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Demodex blepharitis in practice.

Optometrists ****

Therapeutic opticians ***

Dispensing opticians **

Contact lens opticians *

1 CET POINT

Introduction

Demodex folliculorum and Demodex brevis are two species of translucent, spindle-shaped ectoparasites that live in the hair follicles and sebaceous glands of human skin. Demodex feed on skin cells and sebum and, therefore, are most commonly found in areas rich in sebaceous glands such as the cheeks, nose, chin and ocular area; (1,2) this makes the eyelids and eyelashes an ideal habitat. There are two types of Demodex found on the human body. Demodex folliculorum (see Figure 1a) are slightly longer and typically reside in groups within the eyelash follicles. Demodex brevis (see Figure 1b) are smaller, often found in solitude, and generally reside deeper within the sebaceous and meibomian glands. In recent years, there has been an increased interest in the importance of Demodex in ophthalmology. This article discusses the role of Demodex in a clinical environment, how to examine these patients appropriately, and the current methods for treatment.

Pathogenicity

The presence of Demodex alone is not considered to be abnormal. All adults will have Demodex, (3) although it is the presence of large quantities of the mites that causes problems. (4) Increased numbers of Demodex have been associated with rosacea and other papulo-pustular skin conditions, (4-6) increased ocular surface inflammation and irritative symptoms. (7-10)

Prevalence

The prevalence of Demodex varies from 20% in younger patients, to 100% in patients over 70 years of age. (11) Increasing age remains the most predominant risk factor for Demodex infestation. (8,11,12) It is believed that humans acquire Demodex as children from older adults, and over the years the numbers of Demodex grow naturally as they continue to colonise. This results in a naturally higher prevalence of Demodex among older individuals. However, there are certain skin/medical conditions and lifestyle factors that have also been associated with higher quantities of Demodex.

Associated factors

Skin conditions

Given their location in the hair follicles and sebaceous glands of the skin, Demodex has been associated with several skin conditions including: rosacea, (4,13) pityriasis folliculorum, (5,14,15) and pustular folliculitis. (16) However, whether Demodex is the cause of these skin conditions, or these skin conditions offer a more favourable environment for its proliferation, is unclear.

Health conditions

A higher density of Demodex has been associated with renal failure, (17,18) polycystic ovarian syndrome, (19) diabetes, (20) and immune-deficiency. (21-23) It is suggested that underlying health conditions can make an individual more susceptible to higher densities of Demodex. In adults, who will naturally have a higher density of Demodex with age, it is difficult to quantify the contribution, if any, of an underlying medical condition. However, it is unusual to see a high density of Demodex in children, and, therefore, it is likely that the immune status of the child plays a part in Demodex infestation in children.

Lifestyle

Demodex infestation appears to be higher among contact lens wearers. (24) It is thought that increased handling of the eyelids by contact lens wearers can increase the presence of bacteria at the eyelid margin, creating a more desirable environment for Demodex to reside. Demodex has also been associated with causing discomfort and ultimately contact lens drop-out in patients who were previously comfortable contact lens wearers. (25)

There is also a positive association between Demodex infestation and poor lid hygiene. It has been shown that younger individuals with poor lid hygiene are more susceptible to Demodex infestation than older individuals with good lid hygiene. (12) Furthermore, make-up has been proposed as a deterrent for Demodex infestation. (26,27) It is not clear whether the use of make-up promotes good lid and facial hygiene, or if the lipids in the cosmetics affect the growth of Demodex.

Clinical manifestation

Symptomology

Demodex infestation exhibits symptoms similar to dry eye, as they both involve the ocular adnexa and manifest on the ocular surface; dryness, itch, irritation, burning sensation and foreign body sensation have all been recorded in the literature. (7,9,10,12,28-30) While symptoms are subjective, and patients may report several, studies have found itch to be the symptom most significantly associated with Demodex infestation. (9,10,30) However, Demodex can also be found in asymptomatic individuals. (31)

Signs

Due to their location within the eyelash follicles and meibomian glands, Demodex infestation often manifests as chronic blepharitis and meibomian gland dysfunction (MGD). (1,9,29,32) The scraping movement of Demodex within the eyelash follicle causes hyperkeratinised cells to protrude from the follicle and cuff the base of the lash; this is known as cylindrical dandruff (see Figure 2), and is considered a pathognomonic sign for Demodex infestation. (33) Chronic infestation of the eyelashes can also damage the follicles leading to lash disorders such as misdirected eyelashes, trichiasis or madarosis. (29) Demodex brevis contribute to MGD by physically blocking and plugging the gland orifice, preventing the movement of lipids into the tear film. (34-37)

Untreated persistent lid margin inflammation has been shown to spread to the conjunctiva and cause blepharoconjunctivitis that can prove resistant to conventional therapies. (29) However, Demodex targeted treatment has shown the ability to reduce ocular surface inflammation and irritation, suggesting Demodex may be an underlying cause of chronic blepharoconjunctivitis. (1,7,28,29,38) Severe lid inflammation can also spread to the cornea, potentially causing various sight-threatening corneal lesions; corneal vascularisation, marginal infiltration, nodular scars and phylcentule-like lesions have been documented in patients with severe ocular Demodex infestation. (7,28)

Clinical assessment

The following clinical procedure has been recommended when examining for the presence of Demodex: (29,39)

* Clinical history: suspect the presence of Demodex in the following patients: those with persistent blepharitis, conjunctivitis, or keratitis; younger patients with a history of blepharoconjunctivitis or recurrent chalazia that appear to be resistant to conventional treatments; patients complaining of itchy eyes. Finally, remember that older patients, rosacea sufferers and contact lens wearers may be more susceptible to infestation

* Slit lamp examination: after taking a thorough clinical history, examination of the eyelids and eyelashes using a slit lamp is required. Be highly suspicious of Demodex infestation if cylindrical dandruff is present. From experience, the author would also recommend examining the lids for any signs of misdirected eyelashes, trichiasis, or madarosis, especially if there does not appear to be a significant amount of cylindrical dandruff present

* Microscopic confirmation: traditionally Demodex infestation is confirmed by removing an eyelash and counting the number of Demodex and eggs present on the epilated lash; this procedure is carried out with the slit lamp at high magnification (25-40x) and using sterile forceps to rotate the eyelash in clockwise and counter-clockwise directions.

This stimulates Demodex tails, if present, to emerge from the eyelash follicle. The lash is then epilated and placed on a microscope slide with a drop of alcohol and fluorescein, and the number of Demodex present is counted using a microscope. However, it has been noted previously that Demodex can be seen on lash manipulation without the need to epilate the eyelash. (40) From experience, the author has found that this is possible, especially in severely infested follicles (see Figure 3).

Treatment

Current treatment methods for Demodex infestation recommended by the American Academy of Optometrists and College of Optometrists are to treat with topical application of 50% tea tree oil (TTO) to the eyelids or systemically with oral ivermectin. However, TTO is toxic to the ocular surface, and it is recommended that it is only applied in-clinic by an experienced practitioner. (41,42) Ivermectin is a broad-spectrum anti-parasitic drug primarily prescribed to treat human threadworm, and control river blindness. (43) It has been associated with several adverse reactions, (44-49) and is not suitable for use by all patients. Caution is advised in the use of ivermectin by pregnant and nursing mothers, children and elderly individuals. (43) It is not known whether older individuals respond differently to younger individuals, and in general there is an increased frequency of hepatic, renal, cardiac or concomitant disease and other drug therapy in elderly patients. (43) The off-label use of ivermectin in the treatment of Demodex blepharitis has been successfully examined in clinical trials. (50-52) However, at present, systemic ivermectin is not licensed for human use in the UK and Ireland by their respective drug regulatory authorities.

There are several other options that may be considered as first choice treatments, which are discussed below.

Tea tree

TTO is an essential oil with antibacterial, antimicrobial and anti-inflammatory properties. (53-55) Terpinen-4-ol is the active ingredient in TTO effective at killing Demodex. (55) As discussed earlier, much research around the treatment of Demodex blepharitis has involved the use of TTO or tea tree-based products. A recent study has shown that Dr Organic Tea Tree face wash, which contains 38% terpinen-4-ol, is also effective at reducing signs and symptoms of Demodex among affected individuals. (31) The face wash can be administered as part of a lid scrub routine at home and can also be used on the entire face thereby theoretically treating Demodex present in hair follicles on the entire face, not just the eyelashes. Hence the use of face wash as a baseline lid hygiene regimen is recommended in susceptible individuals.

Cliradex lid wipes and foam are another tea treebased treatment available for the treatment of Demodex blepharitis. They have shown promising results in studies for improvement of signs and symptoms among Demodex blepharitis sufferers, (56) and can also be administered by practitioners for patients to use at home.

OcuSoft Lid Scrub Plus

OcuSoft Lid Scrub Plus is a treatment designed for severe blepharitis, including treatment of Demodex infestation. It is available as a wipe or a foam. It is designed to be used as a leave-on treatment overnight. A recent study examining the efficacy of OcuSoft Lid Scrub Plus for treating Demodex blepharitis found that it does help to reduce signs and symptoms in these patients. (31)

BlephEx

BlephEx is a hand-held device that is used to thoroughly scrub the eyelid margin. Its rotating tip is soaked in a lid cleaning solution of choice, and gently rubbed along the eyelid margin to remove crusting, collarettes, cylindrical dandruff and reduce the overall bacterial load on the lid margin before applying lid hygiene treatments. Patients usually notice an immediate improvement in symptoms. Using BlephEx in clinic prior to commencing home lid hygiene treatments appears to give a greater overall improvement in symptoms for patients. (31)

Conclusion

Demodex infestation is common to all optometric practices. It presents with signs and symptoms similar to dry eye, MGD, and blepharitis. Severe infestation is possible to view on the slit lamp without the need to remove the eyelashes. Demodex blepharitis can be successfully treated in practice without the need for further referral for many patients. Consider an in-house deep clean of the eyelids to begin with and advise patients on a suitable lid scrub routine for home use. Follow-up after one to two months depending on the severity of infestation is advised. In cases of chronic, severe, Demodex infestation with little to no improvement of signs and symptoms, consider referral for 50% TTO treatment and/or combined with systemic intervention.

Exam questions

Under the enhanced CET rules of the GOC, MCQs for this exam appear online at www.optometry.co.uk. Please complete online by midnight on 8 June 2018. You will be unable to submit exams after this date. Please note that when taking an exam, the MCQs may require practitioners to apply additional knowledge that has not been covered in the related CET article.

CET points will be uploaded to the GOC within 10 working days. You will then need to log into your CET portfolio by clicking on 'MyGOC' on the GOC website (www.optical.org) to confirm your points.

References

Visit www.optometry.co.uk, and click on the 'Related CET article' title to view the article and accompanying 'references' in full.

Orla Murphy is a practising optometrist and postgraduate research student at the Dublin Institute of Technology. Her areas of interest are dry eye, blepharitis and meibomian gland dysfunction. Her research involves studying the efficacy of treatments for Demodex blepharitis and meibomian gland dysfunction.

Course code: C-58845 Deadline: 8 June 2018

Learning objectives

* Be able to explain to patients about Demodex blepharitis (Group 1.2.4)

* Understand the implications of contact lens wear and Demodex blepharitis (Group 5.2.1)

* Be able to recognise the signs and symptoms of Demodex blepharitis and manage appropriately (Group 6.1.2)

* Understand the management of patients presenting with Demodex blepharitis (Group 1.1.1)

* Be able to recognise cases of Demodex blepharitis (Group 2.1.2)

* Be able to explain to patients about Demodex blepharitis (Group 1.2.4)

* Be aware of the clinical features of Demodex blepharitis (Group 8.1.1)

* Be able to explain to patients about Demodex blepharitis (Group 1.2.4)

* Understand the implications of contact lens wear and Demodex blepharitis and how to manage the patient accordingly (Group 5.4.2)

Caption: Figure 1a Several Demodex folliculorum along an epilated eyelash

Caption: Figure 1b Demodex brevis

Caption: Figure 2 Cylindrical dandruff

Caption: Figure 3 Demodex tails on eyelash manipulation
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Title Annotation:Demodex
Author:Murphy, Orla
Publication:Optometry Today
Date:May 1, 2018
Words:2184
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