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Keratoconjunctivitis Sicca (view source)
Revision as of 17:43, 20 February 2014
, 17:43, 20 February 2014Created page with "'''Keratoconjunctivitis Sicca''' (KCS)is a condition resulting from the lack of production of the '''aqueous''' phase of the tear film. It is also known as '''dry eye'''. ==A..."
'''Keratoconjunctivitis Sicca''' (KCS)is a condition resulting from the lack of production of the '''aqueous''' phase of the tear film. It is also known as '''dry eye'''.
==Aetiology==
===Immune-Mediated===
The most common cause in '''dogs'''. The immune system damages the glandular tissue. Dogs with KCS often have other '''immune-mediated''' diseases.
===Iatrogenic===
Certain '''drugs''', including [[Sulphonamides]], have been associated with KCS. '''Atropine''' causes a temporary reduction in tear production.
Surgical excision of the '''Nictating Gland''' has been associated with KCS later in life, with a '''median''' time for onset of signs 4.5 years after surgery.
===Neurogenic===
KCS occurs if '''parasympathetic''' innervation to the glands is disrupted. Possible causes include '''trauma''', '''neoplasia''', '''infection''' and '''surgical intervention'''. The KCS is more likely to be '''unilateral'''.
===Congenital===
Due to '''glandular aplasia''' or '''hypoplasia'''. More common in '''miniature''' breeds. May resolve with '''maturity'''.
===Infectious===
Infection with [[Canine Distemper Virus]] may result in temporary or permanent dysfunction of the glands. [[Leishmania]] can also cause KCS, as can any '''chronic''' infectious process that results in '''fibrosis''' of the glands.
==Signalment==
Dogs over '''10 years''' old are at greater risk of KCS due to '''senile atrophy''' of their glands. '''Boston Terriers''', '''Cavalier King Charles Spaniels''', '''English Bulldogs''', '''English Springer Spaniels''', '''Lhasa Apsos''', '''Minature Schnauzers''', '''Shih Tzus''', '''West Highland West Terriers''' and '''Yorkshire Terriers''' are all consider predisposed.
==Clinical Signs==
A '''thick mucoid and mucopurulent''' discharge is the most consistent sign of KCS. It often adheres to the '''eyelids'''. The '''conjunctiva''' may be '''thickened, hyperemic''' and '''chemotic'''.
'''Blepharospasm''' may occur to a variable degree. [[Corneal Ulceration - Dogs and Cats|Corneal ulceration]] often occurs, and may not heal as well as expected. '''Corneal Vascularisation''' and '''Pigmentation''' occur in chronic cases, leading to vision loss.
A '''dry, lusterless cornea''' is considered pathognomic for KCS, but only occurs in 25% of cases.
Clinical signs can wax and wane, and are often worse at certain times of the year, such as hot and dry periods or in winter when humidity is low.
==Diagnosis==
'''Schirmer Tear Tests''' are used to diagnose KCS. Normal values are in excess of 10mm. KCS should also be suspected when values are less than 15mm in conditions where excess tear production is expected, such as '''corneal ulceration'''.
Consideration should be given to ruling out other conditions that have been associated with KCS, including [[Hypothyroidism]], [[Diabetes Mellitus]] and '''Polyarthritis'''.
{{Unfinished}}
==Aetiology==
===Immune-Mediated===
The most common cause in '''dogs'''. The immune system damages the glandular tissue. Dogs with KCS often have other '''immune-mediated''' diseases.
===Iatrogenic===
Certain '''drugs''', including [[Sulphonamides]], have been associated with KCS. '''Atropine''' causes a temporary reduction in tear production.
Surgical excision of the '''Nictating Gland''' has been associated with KCS later in life, with a '''median''' time for onset of signs 4.5 years after surgery.
===Neurogenic===
KCS occurs if '''parasympathetic''' innervation to the glands is disrupted. Possible causes include '''trauma''', '''neoplasia''', '''infection''' and '''surgical intervention'''. The KCS is more likely to be '''unilateral'''.
===Congenital===
Due to '''glandular aplasia''' or '''hypoplasia'''. More common in '''miniature''' breeds. May resolve with '''maturity'''.
===Infectious===
Infection with [[Canine Distemper Virus]] may result in temporary or permanent dysfunction of the glands. [[Leishmania]] can also cause KCS, as can any '''chronic''' infectious process that results in '''fibrosis''' of the glands.
==Signalment==
Dogs over '''10 years''' old are at greater risk of KCS due to '''senile atrophy''' of their glands. '''Boston Terriers''', '''Cavalier King Charles Spaniels''', '''English Bulldogs''', '''English Springer Spaniels''', '''Lhasa Apsos''', '''Minature Schnauzers''', '''Shih Tzus''', '''West Highland West Terriers''' and '''Yorkshire Terriers''' are all consider predisposed.
==Clinical Signs==
A '''thick mucoid and mucopurulent''' discharge is the most consistent sign of KCS. It often adheres to the '''eyelids'''. The '''conjunctiva''' may be '''thickened, hyperemic''' and '''chemotic'''.
'''Blepharospasm''' may occur to a variable degree. [[Corneal Ulceration - Dogs and Cats|Corneal ulceration]] often occurs, and may not heal as well as expected. '''Corneal Vascularisation''' and '''Pigmentation''' occur in chronic cases, leading to vision loss.
A '''dry, lusterless cornea''' is considered pathognomic for KCS, but only occurs in 25% of cases.
Clinical signs can wax and wane, and are often worse at certain times of the year, such as hot and dry periods or in winter when humidity is low.
==Diagnosis==
'''Schirmer Tear Tests''' are used to diagnose KCS. Normal values are in excess of 10mm. KCS should also be suspected when values are less than 15mm in conditions where excess tear production is expected, such as '''corneal ulceration'''.
Consideration should be given to ruling out other conditions that have been associated with KCS, including [[Hypothyroidism]], [[Diabetes Mellitus]] and '''Polyarthritis'''.
{{Unfinished}}