; occasionally there is a ring of brown pigment surrounding puncta; rabbit has lower punctum only.
Anatomy and Physiology
Secretory
Lacrimal gland
Accessory lacrimal glands
Gland of the third eyelid
Goblet cells
Meibomian glands
Precorneal tear film
Drainage
Diagnostic Procedures
Fluorescein test
Lavage of the drainage system
Schirmer tear test
Dacryocystorhinography
Nasolacrimal Abnormalities
Abnormalities associated with drainage
Imperforate punctum
Atresia of nasolacrimal duct or canaliculi
Physiologic epiphora
Dacryocystitis
Nasal obstruction
Eyelids
Abnormalities associated with secretion
Acute dacryoadenitis
Chronic dacryoadenopathy (lacrimal atrophy)
Neoplasia
Located beneath conjunctiva between supraorbital process and dorsolateral surface of eyeball - has several short ducts that open into conjunctiva near fornix - innervated by trigeminal nerve (sensory) and nervous intermedius (motor - parasympathetic).
Present in the conjunctiva at various locations, especially the fornix.
Subconjunctivally on bulbar and palpebral surface of third eyelid - has many small ducts.
In conjunctiva - produce mucus (Moore, et al.).
Produce sebaceous secretion; located in upper and lower eyelids; ducts open onto eyelid margins.
Contributed to by all the above.
The tear film is complex and cannot be replaced artificially if it is inadequate or absent - however, satisfactory use of so-called artificial tears is possible.
Meibomian contribution is the outer layer; it retards evaporation.
Serous portion (from lacrimal, third eyelid and accessory glands) is the middle layer and is the majority.
Mucus from goblet cells is deep (precorneal) and contains leukocytes and lysozymes (Moore and Collier).
Function of tears:
- Lysozymes and leukocytes provide antibacterial activity.
- Tears contain oxygen and other metabolites which provide nourishment to the cornea.
- The tear film has optical activity with a refractive index similar to that of the cornea.
- Wash away waste products and foreign debris.
- Provide lubrication for the movement of the eyelids over the cornea and bulbar conjunctiva.
Lacrimal puncta - 1-2 mm diameter, several mm from medial canthus on mucosal side of eyelid margin ; occasionally there is a ring of brown pigment surrounding puncta; rabbit has lower punctum only.
Canaliculi - converge to form nasolacrimal sac .
Nasolacrimal sac - not much more than a dilatation of the proximal end of the nasolacrimal duct in domesticated animals.
Nasolacrimal duct - has dilatations along its route - most prominent at level of first premolar tooth in horse.
External meatus - located within nasal cavity - easily seen in horse (at mucocutaneous junction on nasal floor) .
Mucus thread - mucus traps particulate matter in the tear film and accumulates at the medial canthus. This collection of mucus is present normally in all animals. The amount of mucus may increase with increased particulate matter in the air or with various inflammations.
See elsewhere (Rubin, et al.).
Radiographic visualization of nasolacrimal system using radiopaque contrast media (Gelatt, et al.; Latimer, et al.).
Same procedure as for lavage, but using contrast medium as flushing agent (e.g., sodium diatrizoate - Hypaque® - 50% - mixed with a water soluble gel such as K-Y®).
Survey radiographs are taken first.
Both sides should be done for comparison because variations exist between individuals of the same specie or breed.
All produce epiphora (an overflow of tears due to excess secretion or inability of the tear drainage apparatus to transport) .
Congenital absence of the punctum. Seen more commonly in American cocker spaniels, English bulldogs, and Bedlington terriers; rare in species other than dog.
Generally involves the lower punctum; those involving the upper punctum usually are asymptomatic.
In case of imperforate lower punctum, when upper punctum is flushed, there is 'tenting' of conjunctiva in region where the lower punctum should be.
Treatment:Need to do surgery; #11 scalpel blade is used to incise the conjunctiva in the region of tenting - small piece of conjunctiva is removed. Alternatively, the membrane overlying the punctum can be picked up with fine forceps and simply snipped off with tenotomy scissors.
If flushing is not helpful in localizing where the punctum should be, may attempt to pass a monofilament nylon suture retrograde from nose. Then cut down to the suture with scissors at the point where the punctum should be (should be able to see the suture).
After surgery, use topical steroid therapy to reduce chance of healing over - if wound heals over, repeat excision.
Atretic canaliculus may be opened if just scarred; if you cannot open it, could do conjunctivorhinostomy (create artificial opening from conjunctival side of medial canthus into nasal cavity for tear passage), but this is not recommended; better to live with the problem unless extreme.
Lack of development of distal portion of nasolacrimal duct (no external meatus) seen in horses (Latimer and Wyman) - if palpate where meatus should be, may feel tubular structure below mucosa (pressure on it may cause purulent material to escape from puncta).
Treatment in horses:Pass small (French size 5) polyethylene tube through one punctum down to end of nasolacrimal duct - flush saline to outline end of duct - incise over end of duct - if possible, nasal mucosa should be sutured to duct mucosa with 4-0 or 5-0 silk (remove in 14 days) - if cannot suture mucosa, then suture indwelling catheter in place for several weeks - treat with antibiotics and steroids several times daily for two weeks (via instillation into eye).
Occurs in poodles of all colors - more apparent in white because staining of the hair; occurs in other 'toy' breeds of dogs.
Nasolacrimal flush generally is unimpeded; system is anatomically open, but may be functionally closed.
The cause is thought by some to be an unnaturally shallow lacrimal lake. Others believe it is due to mild entropion of medial aspect of lower eyelid with the medial canthal hairs acting as a wick. Another possibility is trichiasis caused by the caruncular hairs.
If medial entropion is suspected as the cause, first put a suture in the medial canthus to evert the medial aspect of the eyelid margin. If this corrects the problem, then permanent surgery (such as the common entropion correction procedure) can be done. If the problem is thought to be due to caruncular hairs, cryotherapy of the caruncle may resolve the problem.
If treatment is necessary and you do not want to do surgery, you can use petroleum jelly to coat facial hairs and skin to prevent excoriation by tears.
Do not remove gland of third eyelid as advocated by some - this may predispose the patient to keratoconjunctivitis sicca.
Inflammation of lacrimal sac - seen in all species (Jones and Carrington; Lavach, et al.).
Cause:
Preceding conjunctivitis or foreign body with secondary bacterial contamination; inspissation of cellular debris.
Signs:
- Chronic conjunctivitis with excessive mucopurulent exudate.
- Epiphora, if nasolacrimal duct is occluded.
- Fluorescein passes slowly or not at all.
- Abscesses may be present at the medial canthal area.
- Pressure on the lacrimal sac area may cause discharge of material from puncta.
Treatment:
In chronic cases - culture and sensitivity.
Repeated lavage of system. May elect to lavage with specific antibiotic ointment which has been melted in a water bath or can use dilute or full-strength povidone-iodine solution (e.g., Betadine®).
Topical antibiotics - drops preferred.
Judicious use of topical steroids if offending organisms can be controlled.
Abscessation (if occurs) will granulate spontaneously once inflammation is controlled.
Catheterization - used only when irrigation is unsuccessful.Catheterization technique in small animals - general anesthesia required:
Can attempt to pass an 0 or 00 monofilament nylon suture through upper punctum and out through external nares; this may be difficult or almost impossible to do. If you succeed in this, then use PE50 or 90 polyethylene tubing over the suture as the final catheter. This is done by cutting an appropriate length that can be sutured to the periorbital and peri-nasal skin. The monofilament suture in the duct is used as a guide starting at the upper punctum; the tubing is passed over the suture and held in position with a hemostat placed on the suture at the dorsal end. Another hemostat is clamped to the suture protruding from the nose which then is pulled gently to pass the tubing through the duct. Once the tubing is in place, the suture is removed and the ends of the tubing are sutured to their respective skin (the one in the periorbital area must be placed so that the eyelids can close and there is no trauma to the cornea).
Catheterization technique in the horse - use xylazine or other chemical restraint:
Can pass catheter through lacrimal punctum and out through nose; easier to do than in dog, but horse may object too much unless heavily sedated or anesthetized; use PE90 or 160 polyethylene tubing. Usually easier to pass the catheter from the nasal end.
When the tubing is in place, suture to periorbital skin and the skin near the external nares: place a piece of bandage tape around the tubing to create a flap which in turn is sutured to the skin.
You may not be able to pass tubing from either direction if there is considerable scarring of the nasolacrimal duct. If the scarring is close to the external meatus, could pass tubing from eyelid end to the point of obstruction; if the tubing can be felt in this area, you could cut down to it to allow passage of the tubing (use local anesthetic or general anesthesia). After the tubing has been in place for several weeks, a new, permanent punctum will have formed.
Catheterization and retention tube placement can be a successful method of treating chronic dacryocystitis and re-establishing patency of the nasolacrimal duct system. If there is an imperfection in the nasolacrimal duct, the tubing may pass through this aberrant opening and pass into the nasal cavity, causing irritation and sneezing. When this happens, you can try to redirect the tubing through the correct meatus. If this does not work, you may have to try letting it pass through the nasal cavity; if the patient will not tolerate this, you may have to forgo catheterization.
Congenital veils: Occur in horses and reported in Persian kittens - break veil by vigorous flushing.
Nasal neoplasms: Dacryocystorhinography can be done to observe location of compression.
Foreign body, inspissated mucus, etc.: Treated by repeated lavage.
Inflammation: Treat systemically.
Nasolacrimal occlusion may be entirely secondary to an infolding of the eyelid margins (entropion) causing a functional occlusion of the punctum. Treat accordingly.
Inflammation of lacrimal gland.
Generally related to systemic disease - associated with distemper in dogs - uncommon in other species.
Remission in 3-4 weeks.
Signs:
Corneal ulcers
Xerosis (dryness) of cornea and conjunctiva
Blepharospasm - due to pain
Conjunctivitis
Treatment:
For general discussion and treatment see chronic form listed below.
Clinically termed keratoconjunctivitis sicca
Occurrence:
All dog breeds affected - appears to be more prevalent in 'toy' breeds (such as Lhasa apso dogs, schnauzers); may be related to the popularity of the 'toy' breeds; uncommon in cats, rare in other species.
Age - commonly from 5 months to 16 years (dogs).
Cause:
Generally not identified ( Kaswan, et al.)
Sequel to acute dacryoadenitis
Orbital and supraorbital trauma - most common cause in horses
Extensive conjunctival disease - lacrimal gland ducts occluded
Toxicities - by lacrimal secretory inhibitors (e.g., atropine, phenazopyridine) or by drugs such as sulfadiazine and other sulfas (Berger, et al.; Diehl and Roberts; Morgan and Bachrach; Slatter)
Phenazopyridine is found in some urinary antiseptics - it is a potent lacrimal gland toxin in the dog
Avitaminosis A - probably rare currently
Congenital lack of lacrimal activity - lack of glands or nervous stimulation - uncommon
Associated with generalized immune-mediated diseases (Kaswan, et al.; Quimby, et al.)
Spontaneous or senile atrophy
Temporary hyposecretion in old dogs following any surgical procedure (anesthesia) - cause unknown - may be from drugs or post-surgical circulatory disturbance
Loss of third eyelid gland (iatrogenic)
Patient history:
Classic pattern of acute conjunctivitis which improves with any topical therapy, but recurs as soon as therapy is discontinued; this pattern then becomes chronic in nature.
Signs:
Unilateral or bilateral - unilateral more often when not related to cause which would be expected to affect both eyes
Blepharospasm due to pain (this may disappear when the cornea keratinizes)
Photophobia
Cornea dry and lusterless
Corneal ulceration (more common during initial phase of reduced tear formation)
Thick, white (yellow if have bacterial infection), ropy discharge
Melanosis of the cornea (only after condition becomes chronic)
Vascularization of the cornea (usually after condition becomes chronic)
External nares may be moist or dry. Nasal moisture comes from nasal mucosa (in addition to tears), therefore the nares will be wet if keratoconjunctivitis sicca is uncomplicated. In traumatic or neurogenic case, the stimulation for nasal secretion also may be absent and the nares will become dry and obstructed with inspissated debris.
Diagnosis:
Clinical signs and history
Schirmer tear test
Treatment:
Whenever keratoconjunctivitis sicca is diagnosed, especially if you (and the patient) are fortunate enough to see it when it is acute in onset, all potentially lacrimotoxic medication being given the patient should be discontinued to determine if it is drug induced.
Keep the following two paragraphs in mind when considering the medical therapy which is listed afterwards. The goal of therapy depends upon the reason for the reduced (or absent) tear production. If the condition is acute in onset and the cause is able to be removed (e.g., a toxic drug), then therapy is aimed at simply keeping the eye moist until the lacrimal gland can recover. The period of time involved may be days to weeks. The only medications absolutely necessary under this circumstance would be artificial tears during the day and a lubricant prior to night time sleep. A topical steroid also could be used to reduce the inflammation, if necessary. Antibiotics are not needed and should be avoided. If the patient has a systemic disease such as distemper, appropriate supportive therapy needs to be provided.
Unfortunately, most people do not make the diagnosis during the acute phase. By the time reduced tear production as a cause of the patient's signs is recognized, there may be permanent damage to the lacrimal gland. Of course, the initial cause may have damaged the gland irreversibly, even if the condition was recognized at its onset. The goal of therapy under these circumstances is to keep the eye moist by artificial supplementation of tear production or by stimulating lacrimal activity, if possible. Therapy would have to be provided indefinitely. Because there often will be secondary bacterial infection, a topical antibiotic may be necessary until the eye can be returned to a moist state. A topical steroid also should be used to reduce inflammation, but will not be necessary in most cases once the eye can be kept moist.
Artificial tears - see therapeutics chapter - must be applied very frequently.
Lubrication - best combination is white petrolatum, mineral oil and lanolin (e.g., LacriLube S.O.P.®); lasts longer than artificial tears, but should be used along with, not instead of, artificial tears; particularly useful when long periods between artificial tear application will occur (such as at night time).
Antibiotics - only if there is an ulcer or bacterial infection, and then only until the eye is able to be kept moist on a consistent basis.
Steroid - a topical steroid may be desirable initially to reduce inflammation, thus reducing corneal vascularization and scarring; do not use if cornea is ulcerated.
Cyclosporine - desirable in most cases which are chronic in nature or are not expected to spontaneously resolve, because it has the potential of being the only medication necessary once the situation is stabilized (Kaswan, et al.; Olivero, et al.). One application every 12 hours of a 0.2% ointment should be used. Once the ocular condition is stabilized and tear production has returned as a result of cyclosporine treatment, all other medication can be discontinued in most cases.Some patients may require several weeks of cyclosporine use before beneficial results are seen. You should continue using for at least five weeks before considering it ineffective.Pilocarpine - this could be given orally as an alternative to cyclosporine (in addition to artificial tears and lubricant) (Rubin and Aguirre).
Unwanted side effects of cyclosporine, such as conjunctival irritation and facial dermatitis, occasionally occur and require discontinuation of the drug.
Cyclosporine appears to work by blocking immune-mediated lacrimal gland dysfunction. Therefore, it may be of no benefit in situations where dysfunction is due to other causes or the gland is severely degenerated.It is used for its lacrimogenic effect. If lacrimal tissue is present and is capable of being stimulated, pilocarpine will cause tearing. Although pilocarpine used to be a major part of chronic keratoconjunctivitis sicca treatment, the advent of cyclosporine has virtually eliminated its use. For those patients who may react negatively to cyclosporine, you still could try pilocarpine per the following regimen:Prognosis and long-term management:
For dogs 15 kg or less, use 1% ophthalmic solution; for dogs over 15 kg, use 2% ophthalmic solution. Start out with 1-2 drops twice a day for 2 days; have the client increase the dose by one drop each day to a maximum of about 5 drops twice a day. If, however, at any dose the patient salivates about 30-60 minutes after treatment, there is no need to increase the dose; if the dose is high enough to cause salivation, it should be high enough to stimulate any viable lacrimal tissue.
The medication should be mixed well in a small amount of food or given within gelatin or similar capsules.
The client must be warned about the potential toxic effects of pilocarpine. These include vomiting, diarrhea, and bradycardia (manifested as lethargy). If toxic signs occur, the dose should be reduced until no further signs of toxicity are seen; treatment should be discontinued if the patient cannot tolerate any amount of the drug.
The patient should be rechecked in 10-14 days to see if there has been a measurable increase in tear production. If tear production has not increased, the pilocarpine should be discontinued. In this case, the other medications should be continued. If the pilocarpine is causing an increase in tear production, you may be able to discontinue all other medication and maintain the patient on pilocarpine indefinitely.
As mentioned, in acute cases, where a specific cause can be eliminated and damage to the lacrimal gland is inconsequential, tear production will return spontaneously and continued medical therapy is unnecessary. Because of this, you only should use palliative therapy in acute cases, checking tear production every week or so. If tear production returns to normal, discontinue all therapy. Bear in mind that in patients with neurogenic or traumatic causes, this may require up to 60 days of therapy. If you suspect this is the case, adjust your re-examination intervals accordingly so as not to tax the client's financial situation.
In chronic cases, there have been times when tear production spontaneously returned, even after long periods of apparent lacrimal gland inactivity. Such recovery would be masked, of course, by concurrent therapy. The only way you will know if this is the case with a particular patient would be to occasionally discontinue whatever therapy you are using and observe the results. In some cases, it will become immediately apparent that therapy needs to be re-instituted because the eye becomes dry right away. In other cases, you may be able to demonstrate continued tear production and, therefore, cautiously discontinue therapy indefinitely.
Parotid duct transposition:
This is a surgical procedure which may be effective in keeping the eye moist in patients in whom there is no response to cyclosporine (or pilocarpine) or if clients cannot give tear replacement frequently enough (Lavignette; Testoni, et al.). There is considerable potential for serious complications, however, and the procedure should be used only as a last resort (Betts and Helper). In any case, it is strongly recommended that you refer to a specialist any patient you consider to be a candidate for this surgery; do not attempt to do this surgery yourself.
Neoplasia of the lacrimal gland is uncommon. Nevertheless, any recurrent swelling in the region of the gland should be biopsied to rule out neoplasia. Signs seen would include deviation of the globe, ocular discharge, etc.
Eyelid neoplasia may affect the lacrimal puncta, canaliculi and nasolacrimal sac. This is covered in chapter on eyelids.
Nasal or maxillary sinus neoplasms may affect drainage of tears by compressing the nasolacrimal duct. These are more common than lacrimal gland neoplasms and are of various types. Some may invade the orbit or cause pressure on the orbit so that the globe will be deviated. Additional mention will be made in chapter on the orbit and globe.
Footnotes:
Atropine and ulcers with keratoconjunctivitis sicca: Although an iridocycloplegic, such as atropine, usually is recommended in the case of corneal ulceration, it is best not to use this in keratoconjunctivitis sicca because it may further reduce tear production.