DRY EYE DISEASE is multifactorial, and the number of pharmaceutical options that target various aspects of this disease continues to increase, addressing ocular inflammation, tear film instability, and neurosensory mechanisms. Although these approaches can be effective, there are still elements of the dry eye cycle that need to be explored. In particular, the mucin component of the tear film is an area lacking in pharmaceutical options but ripe with therapeutic potential.

Mucins are the building blocks of mucus. The ocular structures that produce them include conjunctival goblet cells and the lacrimal gland, which secrete both gel-forming and soluble mucins and corneal and conjunctival epithelial cells that produce membrane-bound mucins responsible for the glycocalyx matrix that protects and helps spread secreted mucins across the ocular surface (Baudouin et al, 2019; Abelson et al, 2003). Mucus is a powerful lubricant that stabilizes and hydrates the tear film, reduces friction while blinking, and traps microbes and foreign material (Karpecki, 2022; Swamynathan and Wells, 2020).

Of particular importance are the secretory conjunctival goblet cells. Damage to these cells may come from many sources, including vitamin A deficiency, dry eye, inflammation, neurogenic insult, infection, topical medications, preservatives, trauma, and cicatrizing disease (Baudouin et al, 2019; Abelson et al, 2003). As a result, mucus can change in structure and/or volume. Clinical evidence of this varies; mucus may become thin, sticky, or stringy in dry eye disease; thick, purulent, and crusty in infectious conditions; and stretchy/ropy in vernal and giant papillary conjunctivitis (Abelson et al, 2003). Pathologic alterations in mucin structure can create a cycle by being both a cause and a consequence of ocular surface disease and dry eye (Baudouin et al, 2019; Karpecki, 2022).

Specifically related to dry eye, poor mucus quality and/or abnormal amounts can be problematic, and options superior to current mucomimetic lubricants are needed. Mucin deficiency can be treated with topical or oral secretagogues, although topical options are not currently available in the United States and oral options may cause undesirable systemic side effects (Shih et al, 2017). Other potential pharmaceutical options include rebamipide (currently approved as a mucosal protector for stomach ulcers and gastritis) and topical vitamin A (Baudouin et al, 2019).

Excessive amounts of poor-quality mucins can result in corneal filaments and mucus plaques, and damage to surface epithelial cells due to increased friction from blink-induced shear forces (Baudouin et al, 2019; Eghtedari et al, 2022). Studies have shown that  compounded N-acetylcysteine (NAC) can be useful in these cases because of its mucolytic, anti-inflammatory, and antioxidant properties (Baudouin et al, 2019; Eghtedari et all, 2022).

As understanding of the function of mucins in ocular surface disease evolves, pharmaceutical advances and options will likely emerge that help increase and improve mucin quality and quantity.

References

1. Baudouin C, Rolando M, Benitez Del Castillo JM, et al. Reconsidering the central role of mucins in dry eye and ocular surface diseases. Prog Retin Eye Res. 2019;71:68-87. doi: 10.1016/j.preteyeres.2018.11.007

2. Abelson M, Humphrey K, Dartt, D. Mucin: What you don’t know may help you. Rev Ophthalmol. 2003 January. Accessed November 12, 2025. https://www.reviewofophthalmology.com/article/mucin-what-you-dont-know-may-help-you

3. Karpecki P. A sticky subject. Rev Optom. 2022 Mar. Accessed November 12, 2025. https://www.reviewofoptometry.com/article/a-sticky-subject

4. Swamynathan SK, Wells A. Conjunctival goblet cells: ocular surface functions, disorders that affect them, and the potential for their regeneration. Ocul Surf. 2020;18(1):19-26. doi: 10.1016/j.jtos.2019.11.005

5. Shih KC, Lun CN, Jhanji V, Thong BY, Tong L. Systematic review of randomized controlled trials in the treatment of dry eye disease in Sjogren syndrome. J Inflamm (Lond). 2017;14:26. doi: 10.1186/s12950-017-0174-3

6. Eghtedari Y, Oh LJ, Girolamo ND, Watson SL. The role of topical N-acetylcysteine in ocular therapeutics. Surv Ophthalmol. 2022;67(2):608-622. doi: 10.1016/j.survophthal.2021.07.008