Eyes have often been called the ‘windows to the soul’, as they reflect a person’s inner emotions and thoughts. But new studies show that there is a lot more to eyes than, well, ‘meets the eye’. Fresh evidence suggests that eyes could also be windows to both the brain and body health, as they are the only part of the body that allows doctors to peer into the body non-invasively and examine a health condition.
Researchers claim that a regular eye examination, besides checking vision and correcting eye problems, can also help diagnose several health conditions, including, among others, diabetes, multiple sclerosis (MS), and even Alzheimer’s disease.
Before we begin, here are the basics on some eye functions. The pupil of the eye, or the small round opening in the center of the iris — the colored portion surrounding the pupil that gives eyes their characteristic color — changes in size to let the right amount of light into the eye. This is referred to as the ‘pupillary light response’. The pupil contracts in bright light and dilates as the amount of light decreases, so as to improve ‘visual acuity’, or how well you can see details of whatever specific you are looking at, under various light conditions.
Irrespective of the ambient light, pupil size also dilates in response to signals from the autonomic nervous system — the body’s alarm network — that warns us of threats, or opportunities, in a visual environment. This ‘visual sensitivity’, or how well you can see the overall environment and gather visual information from what you are looking at, is improved by dilation of the pupil.
Since the size of your pupil is not under your voluntary control, psychologists consider pupil dilation to be a cue to sexual or social interest. They maintain that contracted pupils are an indication of a lack of interest, while a dilated pupil shows signs of interest, whether in another person or a situation. The dilation allows the viewer to gather as much visual information as possible from whatever they are looking at, under the ambient light condition.
New research now shows that eyes not only provide clues to our emotions, they are also a valuable aid in diagnosing other illnesses. At the back of the eyeball is the retina — a light-sensitive layer of tissue — that captures light coming from an object and passes this information to the brain, along the optic nerve through electrical and chemical signals.
Recent studies by researchers at the Liverpool University Hospital in the United Kingdom reveal that the condition of these blood vessels and nerves can help to diagnose systemic diseases — those that affect other organs in the body or the whole body, such as hypertension, diabetes, thyroid disorders, and neurodegenerative diseases including Alzheimer’s disease, and multiple sclerosis.
Optometrists and ophthalmologists can clearly see blood vessels and the optic nerve when they conduct a regular eye examination to diagnose disorders of the eye such as nearsightedness, farsightedness, and astigmatism. By examining the blood vessels in the retina and the optic nerve, the eye-specialist can also non-invasively discover a lot about a person’s general health. If a routine eye test raises concerns of systemic disease, the examining ophthalmologist can then refer the person to a relevant specialist.
Diabetes is the most commonly diagnosed disease given the frequency of the illness as well as the classic findings on retina exam, which can include bleeding, leakage of fluid, and areas of poor blood flow. Although a firm diagnosis of diabetes can only be made with a blood glucose test, changes in the blood vessels of the retina can give a strong indication that a person may have diabetes. They can then be referred for further testing.
Signs of diabetic retinopathy — damages to the retina from high blood sugar — can sometimes be detected by eye examination even before a person suspects they may have diabetes. Once diagnosed, provided the diabetes is well controlled, the person can then minimize the risk of further eye damage. In addition, studies have shown that signs of hypertension, or high blood pressure, are found in the eyes of around 10 percent of the adult, diabetes-free population.
On examination, an eye doctor might see traces of narrowing of arterioles in the retina, arteriovenous nicking, retinal hemorrhages, all of which are indicators of hypertensive retinopathy. The good news is that if hypertension is detected and controlled early on, through appropriate precautions and lifestyle changes, the damage can be halted.
During a routine eye test, the eye doctor will also examine the optic nerve to look for any abnormalities or changes, as the optic nerve connects the eye to the brain and is therefore an extension of the central nervous system. It is the only part of the brain that can be clearly visualized by examining the back of the eye.
Optic nerve swelling or inflammation (optic neuritis) can be detrimental to vision and color vision, and can also be an indicator of Multiple Sclerosis (MS) — a potentially disabling disease of the brain and central nervous system. In MS, the immune system attacks the protective sheath (myelin) that covers nerve fibers and causes communication problems between your brain and the rest of your body, which could eventually lead to permanent damage of the nerve fibers.
Optic neuritis is the first symptom in up to 20 percent of people who are subsequently diagnosed with MS, although it can indicate other disorders, or even be the result of a viral infection or vitamin deficiency. If an optometrist suspects optic neuritis in a routine eye examination, they will refer a person for further testing to confirm the diagnosis and identify the cause.
Retinal screening of Alzheimer’s disease is another exciting prospect at the forefront of current medical research. Current methods of diagnosing Alzheimer’s are often lengthy, invasive and expensive, so being able to diagnose the condition from the retina would be a huge advance.
Recent research has suggested that doctors could, in the future, diagnose Alzheimer’s through retinal scans. The new technique, so far tested only in mice, combines the results of two scans to assess the condition of the retina. Those with Alzheimer’s disease have a much rougher retinal surface than those without. These findings could, in future, lead to easier, earlier diagnosis of Alzheimer’s disease enabling treatment to begin before symptoms become severe.
After 40 is when eye-specific ailments can start to become more common — including presbyopia, glaucoma, cataract, and changes to the retina from diabetes or high blood pressure. So doctors now recommend that anyone over 40 should get their eyes examined even if they have no need for glasses or contact lenses — it may detect a condition that you were unaware of and help you to take control of your health.
