Related Experiment Video
Updated: Dec 11, 2025
Intravitreal Injection and Quantitation of Infection Parameters in a Mouse Model of Bacterial Endophthalmitis
Published on: February 6, 2021
Microbial Cross-contamination in Multidose Eyedrops: The Impact of Instillation Angle and Bottle Geometry
Alexandre Xavier da Costa1, Maria Cecilia Zorat Yu1, Denise de Freitas1
1Department of Ophthalmology and Visual Sciences, Federal University of São Paulo (UNIFESP), São Paulo, Brazil.
Purpose:
To evaluate the impact of instillation angle and nozzle tip geometry on cross-contamination risk of multidose ocular solution bottles.
Methods:
Pseudomonas aeruginosa solution was passed exclusively on the outside of the nozzle to simulate contamination on the exterior of topical agents. Three drops were administered from angles of 90° and 45° from bottles with either a round or sharp tip geometry, and the cultures were examined for growth. Two-hundred sixteen cultures from nine lubricant eyedrop brands currently existing in the Brazilian market were assessed for bacterial growth.
Results:
After seven days, bacterial contamination was detected in 53.7% of cultures when drops were administered at 90° and in 70.4% of cultures at 45°. Eyedrops collected from a rounded nozzle tip and an instillation angle of 90° transmitted bacteria in 69.4% of cases, whereas those administered from a sharp tip transmitted bacteria in only 22.2% of cases (P = 0.001). At an instillation angle of 45°, contamination was identified in 83.3% of bottles with a rounded tip geometry and in only eight of 18 bottles (44.4%) from those with a sharp nozzle geometry (P = 0.005).
Conclusions:
Adjusting the instillation angle of eyedrop solutions to 90°, as well as using a nozzle geometry that prevents flow of the solution to the side of the bottle, significantly reduced contamination rates.
Translational Relevance:
Standardizing drop bottles and adjusting delivery angle shows promise in reducing contamination rates and may critically impact the quality of care for patients requiring topical therapeutic agents.
Insights
Using a 90° instillation angle and sharp nozzle tips significantly reduces bacterial contamination in multidose eyedrop bottles. This finding is crucial for preventing cross-contamination and improving patient safety with topical ocular agents.
Area of Science:
- Ophthalmology
- Microbiology
- Pharmaceutical Sciences
Background:
- Multidose eyedrop bottles are prone to microbial contamination, posing a risk to ocular health.
- Cross-contamination can occur through improper instillation techniques and bottle design.
Purpose of the Study:
- To investigate how instillation angle and nozzle tip geometry affect the risk of cross-contamination in multidose ocular solution bottles.
- To identify optimal parameters for reducing microbial contamination during eyedrop administration.
Main Methods:
- Simulated contamination of eyedrop bottles using *Pseudomonas aeruginosa* solution on the nozzle exterior.
- Administered three drops from 90° and 45° angles using bottles with round or sharp tip geometries.
- Assessed 216 cultures from nine Brazilian lubricant eyedrop brands for bacterial growth over seven days.
Main Results:
- Bacterial contamination was detected in 53.7% of cultures at 90° and 70.4% at 45°.
- Sharp nozzle tips significantly reduced contamination rates compared to rounded tips at both angles (22.2% vs. 69.4% at 90°, P=0.001; 44.4% vs. 83.3% at 45°, P=0.005).
- A 90° instillation angle also showed lower contamination rates than a 45° angle when combined with specific nozzle geometries.
Conclusions:
- An upright instillation angle (90°) and nozzle designs that prevent solution flow to the bottle's exterior are effective in minimizing contamination.
- These adjustments are critical for enhancing the safety and efficacy of topical ocular treatments.
Related Concept Videos
01:28Angle Closure Glaucoma: Treatment
01:27Open Angle Glaucoma: Treatment
Drugs such as carbonic anhydrase inhibitors, α2- and...