The Third Eyelid Flashcards
The third eyelid: Location
In the medial canthus
The third eyelid: Position is determined by…
Sympathetic tone
The third eyelid: Controlled by which muscle?
Muscle of nicitans
The third eyelid: Gland of the third eyelid
Nictitans gland
- Bottom of the nictitans
- Seromucoid; 30-50% of the PTF is formed here
The third eyelid: T-shaped cartilage
- Cartilaginous skeleton
- Embedded at the base of the nictitans gland
The third eyelid: Function
- Production of fluid for PTF
- Distribute PTF by blinking
- Protect the cornea
Protrusion of the third eyelid gland: Alternative name
Cherry eye syndrome
Protrusion of the third eyelid gland: Seen mostly in which species
Dog
Protrusion of the third eyelid gland: Aetiology
Defect/ laxity in the retinaculum which binds the gland & nictitans to the periorbita
Protrusion of the third eyelid gland: Predisposition
Breed & age disposition in dogs
Protrusion of the third eyelid gland: CSx
- Reddish mass in the medial canthus
- Uni-/Bilateral
- Swelling, drying and inflammation of the prolapsed gland
- Lacrimation
Protrusion of the third eyelid gland: Aim of treatment
- Secure tear production
- Decrease inflammation-irritation
- Improve the cosmetics of the animal
Protrusion of the third eyelid gland: Treatment
Surgical replacement of the prolapsed gland
- Morgan’s pocket method
YOU MUST NEVER REMOVE THE GLAND IF PROLAPSED
Eversion of the T-shaped cartilage: Performed in which species?
Dog
Eversion of the T-shaped cartilage: Aetiology
- Developmental abnormality
- Greater growth rate of the vertical portion of the T-shaped cartilage on the inner surface
Eversion of the T-shaped cartilage: CSx
- Uni-/bilateral
- Deformed/everted part of the cartilage is seen ventral to the conjunctiva
- May be combined with gland prolapsus
Eversion of the T-shaped cartilage: Aim of treatment
Improve cosmetics of the animal
Eversion of the T-shaped cartilage: Treatment
Dissection of the curved portion
Eversion (prolapse) of the third eyelid: Causes
- Systemic backgrounds
- Horner’s syndrome (cats & dogs)
- Tetanus
- Myositis eosinophilica
- Microphthalmia
- Exophthalmus
- Idiopathic
Eversion (prolapse) of the third eyelid: Horner’s syndrome
Sympathetic denervation; Unilateral
- Prolapse of the third eyelid
- Enophthalmus
- Ptosis
- Miosis
Eversion (prolapse) of the third eyelid: Tetanus (pathogenesis)
- Spasm of the muscles
- Spasm of m. retractor bulbi
- Enophthalmus
- Bilateral eversion of the third eyelid
Eversion (prolapse) of the third eyelid: Myositis eosinophilica
Seen mostly in dogs
- Enophthalmos/exophthalmos together with third eye prolapse
- Unilateral/Bilateral
Eversion (prolapse) of the third eyelid: Microphthalmia
- Developmental abnormality (uni-/bilateral)
- Physiological in Collies & Doberman
Eversion (prolapse) of the third eyelid: Exophtalamos (causes)
- Myositis eosinophilica
- Retrobulbar masses
- Tumour
- Cyst
Eversion (prolapse) of the third eyelid: Idiopathic (prediposition)
Cats
Traumatic injury to the third eyelid: CSx
- Haemorrhage
- Laceration
- Haematoma
- Prolapse
- Impaired function
Traumatic injury to the third eyelid: Treatment
- Reconstructive surgery
- If inoperable: Exstirpation of the nictitans
Tumours of the third eyelid: Summary
- Rare
- Carcinomas are the most frequent
- Seen in older animals
Tumours of the third eyelid: CSx
- Generally unilateral
- Third eyelid is prominent, deformed, painful & haemorrhagic
- Function is impaired
Tumours of the third eyelid: Treatment
- Surgical excision/extirpation of the third eyelid
- (Radiotherapy)
What are the only indications for the extirpation of the entire third eyelid?
- Irreparable traumatic injury
- Malignant tumour
