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We conducted a prospective, planned study of argon laser panretinal photocoagulation (PRP) in ischemic central retinal vein occlusion (CRVO) over a 10-year period in 123 eyes. On comparing the lasered eyes versus the nonlasered eyes, there was no statistically significant difference between the two groups in the incidence of development of angle neovascularization (NV), neovascular glaucoma (NVG), retinal and/or optic disc NV, or vitreous hemorrhage, or in visual acuity. Our study, however, did show a statistically significant (P = 0.04) difference in the incidence of iris NV between the two groups, with iris NV less prevalent in the laser group than in the nonlaser group, but only when the PRP was performed within 90 days after the onset of CRVO. The other parameter which showed a statistically significant difference between the two groups was the peripheral visual fields-the laser group suffered a significantly (P less than or equal to 0.03) greater loss than the non-laser group. We discuss the implications of these findings in light of the natural history of ischemic CRVO and of ocular NV. Since the original rationale for advocating PRP in ischemic CRVO was the proven beneficial effect of PRP on ocular NV in proliferative diabetic retinopathy, we also discuss the disparities in the disease process between ischemic CRVO and proliferative diabetic retinopathy and in their responses to PRP.

Experimental renovascular malignant arterial hypertension was produced by modified Goldblatt’s procedures, in 60 rhesus monkeys, and various retinal arteriolar changes in hypertensive retinopathy were studied in detail (by serial ophthalmoscopy, and stereoscopic color fundus photography and fluorescein fundus angiography on long-term follow-up). The retinal arteriolar changes, in ophthalmoscopically visible arterioles, consisted of arteriolar sclerosis and associated changes, e.g., increased arteriolar tortuosity, arteriolar narrowing and in some animals occlusion and sheathing of the fine arterioles; we could find no evidence of localized or generalized ‘spasm’ in these retinal arterioles. Eyes in animals with accelerated arterial hypertension revealed focal dilatation and leakage of the retinal precapillary terminal arterioles (resulting in development of focal intraretinal periarteriolar transudates), and also occlusion of the terminal retinal arterioles (producing cotton-wool spots and associated intraretinal microvascular abnormalities). We discuss the controversial subjects of narrowing (particularly ‘spasm’) of ophthalmoscopically visible retinal arterioles and of fibrinoid necrosis in malignant hypertension.

We produced experimental renovascular malignant arterial hypertension by modified Goldblatt’s procedures, in 60 rhesus monkeys. Hypertensive retinopathy was studied in detail (by ophthalmoscopy, and stereoscopic color fundus photography and fluorescein fundus angiography on long-term follow-up). Cotton-wool spots (CWSs) were found to be an important, early retinal lesion. On ophthalmoscopy, they had a characteristic appearance. Fluorescein fundus angiography of these lesions revealed focal retinal capillary nonperfusion. The CWSs usually lasted for over 3 weeks and resolved within 6 weeks, leaving permanent obliteration of the retinal capillaries in their distribution, secondary intraretinal microvascular abnormalities, and retinal nerve fiber loss. We discuss pathogenesis and other features of CWSs. There is overwhelming evidence that CWSs are due to occlusion of the terminal retinal arterioles, resulting in acute focal inner retinal ischemia; hence the scientifically valid term for them would be ‘inner retinal ischemic spots’.

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