The definition of dry eyes is complex and
reveals the lack of consensus amongst authors. It is sometimes called dry eye
syndrome (but also, keratitis [or keratoconjonctivitis] sicca [KCS],
xerophthalmia, etc) which means that it concerns a group of symptons
related to a deficit of hydration or lubrication of the eye without defining its
exact cause. This somehow reveals that the mechanisms causing dry eyes are still
unknown and most certainly understudied. One of the most complete
definition we have found on this disease is:
The ocular surface, the principal and
accessory lachrymal glands, the meibomius glands et the neural connections that
interconnect them, form a functional unit working together. The dysfunction of
one of those structures is revealed by the inadaquate volume or/and the
lacrhrymal composition necessary to repair the numerous damages caused by the
multiple agressions eyes are constantly submited to, whihc include
the action of microorganism ou the simple action of blinking (Stern
et Al).
According to Murube (a famous Spanish
ophthalomogist) the most adequate of definition of dry eye syndrome is the
"inadequecy between the quality and the composition of the tears and the needs
of the ocular surface". This authors suggests, among other things, to replace
the dry eye term by "lachrymal dysfunction".
According to other authors is a perturbation
associated to a lachrymal production deficiency and/or the excess of evaporation
causing ocular discomfort and damages, in particular in the lid slit area (Lemp
& Al). Some other authors add that the damages may extend beyond the ocular
inter-palpebral surface towards the upper part of the globe and the the
lachrymal instability by itlself is sufficient to establish a dry eye
diagnostic, even in the absence of ocular surface damage.
Recently, a
delphi panel of ophtalmology
specialists decided to replace the term dry eye by DTS or dysfunctional tear
syndrome. Curiously enough is
very close to the term we [Keratos] decided to use two years and a half
ago of lachrymal (=tearfilm) dysfunctions. Let's consider that we have
read the appropriate authors and that we don't always repeat nonsense ;-)
Honestly, this DTS term does not
cover all aspects of a dry eye state and notably the neurological and
lid aspect (except for the glands inlcuded in the tearfilm notion).
Thus, we may consider that the difficulyt to name this syndrome only
reveals the complexity of this pahtology. Nevertheless this new term,
englobes one important notion: dry eyes are not just the result of poor
quantity of tears but most frequenty the result of a poor qaulity of
tears, even toxic, irritanting and inflammatory tears, which increase
evaporation and pain.
Anyway, now that this awful syndrome
is better named, we expect (hope) that it will receive more attention,
it will be better studied and most important better treated than
currently.
