From Diabetes To Dementia: The Eye As A Window To Your Health

The eye is a fascinating part of the human body. It is uniquely composed of transparent structures so as to allow light to enter.

- Dr Khor Wei Boon

This transparency allows eye doctors to directly observe the optic nerve, which is actually a part of the brain. What may surprise many is that the brain, the eye and the optic nerve all originate from the same group of embryonic cells during gestation.

During this period, the cells destined to become our brain extend two thin tubes of tissue that eventually form the eyes and optic nerves.

This ability to examine the inner structures of the eye, and observe how systemic conditions affect the nerves and blood vessels of the eyeball is why the eye is often referred to as a window to our overall health. Through a combination of photographs, scans and artificial intelligence (AI), ophthalmologists and researchers aim to use this window to predict the risks of heart attacks and strokes, and even to detect signs of dementia before a person is aware of it.

LINKING THE BODY TO THE EYE

Lining the inner surface of the eyeball is a thin membrane called the retina. The retina is composed of light-sensing cells situated beneath layers of incredibly delicate nerve fibres - so fine that they are transparent to the naked eye. These nerve fibres converge to form the optic nerve, which also gives rise to the network of blood vessels that nourish the retina (see Figure 1).

While intrinsic eye diseases can damage the retina, conditions originating from outside the eye can also cause harm. For example, poorly controlled diabetes can lead to bleeding in the retinal blood vessels, resulting in a condition known as diabetic retinopathy. If high blood sugar is damaging the vessels in the eye, it stands to reason that the fine blood vessels in other parts of the body, such as the heart or kidneys, may also be affected. Conversely, could heart problems or kidney disease manifest as tell-tale signs in the eye?