Methods

Patient charts that indicated a diagnosis of “retinal artery occlusion” from January 1, 1976, through December 31, 2005, were selected and reviewed using the Rochester Epidemiology Project. The Rochester Epidemiology Project is a medical records linkage system established to study the epidemiology of disease for residents of Olmsted County in southeastern Minnesota. It links and indexes diagnostic and procedure information from the Mayo Clinic in Rochester, Minnesota and other facilities that provide health care to residents in this community (Olmsted Community Hospital, Olmsted Medical Group, the University of Minnesota, and Department of Veterans Affairs hospitals in Minneapolis).

Records were identified through the Rochester Epidemiology Project based on the hospital adaptation of the International Classification of Diseases and International Classification of Diseases-9 codes for retinal embolism, retinal infarction, Hollenhorst plaque, retinal ischemia, retinal artery occlusion, retinal artery obstruction, artery eye occlusion, retinal vascular occlusion, unspecified retinal ischemia, partial retinal arterial occlusion, retinal arterial branch occlusion, and transient retinal arterial occlusion. Patients were eligible for inclusion in this study if their record indicated a clinical history of abrupt vision loss and fundus findings of retinal opacification or a cherry red spot or both. Cases were excluded if there was a recent invasive or surgical procedure (including ocular surgery) known to precipitate a CRAO. Also excluded were cases with an ocular condition that prevented a view of the fundus.

Yearly incidence rates for each age and sex group were determined by dividing the number of cases within each group by the estimated total Olmsted County resident population for that year. Population figures for 1990 and 2000 came from the US Census, and populations for the inter-census years were estimated using linear interpolation. Estimates from the State of Minnesota Demographer’s Office were used to aid with linear interpolation between census years. Incidence rates were also age- and sex-adjusted to the 2000 census figures for the US white population. The 95% confidence intervals (CI) were calculated by assuming a Poisson distribution. Mortality was estimated using the Kaplan-Meier method.

The racial distribution of Olmsted County residents in 1990 was 95.7% white, 3.0% Asian American, 0.7% African American, and 0.3% each Native American and other. The population of this county (106 470 in 1990) is relatively isolated from other urban areas, and virtually all medical care is provided to residents by the Mayo Clinic or the Olmsted Medical Group and their affiliated hospitals. Residency of patients at the time of diagnosis was checked using information from city and county directories. Patients not living in Olmsted County at the time of their diagnosis were excluded.

Results

Between 1976 and 2005, out of 740 charts reviewed 43 cases of CRAO were identified using the inclusion and exclusion criteria; 26 subjects (60%) were male and 17 (40%) were female. The mean age at presentation was 74.3 years (range 46–90). Racial characteristics of the patients reflects Olmsted County’s population, with 93% white and 2% each Asian, African American, and Hispanic. Twenty-seven patients were afflicted in the right eye, 15 patients in the left eye, and 1 presented with bilateral disease. Patients presented on average within 4 days (0.04–30 days) of onset, and 32 (74%) presented within 1 or 2 days. Initial visual acuity was worse than 20/400 in 37 patients (86%). Vision ranged from no light perception (14%) to 20/25 (2%). The majority of patients (28, or 65%) had no prior ocular history. On initial examination, 14 patients (33%) had retinal arterial emboli and 4 (9%) had cilioretinal sparing. Cardiovascular risk factors included hypertension (88%), diabetes mellitus (21%), hyperlipidemia (40%), and smoking (16%). Twenty-four patients (56%) had multiple cardiovascular risk factors. On presentation, 27 patients (56%) were not on anticoagulation therapy. Examinations included transthoracic or transesophageal echocardiogram (TTE, TEE), carotid ultrasound, cerebral angiography or magnetic resonance angiography, and erythrocyte sedimentation rate (ESR). Twenty-six patients were examined by TTE or TEE. Valve disease was the most frequent abnormality found (10 patients). A thrombus was found in 1 patient. Vascular procedures including carotid ultrasound, cerebral angiography, or magnetic resonance angiography were performed 32 times among 26 patients. There was a significant vascular stenosis (> 50%) in 6 patients. Thirty-eight patients had a recorded ESR, with a median of 11 (range 0–86). An ESR of 86 was recorded in a patient with known rheumatoid arthritis who subsequently had a negative temporal artery biopsy. Of the 43 CRAO cases, 3 patients underwent surgical intervention for systemic abnormalities found during the examination for CRAO (1 each: bilateral carotid endarterectomy, pacemaker placement, superficial temporal artery to middle cerebral artery bypass). Multiple treatments for CRAO were attempted (ocular massage, 40%; glaucoma medications, 33%; paracentesis, 16%; anticoagulation, 14%; supraorbital artery cannulation with infusion of heparin, 14%; hyperbaric oxygen, 2%), although no treatment was superior to others. The average follow-up after diagnosis was 5 years (range 2 days – 22.5 years). Thirty-five patients were deceased at the conclusion of the study period. Causes of death included coronary events in 14 (33%), stroke in 5 (12%), and other causes in 15 (35%). One death was from an unknown cause. The unadjusted annual incidence of CRAO in Olmsted County for female and male populations was 1.02 and 1.67 per 100 000, respectively, and the combined incidence was 1.33 per 100 000. The age-adjusted annual incidence per 100 000 for the female population was 1.15 (95% CI, 0.60–1.71), for the male population was 2.78 (95% CI, 1.69–3.86), and combined was 1.87 (95% CI, 1.31–2.43). When adjusted for age and sex, the annual incidence was 1.90 per 100 000 (95% CI, 1.33–2.47).