Dry eyes, medically known as keratoconjunctivitis sicca, occur when the eyes do not produce enough quality tears to maintain lubrication. While environmental factors or aging are common causes, a nutritional deficiency can also be significant. Understanding these underlying nutritional factors is important, especially since this cause is often overlooked.
Identifying the Nutritional Culprit
The nutritional deficiency most strongly linked to a severe form of dry eyes is a lack of Vitamin A. This condition, known as Vitamin A Deficiency (VAD), leads to the eye disease xerophthalmia, which translates to “dry eyes.” Xerophthalmia is the most serious nutritional connection to ocular surface disease.
VAD is a public health concern globally and a leading cause of preventable childhood blindness, predominantly in developing nations. Although rare in industrialized countries, Vitamin A’s role in maintaining the ocular surface remains fundamental.
How Vitamin A Maintains Eye Health
Vitamin A, specifically retinoic acid, plays a foundational role in maintaining the integrity and differentiation of epithelial tissues throughout the body, including the eyes. This nutrient is necessary for the health of the conjunctiva and the cornea.
Vitamin A supports the goblet cells within the conjunctiva, which produce mucin, a layer that helps tears adhere to the eye’s surface. Without adequate Vitamin A, the moist epithelial cells undergo a process called squamous metaplasia. This change causes the surface cells to transform into a drier, skin-like tissue that produces keratin.
This keratinization disrupts the tear film, leading to instability, poor lubrication, and the pathological dryness of xerophthalmia. The loss of mucin production further exacerbates the tear film breakdown.
Recognizing Severe Deficiency and Dietary Sources
The symptoms of severe Vitamin A deficiency progress through distinct stages. The earliest sign is night blindness (nyctalopia), which is difficulty seeing in low light conditions. As the deficiency worsens, dryness appears on the conjunctiva (conjunctival xerosis), followed by Bitot’s spots—distinctive, foamy patches of keratin debris on the whites of the eyes.
If VAD remains untreated, the corneal surface dries (corneal xerosis) and can soften (keratomalacia), potentially leading to corneal ulceration and irreversible blindness. Preventing this progression requires sufficient dietary intake of Vitamin A.
Preformed Vitamin A (retinoids) are found in animal products such as liver, eggs, and dairy. Provitamin A carotenoids, like beta-carotene, are found in vibrant orange and yellow vegetables, such as carrots and sweet potatoes, and dark green leafy vegetables. Supplementation with high-dose Vitamin A is an established public health measure in at-risk populations.
Other Causes of Dry Eye Syndrome
For the majority of people in industrialized countries, dry eye syndrome is not caused by a vitamin deficiency but by a variety of environmental and lifestyle factors. Increased tear evaporation is a common issue, often triggered by spending prolonged periods staring at computer screens, which reduces the natural blink rate.
Environmental conditions such as low humidity, wind, and exposure to smoke or air conditioning also contribute significantly to the problem. Certain common medications can reduce tear production as a side effect, including antihistamines, decongestants, some antidepressants, and blood pressure drugs.
Dry eye often becomes more common with age, particularly in postmenopausal women due to hormonal changes. Other underlying medical conditions, such as autoimmune disorders like Sjögren’s syndrome, rheumatoid arthritis, and thyroid problems, can also cause dry eyes. Because the causes are so varied, anyone experiencing persistent dry eye symptoms should consult a healthcare provider for a thorough examination and accurate diagnosis.