Tear Film Osmolarity, Ocular Surface Disease and Glaucoma: A Review

Abstract

Glaucoma is the second leading cause of blindness in the world, affecting more than 60 million people globally. In order to reduce the progression of the disease, both medical and surgical treatments are used. Frequent side effects of both treatments include a range of modifications of the ocular surface grouped as the Ocular Surface Disease (OSD), which include Dry Eye Disease (DED). DED and other OSD negatively impact on the success of anti-glaucoma treatments and reduce the adherence to medical therapies. Tear film osmolarity (TFO) is a relatively novel test which has become a hallmark of DED. The aim of this paper was to review the association between OSD, DED and glaucoma in view of published TFO data, and to discuss future fields of research and treatments on the topic of glaucoma iatrogenic damage.

Evaluation of lacrimal drainage system in Pseudoexfoliation syndrome

“…Hyperosmolar stress caused by loss of goblet cells and tear film instability promotes and maintains the local ocular inflammatory process [ 5 , 13 – 26 ]. Tear osmolarity is considered the critical pathogenic factor that causes ocular surface inflammation, and hyperosmolarity is known to stimulate the production of inflammatory cytokines in tears and conjunctiva [ 26 – 28 ]. Considering the punctum is the entry point for tears and is close to the conjunctiva, it could be assumed that prolonged ocular surface inflammation caused by PXF accumulation may play a pathogenic role in the development of punctal stenosis.…”

Changes in peri‑ocular anatomy and physiology in pseudoexfoliation syndrome (Review)

“…Growing evidence has suggested that PEX may also be involved through combined pathological effects on all layers, including the tear film, corneal and conjunctival epithelium, as well as eyelid apposition to the eyeball (38). PEX has been reported to be implicated in OSD by several previous studies (40,42). Of note, PEX has been reported to compromise both the quality and quantity of the tear film, as indicated by the defective Schirmer, tear break-up time and tear osmolarity tests (42)(43)(44)(45), as well as defective conjunctival goblet cell activity (46), contributing to the development of DED.…”

“…As in the case of eyelid skin and tendinous anatomical elements of the peri-ocular area, the conjunctiva has also been reported to be affected in PEX, resulting in conjunctival chalasis (39) and subsequent development or deterioration of pre-existing ocular surface disease (OSD). The latter is a chronic malfunction of the physiological elements, contributing to the effectiveness of the ocular surface in supporting eyeball integrity and preserving visual function (40). It has been associated with several pathogenetic mechanisms, including Dry Eye Disease (DED), drug toxicity, particularly from anti-glaucomatous medications, and viral infections, such as the human papillomavirus (40,41).…”

“…The latter is a chronic malfunction of the physiological elements, contributing to the effectiveness of the ocular surface in supporting eyeball integrity and preserving visual function (40). It has been associated with several pathogenetic mechanisms, including Dry Eye Disease (DED), drug toxicity, particularly from anti-glaucomatous medications, and viral infections, such as the human papillomavirus (40,41). Growing evidence has suggested that PEX may also be involved through combined pathological effects on all layers, including the tear film, corneal and conjunctival epithelium, as well as eyelid apposition to the eyeball (38).…”

Mitochondrial Dysfunctions May Be One of the Major Causative Factors Underlying Detrimental Effects of Benzalkonium Chloride

“…Although BAC provides excellent antimicrobial properties in ophthalmic preparations, a large number of clinical and experimental investigations using in vitro or animal models suggested cytotoxic effects of even low BAC concentrations on several components of the eye (see [18]). The topical administration of BAC-containing eye drops may cause a variety of ocular surface changes, from ocular discomfort, redness, dryness, and tear film instability [19][20][21][22][23][24][25][26] to allergic, immune, inflammatory reactions [27][28][29], ocular irritation, scarring of the ocular surface with irreversible vision impairment [21,30,31], disruption of the blood-aqueous barrier inducing cystoid macular edema following cataract surgery [32,33], loss of goblet cells (see [27,34]) and, at higher concentrations, to the disruption of the corneal epithelium, induction of apoptosis or necrosis of Chang's conjunctival cells [31-33, 35, 36]. The proapoptotic effects were seen at very low concentrations of BAC with a threshold of toxicity found at about 0.005% (i.e., below the usual concentration used in most eye drops).…”