Age Related Macular Degeneration
The spotlight has once again fallen on age-related macular degeneration (ARMD), the most common cause of central vision loss for people over 65. In a previous edition of Health Intelligence, we reported on the strong link between ARMD and heart disease. One possible culprit, studies have shown, is an artery-damaging amino acid, called homocysteine. The higher the level of homocysteine in our blood, the greater the chances that we may not only lose our central vision as we grow older, but also suffer from either heart disease or a stroke.
New research has brought a fresh angle to the story of aging eyes. ARMD may be yet another detrimental effect of poorly balanced hormone levels, a situation which also worsens as we age.
Wet and dry
It may sound like the tagline for an expensive vacuum cleaner, but ARMD also comes in “wet” and “dry”. But before you can determine which kind you’re dealing with, you first need to know where to find the macula – from which the word “macular” in ARMD is derived – as well as to understand how this part of the eye works.
The macula sits close to the centre of the retina, which is the light-sensitive layer of cells inside and at the back of the eyeball. This whole area is chock-a-block with tiny blood vessels that supply the retina with much-needed oxygen and nutrients. The retina is also connected directly to the brain via the optic nerve, in fact, eye specialists think of it as an extended part of the brain. The reason for this will become clear as we explore further.
The macula is responsible for sharp central vision, the kind we need to read, drive a car or make out the faces of actors in a movie. Since it’s responsible for this important and sharpest part of our vision, it’s also the most intricately structured and most sophisticated section of the eye, which is why it is sensitive to all kinds of damage. Think of an expensive, high-tech camera and how easily it would break if you dropped it, or left it in the sun.
When dry ARMD sets in, the layer of cells just beneath the retina begins to harden and dry out, a process called atrophy. Also, tiny yellow particles, called drusen, begin to collect in the macula over time. While dry ARMD is often blamed on the drusen itself, there are cases in which drusen spots collect, but there’s no loss of vision. Be that as it may, the net effect of the hardening and drying of the macula is a very gradual blurring of your central vision. This could lead to partial blindness in old age.
Wet ARMD is more serious, but luckily it’s far less common. It occurs when abnormal blood vessels begin to form below the macula, which is presumably the body’s way of trying to circumvent the dried and hardened parts caused by dry ARMD and to keep the macula alive with oxygen and nutrients. But these blood vessels are usually not very well-formed and they begin to leak. The result is worse than before, as your central vision rapidly begins to blur.
Although much of the literature on ARMD speaks of “blindness” setting in, eye specialist Dr Clive Novis explains that the word could be misleading. “ARMD does not lead to total blindness. The peripheral vision is spared, so the person’s mobility and independence are preserved. Magnifying devices can allow many ARMD sufferers to read large print and watch TV, provided that the ARMD is not too advanced. But ARMD can cause ‘legal blindness’, which is a permanent loss of central vision or a constriction of the peripheral visual field below certain levels. Legally blind people can claim a blind disability pension.“
The good news is that we’re getting closer to understanding what causes ARMD, which also means that we’re getting a better grip on its prevention.
The hormone clue
One of the world’s leading researchers in the area of eyes and anti-aging medicine is Dr George W. Rozakis, a biomedical engineer in the US, who specialises in laser eye surgery and lens implants. Dr Rozakis made the connection between ARMD and hormones when he read a study published in the American Journal of Opthalmology, which showed that people who suffer from ARMD also had exceptionally low levels of the hormone dehydroepiandrosterone (DHEA). This hormone is the parent of all of the sex hormones in the body, meaning that it “gives birth” to the estrogens – estrone, estriol and estradiol – and to testosterone. If the level of DHEA in the blood is low, it also means that the body is deficient in the hormones for which DHEA is responsible.
Dr Rozakis also knew that, just like the brain, the retina contains cells that are sensitive to hormones, which is one reason why the retina is seen as an extension of the brain. In fact, a key study showed that the retina is even able to make its own hormones – again, just like the brain. The same study revealed further that many hormones targeted by anti-aging medicine, such as pregnenolone, DHEA, testosterone, the estrogens and progesterone, play a key role in maintaining a healthy retina. The problem is that very few eye specialists are aware of this important fact.
Connecting the dots
The final discovery came when researchers took a closer look at the drusen spots themselves, which occur in most cases of ARMD. Up to this point, most doctors believed these little yellow globules were made up of waste products produced by an already damaged macula. But this did not explain why drusen was sometimes also noticed in cases where there was no blurry central vision yet. The study’s answer to this was a complete paradigm shift: when the spots were carefully analysed, the researchers discovered they contained no waste products, but mostly cholesterol, which is the raw material from which all hormones in the body are made.
This was a eureka moment for Dr Rozakis. He realised that, as we age, the hormone-producing cells in the eye begin to slow down and gradually lose their ability to make hormones. Cholesterol – the raw material needed for the production process – then begins to build up, forming the little yellow spots. But if the hormone deficiency worsens with age and over time, the retina just cannot keep up making hormones any longer and the macula begins to dry up and harden.
As studies have shown, this process is echoed in the rest of the body. The adrenal gland, which produces DHEA, loses the ability to manufacture hormones as we age. This decline stimulates the liver to produce more cholesterol in an attempt to create more hormones, which is why restoring hormones to normal levels reduces cholesterol.
Similarly, if we can keep providing the retina with the hormones it needs as we grow older, it may be the breakthrough we need to make blurry vision in old age a thing of the past.
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