GLAUCOMA AND DES

Many glaucoma patients present with an ocular surface disease related to their therapy, in particular those using IOP-lowering medications containing the preservative benzalkonium chloride (BAK). This can directly affect their quality of life and compliance rates.

“In recent years, we have become more aware of the negative effects of BAK on the ocular surface, so we need to consider preservative-free glaucoma medications where possible in order to preserve the ocular surface and help contain the onset or worsening of this secondary condition in glaucoma patients,” Philippe Denis MD told the 2013 Congress of the European Society of Ophthalmology (SOE).

Dr Denis, Hopital de la Croix-Rousse, Lyon, France, noted that ocular surface disease is commonly associated with glaucoma.

“Both glaucoma and dry eye syndrome (DES) occur in older populations so it is not surprising that there is a clear overlap between the two conditions, with DES prevalent in glaucoma patients and vice versa. There is also a clear relationship between glaucoma eye drops and dry-eye symptoms, and glaucoma surgery may also be a risk factor for patients with DES,” he said.

The association between glaucoma and DES has been borne out by research in the scientific literature, said Dr Denis. One study by Leung et al in 2008 showed that a large proportion of patients (59 per cent) with open-angle glaucoma or ocular hypertension had signs and/or symptoms of ocular surface disease in at least one eye.

“Glaucoma is a chronic life-long condition and glaucoma and DES are often concomitant diseases. Ocular tolerability influences quality of life and adherence. Insufficient tolerability may lead to discontinuation of the glaucoma treatment and a lack of compliance, so the consequences are potentially very serious,” he said.

Focusing on BAK, Dr Denis noted that it is responsible for several components of poor ocular tolerability and worsening of dry eye symptoms.

“Studies have shown that topical anti- glaucoma eye drops containing BAK alter the conjunctival surface, with increased conjunctival inflammation and activation of macrophages, lymphocytes and mast cells, and an increase in the number of fibroblasts increasing connective tissue and conjunctival metaplasia,” said Dr Denis. BAK also has implications for glaucoma surgery, said Dr Denis.

“Bleb failure has been associated with increased conjunctival infiltration of fibroblasts and inflammatory cells. Long- term anti-glaucoma therapy is associated with increased rates of surgical failure, with the failure risk depending on the duration and number of treatments,” he said.

A study by Fukuda et al. comparing additives in anti-glaucoma prostaglandin ophthalmic formulations which compared symptoms of eye drops with and without BAK found significant differences between the medications, said Dr Denis. Symptoms such as red eye, burning, foreign body sensation, dryness and itching were all worse with medications containing BAK.

Another study by Jaenen et al also found that preserved eye drops showed much higher readings for anterior blepharitis, posterior blepharitis, eczema, conjunctival signs and hyperaemia than with non- preserved drops.

BAK toxicity is a rapid, cumulative, dose- related and chronic phenomenon, said Dr Denis. While BAK is also neurotoxic, a study by Sarkar et al suggests that discontinuing BAK exposure to the cornea may allow some nerves with disrupted axonal function to recover structurally.

“Therefore it is possible that discontinuation of BAK-preserved eye drops improves corneal function,” concluded Dr Denis.