For which types of patients do you recommend preservative-free?
In my practice, there are 4 very clear indications for preservative-free treatment. The first is patients with symptoms and signs of ocular surface disease (OSD) or dry eye disease (DED). In these patients, the ocular surface is already damaged and inflamed. Adding preservative to this stimulates further cell death and tear film instability this driving the vicious cycle of OSD/DED rather than correcting it. The use of preserved eyedrops in this patient population simply does more harm than good. The second indication is post-surgery, especially refractive surgery. I would go so far as to state that all post-operative eyedrops regardless of the type of eye surgery should be preservative-free. We know that laser vision correction causes a temporary neurotrophic effect and secondary DED. To administer frequent doses of preservative in this situation is a recipe for exacerbating the signs and symptoms of tear film instability and ocular surface damage. In refractive surgery, patient satisfaction is everything and preservatives lead to unhappy patients.
Switching to preservative free treatment is an excellent way of reducing the chance of unhappy patients. This also applies to older patients undergoing cataract surgery. As the ocular surface ages, the incidence of the OSD/DED increases. In addition, the ocular surface of older patients is more prone to preservative induced toxicity and is more sensitive to dessicative stress and subsequent inflammation post-surgery. Preservative toxicity post-surgery is very common in elderly patients and therefore preservative free treatment post cataract surgery in this group of patients is essential in my practice.
The third indication is glaucoma. Glaucoma patients are exposed to low to medium doses of preservatives for long periods. Whilst this is rarely problematic in the short term, the accumulation of preservative in the ocular surface, trabeculum, lens and choroid eventually leads to toxicity and immuno-allergic reactions and inflammation. The fact that inflammation is bad for glaucoma patients and in particular, the outcome of surgical interventions for glaucoma is universally accepted. There is a substantial body of evidence linking pre-operative preservative and the inflammation it induced to poor surgical outcomes.
Therefore, glaucoma patients who display signs of ocular surface disease or glaucoma patients who may require subsequent surgical intervention should be treated with preservative free drops.
The final indication for preservative free eyedrops is patients undergoing any form of corneal transplantation. Preservatives prime the immune system, induce conjunctival inflammation and cause dendritic cell infiltration of the conjunctiva and cornea. All of these are undesirable in corneal transplantation as they increase the likelihood of corneal allograft recognition and rejection.
Do you explain to your patients the interest of preservative-free?
Given that the typical patients in my practice are in one of the above four categories I always emphasise the importance of preservative-free medication in their treatment. The healing of the ocular surface is such a slow and delicate process that there is no place for preservatives in these patient groups and I insist that patients source the correct preservative-free formulations of their medicines and are not diverted to preserved alternatives.
Do you consider, before prescribing a product, the deleterious effects from preservatives?
As I have explained above there is a very substantial and evidence based scientific rationale for using preservative free medication in the patients I treat. Preservative stimulates apoptosis of the ocular surface cells and induces inflammation. This drives the vicious cycle of OSD / DED and leads to medication doing more harm than good. In patients who have any form of tear film instability, DED, OSD or ocular surface inflammation secondary to surgery the use of preservative is simply counterproductive.