Macular degeneration (AMD)

Age-Related Macular Degeneration – What You Need to Know

The first thing to be said about macular degeneration is that you will never go totally blind from it. Central vision may be lost to a point where you cannot drive, read or see the television clearly,however it must be understood that you will never loose your peripheral vision from AMD and you will always be able to see sufficiently to walk around your house and your garden. The majority of AMD sufferers can also make their way to town and do the shopping and other tasks with ease.

Age-related macular degeneration is a leading cause of vision loss and ‘blindness’ in the world  today and is referred to as ‘AMD’ or ‘ARMD’. It is a continuously growing problem affecting about 3.68% of the population aged 65 and older and may grow to 5% of people by the year 2020.

Age-related macular degeneration is the deterioration of the macula situated in the centre of the retina providing visual and colour acuity enabling one to read, write or drive.

Macular degeneration comes in two forms, the dry (non-neovascular) and wet (neovascular) types. Neovascular (wet) is an abnormal pattern of new but fragile blood vessels that invade the retina from the vascular layer beneath, called the choroid.

Dry (Non-Neovascular) Macular Degeneration

This is the early phase of AMD and is more widespread occuring in about 90% of affected patients. It presents with aging and thinning of macular tissues or with the development of pigment deposits in the macula or sometimes both. It is characterized by yellowish spots called drusen, which are deposits of fragments of deteriorating retinal tissues and waste products that have accrued in and around the macula.

With dry AMD, vision loss is gradual but can later lead to late-stage geographic atrophy (GA) from slow damage of retinal cells that result in central vision loss.

Vitamins A, C and E may help prevent or delay the condition according to a study done by the National Eye Institute (USA) who encouraged the development of nutritional formulas that can help. Supporting facts were established that high dosage intake of nutritional supplements in eye vitamins can help lessen the progress of early-stage AMD by 25%.

Dry AMD treatments are available while FDA-approved cures are still being clinically tested. Patients are advised by eye doctors to protect their eyes from further damage caused by the sun by wearing UV protective sunglasses and appropriate tints.

Wet (Neovascular) Macular Degeneration

When the retina suffers from macular degeneration, the body produces new blood vessel system in a vain attempt to distribute nutrients and oxygen to the tissue however these fragile vessels leak easily casing scarring and sometimes catastrophic bleeding with sudden loss of central vision. This is called choroidal neovascularization (CNV), the process that causes wet AMD.

Dry AMD patients often experience a worsening of the condition where continuing damage from free radicals causes relentless damage of the macula. This can severely harm the light-sensitive retinal cells (photoreceptors) causing central vision blind spots.

In December 2003, Ophthalmology Clinics of North America reported that neovascularization and damage caused by wet AMD may be the result of weak, oxygen-deprived retina cells. Vascular endothelial growth factor (VEGF) is a protein type that causes neovascularization and is the focus of anti-VEGF treatments.

Two Types of Wet Macular Degeneration

  1. Occult

Occult CNV wet macular degeneration type does not result to severe loss of vision. There is less intense growth of new blood vessels and leakage is not as obvious.

2. Classic

This type has very defined new blood vessel growth under the retina causing distinct scarring that typically leads to severe loss of vision.

Symptoms, Signs and Causes of AMD

Loss of vision caused by AMD is usually slow and painless but it can be sudden in some rare cases. At the onset, patient may experience either dim spots in central vision or see images that are unusually hazy or warped.

Even without symptoms, a retinal exam to measure central vision can help detect early signs of macular degeneration. When distortion or blurriness is detected by an eye doctor, a flourescein angiography may be performed to check retinal blood vessels near the macula.

AMD’s characteristic central blind spots

Research carried out by Duke University established that while blindness due to macular degeneration is linked with aging, a genetic deficiency called complement factor H (CFH) may also cause it. Meanwhile, complement factor B may cause AMD development according to the study of Columbia University Medical Center and other researchers. Variants of the said genes influence the body’s immune reactions.

The study found the presence of both genes in 74% of the patients where risk of developing AMD is increased by another gene variant, the complement factor C3.

The Risk Factors

Aside from age, AMD can be caused by other suspected factors that are currently being studied such as over-exposure to sun light and high levels of fat in the diet.

Age

The Canadian Medical Association (February 2004) found 1% of people aged 60 and above suffer vision loss due to advanced AMD while 15% of people aged 90 and above have visual defects due to AMD.

Obesity and Sedentary Lifestyle

The Archives of Ophthalmology established that risk is higher to inactive and obese people as opposed to those with ideal weight who engage in regular vigorous activities.

Genetics

Heredity factor that involves some variant genes types have been found by recent studies to be a factor in AMD development and in its severity.

Hypertension

Investigative Ophthalmology and Vision Science (September 2003) found that high blood pressure may influence AMD development based on their conducted study.

Smoking

A risk factor to many other diseases, a study by British Journal of Ophthalmology found smoking (or living with a smoker) to increase risk by twice as much after 25% of subjects had severe vision loss due to AMD.

Drugs

Drugs cause side effects and some of them are found to possibly cause macular degeneration such as anti-psychosis phenothiazine, anti-nausea and hiccups drug Thorazine (chlorpromazine), Mellaril (thioridazine), Trilafon (perphenazine), Prolixin (fluphenazine), anti-malaria Aralen (chloroquine), and Stelazine (triflouperazine).

Some studies state that white people with lighter skin and eye color are suspected to be at higher risk of developing AMD while those with darker eyes are protected from the sun because of extra pigmentation. However, the study of the British Journal of Ophthalmology (January 2006) found no certain evidence that too much sun exposure or lighter eye and hair color can lead to acquiring the eye condition. Contradictory risk factors were also noted by the American Academy of Ophthalmology save for aging and smoking.

Treating Macular Degeneration

AMD has no absolute cure only treatments to prevent it from worsening and may depend on its stage especially for wet form. Abnormal blood vessel growth may be prevented by FDA-approved medication like Lucentis, Eylea, Macugen and Visudyne along with Photodynamic Therapy (PDT). Dry form, meanwhile, may benefit from nutritional supplementation so that it does not progress into wet form.

Treatments of macular degeneration are continuously improved by research laboratories. Low vision devices can aid in the mobility and functions of those whose vision was lost due to the eye condition.

Helpful Nutrients

Eye care professionals believe that some nutrients and their nutritional benefits can help reduce AMD risks, its development and progression. This was supported by 2001 and 2005 research studies of the National Eye Institute through Age-Related Eye Disease Study (AREDS).

-Zinc

-Lutein

-Zeaxanthin

-High levels of antioxidants

-Vitamins A, C and E

-Omega-3 fatty acids (good fats)

-Green, leafy vegetables

Archives of Ophthalmology (August 2001) also stated that of omega-3 fatty acids common in cold-water fish can fight advanced macular degeneration. On the other hand, omega-6 fatty acids found in vegetable oils may boost AMD development. Brocolli and spinach are supposed to be a good supply of the macular pigment Lutein and should be included regularly in the diet of suffers, or people at risk, of AMD.

How is AMD Detected?

Eye doctors advise patients to use an Amsler grid, a viewing chart with-graph patterned black lines, to check for vision problems. What may not be seen in a routine eye exam may be detected by the sensitive Amsler grid in determining AMD in a patient. Patients should carry out this self-test once weekly on each eye.

An Amsler grid is the visual test to detect the presence of AMD. A person with AMD would see the lines become wavy and the central blind spot located in an incorrect position

 

AMD can be diagnosed by examination of the macula of your eye by using a direct or indirect ophthalmoscope which all eye doctors have. Retinal photography is also very useful in documenting AMD and convenient in explaining the condition to the patient. An OCT is a new machine that measures the back of the eye and can estimate how much damage has occurred in AMD. This modern technology is available at Medical Optics and the eye doctors working in the two practices have special training in using the OCT to determine the exact diagnosis of AMD. Sometimes it is necessary to also undergo a test called fluorescein angiography (FA) which your eye doctor will arrange if appropriate.