RETINAL VASCULAR DISORDERS
Loss of vision can occur from occlusion of a retinal artery or vein. Such occlusions may result from atherosclerosis, cardiac val-vular disease, venous stasis, hypertension, or increased blood viscosity.
Blood supply to and from the ocular fundus is provided by the central retinal artery and vein. Patients who have suffered a cen-tral retinal vein occlusion report decreased visual acuity, which may range from mild blurring to vision that is limited to only hand-motion vision.
Direct ophthalmoscopy of the retina shows optic disc swelling, venous dilation and tortuousness, retinal hemorrhages, cotton-wool spots, and a “blood and thunder” (extremely bloody) appear-ance of the retina. The better the initial visual acuity, the better the general prognosis.
Fluorescein angiography may show extensive areas of capillary closure. The patient should be monitored carefully over the en-suing several months for signs of neovascularization and neo-vascular glaucoma. Laser panretinal photocoagulation may be necessary to treat the abnormal neovascularization. Neovascular-ization of the iris may cause neovascular glaucoma, which may be difficult to control.
Some patients with branch retinal vein occlusions are symptom free, whereas others complain of a sudden loss of vision if the macular area is involved. A more gradual loss of vision may occur if macular edema associated with the branch retinal vein occlu-sion develops.
On examination, the ocular fundus appears similar to that found with central retinal vein occlusion; however, only those portions of the retina affected by the obstructive veins have what is known as a “blood and thunder” appearance. The diagnostic evaluation and follow-up assessments are the same as for central retinal vein occlusion. Potential complications are similar. Po-tential associated conditions include glaucoma, systemic hyper-tension, diabetes mellitus, hyperlipidemia, and hyperviscosity syndrome.
The patient with central retinal artery occlusion presents with a sudden loss of vision. Visual acuity is reduced to counting the ex-aminer’s fingers, or the field of vision is tremendously restricted. A relative afferent pupillary defect is present. Examination of the ocular fundus reveals a pale retina with a cherry-red spot at the fovea. The retinal arteries are thin, and emboli are occasionally seen in the central retinal artery or its branches. Central retinal artery occlusion is a true ocular emergency. Various treatments are used, including ocular massage, anterior chamber paracente-sis, intravenous administration of hyperosmotic agents such as acetazolamide, and high concentrations of oxygen.