DOCTOR SPEAK: Healthy lifestyle can safeguard your vision in old age

MANY gene variants that protect us when young can have harmful effects in old age, including in the eyes, leading to the feared age-related macular degeneration (AMD).

Our ancestors first developed an early macular specialisation in the centre of the retina. It involved directing the eyes forward (orbital convergence). The forward-placed eyes provided sharp colour vision, depth perception and hand-eye coordination. Ageing primates also suffer from macular degeneration. It is a trade-off between sharp vision and longevity that evolution did not prepare for.

A specialised macula located in the centre of the retina has a central fovea that is densely populated with light and colour-sensitive photoreceptors (cones). It has among the highest oxygen consumption and metabolic rates of any tissue for converting light energy into neural/visual signals.

Lifelong exposure to bright light and metabolic activity causes oxidative stress, low-grade inflammation, and gradual accumulation of debris (drusen) in the fovea. This waste build-up blocks the flow of oxygen and nutrients to the foveal photoreceptors. Tiny areas of the fovea begin to die in susceptible individuals by the time they reach their 60s. The black spots obscure vision, especially in dim light. As the dead areas of the fovea merge, dark spots grow larger until central vision is completely lost. Eventually, the ability to see, read, write and recognition is permanently impaired.

In nearly 90 per cent of AMD cases, the photoreceptors in the fovea die gradually (dry AMD). However, in 5-10 per cent of cases, abnormal blood vessels sprout under the retina, leading to fluid leakage and bleeding, resulting in sudden distortion and loss of central vision (wet AMD), necessitating lifelong frequent injections into the eye.

AMD’s early stages are asymptomatic and detectable only by ophthalmologists. In most cases, AMD affects both eyes, but if AMD in one eye is more advanced, the person may miss it altogether. It is important to note that a person with AMD does not become completely blind and can still navigate and maintain independence around the house. Fear of blindness and isolation drives many elderly people into depression.

AMD was rare when first observed in 1850. In the early 20th century, life expectancy used to be low; only about 30 per cent of people lived up to 65. At present, the average life expectancy in India is around 72 years. In developed countries, it is over 80 years. One-third of individuals in these countries suffer from AMD.

India currently has between 149 million and 156 million people aged 60 and over, accounting for about 10.5 per cent of the population, and is projected to reach approximately 20 per cent by 2050. A population-based study conducted 15 years ago, including cohorts from both North and South India aged 60+, found early AMD in nearly 40 per cent of people, with 1.2 per cent experiencing vision-threatening AMD.

Dr Rajiv Raman from Chennai identified AMD in 22 per cent of the rural and 18 per cent of the urban populations of Tamil Nadu; of these, 90 per cent had early-stage AMD and 9 per cent had advanced-stage AMD.

Apart from age and genetics, AMD is associated with modifiable risk factors like smoking, high blood pressure, poor dietary habits and a sedentary lifestyle, which exacerbate metabolic damage leading to the early onset and increased severity of AMD. Those with a family history of AMD, and otherwise also, must stop smoking and control their BP and lipid levels. It is never too late to start exercising and adopt a healthier lifestyle. Those with an intermediate stage of AMD are recommended to take antioxidant supplements containing vitamins C and E, lutein, zeaxanthin, zinc, and copper (but under a doctor’s guidance), which can reduce the risk of AMD progression.

Notably, the fovea is rich in protective yellow pigments, lutein and zeaxanthin, which can minimise damage from photo-chemical reactions. Consuming at least 200 gm of dark green leafy vegetables and fruits (blueberries, persimmons) increases the density of these pigments. When combined with fatty fish, rich in omega-3, the risk of AMD is substantially reduced. Egg yolk contains highly bioavailable lutein and zeaxanthin. Flax and chia seeds, walnuts are good vegetarian sources of omega-3. As lutein and zeaxanthin progressively accumulate in the macula, the best time to start consuming them is in your 20s to 30s.

AMD is also strongly linked to the family history or genetics, and several pathogenic variants have been identified. However, all persons with these variants will not develop AMD, as these genes require epigenetic activation, triggered by the modifiable risk factors mentioned above. The American Academy of Ophthalmology, however, does not recommend testing for these genetic variants. With a healthy lifestyle, it is possible to control whether the harmful genes are activated in later in life.

AMD is not an inevitable consequence of ageing; how we live today determines how well we see tomorrow.

— The writer is Emeritus Professor, PGI, Chandigarh

ASK The EXPERT

Have a low FODMAP diet for IBS

I have Irritable Bowel Syndrome (IBS) since childhood. I can’t digest sour food, milk, juices, cold drinks. I have been taking vitamin B12 and D supplements for nearly four years, as my levels were low. Now an ultrasound shows cyst (10 mm) in kidney and soft tissue (2mm) in gallbladder. Do vitamin supplements cause cysts as earlier I had no cysts. Please advise a vegetarian diet.

— Vijay Kumar (47), Chandigarh

Milk indigestion and tight stomach are due to the IBS. Vitamins B12 and D3 are safe and do not cause cysts. The soft tissue lesion in gallbladder is likely a GB polyp. Best to consult a specialist. Opt for a low FODMAP diet. Almonds, walnuts in small quantities are safe. Consume washed lentils, quinoa, carrots, potato, broccoli, bell peppers.

— Dr Aakash Aggarwal, Gastroenterologist Ojas- Alchemist Hospital, Panchkula

I am pre-diabetic and have high BP, and taking medicines. I have disturbed sleep at night. My wife, too, faces the same problem. Please suggest how to have sound sleep naturally without taking sleeping pills.

— Sushil K Sharma (59), Jalandhar

Even with medical issues, natural sound sleep is possible. Go to bed and wake up at the same time daily, eat a light dinner by 7:30 pm, and avoid tea, coffee, alcohol, heavy, spicy food at night. Limit screens before bed. Take a warm bath or wash feet with warm water. Take slow, deep breaths. It will relax the nervous system and lower BP. Morning sun exposure and a daily walk also help. A glass of warm, low-fat milk at night and gentle relaxation techniques are usually helpful, but any supplement (like magnesium) should be discussed with your doctor.

— Dr Ivan Joshi, Gastroenterologist, Max Super Speciality Hospital, Mohali

My 30-year-old daughter has thyroid and takes 125 mg medicine. Due to thyroid, she has gained weight, and faced repeated rejection of marriage proposals, affecting her emotional well-being. Kindly guide us how can she lose extra weight, live a normal life, and we may solemnise her wedding.

— Mohinder Kumar, Patiala

Hypothyroidism is common in women and may cause weight gain if TSH levels are uncontrolled. Medication can control thyroid. Once controlled, it alone can’t cause weight gain. A low-calorie diet, regular exercise, proper sleep with a regular schedule, stress reduction, and avoiding junk, high-salt-and-sugar, ready-to-eat foods can help in weight loss. You can also ask your doctor for weight-loss drugs. With lifestyle changes, thyroid is not a barrier to weight loss, fertility, or marriage.

— Dr Kanupriya Jain, Gynaecologist, Cloudnine Hospital, Ludhiana