Main : Conditions of the
Eyelids and Ocular Adnexa in Dogs and
Cats

Conditions of the Eyelids and Ocular Adnexa in Dogs
and Cats

David T. Ramsey, DVM, Diplomate ACVO
Associate
Professor, Comparative Ophthalmology,
Department of Small Animal
Clinical Sciences
D-208 Veterinary Medical Center
Michigan
State University
East Lansing, MI  48824-1314

The eyelids and ocular adnexa comprise the primary surface
defense for the globe, specifically the cornea.  Physical or
functional abnormalities of the lids or adnexal ocular structures
may result in abnormalities of the cornea and subsequently
vision.  This commentary will discuss diagnosis and treatment
of the more common abnormalities affecting the lids and ocular
adnexa in dogs and cats.

Anatomy

The eyelids represent a composite structure composed of skin and
cutaneous appendages, including hair follicles and glandular
structures.  Dogs have eyelashes only on the upper lid and cats
lack upper and lower eyelashes.  The palpebral conjunctiva is a
highly vascular mucous membrane that lines the inner aspect of the
lids.  Interposed between the surface skin and palpebral
conjunctiva is skeletal muscle and fibrous tissue.  Eyelids are
highly vascularized, therefore they are fairly resistant to
microbial infection and have the property of healing rapidly after
suffering trauma, but may enlarge considerably from transvascular
exudation of fluid into lid tissue when irritated.  Since skin
comprises a substantial portion of the eyelid, a plethora of
dermatologic conditions may affect the eyelids.1
The adnexa consists of all segments of conjunctiva (palpebral,
nictitans, bulbar and fornix), and the nictitating membrane.
The conjunctiva is the most exposed mucous membrane of the
body.  It is most frequently an “innocent bystander” in the
dog, and conjunctival hyperemia is a nonspecific secondary response
to ocular or systemic disease processes.  However conjunctival
hyperemia in the cat is most frequently caused by infectious
pathogens that directly affect the conjunctiva (e.g., Feline
Herpesvirus-1, Chlamydiophila felis).

Although the histologic anatomy of the canine eyelid is similar
among different canine breeds, substantial variation in eyelid
carriage and conformation among different breeds creates
considerable challenges for the veterinarian.  Conformational
eyelid abnormalities in cats are uncommon but are very common
abnormalities of the eyelids in dogs.  Presence of a
conformational lid abnormality in a given canine breed may eliminate
this dog from competitive show by a judge, while absence of the
identical abnormality in another breed would serve as grounds for
elimination from competitive show.  Surgical correction of a
conformational eyelid or ocular adnexal abnormality may also
constitute grounds for disqualifying a dog from show by some
national breed clubs (see http://www.vin.com/WebLink.plx?URL=http://www.akc.org/dic/clubs/showrule.cfm%3Fpage%3D12).
Knowledge of the variety of eyelid conformations among different
purebred dogs is essential.

It is important to properly evaluate eyelid anatomy and function
prior to undertaking any blepharoplastic procedure attributable to
any of the above conditions.  A “no-touch” eyelid evaluation
should be performed initially.  Eyelid function should then be
assessed by stimulating a blink reflex.  The examiner should
note the amount of eyelid margin misalignment.  Next,
ophthalmic anesthetic solution should be instilled topically and the
examination repeated in the same manner.  It is critical to
compare results of the initial examination with results of the
examination after instillation of topical anesthetic solution for
changes in eyelid function, carriage or anatomy.  Eyelid
surgery should never be performed by a veterinarian who has not
personally evaluated eyelid conformation and carriage in an awake,
non-sedated animal.  Evaluation must be done prior to general
anesthesia.

Abnormalities of the eyelids and adnexa are divided arbitrarily
into categories that denote general etiologic considerations,
including congenital, acquired, structural/conformational,
inflammatory, and neoplastic conditions; category overlap is
common.

Structural/Conformational Abnormalities

Abnormalities in eyelid structure or conformation may be
congenital or acquired.

Congenital

1.  Eyelid Agenesis (coloboma).
Eyelid agenesis is a congenital defect of that occurs most
frequently in cats.  The upper temporal eyelid (lateral 1/3 to
2/3) fails to develop resulting in a full- or partial-thickness
defect (Figure 1).  Absence of eyelids results in secondary
trichiasis and exposure keratoconjunctivitis.  If the agenesis
is mild, cryoepilation or entropion surgery can be performed to
limit trichiasis.  If severe, surgical correction requires use
of grafting procedures, using the lower eyelid and the conjunctiva
of the nictitating membrane as the donor site, to construct a
functional eyelid.

2.  Ankyloblepharon.
Ankyloblepharon is adhesion of the eyelid margins to each
other.  Dogs and cats have physiologic ankyloblepharon until
10-14 days of age.  If it persists past 15 days of age,
infection of the conjunctival sac (ophthalmia neonatorum) may occur
and is typified clinically by excessive swelling and/or discharge at
the medial canthus (Figure 2).  The eyelids should be separated
using gentle (digital) traction.  I recommend massaging the
fused lids toward the medial canthus with a warm, wet cotton ball to
effect separation.  Exudate should be submitted for bacterial
culture.  The palpebral fissure should be flushed with sterile
saline and a broad-spectrum antibiotic ointment applied topically q
6 h.  Untreated neonatal conjunctivitis can lead to severe
corneal scarring or loss of the globe.

3.  Micropalpebral fissures.
Narrowing of the palpebral fissures is usually associated with other
concurrent congenital defects (entropion, microphthalmos) in the
Shar Pei, Chow chow, Kerry blue terrier and Collie.  Correction
usually requires blepharoplastic surgical procedure in which
conjunctiva is sutured to the incised eyelid surfaces to enlarge the
fissure.

4.  Macropalpebral fissures.
Excessively large palpebral fissures is common in brachycephalic dog
breeds with congenital exophthalmos (shallow orbits), the
Bloodhound, St. Bernard, American and English Cocker spaniel.
The dorsal sclera may be exposed and prominence of the globe may
prevent closure of the eyelids while sleeping (nocturnal
lagophthalmos).  Secondary exposure keratitis may result in
corneal pigmentation and fibrosis.  Surgical shortening the
palpebral fissure is indicated but must be performed where the
abnormality exists (permanent lateral or medial canthoplasty).

5.  Dermoid.  A dermoid is a
choristoma (normal tissue in an abnormal location).  Dermoids
may be present on the eyelid (Figure 3) but most frequently they are
located on the lateral conjunctiva or cornea.  Treatment
requires surgical excision and is curative.

Acquired

1.  Entropion.  Entropion is
defined as inversion of the eyelid margin.  Secondary
trichiasis (misdirected hairs of the eyelids) often results.
The lower lateral eyelid is usually involved but depending on the
breed, any part of the eyelid margin can be involved.  Clinical
signs vary from epiphora to corneal perforation.  Entropion is
classified as primary (anatomical), spastic (physiological), and
cicatricial (scarring).

a.  Primary (anatomical).
Primary entropion results from a structural abnormality of the
eyelid/tarsal plate.  Primary entropion is differentiated from
secondary entropion by response to topical anesthetic: If entropion
persists after instillation or topical anesthetic, there is no
spastic component.  When entropion occurs in a puppy or foal
(e.g., prior to mature facial conformation), temporary “tacking
sutures” can be placed to result in eversion of the eyelid
margins.  Several vertical mattress sutures are placed at the
haired-nonhaired junction (approximately 3-mm from the eyelid
margin) at partial-thickness depth in the lid and apposed to the
skin overlying the bony orbital margin.2  Placement
of tacking sutures often eliminates the need for surgical correction
of entropion later in life.  Tissue adhesives and staples have
also been used to tack eyelids.  Once mature facial
conformation is attained, surgical correction requires use of a
blepharoplastic surgical technique.  The shape, size, and
location of the surgical incision vary with the breed, age,
severity, and location of entropion.  Silk sutures have been
recommended to oppose the wound.  Medial canthus entropion is a
common cause of epiphora in brachycephalic canine and feline breeds,
and also occurs in canine breeds with tense eyelid-to-globe
conformations (Toy and Miniature Poodles, Bichon Frise, Maltese,
others).  The lesion may be subtle and is often overlooked as a
cause of epiphora.  Many of these breeds have concurrent medial
canthal entropion and excessive nasal folds.  Medial
canthoplasty surgery is required.  Care should be exercised to
avoid accidentally incising the canaliculi.  Use of a Buster or
Elizabethan collar is recommended postoperatively to prevent
self-excoriation of the surgical area.

b.  Spastic (physiological).
Spastic entropion refers to entropion caused by spasm of the
orbicularis oculi muscle in response to ocular pain or
irritation.  Ocular pain may cause severe blepharospasm which
in some instances results in entropion.  Secondary trichiasis
occurs from eyelid hair rubbing against the cornea, which causes
further ocular pain, additional blepharospasm and subsequently more
pronounced entropion.  The spastic component of entropion is
determined by instilling topical anesthetic; spastic entropion is
that portion of entropion relieved by topical anesthetic.  If
persisting for long duration, spastic entropion may become
cicatricial secondary to tarsal fibrosis.  Treatment is
directed at removing the cause of ocular pain and placement of
temporary tacking sutures.

c.  Cicatricial.  Cicatricial
entropion results from trauma (including previous eyelid surgery) or
from chronic spastic entropion.  Cicatricial entropion is less
common and surgical correction more difficult to achieve long-term
correction.

2.  Ectropion.  Ectropion is
eversion of the eyelid margin.  This may result in exposure of
the conjunctiva (usually lower) but is usually less serious than
entropion.  The most common cause of ectropion is
conformational ectropion that occurs in Spaniel and hound breeds,
and surgical correction is not only unnecessary but may exclude a
dog from competitive show.  Neuroparalytic ectropion following
facial nerve damage can occur but is uncommon.  Clinical signs
of ectropion include visualization of the lower conjunctiva, and may
include conjunctival hyperemia, keratitis, and mucus accumulation in
the lower conjunctival cul-de-sac.  Ectropion frequently occurs
secondary to instability of the lateral canthus and is misdiagnosed
as primary ectropion.  In such instances, correction of
ectropion alone will not correct the abnormality.  Correction
of ectropion is indicated only when eyelid function (ability to
blink) is intact and abnormalities of the cornea are evident.
Surgical correction by full-thickness wedge resection is simple and
effective.  A “V to Y” blepharoplasty can also be used for
cicatricial ectropion. This elevates skin overlying scar tissue and
allows the eyelid margin to retract to a more normal
position.

3.  Instability of the Lateral
Canthus.  This condition may be attributable to a primary
defect or laxity of the retractor anguli oculi lateralis muscle
and/or the lateral canthal tendon.  Many affected dogs have
abnormal tarsal plate development.  Concurrent entropion and
ectropion of one or both eyelids is common.  The normal
position of the lateral canthus varies by breed but is usually
lateral and slightly ventral to a horizontal line drawn across the
cornea.  This frequently occurs in the St. Bernard,
Newfoundland, Chow chow, Bloodhound, and Bullmastiff, but can occur
in most breeds.  Correction involves creation of new lateral
canthus (lateral canthoplasty), removal of excess eyelid tissue
and/or primary entropion repair.2

4.  Brow Ptosis - Certain canine
breeds have a very heavy brow which induces secondary entropion of
the upper eyelid.  When present and inducing entropion and
secondary corneal abnormalities, a brow lift procedure is
indicated.  Various surgical procedures have been described to
correct brow ptosis.  I recommend that you consider referring
dogs to a veterinary ophthalmologist for brow ptosis surgery.

5.  Lagophthalmos.  The inability
to blink may result in exposure keratitis.  Facial nerve
dysfunction (idiopathic, traumatic—following bulla osteotomy) are
common causes.  Temporary lagophthalmos (facial neuropraxia)
after total ear canal ablation and bulla osteotomy surgery is
common.  If eyelid function is absent, the cornea should be
kept moist using a bland, preservative-free tear ointment.
Permanent lagophthalmos may require permanent lateral tarsorrhaphy
surgery to decrease tear evaporation by decreasing the tear film
meniscus between the upper and lower eyelids.

Eyelash Abnormalities

1.  Distichiasis.  Distichia are
cilia that arise from Meibomian gland openings (Figure 4).
Both upper and lower eyelids can be affected.  Animals with
distichiasis must be evaluated carefully; the mere presence of
distichia is not justification for removal (e.g., most American
Cocker spaniels).  Treatment is indicated only when cilia are
inducing corneal irritation (ulceration, vascularization, fibrosis,
pigmentation, epiphora or persistent blepharospasm).  Soft,
fine, tapered or silky cilia which float in the tear film usually do
not cause irritation.  Correction involves electroepilation or
cryoepilation.  Thermocautery is contraindicated as it destroys
normal eyelid structures and results in scarring.  Manual
epilation is effective only temporarily but may aide in determining
if the cilia are causing clinical signs or disease.

2.  Districhiasis.  Districhiasis
is defined as two or more cilia emanating from a single Meibomian
gland opening.  For treatment see Distichiasis above.

3.  Ectopic cilia – Ectopic cilia is a
hair or bundle of hairs that emanate through the palpebral
conjunctiva (usually the upper central eyelid) usually near the base
of the Meibomian gland.  Ectopic cilia are usually diagnosed in
young dogs; they are exceedingly rare in cats.  The cilia cause
corneal irritation or ulceration in the area that they overlie, and
are usually located in the perilimbal cornea.  Spastic
entropion and epiphora are common.  Examination with
magnification may reveal a pigmented area of conjunctiva surrounding
the orifice of the ectopic cilia.  Excision of the palpebral
conjunctiva, including the cilia and its follicle, is usually
curative.

4.  Trichiasis.  Trichiasis is a
cilia which originates from a normal location that is misdirected
toward the cornea, conjunctiva, or eyelids.  This may result
secondary to entropion, or as a primary entity (e.g., excessive
nasal skin folds in brachycephalic breeds).  If trichiasis
occurs secondary to entropion, a modified Hotz-Celsus procedure may
be indicated.  If trichiasis results from nasal skin folds
contacting the cornea, excision of skin folds or medial canthoplasty
is the treatment of choice.

Inflammatory Eyelid Diseases

1.  Chalazion  (ka-lay-zee-on).
Retention or blockage of oily secretions from the Meibomian gland
extravasates into surrounding eyelid tissues and induce a
granulomatous inflammatory response.  Clinically a chalazion
appears as a firm, nodular, yellow-gray mass through the palpebral
conjunctival surface (Figure 5) and is painless.  Chalazia
occur more frequently in dogs than in cats and most commonly occur
secondary to a Meibomian gland adenoma which block secretion of the
Meibomian gland.  Treatment requires surgical curettage through
the conjunctiva.2  The skin is not
incised.  Aftercare consists of topical antibiotic-steroid
solution for 5-7 days.

2.  Hordeolum (stye).  A
hordeolum is inflammation of the glands of Zeis or Moll (external
hordeolum) or Meibomian gland (internal hordeolum).  The
hallmark clinical sign of a hordeolum is pain upon manipulation.
Treatment includes drainage, topical antibiotic ointment, and hot
packs.

3.  Meibomitis - Staphylococcal
infection usually associated with generalized dermatoses.  The
Meibomian glands exude a yellow, purulent material instead of a
clear oily secretion (Figure 6).  Examination of the
conjunctival surface shows linear yellow-white inflammatory
infiltrates perpendicular to the eyelid margin.  Material
should be expressed for bacterial culture and susceptibility
testing.  Topical and systemic antibiotics and warm compresses
are indicated.  Oral corticosteroids may also be necessary.

4.  Blepharitis - inflammation of the
eyelids, especially the eyelid margins, is common but may be
overlooked if it is part of a more generalized dermatitis.
3

a.  Etiologies:

1)  Bacterial - most commonly
Staphylococcus aureus.  Juvenile pyoderma/puppy
strangles in puppies or staphylococcal hypersensitivity in the
adult.  Topical and systemic antibiotics are indicated.
Systemic corticosteroids in refractory or severe acute cases are
also indicated.  In generalized dermatological disease, the
underlying cause should be established and treated accordingly.

2)  Parasitic - mites, e.g.,
Demodex or Sarcoptes in young dogs, Notoedres
in cats.

3)  Metabolic - seborrheic blepharitis
associated with generalized seborrhea or allergic dermatitis.

4)  Actinic - related to sunlight.

5)  Fungal - dermatomycoses.

6)  Traumatic - lye, acids, fire.

7)  Immune-mediated/allergic -
pemphigus, toxic epidermal necrolysis, atopy.

8)  Viral – FHV-1 in young
kittens.  Substantial cicatricial lid deformation and corneal
fibrosis may result.

b.  Diagnosis and treatment:  Diagnosis
requires testing similar to that for other dermatologic diseases
including skin scrapings, cultures (bacterial and fungal), and
biopsy if necessary.  Treatment is based on diagnosis of the
underlying cause.

5.  Blepharedema.  Blepharedema
is a clinical sign rather than a disease entity.  Causes
include trauma, allergies/hypersensitivity reactions, insect bites,
secondary to orbital cellulitis/abscess, and vasculitis.
Treatment depends on the underlying cause but may consist of
corticosteroids (topical and systemic), non-steroidal
anti-inflammatory drugs, antihistamines, and topical and oral
antibiotics (e.g., secondary to cellulitis).

Traumatic Eyelid Abnormalities

Eyelid lacerations occur frequently in many domesticated
animals.  Bite wounds or automobile trauma is the most common
causes.  The animal must be carefully evaluated for concurrent
systemic abnormalities. The globe should also be examined thoroughly
to determine if concurrent ocular trauma is evident.  Eyelid
lacerations should be repaired as soon as possible.  Eyelids
are extremely vascular and post-traumatic swelling can be
extensive.  However, beneficial properties of highly vascular
tissues include rapid rate of healing and resistance to
infection.  When lacerations of the medial aspect of the
eyelids occurs, the lacrimal puncta should be cannulated and flushed
to determine if the nasolacrimal duct is involved.  Eyelid
wounds should be cleaned of all debris and prepared with a dilute
Betadine solution.  The wound should not be debrided (or
minimally debrided).  If the wound is not fresh or is extremely
swollen and edematous, the wound should be irrigated gently.
Application of a topical broad-spectrum antibiotic and atropine
should be applied to the globe and lids, and a nitrofurazone bandage
placed for 12 to 24 hours.  This will provide dramatic
improvement in the appearance of the wound.  The wound should
then be cleansed be apposed in a two-layer closure to ensure
adequate physiologic and cosmetic results.  5-0 or 6-0
polyglactin 910 is recommended to oppose the tarsoconjunctiva,
taking care to bury the knots in the tissue to avoid corneal
irritation or damage.  Simple interrupted sutures of 4-0 or 5-0
silk are used for the skin.2  The first suture is
placed at the eyelid margin in a figure-8 pattern to ensure accurate
apposition.  The next suture is placed 1-2 mm from the
appositional suture.  The remaining wound is closed with simple
interrupted sutures.  Aftercare consists of topical and
systemic antibiotics for 7-10 days.

Neoplastic Eyelid Diseases

The biological behavior of eyelid neoplasms of dogs and cats
differ substantially. 4,5  Canine eyelid neoplasms
generally have a benign biological behavior and can usually be
differentiated based on clinical appearance.  In stark contrast
to eyelid neoplasms of dogs, those of cats have a malignant
biological behavior and can not be differentiated from each other
based solely on clinical appearance.  Feline eyelid neoplasms
may all be raised, alopecic, and eventually ulcerate.
Cytologic examination of fine needle aspiration and biopsy samples
of feline eyelid masses may reveal a specific type of
neoplasm.  Feline eyelid neoplasms should always be submitted
for histologic identification.  The most common skin neoplasms
of dogs and cats also apply to those of the eyelid.  Histologic
examination of all lid masses is recommended.

Canine Eyelid Neoplasms

Meibomian (Sebaceous) Adenoma.  The most
common eyelid neoplasm of dogs is a Meibomian
adenoma.4  This neoplasm arises from the Meibomian
gland but is observed at the eyelid margin, near the Meibomian
orifice (Figure 5).  Treatment is recommended when corneal
irritation results from contact.  Simple excision parallel to
the eyelid margin is not effective.  Treatment requires
debulking and adjuvant cryosurgery or full-thickness eyelid
resection.  The amount of lid shortening that may be done is
dependent upon the conformation of the lids in a given breed.
Very little tissue may be removed without inducing iatrogenic
ectropion or entropion in canine breeds that have a taut
lid-to-globe conformation (Miniature poodle, Bichon Frise, other
brachycephalics).

Melanoma.  Lid melanomas are usually superficial and
benign.  They occur most frequently in older dogs of heavily
pigmented breeds.  They are usually slow growing, may be
multiple, and are cryosensitive.

Papilloma – Papilloma are usually superficial and affect
young dogs.  Surgical removal is recommended if a rapid
increase in size or irritation to the cornea occurs.  Papilloma
are cryosensitive but may spontaneously regress in young dogs.

Adenocarcinoma – Adenocarcinoma can not be differentiated
from Meibomian gland adenoma based on clinical appearance.
Although histologically malignant, benign biological behavior is the
rule. Adenocarcinoma are also cryosensitive.

Histiocytoma.  Histiocytoma is primarily a tumor of
young growing dogs.  Histiocytoma has a characteristic clinical
appearance in the dog—it is always raised, less than 1 cm in
diameter, pink in color, hairless, and has a characteristic rapid
growth pattern (Figure 7).  Histiocytoma frequently regresses
spontaneously between 3 and 5 weeks after it appears.

Feline Eyelid Neoplasms

Squamous cell carcinoma.- The most common eyelid neoplasm
of cats is squamous cell carcinoma.5  The biological
behavior is that of very rapid growth, highly invasive locally, with
a tendency to ulcerate early, and occasionally late metastasis to
regional lymph nodes or organs.  Wide surgical excision and
adjuvant radiation, cryosurgery, interstitial brachytherapy, or
hyperthermia is indicated.

Basal cell carcinoma.  Initially basal cell carcinoma
forms a discrete circular nodule that develops an ulcerated
surface.  Eyelid basal cell carcinoma in cats ulcerates with
equal frequency as other eyelid neoplasms, unlike those located
elsewhere on the body.  The biological behavior is that of
being locally invasive but rarely metastasizes.

Fibrosarcoma.  Fibrosarcoma is a firm, raised,
alopecic, mass that also may ulcerate.  It may be associated
with FeLV infection.

Mast cell tumor.  May appear identical to those
listed above, but this neoplasm generally has the best prognosis of
all eyelid neoplasms in the cat.  Local excision with
appropriate surgical margins may be curative.

Conjunctivitis

It is important to differentiate conjunctival from episcleral
hyperemia/injection.  Conjunctival vasculature can be
differentiated from underlying episcleral vasculature based on
several characteristic differences:

Conjunctival vasculature:

a)  has extensive branching

b)  appears bright red in color

c)  is freely mobile and tends to move over
the surface of the globe with eyelid manipulations

d)  will blanch when a sympathomimetic (e.g.
phenylephrine) is applied topically

Episcleral vasculature:

a)  has a radial pattern from the limbus

b) appears dark red in color

c) is not freely mobile - conjunctival vessels
move over the underlying episcleral vessels

d)  does not readily blanch when a
sympathomimetic is applied topically

These characteristics are important when differentiating bulbar
conjunctival hyperemia from episcleral congestion associated with
serious intraocular disease (iridocyclitis, intraocular neoplasms,
and glaucoma).

Nonspecific Conjunctival Responses to Disease

1.  Conjunctival Hyperemia frequently
occurs in response to a variety of local and systemic diseases.
Unless other criteria for inflammation are fulfilled, conjunctival
hyperemia should not be used synonymously with conjunctivitis.

2.  Conjunctival Hemorrhage -
conjunctival capillaries rupture easily when traumatized.
Hemorrhage usually occurs into the subconjunctival tissue.
Treatment is not necessary and the hemorrhage will spontaneously
resolve in several days.  However, conjunctival hemorrhage
should alert the clinician to perform a complete ophthalmic
examination to determine if concurrent intraocular damage has
occurred.

3.  Chemosis - edema of the
conjunctiva may result from local allergic reactions,
irritating/traumatic stimuli, in concert with infectious (upper
respiratory) disease (chlamydiosis in cats), or obstruction of
orbital venous drainage.  Affected tissue appears pale or dark
and swollen, often “ballooning” through the palpebral fissure.
Chemosis will resolve without complication following correction of
its underlying cause.

4.  Lymphoid Follicle Formation -
proliferation of small lymphoid follicles are normally present on
the bulbar surface of the nictitating membrane. Under pathologic
conditions, they can also appear on any of the conjunctival
surfaces.  In most situations, follicles suggest chronic
physical irritation (e.g., entropion, trichiasis) or antigenic
stimulation (e.g., allergies).

5.  Pigmentation—chronic irritation
(trichiasis, ectopic cilia, keratoconjunctivitis sicca [KCS]) or
inflammation may result in hyperpigmentation of the conjunctival
epithelium.

6.  Ocular Discharge - varies with the
type of disease: serous (viral, allergic); mucoid to mucopurulent
(KCS); purulent (bacterial).

Conjunctivitis

Primary conjunctivitis attributable to infectious pathogens is
exceedingly rare in dogs.6  In contrast to canine
conjunctivitis, feline conjunctivitis is almost always primary and
attributable to infectious pathogens (viral, chlamydial, or
bacterial).7-9  Bacterial conjunctivitis in dogs
almost always occurs secondary to an underlying disease that alters
normal resident conjunctival flora and favors bacterial
proliferation.  Common causes of conjunctivitis in the dog
include:

Allergy/Hypersensitivity - associated with
atopy and other forms of allergic dermatitis.

a.  Follicular conjunctivitis: usually
from chronic antigenic stimulation (entropion, allergy).
Small, clear vesicles are typically present in the ventral
conjunctival cul-de-sac of young, large-breed dogs.  Topical
treatment with corticosteroids is indicated.  In severe, acute
situations, allergic conjunctivitis may cause a serous ocular
discharge and profound chemosis. In chronic cases, hyperemia and
mucoid discharge are more typical and less likely to resolve in
response to topical corticosteroid administration.

b.  Plasma cell conjunctivitis occurs
most frequently in German shepherds and appears as a thickened,
“cobblestone” appearance to the surface of the nictitating
membrane.  It may occur in conjunction with subepithelial
corneal infiltration (pannus).  This is a treatable disease but
is not curable.  Topical corticosteroids and/or topical
cyclosporine are indicated.

Common causes of conjunctivitis in the cat
include:

1.  Herpesvirus (FHV-1).  Feline
herpesvirus-1 is the most common cause of conjunctivitis in
cats.7-8  It may appear similar clinically to
chlamydial conjunctivitis but chemosis is not dramatic except in
young cats or naïve adults.  In young cats, the disease is
bilateral but is usually unilateral in adult cats.  The virus
establishes latency in neurosensory ganglia and recurrences are
common.  In young kittens, symblepharon formation or KCS may
occur secondary to ulcerative disease.  FHV-1conjunctivitis
usually has a clinical course of 10-21 days, but persistent
infection is possible.  Immunosuppression (FIV, FeLV, stress,
and treatment with corticosteroids or immunosuppressive drugs) may
be evident in chronically affected cats.  Diagnosis is based
primarily on typical clinical signs and results of PCR testing is
supportive of the diagnosis.  Topical tetracycline may be
prescribed for cats with mild acute disease to prevent secondary
Mycoplasma overgrowth.  Antiviral drugs (trifluridine)
should be administered to cats with severe acute or chronic,
unresponsive disease.  Recent evidence suggests that L-lysine
(250 –500 mg PO, q 12 h) is effective in preventing shedding of the
virus and decreasing the severity of clinical signs in
experimentally infected cats.10-11

2.  Chlamydia – Chlamydiophila
felis is a primary conjunctival pathogen in cats.
Chlamydiosis may be associated with upper respiratory disease in
adolescent cats but is rarely clinically evident in adult
cats.  The hallmark signs of chlamydial conjunctivitis is
chemosis that begins unilaterally but becomes bilateral in 4-7
days.8  Another clinical sign described as being
suggestive of chlamydiosis is conjunctival lymphoid follicle
formation.  Conjunctival cytology may reveal inclusion bodies
during the acute disease.  Chlamydia can be diagnosed
from conjunctival scraping samples by PCR testing.
Immunofluorescent antibody IFA, which used to be the “gold
standard,” is still offered by many diagnostic laboratories.
If selected as diagnostic test, do not instill fluorescein prior to
collection of samples for IFA analysis; doing so will result in
false positive test results.  Treatment requires administration
of topical tetracycline (mature cats) or chloramphenicol (juvenile
cats) q 6 h for 14 - 21 days.

3.  Mycoplasma - In cats,
Mycoplasma felis has been incriminated in causing
conjunctivitis, but may be normal resident bacteria of the feline
conjunctiva.  Attempts to experimentally induce mycoplasmal
conjunctivitis in cats is invariably unsuccessful.  Mycoplasmal
conjunctivitis in cats may occur secondary to viral (feline
herpesvirus-1, FHV-1) or chlamydial conjunctivitis.
Mycoplasma is an opportunistic organism and may be
responsible for bacterial overgrowth in concert with other ocular
disease (FHV-1, Chlamydia).  Mycoplasma felis is
frequently susceptible to tetracycline, gentamicin, or
chloramphenicol.

4.  Calicivirus – is a very rare cause
of conjunctivitis in cats.8  Most reports detail
experimental infection, not naturally occurring infection.

5.  Eosinophilic conjunctivitis.
Eosinophilic conjunctivitis is characterized by raised follicles in
the bulbar conjunctiva near limbus, or a more generalized thickened,
friable conjunctival surface.12  Concurrent corneal
stromal infiltration may be evident.  Cytologic examination of
samples acquired from conjunctival scraping reveals
eosinophils.  Approximately 76%  of cats with eosinophilic
keratitis are positive by PCR analysis for FHV-1.
13  I recommend treating with topical alpha interferon (
1 drop q 6 h) and L-lysine 250 mg PO, q 12 h.

Conjunctival Foreign Bodies

Foreign bodies may become trapped behind the nictitating membrane
and induce conjunctival irritation and inflammation, and ulceration
of the ventronasal cornea.  Always evaluate behind the
nictitating membrane after topical anesthetic is instilled.
Foreign body should be removed using fine forceps and treatment with
a broad-spectrum topical and oral antibiotic is indicated.

Abnormalities of the Nictitating Membrane

Movement or protrusion of the nictitating membrane is passive in
the dog.  Protrusion occurs secondary to retraction of the
globe into the orbit which causes forward displacement of orbital
fat and protrusion of the membrane. The cat is capable of active
protrusion of the nictitating membrane.  The nictitating
membrane has sympathetic innervation which acts to retract the
membrane.  Sympathetic denervation (Horner’s syndrome) results
in protrusion of the membrane.  Excursion of the membrane
distributes the tear film and protects the cornea.  The
palpebral surface can be examined by retropulsion of the globe.
Examination of the bulbar surface requires topical anesthesia and
gentle use of non-toothed forceps.

Congenital Abnormalities

1.  Encircling third eyelids -
considered a normal in the American Cocker spaniel.

2.  Congenital hypopigmentation -
often misdiagnosed as protrusion when unilateral.

3.  Eversion or Inversion of the
Cartilage – Abnormalities of the cartilage of the nictitating
membrane occurs most frequently in the Great Dane, Irish Wolfhound,
St. Bernard, and German shorthaired pointer.  A scroll-like
curling of the cartilage results in inward or outward rolling of the
nictitating membrane.  This may result in decreased function
and chronic irritation due to exposure.  Epiphora may result if
tear outflow is compromised.  Treatment requires careful
excision of the abnormally scrolled segment of cartilage.
Scrolled cartilage may occur concurrently with prolapsed gland of
the nictitating membrane.

Acquired Abnormalities

1.  Prolapse of the Gland of the
Nictitating Membrane (“cherry eye”) - occurs secondary to weak
supportive connective tissues which normally anchor the base of the
gland to the ventral orbital rim.  The gland may subsequently
undergo hypertrophy after prolapse.  The Beagle, English
bulldog, Boston terrier, Cocker spaniel, and Shar Pei are
predisposed.  It is important to note that all breeds that are
predisposed to prolapse of the gland of the nictitating membrane are
also predisposed to development of keratoconjunctivitis sicca
(KCS).  Excision may predispose dogs to development of
KCS.  For this reason, the preferred treatment is replacement
of the gland.  Restoration of the gland to its normal position
preserves tear production.  Techniques described2
for replacement include suturing the gland to: 1) adjacent sclera;
2) extraocular muscle tendon; 3) ventral endorbita of the orbital
rim.  The best technique to use in instances where the gland
has recently prolapsed or has not been surgically replaced
previously is the conjunctival imbrication (“Pocket”)
technique.14

2.  Protrusion of the Nictitating
Membrane

Protrusion may occur secondary to:

active retraction of the globe (ocular pain
response)

orbital mass effect (e.g., a space-occupying mass
in the orbit)

loss of orbital mass (starvation,
dehydration—always bilateral)

sympathetic denervation (Horner’s syndrome)

decreased ocular mass (microphthalmia, phthisis
bulbi)

skull conformation-related phenomenon
(dolichocephalics)

dysautonomia

tetanus

gastrointestinal disease (parasites, diarrhea)

3.  Neoplasia

Neoplasia of the nictitating membrane is uncommon
in small animals.  Adenoma/adenocarcinoma of the gland of the
nictitating membrane, melanoma, fibrosarcoma, and lymphoma have been
reported in dogs and cats.  The only indication for removal of
the entire third eyelid is confirmed neoplasia.

References

Angarano DW. Dermatologic disorders of the eyelid
and periocular region. In: Kirk RW, ed: Current Veterinary
Therapy X.  Philadelphia: WB Saunders, 1989, pp.
678-681.

Moore CP, Constantinescu GM. Surgery of the
adnexa.  Vet Clin N Am Small Anim Prac 27(5):1011-1066,
1997.

Bedford PGC. Diseases and surgery of the canine
eyelid. In: Gelatt KN, ed: Veterinary Ophthalmology
3rd ed. Philadelphia: Lea & Febiger, 1999,
pp.535-568.

Roberts SM, Severin GA, Lavach JD. Prevalence and
treatment of palpebral neoplasms in the dog: 200 cases
(1975-1983).  J Am Vet med Assoc 189:1355, 1986.

McLaughlin, SA, Whitley RD, Gilger BC, et
al.  Eyelid neoplasm in cats: a review of demographic data
(1979-1990). J Am Vet med Assoc 29:63-67, 1993.

Gilger BC. Diagnosis and treatment of canine
conjunctivitis. In: Bonagura JD, ed. Kirk’s Current Veterinary
Therapy XIII Small Animal Practice.  Philadelphia: WB
Saunders, 2000, pp.1053-1054.

Stiles J. Feline Herpesvirus. Vet Clin N Am
Small Anim Prac 30(5):1001-1014, 2000.

Ramsey DT. Feline chlamydia and calicivirus
infections.  Vet Clin N Am Small Anim Prac
30(5):1015-1028, 2000.

Whitley RD. Canine and feline primary ocular
bacterial infections.  Vet Clin N Am Small Anim Prac
30(5):1151-1167, 2000.

Maggs DJ, Collins BK, Thorne JG, et al. Effects
of L-lysine and L-arginine on in vitro replication of feline
herpesvirus type-1.  Am J Vet Res
61(12);1474-1478:2000.

Stiles J, Townsend W, Rogers Q, et al. The effect
of L-lysine on the course of feline herpesvirus conjunctivitis.
Proc Am Coll Vet Ophthalmol 31;30:2000.

Pentlarge VW. Eosinophilic conjunctivitis
in  five cats. J Am Anim Hosp Assoc 27;21-28:1991.

Nasisse MP,  Luo H Wang YJ, et al. The role
of feline herpesvirus-1 (FHV-1) in the pathogenesis of corneal
sequestration and eosinophilic keratitis. Proc Am Coll Vet
Ophthalmol 27;80:1996.

Morgan RV, Duddy JM, McClurg K. Prolapse of the
gland of the third eyelid in dogs: A retrospective study of 89
cases(1980-1990). J Am Anim Hosp Assoc 29;56-62:1993.

Figure Legends

Figure
1.  Agenesis (coloboma) of the upper lateral 2/3 of
the eyelid is evident in this 6-month-old cat.  Only the
upper medial 1/3 of the lid is present.  Trichiasis and
fibrovascular keratitis are also present.

Figure
2.  Ophthalmia neonatorum is present in this
16-day-old German Shepherd puppy.  Purulent exudate is
emanating from the medial aspect of the palpebral fissure
after gently massaging the fused lids with a moist, warm
cotton ball.

Figure
3.  Two dermoids of the lower eyelid are present in
this 5-month-old Shetland Sheepdog.  Surgical excision
and a blepharoplastic procedure were necessary to correct the
defect.

Figure
4.  Distichiasis is characterized by cilia arising
from the Meibomian gland openings along the eyelid
margin.  Distichia in this dog resulted in profound
epiphora but the cornea appeared normal

Figure
5.  A chalazion (arrow) is present secondary to a
Meibomian gland adenoma (small arrow) of the upper eyelid of
this dog.

Figure
6.  Meibomitis is characterized clinically as yellow
to cream colored purulent material emanating from the
Meibomian gland openings along the eyelid margin.
Blepharitis is also present

Figure
7.  A histiocytoma of the central part of the lower
eyelid is present in this 9-month-old male Miniature
Schnauzer.  The histiocytoma regressed spontaneously
without
treatment.

AUTHOR
INDEX

Vision
in Animals - What do Dogs and Cats See?

The
Histologic Basis of Ocular Disease

Diseases
of the Lens and Cataract Surgery

Diagnostic
Examination of the Eye

Medical
Vs. Surgical Treatment Of Corneal Disease

Conditions
of the Eyelids and Ocular Adnexa in Dogs and Cats

Diagnostic
and Therapeutic Approach to Orbital Disease in Dogs and
Cats

Glaucoma:
Diagnosis and Therapy

Feline
Ophthalmology

Exotic
Animal Ophthalmology

History
Of Veterinary Ophthalmology With Particular Emphasis For
Ohio

Clinical
Syndromes In Canine And Feline Uveitis

Examination
and Interpretation of the Fundus

Retinal
Disease, Degeneration And Diagnosis.

Main : Conditions of the
Eyelids and Ocular Adnexa in Dogs and Cats

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