lacrimal system anatomy and clinical
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Transcript of lacrimal system anatomy and clinical
The lacrimal system Done by:
Mohammed A Qazzaz
the lacrimal glands normallyproduce about 1.2 l 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.INTRODUCTION
Abnormalities are found in:tear composition.the drainage of tears.
ABNORMALITIES IN COMPOSITIONIf 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 insufficiencydry eyeA deficiency of lacrimal secretion occurs with age and results in keratoconjunctivitis sicca (KCS) or dry eyes..
When this deficiency is associated with adry mouth and dryness of other mucous membranes the condition is called primary Sjgrens syndrome When KCS is associated with an auto-immune connective tissue disorder the condition is called secondary Sjgrens syndrome. Rheumatoid arthritis is the commonest of these associated disorders
SYMPTOMSPatients have non-specific symptoms of grittiness, burning, photophobia,heaviness of the lids and ocular fatigue. These symptoms are worse in theevening because the eyes dry during the day. In more severe cases visual acuity may be reduced by corneal damage.
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
TREATMENT1- Supplementation of the tears with tear substitutes helps to reduce symptoms. 2-In severe cases it may be necessary to occlude the punta with plugs, or more permanently with surgery, to conserve thetears.
Inadequate mucus production
Destruction of the goblet cells occurs in most forms of dry eye, but particularly in cicatricial conjunctival disorders such as erythema multiforme(StevensJohnsons syndrome)
StevensJohnsons syndrome).there is an acute episode ofinflammation causing macular target lesions on the skin and discharginglesions on the eye, mouth and vulva. In the eye this causes conjunctivalshrinkage with adhesions forming between the globe and the conjunctiva (symblepharon).
There may be both an aqueous and mucin deficiency andproblems due to lid deformity and trichiasis.
1-Chemical burns of the eye,particularly by alkalis 2- trachoma (chronic inflammation of the conjunctivacaused by a type of chlamydial infection;
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 childhoodblindness on a worldwide scale. It is associated with generalized malnutritionin countries such as India and Pakistan. Goblet cells are lost fromthe conjunctiva and the ocular surface becomes keratinized (xerosis). Anaqueous deficiency may also occur. The characteristic corneal melting and perforation which occurs in this condition (keratomalacia) may beprevented by early treatment with vitamin A.
Abnormal or inadequate production of meibomian oilAbsence of the oil layer causes tear film instability, associated withblepharitis
Malposition of the eyelid marginsIf 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 notform adequately
Correction of the lid deformity is the best answer to theproblem. If the defect is temporary, artificial tears and lubricants can beapplied. If lid closure is inadequate a temporary ptosis can be induced witha local injection of botulinum toxin into the levator muscle. A more permanentresult can be obtained by suturing together part of the apposedmargins of the upper and lower lids (e.g. lateral tarsorrhaphy;
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:00irritation of the ocular surface, e.g. by a corneal foreign body, infectionor blepharitis;00occlusion of any part of the drainage system (when the tearing istermed epiphora).
Obstruction of tear drainage (infant)The naso-lacrimal system develops as a solid cord which subsequentlycanalizes and is patent just before term. Congenital obstruction of theduct is common. The distal end of the naso-lacrimal duct may remainimperforate, causing a watering eye. If the canaliculi also become partlyobstructed the non-draining pool of tears in the sac may become infectedand accumulate as a mucocoele or cause dacrocystitis.
Diagnostically thedischarge may be expressed from the puncta by pressure over thelacrimal sac. The conjunctiva, however, is not inflamed. Most obstructionsresolve spontaneously in the first year of life. If epiphora persists beyondthis time, patency can be achieved by passing a probe via the punctumthrough 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 themost common site is the naso-lacrimal duct. Causes include infection ordirect trauma to the naso-lacrimal system.
The patient complains of a watering eye sometimes associated withstickiness. The eye is white. Symptoms may be worse in the wind or incold weather.There may be a history of previous trauma or infection.
SIGNSA stenosed punctum may be apparent on slit lamp examination. Epiphorais unusual if one punctum continues to drain.
Acquired obstructionbeyond the punctum is diagnosed by syringing the naso-lacrimal systemwith 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. Ifthere is an obstruction of the naso-lacrimal duct then fluid will regurgitatefrom the non-canulated punctum. The exact location of the obstructioncan be confirmed by injecting a radio-opaque dye into the naso-lacrimalsystem (dacrocystogram); X-rays are then used to follow the passage of thedye through the system.
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 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 SYSTEMClosed obstruction of the drainage system predisposes to infectionof the sac (dacryocystitis; Fig. 6.4). The organism involved is usuallyStaphylococcus. Patients present with a painful swelling on the medial sideof the orbit, which is the enlarged, infected sac.Treatment is with systemicantibiotics.A mucocoele results from a collection of mucus in anobstructed sac, it is not infected. In either case a DCR may be necessaryto prevent recurrence.