Both ocular surface disease and glaucoma are more common in older patients, and first-line therapy for these disease entities are topical medications. They both have a spectrum of disease and severity but have compounding effects when coexistent. This interaction is further complicated by treatments for each condition which can interact and yield counterproductive effects.

Glaucoma treatment may cause chronic inflammation or aggravate a concomitant ocular surface disease.  Clinical trials of drugs most often test only one specific medication and preservative at a time, and often only for a short period of time. They do not test multiple or all classes of medications simultaneously for a prolonged period of time. However, in clinical practice patients with glaucoma are typically treated for many years or even decades.  Patients may also have preexisting ocular surface disease, dry eye, meibomian gland dysfunction, or chronic allergy and are very frequently treated with more than one topical glaucoma medication.  Some ocular surface issues can wax and wane while overall possibly worsening as we get older.  It is for these reasons that clinical practice does not always fit into the safety profile of typical clinical trials for medications.  There is still no standardized definition nor classification or assessment of glaucoma therapy related ocular surface disease.  Hollo et al. defined glaucoma therapy-related ocular surface disease well as, “imbalance of the ocular surface homeostasis caused by the toxic effect of chronic topical medication, which leads to tear film instability, epithelial damage, and inflammation. A recent study found a number of negative ocular surface markers associated with glaucomatous disease and treatment.