Arcus Senilis - What does it mean?

Motivation: A few years ago, before I entered medical school, I was volunteering at an inner-city health clinic for the homeless and thought that everyone over fifty was developing cataracts.  So many people had this white ring around their iris.  Since then, I have been disillusioned and learnt about arcus senilis.  Last month, however, arcus senilis again came to my attention.  A resident and I were evaluating a patient in ED with suspicious chest pain, and the resident talked about how the arcus in the context of the patient's history suggested underlying vascular disease.  So, I wondered, how predictive is arcus for atherosclerosis?

As introduction, corneal arcus is a lipid-rich deposit at the junction of the cornea and sclera.  The corneal arcus lipid deposition is thought to share some similarity with lipid deposition in atherosclerosis.

Paper: Relation of Corneal Arcus to Cardiovascular Disease (from the Framingham Heart Study Data Set).  Fernandez, A. B., et. al. The American Journal of Cardiology 2008 (103): 64-66.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2636700/?tool=pubmed

Method: The Framingham study is a prospective study initiated in 1948 to study factors influencing incidence of cardiovascular disease (CVD).  Based on initial evaluation of arcus, the paper determined the predictive value of arcus for CVD after four and eight years.  The total cohort examined in the paper consisted of 23,376 patients for four year prediction study and 13,469 for eight year study.

Results: 


Unadjusted: Just the presence of arcus was predictive of first cardiovascular event with a hazard ratio of 2.28 (2.02-2.57) at 4 years and 2.52 (2.15-2.95) at 8 years.

Age and gender adjusted: Since increased age and male gender correlate with CVD, the authors adjusted for age and gender.  After adjustment, arcus was predictive of events with hazard ratio of 1.07 (0.95-1.22) at 4 years and 1.18 (0.99-1.39) at 8 years.

Multivariate adjustment: Of course, there are more known factors influencing CVD than just age and gender.  The authors also modeled the data after adjusting for age, gender, cholesterol, blood pressure, diabetes, smoking, and BMI.  With multivariable adjustment, arcus was predictive of events with hazard ration of 1.04 (0.92-1.18) at four years and 1.14 (0.96-1.35) at eight years.

Conclusion: After adjusting for age and gender, arcus lost independent predictive value for CVD.  The most likely explanation for the unadjusted association of arcus with CVD is that older people are more likely to have both arcus and vascular disease.  This was the largest study examining the association of arcus with CVD.

Other studies in the past have linked arcus as an independent predictor of CVD.  A major difference in the Framingham study is that detailed ophthalmological exams were not done, and arcus was assigned by visual inspection.  So, while detailed examination of arcus may have some underlying predictive value, just visually finding arcus is not more predictive of CVD than just age and gender!