A recent study evaluated the role of Demodex infestation of the eyelids in patients with recurrent herpetic keratitis and concluded that recognizing and treating it early can help halt progression to herpetic corneal infection.

The retrospective case series included 27 patients with ocular demodicosis and recurrent herpetic keratitis currently undergoing conventional treatments. The researchers collected demographic data and clinical photographs. After confirming the presence of Demodex, they prescribed eyelid scrubs and reviewed treatment responses.

They characterized herpetic keratitis by epithelial defect, which was associated with stromal involvement in 12 cases (dendritic lesions in seven eyes, geographic ulcer in three eyes and neurotrophic ulcer in two eyes). They observed no epithelial defect in the six cases of stromal reactivation (disciform keratitis in two eyes, immune ring in three eyes and ghost vessel in one eye). In 15 cases, they observed active anterior uveitis with keratic precipitates.

All patients had Demodex blepharitis with cylindrical dandruff along the lashes, the researchers reported. This diagnosis pointed to other ocular findings, such as meibomian gland dysfunction (15 eyes), misaligned lashes (eight eyes), telangiectasia (14 eyes), conjunctivitis (18 eyes) and ocular rosacea (three eyes).

Once the Demodex infestation was under control and the blepharitis had resolved, patients reported improvement of ocular symptoms, and the researchers noted stable clinical outcomes.

“Initial unstable clinical presentations showed deterioration of corneal melting into descemetocele, corneal perforation, recalcitrant stromal infiltration/uveitis and uncontrollable IOP, despite antiherpetic medication,” the researchers wrote in their paper. They emphasized that if patients fail to respond to antiviral therapy for more than a week, the following should be considered: potential antiviral toxicity, resistance to antiviral therapy, neurotrophic status, poor compliance with treatment or an alternative diagnosis.

The study was limited in that it didn’t include a control group to compare the immune markers between ocular demodicosis with herpetic keratitis and pure herpetic keratitis. Additionally, the researchers wrote that they didn’t record specific Demodex species or total numbers of distribution. These details matter because D. folliculorum is more commonly found at the base of eyelashes and is therefore more easily detectable than D. brevis, which resides in the meibomian and sebaceous glands and is often related to corneal involvement. Number of mites also significantly correlates with keratitis severity.

Nevertheless, the study authors concluded, “Patients with herpetic keratitis should be meticulously examined and routinely screened for concomitant Demodex eyelid infestation, which requires specific treatment modalities to improve long-term visual outcome.”

Hung K, Lan Y, Lin J, et al. Potential role and significance of ocular demodicosis in patients with concomitant refractory herpetic keratitis. Clin Ophthalmol. 2020;14:4469-82.