Pharmacovigilance typically focuses on monitoring the safety of medicines, vaccines, and biologics. Yet, the scope of patient safety surveillance extends further – to medical devices and health-related products. Among these, contact lens hold a unique position. They are widely used and directly interface with one of the body’s most sensitive structures – the cornea.

Worldwide, more than 140 million people wear contact lenses. For many, they are indispensable for daily vision correction. However, the convenience comes with potential risks ranging from mild irritation to sight-threatening infections. For pharmacovigilance specialists, these risks demand attention: every case report, every unusual pathogen, and every behavioural factor adds to our collective knowledge on preventing harm.

The DrugCard platform, used for continuous medical literature monitoring, has recently highlighted a compelling case of Serratia marcescens keratitis linked to contact lens use. This case underscores why pharmacovigilance cannot ignore the intersection between medical devices, behaviour, and infection risk.

Contact Lens Safety Issues: An Overview

Contact lens complications fall into two main categories: infectious and non-infectious. Both warrant monitoring, as they influence patient adherence, visual outcomes, and even long-term ocular health.

Non-Infectious Complications

Non-infectious reactions often arise from hypoxia, mechanical irritation, or allergic responses. Commonly reported conditions include:

Epithelial edema and microcysts – due to inadequate oxygen permeability.

Superficial punctate keratitis – linked to poor tear film stability.

Corneal warpage – long-term lens-induced corneal remodelling.

Conjunctival reactions – including giant papillary conjunctivitis and superior limbic keratoconjunctivitis.

Neovascularisation – blood vessel growth into normally avascular corneal tissue, often due to chronic hypoxia.

These conditions are generally reversible when detected early, but they highlight how contact lenses can alter ocular physiology over time.

Infectious Complications

The most significant threat is microbial keratitis (MK), a corneal infection that can rapidly progress to vision loss. Key culprits include:

Pseudomonas aeruginosa is the most common organism in contact lens-related keratitis.

Acanthamoeba spp. – notorious for severe and difficult-to-treat keratitis.

Fusarium spp. – a fungal cause often linked to contaminated solutions.

Serratia marcescens – increasingly recognised as a cause of aggressive keratitis.

Epidemiological studies suggest that overnight lens wear increases the risk of microbial keratitis by 5–7 times, while poor hygiene practices multiply the risk even further.

Case Report Spotlight: Serratia marcescens keratitis

Thanks to DrugCard’s monitoring of the literature, a noteworthy case was uncovered in the medical literature. This case provides invaluable insights into both clinical management and risk prevention.

A 22-year-old medical student developed sudden Serratia marcescens keratitis after using soft contact lenses. She admitted to occasionally showering while wearing lenses and had exceeded the recommended 4-week replacement schedule by wearing monthly disposables for 5 weeks. 

Clinical findings included conjunctival injection, anterior chamber inflammation, and a corneal abscess with epithelial defect. Initial treatment with moxifloxacin failed. The regimen was escalated to fortified vancomycin, ceftriaxone, and voriconazole. Once cultures confirmed S. marcescens, therapy was streamlined to fortified ceftriaxone, with full recovery and minimal scarring at one month; visual acuity returned to 20/20.

Lessons for Pharmacovigilance Specialists

This case offers several key takeaways relevant to the field of pharmacovigilance:

1. The Role of Behaviour in Device Safety

Unlike drug-related adverse drug reactions, which depend mainly on dose and pharmacokinetics, contact lens complications usually arise from user behaviour. Overwear, poor hygiene, and water exposure remain leading contributors to keratitis. Monitoring and reporting must therefore integrate behavioural risk factors.

2. Antimicrobial Resistance Considerations

The failure of moxifloxacin highlights an emerging issue: fluoroquinolone resistance in ocular pathogens. For pharmacovigilance, this underscores the importance of culture-directed therapy and the need to track resistance trends in device-associated infections.

3. Interdisciplinary Safety Monitoring

This case bridges multiple domains – ophthalmology, microbiology, and pharmacovigilance. It shows that medical device safety monitoring must integrate into broader patient safety frameworks instead of staying siloed.

The Role of DrugCard in Literature-Based Safety Monitoring

The discovery of this rare case report highlights the value of continuous medical literature monitoring through platforms like DrugCard.

Traditional spontaneous reporting systems may miss such cases.

Monitoring the medical literature captures rare but important safety signals.

Pharmacovigilance professionals gain early awareness of emerging pathogens and resistance trends.

By integrating DrugCard findings into routine pharmacovigilance practice, safety specialists can anticipate new drug – or device-related risks.

Conclusion

Contact lens safety extends far beyond ophthalmology – it is a vital pharmacovigilance concern. The case of Serratia marcescens keratitis demonstrates how everyday user behaviours, the growing challenge of antimicrobial resistance, and timely clinical decision-making intersect to shape patient safety outcomes.

Preventing such vision-threatening complications requires a multi-layered approach: continuous monitoring, patient education, and treatment strategies guided by culture results rather than empiricism alone.

Platforms like DrugCard, with their ability to detect rare but clinically significant cases in the medical literature, provide an additional layer of vigilance. These insights help pharmacovigilance professionals identify early signals that might otherwise be overlooked.

Ultimately, integrating these lessons into routine practice strengthens our ability to ensure that contact lenses remain a tool for better vision and a safe and reliable option for millions of users worldwide.