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Biomedical subjects

H J Van Dyk

Publications and source records attributed to H J Van Dyk.

At least 19 recordsLinked to original sources
PubMed1989

Embolic anterior ischemic optic neuropathy.

The presumed cause of anterior ischemic optic neuropathy is atherosclerotic vascular changes. Small-vessel occlusive vascular disease most likely causes occlusion of one or more posterior ciliary arteries, compromising blood flow to the optic nerve head and choroid. We present the case of a 59-year-old black man with cholesterol emboli within the retinal vasculature combined with a clinical picture of anterior ischemic optic neuropathy and choroidal nonperfusion demonstrated by i.v. fluorescein angiography. We believe this is evidence that, in a rare case, embolic phenomena may be the cause of anterior ischemic optic neuropathy.

Arteriosclerosis↗
PubMed1987

Diagnosis of neuronal ceroid lipofuscinosis by ultrastructural examination of peripheral blood lymphocytes.

A 7-year-old child with a history of seizures, psychomotor regression, and progressive visual loss was found to have juvenile type neuronal ceroid lipofuscinosis on the basis of characteristic ophthalmoscopic and electroretinographic findings. Although transmission electron micrographs of two separate skin biopsy specimens were normal, peripheral blood lymphocytes were vacuolated and demonstrated, by ultrastructural examination, characteristic "fingerprint profiles" confirming the diagnosis. Peripheral blood lymphocytes from the patient's mother, who had an acquired seizure disorder, demonstrated vacuolated lymphocytes with membranous formations and osmophilic granular bodies, as revealed by electron microscopy. Examination of peripheral blood lymphocytes can be a sensitive diagnostic test in suspected neuronal ceroid lipofuscinosis and may be useful in identifying carriers or family members in the early clinical stages of the disease.

Child↗
PubMed1985

Optic nerve head drusen and glaucoma.

The simultaneous occurrence of both optic nerve head drusen and glaucoma may make it difficult to evaluate visual field defects and the appearance of the optic nerve head. We saw five patients with both conditions, of whom four had pigmentary glaucoma or pigmentary dispersion syndrome. Drusen do not preclude the development of cupping, and they make it difficult to interpret its significance. Management of these patients requires serial visual field testing, serial disc photographs, and treatment aimed at keeping the intraocular pressures as low as possible.

Adult↗
PubMed1984

Primary reticulum cell sarcoma of the brain presenting as steroid-responsive optic neuropathy.

A 23-year-old woman presented with subacute monocular visual loss clinically resembling optic neuritis. CT scan revealed a cerebellar mass, biopsy of which led to the diagnosis of reticulum cell sarcoma (RCS). Corticosteroid therapy resulted in improvement of vision and a decrease in disc edema; this resolution was documented radiographically. While optic nerve involvement is sometimes seen in association with systemic lymphoproliferative disease, optic neuropathy as a manifestation of primary cerebral RCS is rare.

Adult↗
PubMed1982

Loss in pattern-elicited electroretinograms in optic nerve dysfunction.

Both flash- and pattern-elicited electroretinograms and visual-evoked potentials were recorded from a patient with well-documented unilateral optic nerve dysfunction. Although the flash-elicited electroretinograms from the left and right eyes did not differ in amplitude or latency, the flash-elicited visual-evoked potentials were greatly attenuated. Prominent pattern-elicited electroretinograms and visual-evoked potentials, were recorded from the better eye, but neither could be obtained from the affected eye. These results supported the contention that pattern-elicited electroretinograms are derived from optic nerve activity and that the absence of such responses may be diagnostic of loss of optic nerve function. This suggests that testing protocols aimed at assessing optic nerve function might benefit from the inclusion of pattern-elicited electroretinographic recordings. We also obtained contrast sensitivity functions from both eyes. Although considerably suppressed, the contrast sensitivity of the affected eye exhibited a 3-octave range, indicating some pattern-processing capability.

Adult↗
PubMed1981

Orbital Graves' disease. A modification of the "NO SPECS" classification.

This paper reviews the original American Thyroid Association (ATA) classification of the orbital changes in Graves' disease, analyzes the subsequent modification of the classification made by the ATA in 1977, and, finally, suggests a second modification. This consists of the addition of six specific soft-tissue signs to Class II of the original classification.

Exophthalmos↗
PubMed1980

The Tensilon test. A safe office procedure.

Myasthenia gravis in now known to be an autoimmune disorder in which damage of acetylcholine receptors takes place at the post-synaptic membrane. This new knowledge has improved therapy and placed a premium on early diagnosis. To overcome ophthalmologic reluctance to perform Tensilon testing, side effects of Tensilon are reviewed and a survey of the frequency of these side effects is reported.

Cardiovascular Diseases↗
PubMed1979

Direct sagittal computed tomography in Graves' ophthalmopathy.

Standard axial transverse orbital computed tomography scans show the medial and lateral rectus muscles very well but section the superior and inferior rectus muscles obliquely. Determining enlargement of the superior and inferior recti in Graves' disease can therefore be difficult on axial transverse scans. We have obtained sagittal, coronal, and axial transverse orbital scans in a series of patients with Graves' ophthalmopathy and have compared the images in each plane. Direct sagittal and coronal scans were obtained without image regeneration from axial transverse sections by using a wide-aperture Varian body scanner and a special accessory table. Sagittal and coronal scans can demonstrate enlargement of the superior or inferior muscles even in cases in which the medial and lateral recti are normal. Since scans performed at approximately 20 degrees to the sagittal plane are parallel to the long axis of the orbit, they demonstrate orbital anatomy better than scans in the true sagittal plane.

Graves Disease↗
PubMed1979

A comparison of computed tomographic techniques in the diagnosis of Graves' ophthalmopathy.

We performed CT scans on 24 patients with clinically typical Graves' ophthalmopathy to compare the advantages of various scanning techniques. Scans were performed before and after intravenous contrast material infusion, and the contrast-enhancement of abnormal muscles was compared with that of known orbital tumors. Images were also obtained using 5-mm and 8-mm collimators, and the diagnostic value of these collimators was compared. Sagittal and coronal scans were performed in some of the cases, using a new direct technique for the sagittal plane. In general, the 5-mm collimators provided sharper definition of the ocular muscles and optic nerves. Contrast-enhancement alone was not helpful in differentiating enlarged muscles from orbital tumors because of the great overlap of attenuation coefficients. Sagittal and coronal images were helpful in confirming muscle enlargement suspected from axial scans, and were most useful in showing enlarged superior and/or inferior recti in cases with normal medial and lateral recti. The advantages of our method of obtaining sagittal scans through the long axis of the orbit and the potential application of this technique to orbital CT scanning are discussed.

Adult↗
PubMed1978

The angiographic ocular choroidal crescent: distortion with intraorbital and remote intracranial pathology.

The ocular choroidal plexus can be identified on virtually all normal internal or common carotid angiograms. Posterior flattening of the choroid is often seen with retrobulbar tumors. This angiographic appearance can also be observed in some patients with papilledema and increased intracranial pressure. In these patients, ampulliform dilatation of the dura and subarachnoid space just posterior to the globe produces a retrobulbar mass effect that can mimic true retrobulbar tumor. Enlargement of the ocular choroid crescent is an unusual angiographic finding and can be seen with intraocular expansile lesions such as unilateral axial high myopia with posterior staphyloma. An abnormally small, shrunken choroidal blush can be seen with microphthalmia, extreme degrees of hyperopia, and in the phthisical eye.

Carotid Arteries↗
PubMed1978

Osseous choristoma of the choroid simulating a choroidal melanoma. Association with a positive 32P test.

We report the clinical and histopathologic features of an osseous choristoma of the choroid that appeared in a 26-year-old woman. Her diagnostic evaluation included a radioactive phosphorus (32P) uptake test, which was 270% positive and led us to believe that the lesion was an atypical malignant melanoma. The extent of true ossification within this tumor, seen microscopically, explains the false-positive uptake of radioactive phosphorus by this benign tumor; it is well known that bone avidly accumulates radioactive phosphorus. We recommend that all "atypical choroidal melanomas" be studied for the presence of bone, with bone-free roentgenograms, ultrasonography, and possibly, computerized tomographic scans before 32P testing or enucleation. This, to our knowledge, is the second histopathologically proved case of an osseous choristoma of the choroid to be reported in the literature.

Adult↗