Biomedical subjects
Publications and source records attributed to G K Asdourian.
Three young women with papilledema secondary to pseudotumor cerebri evolved mottled macular pigmentation with preservation of normal visual acuity. Choroidal folds or macular star figures were observed. These macular changes could represent the sequelae of either macular edema or a mechanical disruption of the retinal pigment epithelium. The mechanism of choroidal folds in papilledema remains uncertain.
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Disc swelling and hemorrhages appeared in three eyes of two men receiving amiodarone hydrochloride for cardiac arrhythmias. The initial diagnosis was ischemic optic neuropathy, but visual acuity was preserved, and visual field changes were present in only one eye. Amiodarone is a cationic amphiphilic compound, and other drugs with this property have keratopathy, retinopathy, and optic neuropathy as side effects. We believe our patients had an amiodarone-induced papillopathy.
Various diseases of the peripheral retinal vasculature, such as sickle cell retinopathy and Eales' disease, demonstrate vascular abnormalities. For comparative purposes, we documented angiographically the peripheral retinal vasculature in young, healthy subjects. Our findings showed the density of the capillary bed to be highest in the posterior pole and least concentrated toward the periphery. Peripheral capillaries are considerably larger than those found posteriorly and have fewer bifurcations. Our technique also detected the periarterial capillary-free zone and the zone without capillaries adjacent to the ora serrata. These aspects were consistent with findings of other investigators using in vitro techniques. By creating a standard of normalcy in vivo, the angiographic technique allows vascular abnormalities evident in diseases of the peripheral retinal vasculature to be more precisely defined and compared.
Five patients had macroaneurysms of the retinal arterioles. These macroaneurysms may be observed without pathologic sequelae or may be associated with circinate retinopathy, intraretinal hemorrhage, subretinal hemorrhage, or intravitreal hemorrhage. They may also evolve into more widespread vascular anomalies resembling adult Coats disease in some respects. Photocoagulation therapy is occasionally indicated.
Sixty-five patients with hemoglobins AS, SC, and SS were investigated in a masked fashion. We observed a statistically significant positive correlation between the severity of conjunctival sickling signs and the counts of irreversibly sickled cells in each hemoglobinopathy group. We also observed a statistically significant positive correlation between the severity of the conjunctival vasculopathy and the percentage of sickle hemoglobin in the total group of patients with hemoglobins AS, SC, and SS.
Fluorescein angiography during the choroidal phase of perfusion has been used to study the origin of blood vessels comprising neovascular tissue of the disc. These newly formed vessels were shown to derive their blood supply primarily from the uveal circulation rather than from the retinal circulation. This is related to the observation that many normal disc blood vessels originate from the choroidal or posterior ciliary circulation.
With prospective observations we have documented by fluorescein angiography the development of retinal neovascularization in the eyes of patients with sickle cell-hemoglobin C disease (hemoglobin SC). In each patient, arteriolarvenular (AV) anastomoses occurred before the development of neovascular sea fans. To our knowledge, this report constitutes the first such documentation in the literature. New sea fans from AV anastomoses appeared throughout an average interval of 18 months (range, 8 to 36 months) in approximately 21% of young adults with hemoglobin SC. Each year approximately 14% of young patients with hemoglobin SC may develop retinal neovascularization.
Seven patients had sickle cell trait (hemoglobin AS) and vasoproliferative retinopathy. The retinal abnormalities in these seven patients were indistinguishable from those seen in patients with clinically significant sickling hemoglobinopathies (sickle cell-hemoglobin C disease, hemoglobin S-thalassemia disease, and sickle cell anemia). All seven patients also had some evidence of associated systemic disease such as diabetes, syphilis, tuberculosis, or sarcoidosis. In the presence of an associated systemic disease, marked retinopathy can occur in the ordinarily benign condition of sickle cell trait.
Acute choroidal vascular insufficiency as a complication of photocoagulation has been little noticed. In 17 eyes of 16 patients photocoagulated with either xenon or argon sources for proliferative sickle cell retinopathy, gray lesions of the fundus developed peripheral to the photocoagulation sites. Histologic examination of similar gray lesions produced in monkeys showed necrosis and atrophy of the outer half of the retina. Intense photocoagulation of the human fundus, even with smaller spot sizes, may occlude a choroidal artery, producing separate gray lesions of distinctive shape. The lesions in both the patients and the monkeys progressed to granular hyperpigmentation by two to three weeks after photocoagulation.
The posterior pole vasculature of 100 patients with different sickling haemoglobinopathies was studied prospectively over a period of three years. Various abnormalities of the posterior pole vasculature were seen in 29 per cent of the patients. Continuous remodelling of the macular and perimacular vasculature occurred. Visual acuity was variably affected and sometimes remained intact.
The unique problems encountered in sickle patients include the need to remove peripheral vitreous if perfusing sea fans-which can bleed after vitrectomy-are present at the time of surgery. However, peripheral vitrectomy is riskier than central vitrectomy alone. If visualization of the sea fans is sufficient, it is safer to close the sea fans prior to vitrectomy in order to obviate the need for peripheral vitrectomy; then, only central vitrectomy is performed. When sea fans cannot be closed prior to vitrectomy, peripheral vitreous is removed to allow early photocoagulation of the sea fans before they bleed again. Four case presentations illustrate these principles. Vitrectomy relieved severe vitreous traction that complicated retinal detachment in the fifth patient, thereby eliminating the need for a tight encircling structure, which can be poorly tolerated in patients with SC hemoglobin.
Argon laser photocoagulation performed to destroy retinal neovascularization in two patients with proliferative sickle retinopathy and one patient with sarcoidosis was complicated by the development of choroidal neovascular tissue that extended through the photocoagulated retina into the vitreous. Attempts to obliterate the neovascular growth were successful in two cases. In the case that did not respond to repeated therapeutic procedures, the possibility of a direct communication with the long posterior ciliary artery was suggested by the presence of a chorioretinal defect in the vicinity of the photocoagulated area.
Three black patients with peripheral retinal sea fan neovascularization were found to have sarcoidosis. The periphlebitic process may be the cause of stasis, hypoxia, and a secondary vasoproliferative stimulus. We noted the peculiar finding of a vessel passing through the neovascular tissue into the peripheral retina. This feature may help in the differential diagnosis.
Of 45 patients with proliferative sickle retinopathy in stages III, IV, and V, nine patients (eight with hemoglobin SC disease, one with sickle cell thalassemia) showed spontaneous regression (autoinfarction) of retinal sea fans. One mechanism involved in autoinfarction of neovascular tissue is progressive, centripetal retraction of the anterior vascular arcade of the peripheral retina. In addition, vitreous traction on feeder vessels may result in sluggish blood flow and occlusion of these vessels, or may tear the sea fan completely away from its feeder vessels. In view of the many incidences of vitreous hemorrhages that occur in patients with proliferative retinopathy, however, we recommend treatment of neovascularization rather than prolonged observation.
Periodic photographic and angiographic surveys of patients with the earliest stages of sickle retinopathy showed a number of fundus findings. In seven cases (sickle cell anemia, four; sickle cell hemoglobin C, three), these findings included: (1) a variety of vascular abnormalities in the equatorial and post-equatorial retina such as segmented dilations of the vessel walls, hairpin-shaped vascular loops, hypertrophic, tortuous A-V anastomoses, intraluminal plugs, closure and loss of capillary bed, and terminal budding of capillaries; and (2) a continuous, spontaneous remodeling of the peripheral retinal vasculature due to successive closures and reopenings of equatorial retinal vessels. A centripetal recession of the peripheral retinal vasculature usually resulted. No correlation between the ophthalmoscopic and the systemic condition of the patients could be made.