Eye Drops That Lower Cholesterol, Fight Age-Related Blindness

In a study which can have far reaching consequences, scientists from the Washington University School of Medicine in St. Louis have found that drugs commonly employed to lower the levels of cholesterol can be effectively used to treat macular degeneration, an age related blindness. The research has been published in the journal Cell Metabolism and was led by Rajendra S. Apte, a Paul A. Cibis Distinguished Professor of Ophthalmology and Visual Sciences, along with his colleagues.

Macular degeneration is one of the commonest causes of blindness in American people beyond the age of 50. Studies done in the past have shown that both atherosclerosis and macular degeneration are a result of the same disease process. In both the conditions, the underlying pathology is the inability of the body to clear fat and cholesterol deposition. Researchers associated with the present study, tried to find out whether medicines used for treating atherosclerosis would be beneficial in treatment of macular degeneration as well.

The two types of macular degeneration

Macular degeneration is basically of two types- the dry form and the wet form. In the dry form of macular degeneration, there is a collection of lipids beneath the retina in the eye. As the deposits increase in size, they start interfering with the vision. The result is gradual loss of vision, particularly in the central part of the eye. In a normal individual, the lipid collection is cleared by the macrophages. But in elderly people, where the macrophages are not working to their optimal capacity, the lipids are not cleared completely. On the contrary, the macrophages meant to remove them get filled with cholesterol and become sluggish. Their collection gives rise to an inflammatory process which, in turn, leads to the formation of new blood vessels. This neo-vascularization is characteristic of the wet form of macular degeneration and results in further impairment of vision. This is because the development of these abnormal new blood vessels is associated with bleeding and formation of scar tissue.

As a part of their study, the researchers analyzed the macrophages in humans and mice. They noticed that the macrophages need a protein, called as ABCA1, to clear cholesterol and fats. With the aging process, the level of this protein becomes insufficient in the macrophages. Therefore, the efficiency of macrophages in clearing cholesterol decreases. With low levels of ABCA1, the macrophages are no longer able to transport cholesterol outside the cells. This leads to an accumulation of cholesterol inside the macrophages.

Researchers Found An Eye Drop Which Could Reverse Macular Degeneration In A Mouse’s Eye

The researchers delivered two different types of cholesterol regulators namely, Liver X Receptor agonists and microRNA-33 inhibitors, in the form of eye drops into the eye of an old mouse. Both these drugs act by increasing the levels of ABCA1 protein inside the microphages. To their surprise, the researchers observed that the process of macular degeneration was actually reversed in the mouse’s eye. The macrophages were able to clear the cholesterol depositions more effectively and the development of new abnormal blood vessels was slowed.

The researchers are all the more excited, because by delivering the drug directly into the eyes in the form of eye drops, the systemic side effects can be reduced. As the macrophages play an important role in clearing the cholesterol, and their ineffectiveness can lead to diseases like atherosclerosis and neovascularization of cancerous tissue, the same pathway can be used to find more effective treatments for these conditions.

Studies done in the past had indicated an association between atherosclerosis and macular degeneration

Although it is only now that researchers have stumbled upon the fact that medicines used to lower cholesterol can be employed to reverse the process of macular degeneration, studies done in the past have already indicated an association between the two diseases.

Way back in 1995, a study published in the American Journal of Epidemiology, called as the Rotterdam Study, had concluded that age related macular degeneration is associated with atherosclerosis. The study, which was carried out by Johannes R. Vingerling, along with colleagues, enrolled 104 patients with macular degeneration and 1,324 participants without the condition. The study was carried out between March 1990 and July 1993 in Rotterdam, Netherlands. The researchers took fundus photographs of the participants to look for evidences of age related macular degeneration. Ultrasounds were carried out to find the presence of carotid atherosclerosis. Atherosclerosis in the arteries of lower extremities was also studied.

The researchers found that presence of atherosclerotic plaques in the carotid bifurcation, in participants younger than 85 years of age, was associated with 4.7 times increased prevalence of macular degeneration. Presence of atherosclerotic plaques in the common carotid artery was associated with 2.5 times increased prevalence of macular degeneration. Atherosclerosis of the arteries of the lower extremities was also linked with 2.5 times increased prevalence of the disease. This led the researchers to conclude that atherosclerosis may be playing a role in the development of age related macular degeneration.

Age related macular degeneration mainly affects the central vision

Age related macular degeneration usually affects the macula. It is the part of the retina consisting of millions of cells that sense light. It is responsible for providing a sharp, detailed central vision. Due to the damage to macula because of lipid deposition (as in dry macular degeneration) or development of new abnormal blood vessels (as in wet macular degeneration), the image perceived is pretty hazy. However, one rarely encounters complete blindness due to macular degeneration. Even though the central vision is impaired in this condition, the peripheral vision remains intact. Apart from atherosclerosis, smoking and a positive family history are two important risk factors for developing age related macular degeneration.

The treatment of macular degeneration is usually complicated and does not lead to a complete cure. However, in the wake of the new study, the future of the treatment of macular degeneration appears promising.