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Fifth stage
OPHTHALMOLOGY
Chapter-6
د
.
ﻧزار
28/11/2016
"The
lacrimal
system"
INTRODUCTION
Disorders of the lacrimal system are common and may produce chronic symptoms with a
significant morbidity .The lacrimal glands normally produce about 1.2 µl of tears per
minute .Some are lost via evaporation .The remainder are drained via the naso-lacrimal
system .The tear film is reformed with every blink .
Abnormalities are found in :
tear composition ؛
the drainage of tears
ABNORMALITIES IN COMPOSITION
If certain components of the tear film are deficient or there is a disorder of eyelid
apposition then there can be a disorder of ocular wetting .
Aqueous insufficiency—dry eye:
A deficiency of lacrimal secretion occurs with age and results in keratoconjunctivitis
sicca
(
KCS)
or dry eyes .When this deficiency is associated with a dry mouth and dryness of
other mucous membranes the condition is called primary Sjögren’s
syndrome
( an auto-
immune exocrinopathy .
) When KCS is associated with an auto-immune connective tissue
disorder the condition is called secondary Sjögren’s syndrome .Rheumatoid arthritis is
the commonest of these associated disorders .
SYMPTOMS
non-specific symptoms of burning ،photophobia ،heaviness of the lids and ocular fatigue .
These symptoms are worse in the evening because the eyes dry during the day .In more
severe cases visual acuity may be reduced by corneal damage.
SIGNS
In mild cases there are few obvious signs. Staining of the eye with fluorescein will show
small dots of fluorescence
(
punctate
staining )
over the exposed corneal and conjunctival
surface. In severe cases tags of abnormal mucus may attach to the corneal surface
(filamentary
keratitis)causing pain due to tugging on these filaments during blinking.
TREATMENT
Supplementation of the tears with tear substitutes helps to reduce symptoms and a
humid environment around the eyes can be created with shielded spectacles .In severe
cases it may be necessary to occlude the punta with plugs ،or more permanently with
surgery ،to conserve the tears .
PROGNOSIS
Mild disease usually responds to artificial tears .Severe disease such as that in
rheumatoid Sjögren’s can be very difficult to treat .
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Inadequate mucus production
Destruction of the goblet cells occurs in most forms of dry eye ،but particularly in
cicatricial conjunctival disorders such as erythema multi -
forme
( Stevens–Johnson’s
syndrome). In this there is an acute episode of inflammation causing macular
‘target ‘lesions on the skin and discharging lesions on the eye ،mouth and vulva .In
the eye this causes conjunctival shrinkage with adhesions forming between the
globe and the conjunctiva (Symblepharon).
There may be both an aqueous and mucin deficiency and problems due to lid
deformity and trichiasis .Chemical burns of the eye ،particularly by alkalis and
(trachoma
) chronic inflammation of the conjunc -
tiva caused by a type of
chlamydial infection; see Chapter7
، may also have a similar end result .
The symptoms are similar to those seen with an aqueous deficiency .Examination
may reveal scarred ،abnormal conjunctiva and areas of fluorescein staining .
Treatment requires the application of artificial lubricants .
Vitamin A deficiency
( xerophthalmia )
is a condition causing childhood blindness on
a worldwide scale .It is associated with generalized malnutrition in countries such as
India and Pakistan .Goblet cells are lost from the conjunctiva and the ocular surface
becomes keratinized
( xerosis )
.An aqueous deficiency may also occur .The
characteristic corneal melting and perforation which occurs in this condition
(
keratomalacia )
may be prevented by early treatment with vitamin A .
Abnormal or inadequate production of meibomian oil
Absence of the oil layer causes tear film instability ،associated with (
blepharitis
)
Malposition of the eyelid margins
If the lid is not apposed to the eye
( ectropion )
or there is insufficient closure of the
eyes e.g. in a seventh nerve palsy or if the eye protrudes (proptosis)
(as in dysthyroid eye disease) the preocular tear film will not form adequately .
Correction of the lid deformity is the best answer to the problem .If the defect is
temporary, artificial tears and lubricants can be applied .If lid closure is inadequate
a temporary ptosis can be induced with a local injection of botulinum toxin into the
levator muscle .A more permanent result can be obtained by suturing together part
of the apposed margins of the upper and lower lids
) e.g .lateral
tarsorrhaphy .
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DISORDERS OF TEAR DRAINAGE
When tear production exceeds the capacity of the drainage system ،excess tears overflow
onto the cheeks .It may be caused by :
o irritation of the ocular surface ،e.g .by a corneal foreign body ،infection or
blepharitis ؛
o occlusion of any part of the drainage system when the tearing is termed (epiphora)
Obstruction of tear drainage (infant )
The naso-lacrimal system develops as a solid cord which subsequently canalizes and is
patent just before term .Congenital obstruction of the duct is common .The distal end of
the naso-lacrimal duct may remain imperforate ،causing a watering eye .If the canaliculi
also become partly obstructed the non-draining pool of tears in the sac may become
infected and accumulate as a mucocoele
or cause dacrocystitis .Diagnostically the
discharge may be expressed from the puncta by pressure over the lacrimal sac .The
conjunctiva ،however ،is not inflamed .Most obstructions resolve spontaneously in the
first year of life .If epiphora persists beyond this time ،patency can be achieved by
passing a probe via the punctum through the naso-lacrimal duct to perforate the
occluding membrane
(
probing )
.A general anaesthetic is required .
Obstruction of tear drainage (adult)
The tear drainage system may become blocked at any point ،although the most
common site is the naso-lacrimal duct .Causes include infection or direct trauma
to the naso-lacrimal system .
HISTORY
The patient complains of a watering eye sometimes associated with stickiness .The
eye is white .Symptoms may be worse in the wind or in cold weather .There may
be a history of previous trauma or infection .
SIGNS
A stenosed punctum may be apparent on slit lamp examination .Epiphora is unusual if
one punctum continues to drain .Acquired obstruction beyond the punctum is diagnosed
by syringing the naso-lacrimal system with saline using a fine cannula inserted into a
canaliculus .A patent system is indicated when the patient tastes the saline as it reaches
the pharynx .If there is an obstruction of the naso-lacrimal duct then fluid will regurgitate
from the non-canulated punctum .The exact location of the obstruction can be
confirmed by injecting a radio-opaque dye into the naso-lacrimal system
(dacrocystogram) X-rays are then used to follow the passage of the dye through the
system .
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TREATMENT
It is important to exclude other ocular disease that may contribute to watering such as
blepharitis .Repair of the occluded naso-lacrimal duct requires surgery to connect the
mucosal surface of the lacrimal sac to the nasal mucosa by removing the intervening bone
)dacryocystorrhinostomy
or
DCR .The operation can be performed through an incision on
the side of the nose but it may also be performed endoscopically through the nasal
passages thus avoiding a scar on the face .
INFECTIONS OF THE NASO-LACRIMAL SYSTEM
Closed obstruction of the drainage system predisposes to infection of the sac
(dacryocystitis
) The organism involved is usually Staphylococcus .Patients present with a
painful swelling on the medial side of the orbit ،which is the enlarged, infected sac .
Treatment is with systemic antibiotics .A mucocoele
results from a collection of mucus in
an obstructed sac ،it is not infected .In either case a DCR may be necessary to prevent
recurrence .