Ocular Demodex folliculorum: prevalence and associated symptoms in an Irish population
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To investigate the prevalence of ocular Demodex folliculorum (DF) in an Irish population. To validate a modified Ocular Surface Disease Index questionnaire and employ it to evaluate the relationship between dry eye symptoms and the presence of DF.
One hundred and fifty-six subjects were enrolled in an epidemiological cross-sectional prevalence study. Each subject completed a novel questionnaire on ocular symptoms and was assessed for the presence of DF. Data was analysed to assess prevalence and to search for significant links between each symptom and DF.
An overall prevalence of 68% was found. Total mean number of DF found on microscopic examination was 3.83 mites per subject (range 0–25). The presence of symptoms was higher among individuals with DF (P = 0.04). Itch was found to be the symptom most significantly associated with the presence and number of DF (P = 0.025 and P = 0.035, respectively). The questionnaire showed good internal consistency (Cronbach’s alpha; α > 0.7) and good reliability (Intra-class Correlation Co-efficient; ICC > 0.7). The sensitivity and specificity of a positive symptom result using the questionnaire were 70.8% and 46.9%, respectively.
There is a strong association between the prevalence of DF and symptoms, in particular itchy eyes. However, not all patients with DF will be symptomatic. The newly developed questionnaire is a reliable instrument for measuring change in symptoms over a period of time and suitable for observing patient reported outcomes in interventional treatment studies.
KeywordsDemodex folliculorum Prevalence Dry eye symptoms Blepharitis
The authors’ thanks the management and staff of the National Optometry Centre for providing use of the premises and equipment, and helping with diary management and subject recruitment. The final year Optometry students assisted with data collection and subject recruitment.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest. This research was conducted as part of a self-funded postgraduate research degree.
Human and animal rights
All procedures performed in this study involving human participants were in accordance with the ethical standards of Dublin Institute of Technology and with the Tenets of Helsinki Declaration of Human Studies .
Informed consent was obtained from all individual participants included in the study.
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