Although a rare condition, ocular ischemic syndrome (OIS) indicates severe arteriosclerotic damage to the carotid artery and, often, significant systemic disease. Because the findings for OIS sometimes mimic those of other diseases, the practitioner should be vigilant in making a differential diagnosis.
The ophthalmic practitioner needs to keep carotid artery disease as a differential diagnosis in the back of his or her mind, said Loren Bennett, OD, MPH, FAAO, of the James H. Quillen Veterans Affairs Medical Center in Mountain Home, Tenn. Practitioners should consider it as a possibility when they see something that may be a little atypical of what they expect for diabetic retinopathy, for example.
Dr. Bennett said although recognizing OIS may be difficult, it is crucial that the practitioner make this subtle distinction. The ocular side effects can be devastating, because the patient can lose his or her vision, he said. But the systemic complications of underlying arteriosclerotic disease can be even more severe, in terms of cardiac damage and stroke.
Patients suffering from OIS are only rarely asymptomatic and often have a wide variety of ocular and systemic findings. The patient with OIS is often elderly, but can range in age from 50 to 80. The incidence of OIS in men is twice that in women.
According to Dr. Bennett, the patient very often manifests some sort of accompanying systemic condition. Generally, these patients will have co-existing systemic morbidities, such as diabetes, hypertension, peripheral vascular disease or cardiovascular disease, he said.
Joseph Sowka, OD, FAAO, an associate professor of optometry at Nova Southeastern University College of Optometry in Ft. Lauderdale, Fla., discussed some of the systemic findings associated with OIS.
In the vast majority of these patients, it comes from poor blood flow through the carotid artery, Dr. Sowka said. So there is atherosclerosis, as well as thrombosis formation within the carotid artery, which is almost always associated with hypertension.
Dr. Sowka added that in a small but significant number of patients, these systemic findings do not point to carotid artery disease or hypertension, but another condition called giant cell arteritis.
With this disease, inflammation of the walls of the carotid artery leads to closure, he said. And the devastating thing about this condition is that it is a multi-system disease and will quickly take the vision in the other eye from ischemic neuropathy or artery occlusion if it is not diagnosed properly.
Dot and blot hemorrhages: Mid-peripheral dot and blot hemorrhages and non-tortuous veins are a common finding in patients with OIS.
Anterior segment ischemia: The clinician may pick up anterior segment signs such as mid-dilated pupil, vascular congestion and rubeosis even before looking at the back of the eye.
Hypoperfusion retinopathy: This condition will be indicated by mid-peripheral dot and blot hemorrhages.
Venous irregularity can also occur in patients with OIS.
Digital subtraction angiogram: This angiogram shows 100% right carotid occlusion and critical stenosis of the left carotid in an OIS patient.
According to Dr. Sowka, some important signs of OIS include red eye; vision loss; unusual, atypical or asymmetric cataracts; unexplained anterior segment reaction; and ocular hypotony. And if you get to the back of the eye, you will see dilated but not tortuous retinal veins and mid-peripheral dot and blot hemorrhages, he said.
Maynard L. Pohl, OD, FAAO, clinical director of Pacific Cataract and Laser Institute, Bellevue, Wash., said the most significant symptoms of OIS are visual. Gradual loss of vision over several weeks occurs in up to 90% of patients, accompanied by dull eye or periorbital pain in approximately 50% of the patients, he said. Approximately 80% of cases are unilateral. Patients may report amaurosis fugax a transient monocular loss of vision due to thrombosis at the level of the central retinal artery.
According to Dr. Pohl, this phenomenon is described as a more gradual contracture of the visual field (tunnel vision) rather than a more sudden curtain-like phenomenon (associated with embolism.)
In addition, generalized ischemia is sometimes characterized by a condition called light-induced amaurosis, he said.
In some cases, the recovery of vision following exposure to bright lights is slow due to hypoxia interfering with the regeneration of visual pigment, Dr. Bennett said. So, patients may complain that it takes a while to recover from bright light.
Dr. Bennett discussed the manifestation of hypoperfusion retinopathy. It will show up as dot and blot hemorrhages in the mid-periphery, as well as in some cases cotton-wool spots or neovascularization either on the retina or on the disc.
Anterior segment ischemic signs include a low-grade uveitis or a sluggish, minimally reactive pupil, Dr. Bennett said. Scleral congestion presenting as red eyes is also a potential sign.
Dr. Sowka added that OIS can usually be recognized before looking at the back of the eye. You will see uveitis, particularly in an older person, ocular hypotony, corneal edema and asymmetric cataract, he said. There are many anterior segment signs that you will pick up before you even look in the back of the eye.
OIS sufferers generally experience severe vision loss and pain in the eye, called ocular angina, said Dr. Bennett. Ocular angina is caused by generalized ischemia of the eye. Other findings that may be associated with OIS are unilateral cataract, macular edema, and elevated intraocular pressure if neovascularization of the iris and angle with neovascular glaucoma develops.
Dr. Sowka said it is important for the practitioner to weave all of these symptoms together into a diagnosis. If a doctor looks at only one aspect of the condition, it could easily be missed, he said. Really, it is a combination of things. It is poor blood flow to the eye, and anterior chamber reaction, cataract, uveitis, or neovascularization.
But, typically, Dr. Sowka said, OIS is characterized by painful vision loss, and the patient is usually an older person. The mortality rate is actually quite high, he said.
The differential diagnosis
Diagnosing OIS can be a potentially difficult and confusing endeavor, according to Dr. Pohl. A thorough understanding of the patients medical and ocular history is imperative to making the diagnosis, he said. The ocular findings must be sequelae of underlying systemic vascular disease.
Dr. Pohl explained that the definitive diagnosis can be made when the subjective findings of the nature of vision loss are associated with clinical findings. The results of a medical consultation for complete cardiovascular evaluation, including carotid duplex scanning, aid in establishing the definitive diagnosis of ocular ischemic syndrome, Dr. Pohl said. Typically, carotid studies reveal greater than 90% obstruction of the ipsilateral, internal or common carotid artery.
According to Dr. Pohl, the differential diagnosis often requires the practitioner to distinguish OIS from central retinal vein occlusion (CRVO) and diabetic retinopathy. The presence of optociliary shunt vessels, presence of disc edema, no report of decreased vision after bright light exposure and absence of orbital and periorbital pain help differentiate CRVO from ocular ischemic syndrome, he said.
Bilaterality and often symmetry, posterior pole confinement and the presence of lipid exudates help differentiate diabetic retinopathy from OIS, Dr. Pohl said. However, keep in mind that ocular ischemic syndrome may be preceded by either or both of these retinal conditions, he added.
Treatment of OIS
According to Dr. Sowka, treatment for OIS is not well delineated. If a patient develops neovascularization of the anterior segment, the treatment for that is generally panretinal photocoagulation, he said. Unfortunately, the response is much poorer for OIS than diabetes, for example.
Establishing the causative factor for OIS is a major component of treatment, according to Dr. Bennett. The primary treatment is to try to get at the underlying cause, which is mainly carotid occlusive disease, he said. So, the underlying carotid occlusive disease would need to be treated, either through anti-coagulants or anti-platelet therapy, possibly carotid endarterectomy surgery.
Dr. Sowka said carotid endarterectomy surgery is one of the most viable options in treating OIS. The surgeon actually goes in and removes the ulcerated carotid plaque, he said. It is the more definitive option. However, approximately 30% of the patients will improve, and a third will stay the same. A third will worsen.
Dr. Pohl said carotid endarterectomy should be considered in cases of significant carotid obstruction. Based on current clinical research, carotid endarterectomy by a skilled vascular surgeon should be considered in cases of 60% or greater carotid obstruction, he said.
Because OIS generally signals severe systemic problems, practitioners are advised to carefully assess both ocular and systemic findings when making a differential diagnosis.
It is important for the practitioner to remember that the systemic complications of atherosclerotic disease can be quite severe, Dr. Bennett said. Cardiovascular abnormalities may be involved as well. So practitioners are going to need to look not just at carotid duplex in their work-up of the patient, but cardiovascular risk factors as well.
Dr. Pohl added that the careful monitoring of systemic findings of OIS also presents an excellent opportunity for comanagement.
Direction to the attention of the underlying systemic vascular conditions is imperative, he said, and arranging for such patients to follow up closely with their internist represents a wonderful interprofessional comanagement opportunity for primary care optometrists.
For Your Information:
- Loren Bennett, OD, MPH, FAAO, is a practitioner at the James H. Quillen Veterans Affairs Medical Center. He can be reached at Eye Clinic 112E, Mountain Home, TN 37684; (423) 926-1171, ext. 7283; fax: (423) 979-3530.
- Joseph Sowka, OD, FAAO, is an associate professor of optometry at Nova Southeastern University in Fort Lauderdale, Fla. He can be reached at 3200 S. University Dr., Ft. Lauderdale, FL 33328; (954) 262-1472; fax: (954) 262-1818.
- Maynard L. Pohl, OD, FAAO, is clinical director of the Pacific Cataract and Laser Institute in Bellevue, Wash. He can be reached at 10500 NE 8th St., Suite 1650, Bellevue, WA 98004; (425) 462-7664; fax:(425) 462-6429.