The eye is proverbially the window to the soul, and literally a window into the vascular system. Evaluation of the retinal vasculature gives insight into multiple systemic diseases affecting the patient. Simply by evaluating the retina, one can determine diseases such as severe hypertension, diabetes mellitus, embolic disease, lupus, infection, and extended abdominal trauma.

The eye is fed by the first branch of the internal carotid artery. This ophthalmic artery then branches off into the central retinal artery, the posterior ciliary arteries, and the muscular branches. The venous system is comprised of the posterior vortex veins, which drain into the superior and inferior orbital veins which then drain into the cavernous sinus; and the central retinal vein, which drains the retina and the optic nerve directly into the cavernous sinus.¹

Systemic hypertension is diagnosed when the blood pressure is greater than 140 systolic and 90 diastolic measured on three separate occasions separated by at least 2 weeks. High blood pressure is extremely common to the industrialized countries. The ocular signs in hypertension are directly related to the rate and degree of systemic blood pressure. Atherosclerosis is a common finding in systemic hypertension. It can also occur in the normal aging population. The retinal changes seen in hypertension may overlap with those found in other retinal vascular diseases such as diabetes (Figure 22-1).²

Systemic hypertension is one of the most common diseases affecting patients throughout the world. The most common ocular manifestations include focal constriction and dilation of retinal arteries, narrowing and irregularity of the retinal arteries, AV nicking, blot retinal hemorrhages, microaneurysms, and cotton-wool spots. Several classification schemes have been used to stage hypertensive retinal changes. The most commonly accepted are the Keith-Wagener-Barker classification (Table 22-1) and the Scheie classification (Table 22-2). With these classification systems, one is able to evaluate the degree of hypertension systemically and begin therapy.

The treatment of hypertensive retinopathy consists of blood pressure control. No specific ocular therapy exists to reverse the changes. In case of accelerated hypertension or malignant hypertension, systemic diseases must be ruled out such as renal disease, polycystic kidney, renal stenosis, pheochromocytoma, and pregnancy.⁴

Retinal artery obstructions are divided into two main types: central and branch, depending on the location of the obstruction. Central retinal artery occlusion is an acute stoppage of blood flow through the central retinal artery, leading to ischemia and nonperfusion of the retina. This is an abrupt, painless, severe loss of vision heralded by a cherry-red spot in the macula area. The peripheral retina becomes ischemic and white. The macula remains red secondary to choroidal blood flow. This is commonly referred to as an amaurosis fugax and is a term used to describe the situation with a painless loss of vision occurring. Emboli are seen only approximately 25% of the time. It is an indicator of carotid vascular disease approximately one-third of the time as opposed to giant cell arteritis, which is only found 5% of the time. Branch retinal artery occlusions have a similar presentation commonly associated with carotid vascular disease, cardiac valvular disease, or systemic clotting (Figure 22-3).⁵

Central retinal artery obstruction is rare. It is estimated to be seen in one patient out of 10 000 who visits to an ophthalmologist. Men are more common than women at a ratio of 2:1 with the onset being around 60 years of age. The majority of central retinal artery obstructions are caused by thrombus formation just proximal to the lamina cribrosa and are therefore not seen on ophthalmic examination. Atherosclerosis is the cause in most cases, although congenital anomalies of the central retinal artery, systemic coagulopathies, or low blood flow states may also be seen. In only 25% of the cases, an emboli is visible in the central retinal artery or one of its branches, suggesting that an embolic cause is not very common. Other diseases besides emboli that can lead to central retinal or branch retinal artery occlusion include shingles, optic neuritis, or mucormycosis. Systemic coagulopathies may be associated with both central and branch retinal artery obstructions. Other causes of obstructive retinopathy include radiation retinopathy, emboli associated with depot medication, injections such as steroids around the eye, and IV drug use.⁶

The hallmark of ocular manifestation of acute central retinal artery obstruction is an abrupt, painless loss of vision. Pain is unusual and if found is associated with ocular ischemic syndrome. Amaurosis fugax is seen in approximately 10% of the patients.

In rare situations, a patient may have a patent cilioretinal artery which perfuses the fovea and the patient may have normal central vision. The ophthalmic manifestation on clinical examination, the hallmark is a cherry-red spot of the macula, will not be seen in a patient with a ciliary retinal artery.

When a central retinal branch artery occlusion is found, systemic disease associated includes 60% of the time systemic hypertension, 25% of the time diabetes, and 50% of the cases have no definitive cause for the obstruction. Potential embolic sources are found less than 40% of the time in any type of arterial occlusion.

The most common association is significant ipsilateral carotid artery disease, which is present in approximately one-third of the patients. An embolic source from the heart is present in less than 10% of the cases. Other rare systemic diseases include blood-clotting abnormalities such as antiphospholipid antibodies, protein S deficiency, protein C deficiency, and antithrombin III deficiency.⁷

Common systemic conditions associated with central retinal artery obstruction include atherosclerotic cardiovascular disease such as carotid plaques or dissection, aortic plaques or dissection, cardiac disease such as valvular rheumatic fever, VSD (ventriculoseptal defects), cardiac myxoma, mural thrombus, and subacute bacterial endocarditis. Cancers including metastatic tumors, leukemia, and lymphoma have also been associated with vascular obstructive diseases.

Medical procedures such as angiography, angioplasty, chiropractic neck manipulation, and cortical steroid injections around the eye have also been found to lead to vascular obstructive diseases. Systemic vasculitides such as temporal arteritis, Wegener’s granulomatosis, inflammatory bowel disease, Kawasaki syndrome, systemic lupus, and polyarteritis nodosa have also been associated with retinal artery obstruction. Systemic infections such as syphilis—the great masquerader—have also been found associated with this syndrome.

Miscellaneous other diseases leading to vascular obstruction include amniotic fluid emboli, IV drug use, cocaine abuse, oral contraception, pregnancy, and migraines.

Venous obstruction of the retina is a relatively common finding second only to diabetes, more commonly affecting patients 50 years of age or older. Retinal vein obstructions are classified as whether they are central or branch. Although classified commonly together, they have significant differences leading to various outcomes for the eye. Specifically, ischemic venous obstructive diseases can lead to neovascular glaucoma of the eye and eventual blindness.⁸

Central retinal vein occlusion is 90% of the time in patients 50 years of age or older, more common in men than women. It is often associated with diabetes, hypertension, and atherosclerotic disease. Sedimentation rate elevation appears to be a risk factor in women only. Open-angle glaucoma is a relatively common finding in patients who have had a central retinal vein occlusion. Patients with a history of glaucoma are five times more likely to have a central retinal vein occlusion than those who do not. An acute angle-closure glaucoma may precipitate a central retinal vein occlusion.⁹

The exact pathogenesis of a central retinal vein occlusion seems to involve a thrombus at the central retinal vein near the lamina cribrosa, and why this occurs is unknown. Clinical findings include retinal hemorrhaging; dilated, tortuous veins in affected quadrants; disk edema; macular edema; and cotton-wool spots.

Central retinal vein occlusions can be broken down into nonischemic versus ischemic. Both involve hemorrhages throughout the retina in all four quadrants. However, with the ischemic version, approximately two-thirds of the patients go on to develop anterior segment neovascularization usually within 3 months, which then leads to neovascular glaucoma. Workup for venous occlusions would include a complete eye examination, blood pressure, complete blood count, partial thromboplastin time, antinuclear antibody, protein electrophoresis, and sedimentation rate.¹⁰