Acanthamoeba keratitis (AK) is a severe and often refractory corneal infection, frequently associated with contact lens wear while swimming or rinsing lenses with tap water. Despite intensive medical therapy, many cases fail to resolve due to the parasite’s highly resistant cystic form, which can persist within the corneal stroma. A recently published case report in Eye and Vision by Hafezi et al. explores a novel treatment approach: same-session dual chromophore photoactivated chromophore for keratitis-corneal cross-linking (PACK-CXL) using riboflavin/UV-A and rose bengal/green light.
Overcoming AK Treatment Challenges
Conventional PACK-CXL using riboflavin and UV-A has proven effective in bacterial and fungal keratitis but has not demonstrated consistent success in treating AK. Similarly, rose bengal/green light PACK-CXL has shown promise in fungal infections but has not been sufficient against Acanthamoeba. Recognizing this limitation, the ELZA Institute investigated a combined approach utilizing both chromophores in a single procedure.
AK presents unique challenges due to the parasite’s ability to exist in a cystic form, which is highly resistant to standard antimicrobial therapy. The need for prolonged treatment with multiple antimicrobial agents increases the risk of corneal scarring and visual impairment. Therefore, the development of more effective therapeutic strategies, such as dual chromophore PACK-CXL, is critical to improving outcomes for patients with recalcitrant infections.
Case Study: A Same-Session Sequential Approach
In the reported case, a 44-year-old patient with AK unresponsive to 10 months of standard therapy underwent three same-session PACK-CXL procedures at the ELZA Institute. The protocol involved sequential application of riboflavin/UV-A (365 nm, 10 J/cm2) followed by rose bengal/green light (522 nm, 5.4 J/cm2) irradiation. After three treatments, the infection was eradicated, and the cornea stabilized, though a penetrating keratoplasty was ultimately required for visual rehabilitation.
Throughout the treatment course, the patient showed progressive clinical improvement. Following the second PACK-CXL session, signs of active infection diminished significantly, with reduced ocular pain, photophobia, and epiphora. Confocal microscopy confirmed the absence of viable Acanthamoeba cysts after the final treatment session, supporting the efficacy of the dual chromophore approach in eliminating the infection.
A New Treatment Paradigm?
This case suggests combining two chromophores with distinct photochemical properties may enhance PACK-CXL’s efficacy in treating AK. The sequential application allows each chromophore to exert its effect without interference, potentially leading to improved pathogen eradication and stromal strengthening. The unique absorption spectra of riboflavin and rose bengal ensure that the chromophores do not compete for energy, maximizing the photochemical response within the corneal tissue.
Furthermore, this novel approach could have broader implications for managing severe and treatment-resistant infectious keratitis. By reinforcing the corneal stroma while simultaneously exerting antimicrobial effects, dual chromophore PACK-CXL may provide a valuable adjunct to conventional antimicrobial therapy. Future studies should establish standardized treatment protocols and assess long-term outcomes in larger patient cohorts.
While further clinical research is required, this innovative approach may offer a viable option for refractory AK cases. The successful eradication of infection in this patient highlights the potential of dual chromophore PACK-CXL as an emerging therapeutic modality for challenging corneal infections.
Reference: Hafezi F, Messerli J, Torres-Netto EA, et al. Same-session dual chromophore riboflavin/UV-A and rose bengal/green light PACK-CXL in Acanthamoeba keratitis: a case report. Eye and Vis. 2025;12(1):2. PubMed Link.
