Of the clinical and procedural variables analyzed in our sample of 300 patients who underwent diagnostic or therapeutic catheterization, 2 conventional risk factors (age and hypertension) and operator expertise were strongly associated with the appearance of new retinal emboli. Other conventional and procedural risk factors showed no significant relation with the appearance of this lesion. At the start of the study, we hypothesized a strong association between the severity of coronary artery disease and the risk of retinal embolization. We reasoned that more severe coronary artery disease would be related with more atherosclerosis of the aorta, which in turn would make patients more susceptible to retinal emboli. As noted by Segal and colleagues, plaque broken off from the ascending aorta or the aortic arch can be the main source of systemic emboli including retinal lesions . It appears likely that the risk of vascular plaque mobilization increases with aging and hypertension.
Klein et al.  found that the prevalence of baseline retinal emboli was associated with higher pulse pressure, hypertension, cardiovascular disease, diabetes mellitus and past and current smoking. The prevalence of baseline retinal emboli in their patients was 1.3%. Our study identified some of the same risk factors, including age and hypertension, as playing a role in post-procedure retinal emboli. A prospective cohort study by Thyer et al.  found a prevalence of baseline retinal emboli of 5%, but obtained no evidence suggesting that coronary catheterization contributes to retinal embolism shortly after the procedure. Funduscopic examination detected no new retinal emboli in 97 patients who underwent coronary catheterization. The differences between their findings and ours may have arisen, in part, because Thyer and colleagues included patients with a normal angiogram in their sample of patients who underwent coronary catheterization, and their sample was too small to reveal significant differences.
Kreis et al.  found a 2% incidence of acute retinal embolism after coronary catheterization, and indicated that the retinal and possibly cerebral circulation may be more severely compromised more frequently than is clinically apparent. In their study the main method of retinal examination was digital retinal photography. New retinal emboli after cardiac catheterization were seen in 6.3% of our patients. The reason for our higher figure compared to the incidence found by Kreis and colleagues may be that routine retinal photography is not sensitive enough to detect tiny retinal emboli that cause partial, peripheral arteriolar obstruction.
Busing et al.  found that diagnostic and interventional cardiac catheterization increased the risk of silent cerebral infarction to 15%. Their sample of 48 patients was not large enough to analyze risk factors, and they noted that the statistical analysis of their results was weak, so they could not evaluate potential risk factors in detail.
Our figures for the incidence of retinal emboli after coronary catheterization are based on the findings of retinal examination by a retinal specialist. Nineteen patients developed retinal emboli, only one of which was clinically apparent. With regard to the rate of emboli formation and their clinical significance, cardiac catheterization can be considered a safe procedure. In our patients, all lesions were located in non-eloquent areas of the retina (one was found in the main branch of the central retinal artery) and were too small to be clinically apparent. However, when lesions affect more important areas of the retina, such as the central retinal artery, they can have severe clinical consequences. Cardiologists who perform coronary catheterization should be cognizant of the clinical symptoms and signs of large retinal emboli (i.e., any visual complaint, especially a decrease in visual field or acuity), because they can have a devastating effect on the retina. Because coronary catheterization may contribute to retinal artery occlusion, prompt consultation with an ophthalmologist should be considered if symptoms suggestive of visual disturbance appear during or soon after coronary catheterization.
The rate of retinal embolization appeared to be slightly higher after therapeutic cardiac catheterization than after diagnostic angiography; however, this difference was not statistically significant. We suspect that further manipulation of the aortic root might increase the risk of embolism, and further research will be needed to test this hypothesis. Retinal emboli occurring after cardiac catheterization warrant a careful vascular workup including a search for the emboli in the aortic arch, the great vessels and the chambers of the heart itself. Vascular ultrasound, transesophageal echocardiography and (potentially) computed tomographic angiography or magnetic resonance angiography can be extremely useful in this regard. These techniques, unfortunately, were not available at our center when we studied this cohort.