Classification and pathogenesis of proliferative sickle retinopathy

Alteration of the blood-retinal barrier and vitreous in sickle cell retinopathy

Nineteen eyes with background sickle cell retinopathy, eleven from patients with SC disease, eight from patients with SS disease, and twelve eyes with proliferative sickle cell retinopathy were examined by direct and indirect ophthalmoscopy, slit-lamp, fluorescein angiography and vitreous fluorophotometry. Calculation of the alteration of the blood-retinal barrier (BRB) and estimation of the diffusion coefficients of fluorescein in the vitreous were performed by fluorophotometry. In background sickle cell retinopathy, the results show a normally functioning BRB in the posterior pole. Abnormally increased fluorescence values to the mid-vitreous (peripheral leakage) were found only in 3 of these 19 eyes, at the two-hour examination (all SC patients). Similarly, mid-vitreous fluorescence values at the two-hour examination were 4.19 +/- 1.52 ng/ml in eyes of patients with SC disease, compared with 2.65 +/- 0.56 ng/ml in eyes of patients with SS disease. All eyes with background sickle cell retinopathy, except one, showed values for the coefficient of diffusion of fluorescein within normal limits, indicating normal vitreous gel structure. In proliferative retinopathy, the mid-vitreous fluorophotometry readings were abnormally increased, correlating well with the extent of the peripheral angiographic changes (neovascularization). The coefficient of diffusion of fluorescein in the vitreous was generally increased in the eyes with proliferative retinopathy (15.0 +/- 8.4 X 10(-4) cm2/min) in comparison with a mean value of 5.4 +/- 1.4 X 10(-4) cm2/min in the eyes with background sickle cell retinopathy, suggesting an alteration of the vitreous structure eyes with proliferative retinopathy. Fluorophotometry is considered a useful tool to follow patients with sickle cell retinopathy by quantitating peripheral retinal vascular leakage.

Retinal neovascularisation: early contributions of Professor Michaelson and recent observations

The late Professor I. C. Michaelson's pioneer contributions to the development and pathophysiology of the retinal vasculature have laid the groundwork for a generation of ophthalmic research scientists to pursue this exciting field of investigation. In more recent studies it has been found that, in diabetic retinopathy, branch vein occlusion, sickle cell retinopathy, and retrolental fibroplasia, retinal neovascularisation follows the development of retinal capillary closure. The capillary closure or nonperfusion has been demonstrated by fluorescein angiography. A working hypothesis to explain the clinical and experimental observations is that these areas of nonperfused retina are ischaemic or hypoxic and liberate a theoretical angiogenic or vasoproliferative substance which stimulates the development of retinal neovascularisation. In postulating this working hypothesis it is important to recognise, firstly, that this hypothesis remains to be proved, and, secondly, that retinal neovascularisation may develop from other stimuli such as intraocular inflammation where retinal ischaemia is not apparent.

Clinical and experimental studies on retinal neovascularization. XXXIX Edward Jackson Memorial Lecture

Retinal neovascularization is a serious complication of the retinopathy associated with diabetes, branch vein occlusion, sickle cell anemia, and retrolental fibroplasia. Retinal capillary nonperfusion, demonstrated on fluorescein angiography, precedes the development of neovascularization in each of these conditions. Our working hypothesis is that the nonperfused (ischemic or hypoxic) retina liberates a vasoproliferative or angiogenic substance. Although I have delineated the clinical and experimental observations relating to the hypothesis of an ischemic-mediated angiogenesis substance, other postulated mechanisms for the development of retinal neovascularization may be involved. Recent observations on the experimental model of retrolental fibroplasia have demonstrated the markedly abnormal persistence and apparent proliferation of the hyaloid vessels in mice following oxygen-induced retinal vascular closure.

A low-molecular-weight angiogenic factor in cat retina

A low-molecular-weight angiogenic factor has been isolated from healthy adult cat retinas. The factor, which has been purified by diethylaminoethyl (DEAE) cellulose chromatography and affinity chromatography, stimulates neovascularisation of the chick chorioallantoic membrane and has a number of properties similar to those previously described for a tumour factor. The finding of an angiogenic factor in healthy retina and its relationship to previously described inhibitors of angiogenesis is discussed.

Sickle cell retinopathy in young children in Jamaica

Ophthalmological examinations were performed on 59 of the 74 (80%) children with homozygous sickle cell (SS) disease and on 37 of the 54 (69%) children with sickle cell-haemoglobin C (SC) disease, aged 5-7.5 years, within the cohort study of sickle cell disease. Arteriolar sheathing was the commonest retinal vessel abnormality, occurring in 30/59 (51%) SS children and in 11/37 (30%) SC children. Peripheral arteriolar closure was observed in 14 (24%) SS children and in 6 (16%) SC children. Arteriovenous anastomoses were seen in 3 children, but proliferative retinopathy was not identified. Capillary changes often occurred in patients without confluent closure, suggesting that complex remodelling of the capillary bed may precede retinal non-perfusion. Discrete retinal patches similar to schisis cavities resulting intraretinal haemorrhages were found in 22 (37%) SS children and in 9 (24%) SC children, but haemorrhages were observed in only 2 patients (1 SS, 1 SC). Vitreous opacities were common and were generally associated with retinal vessel disease. Retinal changes were consistently more common in children with SS disease, though the differences failed to reach statistical significance. The prevalence of peripheral vascular closure and retinal patches showed a significant upward trend with age. These observations contrast with the greater prevalence of proliferative retinopathy characterising SC disease in adults.

Talc retinopathy

Twenty-three patients had bilateral intraretinal talc microemboli, which were seen on ophthalmoscopic examination. Twelve of these patients had additional retinal vascular or choroidal abnormalities in the posterior pole that were confirmed by fluorescein angiography. Six patients had peripheral retinal neovascularization associated with peripheral retinal vascular nonperfusion. Of these six patients, three had associated vitreous hemorrhage, and two had optic disk neovascularization and traction retinal detachment. The progressive fundus changes seen in talc retinopathy were documented by fluorescein angiography and compared to those seen in sickle-cell retinopathy. One eye in one patient was treated by argon laser photocoagulation for proliferative retinopathy, and three eyes in two patients with vitreous hemorrhage were treated by pars plana vitrectomy.

Permanent retinal damage following massive dapsone overdose

A massive dose of 7.5 g of 4,4'-diamino, diphenyl sulphone (dapsone) taken as a suicide attempt in a patient on long-term therapy for tuberculoid leprosy resulted in permanent bilateral retinal necrosis, previously unreported side effect of this drug. The patient developed a severe haemolytic anaemia, methaemoglobinaemia, and acute renal failure requiring peritoneal dialysis. It is proposed that the retinal damage was due to a combination of severe hypoxaemia and the physical effects of red cell fragmentation producing vascular occlusion in the macular and perimacular region, with consequent ischaemic necrosis.

Peripheral proliferative retinopathies

Peripheral retinal neovascularization (i.e., new vessel growth peripheral to the major vascular arcades) may be secondary to a wide variety of ocular and systemic diseases. Vascular and inflammatory diseases in particular may cause peripheral neovascularization. Following a brief review of ocular angiogenesis, the various clinical entities that can cause peripheral retinal neovascularization are described. The diagnostic workup of a patient with peripheral proliferative retinopathy is outlined and techniques of treatment of the neovascularization (including feeder vessel technique, cryopexy, and panretinal photocoagulation) are discussed.

The demonstration of angiogenic activity from ocular tissues. Preliminary report

Human, bovine, and rabbit retinal extracts are shown to be capable of stimulating (1) proliferation and thymidine uptake of bovine vascular endothelial cells in cultures and (2) neovascularization of the chick chorioallantoic membrane (CAM). Extracts of skeletal muscle, heart, and liver lack similar stimulatory activity. Vitreous aspirates from patients with proliferative diabetic retinopathy, in a preliminary study, were able to stimulate vascular endothelial cell thymidine uptake. Most vitreous samples from patients without intraocular neovascularization lacked similar stimulatory activity. Indirect evidence suggests the liberation of an angiogenic factor from the retina in several ocular disorders. The data contained in this report represent the first direct evidence of angiogenic activity from mammalian retina.

Ocular findings in a case of haemoglobin H disease

A case is reported of a patient with known haemoglobin H disease who was found to have angioid streaks and retinal detachment. Angioid streaks have not previously been reported in cases of alpha-thalassaemia, and the question whether this is a chance association or otherwise is discussed.

Posterior pole neovascularization in a patient with hemoglobin SC disease

A 33-year-old black woman with hemoglobin SC disease and a history of photocoagulation for peripherally located retinal neovascularization had a neovascular frond at the temporal border of her right macula. Multiple zones of black sunburst hyperpigmentation were located nearby. Fluorescein angiography showed that the lesions were closely related to an extensive zone of avascular retina in the posterior pole. The perifoveal vasculature was uninvolved, and the patient was unaware of any visual deficit. Although sickle cell maculopathy is a well-recognized entity, there have been no published reports, to the best of our knowledge, of posterior pole neovascularization in patients with sickle cell hemoglobinopathy. The fluorescein angiographic findings in our case provide further support for the hypothesis that retinal hypoxia is an important stimulus for retinal neovascularization.

An examination of the possibilities of preventive therapy in arteriolar retinopathies

The identification of certain chronic vascular retinopathies has been marked by a search for their classification. Such proper classification has therapeutic implications. The similarities of these retinopathies are based on a shared pathogenic process, initiated by diminished arteriolar perfusion pressure, as the result of varied causes but leading to somewhat nonspecific capillary and reactive stages. On the basis of such a pathogenesis, various possible prophylactic and therapeutic measures and their organizational requirements are significant. These measures are directed to the correction of a blood perfusion pressure defect and to leaking capillaries and new vessels. Prophylactic and therapeutic exercises will be required for various chronic arteriolar capillaropathies, although the experience with one disease may be applicable to the others. Senile macular disciform degeneration provides the factors necessary for a therapeutic trial.

Self-injected retinal emboli

Twelve patients with bilateral intraretinal talc emboli were examined. Each patient had self-injected large doses of methylphenidate (Ritalin) for one or more years. All fundi showed yellow-white particles in the macular area, and two eyes had reduced vision secondary to retinal vascular occlusion. The clinical syndrome, ophthalmoscopic appearance, and fluorescein angiographic findings of self-injected retinal emboli are presented, and the pathogenesis is discussed.

Talc emboli and retinal neovascularization in a drug abuser

A 38-year-old male drug abuser had multiple emboli in the retinal circulation of the posterior pole of both eyes. He showed widespread peripheral retinal capillary nonperfusion and neovascular proliferation at the junction of perfused and nonperfused retina. The emboli were considered to be talc particles from the intravenous administration of suspensions of oral medications. The presumed mechanism of development of neovascularization in this case was the filtering out of the particles by the retinal vasculature with vaso-occlusion, ischemia and subsequent retinal neovascularization.

Optic disk neovascularization in hemoglobin SC disease

A 37-year-old black man had a clinically documented case of optic disk neovascularization associated with hemoglobin SC disease. Through medical evaluation, we ruled out other disorders associated with proliferative retinopathy. Extensive areas of retinal nonperfusion were associated with vasoproliferative retinopathy at the junction of the perfused and nonperfused retina; and a delicate network of neovascularization extended from the optic disk into the vitreous gel in one eye.

Ocular manifestations of sickle hemoglobinopathies

The ocular manifestations of sickle cell hemoglobinopathies, while often not severe enough to affect vision, may develop in proliferative stages, resulting in arteriolar-venular anastomoses, neovascular proliferations, vitreous hemorrhage and retinal detachment. The authors review the historical, biochemical, and geographic aspects of the disease, and provide detailed descriptions of findings in theconjunctiva, uvea and fundus, with particular emphasis on the retina. Pathogenesis, histopathologic and clinical appearance, and modes of treatment are discussed.

Occlusive retinal arteriolitis with neovascularization

A 34-year-old white woman who had used oral contraceptives for six years showed an occlusive bilateral retinal arteriolitis that resulted in a branch arteriolar occlusion in the right eye and retinal neovascularization. Three years later, we observed active arteriolitis in the left eye with successive occlusion of several branch arterioles. The disease has shown spontaneous remissions and exacerbations. An extensive medical evaluation revealed only old pulmonary granulomatous disease and an elevated sedimentation rate in association with exacerbations of the arteriolitis.

Severe proliferative retinopathy as the only sign of sickle cell hemoglobin C disease

A 48-year-old black woman developed severe bilateral hypoxic proliferative retinopathy without other clinical manifestations. The hemoglobin level was 10.6 to 11.5 g/100 ml, reticulocyte level was 2.2%, targeted and sickled red blood cells were seen on blood smears, and hemoglobins S and C were demonstrated by electrophoresis. Glucose tolerance test was normal. The development of neovascular proliferation, vitreous hemorrhage, and retinal detachment unassociated with other clinical symptoms is unusual in sickle cell hemoglobin C disease.

Regional ischemic infarcts of the retina

Macroscopic and light microscopic features of regional ischemic infarcts of retina in autopsy eyes are described. Lesions were found throughout life span, most patients having significant primary or secondary vascular disease (younger had systemic hypertension, rheumatic heart disease, vasculitis or sickle hemoglobinopathy; most older patients had arteriosclerosis). Diabetes mellitus and infarction of other organs (including brain) also were common. Topographically almost all lesions were found in posterior fundus; most were temporal and involved anatomical macula. Microscopically there was destruction of inner retinal layers with preservation of outermost cells of inner nuclear layer; occasionally ganglion cell layer was relatively spared.

Spontaneous regression (autoinfarction) of proliferative sickle retinopathy

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.

Peripheral retinal microaneurysms in chronic leukemia

Of 25 patients with chronic leukemia, there was clinical evidence of peripheral retinal microaneurysm formation in two of eight patients with chronic lymphocytic leukemia and six of 17 patients with chronic myelogenous leukemia. There was no proliferative retinopathy in any of the 25 patients. An elevated leukocyte count seemed necessary for microaneurysm formation in leukemia, although some patients with elevated counts had no microaneurysms. The prolonged leukocytosis of chronic leukemia can produce peripheral capillary dropout, vascular stagnation, microaneurysm formation, and, rarely, peripheral proliferative retinopathy similar to sickle cell disease.

Spontaneous remodeling of the peripheral retinal vasculature in sickling disorders

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.

Recent advances in fluorescein fundus angiography

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