Dry eyes due to "lack of water"? Actually it's "lack of oil"!

"My eyes are dry and itchy, and eye drops don't help"

"When I blink, I feel a foreign body sensation, like being pricked by a needle"

"My eyes feel tired and sore after staring at electronic products for a while"

…

In the era of screen reading, I believe everyone has experienced the above experience more or less. According to the "Chinese Dry Eye Expert Consensus (2020)", the number of dry eye patients in China has actually exceeded 360 million, with an average of one in four people suffering from dry eye. Dry eye has gradually become a chronic high-incidence disease exclusive to modern people.

Although common, it is by no means simple. Once you suffer from dry eyes, it is not enough to just use eye drops to relieve or improve the symptoms. Some difficult dry eyes, such as severe meibomian gland deficiency, cannot be left alone. Severe dry eyes can cause corneal ulcers or even perforations, and even lead to blindness.

In addition to the characteristic dry eyes, dry eyes also have symptoms such as burning sensation, foreign body sensation, visual fatigue, red and stinging eyes, and increased secretions. There are many factors that cause dry eyes, including systemic factors such as diabetes, menopausal syndrome, gout, and local causes such as eye infection mites; urban people's long-term "screen reading", staying in air-conditioned rooms, wearing contact lenses, cosmetic lenses, and long-term high-sugar and high-fat diets, etc., can all lead to the occurrence of dry eyes.

According to relevant research, about 70% of dry eye patients have lipid abnormality dry eye [1], and the main cause of the disease is meibomian gland dysfunction (MGD) [2]. In other words, the "dryness" of dry eyes is not due to "lack of water" but "lack of oil". The lipids secreted by the meibomian glands, commonly known as "oil", adhere to our cornea and play a role in "locking in moisture and moisturizing" and preventing excessive evaporation of tears. Once the lipid secretion ducts, that is, the meibomian glands, are blocked, the "oil" cannot be secreted, and the water-locking function will be destroyed, resulting in dry eye surface.

Therefore, the "dryness" of dry eyes is actually more about "lack of oil" than "lack of water".

References:
【1】Chinese Journal of Experimental Ophthalmology, 2022, 40(2): 97-103. DOI: 10.3760/cma.j.cn115989-20211015-00563.

【2】 Lemp Michael A, Crews Leslie A, Bron Anthony J et al. Distribution of aqueous-deficient and evaporative dry eye in a clinic-based patient cohort: a retrospective study.[J] .Cornea, 2012, 31: 472-8.