Humayoun Ashraf1 , Shamim Ahmad2 , Rupankar Sarkar3 , Syed Wajahat Ali Rizvi4
BACKGROUND Prostaglandin analogues (PGAs) have proven to be the most potent of the antiglaucoma medications in decreasing IOP, with little systemic side effects and hence are the initial treatment of choice. Many PGAs contain preservatives which are associated with increased ocular side effects, the most common preservative being benzalkonium chloride (BAK). BAK is known to cause cell toxicity and cell death in ocular surface tissues in a dose-dependent and time-dependent manner and often gives rise to ocular surface diseases, with the consequence of dysfunctional tear film in patients who are on long-term PGA therapy. We wanted to evaluate the long-term effects of prostaglandin analogue eye drops with and without preservative on tear film stability in glaucoma patients who are instilling these medications on a long-term basis. METHODS This is a prospective study conducted on 48 eyes from 48 patients of glaucoma and 30 eyes from 30 controls. Patients who were newly diagnosed to have glaucoma were started on either of the two eye drops: Tovaxo (Travoprost 0.004%, preservative-free) and 9PM (Latanoprost 0.005%, BAK 0.02%). The patients were followed up for one year at the end of which period Tear break up times (TBUT) were measured and Schirmer’s tests were performed. RESULTS In preservative-free travoprost group 62.5% patients had TBUT between 6 and 10 seconds while BAK-preserved latanoprost group had 79.2% patients with TBUT between 6 and 10 seconds. 8.3% of patients in BAK-preserved latanoprost group had TBUT ≤5. The rest of the patients had normal TBUT (>10 seconds). 76.7% of the controls had a normal TBUT. None of the subjects in control and travoprost group had TBUT of 5 seconds or less. All patients in the travoprost group and all the controls had Schirmer test result >10 seconds while 91.7% of the patients in latanoprost group had TBUT >10 seconds. The intergroup difference was not statistically significant. CONCLUSIONS Long term instillation of prostaglandin analogues can be associated with tear film instability. BAK-preserved drugs may have a greater deleterious effect on the tear film than preservative-free drugs.
