Understanding Age-Related Macular Degeneration and the Risk Factors and Causes of the Disease

Introduction

Age-Related Macular Degeneration (AMD) is now the leading cause of new blindness in patients 55 years and older, yet in the 1970s it was practically unknown.

What's going on? Why is it so common today?

Being aware of the risk factors and causes of macular degeneration mentioned below, will provide answers to these questions about AMD and the macular degeneration treatment options.

What is Age-related Macular Degeneration?

AMD is actually two different diseases.

• "Dry (Atrophic) Form" AMD in which the central part of the retinal (the macula) deteriorates. This constitutes about 85% of all AMD.
• "Wet (Neovascular) Form" AMD in which new but defective blood vessels grow under the retina and leak fluid. This is the other 15% of AMD.

The Dry Form may transform into both Dry and Wet Forms.

Macular Degeneration	Normal Retina

All of us have "two retinas in one".

The central retina (macula) sees the fine detail when you look directly at something.

The outer part of the retina is for peripheral vision and is very important for walking or moving around without running into things.

What Age-related Macular Degeneration Does

• Macular Degeneration affects the central retina, or macula, but leaves the peripheral retina alone.
• It becomes difficult or impossible to see fine detail.
• Faces are blurred.
• Reading is very difficult.
• You can lose your driver's license.

Risk Factors of Age-related Macular Degeneration

Both Dry Form and Wet Form have similar risk factors.

• Smoking. If you have AMD and continue to smoke, you are at very high risk to go blind. Smoking generates such an intense amount of free radicals and reactive oxidative stress (ROS) that nothing else is going to help.
• Heredity. If you have close family members in your gene pool with AMD you have an increased risk.
• High Body Mass Index (BMI). Being overweight makes you more likely to develop AMD and to have a more severe case.
• Female. Women have a higher BMI than men (See above).
• Blue-eyed. Blue-eyed people have less pigment in the macula and less pigment is a risk factor.



Blue eyes aren't always an advantage...
• Diet low in dark green leafy vegetables (like spinach, kale, chard, collards, beet greens). These are the best sources of lutein and zeaxanthin, the two critical pigments in the macular area.
• The body can't make either of them.
• They must come from the diet.
• Low lutein in the diet means low lutein in the macula. Low macular lutein is a risk factor for AMD.
• Low HDL cholesterol. Recent studies indicate lutein is carried to the macula by HDL.
• Poor circulation. This is more of a risk factor for Wet Form than Dry Form.

Causes of Age-Related Macular Degeneration

Dry Form Macular Degeneration Is Felt to Be Multi-factorial

• Genetics. Recent work has suggested the possibility of a defective enzyme that reduces the conversion of lutein to meso-zeaxanthin. Meso-zeaxanthin is an isomer of lutein that is the primary pigment found in the center of the macula. It is a strong antioxidant and also preferentially absorbs blue light, which is the most damaging to the macula.
• Diets low in green leafy vegetables result in low amounts of macular carotenoid pigments. These pigments act as antioxidants to prevent damage from light-induced free radicals and reactive oxygen species (ROS) and also to absorb blue light, which is the most damaging to the macula. Maculae that are low in pigment have more damage and develop AMD more frequently.



Popeye was right. Eat your spinach.
• Diets high in dark-green leafy vegetables have been shown to produce thick macular pigments which are protective against AMD.
• Smoking produces such intense oxidative stress by liberating tremendous amounts of free radicals and ROS. It's felt that this mechanism causes so much damage to the weakened retinal cells that no treatment has been found to be effective. It's like trying to put out a bonfire with a squirt gun.
• Low HDL cholesterol transports lutein from the gut to the retina. Low HDL therefore reduces the transport mechanism and results in lowered macular pigment. Docosahexanoeic acid (DHA) from fish oil increases HDL and has been shown to be synergistic with lutein.

Causes of Wet Form Macular Degeneration Are Also Multi-factorial

Most of the same factors are true for Wet Form. Due to its different nature it has some special ones of its own...

• Low oxygen tension in the macula from poor blood flow causes the release of chemicals that promote the growth of new and defective blood vessels.
• VEGF (Vascular Endothelial Growth Factor) causes uncontrolled growth of leaky blood vessels in places they aren't supposed to be.
• The leaking fluid collects and "drowns" the tissues, causing more VEGF release and more neovascularization (new vessel growth).

Vision loss with Wet Form is often very sudden, though it can be slow. Vision loss with Dry Form is almost always slow.

If Dry Form damages circulation and releases VEGF it can convert to Wet Form.

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