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probably multifactorial (Dougherty and McCulley 1984, Oto et al. 1998).
The treatment is prolonged and recurrences are common.
ANATOMY
The eyelid margin is divided in anterior and posterior portions by the
grey line that represents the marginal region of the orbicularis muscle seen
through the skin ( Fig. 1 ). The Meibomian glands are arranged in parallel in a
single row throughout the length of the tarsal plate. The number of separate
glands in the upper lid varies from 25 to 40 and in the lower lid from 20
to 30 (Knop et al. 2011). The ducts of the Meibomian glands open onto the
lid margin posterior to the grey line and anterior to the mucocutaneous
junction. The secretion of the glands is controlled by neural and hormonal
factors. The delivery of the secretion is related to the mechanical action of
the lid muscles during blinking.
Figure 1 The eyelid margin is subdivided in anterior and posterior by the grey line.
Color image of this figure appears in the color plate section at the end of the topic.
Meibomian secretion forms the superfi cial layer of the tear fi lm and
is responsible for stabilizing and protecting it against evaporation and
outfl ow. It lubricates the lid margins avoiding maceration when in contact
with the tear fi lm, protects against contamination and provides a regular
optical surface at the cornea.
TERMINOLOGY
The term blepharitis refers to infl ammation of the lid as a whole ( Fig. 2 ).
Marginal blepharitis is infl ammation of the lid margin and includes anterior
and posterior blepharitis. Anterior blepharitis describes infl ammation of
the margin anterior to the grey line and posterior blepharitis describes
 
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