We all understand that our eyes are essential for normal life and well-being. Human beings are essentially visual animals and 70% of sensory input from the world around us is through our eyes.

In addition, our eyes are also windows to our inner world of thoughts and feelings and emotions, whether happiness, sadness, grief, anxiety, fear, or anger can be read by watching someone’ face, particularly the eyes. This has immense importance in everyday communication and social interaction.

In addition to these aspects, our eyes are accessible portals that permit us doctors to look into them with a view to finding out about various diseases affecting the person. Diabetes mellitus, which is poorly controlled diabetes results in damage to many organs in the body. One important area affected is the eye.  Diabetic retinopathy is the damage that occurs to the retinal tissue which lines the inside of the eye. The health of retinal tissues can be observed, documented using fundus photographs, and studied layer by layer using tools like optical coherence tomography. Retinal damage due to prolonged high sugars in the blood results in very early findings called micro aneurysms and with further damage, leads to further damage in stages leading up to advanced diabetic disease which may include bleeding into the eye and even to retinal detachment. This damage does not happen suddenly and gives us healthcare professionals ample time to detect and treat in a way that preserves vision. Hence it is recommended that all diabetics undergo a detailed ophthalmic examination once at the time of diagnosis of the disease, and every year thereafter to detect any changes early, and to successfully treat and arrest the progression of diabetic retinopathy. 

Systemic hypertension or high blood pressure is another common ailment. The eye retinal examination can reveal subtle changes including narrowing of the arteries and areas of bleeding in the retina. In the most severe uncontrolled cases which we call as malignant hypertension there can be swelling of the eye nerve in both eyes which is called disc oedema. This is a medical emergency and patients with such severe disease often need admission and aggressive management to prevent heart, kidney, and brain damage. Examination of the eyes at regular intervals is recommended particularly if the person has poorly controlled blood pressure. 

 Another relatively common systemic disease results from overactivity of the thyroid gland, a condition called hyperthyroidism. This results in bulgy eyes, a staring appearance, incomplete eye closure, and raised pressure on the eyeball and eye nerve, even resulting in loss of vision in one or both eyes. These patients need close monitoring with tight control of   thyroid gland function. Steroid medication given by mouth or as injections are a mainstay of eye treatment in addition to lubricant eye drops. Surgery is needed in more severe disease.

In addition to these non -communicable diseases, infectious diseases like tuberculosis show findings within the eye which can be easily detected by meticulous examination. Such findings help guide not only the treatment of the eye condition but also of the underlying tuberculosis infection. Systemic infections due to bacteria, viruses, fungal infections like black fungus, and even worm infestations result in eye changes and prove invaluable in timely diagnosis especially when clues elsewhere in the body are inconclusive. 

 Eye examination also provides distinct clues to numerous neurological diseases. These findings provide pointers to neurological conditions like Parkinsonism, brain tumours, multiple sclerosis, stroke, and raised pressure within the brain tissues among other conditions. In addition, conditions affecting the peripheral nerves like myasthenia gravis often present first to the ophthalmologist with complaints like double vision or eyelid droop.

The eyes, in addition, also provide clues to numerous other diseases affecting every organ in the body, and also to drug toxicity due to a variety of medications. Cutting -edge ophthalmic investigative tools supplement clinical examination techniques and help the ophthalmologist in making precise diagnoses.