**1. Introduction**

Glaucoma is known to be a major cause of optic neuropathy that eventually leads to loss of vision. This is characterized by loss of retinal ganglion cells and their axons, excavated appearance of optic nerve head, and progressive loss of visual field sensitivities.

Quigley and colleagues published pooled-data analyses of glaucoma prevalence. In 2020, 80 millions of people are affected by glaucomatous optic neuropathy [1], of these, 60% will present concomitant ocular surface disease.

There is considerable evidence to suggest that medical treatment of glaucoma contributes to ocular surface disease (OSD) and the development of dry eye [2]; its prevalence with or without symptoms ranges from 5–50%, and the prevalence based on symptoms alone is very higher around 75% [3].

The cause of OSD in glaucoma patients is believed to be multifactorial and may include both the active component of the drug and the preservative, most commonly benzalkonium chloride (BAK), which is capable of causing inflammation and other anterior segment eye diseases that they range from allergy, blepharitis, dry eye, and anatomical eyelid abnormalities [3–5].
