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Biomedical subjects

E S el-Hifnawi

Publications and source records attributed to E S el-Hifnawi.

7 recordsLinked to original sources
PubMed1993

Retinal lesions experimentally produced by intravitreal ultrasound.

Currently, vitreous surgical techniques combined with phakoemulsification are an established procedure for the removal of luxated natural lenses or dislocated lenticular material. This has proven to be a safe procedure, but occasionally retinal lesions have been inadvertently created. We describe the ophthalmoscopic and morphologic features of ultrasonically induced retinal lesions in rabbit eyes using a similar technique. The retina was treated directly using a conventional ultrasound tip for pars plana lensectomy (Fragmatome). Ophthalmoscopically slight lesions corresponded to an area of retinal whitening. More severe lesions showed a destruction of the inner retina and created a retinal break. Extensive effects also involved the choroid and led to a retinal defect with rupture of choroidal vessels and heavy bleeding into the vitreous cavity. Histologic evaluation showed that the acoustic energy primarily led to damage of the outer retina, later involving the inner retina and the choroid as well.

Animals↗
PubMed1992

Lectin binding pattern in human retinal pigment epithelium.

A comparative lectin histochemical study of human retinal pigment epithelium (RPE) was performed to investigate the lectin binding pattern of normal, reactive and proliferating RPE. Normal RPE with attached sensory retina was found to bind the lectins Con A, WGA, PNA and RCA I. Reactive and proliferating RPE in retinal detachment and in photocoagulation scars revealed the same lectin binding pattern although its cellular topography changed. RPE-macrophages showed an additional reaction with SBA. In periretinal membranes of human PVR the typical lectin binding pattern of Con A, WGA, PNA and RCA I was found in pigmented and in a subpopulation of non-pigmented cells, suggesting that these lectin-positive elements were of RPE-origin. Additionally, single pigmented cells positive for SBA were found indicating macrophage differentiation. Thus lectin histochemistry provides a tool for cytochemical identification of RPE and its morphologic variants by revealing a specific combination of sugar-binding sites.

Binding Sites↗
PubMed1992

[The effect of cyclooxygenase inhibitors on the course of hereditary retinal dystrophy in RCS rats].

Daily administration of acetyl salicylic acid (ASA) and ibuprofen leads to an appreciable retardation in the process of retinal degeneration in the RCS rat which is dependent on the dosage given. The photoreceptor cell nuclei and inner segments are relatively well preserved in all regions of the retina. While the outer nuclear layer of 32 day old RCS rats is usually composed of only 3-4 rows, we found 8-9 nuclear rows exhibiting minimal pyknotic change in animals which had been treated with higher doses of ASA. These differences in layer thickness could be confirmed using morphometric analysis. The outer segments show evidence of degenerative change although they are in a clearly better condition than those found in untreated animals and in those animals treated at lower dose. Phagolysosomal structures which are not otherwise apparent in this strain of rat are detected only in the RPE cells of animals treated with higher dose. The animals treated with ibuprofen show essentially the same morphological changes although a corresponding effect in regard to the thickness of the outer nuclear layer was only achieved after a high dose. The determined dose for the optimal preservation (thickness) of the outer nuclear layer lies around 160 mg/kg body weight for acetyl salicylic acid and at 400 mg/kg body weight for ibuprofen.

Animals↗
PubMed1991

[Retinal lesions after transvitreal use of ultrasound].

Removal of a dislocated natural lens into the vitreous cavity is now performed using vitreous surgery techniques combined with intravitreal phacoemulsification via the pars plana. In contrast to the earlier external surgical approach to luxated lenses, postoperative complications, particularly retinal detachment, are rare. However, retinal damage may occur when ultrasound is used at therapeutic intensities. We therefore examined ultrasound-induced retinal lesions produced in rabbit eyes by treating the retina directly with ultrasound using the type of tip conventionally used for pars plana lensectomy (Fragmatom). Histological evaluation showed that acoustic energy at low intensities led primarily to damage of photoreceptor cell outer and inner segments, which correlated with a discrete pigment reaction visible on ophthalmoscopy. More severe lesions were seen in destruction of the inner retina and resulted in retinal blanching or caused a small retinal break. High energy led to a full-thickness retinal defect with rupture of choroidal vessels and heavy bleeding into the vitreous cavity. Within these lesions the retinal pigment epithelium and Bruch's membrane were also disturbed. Our ophthalmoscopical and histological findings indicate that the mechanism of ultrasound-induced chorio-retinal lesions is not exclusively thermal in nature and differs from other coagulation modalities.

Animals↗
PubMed1987

Ultrastructural characteristics of preretinal membranes from human eyes filled with silicone oil.

We removed preretinal membranes previously in contact with an intraocular silicone oil bubble from 22 human eyes for ultrastructural examination. All had membrane-bound intracytoplasmic vacuoles, which most likely had been filled with silicone oil before tissue processing. The vacuolation was more pronounced at the surface of the membrane. In the course of ingestion of silicone oil by preretinal cells, giant vacuoles may form by fusion of smaller vacuoles as these cells lack the ability to digest silicone oil.

Capillaries↗
PubMed1987

The effect of long-term irradiation with fluorescent light on the rat fundus.

In the rat, continuous exposure to so-called "cold light" of 800 lux leads to a nearly complete loss of retinal photoreceptors, which occurs within 4 weeks. This process is followed by vascularization of the retinal pigment epithelium (RPE). The origin, extent, and expansion of such proliferations within 6 months after the onset of irradiation were evaluated by means of light microscopy, transmission electron microscopy, scanning electron microscopy, corrosion cast preparation, india ink injection, and trypsin digest preparation. The vessels within the RPE were found to be fenestrated and to form a network with the vessels of the neurosensory retina. Invasion of Bruch's membrane and formation of chorioretinal anastomoses were not observed. The occurrence of vessels within the RPE coincided with a massive regression of capillaries in the neurosensory retina.

Animals↗