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Biomedical subjects

A Patz

Publications and source records attributed to A Patz.

At least 37 records · Page 2Linked to original sources
PubMed1987

Ten years after the Diabetic Retinopathy Study.

The Diabetic Retinopathy Study (DRS) demonstrated that prompt argon laser photocoagulation, in comparison to indefinite delay in treatment, could reduce by more than 50% the risk of severe visual loss from proliferative diabetic retinopathy. The DRS also enlightened two generations of ophthalmologists about the value of the randomized controlled clinical trial as a way of assessing new and existing treatments for unsolved therapeutic problems. After the example of the DRS, laser treatment was shown to be effective in reducing vision loss in selected patients with branch retinal vein occlusion, age-related macular degeneration, ocular histoplasmosis, and diabetic macular edema. Existing trials, supported by the National Eye Institute, are seeking to determine the appropriate treatment for selected patients with newly diagnosed glaucoma, vascularized corneas, retinopathy of prematurity, proliferative vitreoretinopathy and complicated retinal detachment, and choroidal melanoma. Clinical practice has benefited enormously from these studies all of which owe their existence, at least in part, to the prototypical clinical trial, the DRS. This symposium discusses the DRS and places it in today's perspective, with a look to the past as well.

Clinical Trials as Topic↗
PubMed1986

The role of fluorescein angiography in national collaborative studies.

Over the past 20 years, fluorescein angiography has demonstrated its value in the diagnosis and management of most diseases of the retinal vessels and choroidal vessels, including diabetic retinopathy, aging macular degeneration, and venous occlusive disorders. Fluorescein angiography has become so important for diagnostic purposes and for laser management that it has become a standard technique in the authors' most carefully performed clinical research studies such as randomized clinical trials. These clinical trials demand fluorescein angiography not only for diagnosis and eligibility of patients, but also to document the adequacy of laser photocoagulation. The use of fluorescein angiography has encouraged the development of newer photographic techniques and has encouraged a commendable level of expertise among photographers. Experience with fluorescein angiography in clinical trials has led to the development of general guidelines for the use of angiography for the management of patients outside the confines of a clinical trial; we emphasize the importance of recent angiography as a general guideline for all patients with macular edema or choroidal neovascularization before consideration of laser photocoagulation.

Aspirin↗
PubMed1986

Respiratory arrest following retrobulbar anesthesia.

Respiratory arrest is a serious complication of retrobulbar anesthesia. We have prospectively followed 3123 retrobulbar injections to determine the incidence of respiratory arrest and identify possible risk factors. Injections contained either 2% or 4% lidocaine with 0.75% bupivacaine (Marcaine) in a 50:50 mixture by volume (total 10 cc.) to which a 1 ml ampule of hyaluronidase (150 NF units) was added. Use of 4% lidocaine gave a significantly higher incidence of respiratory arrest than 2% lidocaine (0.79% vs. 0.09%; P = 0.003, Fisher's exact test). Serum levels of lidocaine and bupivacaine of patients who arrested were not elevated significantly compared to 20 control patients. All levels were well below accepted levels of toxicity. Thus, 4% lidocaine increases the risk of respiratory arrest. These results suggest the mechanism is not direct intravascular or central nervous system injection.

Adult↗
PubMed1986

The natural history of serous retinal pigment epithelium detachment in patients with age-related macular degeneration.

One hundred ten patients with serous detachment of the retinal pigment epithelium (RPE) were reexamined to enhance our knowledge of the natural course of this condition. All patients were greater than 50 years of age, had age-related macular degeneration, and had neither blood, lipid, nor angiographic evidence of a definite choroidal neovascular membrane (NVM) at the time of the initial examination. All patients were followed up for at least six months except for two patients who had developed a choroidal NVM within the first six months of the initial exam. Forty-five of 140 eyes (32%) developed a choroidal NVM within an average of 19.6 months (median, 12 months). This was associated with a final visual acuity of 20/200 or worse (P less than 0.0001). Ophthalmoscopic and angiographic features present at the initial visit which were associated with the development of NVM and poor final visual acuity were: sensory retinal detachment; increased size of PED; hot spot; late filling; notching; and irregular filling. At the most recent examination, 39% of the eyes had a final visual acuity of 20/20 to 20/40, while 24% of the eyes had a final visual acuity of less than or equal to 20/200.

Aged↗
PubMed1986

Presence of endothelial cell growth factor activity in normal and diabetic eyes.

Two classes of growth factors affecting endothelial cell proliferation have been found previously in ocular tissues: a heat labile mitogen from retina (RDGF) and a heat stable inhibitor of proliferation from vitreous. The relative amounts of these growth factors in normal and diabetic cadaver eyes were investigated using fetal bovine aortic endothelial cell proliferation as an assay. Equivalent levels of RDGF activity were extracted from diabetic and normal sensory retinas. An extract from pigment epithelium and choroid was found to have similar levels of mitogenic activity, but this activity was not as heat labile as RDGF. Like RDGF, equivalent amounts of mitogen were extracted from diabetic and normal tissue. Normal human vitreous inhibited endothelial cell proliferation, and this activity was enhanced by heating the material (10 min., 95 degrees C). Four of the five individual diabetic vitreous samples of identical postmortem times were mitogenic when not heated, and exhibited little or no inhibitory activity when heated. Vitreous of identical postmortem times was pooled and fractionated by heparin-Sepharose chromatography to determine if the heat labile mitogen in vitreous was RDGF. From the insulin-dependent diabetic (IDDM) pooled vitreous sample, a prominent protein of 18 Kd was eluted from the column with 1.2 M NaC1, a characteristic of RDGF. This work suggests that both RDGF and the vitreous inhibitor are found in human vitreous, but their relative concentrations may change in the diabetic state so that retinal neovascularization from retina can occur.

Animals↗
PubMed1985

Observations on the retinopathy of prematurity.

The fourfold to fivefold increased survival rate since 1950 of premature infants with birthweights of less than 1,000 g apparently explains the increase in cases of retinopathy of prematurity in recent years. A new international classification permits standardized grading of the retinopathy of prematurity based on severity, anterior-posterior location, and the meridians involved. Previously reported clinical trials on the role of vitamin E in the prevention of retinopathy of prematurity have given conflicting results.

Carbon Dioxide↗
PubMed1985

Regulation of cell growth by vitreous humour.

Extracts of normal vitreous have been found to inhibit angiogenesis in two animal models: tumour-induced neovascularization in the rabbit corneal micropocket and retinal extract-induced angiogenesis in the chick chorioallantoic membrane assay. Using in vitro assays, we have found recently that an extract of bovine vitreous, free of hyaluronic acid, inhibits proliferation of cells in the aortic wall, i.e. endothelium and smooth muscle cells, as well as capillary and corneal endothelium. The inhibition is dose-dependent, as determined by either cell count or [3H]thymidine incorporation, and not due to cytotoxicity, as demonstrated with a double-label thymidine assay. The inhibitor is trypsin-sensitive and heat-stable (95 degrees C for 10 min). Conversely, proliferation of pericytes, lens epithelium and fibroblasts (dermal and corneal) was stimulated by the vitreous extract. This mitogenic activity was heat-labile. Growth of pigment epithelium and several tumour cell lines was unaffected. The data demonstrate that normal vitreous contains a heat-stable growth inhibitor specific for endothelium and smooth muscle cells, and a non-specific heat-labile mitogen. The paradoxical effect of this antiangiogenic factor on arterial and capillary contractile cells, smooth muscle and pericytes, suggests a basic difference in the regulation of the two vasculatures. The results suggest that a substance in normal vitreous may be important in controlling neovascularization that results from diabetic and other retinopathies, and could be useful for inhibiting tumour-induced angiogenesis.

Animals↗
PubMed1985

Argon laser debridement of the posterior capsule: a potential treatment for posterior capsule opacification after extracapsular cataract surgery.

We treated an opacified membrane on the anterior surfaces of the posterior capsule of two cynomolgus monkeys that had undergone extracapsular cataract extraction and intraocular lens insertion. After development of opacification of the posterior capsule, argon laser energy was employed in an attempt to debride the capsules while maintaining structural integrity of the capsule. With this technique, small areas of destruction of the membrane on the anterior surface of the posterior capsule were created with preservation of the capsule.

Animals↗
PubMed1984

Macular edema. A complication of diabetic retinopathy.

Diabetic macular edema is the leading cause of decreased vision from diabetic retinopathy. This decreased vision is caused by an increase in extracellular fluid within the retina distorting the retinal architecture and frequently taking on a pattern of cystoid macular edema. This fluid accumulates within the retina because of the breakdown of the barriers within the retinal blood vessels and possibly the pigment epithelium. Diabetic macular edema tends to be a chronic disorder. Although spontaneous recovery is not an uncommon occurrence, over one-half of diabetics with macular edema will lose two or more lines of visual acuity within two years. The most promising treatment for diabetic macular edema has been photocoagulation. It is recommended that in all patients with diabetic macular edema attempts be made to normalize elevated blood glucose, decrease elevated blood pressure, and improve cardiac or renal status. Reduction of serum lipids by diet or pharmacologic means is an unproven treatment at this time. The Early Treatment Diabetic Retinopathy Study hopefully will provide more definitive information as to whether photocoagulation is effective in various subgroups of patients with diabetic macular edema.

Blood Glucose↗