Association of poor eyedrop instillation technique and faster rate of visual field progression in patients under chronic glaucoma medical therapy

Abstract

Purpose: To study the association of eyedrop instillation technique and previous rate of visual field progression (VFP) in patients under chronic glaucoma medical therapy.

Methods: We conducted a retrospective review of visual fields (VF) from patients that participated in a randomized controlled trial (RCT) comparing success of 2 eyedrop instillation techniques (NCT01417689). All participants were on chronic (>= 1 year), bilateral ocular hypotensive therapy. Eligibility criteria included >= 6 previous VFs at the time of enrollment and having non-missing data for the baseline evaluation of the RCT. After censoring the first 2 VFs to reduce noise induced by learning, VFP was estimated using linear regression to estimate the the slope of Mean Deviation in dB/year. The variables correlated with rate of VFP were: Total success, defined as getting the drop in the eye using only one eyedrop; and number of eyedrops spent during instillation dichotomized using different cut-offs. Given that most of the patients had 2 eligible eyes, generalized estimating equations were used to estimate the associations.

Results: The 228 patients enrolled in the RCT had data for baseline eyedrop instillation evaluation of which 134 patients (239 eyes) had >=6 previous VFs. Mean age (sd) was 73.9 (7.5) years, 58% were women. Included eyes had a mean (sd) of 9.8 (SD 2.3) previous exams. While 99% of the eyes managed to get a drop in the eye, only 164 (69%) did so spending only one drop (Total success). Patients that achieved total success at baseline had a mean rate of VFP of -0.52dB/year versus -0.67 dB/year in those that did not. (p=0.12). For the association of number of drops spent to VFP, the cutoff that achieved the greatest contrast and significance was >=3 drops spent. The 24 eyes (10%) that spent 3 or more drops had a mean rate of progression of 0.91dB/year while those that spent <3 drops had a mean rate of VFP of 0.52 dB/year. (p=0.05)

Conclusions: Our data suggests that patients spending more drops per instillation attempt might be at risk of progressing faster. This association could be mediated by decreased adherence and needs confirmation in prospective studies.

Keywords: 579 learning • 758 visual fields • 669 quality of life