Vitamin A and OSD: the Good, the Bad, and the Ugly
Understand the therapeutic benefits and potential adverse effects associated with products containing vitamin A derivatives.
Kaleb Abbott, OD, MS, FAAO
Modern Optometry
The significance of vitamins for maintaining ocular health cannot be overstated. Vitamin A, in particular, takes center stage in the context of dry eye disease (DED); however, its exact role in ocular surface disease (OSD) is a subject of controversy due to conflicting evidence of its benefits and potential harmful effects. This article delves into the intricate relationship between vitamin A and DED and discusses various derivatives of vitamin A, including their mechanisms, therapeutic potential, and inherent risks. VITAMIN A: THE BASIC FACTS Vitamin A is a fat-soluble vitamin that supports immunity, growth and development, reproduction, gene transcription, cell differentiation and proliferation, epithelial cell health, and mucous membrane integrity.1 Tissues requiring vitamin A, such as the liver and the lacrimal gland, may store it as retinyl esters.2,3 Vitamin A deficiency remains a global issue, affecting approximately one-third of children worldwide and leading to blindness in 250,000 to 500,000 cases each year.4,5 However, in the United States, vitamin A deficiency affects only about 0.3% of the population, typically occurring in individuals with substance abuse or malabsorption issues.6 Vitamin A deficiency can result in the loss of goblet cells, increased epidermal keratinization, and squamous metaplasia of mucous membranes, including the conjunctiva,7,8 so it is crucial to consume a sufficient amount to support ocular health. Signs of vitamin A deficiency include night blindness, ocular surface dryness, dry skin, Bitot spots, frequent infections, and other skin problems.9 Dairy products, eggs, fish, meat, liver, leafy greens, carrots, and sweet potatoes are excellent sources of vitamin A.10 With respect to vision, vitamin A plays a pivotal role in transforming photons into electrical signals through a process known as phototransduction.11 Vitamin A also exerts significant effects on goblet cells, corneal epithelial cells, tear film stability, and meibomian gland health. VITAMIN A and OSD The relationship between vitamin A and OSD is complex. On one hand, deficiency is detrimental to ocular surface health, and oral and topical supplementation has proven effective at improving the signs and symptoms of OSD.12,13 On the other hand, more potent derivatives can cause significant meibomian gland damage. Similarly, certain facial creams containing such potent derivatives, such as isotretinoin, may pose a risk to meibomian glands; patients should be advised not to use these products near their eyelids.14 As with any nutrient, moderation is key. It’s essential to recognize that because vitamin A is a fat-soluble vitamin, toxicity is a possibility. Oral supplementation should generally be recommended only in cases of known deficiency, as toxicity is more common than deficiency in the United States.6 However, for patients suspected of mucin deficiency, meibomian gland hyperkeratinization, or aqueous deficiency, an ointment containing a mild vitamin A derivative may prove beneficial.