eyelid structure or conformation may be congenital or acquired.
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.
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.
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.
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
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.
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).
(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
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.
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
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.
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.
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.
Districhiasis. Districhiasis is defined as two or more cilia emanating
from a single Meibomian gland opening. For treatment see Distichiasis
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.
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
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.
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.
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.
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
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
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,
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.
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
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
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.
It is important to differentiate conjunctival from episcleral hyperemia/injection.
Conjunctival vasculature can be differentiated from underlying episcleral
vasculature based on several characteristic differences:
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
d) will blanch when a sympathomimetic (e.g. phenylephrine) is applied
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
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
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
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.
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.
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
- chronic irritation (trichiasis, ectopic cilia,
keratoconjunctivitis sicca [KCS]) or inflammation may result in
hyperpigmentation of the conjunctival epithelium.
Ocular Discharge - varies with the type of disease: serous (viral,
allergic); mucoid to mucopurulent (KCS); purulent (bacterial).
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
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
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
Common causes of conjunctivitis in the cat include:
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
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.
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.
Calicivirus – is a very rare cause of conjunctivitis in cats.8 Most
reports detail experimental infection, not naturally occurring infection.
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
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.
Encircling third eyelids - considered a normal in the American Cocker
Congenital hypopigmentation - often misdiagnosed as protrusion when
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.
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
Protrusion of the
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)
• gastrointestinal disease (parasites, diarrhea)
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
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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.
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College of Veterinary Medicine
Ohio State University
Eyelid neoplasms are the most frequent group of ophthalmic neoplasms in dogs. Adenoma and adenocarcinoma of the meibomian gland are the most common lid neoplasms (~60%); local disfigurement and irritation necessitate local excision, which is usually successful. Sebaceous adenocarcinomas are locally invasive and histologically malignant but are not known to
metastasise. Lid melanomas, exhibited as spreading pigmented masses on the eyelid margins, should be widely excised. Other frequent eyelid neoplasms include histiocytoma, mastocytoma, and papilloma.
Orbital neoplasms in dogs produce exophthalmia, conjunctival and eyelid swelling, strabismus, and exposure keratitis. The globe cannot be retropulsed. Usually, there is no pain. Because ~90% of the neoplasms are malignant and ~75% arise within the orbit, the prognosis for longterm survival is often poor. The neoplasm type should be determined histologically, and the extent of the mass determined by physical examination, skull radiographs (including special contrast procedures, computed tomography, and MRI), and ultrasonography before treatment by surgical excision or radiation. Excision of the orbital mass with the globe and all orbital tissues (including adjacent bone) may decrease the possibility of recurrence.
Corneal and limbal neoplasms are uncommon in dogs and can be confused with nodular fasciitis and proliferative keratoconjunctivitis in Collies. Limbal or epibulbar malignant melanomas are focal, usually superficial, pigmented masses that extend both onto the cornea and caudally toward the globe’s equator. After close intraocular examination, including gonioscopy and B-scan ultrasonography, to detect possible penetration of the sclera, partial- to full-thickness surgical excision with scleral grafts, cryotherapy, or laser photocoagulation is usually successful. If intraocular extension occurs, enucleation is performed.
Malignant melanomas are the most common uveal neoplasm, are usually pigmented, and most frequently involve the iris and ciliary body. Clinical signs of anterior uveal melanomas may include an obvious mass, persistent iridocyclitis, hyphema, glaucoma, and pain. Ciliary body adenoma and adenocarcinoma are the most frequent epithelial neoplasms of the anterior uvea. Signs may include hyphema, glaucoma, and usually a
non-pigmented mass behind the iris and in the pupil. Neoplasms of neuroectodermal origin are rare. Treatment is usually enucleation. Recent studies in iridal melanomas, especially in Labrador Retrievers, suggest
non-invasive diode laser photocoagulation may be effective and can be repeated if necessary. Secondary uveal adenocarcinomas are relatively infrequent and originate from a number of distant sites. Other neoplasms such as the transmissible venereal tumor and hemangiosarcoma may
metastasise to the anterior uvea. Lymphosarcoma frequently involves the anterior uvea and other ocular structures, and may present as bilateral disease. Systemic therapy with topical and/or systemic anti-inflammatory treatment for intraocular lymphoma may be attempted using one of several available lymphoma protocols (eg, Madison, WI or Animal Medical
Centre: combination of cyclophosphamide, prednisolone, vincristine, and/or doxorubicin), but dogs with intraocular lymphoma have shorter survival times.