Simvastatin increases retinal blood flow and decreases intraocular pressure in healthy subjects, making it a potential treatment for diabetic retinopathy and glaucoma, according to Dr. Taiji Nagaoka of Asahikawa (Japan) Medical College and associates.
Noting that long-term statin use has been reported to reduce the risk of retinal ischemic diseases, the researchers assessed the effect of simvastatin on the retinal circulation and on intraocular pressure in 12 healthy volunteers.
The subjects were nonsmoking Japanese men aged 19–23 years. They were examined 90 minutes after a single 20-mg dose of the drug on one occasion and after taking a placebo on a separate occasion. They also underwent similar assessments after taking daily doses of either simvastatin or placebo for 1 week.
Retinal blood flow increased significantly, by 20% in the retinal arteries and by 23% in the retinal veins, after 1 week of simvastatin therapy. Intraocular pressure decreased significantly, from 14.3 mm Hg at baseline to 12.6 mm Hg after a single dose of the drug and to 12.4 mm Hg after 1 week of therapy. Plasma nitrite/nitrate levels also rose by 60% after 1 week on simvastatin.
In contrast, all retinal measurements remained unchanged after administration of the placebo.
This is the first study to show that simvastatin increases retinal blood flow, “probably via the increase in nitric oxide,” the investigators said (Arch. Ophthalmol. 2006;124:665–70).
The increase appears to be exerted mainly on the more downstream vessels in the retinal microvascular network, notably the capillaries, they added.
A previous study involving six subjects suggested that statins might improve hard exudates and microaneurysms in diabetic retinopathy. “Although the findings in the present study are obtained from healthy men whose physiological response to simvastatin may be different from that of patients with diabetes, the increased retinal blood flow associated with treatment with simvastatin may be a potential therapy for diabetic retinopathy,” Dr. Nagaoka and associates said.
Similarly, another study recently reported that statin use appears to reduce the risk for glaucoma but did not measure intraocular pressure. “In the present study, we document for the first time … that the intraocular pressure was slightly but significantly decreased by simvastatin,” they added.
“Further study among more subjects is needed to examine the effects of age, sex, and systemic disorders such as hyperlipidemia, hypertension, and diabetes mellitus, on the retinal circulation that are associated with systemic administration of simvastatin,” they said.