Ocular Ischaemic Syndrome

http://emedicine.medscape.com/article/1201678-overview

Background

Ocular ischemic syndrome (OIS) encompasses the ocular signs and symptoms that result from chronic vascular insufficiency. Common anterior segment findings include advanced cataract, anterior segment inflammation, and iris neovascularization. Posterior segment signs include narrowed retinal arteries, dilated but nontortuous retinal veins, midperipheral dot-and-blot retinal hemorrhages, cotton-wool spots, and optic nerve/retinal neovascularization. The presenting symptoms include ocular pain and abrupt or gradual visual loss.

Pathophysiology

The most common etiology of OIS is severe unilateral or bilateral atherosclerotic disease of the internal carotid artery or marked stenosis at the bifurcation of the common carotid artery. OIS may also be caused by giant cell arteritis. It is postulated that the decreased vascular perfusion results in tissue hypoxia and increased ocular ischemia, leading to neovascularization.

Frequency

United States

It is estimated that approximately 5% of patients with marked carotid artery stenosis present with OIS.

Mortality/Morbidity

The 5-year mortality rate in patients with OIS is about 40%. The leading cause of death is cardiac disease, followed by stroke and cancer. Predisposing risk factors for atherosclerosis (eg, hypertension, diabetes mellitus) have a higher prevalence in patients with OIS than in age-matched populations.

Sex

Males are affected more frequently than females, by a ratio of approximately 2:1.

Age

OIS mainly affects elderly patients. The age range is 50-80 years, with a mean age range of 65-68 years. OIS is uncommon in patients younger than 50 years.

History

Symptoms can include amaurosis fugax, gradual or sudden visual loss, and pain. The diagnosis of OIS should always be suspected in elderly patients with asymmetric anterior uveitis, hypotony, neovascularization cataract, and retinopathy.

• Loss of vision
  • Loss of visual acuity is the most frequently encountered symptom, present in 70-90% of patients at the time of presentation. Only a minority of patients (<10%)>
  • Patients with OIS can present with variable degrees of visual loss. Up to two thirds of patients can present with visual acuities of 20/60 or worse. One third of patients will have visual acuities of counting fingers or worse. Although, in most cases, visual loss occurs gradually over a period of weeks to months, in some cases, it can also occur abruptly.
• Pain: About 40% of patients with OIS will present with symptoms of pain. The pain is characteristically described as a dull ache over the brow, which begins gradually over a period of hours to days.
• Amaurosis fugax: Amaurosis fugax is a transient episode of complete or partial monocular blindness, lasting for a period of less than 10 minutes. A history of amaurosis fugax is elicited in 9-15% of patients with OIS.

Physical

• Cardiovascular examination
  • Arm pulses
  • Cardiac auscultation
  • Carotid auscultation
• Ophthalmic examination
  • Anterior segment^1,3
    • Corneal abnormalities: Descemet folds and corneal edema may be present secondary to ocular hypotony or increased intraocular pressure.
    • Iris neovascularization: Iris neovascularization is encountered in 67-87% of affected eyes.
    • Neovascular glaucoma: This is elevated intraocular pressure in the presence of angle neovascularization. Neovascular glaucoma is seen in about one third of patients with OIS. Lower arterial perfusion to the ciliary body may induce hypotony or normal intraocular pressure despite significant anterior chamber angle neovascularization.
    • Anterior chamber inflammation: Uveitis, characterized by the presence of cells and flare in the anterior chamber, was estimated to occur in up to 20% of eyes. In most cases, the inflammatory reaction is only mild.
    • Cataract: Advanced degrees of lens opacities may be seen in patients with OIS.
  • Posterior segment
    • Retinal vessels: Retinal arteries are typically narrow in eyes with OIS. The veins are usually irregularly dilated but not tortuous.
    • Retinal hemorrhages: Midperipheral dot-and-blot retinal hemorrhages are observed in 24-80% of eyes with OIS. Microaneurysms can also be seen.
    • Cotton-wool spots: These are seen in approximately 5% of eyes with OIS and are typically located in the posterior pole.
    • Neovascularization: Neovascularization of the optic nerve is seen in 13-35% of eyes with OIS. Retinal neovascularization is less common, and occurs in 3-8% of cases. Neovascularization of the optic nerve can be mild, or it can progress into extensive fibrous proliferation, causing secondary vitreous hemorrhage and tractional retinal detachment.
    • Cherry-red spot: The cherry-red spot appears as a result of ischemia involving the inner layers of the retina, as typically seen in cases of central retinal artery occlusion. It is noted in 12% of eyes with OIS.
    • Optic disc: Optic disc pallor, cupping, or edema is also noted in patients with OIS.
  • Orbit: Ocular ischemia can be part of a rare orbital compartment syndrome that occurs after prolonged spinal surgery in the prone position and was first described by Hollenhorst more than 50 years ago.These patients can present with significant proptosis, ophthalmoplegia, eyelid swelling, and ocular ischemia. The exact mechanism is not known, but it is hypothesized that the tamponade action from pressure of the ocular content causes partial or complete collapse of the orbital arterial and venous channels. When the external pressure is released, the ischemic vessels dilate and fluid transudates into the tissue spaces, causing orbital edema.

Causes

• High-grade carotid stenosis: Stenosis of the carotid artery results in concomitant chronic ophthalmic artery insufficiency. Abnormalities of both anterior and posterior segments of the globe are a result of reduced oxygen delivery to the eye.
• Vascular occlusive disease includes occlusive disease of the aortic arch, ophthalmic artery, central retinal artery, and ciliary arteries.