Biomedical subjects
Publications and source records attributed to J G Diamond.
The Macular Photocoagulation Study criteria require that at least 1.5 clock hours of temporal peripapillary retina be spared when treating choroidal neovascular membrane in that location. The authors successfully treated peripapillary choroidal neovascular membrane involving temporal 180 degrees with the krypton laser without any loss of visual acuity and central field.
Choroidal neovascular membrane in the macular area is one of the leading causes of severe visual loss. Usually a manifestation in elderly population, it is often associated with age-related macular degeneration. The current mainstay of management is early diagnosis, usually by fundus examination, aided by angiography and photocoagulation in selected cases. Various other modalities of treatment including surgery are being considered as alternate options, but with limited success. The purpose of this review is to briefly outline the current concepts and the management strategy from a clinician's viewpoint.
We studied the use of human retinal pigment epithelial cells cultured on a collagen support as a potential transplantation therapy to replace diseased or damaged retinal pigment epithelium. Using a transvitreal approach, we transplanted human retinal pigment epithelial cells attached to either a sheet of noncross-linked or cross-linked type I collagen into the subretinal space of New Zealand white rabbits, whose eyes lack pigment. Animals were killed after six weeks, and the eyes were fixed for light microscopy. The results demonstrated that, in eyes receiving the noncross-linked collagen support, a layer of pigmented donor retinal pigment epithelium was visible within the subretinal space, with a normal-appearing retina and no evidence of proliferative vitreoretinopathy or graft rejection. We believe this method may be applicable to replace dysfunctional retinal pigment epithelial cells in humans.
Twenty-five consecutive cases of culture-proven postsurgical endophthalmitis were evaluated. Patients underwent wound revision and pars plana vitrectomy with intravitreal antibiotic and steroid infusion (gentamicin 8 micrograms/cc, clindamycin 9 micrograms/cc, dexamethasone 8 micrograms/cc) and injection (gentamicin 100 micrograms plus clindamycin 200 micrograms [and amphotericin 5 micrograms in one case] and dexamethasone 800 to 1000 micrograms). Twenty cases demonstrated wound defects (eg, wound gape/malapposition, abscess/tissue necrosis, suture dehiscence, leak, vitreous wick). Culture-proven isolates included both gram negative and positive bacteria and fungi. Visual acuity improved in 18 of the 20 (90%) gram positive cases. Ten of the 17 (59%) patients in the Staphylococcus epidermidis subgroup achieved a visual acuity of 20/50 or better. Surgical wound defects are frequently associated with culture-proven endophthalmitis. When vitrectomy is included as part of the treatment regimen, we recommend meticulous inspection and closure of any defective surgical wounds associated with endophalmitis.
Retinal arterial macroaneurysms are distinct vascular lesions with a typically benign course. Laser treatment to these vascular lesions is controversial, and has been limited to cases of persistent macular edema. Devastating vision loss can occur, however, through vitreous or subretinal hemorrhage. We describe eight cases of retinal arterial macroaneurysms associated with subretinal or vitreous hemorrhage requiring pars plana vitrectomy. Final visual acuities ranged from 20/20 to 20/400 at most recent follow up. Until reliable indicators of rupture are identified, we suggest consideration of laser photocoagulation to clinically active, identifiable retinal arterial macroaneurysms within the macula.
We studied zinc uptake by nonhuman primate retinal pigment epithelium (RPE) and choroid, using 65Zn as a probe. With intravenously administered 65ZnCl2, virtually all detectable tracer was lost from the plasma after 20 hours but the pigment epithelium-choroid showed prominent uptake and retention. Plasma concentrations of oral 65ZnO remained high 20 hours after feeding. Uptake and retention of orally administered 65Zn as 65ZnO from the bloodstream by the RPE/choroid was avid in both young and old animals. Excretion in urine and feces was minimal. All pigmented ocular tissues took up and retained 65Zn. A survey of total zinc content of human and nonhuman primate ocular tissues showed that the pigmented tissues had consistently higher concentrations of zinc. Our results demonstrate for the first time direct uptake and retention of zinc from the blood by primate RPE and other ocular tissues.
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The histologic and clinical effect of intravitreal dexamethasone was studied in a rabbit model of experimentally induced gentamicin sensitive Staphylococcal epidermidis endophthalmitis. The study compared four treatment groups: vitrectomy alone (group I), vitrectomy plus intravitreal gentamicin (group II), vitrectomy plus intravitreal gentamicin and dexamethasone (group III), and intravitreal gentamicin and dexamethasone without vitrectomy (group IV). All eyes treated with dexamethasone, with or without vitrectomy, exhibited less clinical and histologic manifestations of inflammation. This study suggests that suppression of inflammation through the use of intravitreal dexamethasone leads to preservation of ocular architecture with potentially improved retinal function and visual benefit.
Eleven infants and children presenting for daily radiotherapy for a period of at least 2 weeks were anaesthetised with isoflurane in 33% oxygen and nitrous oxide. They were unpremedicated and given no other agents to supplement anaesthesia. The average number of exposures was 24 (SD 11; range 10-39) and the total anaesthetic time per exposure varied between 15 and 30 minutes. Liver function was assessed by determining serum total bilirubin, aspartate amino transferase, gamma glutamyl transferase and alkaline phosphatase before the start of treatment and at 5-daily intervals thereafter. There was no measurable change in any of these determinants of liver function. All children accepted daily induction of anaesthesia with isoflurane. Induction, maintenance and recovery from anaesthesia were uncomplicated.
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The use of intraocular thrombin to control intraoperative hemorrhage is presented in two cases, one involving severe ocular trauma, the other severe proliferative diabetic retinopathy. The technique of intermittent boluses of 100 units/ml of thrombin in BSS Plus solution has certain advantages over the constant infusion mode of delivery. The ability to quickly manipulate the flow offers a distinct advantage in controlling the intraocular pressure and total amount of thrombin delivered. This is achieved by a simple and uncomplicated modification of the standard gravity infusion controlled by the surgical assistant.
Three cases of bullous superior rhegmatogenous retinal detachment were surgically repaired by circumferential scleral buckling and intravitreal air injection. Unusual retinal folds were found postoperatively. Unlike the well-recognized radial retinal folds classically associated with circumferential buckling of bullous retinal detachments, the folds reported herein originated from the "end" of a hard silicone exoplant and traversed an arcuate course corresponding to the lower meniscus of the intravitreal air bubble. Although the macula was involved in all three cases, the retinal break was unaffected.
Thirty-four patients underwent eye wall resection for choroidal malignant melanoma over a period of more than ten years. Of these, 11 eyes were later enucleated for complications. Average mean follow-up has been more than 5.3 years. Postoperative visual acuity ranged from light perception to 20/30. Two patients developed liver metastasis 4 years following eye wall resection and later died. However, no local metastasis has been observed. Two patients died from unrelated causes.
Antibiotics were administered intravitreally to 26 patients with culture-verified endophthalmitis. Vitrectomy surgery was combined with intravitreal antibiotic therapy in 14 of the cases. Pretreatment selection into a vitrectomy or nonvitrectomy group was determined by the duration of the disease, type of predisposing injury, and echographic findings. This diagnostic-treatment grouping allowed management to be initiated on the basis of the existing and potential virulence of the infecting process. The less virulent and often successfully managed Staphylococcus epidermidis accounted for 67% of cases in the nonvitrectomy group and only 14% in the vitrectomized series. During a mean follow-up period of 32 months (range, one to five years), retinal changes were monitored by visual acuity determination, electroretinography, and fluorescein angiography. An overall visual improvement (greater than or equal to 20/400) was found in 73% of the eyes treated. The causes for failure in the remaining cases may be related to retinal damage from the initiating trauma, organism response, and intraocular antibiotic therapy.
A prospective, randomized, double-blind study showed that glutathione-bicarbonate-Ringer's solution (BSS Plus) caused significantly less corneal swelling on the first postoperative day after pars plana vitrectomy than did lactated Ringer's solution. By the seventh postoperative day, no difference was seen between the two solutions. We found no correlation between the increase in corneal thickness and either the duration of intraocular irrigation or the volume of solution used or the presence or absence of the lens. No persistent corneal complications were seen.
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