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Journal of Optometry (2018) 11, 211---222
www.journalofoptometry.org
REVIEW
The eyelash follicle features and anomalies: A review
Sarah Aumond∗, Etty Bitton
École d’optométrie, Université de Montréal, 3744 Rue Jean-Brillant, Montréal, Québec, Canada H3T 1P1
Received 31 January 2018; accepted 26 May 2018
Available online 17 July 2018
KEYWORDS
Eyelash;
Follicle;
Hair;
Eyelash
pathophysiology;
Lid margin
Abstract The primary role of eyelashes is to protect and maintain the health of the lid margin.
However, the mechanisms to fulfill this role are not fully understood. Unraveling these mech-
anisms will stand to greatly improve the efficiency of eye care professionals’ interventions in
anomalies of the eyelashes. The aim of this article is to provide a review on eyelashes includ-
ing highlights and new avenues for research; the biology of both the lash and its follicle; the
pathophysiology and management of lash anomalies by eye care professionals; and the effect of
iatrogenic factors on lashes. Using the database of Ovid MEDLINE, we reviewed studies specifi-
cally directed on human/mammalian eyelashes and key articles on current trends in scalp hair
methodologies that can be applicable to lash research. The eyelash morphology, pigmentation
and growth rate have been documented using techniques ranging from lash imaging to follicle
immunohistochemistry. Furthermore, studies have demonstrated that the lash follicle is sen-
sitive to many factors of the external environment, a variety of systemic/topical medications
and cosmetics. Recently, aerodynamic studies using a mammalian eye model confirmed that
an optimal lash length was needed so that eyelashes serve a protective role in reducing the
number of particles that can reach the eye. Despite recent advances in lash research, studies
are still scarce, due to the limited availability of the human lid for sampling. This review brings
awareness that further research is needed with respect to eyelashes and will hopefully reduce
the gap with scalp hair research.
© 2018 Spanish General Council of Optometry. Published by Elsevier Espa˜
na, S.L.U. This is an
open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-
nc-nd/4.0/).
PALABRAS CLAVE
Pesta˜
nas;
Folículo;
Pelo;
Patofisiología de las
pesta˜
nas;
Margen palpebral
Características y anomalías del folículo de la pesta˜
na: revisión
Resumen La función principal de las pesta˜
nas es proteger y mantener la salud del margen
palpebral. Sin embargo, los mecanismos de desempe˜
no de esta función no se comprenden
plenamente. Desentra˜
nar estos mecanismos ayudará a mejorar la eficiencia de las interven-
ciones de los profesionales de cuidados oculares en cuanto a las anomalías de las pesta˜
nas. El
objetivo de este artículo es aportar una revisión sobre las pesta˜
nas, incluyendo los aspectos
∗Corresponding author at: École d’optométrie, Université de Montréal, 3744 Rue Jean-Brillant, Montréal, Québec, Canada H3T 1P1.
E-mail address: sarah.aumond@umontreal.ca (S. Aumond).
https://doi.org/10.1016/j.optom.2018.05.003
1888-4296/© 2018 Spanish General Council of Optometry. Published by Elsevier Espa˜
na, S.L.U. This is an open access article under the CC
BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
212 S. Aumond, E. Bitton
más destacados y las nuevas aportaciones para la investigación, la biología de la pesta˜
na y
su folículo, la patofisiología y tratamiento de las anomalías de las pesta˜
nas por parte de los
profesionales de cuidados oculares, y el efecto de los factores iatrogénicos sobre las pesta˜
nas.
Utilizando la base de datos de Ovid MEDLINE, revisamos los estudios específicamente dirigi-
dos a las pesta˜
nas humanas/de mamíferos, así como los artículos clave sobre las tendencias
actuales en cuanto a las metodologías del cuero cabelludo, que pueden aplicarse a la inves-
tigación sobre las pesta˜
nas. Se han documentado la morfología de las pesta˜
nas, así como su
pigmentación y tasa de crecimiento, utilizando técnicas que oscilan entre la imagen de las
pesta˜
nas y la inmunohistoquímica del folículo. Además, los estudios han demostrado que el
folículo de la pesta˜
na es sensible a diversos factores del entorno externo, diversas medica-
ciones sistémicas/tópicas y cosméticos. Recientemente, los estudios aerodinámicos que han
utilizando un modelo de ojo de mamífero, han confirmado que se precisaba una longitud de
pesta˜
nas óptima para que éstas ejercieran su función protectora a la hora de reducir el número
de partículas que pueden acceder al ojo. A pesar de los avances recientes de la investigación
sobre las pesta˜
nas, los estudios son aún escasos, debido a la disponibilidad limitada de párpado
humano para muestreo. Esta revisión sirve de concienciación acerca de la necesidad de inves-
tigación futura con respecto a las pesta˜
nas, que reducirá presumiblemente la brecha existente
con respecto a la investigación sobre el cuero cabelludo.
© 2018 Spanish General Council of Optometry. Publicado por Elsevier Espa˜
na, S.L.U. Este es un
art´
ıculo Open Access bajo la licencia CC BY-NC-ND (http://creativecommons.org/licenses/by-
nc-nd/4.0/).
Introduction
Little research has been done on the human eyelash on
account that most of the attention has been directed to
research on hair for people suffering from scalp hair loss.
However, recent discoveries on the role of eyelashes and
its distinctive characteristics have led to an increased sci-
entific interest. Moreover, eyelashes are now considered an
important aspect of the facial esthetic and are the object
of various beauty treatments to enhance them.1,2 Since eye-
lashes form a barrier between the external and internal
environment of the eye, they are extremely sensitive to a
variety of threats and irritants and are highly innervated
to perform that function.3Eyelashes are an integral part of
the lid margin anatomy, much like the Meibomian glands,
eyelid skin and biofilm, each contributing to the overall
homeostasis of the ocular surface. As such, it is important
to maintain their integrity. As a whole, the lid margin is
responsible for the production of the tear film lipid layer
and the protection of the eye from external trauma. Via
the blink, it distributes the tears toward the nasolacrimal
puncta found in the inner portion of the lid margin.4If any
part of the lid margin is inflamed, it can induce a tear film
disturbance or instability which can, in turn, affect the ocu-
lar surface.5Left untreated, this inflammatory cascade can
develop into dry eye disease.5Therefore, studying the eye-
lash and its pathophysiology is valuable for researchers and
eye care professionals (ECPs) alike, to maintain ocular sur-
face homeostasis.
An Ovid MEDLINE search for eyelash physiopathol-
ogy/abnormalities/pathologies has led to 419 human and
59 non-human publications. The articles that were selected
for this non-systematic review concentrated on the general
biology of the human lash, the prevailing methods in lash
research, lash anomalies and the resulting pathologies with
their associated clinical management by an ECP. Also, we
reviewed relevant articles on current trends in scalp hair
research that can be applicable to eyelashes, and the iatro-
genic factors that can affect the lashes, such as cosmetics.
The general biology of the human lash
The human lower lid contains 75---80 lashes dispersed in
three to four rows, whereas the upper lid has 90---160 lashes
scattered on five to six rows.3,6,7 The anatomy of the lash
and hair has some similar characteristics.8Both have a hair
shaft (the visible part) that extends outside the skin, a root
that is under the skin and a bulb, which is the enlarged ter-
minal portion (Fig. 1). The inferior portion of the bulb is
in direct contact with the dermal papilla, which brings key
mesenchymal-epithelial interactions in follicle cycling.
The lash itself is made up of three structures that fit
into one another (Fig. 2).6The innermost structure, the
medulla, consists of loose cells. A thicker cortex surrounds
the medulla to ensure its strength and stability. The pigmen-
tation of either the lash or hair is the result of the melanin
contained in the cortex. Finally, the cuticle, composed of
several cell layers, forms the outermost portion, offering
protection to the internal structures by its impermeability.
The anatomy and physiology of the lash follicle are dis-
tinctive from other hair follicles. Consequently, the lash
follicle is worthy of a detailed study and appreciation of its
specific characteristics and surrounding skin; its influence
on the lash life cycle, curvature, and pigmentation; and the
age-related changes of the lashes.
The eyelash follicle features and anomalies: A review 213
Figure 1 The general morphology of the eyelash and its sur-
rounding skin.
Figure 2 The anatomy of the eyelash.
The surrounding skin of the follicle and its features
To appreciate the main characteristics of the lash follicle
and its surrounding skin, it is imperative to compare these
structures to that of the scalp hair, which have been studied
extensively. The scalp skin contains three layers: the epi-
dermis (external), the dermis (middle) and the hypodermis
(internal)8whereas the skin of the lids has two layers:
a thinner epidermis and a dermis.9All follicles on the
human body are rooted in their deepest skin layer, notably
the hypodermis for the scalp and the dermis for the lid.
Consequently, the lash follicle is shorter than the scalp hair
follicle.9Another major characteristic that distinguishes
lash follicles from scalp hair follicles is that they have no
arrector pili muscles, which are responsible for straight-
ening the hair in response to cold or intense emotions,8
producing, what is commonly referred to as ‘goose bumps’.
Therefore, lashes do not require individual mobility.3
Lash follicles are connected with two types of secretory
glands: Zeiss and Moll. They produce different substances
released through channels that flow into the follicle. The
Zeiss glands use a holocrine mechanism of action, thus lib-
erating their complete cell content, which is a sebum.10 It
has antimicrobial and lubrication properties, just as it allows
the transport of antioxidants, although the exact function
of the sebum is unknown.10 The Moll glands, only found in
the lids and active from birth, are apocrine glands that pro-
duce secretions by fragmentation from one side of their
cells.11 Their secretions, which contain a variety of sugar
components, might play a critical role in the defense against
microorganisms.11
The life cycle, curvature and pigmentation
Lashes have a life cycle consisting of three phases: the
growth phase (anagen), the degradation phase (catagen) and
the resting phase (telogen).12 Following the telogen phase,
the lash falls out and the life cycle begins again with a new
lash in the anagen phase (Fig. 3).12 The daily growth rate of
a lash is 0.12---0.14mm.7,9 The anagen phase duration varies
from four to ten weeks and the complete life cycle is from
four to eleven months.7,9,13 The lash length rarely exceeds
12 mm, as the growth rate and anagen phase duration are
shorter than the ones observed in scalp hair research.9The
lash growth rate is influenced by several factors, includ-
ing the topical prostaglandin analogs used to reduce the
intraocular pressure in glaucoma patients.13 Nesher et al.
demonstrated that the prostaglandin analog F2␣receptors
were expressed in several layers of the lash follicle during its
anagen phase.14 Further studies are needed to confirm the
expression of the prostaglandin analog F2␣receptors with
the use of prostaglandin analogs eyedrops.
The morphology of the eyelashes is such that they are
curved in all individuals, regardless of ethnicity. This cur-
vature is initiated at the bulb of the lash and continues
until the tip of the shaft.15 Thibaut et al. have shown that
several cell types of the lash follicle alongside the bulb loca-
tion are asymmetric (i.e. certain sheaths along the concave
side of the bulb are thicker than the ones on the convex
side).9While studying the biology of curly hair in vitro, the
same phenomenon of asymmetry has been observed.15 Curly
hair’s markers are also found in the cuticle and cortex of
the lash itself.9,16 These studies offer possible explanations
of the mechanisms involved in lash curvature. Nevertheless,
the amplitude of the curvature can vary among individuals.
Ethnic studies have identified a difference in the degree of
lash curvature (or curl) revealing that the lift-up and curl-up
angles are more pronounced among Caucasians as compared
to Asians.7
214 S. Aumond, E. Bitton
Figure 3 The life cycle of the eyelash.
The skin and all hair on the human body acquire their pig-
mentation mostly by melanogenesis, which is the synthesis
of different types of melanin by the melanocytes,17 these
cells being under the influence of several enzymes, includ-
ing tyrosinase-related protein 2 (TRP-2).18 When it comes
to lashes, their degree of pigmentation is defined by the
quantity of melanocytes in the lash follicle structure.9The
lash becomes grayish at a very advanced age and rarely
whitens.6The maintenance of the lash pigmentation may
be explained by a sustained expression of TRP-2.9Fur-
ther studies are needed to confirm if this association is a
direct cause-effect relationship. In contrast, many studies
have shown that scalp hair will progressively lose its pig-
mentation due to a gradual depletion of melanocytes.19
Several mechanisms have been demonstrated to explain this
phenomenon: melanocyte apoptosis, oxidative stress and a
reduced expression of certain enzymes, such as TRP-2.17,20,21
Age-related changes
There are limited studies about age-related changes on
eyelashes. Procianoy et al. have studied women’s lower
lid lashes and found that the curvature of the lashes on
the medial and central eyelid portion increased with age,
while those of the lateral portion remained in the same
direction.22 Glaser et al. reported that there was a reduc-
tion of length, thickness and pigmentation of the lashes with
age.23
Research methods
Compared to scalp hair, little research has been dedicated to
the study of eyelashes, namely due to the limitation inher-
ent to the in vivo access of the lash follicle. This section
explores the techniques employed in lash research and their
challenges.
Sampling and organ culture of the lash follicle
There are only a few studies on human lash follicle
sampling because it is limited to cadaveric studies and
eyelid surgeries, such as ectropion repairs.3,9,14 It was in
1969 that the first research on the histology and cyto-
chemistry of human lids and lashes was published.3The
function and microscopic anatomy of the follicle cells were
studied post mortem following sudden accidental deaths.
Other studies that have succeeded in preserving a por-
tion of the human lid have used immunohistochemistry to
perform analysis.9,14 This technique consists of detecting
The eyelash follicle features and anomalies: A review 215
certain antigens (proteins) in the cells of the tissue, using
antibodies that bind to them specifically. This technique
allowed researchers to describe the morphology, curvature
and pigmentation of the lash follicles,9and the presence
and characteristics of some prostaglandin receptors in the
follicles.14
As sampling on human lash follicles is limited, it is
even more complex for scientists to perform lash folli-
cle cultures, hence existing publications on that topic are
limited to animal studies. Yet, human scalp hair cultures
are common and have been successfully achieved for the
past several decades, whereby tissues are obtained dur-
ing face-lift procedures.12,24,25 A research guide has been
proposed to standardize the scalp hair follicle culture,
which is of interest to researchers in different fields:
experimental dermatology, genetics, developmental biology
and endocrinology.26 It is even possible to observe human
hair follicles in vivo with xenotransplantation (the follicles
in their anagen phase or full-thickness skin portions are
removed from the human scalp and transplanted on the
back of mice).27---29 All of these studies highlight how hair
research has progressed as compared to eyelash research.
To overcome this gap, other mammals had to be consid-
ered. In the past, primate tissues have been used due to
their resemblance with respect to anatomy and physiology.
However, animal protection laws have evolved and primates
have a restricted accessibility.30 Previous hair studies have
demonstrated that both human and porcine hair follicles are
anatomically close.31,32 Consequently, preliminary trials on
cultivated porcine lash follicles were performed as recently
as 2016, whereby follicles from pigs intended for human con-
sumption were used for organ culture assays.13 An elongation
of the follicles was obtained within a few days. Hopefully,
this study and future ones will enhance our knowledge on the
lash and help to reduce the gap between studies on lashes
and hair.
Imaging of lashes
Imaging is a minimally invasive technique to quantify var-
ious parameters of human lashes. Observational studies
with different age categories demonstrated that lashes
change with age.22,23 Characteristics such as the orienta-
tion, length, thickness and pigmentation were measured
from photographs of the lower and upper lids.22,23 Human
and mouse eyelash life cycle phases have been estimated
with photographs in several studies.7,9,13,33 However, the
measures were variable from one study to another due
to non-standardized methodologies. To improve accuracy,
Thibault et al. observed preselected lashes over a nine-
month period by measuring their length each week.9Once
again, while imaging of lashes estimates the parameters of
the life cycle, more advanced techniques described above,
such as xenotransplantation and follicle cultures, are rou-
tinely used to measure the same parameters for hair.29
Imaging techniques have also been utilized for ethnic
differences between the lashes of Caucasian and Asian
women.7Digital photographs were used to calculate the
lift-up and curl-up angles of the upper lashes and phototri-
chogram (allows in vivo study of the growth cycle)34 for the
number, length and thickness of lashes.7Smaller lash details
such as the cuticle textures and layer density were observed
ex vivo with electron microscopy.7
Study on aerodynamics
No in vivo studies of human lash aerodynamics exist to date
in the literature. Only one in vitro study exists using a model
of a mammalian eye to study the aerodynamics of particles
around eyelashes.35 The biophysics research team designed
a wind tunnel in which air flow, that could affect the ocu-
lar surface, was recreated. The model had dimensions of an
adult human eye, with a depth of 4 mm and a diameter of
20 mm, and was made with an aluminum dish. Water filled in
the dish was used to mimic the tear film and a mesh was cho-
sen to represent the lashes, after obtaining the same results
with commercially available lashes made with human hair.
Measurements of water evaporation on the ocular surface
and calculation of particle deposition on the lashes were
obtained using various mesh lengths. Optimal lash lengths
that decreased evaporation and particle deposition were
determined. Using fluid mechanic principles, the flow on the
model eye’s surface, as well as around and through lashes,
were calculated. The optimal lash length determined was
compared with other mammalian eyelash lengths, obtained
by photographs from phylogenetically diverse preserved
mammalian heads. They established that the optimal lash
length was one-third of the width of the eye. Aerodynamic
analysis confirmed that this was the optimal length, because
it reduced tear evaporation and deposition of particles on
lashes by half. Short lashes created a zone of airflow stag-
nation above the ocular surface, while long lashes pushed
the airflow toward the ocular surface. These aerodynamic
studies highlighted the important role of lashes in the pro-
tection of the eye. In vivo studies should be carried out to
validate these results on humans, but the wind tunnel effect
would most undoubtedly induce an increased frequency of
reflex blinking to protect the ocular surface. Based on this
study, any alterations of lash length, be it with certain phar-
maceuticals or cosmetic procedures (i.e. lash extensions),
would have an impact on the protective effect of the ocu-
lar surface. Further studies will be needed to validate this
impact. Although the study provided an interesting insight
into the role that lashes play in the aerodynamics at the
front surface of the eye, there remained limitations. Some
examples of those include the plane surface used in the
model, instead of a convex surface, and water as the chosen
composition to represent the tear film, which is more com-
plex in mammals. Studying the protective role of lashes was
unexplored before this study, and the authors have paved
the way for future investigations in the aerodynamic role of
in vivo human lashes.
Pathophysiology of the lashes and their
management
Definitions of lash anomalies
During an evaluation of the anterior segment of the
eye, ECPs need to assess the normalcy of several struc-
tures including eyelashes. There are several terms in the
216 S. Aumond, E. Bitton
Table 1 Hair anomalies and their associated pathologies.
Anomaly Pathological condition Lashes only Description
Pigmentation Poliosis Decreased/absence of pigmentation in hair from
any area of the body,36 by decreased/absence of
melanin and/or hair follicle melanocytes37
Direction and
position
Primary trichiasis: misdirected lash, by
misdirection of the hair shaft38
Trichiasis X Secondary trichiasis: secondary to entropion,
normal orientation of the hair shaft38
Distichiasis X Abnormal row of lashes near or in the Meibomian
glands; rare condition39
Growth
Hypotrichosis Reduced hair density in any area of the body40
Milphosis X Lash loss41
Madarosis Lash and/or eyebrow loss41
Mixed Hypertrichosis An increased of hair in any area of the body,
beyond the normal variation for age, sex or race42
Trichomegaly Increased lash (>12 mm) and/or eyebrow length,
curl, stiffness, pigmentation and thickness43---45
literature that define anomalies of hair anywhere on the
body, however some are specific for eyelashes. Table 1
summarizes the different types of hair anomalies and their
associated pathologies.
There is a consensus on most definitions on eye-
lash anomalies with the exception of hypertrichosis and
trichomegaly. The term hypertrichosis is commonly mis-
interpreted as a synonym for trichomegaly, even though
they have distinct definitions. Hypertrichosis is defined as
an increase in hair in any part of the body, whereas tri-
chomegaly is specific for eyelashes and eyebrows.43---45 The
definitions of hypertrichosis and trichomegaly adopted for
this review reflect the ones used in recent publications.43---45
Also, the terms madarosis and milphosis are often con-
founded. In a clinical setting, the term madarosis is used
to describe lash loss, however milphosis is the more appro-
priate term.
Management of lash anomalies
The etiology and management of poliosis, trichiasis, milpho-
sis and trichomegaly have been summarized from the
written literature, mainly from case reports (Table 2).
Depending on the etiology, a single pathology or several lash
pathologies may be present simultaneously. As a result of
the lack of substantive clinical trials on lash pathologies,
Table 2 emphasizes the most frequently reported manage-
ment strategies, and as such, is non-exhaustive.
It is essential for ECPs to first determine the etiology
of the lash pathology to select the appropriate manage-
ment. In the particular case of milphosis without a clear
etiology, ECPs must consider a psychiatric disorder called
trichotillomania as a possible causal factor, regardless of the
concomitance of eyebrow and/or hair madarosis. Trichotil-
lomania is characterized by an uncontrollable urge to pull
out hair from any part of the body73 and a referral for a psy-
chological evaluation should be considered. This condition
can be managed by investigating the cause of the behavior
and, in some cases, pharmacotherapy is recommended.74
The etiology of the lash pathology also affects the
appearance of the lashes, which may affect the patient’s
esthetic appearance. For example, common causes of tri-
chomegaly, such as HIV infection and allergic rhinitis, will
induce the regrowth of long and smooth lashes, while epi-
dermal growth factor receptor (EGFR) inhibitors make them
rougher and more dispersed.44 The appearance of eyelashes
also has a major impact on the quality of life, as hair
loss can cause various degrees of psychological distress.75
Dunnill et al. have demonstrated that the most distressing
side effect of chemotherapy is the loss of hair.76 Other sys-
temic diseases that induce hair loss can be stressful for the
affected person, such as alopecia areata, which is characte-
rized by a patchy loss of scalp hair. This disease can progress
to other parts of the body, including eyelashes.77 Although
the exact pathophysiological mechanism is not established
yet, it is thought to be caused by an autoimmune attack
on hair follicles.78 Patients with alopecia areata have poor
health-related quality life scores similar to what is estab-
lished in other chronic skin diseases, as demonstrated in two
systematic studies.77,79
As seen in Table 2, the management of lash patholo-
gies will be influenced by their causal agent. When the lash
pathology severity ranges from mild to moderate, this can
be managed by an ECP in most cases. To date, there is
only one pharmaceutical option approved for eyelash loss
(lash hypotrichosis), consisting of a topical application of
bimatoprost ophthalmic solution 0.03% (Latisse, Allergan)
along the superior lash base. Its mode of action is to prolong
the anagen phase of the lash life cycle,65 hence resulting in
an increased lash length, thickness and pigmentation.65---68
Before using this product, patients should always seek the
advice of an ECP. If adverse events occur, such as discom-
fort and skin pigmentation, discontinuation of the product
will typically reverse the effects. Some cases of poliosis
have been reported following prostaglandin analogs use.51
The eyelash follicle features and anomalies: A review 217
Table 2 Etiologies and management of lash conditions.
Pathological condition Etiology Management
Poliosis
Congenital syndromes46 No medication approved to restore lash pigmentation
Acquired conditions36,47---49:melanocytic
lesions, inflammatory systemic disorders,
blepharitis and vernal keratoconjunctivitis
(VKC)
If ophthalmic-related: treat underlying etiology54 with
results varying from no change to full recovery of the
pigmentation47,51,53
Less common: systemic/ophthalmic
drug-induced (side effect of all topical
prostaglandin analogs)50---53
If systemic implication54:referred to the patient’s
primary care doctor
Trichiasis
Ophthalmic39:lid margin scars from
trauma/surgery; lid margin inflammation;
conjunctival diseases; conjunctival burns
Initial episode: epilation of the affected lash(es) and
soft contact lenses for short-term relief of induced
conjunctival or corneal irritation55
Various skin diseases39 Recurrent episode: refer to an ophthalmologist for an
ablation procedure (depends on the severity): laser
argon ablation,56,57 electrolysis,58 trephination,59 direct
internal lash bulb extirpation,38 folliculectomy,60
cryotherapy,61 entropion surgery62
If skin disease suspected: refer to a dermatologist
Milphosis
(loss of
lashes)
Ophthalmic41:lid infestation (staphylococcal
spp.,Demodex folliculorum, trachoma) and/or
lid inflammation (posterior blepharitis, ocular
rosacea, seborrheic blepharitis)
Reversible follicle damage64:lash(es) regrowth
possible; consider pharmaceutical approach to increase
the regrowth rate (bimatoprost ophthalmic solution
0.03% is the only approved drug in patients with healthy
lashes and hypotrichosis)65---68
Associated with eyebrow madarosis63:
several dermatological diseases and inherited
conditions
Irreversible follicle damage: no lash regrowth
Associated with eyebrow and hair
madarosis63:Extensive list of systemic and
drug-induced conditions
Severe irreversible milphosis: refer to an oculoplastic
surgeon for lash grafting consideration63
Trichomegaly
Congenital syndromes69:(Oliver-McFarlane
and Cornelia de Lange)
Trimming of the affected lashes if visual disturbance or
smudging with inner surface of eyeglass lens70---72
Familial With concomitant trichiasis55:refer to trichiasis
management (above)
Acquired44:Allergic rhinitis, atopic dermatitis,
HIV infection, uveitis and VKC
Drug-induced44:Topical prostaglandin analogs
and epidermal growth factor receptor (EGFR)
inhibitors used in oncology
To date, there is no medication approved to restore the
pigmentation of lashes.
Severe lash pathologies must be referred to special-
ists for an ablation procedure,57---60 eyelash grafts,63 lid
reconstruction80,81 or systemic therapies.78 Promising ther-
apies are emerging for hair loss, which can lead to
the discovery of new treatments for eyelashes specifi-
cally. Dainichi and Kabashima have reviewed all current
therapies and treatments that have an effect on hair
regrowth in alopecia areata and universalis (subtype of
alopecia that also affect the lashes).78 In alopecia univer-
salis, hair regrowth has been observed with medications
such as topical immunotherapy and corticosteroids.78 How-
ever, these studies focused on scalp hair regrowth and
did not collect data on the regrowth rate of lashes. Data
from scalp hair studies may guide future therapies for
eyelashes.
Lid margin microflora
The inherent microflora of the lid margin also plays a
vital role in maintaining the lashes free of anomalies.
The lid margin typically contains a microflora composed
of commensal bacteria and parasites. A disruption of the
balance of this microflora can lead to various types of
blepharitis.82 Lee et al. have demonstrated that the most
common bacteria found in lash samples were Propionibac-
terium,Staphylococcus,Streptophyta,Corynebacterium
and Enhydrobacter.83 The variety of the lash microflora is
unique to each individual. The study further highlighted
that when blepharitis was diagnosed, Staphylococcus,
Streptophyta,Corynebacterium, and Enhydrobacter were
increased whereas Propionibacterium was decreased. Due
to the constant contact of the lids with the ambient air, the
lid microflora is particularly influenced by environmental
218 S. Aumond, E. Bitton
factors, such as pollen, dust, and soil particles. Further-
more, touching our lids with our fingers can inoculate other
varieties of the microflora, contributing to the dynamic
nature of the lid margin microflora.
Bacterial overpopulation can be observed clinically with
the presence of debris on the lashes. Acute Staphylococ-
cal blepharitis is identified with collarettes, which are
hard crusts on lashes, and with other non-specific signs
(squame/scale, telangiectasia vessels, Meibomian gland
dysfunction).84 Chronic signs are madarosis, trichiasis, polio-
sis, tylosis or scars on the lid margin.82,84 Blepharitis can
also be caused by other micro-organisms, such as para-
sites. Three types of parasites, all arthropods, can inhabit
the lid margin: Demodex folliculorum,Demodex brevis and
Phthirus pubis.85 Demodex parasites are part of the natu-
ral eye microflora82 and their number increases with age,
so much so that one study has reported 100% prevalence in
people over 70 years old.86 D. folliculorum is mostly found
in the lash follicle and other parts of the body such as
eyebrows, scalp, nose and ears. D. brevis is found mainly
in the Meibomian glands and other sebaceous glands, such
as the face.87 The anatomy of the Demodex parasite con-
sists of a head with four pairs of legs on either side and
an elongated body/tail that contains the digestive system.
The parasite has no anus, hence all the ingested material
remains in the gut, along with its own microflora of Strep-
tococcus spp., Staphylococcus spp. and Bacillus oleronius.88
At the end of its life cycle, approximately 15---18 days in
length, the parasite bursts and releases its content, which
can provoke an inflammatory response.87,88 An overpopula-
tion of the parasite is called a demodicosis, and on the lids,
this would be termed blepharitis secondary to Demodex.
Since Demodex has the potential to affect both the anterior
(lashes) and posterior (Meibomian glands) portion of the lid
margin, some89 have proposed the term marginal blephari-
tis to describe a demodicosis of the lid margin. Clinical signs
of demodicosis include follicular hypertrophy,87 gelatinous
debris surrounding the base of the lashes termed cylindri-
cal dandruff,90 and non-specific blepharitis signs as stated
above. Cylindrical dandruff is a pathognomonic sign for
Demodex.90 On the other hand, the parasite Phthirus pubis
is not found in the normal lid microflora, as it originates in
pubic hair. It can be transmitted by sexual contact and less
often through linens and bedding.91 Transfer of the parasite
from the infested region to the hand can reach any hair on
the body, including the eyelashes.92 The resulting blepharitis
is termed Phthiriasis palpebrarum and its clinical presenta-
tion, in one or both eyes, includes the translucent parasite’s
body firmly attached to lashes, brown scales corresponding
to the parasite’s feces, and multiple nits (unhatched para-
sites) fixed on the lashes and the lid margin.91,92 Symptoms
include itchiness and irritation of the lid margin.91
Finally, blepharitis can be the result of seborrheic der-
matitis, a dermatological condition affecting the skin and
in some cases, the lid margin. Many etiologies have been
proposed and researchers are still looking for the exact
mechanism.93 An imbalance in the skin micro-organisms
might be the cause.93 Other than the non-specific signs of
blepharitis detailed above, ECPs can observe some flaky
scales on the lids that can fall on the lashes.94 When the
condition affects the anterior portion of the lid, it is called
seborrheic blepharitis.
Management of anterior blepharitis
The aim in blepharitis management is to restore the normal
microflora.95 A complete eradication of Phthiriasis palpe-
brarum is desired and can be achieved by mechanical
removal of the parasites and nits.85,96 Blepharitis secondary
to the imbalance of the microflora are chronic conditions.
Hence, they are not expected to be completely eradicated.
First line therapies of blepharitis include warm compresses
to soften the debris and eyelid hygiene to manually dis-
lodge them.97 Targeted lid margin therapies should be
adopted by ECPs, including antibacterial for Staphylococcal
infestation87 and anti-parasitic formulations for Demodex
parasites,98,99 in order to limit lid margin anomalies that
come with chronic blepharitis. To target properly sebor-
rheic blepharitis, a reference to dermatology is required to
establish the diagnosis of seborrheic dermatitis and treat
the affected skin with the appropriate pharmaceutical.93
ECP assessment of lashes
Fig. 4 summarizes in a flowchart the management of debris
on eyelashes. This tool can be used when teaching students
or residents to identify and localize debris on lashes and
select the appropriate management.
Iatrogenic factors
The appearance of eyelashes is an increasingly growing pre-
occupation in many people who are seeking an esthetic
enhancement. Cosmetics have been used since biblical times
to improve the esthetic of the eye and the thickness, length
and color of eyelashes.100 Lash tints and extensions are
newer and popular, surpassing expectations in the cosmetic
marketplace. Over $55 million in 2014 were dedicated to
eyelash extension and adhesives alone in the US.101 Syn-
thetic lashes are glued individually on the natural lashes
with different adhesives, which have been linked to ocu-
lar problems such as keratoconjunctivitis.102 In most cases,
the glue and removing agents have induced inflammation
on the eye, by direct contact with the ocular surface. Fur-
thermore, the vapors associated with the application, or
the dissolving, of the glue afterwards have been reported
as ocular irritants. Lash tinting is done with dyes that con-
tain p-phenylenediamine, a sensitizer that can provoke an
allergic reaction and contact dermatitis.103,104 Water-based
mascara is made of several waxes, types of pigment and
resins dissolved in water, whereas solvent-based mascara,
known as waterproof, has its pigments and waxes added
in petroleum distillates.100 Fukami et al. found a positive
correlation between the frequency of mascara use and the
degree of cracking in the lash cuticles.105 Also, long-term
use of mascara led to milphosis, possibly due to the rub-
bing, with fingers and water only, by the users.106 Needless
to say, eye cosmetics in general can have an impact on the
lids, lashes, tear film and ocular surface.107 Consequently,
patients need to be educated appropriately about the appli-
cation, removal, shelf life and associated precautions of
cosmetic use.
The eyelash follicle features and anomalies: A review 219
Figure 4 Eyelash debris assessment by eyecare professionals.
Conclusion
This review brings a deeper awareness on the eyelashes
and their follicles. The current literature has numerous
cases of how lashes are affected by systemic/eye diseases,
pharmaceuticals and cosmetics, and how they change the
lash morphology. In addition, an imbalance of the lash
microenvironment can lead to a variety of blepharitis and
impact negatively the adjoining lid margin. Many studies
have demonstrated that lashes do not serve only a cosmetic
function, but also a protective role on the lid margin and
the ocular surface. The lash follicle structures are mostly
studied with ex vivo techniques, which are limited by the
poor availability of the human lid sampling. This review fur-
ther highlights the challenges when studying the lash follicle
and the need to develop newer techniques. Increasing lash
research will certainly improve the efficiency of ECP’s inter-
ventions in lash anomalies.
220 S. Aumond, E. Bitton
Funding
This research did not receive any specific grant from funding
agencies in the public, commercial, or not-for-profit sectors.
Conflicts of interest
SA has received honorarium for conferences/consulting from
Allergan and Shire. EB has received funding from Alcon,
Allergan, Canadian Optometric Trust Fund, I-Med Pharma
Inc, Shire and honorarium for conferences/consulting from
Akorn, Alcon, Allergan, American Academy of Optometry,
Canadian Association of Optometry, CooperVision, Labti-
cian, Jobson Publishing, Novartis, Santen, Shire.
Acknowledgement
A special thanks to Micheline Gloin for her graphic assis-
tance.
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