carotid connection, The

Optometric Management, Feb 2000 by Schmidt, Eric

Unmasking oscular ischemic syndrome.

Many ocular conditions can mimic more common diseases. Some mimickers can have sight- or lifethreatening consequences. Conduct a differential diagnosis process like the one here to rule out serious conditions.

THE CASE: Fred was a 76-year-- old gentleman with a grandfatherly disposition. His internist referred him to me because of persistent pain centered around his left eye.

Fred said that the pain had been constant for almost a year and that at times it became severe. Pain relievers did nothing to alleviate it, but putting pressure on the eyeball or bone around it helped. Fred said he saw well but occasionally noticed a shadow "shimmer" before his eyes. In the referral note, the internist said that the pain might be caused by trigeminal neuralgia, but he wanted me to rule out glaucoma before embarking on more aggressive treatment.

Fred was taking isosorbide dinitrate 20 mg (Isordil) for hypertension and diltiazem hydrochloride 60 mg (Cardizem) for his heart. He was also using pseudoephedrine for his sinuses.

Though Fred was very jovial, he seemed frail. He walked with a very unsteady gait. His wife told me that he'd never had a stroke, but that his heart problem was worsening.

Fred's exam

I measured Fred's visual acuity (VA) as 20/20 OD, 20/25 OS with his spectacles. His extraocular muscles showed no restrictions, and he denied pain on movement. Pupils were 4 mm on both sides and reactive to light; I saw no afferent pupillary defect. Fred's anterior segments were normal OU. The anterior chambers (AC) were narrow but open, and I saw no cell or flare. There was no iris transillumination or posterior synechiae.

Fred did have a mild posterior subcapsular cataract OS. His intraocular pressures (IOP) were 17 mm. Hg OD and 24 mm Hg OS. Because of the pain, the asymmetry of IOP and the appearance of the AC, I felt that a gonioscopic exam was warranted. This revealed narrow but open angles OU. I graded the right angle as Grade 2, 360 degrees and the left as grade 1 temporally with grade 2 angles for the remaining 270 degrees. I saw, importantly, that both angles were free of synechiae, iris processes and neovascularization.

The second clue

When I examined Fred's retinas, I detected six blot hemorrhages in the mid-periphery OS (see photo, page 98). I also saw a small cotton wool spot in the superior arcade OS. No neovascularization was present. The disks weren't elevated or pale. The retinal appearance was consistent with ischemia, but I wanted to rule out temporal arteritis. I ordered an erythrocyte sedimentation rate, which came back normal (14 mm/hr). Now I could diagnose ocular ischemic syndrome (OIS). I called Fred's internist and suggested a prompt carotid scan or arteriography.

The arteriogram showed 70% blockage of the right carotid artery and 90% blockage of the left. Six days later, Fred underwent a carotid endarterectomy on his left side.

Signs along the way

OIS results from prolonged hypoperfusion of the ocular structures due to severe carotid artery occlusion.The blockage is usually greater than 90%.

Signs and symptoms of OIS can vary widely, depending on the severity of the ischemia. Ocular pain and decreased vision are characteristic. The pain, or "ocular angina," comes from ischemia rather than the elevated IOP. The vision loss may range from 20/40 to NLP and is usually progressive over weeks. Mild corneal edema is common, and a uveitis may occur, especially with rubeosis iridis. IOP is usually increased on the affected side.

Here are other pointers:

The retinal picture. This is consistent with hypoperfusion retinopathy. Dot and blot hemorrhages and microaneurysms exist in 80% of cases. They're usually asymmetric or unilateral and are found in the mid-periphery.

Retinal veins. Retinal veins are dilated but not tortuous; the retinal arterioles are attenuated.

Neovascularization. Rubeosis, a key to diagnosis, is present in two-thirds of OIS patients. Thirty-five percent develop neovascular glaucoma, characterized by neovascularization of the angle. Neovascularization of the disk and neovascularization elsewhere, though less common, are also visible.

Poor prognosis. For reasons that are unclear, only 5% of patients with severe carotid stenosis develop OIS. Other vascular conditions, such as diabetes mellitus, hypertension or stroke, often accompany OIS.

OIS patients have a poor visual prognosis. Within a year, 60% progress to count-fingers vision, even with optimal medical treatment. If rubeosis is present, 97% lose this much vision after 1 year. But most important OIS patients are at risk for death from myocardial infarction or stroke. One study showed that 40% will die after 5 years, and 5% will suffer a stroke in any given year. Clearly, the earlier the diagnosis is made, the better. Counsel your patients to take the situation seriously and advise them of the potential for vision loss or even death.

How to treat

Panretinal photocoagulation is indicated for OIS, especially in cases with neovascularization. It won't improve vision, but will alleviate pain and other symptoms by decreasing the ischemia.