Diseases of adnexa and nasolacrimal system

Question 1

Describe the anatomy of the equine eyelid

Answer 1

Outer skin contains hair and sebaceous glands
-Musculofibrous layer contains muscle and connective tissue (tarsal plate-area that is more dense-important to include when suturing)
-palpebral conjunctiva

Upper eyelid is larger longer and more mobile than the lower

Question 2

What nerves innervate the eyelids in horses?

Answer 2

Sensory: branches of trigeminal nerve
Motor: Facial nerve with some input from the oculomotor nerve

Question 3

What are the actions of the orbicularis oculi muscle and the levator palpebrae superioris?

Answer 3

Orbicularis oculi: facilitates eyelid closure

Levator palpebrae superioris: Pulls the eyelid open

Question 4

What are the functions of the eyelid?

Answer 4

1. Direct protection of the eye through blinking
2. Entrapment and removal of material
3. Distribution of tears
4. Production of glandular secretions (Meibomian glands) contributing to the tear film

Question 5

Describe the nictitating membrane

Answer 5

A T shaped cartilage covered by a mucous membrane
-contains the gland of the third eyelid

*Movement of the third eyelid is indirect- passively covers eye with retraction of the globe

Question 6

What are the different components of the conjunctiva?

Answer 6

Palpebral- the conjunctiva that lines the eyelids
Bulbar- the conjunctiva that covers the globe
Fornix: a blind sac or junction of the above
Fornix of the third eyelid: the junction of the conjunctiva that covers the third eyelid and palpebral conjunctiva

Question 7

What is entropion?

Answer 7

Inversion of the eyelid margin
-results in hair contacting the cornea (typically occurs with the lower eyelid)
-one of the most common congenital abnormalities in foals
-any breed can be affected but particularly affects thoroughbreds and quarterhorses
-clinical signs include epiphora, blepharospasm, conjunctivitis, keratitis, and corneal ulcers
-often occurs along with congenital or another underlying disease such as dehydration or neonatal maladjustment syndrome

Question 8

What is the temporary treatment for entropion?

Answer 8

Temporary tacking sutures
-vertical mattress 4-6 nonabsorbable monofilament sutures (2-3 typically adequate)
-goal is to roll the eyelid margin away from corneal contact
-leave sutures in for 2-3 weeks

Question 9

When should you pursue permanent correction in entropion cases?

Answer 9

-rarely require
-can occur with scarring if temporary entropion is not dealt with early enough

Holtz Celsus procedure: make first incision 2-2.5 mm from and parallel to the eyelid margin, extending slightly medial and lateral to the region of entropion
-second incision defines amount of skin to remove
-excise skin and underlying strip of the orbicularis m
-close with simple interrupted (start in the middle and work out)
**try to avoid over correction which can lead to permanent ectropion

Question 10

What are the most common causes of eyelid lacerations in horses?

Answer 10

-can occur from blunt trauma (irregular laceration with substantial swelling, usually not full thickness)
-can occur from direct contact with sharp objects (focal, straight lacerations)
-can be rips of the eyelid after getting caught on something (more common on upper eyelid)

Question 11

Describe the treatment for eyelid lacerations

Answer 11

Treat with prompt intervention, goal is to achieve functional and cosmetic eyelid
-use standing sedation or general anesthesia ( + local blocks to achieve akinesia and analgesia)
-clean wound with saline or dilute betadine
-minimal debridement (do not excise tissue, freshen/scrape edges with blade, preserve the eyelid margin
-primary closure with eyelid margin alignment is critical
-2 layer closure: tarsoconjunctival layer (absorbable) and musculocutaneous layer (non absorbable)
-try to appose margins perfectly with figure 8 suture
-consider tarsorrhaphy if you want to limit mobility

Question 11

What should you do post operatively to protect the eye after an eyelid laceration repair?

Answer 11

-use protective mask
-give triple antibiotic ointment every 8 hours for 1-2 weeks
-systemic NSAIDs can be used and taper them accordingly
-can consider systemic antibiotics if concerned about establishing infection

Question 12

What can occur with improper repair of eyelid laceration?

Answer 12

-corneal ulcers due to suture rubs
-poor tear film retention or dispersion leading to chronic keratitis

Question 13

What are the some signs of facial paresis/paralysis?

Answer 13

-ptosis/diminished ability to blink
-ear droop and diminished motility
-nose deviation (acute vs chronic)
-flaccid lip/diminished function

Can occur due to trauma, inflammation of the inner ear, guttural pouch or salivary gland, or fracture of the stylohyoid, petrous temporal bone or ramus of the mandible

Question 14

What is the treatment and prognosis associated with facial paresis/paralysis?

Answer 14

Treatment:
-topical lubrication 4-6 times daily (artificial tears)
-topical management of ulcers if present
-partial temporary tarsorrhaphy
-manage underlying conditions

Prognosis:
-depends on cause
-most traumatic cases resolve in 3-4 weeks, prognosis declines significantly after this
-consider permanent partial eyelid closure in non-resolving cases

Question 15

What are the signs of conjunctivitis? What causes it?

Answer 15

-inflammation of the palpebral and/or bulbar conjunctiva
-causes hyperemia, chemosis and ocular discharge

Primary conjunctivitis is uncommon, usually a secondary issue as a result of eosinophilic response, allergy, bacterial, fungal, viral or parasitic infection, or solar exposure

-diagnose on cytology or culture, treatment depends on underlying cause

Question 16

Define a sarcoid. What is the signalment and prognosis?

Answer 16

The most common neoplasm of horses. It is a tumor of fibroblastic origin (can involve subdermal or dermal tissue)
-usually occurs in young horses. QHs, appaloosas and Arabians are at higher risk, standardbreds have decreased risk
-prognosis: metastasis is rare, recurrence is very common especially with excision alone
-generally try to leave these alone if possible, especially if around the eye

Question 17

What is the most common neoplasm of the equine eye and ocular adnexa?

Answer 17

Squamous cell carcinoma
-second most common tumor overall
-often involves the third eyelid (most curable), the medial canthus, the limbus, and the eyelid
-these are locally invasive and slow to metastasize
-predilection to affect draft breeds, appaloosas, paints and color dilute horses (aka horses with light hair and minimal skin pigmentation)

Question 18

What are the types and progression associated with SCC of the eye?

Answer 18

Solar elastosis- no neoplastic changes at this point

Carcinoma in situ- have yet to breach the basement membrane of the cornea

Invasive SCC-have breached the basement membrane of cornea

Question 19

What are the treatment options for SCC?

Answer 19

Surgical excision alone (associated with 50-60% recurrence)
-adjunctive trts: cryosurgery, radiation, hyperthermia, immunotherapy, chemotherapy, photodynamic therapy

Question 20

What is nasolacrimal atresia?

Answer 20

-when the nasolacrimal duct did not form normally leading to a imperforate nasal punctum
-most common congenital nasolacrimal abnormality in foals
-results in severe epiphora (discharge usually becomes mucopurulent due to secondary bacterial overgrowth (dacryocystitis)

Question 21

How do you diagnose and treat an imperforate nasal punctum?

Answer 21

Diagnosis: can be through direct visualization, inability to flush NL duct (need to flush from the eye side), contrast radiography and/or culture/susceptibility

Treatment: Create nasal punctum by passing a catheter and cutting, or flush and cut over the bleb created
-prevent re-obstruction through suturing catheter in place within the NL system (leave in for 4-6 weeks)
-treat secondary infection

Question 22

Describe acquired nasolacrimal obstruction

Answer 22

-often suspected as a cause of epiphora but it is an uncommon disorder
-clinical features include epiphora or mucopurulent discharge
-diagnose through the Jones test, flushing of NL duct and culture
-treat through flushing and topical antibiotics
-NOT PAINFUL

**more commonly the epiphora is more commonly due to equine recurrent uveitis which is painful