Studies: Demodex mites and eye discomfort
Study 1: All about discomfort?
I found this Austrian study interesting….
What they found was that mites were associated with discomfort, but the association with specific clinical signs of MGD varied: Gland expressibility, and gland dropout, were not related to the mites, but some of the other signs were.
Once again, as is so often the case in all things dry eye, symptoms (pain, discomfort, whatever language you want to use for it) do not match well with clinical signs (test results).
The good news about this study is that we know it’s not all that hard to get mites under control with lid hygiene products that contain tea tree oil. If 40% of people with the discomfort have mites, why wouldn’t they all go on a simple at-home treatment to help improve it? It’s easy to do.
Demodex mite infestation and its associations with tear film and ocular surface parameters in patients with ocular discomfort.
Rabensteiner et al, American Journal of Ophthalmology, March 2019.
The presence of Demodex species can be associated with blepharitis. Their pathogenic potential in Meibomian Gland Dysfunction (MGD) was discussed. The purpose of this study was to determine the prevalence of Demodex mites in eyelashes of Austrian patients with ocular discomfort and to evaluate associated changes of the lid margins and meibomian glands.
case-control study METHODS: Two-hundred-twenty-nine consecutive patients with ocular discomfort from an Austrian dry eye clinic were investigated for the presence of Demodex mites on sampled eyelashes. Associations of a mite infestation with individual dry eye and lid parameters were assessed. Lid margins were evaluated for scales, vascularization, Marx line, expressibility and quality of meibum, as well as drop-out of meibomian glands.
Demodex mites were identified in 40.2% of patients suffering from ocular discomfort (mean mite count 3.3 ± 2.9 per patient). The infestation with mites was associated with the presence of significantly more cylindrical scales (sleeves), a higher Marx line score and a lower quality of meibum compared to mite-free patients. There were no significant associations with the expressibility and the drop-out of meibomian glands.
The prevalence of Demodex mites in patients with ocular discomfort is high. The mean mite count per patient in this Austrian dry eye unit population is lower compared to previously published data from Asian regions. The infestation of the eyelids with Demodex species is associated with changes of the anterior and posterior lid margin, suggesting a pathogenic role in blepharitis and MGD as well.
Study 2: Ocular surface and demodex in kids and adults
This was a study of a Chinese population, looking at people with and without blepharokeratoconjunctivitis. 56% of the BKC patients had demodex mites, compared to 26% in healthy patients.
Evaluation of the ocular surface characteristics and Demodex infestation in paediatric and adult blepharokeratoconjunctivitis.
Wu M et al, BMC Ophthalmology, March 2019
To evaluate the ocular surface characteristics and the infestation of Demodex in Chinese paediatric and adult blepharokeratoconjunctivitis (BKC).
Fifty consecutive patients with BKC and 50 age- and sex-matched healthy subjects were enrolled. Lid margin characteristics and corneal disorders were evaluated under slit-lamp illumination. Four eyelashes were collected from each eye to examine Demodex infestation by light microscopy.
Corneal neovascularization (P = 0.001) and scarring (P = 0.040) were significantly worse in children than in adults with BKC, whereas meibum quality was worse in adults (P = 0.008). Diagnosis delay was longer in children with BKC than in adults (2.2 vs 1.2 years, P = 0.022). Demodex infestation was more frequent in subjects with BKC than in healthy subjects (56% vs 26%, P = 0.002). The lid margin inflammation and meibomian gland dysfunction were worse in Demodex-positive subjects than in Demodex-negative subjects with BKC.
Children with BKC had severer corneal disorders compared with adult BKC patients, which may be caused by a long-delayed diagnosis. Ocular demodicosis was more common in subjects with BKC. Ocular Demodex infestation was associated with worse lid margin inflammation and meibomian gland dysfunction.