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Glaucoma Section Heading Section sub Evaluation of Ocular Surface Disease Associated with Glaucoma Patients Nilay Yuksel Specialist in Ophthalmology, Kahramanmaras Necip Fazil City Hospital, Kahramanmaras, Turkey Abstract The relationship between glaucoma medications and ocular surface disease (OSD) has been investigated for a long time by ophthalmologists. It has been well known that all preservatives used in topical medications have the potential to cause corneal and conjunctival changes, including dry eye. It is important to also consider the toxicity of the active ingredients. Objective tests for evaluating OSD are the Schirmer Test, Tear Break Up Time (TBUT), Fluorescein Clearance Test (FCT), impression cytology, confocal microscopy – the most common subjective test is Ocular Surface Disease Index (OSDI). Adverse effects associated with topical medication may have a negative effect on patient adherence to medical treatment, the patient’s life quality and the doctor–patient relationship. A favourable adherence to treatment will lead to more effective intraocular pressure (IOP) lowering and resultant decrease of glaucomatous vision loss. Keywords Glaucoma medications, ocular surface disease, ophthalmic preservatives Disclosure: The author has no conflicts of interest to declare. Received: 7 October 2013 Accepted: 28 October 2013 Citation: European Ophthalmic Review, 2013;7(2):81–3 Correspondence: Nilay Yuksel, Gaziantep Yolu 14 Km Karacasu Mevkii Merkez, Kahramanmaras, Turkey. E: ozturk.nilay@gmail.com Ocular surface disease (OSD) is an umbrella term that includes both dry eye and non-dry eye disease (e.g. lid disease, conjunctivitis and keratitis). 1 OSD can severely and negatively affect visual function, the ability to perform daily tasks, such as reading, watching TV and driving. Symptoms may include dryness, irritation, tearing, photophobia, foreign body sensation, grittiness, itching, burning, blurry vision, discomfort or pain, redness and, in severe cases, blindness due to corneal scarring. 2,3 Glaucoma is a group of diseases that damage the optic nerve and can result in vision loss and blindness. Topical intraocular pressure (IOP)-lowering medication is the initial option in the treatment of glaucoma. 4 Patients with glaucoma and ocular hypertension have been shown to suffer OSD at a higher prevalence rate than patients without these ocular disorders. 5 Development of OSD resulting in dry eye may cause discontinuation and poor adherence with glaucoma treatment, 6,7 and it can cause irreversible vision loss due to glaucomatous optic nerve damage. Wong et al. compared tear protein profile in patients receiving long-term glaucoma medication and in those with primary dry eye. They suggested that duration of use of anti-glaucoma medications longer than 1 year might start to induce changes in ocular surface inflammation. 8 Jaenen et al. evaluated 9,658 patients who were on anti-glaucoma treatment in a multicentre cross-sectional epidemiological survey in four European countries. 9 When they compared preservative-free eyedrops with preserved eyedrops, the former were significantly less associated with ocular symptoms and signs of irritation. © To u ch MEd i ca l MEd ia 2013 Ophthalmic Preservatives All preservatives used in topical medications have the potential to cause corneal and conjunctival changes, including dry eye. Most of the IOP-lowering agents contain the preservative benzalkoniumchloride (BAK). BAK is a quaternary ammonium compound that is used to inhibit microbial growth in the bottle. It disrupts cell membranes, increases membrane permeability and causes cell death. 10 After instillation, eye drops interact with ocular surface tissues. 11 Several studies showed that BAK has also a toxic effect on the corneal epithelium as well as conjunctival epithelium and stroma, and therefore can trigger or exacerbate OSD. 12–14 In animal models, BAK-free travoprost 0.004 % did not affect goblet cell numbers 15 or corneal epithelial cells, 16,17 whereas BAK-preserved latanoprost 0.005 % was shown to cause losses of goblet cells 15 and pathological changes in the corneal epithelium. 16,17 Studies have also shown that preservative-free drugs caused less ocular toxicity and damage to ocular surface compared with preserved drugs. 18–20 Other studies have shown that BAK does not have important negative effects on cornea. 21–24 Alternative oxidising preservatives agents have been developed, such as sofZia™ (Alcon Laboratories), which contains borate, zinc and sorbitol. These oxidising agents may cause less cell damage than detergent preservatives such as BAK. 25 Also Purite is an oxidative preservative that is used in brimonidine and artificial tears. 26 In a study by Katz et al., brimonidin-purite 0.15  % showed the most favourable safety and tolerability profile with a reduced incidence of allergic conjunctivitis and better satisfaction and comfort rating. 27 Polyquad ® is an another alternative polycationic preservative. Labbe et al. showed that Polyquad causes less toxicity than BAK in vivo. 28 81