Vascular retinopathies
Vascular retinopathies: Excerpt from Handbook of Diseases
Vascular retinopathies are noninflammatory retinal disorders that result from interference with the blood supply to the eyes. The five distinct types of vascular retinopathy are central retinal artery occlusion, central retinal vein occlusion, diabetic retinopathy, hypertensive retinopathy, and sickle cell retinopathy.
Causes
When one of the arteries maintaining blood circulation in the retina becomes obstructed, the diminished blood flow causes visual deficits.
Central retinal artery occlusion
This form of vascular retinopathy may be idiopathic or may result from embolism, atherosclerosis, infection, or conditions that retard blood flow, such as carotid occlusion and heart valve vegetations. Central retinal artery occlusion is rare and occurs unilaterally; it affects elderly patients as well as younger patients with valvular disease.
Central retinal vein occlusion
Causes of central retinal vein occlusion include external compression of the retinal vein, trauma, diabetes, thrombosis, granulomatous diseases, generalized and localized infections, glaucoma, and atherosclerosis. This form of vascular retinopathy is most prevalent in elderly patients.
Diabetic retinopathy
This form results from juvenile or adult diabetes. Microcirculatory changes occur more rapidly when diabetes is poorly controlled. About 75% of patients with juvenile diabetes develop retinopathy within 20 years of onset of diabetes.
In adults with diabetes, incidence increases with the duration of diabetes; 80% of patients who have had diabetes for 20 to 25 years develop retinopathy. This condition is a leading cause of acquired adult blindness.
Hypertensive retinopathy
This form results from prolonged hypertensive disease, producing retinal vasospasm, and consequent damage and arteriolar narrowing.
Sickle cell retinopathy
This form results from impaired ability of the sickled cell to pass through the microvasculature, producing vasocclusion. This results in microaneurysms, chorioretinal infarction, and retinal detachment.
Signs and symptoms
The following features characterize vascular retinopathy.
Central retinal artery occlusion
This type of occlusion produces sudden, painless, unilateral loss of vision (partial or complete). It may follow amaurosis fugax or transient episodes of unilateral loss of vision lasting from a few seconds to minutes, probably due to vasospasm.
This condition typically causes permanent loss of vision. However, some patients experience spontaneous resolution within hours and regain partial vision.
Central retinal vein occlusion
Occlusion of this type causes reduced visual acuity, allowing perception of only hand movement and light. This condition is painless, except when it results in secondary neovascular glaucoma (uncontrolled proliferation of weak blood vessels). Prognosis is poor — 5% to 20% of patients with this condition develop secondary glaucoma within 3 to 4 months after occlusion.
Diabetic retinopathy
Nonproliferative diabetic retinopathy produces changes in the lining of the retinal blood vessels that cause the vessels to leak plasma or fatty substances, which decrease or block blood flow (nonperfusion) within the retina. This disorder may also produce microaneurysms and small hemorrhages.
Although nonproliferative retinopathy causes no symptoms in some patients, in others fluid leakage into the macular region causes significant loss of central visual acuity (necessary for reading and driving) and diminished night vision.
Proliferative diabetic retinopathy produces fragile new blood vessels on the disk and elsewhere in the fundus (neovascularization). These vessels can grow into the vitreous and then rupture, causing vitreous hemorrhage with corresponding sudden vision loss.
Scar tissue that may form along the new blood vessels can pull on the retina, causing macular distortion and even retinal detachment.
Hypertensive retinopathy
Symptoms of hypertensive retinopathy depend on the location of retinopathy. For example, mild visual disturbances such as blurred vision result from retinopathy located near the macula.
Without treatment, the prognosis is poor (50% of patients become blind within 5 years). With treatment, the prognosis varies with the severity of the disorder. Severe, prolonged disease eventually produces blindness; mild, prolonged disease, visual defects.
Diagnosis
Appropriate diagnostic tests depend on the type of vascular retinopathy. (See Diagnosing of vascular retinopathies.) Always include determination of visual acuity and ophthalmoscopic examination.
Treatment
The following measures are used to treat vascular retinopathy.
Central retinal artery occlusion
No treatment has been shown to control central retinal artery occlusion. However, an attempt is made to release the occlusion into the peripheral circulation.
To reduce intraocular pressure, treatments include immediate ocular massage, anterior chamber paracentesis after anesthetizing the surface with topical cocaine 2% to 4% drops, acetazolamide 500 mg I.V., and inhalation of carbogen (95% oxygen and 5% carbon dioxide) to improve retinal oxygenation. Because inhalation therapy may be given hourly for up to 48 hours, the patient should be hospitalized so vital signs can be monitored.
If the patient is young, the source of the occlusion may be the heart. Echo-cardiography may be necessary. Treatment in this case is to heparinize the patient.
Central retinal vein occlusion
Therapy for central retinal vein occlusion may include aspirin, which acts as a mild anticoagulant. Laser photocoagulation can reduce the risk of neovascular glaucoma for some patients whose eyes have widespread capillary nonperfusion.
Diabetic retinopathy
Treatment of nonproliferative diabetic retinopathy is prophylactic. Careful control of blood glucose levels during the first 5 years of the disease may reduce the severity of the retinopathy or delay its onset.
Patients with early symptoms of microaneurysms should have frequent eye examinations (3 to 4 times a year); children with diabetes should have an annual eye examination.
Treatment for proliferative diabetic retinopathy is laser photocoagulation, which cauterizes the leaking blood vessels, thereby eliminating the cause of the edema. Laser treatment may be focal (aimed at new blood vessels) or panretinal (placing burns throughout the peripheral retina).
Despite treatment, neovascularization doesn’t always regress, and vitreous hemorrhage, with or without retinal detachment, may follow. Vitrectomy is the treatment of choice for vitreous hemorrhage to restore vision.
Hypertensive retinopathy
Treatment for hypertensive retinopathy includes control of blood pressure with appropriate drugs, diet, and exercise.
Special considerations
❑ Arrange for immediate ophthalmologic evaluation when a patient complains of sudden, unilateral loss of vision. Blindness may be permanent if treatment is delayed.
❑ Be sure to monitor a patient’s blood pressure if he complains of occipital headache and blurred vision.
❑ Administer acetazolamide I.V. During inhalation therapy, monitor vital signs carefully. Discontinue therapy if blood pressure fluctuates or if patient develops arrhythmias or disorientation.
❑ Encourage a patient with diabetes to comply with the prescribed regimen.
❑ For a patient with hypertensive retino-pathy, stress the importance of complying with antihypertensive therapy.
Pictures
Book Source Details
- Book Title: Handbook of Diseases
- Author(s): Springhouse
- Year of Publication: 2003
- Copyright Details: Handbook of Diseases, Copyright © 2003 Lippincott Williams & Wilkins.
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More About This Book:
Title: Handbook of Diseases
Authors: Springhouse
Publisher: Lippincott Williams & Wilkins
Copyright: 2003
ISBN: 1-58255-266-5
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