Why Must the Safety of Eye Drops Be Proven Through Laboratory Testing?
The eye is a complex sensory organ with specialized anatomy and physiology designed for vision. It is highly sensitive to various factors, ranging from environmental exposure such as dust, smoke, and pollution, to prolonged use of digital devices, as well as medical conditions including allergies, infections, and dry eye.
This sensitivity can lead to mild disturbances that reduce comfort and quality of life, prompting many people to seek quick relief through the use of eye drops.
- Types and Functions of Eye Drops
- How Long Are Eye Drops Safe to Use After Opening?
- Signs That Eye Drops Are No Longer Suitable for Use
Types and Functions of Eye Drops
Eye drops offer a non-invasive route of drug administration, meaning they do not involve penetration of the skin. They are available in various types and formulations, including artificial tears for moisturizing, saline solutions for eye rinsing, antihistamines or decongestants for allergies, antibiotics for bacterial infections, corticosteroids for inflammation, and specialized medications for patients with glaucoma.
These formulations are carefully designed to be safe for direct application to the ocular surface. In general, eye drops are ready-to-use products marketed with or without preservatives.
They are available in single-dose and multi-dose packaging. Any multi-dose eye drop product intended for repeated use must have a mechanism to maintain sterility throughout its period of use.
For this reason, many products include preservatives to keep the formulation sterile and prevent microbial contamination. However, because eye drops are applied directly to a highly sensitive organ, product quality and sterility are critical factors.
The use of contaminated eye drops or those used beyond their safe period can cause severe irritation, new infections, or even damage to the ocular surface. Therefore, understanding the expiration period of eye drops, including the safe usage time after opening, is an essential part of proper use.
How Long Are Eye Drops Safe to Use After Opening?
Once an eye drop container is opened, the bottle is at risk of exposure to microorganisms from the environment or from the dropper tip accidentally touching the eye surface, skin, or hands. The risk of contamination increases with multi-dose bottles that are used repeatedly over several weeks.
To reduce the risk of infection, many products contain preservatives such as benzalkonium chloride (BAK) or other antimicrobial agents. However, although effective against microbes, several studies have shown that long-term use of BAK may cause ocular surface toxicity, disrupt tear film stability, and worsen dry eye symptoms.
For this reason, in cases of long-term routine use such as in glaucoma or dry-eye syndrome, physicians often recommend considering preservative-free formulations or single-dose packaging. According to the NHS Specialist Pharmacy Service, if there are no specific instructions from the manufacturer, multi-dose eye drops are generally recommended to be discarded after 28 days (approximately four weeks) from the date of opening.
This guideline aims to prevent the risk of microbial contamination during daily use at home or in healthcare settings. However, the final decision should always refer to the official manufacturer’s instructions on the packaging.
Some products may have longer stability, while others have a shorter shelf life, especially preservative-free products, which often must be discarded within hours or days after opening.
Signs That Eye Drops Are No Longer Suitable for Use
Signs that eye drops are no longer safe to use include visible changes such as cloudiness, discoloration, the presence of sediment or undissolved particles, unusual odor, excessive stinging compared to previous use, usage beyond the 28-day period after opening, or expiration based on the date stated on the packaging.
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Given the high risk of contamination and the serious consequences it can have on eye health, the safety of eye drops cannot rely solely on formulation claims or the presence of preservatives. Scientific evidence through laboratory testing is required to ensure that products remain sterile, stable, and safe throughout their shelf life.
This is where laboratory testing plays a crucial role, both for manufacturers and brand owners, to ensure that every product on the market truly meets quality and safety standards.The risks of contamination, reduced sterility, and ocular irritation demonstrate that the safety of eye drops cannot be assessed solely on theoretical formulation.
Each product must have its safety proven through laboratory testing to ensure maintained sterility, product stability, and minimal risk to users throughout its intended shelf life. IML Testing and Research provides comprehensive and reliable laboratory testing services for eye drops, including sterility testing, microbial contamination testing, stability testing, and quality assessments in accordance with regulatory standards.
Ensure that your eye drop products have undergone appropriate laboratory testing before being marketed, to safeguard product safety and maintain consumer trust.
Author: Jihan
Editor: Sabilla Reza
References:
Coroi, M. C., Bungau, S., & Tit, M. (2015). PRESERVATIVES FROM THE EYE DROPS AND THE OCULAR SURFACE. Romanian journal of ophthalmology, 59(1), 2–5.
Iskandar, K., Marchin, L., Kodjikian, L., Rocher, M., & Roques, C. (2022). Highlighting the Microbial Contamination of the Dropper Tip and Cap of In-Use Eye Drops, the Associated Contributory Factors, and the Risk of Infection: A Past-30-Years Literature Review. Pharmaceutics, 14(10), 2176. https://doi.org/10.3390/pharmaceutics14102176
NHS Pharmaceutical Quality. (2025). Guidance on the in-use shelf life for eye drops and ointments.
Walsh, K., & Jones, L. (2019). The use of preservatives in dry eye drops. Clinical ophthalmology (Auckland, N.Z.), 13, 1409–1425. https://doi.org/10.2147/OPTH.S211611
