Macular degeneration – a blinding issue of old age
11th October is the ‘World Sight Day’. What is the scenario of blindness in the world today? Or one may ask what will be the fate of our sight in future? 285 million people are visually impaired around the world. 90% of visual impaired reside in developing countries. 39 million people are blind that is severe visual impairment. 80% of blindness is avoidable. 65% visual impairment is belong to 50 or older age group. Glaucoma (12.3%), Age related macular degeneration (ARMD) (8.7%), corneal opacity (5.1%), Diabetic retinopathy (4.8%) is the common causes of visual impairment.
What is sight or vision?
Vision is a special sense by which the qualities of an object ( as color, luminosity, shape & size) constituting its appearance are perceived through a process in which light rays entering the eye are transformed by the retina in to electrical signals that are transmitted to the brain via the optic nerve.
Visual impairment is the functional loss of vision that can not be corrected by conventional means as refraction, medical or surgical treatment resulting from diseases, trauma, congenital or degenerative process.
How retina helps us to see the world or function of retina?
Retina is a highly metabolic organ or we can say it is a highly active organ, which uses high rate of oxygen. Retina is a thin layer of light sensitive tissue at the back of the eye. Human eye is like a camera that collects, focuses and transmits light through a lens within eyeball to create an image of its surrounding. This image create electrical signal in the retinal tissue, which is propagated to the brain in its posterior part (visual cortex). The brain interprets this signal and helps to see the surroundings.
Impact of visual process on retina:
This active process of image formation and conversion of light to electrical signal and propagation of the signal causes huge amount of oxygen consumption in the retinal tissues. During oxygen consumption or oxidative reaction several oxygen derived free radical like singlet oxygen, hydrogen peroxide etc are liberated in the site. These free radicals are injurious to normal retinal tissue. The tissue damage caused by the free radical is called oxidative stress. Retina is highly vulnerable to oxidative stress due to its high oxygen consumption; high proportion of polyunsaturated fatty acid and constant exposure to visible light. To minimize the damaging effect of free radical injury it is very urgent to detoxify the free radicals immediately after their production. This detoxification is naturally done by the anti-oxidant. The common anti-oxidant is vit-A or beta carotene, vit-C, vit-E, Lutein, Selenium, Flavinol, Lycopene, Cu, Zn etc.
What is Macular Degeneration or ARMD?
Most highly sensitive part of the retina is called the macula lies in its central area. Long continued oxidative stress can cause permanent damage to the retinal tissue specially the macula. This happens gradually as a result of commutative damaging effect of oxidative stress as the age advanced. This condition is known as age related macular degeneration (ARMD).
Presentations of ARMD:
1. Vision will reduce gradually at age 50 or above.
2. Difficulty in reading or other near work even with spectacle.
3. Near work demands more light.
4. Difficulty to recognize face from usual distance.
5. Black/ dark spot in front of vision.
6. Difficulties faced in both eye.
Risk factor for macular degeneration:
1. Age- usually after 50 yrs.
3. Family history.
4. U-v light exposure
5. cardiovascular diseases
6. over weight
7. Dietary habit.
Diagnosis: an ophthalmologist can easily diagnose a case of ARMD by clinical examination of retina by ophthalmoscopy and with the help of different diagnostic tools like amslar greed chart, fundus photography, OCT, fluorescein angiogram etc.
Macular degeneration is an aging process and irreversible condition. Consequence is mild, moderate to severe visual impairment. As the condition is bilateral, one stage patient become visually disabled or handicapped. Now the population size of 50 yrs and older is 20% of the total population. The size is increasing as the life expectancy is increasing. The burden of macular degeneration will be increased in future. So it can be said that each and every people over 50 has a chance of macular degeneration. There is no effective treatment of macular degeneration yet. So the big question arises how this issue will be resolved.
Life long battle with macular degeneration:
To address macular degeneration main key is to minimize the oxidative stress or accelerate detoxification of radicals or oxygen intermediates by anti-oxidants.
There are two way of having anti-oxidants in our body.
1. One way is dietary intake of anti-oxidant and another is
2. Nutritional supplement of anti-oxidants (tablet or capsule containing anti-oxidant).
Diet high in multiple anti-oxidants lower the risk of macular degeneration to a greater extend than does diet high in single anti-oxidant.
Healthy lifelong dietary practice rather than the consumption of high amount of narrow range of specific nutritional supplements protect macular degeneration.
Low glycemic index food (smaller & slower rise of sugar in blood after intake) with low/ moderate intake of saturated/ polyunsaturated fat and high intake of fish, nut, seeds and whole grain might protect macular degeneration (ARMD).
High glycemic index food (high & fast rise of sugar in the body after intake) with high fatty diet associated with ARMD.
Low glycemic index include- plenty of fruits, Vegetables, whole grain (pulse etc) legumes, milk etc.
High glycemic index include- cornflakes, Rice bubbles, puffed wheat, watermelon cereals, glucose, maltose, white potatoes, white bread etc.
Intermediate glycemic index- ice-cream, bear, grapes, basmati rice, sucrose (Cane)
Sources of anti-oxidant:
Beta-carotene (vit-A) are abundant in pumpkin, mango, spinach, carrots etc.
Vit-C- are abundant in orange, mango, broccoli, spinach, peppers, and kiwi fruits.
Vit-E – are abundant in nuts, seeds, bean, lentils, vegetable oil, whole grain etc.
Lutein- are found in corn and leafy green.
Lycopene- are found in tomato, watermelon.( reddish color is due to lycopene).
Selenieum- are found in whole grain, sea food & lean meat (animal source)
Flavinoids- are found in green tea, onion, apple, citrus fruits etc.
Cu & Zn- are found in nuts, legume, sea food, lean meat & milk. (Last three are animal source).
Few important notes to combat macular degeneration:
From above list it is clear that dietary sources of ant-oxidants are chiefly plant origin. Only few are derived from animal source.
Bright color of the vegetables/ fruits means more chances of anti-oxidants.
Highest anti-oxidant containing vegetables are spinach, red cabbage and broccoli.
Sunlight, smoking and pesticides all accelerate ARMD.
Vegetables/ natural dietary intake of anti-oxidant are better option than supplement (tablet or capsule)
Smoker should avoid beta carotene and lutein supplement as it is associated with lung cancer.
Lutein and xeaxenthene effectively absorb and screen high energy blue light that damage retina and lens causing ARMD & cataract.
Anti-oxidant can also help to prevent stroke (CVA), fertility, asthma, cancer etc.
Intake of several anti-oxidants one by one is least effective. Rather a bunch of anti-oxidants intake is more effective.
Best is to change the living style and intake anti-oxidant rich different food items daily and make it life long habit so that maximum protection against ARMD will be ensured. This is the only effective weapon for life long battle with ARMD to push away the blindness as much far away as possible.
Dr. Md. Sayedul HoqueMBBS, FCPS, MS (ophth) National Eye Care Centre Ring Road, Shyamoli, Dhaka. Ex-Associate Professor National Institute of Ophthalmology & Hospital