Biomedical subjects

E Z Blumenthal

Publications and source records attributed to E Z Blumenthal.

30 records · Page 2Linked to original sources

PubMed1997

Recurrent abducens nerve palsy caused by dolichoectasia of the cavernous internal carotid artery.

PURPOSE: To describe a 59-year-old patient who had seven recurrent, self-limited episodes of isolated ipsilateral abducens nerve palsy in the previous 4 years. Each episode lasted between 2 and 5 weeks. METHODS: Systemic examination and neuroimaging studies were performed. RESULT: Repeated comprehensive examination failed to demonstrate any ocular or systemic condition apart from a lateral protrusion by dolichoectasia of the posterior portion of the cavernous left internal carotid artery, compressing the posterior left cavernous sinus. CONCLUSION: Numerous self-limited episodes of sixth nerve palsy may be associated with structural abnormalities of the intracranial carotid vasculature.

Abducens Nerve↗

PubMed1997

Multiple conjunctival metastases as the initial sign of metastatic uveal melanoma.

PURPOSE: To describe a 31-year-old patient who was initially examined with a uveal malignant melanoma metastatic to the ipsilateral conjunctiva. METHOD: Thirteen months after ruthenium 106 plaque therapy for a ciliochoroidal malignant melanoma, numerous pigmented conjunctival lesions first appeared. RESULTS: These lesions were excised and found to be metastases of melanoma to the superficial subepithelial conjunctival tissue, composed of epithelioid cells. CONCLUSION: The appearance of darkly pigmented conjunctival lesions in a patient known to harbor a uveal malignant melanoma, even though lacking any evidence of extrascleral extension or metastatic involvement, may indicate metastatic disease.

Adult↗

PubMed1996

On the origin of cancer.

In this paper, I present a highly unorthodox and provocative hypothesis, namely that cancer is an evolutionarily derived phenomenon, dormant in every human cell and actively triggered in certain individuals. Cancer is shown to help maintain the integrity of the common gene pool through active elimination of individuals, thus serving a definite advantage for the survival of the species. Those individuals who are less capable of maintaining the integrity of their genome are stopped from inheriting defective genes, and even more important, from bequeathing defective deoxyribonucleic acid conservation traits to their offspring. Genome stability is a primary prerequisite for survival. The spread of deteriorated, imperfect genes should have a disastrous effect on a species' chances for survival. Although we tend to focus our attention on mutations as evolution's driving force, the stability of the deoxyribonucleic acid molecule is what really maintains life on our planet. When observing evolution's end product, we tend to forget that the extreme stability of the genetic material is a genetic quality by itself, a product of a long evolutionary process. The hypothesis presented here is that the selection pressure imposed by cancer is one of the mechanisms leading to this stability.

Biological Evolution↗

PubMed1994

A giant tuberculous lymphangioma extending from the mediastinum to the inguinal region.

A 23-year-old Ethiopian new immigrant presented with a giant lymphangioma extending from the posterior mediastinum through the retroperitoneum, ending as a herniated fluid-filled sac in the inguinal region. Chylous fluid aspirated from within the lymphangioma was cultured positive for Mycobacterium tuberculosis. Considerable regression occurred following 6 months of antituberculous treatment.

Adult↗

PubMed1992

Could cancer be a physiological phenomenon rather than a pathological misfortune?

The hypothesis presented here is that cancer is not a phenomenon where the normal functions of the human body break down (like diabetes mellitus or renal failure) but rather a well planned and well coordinated physiological response (similar to the inflammatory response). 'Cancer initiating genes' are presumed neoplastic DNA sequences involved in sensing genome deterioration, consequently enhancing preservation. This genetic trait, different from the concept of oncogenes, actively triggers the neoplastic transformation once genome deterioration is sensed. This self destructive, altruistic phenomenon, obviously devastating to the organism, is nevertheless shown to be a possible mechanism of natural selection. The survival advantage of cancer initiation is discussed using both the concepts of group selection and gene selection. Natural selection, the driving force of evolution, is believed to operate solely on the basis of phenotype differences among individuals. In this paper cancer is hypothesized to be a mechanism that directly scrutinizes the gene contents of the individual, therefore representing natural selection based on genotype differences.

DNA, Neoplasm↗

PubMed1991

A presumed reflex by which upward gaze induces relaxation of accommodation, a way to overcome instrument myopia.

This hypothesized reflex relates the vertical direction of gaze to the amount of tension exerted by the ciliary muscle. Based on simple observations the following is assumed. When looking downwards a tendency for closer focusing (near searching) exists even without a specific visual stimulus, whereas looking up favors a more relaxed state of the accommodative mechanism. This reflex is much weaker than accommodation induced by visual stimuli but may have potential practical implications with regards to automated objective ocular refraction devices. When using such instruments it is crucial to eliminate entirely all accommodation. The inability to achieve such relaxation has prevented automated devices from completely replacing all manual and subjective techniques in ophthalmology practice. If the reflex is empirically proven to exist, then by performing objective examinations while the patient's gaze is directed up, more precise measurements may be achieved. An additional benefit can be derived from comparing upward versus forward gaze measurements. Even a small difference can imply that accommodation has been triggered, so that ultimately this screening method enables identification of the accommodators sub-group and reciprocally approving the accuracy of the non-accommodators sub-group results.

Accommodation, Ocular↗

PubMedDate not supplied

Adjusting the slit-lamp oculars: an unnecessary burden or a must?

Adjusting the slit-lamp eyepiece rings is perceived by some to be insignificant for achieving adequate focus. Others assume that these rings should be set only to compensate for one's refractive error. Observations are presented concerning the eyepiece scale setting during routine examinations, slit-lamp mounted YAG and Argon laser procedures and during opthalmic surgery. Diagrams illustrate the optical basis of these observations. Factors influencing optimal eyepiece ring setting, besides ametropia, include slit-lamp misalignment (variations in calibration) as well as unconscious accommodation. An inaccurate setting cannot be fully compensated by adjusting the slit-lamp joy-stick. When an incorrect setting is used, while using oblique illumination, it becomes impossible to focus on details placed at the center of the viewfinder. In addition, irrespective of joy-stick position, it is impossible to view an oblique slit transecting the cornea in perfect focus. An accurate setting, as a whole, results in sharper images throughout the slit-lamp examination. Differences between individual instruments make it necessary to reset the eyepieces for each eye and for each individual instrument. Methods are described for evaluating the need for readjustment, as well as a simple technique for calibration in the absence of a focusing rod.

Calibration↗

PubMedDate not supplied

On focusing the slit-lamp: Part I. An inaccurate ocular setting--what is there to lose?

Adjustments of the diopter rings on the slit-lamp oculars compensate for three independent factors: the observer's refractive error, the observer's state of accommodation, and any instrument misalignment. An inaccurate setting of these rings will significantly affect the slit-lamp image quality, as well as the precision and accuracy of slit-lamp mounted lasers, such as are used for retinal photocoagulation, YAG capsulotomy, and laser trabeculoplasty. For each slit-lamp and microscope-related examination technique, photographic technique, and laser procedure, the consequences of an incorrect ocular setting are discussed. Data are presented on the preferred ocular settings of several random observers, highlighting both interobserver and intraobserver variability. Finally, photographs demonstrate the image deterioration that occurs when an incorrect ocular setting is used. It is shown that for younger observers, one's distance refraction is only seldom the correct setting of the slit-lamp oculars, and that on different instruments, one should not be surprised to find somewhat different settings. Examiners are urged to check the accuracy of their habitual setting, if only to find out whether the improvement in image quality is worth the extra bother.

Calibration↗

PubMedDate not supplied

On focusing the slit-lamp: Part II. "The fading-slit test"--verifying the ocular setting.

The focusing-rod test is considered the gold standard for determining the correct setting of the slit-lamp ocular rings. This method is, however, somewhat time-consuming, considering the time it often takes to locate a rod every time one switches between slit-lamps or slit-lamp-mounted lasers. In this article we present an alternative test, which we call the fading-slit test, that requires only a second to perform, does not involve additional equipment (such as a rod), and can be applied at any time during the slit-lamp examination. However, while the focusing-rod test determines what setting should be used, the fading slit test can verify only whether the current setting is indeed the correct one and, therefore, it is not a complete substitute for the focusing-rod test. The fading-slit test is performed as follows: while focusing on any approximately flat surface (even the center of the patient's dome-shaped cornea would do) and using oblique illumination, gradually reduce the slit width until it disappears. Pay attention to whether the slit continuously thins, reaching a hairline width prior to its disappearance or, alternatively, whether, just before disappearance, the slit remains somewhat wide, gradually fading away, instead of thinning away. In the former case the ocular setting is correct; in the latter case it is incorrect.

Calibration↗

PubMedDate not supplied

Aligning the Goldmann tonometer tip by means of the "precontact whitish rings".

A set of whitish rings observed before contact is made during Goldmann-type applanation tonometry can help simplify and speed the examination. The orientation and size of the rings are useful both in aligning the tonometer and in estimating the distance remaining before contact is made. Relying on these whitish rings can also avoid some of the shear-related damage exerted on the corneal epithelium from alignment movements of the tonometer tip after contact with the cornea has been made.

Cornea↗

PubMedDate not supplied

A gliacentric view of the human retina.

The structure of retina was historically described using light microscopy histological sections. This description placed prime importance on neural elements and their interconnections is establishing retinal structure. Of the 10 retinal layers, 7 are neural elements. This neurocentric description is, however, not the only way to view the retina. After considering various pathological conditions, we believe that an alternative description of the retina exists, based on glial cells. The gliacentric view may better enhance our understanding of vascular pathologies of the retina. In contrast to the classical view of a 10 sheet neurocentric structure, we propose a gliacentric structure composed of two sheet. This model is supported by the embriological development of the retina, originating from two neuroepithelial sheets (the two layers of the optic vesicle). These neuropithelial layers later develop into two monostratified stheets composed of epithelial cells with the following characteristics: a basement membrane at the basal side, villi at the apical side and intercellular junction complexes at the lateral aspects of the cells. The neural network of the retina lies embedded within these sheets. This gliacentric model has not only theoretical implications but bay also explain why various pathologies of the retina are limited to one compartment rather than extending the entire thickness of the retina.

Epithelial Cells↗

PubMedDate not supplied

The relative distribution of retinal and choroidal blood in the human retina.

In this paper a model is presented to explain the relative distribution of retinal and choroidal blood to the human retina. According to this model the retina between the inner limiting membrane and the outer limiting membrane is metabolically controlled and nourished by the retinal vasculature, through Muller cells. The retina between the outer limiting membrane and Bruch's membrane is nourished by the choroidal vasculature, through the retinal pigment epithelium. Muller cells have the ability of metabolic uptake from the interphotoreceptor space as demonstrated in pathological situations suchs as central retinal artery occlusion, when both the Muller cell and the photoreceptor nuclei survive. This demonstrates an overlap existing between the two distributions. Neural elements in the retina depend on Muller cells and RPE for metabolic support. It is only reasonable to expect that the cleavage plane between the two blood supplies is the outer limiting membrane, the outer limit of the Muller cell. In this model both the photoreceptor nuclei (the outer nuclear layer) and the foveal retina are assumed to be supplied by retinal. and not choroidal, vasculature. One consequence is that after long standing retinal detachment the photoreceptor outer segments degenerate (since they become deprived of choroidal blood supply) but the outer nuclear layer, nourished by the Muller cell, continues to survive.

Choroid↗