Biomedical subjects
Publications and source records attributed to M F Rabb.
A young black girl with sickle cell B+ thalassemia sustained macular infarction of the right eye due to multiple arteriolar occlusions. Follow-up examination revealed optic atrophy as well as microvascular abnormalities of the right macula. To the authors' knowledge, this is the first reported case of macular infarction in sickle cell B+ thalassemia.
Observations of visual acuity and the conjunctival, macular, and perimacular vascularity have been assessed in patients with homozygous sickle cell (SS) disease. There were 17 matched pairs, each consisting of one patient with a high count (greater than or equal to 15%) and one with a low count (less than or equal to 5%) of irreversibly sickled cells (ISCs). The macular vascular bed was assessed by measurements of the foveal avascular zone (FAZ), perimacular avascular zones, and counts of perimacular vascular abnormalities (perimacular counts). Small foveal avascular zones and high perimacular counts were commoner in younger than older patients and there was a significant inverse correlation between size of the FAZ and the perimacular count. These observations were compatible with the hypothesis that perimacular vessel anomalies represent the early vaso-occlusive phase which progresses to ischaemia and the formation and enlargement of avascular areas. Visual acuity was assessed by Snellen's test type and by measuring contrast sensitivity. There was no obvious relationship between acuity measured by the 2 methods and no relationship between acuity and observations of macular vascularity. High ISC counts were significantly related to abnormalities of the conjunctival vasculature, but no relationship was noted with abnormalities of the macular vasculature or with visual acuity.
Coats' disease is characterized by vascular anomalies in the retina that are usually associated with exudates. In the absence of treatment the disease almost always progresses toward loss of vision and, often, loss of the eye. This report describes three patients in whom some of the retinal lesions apparently regressed spontaneously; only two other such patients are mentioned in the literature. These patients may have had a form of Coats' disease that has a better prognosis than usual for the eye.
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Six black patients had fundus lesions diagnostic of the presumed ocular histoplasmosis syndrome. All patients had peripapillary changes or peripheral punched-out chorioretinal lesions, or both. Five of the six had macular subretinal neovascularization, disciform scarring, or an atrophic macular lesion, and one patient had a macular hole; four of five patients tested had a positive histoplasmin skin test. The macular involvement was bilateral in three of the six cases. HLA B-7 was present in one of four patients who had HLA typing. Macular involvement can occur in blacks with the presumed ocular histoplasmosis syndrome.
Three cases of retrolental fibroplasia with vascular tufts at different locations are described. They probably represent mesenchymal proliferation in response to severe hypoxia. The tufts are reddish-pink in color and angiographically do not leak fluorescein. When present posterior to the equator they suggest an immature retinal circulation and the visual prognosis is poor.
True vitelliform dystrophy rarely appears in the adult population. We describe 10 cases in adults of bilateral vitelliform lesions clinically mistaken for Best's disease. Fluorescein angiography is a useful tool in distinguishing this dystrophy from Best's disease or other diseases. The angiographic findings suggest pigment epithelial disease. Adult vitelliform degeneration may lead to dry atrophic macular degeneration in a similar fashion as macular drusen. Symptoms and visual findings in these patients are fairly stable, and may be only slowly progressive in spite of ophthalmoscopic and fluorescein angiographic changes over a period of years. The electro-oculogram is useful in separating adult vitelliform macular degeneration from true vitelliform dystrophy.
Three patients with geographic choroiditis developed subretinal neovascular membranes associated with subretinal hemorrhage and serous elevation of the retina. Proximity of the membrane to the foveal avascular zone prevented photocoagulation of the neovascular membrane in one patient. Central visual acuity remained 6/60 (20/200) despite systemic corticosteroid therapy. The neovascular membranes in the other two patients were obliterated by argon laser photocoagulation with preservation of central vision. The inflammatory process of geographic choroiditis can disrupt Bruch's membrane, allowing occasional choroidal vascular growth. Concomitant destruction of choroidal vessels may account for rarity of subretinal neovascularization in geographic choroiditis.
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Three patients with vitelliform-like macular lesions had normal electroooculogram (EOG) light-peak/dark-trough ratios, unlike typical cases of vitelliform dystrophy (Best macular dystrophy). Leakage of fluorescein dye from perifoveal cappillaries implicated an increased permeability of these vessels as the probable cause for the vitelliform-appearing lesions. All patients with vitelliform lesions demonstrating normal EOG ratios should have an evaluation by fluorescein angiography to rule out a diagnosis of what we prefer to call pseudovitelliform macular degeneration.
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.
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.
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