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Biomedical subjects

A Loewenstein

Publications and source records attributed to A Loewenstein.

At least 73 records · Page 4Linked to original sources
PubMed1995

Ocular pigmentation protects the rabbit retina from gentamicin-induced toxicity.

PURPOSE: This study was designed to investigate the possibility that gentamicin-induced retinal toxicity is dependent on ocular pigmentation by comparing the effects of the drug on the functional and morphologic integrity of the retina in albino and pigmented rabbits. METHODS: In each rabbit, a solution of gentamicin sulfate was injected into the vitreous of one eye, and saline was injected into the other eye. Retinal function was assessed by electroretinogram (ERG) at different time intervals after injection. Retinal structure was examined at the light microscopic level. RESULTS: In albino and pigmented rabbits, functional retinal damage developed to a maximal level within the first week after gentamicin injection. Thereafter, gradual recovery could be seen in eyes that suffered less than 80% maximal reduction in the ERG b-wave. For each dose >0.1 mg studied, retinal damage was more severe in the albino rabbits than in the pigmented ones. The degree of damage was not affected by the level of ambient illumination, nor was it reduced by the administration of N-acetylcystein, a free radical scavenger, together with gentamicin. CONCLUSIONS: Ocular pigmentation partially protects the rabbit retina from the toxic action of gentamicin. This protection probably reflects binding of the drug by the melanin, which thereby reduces the concentration of the free gentamicin. When the initial gentamicin-induced retinal damage is expressed in < 80% reduction in the ERG, substantial recovery may occur in both strains of rabbits.

Albinism↗
PubMed1994

Application of eye drops to the medial canthus.

BACKGROUND: Our purpose was to investigate the efficacy of instillation of eye drops in the medial canthus with the lids closed at the time of application. METHODS: The pupils of 50 healthy volunteers were dilated with tropicamide 0.125%. The effect of the drug on pupillary dilatation when instilled in one eye with the lids closed was compared to its effect when instilled in the conventional mode in the other eye. RESULTS: Maximal mydriasis achieved was 2.75 +/- 0.76 mm in the eye with closed lids and 2.8 +/- 0.77 mm in the eye in which eye drops were instilled in the conventional mode. CONCLUSION: Eye drop instillation in the medial canthus with the lids closed at the time of application seems to be an effective means of ophthalmic drug delivery.

Adult↗
PubMed1994

Opening by the Nd:YAG laser of the anterior portion of the capsular bag in the treatment of delayed onset pseudophakic endophthalmitis.

We report on a pseudophakic patient with delayed onset endophthalmitis. The patient was treated twice topically and systemically with antibiotic and steroids with temporary response to treatment. The inflammation recurred twice upon withdrawal of treatment. Upon the third relapse of endophthalmitis the anterior portion of the capsular bag was opened by Nd:YAG laser. A third course of systemic and topical antibiotic and steroid treatment was followed by permanent resolution of inflammation. No relapse occurred during 18 months of follow-up.

Aged↗
PubMed1993

Intentional retention of Descemet's membrane in keratoplasty for the surgical treatment of bullous keratopathy.

We report on a modified keratoplasty procedure performed in 6 patients for the treatment of severe pseudophakic bullous keratopathy. While removing the host's cornea, the Descemet membrane was retained, and a full thickness graft sutured on top of it. Postoperatively, aqueous separated the host's Descemet membrane from the graft, thus forming a supernumerary anterior chamber. The graft remained clear in 5 of these patients during up to 28 months of follow-up. We suggest that in some severely damaged and high risk eyes, where opening the anterior chamber might be associated with difficulties and complications, it could be worthwhile to perform an 'extraocular' procedure by retaining the host's Descemet membrane.

Aged↗
PubMed1993

Variable phenotypic expressivity of Best's vitelliform dystrophy.

Two families with Best's vitelliform macular dystrophy (BVMD) were investigated ophthalmoscopically and electrophysiologically. Pedigree examination confirmed the autosomal dominant heredity of this disorder with variable expressivity. Extrafoveal vitelline deposits were present in some asymptomatic patients, strongly suggesting that these deposits represent variable expressivity of familial BVMD.

Adolescent↗
PubMed1993

[Excimer laser correction of myopia].

Excimer laser photorefractive keratectomy was performed on 100 myopic eyes. The preoperative spherical equivalent of myopia ranged from -2.00 to -9.99 diopters (D), mean -4.80 +/- 2.20 D. The procedure was performed under local anesthesia using 0.4% topical benoxinate HCl; corticosteroid eye drops were then used for up to 3 months. All patients achieved corrected visual acuity within 1 line of corrected preoperative visual acuity. The only complication was subepithelial reticular haze seen in all patients, which peaked at 4 weeks after the procedure and gradually diminished within 3 months. After follow-up of from 6-11 months, 93% of patients had achieved uncorrected visual acuity of 6/12 or better. Mean postoperative refraction was -0.20 +/- 0.97 D. 69% achieved a correction within +/- 0.50 diopter of emmetropia, 85% within +/- 1.00 D and 96% achieved corrected visual acuity of within 1 line of preoperative corrected visual acuity. This study and those in the literature show excimer laser to be a promising surgical treatment for myopia.

Follow-Up Studies↗
PubMed1993

Drug-induced retinal toxicity in albino rabbits: the effects of imipenem and aztreonam.

PURPOSE: To test the toxic action of two antibiotics, imipenem and aztreonam, on the functional and morphologic integrity of the albino rabbit retina. METHODS: Two commercial drugs were used--Tienam, which contains imipenem, and Azactam, which contains aztreonam. Different doses of these drugs were injected intravitreally. Retinal function was assessed from the electroretinogram (ERG) and the visual evoked potential (VEP). Retinal structure was examined at the light microscopic level. RESULTS: Imipenem did not affect the ERG and the VEP responses or the morphology of the retina up to a total injected dose of 0.98 mg (2 mg Tienam). Aztreonam was not toxic to the albino rabbit retina up to a total injected dose of 2.8 mg (5 mg of Azactam). Severe functional and morphologic retinal damage was seen when 10 mg of Azactam was injected. A similar degree of damage was seen when a dose of 5 mg L-arginine, an ingredient of Azactam, was injected into the vitreous. CONCLUSIONS: Imipenem and aztreonam are nontoxic to the albino rabbit retina at concentrations that are 500-fold higher than their effective dose against bacterial infection. Azactam is highly toxic at high levels (more than 10 mg injected into the vitreous). Most of the toxicity could be explained by the L-arginine content of the drug.

Animals↗
PubMed1993

The effects of myristyl gamma-picolinium chloride on the rabbit retina: morphologic observations.

PURPOSE: This study was designed to localize the site of action of myristyl gamma-picolinium chloride (MGP) in the rabbit retina and to evaluate the extent of the structural damage induced by the drug. METHODS: The structural damage was assessed at the light microscopic level in eyes treated with various concentrations of MGP at different time intervals after intravitreal injection of the drug. Glial fibrillary acidic protein (GFAP) immunoreactivity was tested in the same eyes and served as an index of retinal damage. RESULTS: The rabbit retinas, examined about 1 mo after MGP injection, exhibited loss of photoreceptors and thinning of the retina in the regions close to the site of injection; remote retinal areas appeared morphologically intact or only slightly affected. Immunocytochemical analysis demonstrated the presence of GFAP in Müller (glial) cells throughout the entire retina. When the effects of MGP were examined at short time intervals (24 and 72 hr) after injection, severe morphologic damage in areas adjacent to the site of drug injection developed in parallel with the electroretinographic findings. However, GFAP could not be demonstrated. CONCLUSIONS: MGP, the preservative used in Depo-Medrol (Upjohn, Kalamazoo, MI), is highly toxic to the rabbit retina.

Animals↗