The eye's primary function is to see, and in that role, all its parts form a single organ. However, it is frequently ignored that the ocular surface is also part of the overall body surface, which predominantly consists of skin. The eye with tear film protects itself from drying, and so does the skin for the rest of the body, which enables the body to retain its hydration. In that sense, both parts of the body surface perform the same task.
Dry eye is a medical problem of epidemic proportions. In the last three decades, awareness of dry eye disease (DED) has risen considerably worldwide. It is a growing public health concern causing ocular discomfort, fatigue, and visual disturbance that interferes with quality of life (QoL), including aspects of physical, social, psychological functioning, daily activities, and workplace productivity. According to the literature, the prevalence of dry eye ranges from 5 to 30 % in individuals over the age of 50, with women consistently having a 1,3 − 1,5 times higher prevalence rate than men in all studies that measured both signs and symptoms . On the other hand, dry skin (xerosis cutis) is the most common skin disorder, more frequently among women and older people, with prevalence ranging from 5.4 % to 85.5 % . DED is defined by Tear Film and Ocular Surface Society (TFOS) Dry Eye Workshop (DEWS) and amended by the TFOS DEWS II [3, 4].
At the same time, millions of people, especially women, complain of dry skin and use cosmetics to alleviate this discomfort. However, dry skin is not labeled as a disease, nor people who have it experience it as a disease but as a condition. It is characterized by a lack of the appropriate amount of water in the most superficial layer of the skin, the epidermis . It is not inflamed or diseased, just dry. Overall, there is a lack of reports describing it at all.
When eye care practitioners examine the dry eye patients and ask them about their skin type, very frequently, such patients also complain of having dry skin, especially women.
Having this in mind, is there a connection? Do people with dry skin also have dry eyes, and if they do, what may be the cause - the same for both parts of the body surface?
As Meibomian glands produce meibum, the skin's sebaceous glands produce an oily substance called sebum to protect the outer layer of skin from losing water. If the skin does not have enough sebum, it loses water and feels dry, like DED. The new definition recognizes dry eye as a multifactorial disease resulting from numerous interacting causes that influence tear film homeostasis, e.g., age, sex, gender, hormone imbalance, environmental causes, inflammation, neurogenic, iatrogenic, low blink rate, lid disorders, vitamin A deficiency, allergies and psychological causes [4, 6]. Many of them also result in dry skin. Aging decreases sebum production. Excessive bathing, showering, or scrubbing of the skin also excessively removes sebum. Dry indoor air, exposure to wind and sun, diabetes or skin allergies, thyroid gland disorders, Sjogren's syndrome, and various medications also cause the same condition . So, both conditions have much in common.
One of the most prominent DED and dry skin features is that both conditions occur more frequently in women than in men and older people. Moreover, the female gender by itself is a significant risk factor for the development of DED.
Sex hormones, especially androgens, are essential in regulating lacrimal, Meibomian, and sebaceous glands function, imbalance of which is associated with both aqueous-deficient, evaporative DED [8–11], and dry skin . Many other hormones, sex-related differences in brain organization, cognitive ability, and pain perception are responsible for dry eye sex-related prevalence differences and may play an important role in dry skin prevalence differences [13, 14].
Keeping in mind all the above mentioned, authors were surprised in not enabling to find any study comparing ocular and skin dryness.
The purpose of this study was to enquire whether patients with dry eye symptoms also report having dry skin and whether their perception could be corroborated with objective measurement. These answers could help DED diagnosing and treatment, and prevent disease complications that impact patients' vision, daily activities, QoL, and working abilities.