Evidence is increasingly suggesting a person’s eyes provide potential non-invasive ‘windows’ to the secrets of both our brain and body.
Health conditions detected by routine eye examination now including hypertension, diabetes, thyroid disorders, and neurodegenerative diseases such as multiple sclerosis and Alzheimer’s disease.
UK ophthalmology specialist Dr Hagar Ibrahim told medicalnewstoday.com: ‘A routine eye examination in which pupils are dilated using eye drops can provide a full and clear view of the optic nerve, which connects to the brain, the retina and all the blood vessels supplying the retina.
‘Therefore pathology of the eye can be clearly seen during an eye examination, both in localised eye conditions and in systemic disease, truly making the eye a window into the rest of the body.’
US ophthalmologist Dr Philip Storey noted: ‘People are often surprised when an eye doctor diagnoses them with a systemic illness, but they shouldn’t be. Many people with systemic illnesses are first diagnosed by their eye doctor, which is just one reason all adults should have regular eye examinations at least every 2 years.’
Changes in the blood vessels in the retina can be early indicators of both diabetes and hypertension, with Dr Storey telling medicalnewstoday.com: ‘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.’
Indicators of hypertension seen by an eye doctor include traces of narrowing of arterioles in the retina, arteriovenous nicking, retinal haemorrhages and (as in diabetic retinopathy) microaneurysms.
Dr Storey noted: ‘Hypertension presents with classic signs within the eye. The earliest signs are narrowing of the vessels, often referred to as “silver wiring” because of their appearance.’
Dr Ibrahim added: ‘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 visualised by examining the back of the eye.
‘Optic nerve swelling or inflammation can be detrimental to vision and can diagnose MS, as well as neuro-inflammatory disorders such as neuro myelitis optica or brain tumour.’ (Optic neuritis is the first symptom in up to 20% of people subsequently diagnosed with MS.)
While current methods of diagnosing Alzheimer’s are often lengthy, invasive and expensive, Dr Ibrahim said: ‘Retinal screening of Alzheimer’s disease is an exciting prospect at the forefront of current medical research.
‘The retina is made up of multiple layers of specialised neural cells and there is strong evidence that the same changes in the brain occur in the retina, potentially allowing screening patients for early signs of Alzheimer’s disease.’
While Alzheimer’s is not yet a disease which can be diagnosed via a routine eye examination, US biomedical engineers at Duke University have developed a new technique (so far tested only in mice) which could in future diagnose Alzheimer’s through retinal scans.
Their research, published in Scientific Reports, combines the results of 2 existing technologies to assess the condition of the retina – those with Alzheimer’s have a much rougher retinal surface.
Other recent US research has identified beta-amyloid plaques on the retina as an indication of Alzheimer’s (published in the International Journal of Molecular Science) and also in the lens of the eye (published in Experimental Eye Research) – both of which can be detected by non-invasive methods, and potentially facilitate easier and earlier Alzheimer’s diagnosis to enable treatment to begin before symptoms become severe.
