Eye Disorders associated withTear Production


Introduction.


Tears have several very important functions and are essential for the health and transparency of the cornea (the surface of the eye).  Significantly:







Blocked Tear Ducts

(Technically known as Imperforate Lachrymal Punctum)



Introduction.


Tears ‘flow’ over the conjunctiva and ‘gravitate’ towards the median corners of the eyes.  Under normal circumstances they drain via tiny apertures (puncta). located behind the lower eyelids, into ducts that eventually drain into the nasal passage.


The condition commonly referred to as ‘blocked tear duct(s)’ may be due to:





Bedlington terriers are one of several breeds of dogs that are considered to be ‘prone’ to the congenital condition.  


The condition is usually bilateral, i.e. affecting both eyes - when unilateral, i.e. when only one eye is affected, the punctum is generally narrowed rather than completely closed.



Cause.


There is no doubt concerning the familial nature of the condition in Bedlington terriers.  However, the pattern of inheritance has not been determined.



Symptoms.





 Diagnosis.


Excessive tearing can be caused by a number of different conditions.  The veterinary surgeon will flush the naso-lacrimal system to determine the origin of the constriction.



Treatment.


The condition is relatively easy to correct.  An small incision is made in the blocked orifice and then enlarged to minimise the likelihood of the wound ‘closing’.  Steroids may be applied topically in the immediate post operative period.





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Dry Eye

(Technically known as Keratoconjunctivitis Sicca)



Cause.


The primary underlying cause of dry eye is inadequate production of tears necessary to maintain the eye(s) in a healthy condition.  Although this may be due to such factors as trauma or infection, the main cause appears to be progressive destruction of the tear glands by the dogs own auto-immune system.


It is apparently a relatively common condition in dogs.  It can occur in all breeds of dogs and it has been estimated that 1 in 22 dogs in the UK are affected to some degree, with certain breeds, e.g. Cocker spaniels, Cavalier King Charles spaniels, Yorkshire terriers and West Highland White terriers, being significantly more prone to the condition than others.


Fortunately, the reported incidence in Bedlington terriers seems to be relatively low, although 3 cases recently have  been brought to the attention of the BTHG.



Signs of Dry Eye.


The condition often develops in one eye with the second eye subsequently being affected some time later.  It is important to realise that the signs of dry eye varies and, particularly in the early stages, may not be obvious.  


Presence of any of the following signs should be considered as suspicious and it is strongly advocated that the dog should be checked by a veterinary surgeon.  






Subsequent changes may include the development of conjunctivitis, bacterial infection (often accompanied by a “thick” discharge), ulceration and, ultimately, blindness.


Generally, dry eye is not curable.  Early diagnosis and prompt treatment is essential to minimise the effects of the condition.



Diagnosis.


Because of the variability of the signs, it can be very difficult to diagnose dry eye purely on the basis of a physical examination of the eye(s).  Fortunately, there is a very simple, straight-forward test available, the Schirmer Tear Test, which measures the level of tear production over a 1 minute period and which can be carried out without any discomfort to the dog.



Treatment.


The aims of treatment are to restore moisture to the eye and to treat conditions such as infection or ulceration that develop because of the lack of normal tears.  


Cyclosporine ophthalmic ointment or drops is the treatment of choice due to its efficiency at stimulating tear production, the need for fewer applications, and the lack of undesirable side effects with long term use.  Adequate tear production may not occur for a few weeks or even longer, and during this time artificial tears must be used as well.


Generally it will take a period of trial-and-error for your veterinarian to determine what is the best treatment regime for your dog.


It is important to recognize that this treatment is not a cure for dry eye.  It is a way to manage a frustrating, painful, and potentially blinding condition and the condition will return if treatment is stopped.


Note.


In very severe cases surgery may be recommended.  This involves diversion of a salivary duct into the lower eyelid area.  Saliva then drains into the eye, providing lubrication.







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