Do adherence rates and glaucomatous visual field progression correlate?

Purpose. To assess the relation between visual field progression and adherence rate in patients with glaucoma using Travatan Dosing Aid® (TDA). Methods. In this 36-month retrospective study, 35 patients with primary open-angle glaucoma on travoprost or travoprost/timolol fixed combination monotherapy were submitted to ophthalmic examination and to visual field (VF) test from 2007 to 2009. Adherence was recorded with TDA. The association between VF progression (from 2007 to the end of the follow-up period) and a number of predictors (adherence rates at 12 months) was tested by means of chi-square test (or Fisher exact test) or Mann-Whitney test as appropriate. Results. The mean (±SD) adherence rates were 71.9\%±27.8\% after 1 month of follow-up and 76.8\%±20.9\% at 12 months. A total of 25 (71.4\%) patients with stable VF had a median adherence rate (IQR) of 85\% (75\%-97\%); patients who worsened (n=10; 28.6\%) recorded a median (IQR) adherence of 21\% (9\%-45\%) (p<0.001). No association was found between VF progression and any of the other variables (age, sex, schooling, visual acuity, intraocular pressure (IOP) at baseline and over time, other ocular diseases, time since diagnosis and actual therapy, number of concomitant systemic therapies). Patients who were at least 90\% adherent did not progress, while 43.5\% of the patients with lower adherence worsened (p=0.01). Conclusions. Our data suggest that adherence rate may play a role in glaucomatous damage and/or progression; the target IOP therefore should be adjusted by adherence rates. Monitoring tools, educational programs, use of videos, a better doctor-patient relationship, or other means to improve adherence are desirable and necessary to preserve visual function.