In the current field of nutrition and health, the microbiome represents a distinctive role as both a causative factor in chronic health conditions and a potential target for treatment.. Regarding connections to the eyes, studies have demonstrated distinct microbiome differences with subjects with autoimmune uveitis or age- related macular degeneration and their controls. The gut microbiota refers to the bacteria, fungi, archae, viruses, and protozoans present within the gut. It has been well established that this population of micro-organisms plays a fundamental role in digestion, nutrient and drug metabolism, vitamin synthesis, barrier function, antimicrobial immunity, and neurological functions.
The surge of recent research regarding the microbiome One of the largest studies initiated by the NIH common fund is the Human Microbiome Project (HMP). Within the human body, it is estimated that there are 10x as many microbial cells as human cells. It stands to reason that a disruption in the balance of this “genome” will adversely affect the human body’s ability to carry out its regular functions and enter into a diseased state. This state is referred to as dysbiosis. Obesity, inflammatory bowel disease, neurological conditions, irritable bowel syndrome are some examples of conditions that have been demonstrated to have a connection to altered gut microbiota, or dysbiosis.
More recently, researchers have drawn a link between dysbiosis and two ocular disease states – uveitis and age-related macular degeneration. This has also raised the additional question of whether there is a unique ocular microbiome. Uveitis is an inflammation of the uveal tract in the eye, and can include adjacent structures with estimated 10% to 15% of all cases of total blindness in the USA, typically from a sequelae of secondary complications such as cataracts, glaucoma, corneal, and retinal complications.
Uveitis is commonly associated with multiple autoimmune disorders particularly, inflammatory bowel disease (IBD), including ulcerative colitis and Crohn’s disease. Altered intestinal microbiota may modulate the immune system by Treg homing with possible developments in the eye.
Wet age-related macular degeneration
Wet age-related macular degeneration (AMD) accounts for most of the severe vision loss caused by AMD. It is the leading cause of vision loss amongst adults over the age of 60 with projections to grow by 2050. The Melbourne Collaborative Cohort Study associated early and late AMD in men with obesity. With every increase in 0.1 in waist/hip ratio, there was a 13% increase in early AMD and 75% increase in late AMD. Bacteroidetes is decreased in the obese as compared to lean individuals; the importance of the microbiome with regards to inflammation as well as basic metabolic function is;
The Ocular microbiome
We now know that there is a category of the ocular microbiome, distinct from the gut. The ocular microbiome is comprised of the cornea and conjunctiva, excluding the eyelids. There is the potential to link certain ocular surface imbalances to various ophthalmic diseases such as dry eye syndrome, contact lens complications and infection. A great deal of research is needed in this arena, but the potential benefits cannot be under-emphasized.
As personalized healthcare becomes more accessible and readily applied, the ocular conditions that have relations to not only distinct nutritional deficiencies but also microbiome deficiencies is paramount.