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Dry eye patients with Demodex have decreased nerve density

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VANCOUVER, British Columbia – Researchers concluded that patients who have both Demodex and dry eye are at a great risk for having significantly reduced subbasal nerve density, in a poster presented here at the Association for Research in Ophthalmology meeting.

“And so, patients who have both should have extra attention taken to resolve the Demodex in addition to their dry eye,” lead author Nicholas Pondelis told Primary Care Optometry News.

The retrospective study included 57 patients that were divided into three groups: 12 with both dry eye disease and Demodex folliculorum blepharitis, 19 with dry eye alone and 26 controls, according to the study. All patients underwent confocal microscopy imaging of the central corneal subbasal nerve plexus with the Heidelberg Retinal Tomograph 3/Rostock Cornea Module and examination of the eyelid margin at the lash follicles for D. folliculorum.

Pondelis and colleagues found reduced total central corneal nerve density in patients with both dry eye disease and Demodex blepharitis (15.69 ± 1.49) compared to those with dry eye alone (19.63 ± 1.25; p = 0.0001) and normal controls (22.60 ± 0.77; p = 0.042), according to the study.

In addition, “the more mites you have per follicle on average, the lower your nerve density is, as well,” Pondelis said. “And that is the same for the total nerve density and the branch nerve density.”

He noted the importance of this finding in light of the Tear Film and Ocular Surface Society Dry Eye Workshop II report discussion of nerve sensory abnormalities playing into reduced tear production.

In addition, more links are being found between Demodex and conditions such as rosacea, he said. The doctor in his practice orders confocal microscopy images for patients in whom he sees cylindrical dandruff, and “it’s part of our new dry eye patient pre-testing.”

Pondelis said several theories for the correlation have been discussed.

“One simple thing could just be that there’s more rubbing of the eye with Demodex, and that’s causing dry eye because there’s more inflammation, and it’s not letting the nerves heal from the rubbing,” he said. “We’re going to look into ruling out early stage keratoconus patients, to see if the rubbing alone is causing any differences in the nerves.” – by Nancy Hemphill, ELS, FAAO

Reference:

Pondelis N, et al. Demodex folliculorum mite density is associated with reduced cornea subbasal nerve density in patients with dry eye disease. Presented at: Association for Research in Vision and Ophthalmology; Vancouver, British Columbia; April 28-May 2, 2019.

Disclosure: Pondelis reports no relevant financial disclosures. Please see the full study for all other authors’ financial disclosures.