Vitamin D and Ocular health
An overview of 125 clinical studies examined the association between diseases of the eye and vitamin D. “As many tissues in the eye are able to both activate and respond to vitamin D”, it was clearly established that vitamin D is “biologically relevant in the eye”.
Following is a brief overview of the eye problems that can be caused by vitamin D deficiency and/or treated with vitamin D supplementation.
Population studies have found that time spent outdoors protects against the development of myopia (nearsightedness), the thesis here being that the outdoors provides us with a source of vitamin D (via sunshine).
According to this study, low serum levels of vitamin D are more frequent in Asian and Middle Eastern populations. Among these populations, “darker skin coloration, higher latitudes, low sun exposure, age, and diet all contribute significantly to deficiency. Similarly, myopia development is associated with a range of both environmental and genetic components and rates are increasing worldwide, particularly in East and Southeast Asian populations. In total, data suggest a link between vitamin D status and myopia.”
Eye cancer is a terrible thing to contemplate, so it is encouraging that “vitamin D has been proven effective both in vitro and in animal models of retinoblastoma in inhibiting tumor cell growth”.
Age-related Macular Degeneration
Given our constant exposure to blue light (via smartphones, tablets, and monitors) macular degeneration is becoming more prevalent. Age-related macular degeneration (AMD) is, obviously, a form linked to the aging process, but I believe the value of vitamin D in this case would indicate that even younger people should ensure they have enough of this nutrient, in order to ward of the development of macular degeneration as they age.
One of the studies reviewed “importantly showed a genetic link between AMD prevalence and vitamin D metabolism”.
And, “mouse models suggest that vitamin D supplementation could be protective against both inflammation and angiogenesis in the retina, providing mechanisms of reduced vitamin D being involved in AMD development.”
Diabetic retinopathy (DR) is a complication of diabetes that causes damage to the blood vessels of the light-sensitive tissue at the back of the eye (retina).
“In an epidemiological study, Aksoy et al. (2000) found that serum vitamin D concentrations were inversely related to the severity of retinopathy in diabetic patients, with the lowest concentrations of the hormone measured in patients with proliferative DR.”
Uveitis is an inflammatory condition that affects the retina and the middle layer of the eye (uvea). This inflammation can be caused by an infectious agent or autoimmune conditions. “These studies provide evidence that vitamin D supplementation could be beneficial not only during the active inflammatory condition but also for prevention of uveitis as well.”
Ocular Surface Inflammation and Pathology
Inflammation in the eyes can lead to tissue damage and impairment of vision, thus anything that can protect the eyes during infection or injury will be of value. “Vitamin D therefore has the potential to reverse the harmful effects to the corneal epithelial barrier during infection and protect against inflammatory conditions.”
A Korean survey from 2014, “found a significant relationship between serum 25D3 (vitamin D3) levels and prevalence of OAG (open-angle glaucoma) with increased risk of disease particularly in participants in the lowest quintile of 25D3.”
Dry eye syndrome
“In a cross-sectional study examining male patients with dry eye syndrome, a condition that is accompanied by ocular surface inflammation, serum 25D3 levels were not found to be associated with severity of disease clinically, however, higher serum vitamin D levels were significantly correlated with a decrease in subjective dry eye symptoms.”
Here I will mention that vitamin A is also required for reversing dry eye syndrome.
Highlights of this study
Vitamin D deficiency is associated with development of various ocular pathologies.
Genetic variations in vitamin D pathways genes are associated with disease risk.
Ocular cells express vitamin D-related genes and can activate vitamin D.
Vitamin D treatment is protective in animal models of ocular disease.
In vitro studies suggest that vitamin D dampens inflammatory events in the eye. (Source)
Is there anything vitamin D can’t do? Well, considering it is involved in influencing around 200 genes, it is no surprise when we find yet another benefit (in this case, eye support) to ensuring we have more than adequate amounts of vitamin D in our bodies.