From the perspective of modern medicine, dry eye syndrome develops when the tear film becomes unstable or tear production decreases. Beyond a simple lack of tears, the balance among the three layers of the tear film—the lipid layer, aqueous layer, and mucus layer—is frequently disrupted, causing tears to evaporate too rapidly. The concept of internal water in the Donguibogam corresponds closely to the modern medical understanding of body fluids and fluid metabolism. In the body, fluid metabolism is carefully regulated by the autonomic nervous system and the endocrine system. Psychological stress, sleep deprivation, and prolonged screen time overstimulate the sympathetic nerve and constrict blood vessels, which reduces blood flow to the lacrimal gland and impairs tear secretion. Lacrimal gland function is also influenced by sex hormones; women, in particular, often experience worsening dry eye syndrome as estrogen levels decline during menopause. This mirrors the view in the Donguibogam that a decline in the essence qi of the kidney depletes yin fluid throughout the body, eventually drying the eyes, as the kidney plays a vital role in reproduction and hormone metabolism.
Furthermore, tear film stability depends heavily on the meibomian glands, which are specialized sebaceous glands along the eyelid margins. The lipid secretions from these glands form the outer protective layer of the tear film to prevent evaporation. When these glands malfunction, tears evaporate quickly regardless of how much fluid the eyes produce. In modern life, external and internal factors—such as fine dust, contact lens use, and certain medications—interact to disrupt tear film homeostasis. Extended exposure to blue light reduces blinking frequency, leading to decreased tear distribution and potential damage to the ocular surface. Over time, this compounding strain increases eye fatigue, lowers visual acuity, and can even cause damage to the cornea. Artificial tears alone cannot fully resolve this state. Preserving long-term eye moisture requires supporting overall systemic health through stress reduction, adequate rest, and balanced hormone metabolism.
