AFTER FORGETTING to wear his orthokeratology (ortho-k) lenses for two nights in a row, a 12-year-old boy realized that his regressed vision would not be sufficient for his next two days of basketball tournaments. He then decided to wear his ortho-k lenses for that day, that night, and the following day and night.

On the third day, the patient presented complaining of eye pain and photophobia, and slit lamp examination revealed diffuse roundish, gray-white nonstaining areas of opacity throughout both corneas. The patient was diagnosed with bilateral sterile infiltrative keratitis.

Corneal infiltrates can be divided into two broad categories: sterile and microbial/infectious. Sterile infiltrates are the result of an immune response that is present without true corneal microbial infection, and are theoretically negative when cultured. However, the term “sterile” is a bit of a misnomer, as bacteria and/or bacterial byproducts (endotoxins and exotoxins) are commonly found in surrounding tissue and/or associated contact lenses or cases (Robboy et al, 2003). Thus, treatment often includes both a steroid to reduce the immune response and inflammation and an antibiotic to mitigate any bacterial presence.

Exposure to bacteria increases with poor lens care and compliance, insufficient cleaning of lenses and cases, failure to replace lenses as recommended, and overnight/extended wear (Stapleton et al, 2021). However, other nonbacterial etiologies have been proposed, including tight or poorly fitting lenses, solution preservatives or sensitivities, silicone hydrogel lens materials, and smoking (Ho et al, 2021).

Variations in presentation and nomenclature of sterile infiltrates include contact lens-associated red eye (CLARE) and contact lens peripheral ulcer (CLPU). It can sometimes be difficult to tell whether infiltrates are sterile or microbial. If there is a staining epithelial defect overlying an infiltrate (by definition an ulcer, no matter how small, and particularly if centrally located), microbial keratitis should be strongly considered.

Sterile infiltrates are a commonly encountered soft contact lens complication, with an annual incidence of symptomatic infiltrates being anywhere from 0.5% to 6.0% (lower estimates in daily wear and higher in extended wear) (Ho et al, 2021). Infiltrates found in asymptomatic patients may be even more common, as high as 10% to 25% of soft contact lens wearers per year.

In GP wearers, the frequency is notably less. The relative risk of sterile infiltrates for daily wear soft lens wearers is estimated to be 2.3 times higher than for daily GP wearers, and for extended wear soft lens wearers 4.6 times higher (Robboy et al, 2003). Again, extended wear of lenses appears to increase risk, though studies in ortho-k (the most common reason for overnight use of GP lenses) indicate that corneal infiltrate events are rare, and when they occur are more likely to be microbial than sterile in nature (Bullimore and Johnson, 2020).

With the growing popularity of overnight GP wear in ortho-k, the finding of sterile infiltrates in GP wearers may increase going forward (Ho et al, 2021). However, it remains unlikely that they will ever be as commonly encountered as in soft lens wearers, and they are relatively easy to manage without significant threat to vision.

Patient education on proper wear and care for GP lenses can help prevent these issues and is critical in preventing more serious microbial infections as well. This education must be ongoing, as the pediatric population wearing ortho-k lenses often “forgets” the importance of compliance.

REFERENCES

1. Robboy MW, Comstock TL, Kalsow CM. Contact lens-associated corneal infiltrates. Eye Contact Lens. 2003 Jul;29:146-154.

2. Stapleton F, Bakkar M, Carnt N, et al. CLEAR - Contact lens complications. Cont Lens Anterior Eye. 2021 Apr;44:330-367.

3. Ho L, Jalbert I, Watt K, Hui A. Current understanding and therapeutic management of contact lens associated sterile corneal infiltrates and microbial keratitis. Clin Exp Optom. 2021 Apr;104:323-333.

4. Bullimore MA, Johnson LA. Overnight orthokeratology. Cont Lens Anterior Eye. 2020 Aug;43:322-332.