It is stated in some studies that Demodex mites, which are frequently detected in humans around the world, may be pathogenic in chronic eyelid diseases [16,17,1]. While Demodex folliculorum causes anterior blepharitis, DB positivity shows a strong correlation with the prevalence of posterior blepharitis, meibomian gland dysfunction, recurrent chalazion, and keratoconjunctivitis [12,18]. In the pathogenesis of blepharitis, it has been reported that mites are vectors in the transport of some bacteria such as Bacillus, Staphylococcus and Streptococcus, and mites play a role with the bacteria especially in cases that are resistant to treatment and recurrent after treatment [12,19]. At the final point, mites are considered as a causative factor for blepharitis .
The etiology of chalazion has not been explained and is still unknown. The accumulated secretion causes an inflammatory reaction in the surrounding tissues. Another factor could be bacterial and / or Demodex infestation [7,6,13].
Considering the epidemiological studies on blepharitis and chalazion, it is seen that the prevalence of Demodex spp. ranges from 28.8% to 84% in patients with blepharitis, 63.2% to 91.67% in patients with chalazion, and 4.6% to 54.9% in the healthy control group. The results of our study are compatible with the literature [21-24,6,25]. In several studies, no significant difference was found between patients with blepharitis and the control group in terms of mite positivity [21,22]. However, it is stated in most of the literature that the presence of parasites is significantly higher in patients with blepharitis and chalazion [16,24,6,25,13]. In our study, it was found that the presence of Demodex spp. was statistically significantly higher in patients with blepharitis and chalazion.
It is known that the most common type in almost all studies showing the relationship between blepharitis and Demodex is DF [16,25-27]. Our study is similar to studies reporting that DF is significantly more common than DB in eyelash follicles in patients diagnosed with blepharitis.
Studies examining the relationship between chalazion and Demodex show that DF dominance is at the forefront, as in blepharitis studies . In our study, it was determined that DF was the most common mite in the chalazion group. In addition, although there was no statistically significant difference between DF and DB in patients diagnosed with chalazion, the incidence of DB was found to be significantly higher than blepharitis and control groups. Based on the results, we think that both species may have a role in the pathogenesis of chalazion.
Although the eyelash hair removal method was commonly used in ocular demodicosis studies, which eye (right eye, left eye, both eyes, lower or upper eyelids), which eyelashes (cylindrical dandruff eyelashes or random) and how many eyelashes to be taken could not be made a standard method . Apart from the eyelash epilation method, resection samples were also evaluated in patients with chalazion . The average number of mites in the studies is not based on a standard method. In some studies, the average Demodex number was obtained by dividing the total number of mites by the number of Demodex positive volunteers [29,28], while in others the total number of mites was divided by the number of all volunteers [23,27]. The issues such as the different number of eyelashes, giving the average number of mites according to all patients or positive patients, giving the average per patient or per eyelash vary. This makes it difficult for researchers to interpret between studies. As a result of our observations and research, we think that positive individuals should be evaluated while giving the average number of mites. Because:
a) When non-infested patients are included in the studied patient group, the average "mite density in infested patients in X group", which is the main focus, is reduced.
b) The main goal in medicine is to develop a solution-treatment for the current problem. "Mite positive in X group" individuals should be evaluated in order to detect the change in the number of mites before and after treatment studies.
c) Determining how the number of mites changes when species are found individually or together in "Mite positive in group X" will help to illuminate the pathogenesis between the mite and the disease.
In addition, we think that the average Demodex numbers should be given per eyelash. Although the researchers examine different numbers of eyelashes, by giving the results to the eyelash head, we provide the researchers with ease in interpretation and achieve a standard in the literature. If we list our two suggestions on this subject:
1) Positive individuals should be taken into consideration while giving average mite numbers.
2) Average mite counts should be given per eyelash.
In our study, we found it appropriate to give results with the average number of mites per eyelash. In the blepharitis group, the average number of mites when DF + DB coexists were found to be significantly higher compared to those with only DF or only DB and total mites. It was found that the number of mites increased in patients with blepharitis if both species were seen together.
Similarly, there is no standardization in the data in studies examining the relationship between chalazion and Demodex. Schear et al. found 0.804 ± 1.03 DF per eyelash epilled, while the average DF in the control group was found to be 0.487 ± 0.82 . In our study, the DF number per eyelash was found by Schear et al. shows similarities with the results of their study. In addition, the average number of mites in DF + DB coexistence was found to be significantly higher in patients compared to those with DB alone.
It is reported that the increase in the activity of the sebaceous glands that occur with age and the changes in the sebum composition will facilitate the increase of mites in the elderly . In many studies, it has been reported that ocular Demodex infestation increases with age, it is seen in 84% of the population in their 60s and in 100% of the population aged 70 and over [12,16,21,23]. Kasetsuwan et al. reported the prevalence of ocular demodicosis as 70% over the age of 80 . In other studies, it was reported that infestation was significantly higher in patients with blepharitis over the age of 50, those over 60 years of age, and those with ocular disease over the age of 70 [31,10,26]. However, in some studies, no significant difference was found between increasing age and the presence of mites [22,32]. This study supports the general literature. A statistically significant positive correlation was found between age and the presence of Demodex spp. in patients with blepharitis. We think that this is caused by the weakening immune system, increased sebum amount and weakened-deteriorating skin structure in the elderly.
Although there is no statistically significant difference, there are studies reporting that infestation is higher in women , as well as studies reporting that it is common in men . Zeytun and Karakurt stated that the prevalence of mites is significantly higher in males . Most of the studies argue that there is no significant difference between gender and Demodex spp. [16,22,23,26,32]. This study supports the literature. No significant difference was found between gender and mite positivity in patients with blepharitis.
As a result of the resection samples of patients with chalazion, no significant relationship was found between gender and the presence of mites. Tarkowski et al. reported that the infestation was in a similar distribution in men and women with chalazion [24,6]. Our study is the same as the results of the other two studies. There was no significant relationship between sex and mite positivity in the chalazion group.
It was reported that the symptoms of Demodex spp. positive blepharitis patients did not differ from those of other blepharitis patients. In some studies, it was reported that most of the patients were asymptomatic and their complaints generally increased in hot weather . The most common complaints in patients with infected blepharitis were itching, foreign body sensation (stinging) and redness. Eyelash sticking, dandruff at the bottom of the eyelashes, mild papillary conjunctivitis, meibomian gland dysfunction and telangiectasia were seen in patients with chronic blepharitis . In addition, it was stated that patients had ocular pain, contact lens intolerance, photophobia and crusting . Symptoms were usually worse in the morning, and several flare-ups and remissions might ocur . In this study, a significant difference was found between the presence of symptoms and mite positivity in the blepharitis group. The most common complaints in patients with blepharitis were itching, stinging (foreign body sensation) and burning, respectively. Although itching ,in our study, was the most common symptom as in other studies, this symptom was similar in patients with mite negative and positive blepharitis like the studies conducted by Inceboz et al . In our study, among these symptoms, only a significant relationship was found between stinging complaint and the presence of DF.
While patients with chalazion have eyelid nodules showing pain, inflammation and sensitivity in the acute phase, there is a permanent, painless mass in the chronic phase . Cylindrical dandruff was not common, as most patients with recurrent chalazion had regular eyelid hygiene . In this study, the complaints seen in patients with chalazion were itching, dandruff at the base of the eyelashes, stinging, burning and watering, respectively. However, there was no significant difference between mite positivity and the presence of symptoms.
Studies show that DF is increased in immunocompromised patients such as diabetes, end-stage chronic renal failure, Behçet's disease, urological cancers and eyelid basal cell carcinomas [11,34]. It has been reported that DF is an important factor in eye diseases such as blepharitis and that the mite is more common in immune system disorders. In a study, DF was detected in 27.4% of eyelashes of 42 patients with Type 2 diabetes and 19% in 42 control group volunteers. It has been reported that infestation is significantly higher in patients with diabetes . In our study, it was determined that the prevalence of infestation was higher in patients with systemic disease in both groups. However, no significant difference was found between the presence of systemic disease and mite positivity in the blepharitis and chalazion groups. We think that this is due to the low number of patients with systemic diseases in our target study groups.
There is no information about the relationship between education level and mite positivity in the available literature. In our study, a negative correlation was observed between education level and the positivity of Demodex spp. in the blepharitis and control group. However, while this negative correlation was not significant in the control group, it was significant in the blepharitis group. It has been found that as the education level increases in patients with blepharitis, the mite positivity decreases. The reason for this may be the increase in personal hygiene practices and compliance with protection methods due to the increase in education level. There was no significant difference in the chalazion group.
It was reported that there was no significant relationship between pet feeding and demodicosis in patients with blepharitis . In our study, no significant difference was found between animal feeding and mite positivity in blepharitis, chalazion and control groups. We think that this is due to the fact that mites transmitted from infested animals are host specific and can only cause a temporary dermatitis in the human body.
As a result, clinicians should warn especially the elderly patients against Demodex mites that infect eyelashes. Patients with recurrent blepharitis and chalazion who do not respond to the current blepharitis treatment procedure should be investigated and treated for Demodex spp.