Immune System and Eyes

Overview

William Shakespeare refers to the eyes as the window to the soul, and this is not far from the truth because eyes arethe eye is the "middleman" between us and our immediate environment. 

The eyes are protected by several physical and biological defences, including eyelashes, the tear film (the layer of liquid that coats your eye when you blink), and conjunctiva (a membrane lining the whites of your eyes and inside of your eyelids). However, despite these protective measures, the eyes are still susceptible to infections and other damage due to their frequent contact with our environment through the ocular (eye) surface. This means preserving eye health requires a strong and healthy immune system. 

The immune system, which comprises organs like the skin, tissues like the bone marrow, and white blood cells such as B cells and T cells, protects us from invading viruses and other foreign bodies. One of the ways it does this is by activating a process known as an inflammatory response. This natural defence system causes tissue swelling and high temperatures in infected compromised individuals.

This article will discuss how the immune system and the eyes interrelate and how to boost immune cells and maintain eye health.

The relationship between the immune system and eyes

The human eye comprises a unique variety of cells, many of which are not found anywhere else in the body. The ocular surface is made up of the cornea (the transparent layer on the irises and pupils), conjunctiva, tear ducts, glands, as well as the eyelids, eyelashes, and more. These are connected by protective layers, and have interconnected blood vessels, nerves, and immune systems.¹

Two critical components of the eye required for normal vision are:

• the corneal endothelium, which moves water around the eye
• photoreceptors, which help convert light into signals in the brain

These tissues of the eye do not regenerate, and as a result, traumatic events like inflammation can cause damage to them, which could result in vision loss.

According to the National Eye Institute, our eyes have to protect themselves from various foreign bodies, also known as antigens, including:

• viruses and bacteria
• dust and debris
• ultraviolet radiation from the sun
• chemicals from everyday items such as soaps and lotions
• long exposure to computer screens or devices. 

Given all these potential causes of inflammation, parts of the eye essential for vision (the lens, cornea, and retina) have evolved immune privilege. Immune privilege means that the immune system in the eyes actually suppresses the inflammatory response when faced with these antigens. This also occurs in the brain and other organs with poor healing abilities.²

The relationship between the immune system and the eyes is dynamic and intricate, with the eyes containing a network of immune cells that secrete a variety of anti-inflammatory molecules. Certain types of eye cells can suppress T cells and other components of the immune system.³

How does the immune system affect our eyes

The immune system can affect our eyes both positively and negatively. Immune responses can be counterproductive when the eye's immune privileged status is jeopardised; the resulting disease can be fatal. When immune privilege fails, it results in several ocular conditions, including inflammation, pain, and vision problems.⁴

In autoimmune diseases, such as rheumatoid arthritis and lupus, the immune system produces antibodies that can mistakenly attack the eye and damage the optic nerve, leading to inflammation and other symptoms. Similarly, some viral infections, such as the herpes virus, can cause the immune system to attack the eyes, leading to conditions such as eye shingles or corneal ulcers.^3,5

Some common tests done to check for ocular surface diseases or vision impaired profile include:⁶

• observing eye movement
• tear break-up time (TBUT)
• tear secretion by the Schirmer's score
• fluorescein eye staining to detect corneal injuries
• meibomian gland dysfunction
• questionnaires to assess symptoms

Other less common tests include checking eye pressure, redness of the eye, corneal nerve density, autoimmune factors, appearance of theconjunctiva, pain assessment, and immune, nerve, and eye cell counts.⁶

In addition, the immune system can also play a role in the development of certain eye diseases, such as age-related macular degeneration (AMD) and cataracts. While the exact causes of these diseases are still not fully understood, researchers believe that inflammation influenced by the immune system may play a role.^1,4

Your healthcare provider may recommend eye drops or anti-inflammatory drugs for some common eye conditions that are caused by a weakened immune system, which include:

• conjunctivitis or pink eye
• double vision
• blurred vision

Other conditions include:

• thyroid eye disease (TED): An autoimmune eye disorder characterised by inflammation (swelling) and damage to the tissues surrounding the eye, which include muscles, fatty tissue, and connective tissue⁴

• microbial Keratitis: A condition that affects people with corneal transplants which can cause rejection or failure of the graft⁷

• dry eye: Recent data suggests that an increase in inflammatory immune cells is a key catalyst during the development of stress-induced dry eye¹

• uveitis: An ocular surface disorder, with the most common type being anterior uveitis. It causes pain, redness, and vision issues caused by inflammation of the uvea, the middle layer of the eye. However, uveitis may also be caused by other factors, including autoimmune diseases (autoimmune uveitis) and infections 

Ways to boost your immune system 

There are various ways to boost your immune system and help promote healthy immune cells, maintain immune privilege, eye health, and overall health. The most proven method to boost your immune system is to adopt and adhere to a healthy lifestyle because a poor diet can impair your immune system. A healthy lifestyle includes:

• eating foods that can boost your immune system, such as greens, nuts, and turmeric
• quitting smoking
• drinking little to no alcohol
• staying active by doing regular exercise
• staying hydrated
• getting enough sleep to prevent sleep deprivation and its adverse effects on the immune system
• managing stress by staying away from things and situations that cause anxiety. Stress may also cause tunnel vision
• practising top tier hygiene by washing your hands regularly, especially before and after using the bathroom or cooking, and staying away from anyone who shows symptoms of a contagious respiratory illness, such as the flu or COVID-19
• taking vitamins such as vitamin C, vitamin D, magnesium, zinc and other vitamins that help the eyes. You may also take supplements such as probiotics

Speak with your healthcare provider before starting a new exercise regimen or taking supplements, especially if you have a pre-existing health condition. You should also stop any new changes to your lifestyle or diet if you notice any side effects.

Summary

The immune system is critical in protecting the body from pathogens that cause infections and diseases, ensuring good health.However, inflammatory immune responses can be detrimental. The eye is immune-privileged organ. Several anti-inflammatory molecules, mechanisms, and barriers collaborate to suppress harmful immune activity and protect the eye. 

A strong and healthy immune system can help prevent the onset and progression of eye conditions caused by immunodeficiency or an autoimmune disease.

Adopting a healthy lifestyle, including exercising regularly, eating a healthy diet, practising good sleep hygiene, staying hydrated, and taking supplements can help to boost your immune system, promote healthy immune cells, and maintain ocular immune privilege.