Really bugging our patients and practices?

There has been much discussion around Demodex blepharitis as of late, due to the anticipation of a new drug designed to target and control the condition’s root cause. This begs the questions: how prevalent is this mite, and does it cause that much trouble?

Here, I answer these questions:

PREVALENCE?

I was challenged a few years ago to have my patients look down during the slit lamp exam to enable me to evaluate the upper lid margin for collarettes, a pathognomonic sign of Demodex blepharitis. It was an eye-opening experience (pun intended), as I realized I had likely missed diagnosing several patients who had the condition. The scientific literature also bears this out.

Specifically, a recent multicenter retrospective study shows that 57.7% of patients had Demodex blepharitis, as confirmed by the presence of collarettes.1 Interestingly, 77% of those patients who had Demodex blepharitis presented for an annual exam, cataracts, and glaucoma, not for complaints, such as dryness, tearing, burning, stinging, or itching, related to Demodex blepharitis.¹ This study illustrates that if we look for the presence of Demodex blepharitis based solely on patient complaints, we will miss a large majority of these diagnoses.

TROUBLESOME?

A 2022 study revealed that eyelids with collarettes had significantly more meibomian gland atrophy on meibography than those without.² Additionally, those eyes that had more severe Demodex blepharitis had significantly more telangiectasia and meibomian gland atrophy when compared to patients with less severe Demodex blepharitis.²

How do these mites cause damage? The mechanical direct damage results from their consumption of the epithelial cells and the micro-abrasions from their claws within the meibomian glands. The outcome of this is hyperkeratinization.³ Also, the mites cause mechanical blocking of the meibomian glands where they create a home.³ They carry bacteria both on their surface, as well as within their abdomen, which is released into the meibomian glands where they burrow.³ Lastly, the proteins inside the mites, along with their debris, may actually trigger a host inflammatory response by delayed hypersensitivity.³ Any one of these mechanisms cause significant damage, but combined it is evident why Demodex blepharitis can be a problem.

TIME TO ACT

As illustrated above, overgrowth of Demodex leading to blepharitis and loss of homeostasis is prevalent and does cause trouble for our patients. Therefore, we should be taking the extra time to have the patient look down during the slit lamp examination, so Demodex blepharitis can be identified regardless of patient complaints — even if doing so makes us bug out. OM

REFERENCES

1. Trattler W, Karpecki P, Rapoport Y, et al. The Prevalence of Demodex Blepharitis in US Eye Care Clinic Patients as Determined by Collarettes: A Pathognomonic Sign. Clin Ophthalmol. 2022;16:1153-1164. doi: 10.2147/OPTH.S354692.
2. Koetting C, Yeu E. “Meibomian Gland Atrophy in Patients with Demodex Blepharitis.” Poster American Academy of Optometry, November 2022.
3. Nicholls SG, Oakley CL, Tan A, Vote BJ. Demodex species in human ocular disease: new clinicopathological aspects. Int Ophthalmol. 2017;37(1):303–312.

DR. KOETTING practices in Denver, Colo. She is a fellow of the American Academy of Optometry, diplomate of the American Board of Optometry, an active member of AOA, and a speaker and consultant for multiple companies. Follow her on Instagram at Dr_Jazz_Hands, or email her at Dr.CeceliaKoetting@gmail.com.