Health & Wellness: How eye check-up can prevent strokes & heart attack

DOCTORSPEAK

It is well known that the heart pumps blood to all tissues of the body and recirculates it after oxygenation through the lungs. It does so via a highly complex network of arteries, capillaries, and veins. The arteries carry blood from the heart to various organs, while veins return blood to the heart.

During each heartbeat, a pressure of 90-140mmHg (average 120mmHg) is generated in the aorta, the main artery emerging from the left lower chamber, and blood is propelled throughout the body and regulated in the progressively narrowing large, medium, and small arteries and arterioles. This pressure is called systolic blood pressure (BP). The pressure maintained in the arteries between two beats is less than 80mmHg and is referred to as diastolic BP. The notation 120/80mmHg represents these measurements. BP is usually measured in the upper arm, specifically in the brachial artery just above the elbow.

As you age, beyond the 30s, the walls of the arteries gradually thicken and become less flexible. This stiffening of the arteries, mainly in the peripheral small arteries and arterioles, hampers blood flow. By age 40, the heart needs to pump more forcefully to overcome this resistance, leading to high BP during each heartbeat (systolic hypertension).

Peripheral resistance is a key factor in causing essential or primary hypertension, which accounts for 90-95 per cent of cases with high BP. Primary hypertension develops gradually and may show no symptoms; many people remain unaware they have high BP until they are screened for memory loss, slow thinking, neurological deficits, or a severe complication such as a minor or major stroke or a heart attack. The kidneys and eyes are also affected. Detecting high BP during routine check-ups and ensuring timely, effective treatment can prevent serious complications.

Undiagnosed numbers

Almost 140 crore people worldwide have high BP, with more than two-thirds living in low and middle-income countries. In India, approximately one in three adult men and one in four women suffer from hypertension. However, only about 20-30 per cent receive treatment, and fewer than half manage to keep their BP under control. Alarmingly, nearly half of the young individuals under 50 with hypertension are unaware of their condition, and around 20 per cent remain undiagnosed despite visiting healthcare facilities.

Not everyone develops high BP. The prevalence of hypertension is closely linked to higher socio-economic status, family history of hypertension or heart and kidney disease, smoking, a sedentary lifestyle and obesity. The widespread consumption of processed foods such as potato chips, namkeen, instant noodles, etc, often high in sodium and preservatives, has become a significant modifiable risk factor.

In 5-10 per cent of hypertension cases, a sharp rise in BP due to certain kidney or endocrine disorders requires urgent care to save their lives. The retina is the only tissue in the body where small branches of arteries (arterioles) can be directly observed by ophthalmologists. Interestingly, the walls of the retinal arterioles are transparent in young individuals. A gradual loss of transparency and increasing stiffness of the arterioles are signs of persistent hypertension. Dr IS Jain and Dr PL Wahi from the PGI, Chandigarh, discovered over 50 years ago that the stiffening of the retinal arterioles is linked to its adverse effects on the heart, leading to left ventricular hypertrophy (the thickening of the heart’s ventricles, the lower chambers that pump blood out of the heart). Interestingly, the retina is also the only tissue where arterioles visibly cross veins.

Indication of stroke risk

Hypertension-induced stiffening of the retinal arterioles causes compression of the underlying retinal veins, leading to incomplete or complete blockage of blood flow in the veins. This phenomenon, regardless of traditional risk factors, independently predicts the risk of stroke. The presence of retinal haemorrhages, widening of the retinal veins, and retinal infarcts (cotton wool spots) due to secondary hypertension indicates life-threatening hypertension.

Dr Tien Wong from Singapore has played a pioneering role in developing and applying the concept of ‘oculomics’, utilising retinal imaging to detect and predict systemic diseases. The retinal changes caused by hypertension reflect similar changes in the small vessels of the brain, heart, kidneys, and other organs, and can independently predict the risk of stroke, heart failure, kidney dysfunction, and overall mortality, regardless of traditional risk factors. Artificial intelligence (AI) tools developed by them to analyse these changes are being used in primary care and community health settings in Singapore to identify individuals at risk of systemic diseases and mortality.

National Health Service, UK, and the University of Cambridge are investigating these technologies. The World Health Organisation (WHO) has shown interest in scalable and affordable AI-based tools to improve hypertension and chronic disease screening from retinal pictures in underserved populations. The current definition of normal BP is less than 120/80. BP above it requires lifestyle modifications. If BP exceeds 140/90 mmHg, in addition to lifestyle changes, your doctor may prescribe medication.

The American Heart Association recommends monitoring BP at home for everyone. Use a BP monitor approved by your doctor. Avoid smoking, tea, coffee, or exercise for at least 30 minutes before measuring BP. Sit in a relaxed position for 3-5 minutes on a straight-backed chair with uncrossed legs, feet flat on the floor. Do not talk while recording your BP. Take three readings at 2–3-minute intervals and record the average of the last two readings to share with your doctor. When you next visit an eye specialist, ask them to take a picture of your retina! It could save your life!

Factcheck: Indian guidelines for hypertension management (2024) have revised the BP classification: g Non-elevated BP: