How Your Eyes Can Reveal Hidden Health Conditions

Melissa, a 30-year-old teacher, arrived at the emergency department after suddenly developing double vision. She had not been involved in an accident, had sustained no injury and had never had this symptom previously.

A few months beforehand, however, she had noticed blurred sight in one eye, which soon returned to normal. Following an intensive period of screen work, she had assumed it was simply due to tiredness.

Initial optometric assessments, followed by more specialised visual-perception tests, suggested that the episodes could be linked to multiple sclerosis. Melissa was referred to a neuro-ophthalmology specialist, who confirmed the diagnosis and ensured she received prompt treatment.

Was Melissa’s experience unusual? During my 30 years as an optometrist, I have encountered numerous patients with visual and eye-health concerns that were ultimately caused by an undiagnosed illness.

As a professor at the School of Optometry at the Université de Montréal, I teach students that some eye-related symptoms may point to wider health conditions.

Optometrists are trained to recognise diseases that may reveal themselves through the eyes, and to collaborate with other healthcare professionals in their management.

Diabetes

With diabetes expected to affect almost 8 percent of the population by 2030, screening is essential. Yet diabetes is estimated not to be diagnosed, in general, until six to 13 years after it begins.

An eye-health examination can reduce that delay, as characteristic damage caused by the disease can often be detected at the back of the eye before other diabetic symptoms emerge.

Prompt diagnosis matters because, within five years of diagnosis - that is, 11 to 15 years after diabetes starts - 25 percent of patients with Type 1 (juvenile diabetes) and 40 percent of insulin-treated patients with Type 2 (adult diabetes) will develop eye damage that may seriously affect their sight.

Detecting problems early and closely monitoring eye health greatly lowers the risk of blindness, which may occur when the condition remains untreated.

Revealing the silent killer

If many people have diabetes without realising it, the same question applies to high blood pressure and high cholesterol. Both conditions substantially raise the likelihood of coronary heart disease or stroke in our societies.

The eye is the sole location in the human body where blood vessels can be observed without an incision or invasive procedure.

• High blood pressure, often called the silent killer, may be identified through compressed vessels and highly distinctive retinal signs.
• Hypercholesterolaemia results in cholesterol deposits within blood vessels.
• Atherosclerosis is linked with Hollenhorst plaques, which can likewise be seen inside vessels.
• Cholesterol may also be visible in the cornea as a lipid arc, or in the adnexa as xanthelasma.

In each of these situations, patients frequently have so few symptoms - or symptoms that develop so gradually - that they regard them as almost normal.

Normotensive or open-angle glaucoma

Glaucoma is also typically symptom-free. This disorder of the optic nerve is generally linked either to excess production of aqueous humour within the eye or to insufficient drainage of it.

Pressure inside the eye consequently rises and, through several mechanisms, causes nerve fibres to be lost. The visual field contracts extremely slowly and may therefore pass unnoticed, eventually leaving the individual with tunnel vision after a number of years.

When the vision loss becomes apparent, it is often already late and the optic-nerve damage may be severe. Although this damage is principally ocular, it can also be caused by the effects of certain medicines, including cortisone.

Normotensive glaucoma is quite different. Here, eye pressure stays within the normal range, but the nerve nevertheless becomes damaged. The processes involved differ from those seen in chronic open-angle glaucoma.

Normotensive glaucoma is commonly linked to low blood pressure or conditions including sleep apnoea. Where it is identified, the patient should be referred to their GP for a comprehensive assessment.

The disease of the century

As cancer is increasingly widespread and can present in so many forms, it is described as the disease of the century. Cancers involving the eye, such as retinoblastoma, may also metastasise to the lungs and liver.

Again, the condition often progresses without symptoms until it is too late. Early detection is therefore vital, as the patient’s survival may depend on it.

Other symptom-free types of retinal pigment, resembling a bear’s paw, may be associated with colon cancer, which has a very poor prognosis when treatment is delayed.

A straightforward visual-field test can identify abnormalities of which patients may be unaware, or which they may consider too minor to mention. Yet many visual-field abnormalities conceal brain tumours, including pituitary adenoma, or nerve fibres compressed by blood vessels.

Unusual eye movements, uneven pupil responses, abrupt difficulties with reading and the onset of diplopia are all warning signs requiring additional eye and neurological examinations.

Rather than serving as the mirror of the soul, the eyes can offer an unobstructed view of our general health.

This makes regular appointments with an optometrist more important than ever, including for people without symptoms. Many conditions can be discovered and treated, either to minimise illness or to prevent it altogether.

Langis Michaud, full professor, School of Optometry. Expertise in eye health and the use of specialised contact lenses, University of Montreal

This article is republished from The Conversation under a Creative Commons licence. Read the original article.