Dublin, Ireland - Not only are high blood pressure and high cholesterol levels risk factors for cardiovascular disease, but they also appear to increase the risk of patients developing retinal vein occlusion, a common form of retinal vascular disease that causes vision loss, according to the results of a new meta-analysis [1].

Investigators showed that those with hypertension had a 3.5-fold greater risk of having retinal vein occlusion than normotensive subjects, while those with elevated cholesterol levels had a 2.5-fold greater risk. There was only a modest correlation between retinal vein occlusion and the presence of diabetes mellitus.

"Those who treat patients with systemic hypertension, diabetes mellitus, and hyperlipidemia should consider that each poses a risk not only to cardiovascular health but also to ocular health," write Dr Paul O'Mahoney (Royal College of Surgeons, Dublin, Ireland) and colleagues in the May 13, 2008 issue of the Journal of Ophthalmology.

The meta-analysis included 21 studies involving 2916 individuals with retinal vein occlusion and 28 646 control participants. The data were pooled to estimate population-attributable risk, or the percentage of retinal vein occlusion that could be attributed to hypertension, diabetes, and hyperlipidemia. As noted, investigators observed significantly higher rates of retinal vein occlusion among subjects with hypertension, hyperlipidemia, and diabetes mellitus, although there was only a modest correlation between the latter risk factor and retinal vein occlusion.

In terms of the population-attributable risk, nearly 50% of disease was attributed to hypertension, 20% to high cholesterol levels, and 5% to diabetes mellitus. If causal, write the authors, this would mean that treatment of these diseases might be important in the primary and secondary prevention of retinal vein occlusion, in addition to the prevention of heart disease and stroke.

"Accordingly, we recommend that an assessment of blood pressure and both fasting lipid and glucose levels be routinely performed in adults with any form of retinal vein occlusion," writes O'Mahoney and colleagues.

The investigators point out, however, that the study has limitations, notably that the definitions of hypertension, diabetes mellitus, and hyperlipidemia varied within and among studies, which was partly due to the changing diagnostic criteria for each condition during the 20 years of study. In most studies, the severity of hypertension and hyperlipidemia were not reported.

O'Mahoney and colleagues write that data are needed to determine whether excessive lowering of blood pressure in persons with retinal vascular disease might have negative effects during the acute phase of the disease and whether or not it can reduce the long-term risk of glaucoma or retinal vein occlusion recurrence.

Studies are under way to determine any potential benefits of lowering LDL- and total-cholesterol levels in subjects with retinal vein occlusion, such as the Atorvastatin Toronto Retinal Vein Occlusion (ATORVO) study, a randomized, double-blind clinical trial comparing 80 mg of atorvastatin with placebo in 180 persons with retinal vein occlusion. Changes in visual acuity and the presence of secondary complications will be evaluated 24 weeks after randomization. In 2006, heartwire reported the results from a small pilot study showing that statins might be used to treat retinal ischemic disease, with Japanese investigators reporting that treatment with simvastatin increased blood-flow velocity in the retinal arteries and veins and decreased intraocular pressure [2].