Prof. Jennifer P. Craig
Professor and Founder of Ocular Surface Laboratory
BSc (Hons) MSc (Cataract & Refractive Surgery) PhD FCOptom FAAO FBCLA FACLS
Department of Ophthalmology
New Zealand National Eye Centre
The University of Auckland
Excerpts from Prof Jennifer P. Craig’s presentation at the Glaucoma NZ Professional Symposium in Auckland on 16th May 2021.
Studies suggest that 40-50% of glaucoma patients have dry eye syndrome. Dry eye syndrome becomes more common with aging and women are more likely than men to have it. People with glaucoma are at higher risk of dry eye because some glaucoma treatments can worsen the ocular surface and increase a tendency to dry eye.
Glaucoma therapy frequently requires decades of topical IOP-lowering medications. Preserved prostaglandin monotherapy is often the first step, and when this proves insufficient, combined preserved therapy follows, with multiple agents added until the desired target pressure is reached. Almost half of glaucoma patients worldwide receive more than one topical medication, and chronic, progressive ocular surface disease is not uncommon, affecting the majority of glaucoma patients.
The topical medications used to treat glaucoma can have allergic, toxic and/or immuno-inﬂammatory effects, sometimes as a result of a pro-inflammatory active ingredient (e.g. prostaglandin analogue), or more commonly, from the preservatives and excipients. Chemical interactions can be highly disruptive to all layers of the preocular tear film through direct effects on the film itself or indirectly by impacting the glands that produce the various tear components.
The most major culprit is recognised to be the quaternary ammonium preservative, benzalkonium chloride (BAK), a highly hydro-soluble bipolar surfactant that dissolves lipids and destroys bacterial walls and cell membranes. This damages the goblet cells of the conjunctiva and triggers the vicious circle of dry eye disease, resulting in a self-perpetuating cycle of tear film instability, hyperosmolarity, cellular damage and inflammation, accompanied by marked symptoms. This iatrogenic dry eye adversely affects quality of life, impacts patient compliance with therapy and reduces long term therapeutic success.
Iatrogenicity is just one cause of dry eye disease, but dry eye is a common problem, and many patients with glaucoma will have pre-existing ocular surface disease or other dry eye risk factors. Taking a holistic view is important in successfully managing patients, in order to break the vicious circle of dry eye disease and restore tear film homeostasis. It’s vital to avoid preserved lubricants in order not to exacerbate any preservative-toxicity, and careful attention should be paid to co-morbidities, particularly lid disease so that these can be managed accordingly. Educate patients to encourage application of home-based therapies, and offer advice about in-office treatments that might improve meibomian gland function to augment the lipid layer and improve tear film stability.
A multifaceted approach is usually required to manage dry eye in patients with glaucoma. Avoiding, or at least minimising, preservatives is key. Research shows that use of preservative-free glaucoma drops improves the quality of the ocular surface, without a reduction in pressure-lowering effect. Across the developed world, the use of preservative-free anti-glaucoma drops is thus growing, but costs remain higher than for preserved drops.
Where preservative-free options are not available, or affordable, efforts need to be made to minimise the application of drops as the preservative effect is cumulative. This might be achieved by using a drop that requires less frequent instillation. Where multiple medications are needed to achieve the target pressure, combination drops can halve the amount of preservative instilled compared with application of the same two active ingredients individually.
Products that contain less harmful ‘disappearing’ preservatives than BAK, such as Polyquad® or Purite®, which break down into non-harmful by-products on instillation, may be better tolerated by the ocular surface. Surgical (e.g. MIGS) or laser (e.g SLT) treatments as options for pressure-lowering can also reduce the dependency on topical therapy, protecting the ocular surface over the longer term.
Aim to minimise the impact of glaucoma treatments on the ocular surface, utilise the increasing range of therapeutic strategies available for dry eye to restore tear film homeostasis and optimise ocular surface health.