Search PubMed⌕ Search

Biomedical subjects

D J Apple

Publications and source records attributed to D J Apple.

At least 235 records · Page 13Linked to original sources
PubMed1976

Experimental argon laser photocoagulation. I. Effects on retinal nerve fiber layer.

Eight rhesus monkeys were photocoagulated with varying intensities of argon laser energy to determine the effects on the retinal nerve fiber layer. Photocoagulation of arterioles and venules always resulted in largely irreversible and permanent perivascular axonal destruction. Photocoagulation of areas free of major vessels showed variable responses to identical dosages, ranging from minimal destruction of the outer part of the retina to full-thickness destruction involving the nerve fiber layer. Variations in retinal thickness, vascularity, pigment epithelial pigmentation, and focus of the laser beam are responsible for differences in severity of each burn. Even when major vessels are avoided, it is impossible to predict accurately the degree of damage. However, our studies suggest that much of the initial damage is extracellular, sparing nerve fiber layer axons. Therefore, some acute damage might be reversible following resorption of the edema.

Animals↗
PubMed1976

Experimental argon laser photocoagulation. II. Effects on the optic disc.

Eight monkeys and five humans were subjected to photocoagulation with single argon laser burns of varying intensity on the optic nerve head. Energies greater than 400 milliwatts, 0.2 second and 100 mu spot size consistently caused neural parenchymal damage, even in the absence of heat-generating pigment epithelium. Papillary burns in monkeys and humans created with powers less than 400 mW showed only small, focal submicroscopic areas of degeneration, and were therefore considered relatively safe except for the occasional involvement of critical foveal fibers in which scotomas of disproportionately greater severity than one would expect from the size of the lesion could result. The threshold for toxicity following peripapillary photocoagulation is lower, because the burned pigment epithelium can radiate heat into the adjacent optic nerve fibers. Normal capillaries within the optic nerve were seldom destroyed or occluded, even after high energy densities. In normal vessels, we have found it impossible to create a highly selective lesion without concurrently causing neural damage about the vessel.

Adult↗
PubMed1976

Experimental argon laser photocoagulation. III. Relative dangers of immediate vs delayed retreatment.

Monkey retinas were studied histopathologically to assess the relative effects of immediate versus delayed repetitive photocoagulation with the argon laser. Immediate retreatment adds relatively little damage to that created in the retinal nerve fiber layer by the initial photocoagulation. Delayed retreatment increases destruction of all retinal layers, including the nerve fiber layer, and also increases the chance of inducing hemorrhage. When argon laser retreatment of a retinal locus is necessary, it is much safer to do so immediately (within a few hours) rather than after days or weeks.

Animals↗
PubMed1975

Histopathology after vitrectomy with the vitrophage.

A 72-year-old adult-onset diabetic woman underwent vitrectomy with the vitrophage because of persistent vitreous hemorrhage. Postoperatively a hyphema developed and elevation of intraocular pressure was refractory to medical management. Intraocular pressure was controllable within normal limits after vitreous lavage. Eleven days after vitreous lavage the patient died from pulmonary embolization. Histologic sections demonstrated a flat pars plana over the sclerotomy site with vitreous condensation along the internal aspect of the wound. Rubeosis iridis was postulated as the source of the hyphema. A hemolytic mechanism may have caused the elevated intraocular pressure.

Aged↗
PubMed1975

Biopsy of human scleral-chorioretinal tissue.

The usefulness of a technique for scleral-chorioretinal biopsies was evaluated on a human eye destined for enucleation due to a malignant melanoma of the choroid. The operative procedure was without complication. The biopsy specimen was removed and carefully evaluated both by light and electron microscopy. The underlying choroid and retinal tissues were successfully preserved by this technique.

Aged↗
PubMed1975

Retinal and pigment epithelial alterations over choroidal malignant melanomas.

Although in some cases orange or yellow-orange pigment overlying a malignant choroidal melanoma may represent lipofuscin, a case is presented which showed extensive yellow-orange coloration overlying a malignant choroidal melanoma without any demonstrable lipofuscin on histopathologic and electron microscopic analysis. Our findings suggest that other mechanisms, such as serous fluid or lipid deposition within retinal cystoid spaces or diffuse drusen, can clinically stimulate the yellow-orange pigment associated with lipofuscin.

Adult↗