Instillation success rates among glaucoma eyedrop products: patient survey in Japan.

backgroundGlaucoma is the leading cause of blindness in Japan and poses a significant public health challenge. Previous studies have reported low success rates for antiglaucoma eyedrop instillation. Our earlier research demonstrated that various physical attributes—including the squeezing force required to dispense a drop—differ markedly among eyedrop products. However, no prior studies have examined how instillation success rates vary across products or which container or formulation characteristics influence these rates. This study aimed to assess how instillation success varies by patient characteristics and product attributes and to develop predictive models based on container and formulation properties.

methodsA web-based survey was conducted in April 2025 among glaucoma patients aged ≥ 40 years who were undergoing eyedrop therapy without assistive devices. The survey investigated daily instillation practices and success. Ten first-line antiglaucoma products across eight brands (prostanoid receptor-related drugs and β-adrenergic receptor blockers) were selected. Responses were obtained from 800 patients (100 per brand). The first instillation attempt success rate (FIASR) and the expected number of attempts for a successful instillation (ENASI) were analyzed according to patient and product characteristics. Multiple regression analyses were conducted to develop estimation models based on container and formulation features.

resultsNeither patient sex, age, nor concomitant use of non-glaucoma eyedrops showed a significant influence on instillation success. Treatment experience was relatively impactful: patients with over one year of eyedrop use exhibited higher FIASR and lower ENASI than those with less experience, although not statistically significant. No consistent differences in instillation success were observed across products. Regression models did not yield significant predictors, but trend-level findings suggested that dimpled bottles had higher FIASR than cylindrical or flat types. Lower squeezing force, larger pinchable area, and lower solution viscosity were also associated with improved instillation success.

conclusionsThis is the first study to quantify instillation success rates in real-world glaucoma care from patient and product perspectives, and explore their relationship with product characteristics. The findings suggest that treatment experience may be more influential than demographic or product factors. These insights may assist clinicians and pharmacists in refining patient education and optimizing prescribing strategies.