Dry eyedisease compounds…
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more tear components (7). Tear film forms amoist natural barrier separating eye
from the external media. This consistent film is formed mainly from a triplet of
aqueous, mucous, and lipid layers providing the necessary equilibrium for the
healthymaintenance of the ocular surface (Figure 1). Themain functions of this
film are: lubrication of the ocular surface, transfer of nutritional elements to the
cornea, elimination of foreignmatter and cellular debris generated on the ocular
surfaceby the tear flowand theblinkprocess, andactingas the first lineof defense
against ocular surface infections
(8). Insome cases, the imbalance
of the tear filmcomposite layers
leads to reduced tear secretion,
exposure of the eye surface,
dryness and damage of the
surface cells (6). The imbalance
of the composite layers could be
caused by Sjögren’s syndrome
tear secretion deficiency and/or
tear film instability due to the
use of contact lenses (6, 9, 10).
Dry eye syndrome types are classified according to etiologic perspectives and
environmental influences as: aqueous deficient dry eye (ADDE) and evaporative-‐
tear dry eye (EDE) (6, 11). ADDE is divided to: related to Sjögren’s syndrome
(primary and secondary) and non-‐related to Sjögren’s syndrome conditions
(lacrimal disease, lacrimal obstructionandmalfunctioningblinkingreflex) (6). EDE
conditions are: oil deficient, lid related and caused by an ocular surface alteration
(6). Signs and symptoms of these complications can vary frompatient to patient,
sometimes with little or no correlation between them, even though they are
generally related to the tear film composition. The signs and symptoms could
include keratitis, conjunctival and corneal staining, redness, blurry vision,
decreased tear film break-‐up time, decreased tear production, volume, and flow,
increased conjunctival redness, excess debris in the tear film, ocular dryness,
ocular grittiness, ocular burning, foreignbody sensation in the eye, excess tearing,
photophobia, ocular stinging, refractive impairment, ocular sensitivity, and ocular
irritation(12, 13).
The clinical diagnosis of dry eye is challenging since dry eye is a pathology
characterized by an extensive variety of signs and symptoms, mentioned above,
related toocular dryness and the ambiguity in the etiologyandpathophysiologyof
Figure1.-‐
Tear filmlayers.
