THE DRY EYE

The dry eye per se is not a disease entity, but a
symptom complex occurring as a sequelae to
deficiency or abnormalities of the tear film.
Etiology
1. Aqueous tear deficiency. It is also known as
keratoconjunctivitis sicca. It is seen in conditions
like congenital alacrimia, paralytic hyposecretion,
primary and secondary Sjogren’s syndrome, Riley Day
syndrome and idiopathic hyposecretion.
2. Mucin deficiency dry eye. It occurs when goblet
cells are damaged, as in hypovitaminosis A
(xerophthalmia) and conjunctival scarring diseases
such as Stevens-Johnson syndrome, trachoma,
chemical burns, radiations and ocular pemphigoid.
3. Lipid deficiency and abnormalities. Lipid
deficiency is extremely rare. It has only been
described in some cases of congenital anhydrotic
ectodermal dysplasia along with absence of
meibomian glands. However, lipid abnormalities are
quite common in patients with chronic blepharitis and
chronic meibomitis.
4. Impaired eyelid function. It is seen in patients
with Bell’s palsy, exposure keratitis, dellen,
symblepharon, pterygium, nocturnal lagophthalmos
and ectropion.
5. Epitheliopathies. Owing to the intimate
relationship between the corneal surface and tear film,
alterations in corneal epithelium affect the stability
of tear film.
Clinical features
Symptoms suggestive of dry eye include irritation,
foreign body (sandy) sensation, feeling of dryness,
itching, non-specific ocular discomfort and
chronically sore eyes not responding to a variety of
drops instilled earlier.
Signs of dry eye include: presence of stringy mucus
and particulate matter in the tear film, lustureless
ocular surface, conjunctival xerosis, reduced or absent
marginal tear strip and corneal changes in the form of
punctate epithelial erosions and filaments.
Tear film tests
These include tear film break-up time (BUT), Schirmer-
I test, vital staining with Rose Bengal, tear levels of
lysozyme and lactoferrin, tear osmolarity and
conjunctival impression cytology. Out of these BUT,
Schirmer-I test and Rose Bengal staining are most
important and when any two of these are positive,
diagnosis of dry eye syndrome is confirmed.
1. Tear film break-up (BUT). It is the interval between
a complete blink and appearance of first randomly
distributed dry spot on the cornea. It is noted after
instilling a drop of fluorescein and examining in a
cobalt-blue light of a slit-lamp. BUT is an indicator of
adequacy of mucin component of tears. Its normal
values range from 15 to 35 seconds. Values less than
10 seconds imply an unstable tear film.
2. Schirmer-I test. It measures total tear secretions. It
is performed with the help of a 5 × 35 mm strip of
Whatman-41 filter paper which is folded 5 mm from
one end and kept in the lower fornix at the junction of
lateral one-third and medial two-thirds. The patient is
asked to look up and not to blink or close the eyes
(Fig. 15.4). After 5 minutes wetting of the filter paper
strip from the bent end is measured. Normal values of
Schirmer-I test are more than 15 mm. Values of 5-10
mm are suggestive of moderate to mild
keratoconjunctivitis sicca (KCS) and less than 5 mm
of severe KCS.
3. Rose Bengal staining. It is a very useful test for
detecting even mild cases of KCS. Depending upon
the severity of KCS three staining patterns A, B and
C have been described: ‘C’ pattern represents mild or
early cases with fine punctate stains in the
interpalpebral area; ‘B’ the moderate cases with
extensive staining; and ‘A’ the severe cases with
confluent staining of conjunctiva and cornea.
Treatment
At present, there is no cure for dry eye. The following
treatment modalities have been tried with variable
results:
1. Supplementation with tear substitutes. Artificial
tears remains the mainstay in the treatment of dry
eye. These are available as drops, ointments and slowrelease
inserts. Mostly available artificial tear drops
contain either cellulose derivatives (e.g., 0.25 to 0.7%
methyl cellulose and 0.3% hypromellose) or polyvinyl
alcohol (1.4%).
2. Topical cyclosporine (0.05%, 0.1%) is reported to
be very effective drug for dry eye in many recent
studies. It helps by reducing the cell-mediated
inflammation of the lacrimal tissue.
3. Mucolytics, such as 5 percent acetylcystine used
4 times a day help by dispersing the mucus threads
and decreasing tear viscosity.
4. Topical retinoids have recently been reported to
be useful in reversing the cellular changes (squamous
metaplasia) occurring in the conjunctiva of dry eye
patients.
5. Preservation of existing tears by reducing
evaporation and decreasing drainage.
Evaporation can be reduced by decreasing room
temperature, use of moist chambers and protective
glasses.
Punctal occlusion to decrease drainage can be
carried out by collagen implants, cynoacrylate
tissue adhesives, electrocauterisation, argon laser
occlusion and surgical occlusion to decrease the
drainage of tears in patients with very severe
dry eye