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Biomedical subjects

P A Weber

Publications and source records attributed to P A Weber.

At least 19 recordsLinked to original sources
PubMed1992

Probe orientation in contact Nd:YAG laser cyclophotocoagulation.

We investigated the effect of the angle orientation of the probe during Nd:YAG transscleral cyclophotocoagulation. We found, based on histologic evaluation of the ciliary processes and surrounding structures, that the angle at which the probe was placed on the eye was critical. A probe angulation as little as 15 degrees off the perpendicular destroyed sites less than optimal for achieving the goal of decreasing aqueous humor production.

Aqueous Humor↗
PubMed1991

In vivo functional implications of isoproterenol-mediated relaxation of isolated human iris sphincter.

The isolated human iris sphincter contracted with carbachol produced relaxation with an average ED50 of 1.30 x 10(-7) M for (-)-isoproterenol. The effect is sensitive to block by (-)-timolol with KB 3 x 10(-9) M. The magnitude of the average relaxation mediated by the beta-adrenoceptor agonist was only 31%. Lowering of the temperature did not potentiate the effect of (-)-isoproterenol to a significant extent. Thus, in contrast to bovine iris sphincter, where the beta-adrenoceptor mediated response of (-)-isoproterenol produces a maximum relaxation or complete mydriasis, the maximum beta-adrenoceptor mediated mydriasis of human iris may not be more than 1/3 of the maximum pupillary dilatation achieved by physiologic or pharmacologic procedures.

Aged↗
PubMed1990

Evaluation of antiproliferative agents using a cell-culture model.

Chinese hamster ovarian (CHO) cells in culture were used to evaluate the relative antiproliferative potential of drugs. These agents have been used to improve the clinical response after glaucoma filtering surgery. The following drugs were evaluated: 5-fluorouracil (5-FU) as the benchmark, 5-fluorouridine (FUR), 5-fluorodeoxyuridine (FUDR), 5'-deoxy-5-fluorouridine (DFUR), bleomycin, and cytarabine (ARA-C). In addition to cell counting, a colorimetric assay based on the tetrazolium salt, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) was used to follow growth response. The MTT assay was found to be extremely convenient and an indirect measure of cell activity, offering an alternate or addition to a measure of cell number. All agents tested were shown to inhibit cellular proliferation. Dose-response curves for each agent indicate the following absolute potency: FUDR greater than FUR greater than ARA-C greater than 5-FU = bleomycin greater than DFUR. Besides absolute potency, an evaluation of the effects of equivalent inhibitory concentrations of each drug on growth rate was assessed. Several agents affected the proliferation rate patterns differently. Based on these studies, it is suggested that the in vitro model can identify potential agents through an assessment of their overall activity profile in CHO cells, which includes not only their potency based on dose response, but their onset of activity, duration of effect, and potential for toxicity.

Animals↗
PubMed1989

Laser trabeculoplasty retreatment.

Thirty-seven eyes of 30 patients classified as late treatment failures following 360 degrees of argon laser trabeculoplasty (ALT) underwent retreatment of the trabecular meshwork. Retreatment was considered successful if the intraocular pressure was maintained at 21 mm Hg or below and if the visual fields and optic nerve remained stable. By the Kaplan-Meier survival analysis the rates of success were: 100% at 3 months, 91% at 6 months, 77% at 9 months; 70% at 1 year, and 47% at 16 and 20 months. The mean decrease in intraocular pressure 1 month after retreatment was 6.5 +/- 4.9 mm Hg (from 23.9 to 17.5). Three patients followed for 3 years or longer had a mean decrease of -5.67 mm Hg. Repeat argon laser trabeculoplasty appears to be a reasonable treatment option for selected patients who are late failures after initial treatment.

Aged↗
PubMed1988

Corneal decompensation after argon laser iridectomy.

Five eyes of three patients developed generalized corneal decompensation after undergoing argon laser iridectomy for angle closure glaucoma. Factors possibly associated with corneal decompensation include episodes of angle closure glaucoma with pressure elevations and inflammation, corneal guttate, diabetes, and the need for multiple treatments requiring a high-laser energy. It is important for ophthalmologists to inform their patients of the rare risk of developing bullous keratopathy after argon laser iridectomy and to consider obtaining prelaser specular microscopy to document the corneal status in high-risk patients.

Aged↗
PubMed1988

Posterior polymorphous dystrophy--a histopathologic presentation.

The corneal button from a 34-year-old woman with posterior polymorphous dystrophy was studied by light and electron microscopy. Ultrastructural findings showed coexistence of epithelial-like cells and abnormal endothelial cells, and Descemet's membrane composed of a normal anterior banded layer, and an irregular posterior homogeneous and collagenous layer. We suggest that these abnormal endothelial cells are in the process of transforming into epithelial-like cells.

Adult↗
PubMed1987

Central retinal vein occlusion and malignant glaucoma.

Malignant (ciliary block) glaucoma developed in three patients with primary open angle glaucoma with preexisting central retinal vein occlusion following trabeculectomy. Two of the three patients had 360 degrees open angles prior to surgical trabeculectomy. Although the relationship may be coincidental, we propose that central retinal vein occlusion may be a risk factor for the development of malignant glaucoma following filtering surgery.

Aged↗
PubMed1987

The effect of blepharoptosis on the field of vision.

Upper eyelid position, pupillary diameter, and visual field impairment were measured in 26 eyes with adult-onset blepharoptosis. The magnitude of superior visual field impairment was inversely proportional to the distance between the upper lid margin and the pupillary aperture. The distance between the upper lid and the central corneal reflex was the most useful measurement for predicting visual field impairment. Superior visual field impairment was present when the distance between the upper lid and the central corneal reflex was less than 2.5 mm. Visual field impairment inferiorly, temporally, and nasally occurred when the central corneal reflex was obscured and less than 1.5 mm of the vertical diameter of the pupil was visible. Observation of the relationship between the upper eyelid and the pupillary aperture provides useful information for the performance of accurate diagnostic perimetry, as well as for the management of blepharoptosis.

Adult↗
PubMed1986

Cardiovascular effects of ophthalmic timolol.

We studied cardiovascular effects related to ophthalmic timolol maleate, a beta-adrenergic blocker commonly used to treat chronic glaucoma. Twenty normal subjects were randomly assigned to two double-blind treatment groups each with ten subjects. One group received two drops of ophthalmic timolol (0.5%) twice daily for 4 weeks, and the other received two drops of placebo (artificial tears) twice daily for 4 weeks. Ophthalmic timolol significantly decreased resting and maximal exercise heart rate after the first dose and maximal exercise heart rate during chronic dosing. Chronic timolol administration reduced oxygen consumption at maximal exercise and blunted the augmentation in exercise capacity seen during chronic placebo therapy. Cardiac sympathetic tone and inotropy were reduced after ophthalmic timolol treatment. Despite the presence of drug-induced cardiovascular effects, the plasma levels of timolol were often undetectable and never exceeded 2.8 ng/mL.

Adult↗
PubMed1986

Coexistence of diabetes mellitus, optic atrophy, and sensorineural deafness: case report.

The association of diabetes mellitus, optic nerve atrophy, and sensorineural deafness is a rare but distinct syndrome. We describe an 18-year-old woman who developed diabetes mellitus at three years of age, sensorineural deafness at 14 years of age, and bilateral asymptomatic optic atrophy at 18 years of age. Diabetic retinopathy was notably absent. Forty-two patients with diabetes mellitus and optic atrophy have been described. All had type I diabetes mellitus without typical diabetic retinopathy even though insulin-dependent diabetes mellitus was present for many years. Other neurologic abnormalities, including diabetes insipidus, epilepsy, and nystagmus, have been described in association with diabetes mellitus and optic atrophy. A distinct, heredofamilial genetic mechanism, unrelated to diabetes mellitus per se, is postulated.

Adolescent↗
PubMed1986

Elimination of sodium hyaluronate-induced decrease in outflow facility with hyaluronidase.

The use of intraocular sodium hyaluronate is complicated by a postoperative rise in intraocular pressure (IOP). The rise in IOP is thought to stem from a "clogging" at the trabecular meshwork by the large molecules of hyaluronate. This study uses serial tonographic measurements in an animal model to document this change in outflow facility. Furthermore, we investigate the ability of the enzyme hyaluronidase to cleave the hyaluronate into smaller molecular weight fragments, in vivo, and thereby eliminate the change in outflow facility. This report demonstrates the potential usefulness of this enzyme and documents the lack of harmful side effects histopathologically.

Animals↗
PubMed1985

Interaction of timolol and caffeine on intraocular pressure.

The clinical interaction of 0.5% timolol maleate and 400 mg of oral caffeine on the intraocular pressure of 20 normotensive volunteers was studied. Caffeine administration did not significantly alter the reduction in intraocular pressure in timolol treated eyes. An antagonism, however, was observed in the fellow timolol untreated eyes with caffeine. The crossover reduction in intraocular pressure noted in the control group was significantly depressed in the caffeine group. A proposed mechanism for these observations is discussed.

Adult↗
PubMed1984

Effect of topical timolol maleate on exercise performance.

The effect of topical timolol maleate on exercise performance was investigated in a randomized double-blind study. Healthy young subjects underwent two graded maximal exercise evaluations on a treadmill. The evaluations were given one week apart. Before each trial, the subjects were given a single drop of either placebo or 0.5% timolol maleate in each eye. The results indicate that topical timolol has a statistically significant effect on both maximal heart rate and time to exhaustion. However, we found that the drug had no effect on the physiologic parameters of Vo2, respiratory rate, Vco2, or respiratory quotient.

Administration, Topical↗
PubMed1984

Argon laser treatment of the ciliary processes in aphakic glaucoma with flat anterior chamber.

We treated three patients (a 72-year-old man, a 68-year-old woman, and a 60-year-old man) with aphakic glaucoma with flat anterior chamber by administering laser burns to the ciliary processes (11 ciliary processes in one case, 27 in the second, and three in the third). There was some improvement in all three cases; in one case the intraocular pressure decreased from more than 50 mm Hg to less than 20 mm Hg. In each case the anterior chamber deepened immediately without administration of cycloplegics.

Aged↗
PubMed1983

Pigmentary glaucoma in a black albino.

Pigmentary glaucoma has been only rarely reported in the black population. There have been no reports of this disorder in an albino. We report a case of pigmentary glaucoma in a 55-year-old black albino. A dramatic increase in iris transillumination was observed after institution of topical epinephrine. A possible explanation for this progressive iris transillumination is discussed.

Albinism↗
PubMed1983

Transient myopia following isosorbide dinitrate.

A 38-year-old white woman consistently developed transient myopia following the administration of isosorbide dinitrate (Isordil). The myopia was associated with a decreased amplitude of accommodation, a reduction of the AC/A ratio and was eliminated by cycloplegia. Ciliary spasm secondary to the ingestion of this medication is proposed as a possible explanation for the transient myopia. To our knowledge, this case represents the first case of transient myopia following isosorbide dinitrate administration.

Accommodation, Ocular↗
PubMed1983

Two-stage Neodymium-YAG laser trabeculotomy.

A preliminary report of a newly devised glaucoma operation is presented. This procedure combines a non-penetrating trabeculectomy with Neodymium:Yittrium-Aluminum-Garnet (Nd:YAG) trabeculotomy. This thus creates a through and through filtration under a scleral flap without actually entering the anterior chamber.

Adult↗