Background: Noncompliance can mislead clinicians regarding the efficacy of therapy and result in more aggressive, but inappropriate treatment. Improper techniques used for eye drop instillation frequently occurs in chronic glaucoma patients. The Thai Eye Drop Guide (EDG) device has been developed to ensure precise instillation. However, whether the EDG is more effective than the traditional technique when careful instructions for both techniques are given is still unknown.

Objective: To compare success rates of eye drop self-instillation by chronic glaucoma patients using a traditional technique and the EDG when careful instructions for both are given.

Methods: Fifty-nine chronic glaucoma patients were instructed to instill eye drops using the EDG or a traditional technique in a randomized sequence. A two week practice period was assigned before groups were crossed-over. The instillation performance was VDO recorded after each practice period. Three criteria of success: time taken to instill an eye drop into the eye; instillation of only one drop; and without the bottle tip touching lids, lashes, periocular tissues, or the other hand, were scored by three independent readers from video-records. The readers were blinded to the sequence to which the patients were randomized.

Results: There were no significant differences in success rates between the EDG and traditional technique (61.0% and 66.1% respectively, p = 0.607) and the number of drops dispensed per application (median of 1 drop in both groups, p = 0.89). The time taken to instill eye drops with the EDG was significantly longer than using the traditional technique (median of 19 and 9 s respectively, p < 0.001). Older age (p = 0.049, OR 4.23) and more education (p = 0.025, OR 0.19) were found to be significantly associated with failure of the EDG.

Conclusion: EDG is not more effective than a traditional technique in terms of improving dispensing accuracy and decreasing the drops dispensed per application even when careful instructions are given. The results suggest that, if good instructions are provided, experienced glaucoma patients can improve their eye drop instillation performance.