a chair designed to rotate about the horizontal inter-aural axis at frequencies and amplitudes of natural head movements. Asymmetries in the gain of upward and downward pursuit and fixation-suppression of the VOR were found in individual subjects. However, there was no significant difference (p greater than 0.05) between the mean gain of up and down slow eye movements induced by vestibular, visual or visual-vestibular stimulation in the group of normal subjects. Systematic up-down asymmetries in vertical eye movements previously observed with testing about the vertical inter-aural axis were probably due to bias introduced by otolith stimulation and/or electro-oculographic eyelid artifact.

Adult↗
PubMed1986

Late cortical cerebellar atrophy. Clinical and oculographic features.

Ten patients with late cortical cerebellar atrophy documented with computerized tomography (CT) and magnetic resonance (MR) imaging presented a uniform pattern of oculomotor abnormalities. All had deficits in smooth pursuit and fixation suppression of the vestibulo-ocular reflex (VOR). The gain of the VOR was often increased but the dynamics of the VOR were not different from normals. Full-field optokinetic responses and visual-vestibular interaction mediated via the VOR velocity storage element were preserved. Just as in lower primates, the cerebellum in humans is a critical relay station for foveal pursuit and visual-vestibular interaction requiring foveal pursuit. Vestibular responses and visual-vestibular interaction mediated through the VOR velocity storage element are relatively independent of the cerebellum.

Adult↗
PubMed1986

The ETHAN syndrome.

Two mechanisms by which patients compensate for congenital nystagmus are assumption of a head position that places the eyes in a "null zone" of least nystagmus, known as nystagmus compensation syndrome (NCS), and convergence to dampen nystagmus, known as nystagmus blockage syndrome (NBS). We followed five patients in two groups who combine these mechanisms. The first group presented with spontaneous alternation between nystagmus and a head turn with orthotropia (NCS), and a large-angle esotropia with a variable head position that persisted even when patched (NBS). The second group of patients presented with a constant large-angle esotropia that lessened their nystagmus and variable head posture (NBS). Following recession of both medial rectus muscles with or without placement of posterior fixation sutures, they developed an abnormal head posture with orthotropia (NCS). The presence of mild amblyopia may contribute to the alternation between the two compensatory mechanisms.

Adult↗
PubMed1985

Eye-movement abnormalities in ophthalmoplegia, ataxia, and areflexia (Fisher's syndrome).

Ophthalmoplegia, ataxia, and areflexia are present in a distinctive syndrome called Fisher's syndrome. Eye-movement recordings were used to analyze ophthalmoplegia and other eye-movement abnormalities in three patients. Disorders of supranuclear ocular motor pathways (palsy of upward gaze and internuclear ophthalmoplegia) and peripheral cranial nerve palsies could account for the ophthalmoplegia. In one patient, computed tomography demonstrated a lucency in the midbrain that could be correlated with palsy of upward gaze and bilateral internuclear ophthalmoplegia. Eye-movement abnormalities characteristic of lesions of the midline structures of the cerebellum were documented in two patients. A review of reported cases of Fisher's syndrome and brain-stem encephalitis suggested that these syndromes comprise a spectrum of a reversible, parainfectious process affecting the peripheral cranial nerves and CNS.

Adolescent↗
PubMed1985

Eye movements in patients with absent voluntary horizontal gaze.

Despite the complete absence of horizontal saccades, two patients with pontine gliomas had horizontal reflex eye movements within a range of +/- 20 degrees. The gain (peak eye velocity/peak stimulus velocity) and phase of the vestibulo-ocular reflex were normal, but the optokinetic gain was decreased. The latency, accuracy, and peak velocity of vertical saccades were normal. Apparently the voluntary gaze centers in the pontine reticular formation are not crucial for generating horizontal vestibular or vertical saccadic eye movements.

Adult↗
PubMed1985

Eye movement abnormalities in rod monochromatism and blue-cone monochromatism.

Eye movements were recorded with electro-oculography in seven patients with rod monochromatism (RM) and five with blue-cone monochromatism (BCM). The continuous horizontal nystagmus was similar in both groups. However, three patients with BCM demonstrated an intermittent, high-frequency nystagmus, in addition to the continuous nystagmus. The most striking differences between the groups were present during monocular smooth pursuit and optokinetic tracking. Patients with RM demonstrated better tracking when targets moved in the temporal-to-nasal (T-N) direction in the visual field of the viewing eye, than when targets moved in the nasal-to-temporal (N-T) direction. The velocity of optokinetic nystagmus (OKN) increased gradually over several seconds during T-N target movement. Patients with BCM did not show a directional asymmetry or a slow build-up of OKN during monocular tracking. Differences in eye movement abnormalities can be useful in differentiating these two forms of congenital color blindness from other forms of congenital nystagmus and from each other.

Adolescent↗
PubMed1985

Dorsal midbrain syndrome: clinical and oculographic findings.

We report clinical and oculographic findings in seven patients with the dorsal midbrain syndrome (Parinaud's syndrome). All presented with limited upward voluntary gaze and convergence nystagmus with attempted upward voluntary gaze. Quantitative analysis of vertical eye movements documented characteristic abnormalities of saccades with relative preservation of reflex eye movements (ie, vestibular, optokinetic, and visual-vestibular). Vertical saccade velocity was only slightly decreased in five patients with tumors, indicating that the vertical burst neurons in the mesencephalic reticular formation and their efferent pathways to the oculomotor neurons were minimally damaged. On the other hand, two patients with probable brainstem encephalitis exhibited marked slowing of vertical saccades, indicating that the burst neurons, or their efferent pathways to the oculomotor neurons, were severely damaged.

Adolescent↗
PubMed1985

Rotational testing in patients with bilateral peripheral vestibular disease.

We performed quantitative low and high frequency rotational testing in 17 patients with bilateral peripheral vestibular deficits. A characteristic pattern of decreased gain and increased phase lead at low frequencies of sinusoidal stimulation and decreased time constant to impulsive stimulation was observed in most patients. The results of caloric testing correlated with the results of low frequency rotational testing but not with the results of high frequency testing. Only 2 patients complained of oscillopsia at the time of testing and both of these had decreased vestibulo-ocular reflex gain at low and high frequencies of sinusoidal rotation.

Adult↗
PubMed1985

Velocities of vertical saccades with different eye movement recording methods.

Voluntary vertical saccades were recorded in five normal human subjects with electro-oculography (EOG), an infrared, limbus tracking system (IR), and a magnetic scleral search coil method. The peak velocity-amplitude relationships of up and down saccades were measured during refixations across the center of the orbit and within the upper and lower fields of the orbit. The search coil was the most accurate method and did not reveal significant differences between the group mean velocities of up and down saccades in the different fields of the orbit. However, subjects can have idiosyncratic differences in velocities between up and down saccades. EOG overestimated the velocities of up saccades. IR underestimated the velocities of up saccades. The search coil was used to record vertical saccades in adduction and abduction. Horizontal eccentric gaze did not significantly affect the velocities of vertical saccades.

Adult↗
PubMed1984

Episodic vertical oscillopsia and downbeat nystagmus in a Chiari malformation.

A 36-year-old woman had intermittent downbeat nystagmus. Between episodes of downbeat nystagmus, eye movements were normal, except for stationary positional nystagmus and decreased vestibulo-ocular responses (VOR) to rotation. Smooth pursuit, optokinetic nystagmus, and visual-VOR interactions, which are usually impaired in patients with downbeat nystagmus and cerebellar dysfunction, were normal. Computed tomography and findings during a suboccipital craniotomy demonstrated a mild Chiari malformation, type 1. Episodic downbeat nystagmus that is not associated with other ocular motor abnormalities due to cerebellar dysfunction can be an initial sign of a Chiari malformation.

Adult↗
PubMed1984

Changes in the human vestibulo-ocular reflex after loss of peripheral sensitivity.

Quantitative rotational testing was used to study changes in the vestibulo-ocular reflex of patients with unilateral and bilateral peripheral vestibular lesions. Compared with normal subjects, the patients exhibited a characteristic pattern of decreased gain and increased phase lead at low frequencies of sinusoidal stimulation and decreased time constants on impulsive stimulation. By contrast, gain and phase measurements on high-frequency-low-amplitude sinusoidal stimulation were often normal. In the patients with bilateral lesions, the results of caloric testing correlated with the results of low-frequency rotational testing but not with the results of high-frequency testing. There are two main clinical implications of these findings. First, patients with absent response to caloric stimulation (unilateral or bilateral) may have a normal response to high-frequency sinusoidal rotation (i.e., the frequencies that constitute most natural head movements). This probably explains why such patients do not report oscillopsia. Second, low-frequency sinusoidal rotational testing and caloric testing are more sensitive than high-frequency sinusoidal or impulsive rotational testing for detecting early loss of vestibular sensitivity due, for example, to ototoxic drugs.

Adult↗
PubMed1984

Quantitative vestibular testing.

Our standard rotational test battery includes tests of optokinetic nystagmus (OKN), the vestibulo-ocular reflex (VOR), and visual-vestibular interaction. Lesions of the peripheral vestibular system characteristically impair only the VOR, whereas lesions of the central system impair OKN and visual-vestibular interaction. The pattern of abnormal responses can help localize lesions within the central vestibular pathways.

Electronystagmography↗