The Third Eyelid Flashcards

1
Q

The third eyelid: Location

A

In the medial canthus

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2
Q

The third eyelid: Position is determined by…

A

Sympathetic tone

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3
Q

The third eyelid: Controlled by which muscle?

A

Muscle of nicitans

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4
Q

The third eyelid: Gland of the third eyelid

A

Nictitans gland

  • Bottom of the nictitans
  • Seromucoid; 30-50% of the PTF is formed here
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5
Q

The third eyelid: T-shaped cartilage

A
  • Cartilaginous skeleton
  • Embedded at the base of the nictitans gland
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6
Q

The third eyelid: Function

A
  • Production of fluid for PTF
  • Distribute PTF by blinking
  • Protect the cornea
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7
Q

Protrusion of the third eyelid gland: Alternative name

A

Cherry eye syndrome

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8
Q

Protrusion of the third eyelid gland: Seen mostly in which species

A

Dog

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9
Q

Protrusion of the third eyelid gland: Aetiology

A

Defect/ laxity in the retinaculum which binds the gland & nictitans to the periorbita

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10
Q

Protrusion of the third eyelid gland: Predisposition

A

Breed & age disposition in dogs

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11
Q

Protrusion of the third eyelid gland: CSx

A
  • Reddish mass in the medial canthus
  • Uni-/Bilateral
  • Swelling, drying and inflammation of the prolapsed gland
  • Lacrimation
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12
Q

Protrusion of the third eyelid gland: Aim of treatment

A
  • Secure tear production
  • Decrease inflammation-irritation
  • Improve the cosmetics of the animal
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13
Q

Protrusion of the third eyelid gland: Treatment

A

Surgical replacement of the prolapsed gland

  • Morgan’s pocket method

YOU MUST NEVER REMOVE THE GLAND IF PROLAPSED

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14
Q

Eversion of the T-shaped cartilage: Performed in which species?

A

Dog

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15
Q

Eversion of the T-shaped cartilage: Aetiology

A
  • Developmental abnormality
  • Greater growth rate of the vertical portion of the T-shaped cartilage on the inner surface
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16
Q

Eversion of the T-shaped cartilage: CSx

A
  • Uni-/bilateral
  • Deformed/everted part of the cartilage is seen ventral to the conjunctiva
  • May be combined with gland prolapsus
17
Q

Eversion of the T-shaped cartilage: Aim of treatment

A

Improve cosmetics of the animal

18
Q

Eversion of the T-shaped cartilage: Treatment

A

Dissection of the curved portion

19
Q

Eversion (prolapse) of the third eyelid: Causes

A
  • Systemic backgrounds
  • Horner’s syndrome (cats & dogs)
  • Tetanus
  • Myositis eosinophilica
  • Microphthalmia
  • Exophthalmus
  • Idiopathic
20
Q

Eversion (prolapse) of the third eyelid: Horner’s syndrome

A

Sympathetic denervation; Unilateral

  • Prolapse of the third eyelid
  • Enophthalmus
  • Ptosis
  • Miosis
21
Q

Eversion (prolapse) of the third eyelid: Tetanus (pathogenesis)

A
  1. Spasm of the muscles
  2. Spasm of m. retractor bulbi
  3. Enophthalmus
  4. Bilateral eversion of the third eyelid
22
Q

Eversion (prolapse) of the third eyelid: Myositis eosinophilica

A

Seen mostly in dogs

  • Enophthalmos/exophthalmos together with third eye prolapse
  • Unilateral/Bilateral
23
Q

Eversion (prolapse) of the third eyelid: Microphthalmia

A
  • Developmental abnormality (uni-/bilateral)
  • Physiological in Collies & Doberman
24
Q

Eversion (prolapse) of the third eyelid: Exophtalamos (causes)

A
  • Myositis eosinophilica
  • Retrobulbar masses
  • Tumour
  • Cyst
25
Q

Eversion (prolapse) of the third eyelid: Idiopathic (prediposition)

A

Cats

26
Q

Traumatic injury to the third eyelid: CSx

A
  • Haemorrhage
  • Laceration
  • Haematoma
  • Prolapse
  • Impaired function
27
Q

Traumatic injury to the third eyelid: Treatment

A
  • Reconstructive surgery
  • If inoperable: Exstirpation of the nictitans
28
Q

Tumours of the third eyelid: Summary

A
  • Rare
  • Carcinomas are the most frequent
  • Seen in older animals
29
Q

Tumours of the third eyelid: CSx

A
  • Generally unilateral
  • Third eyelid is prominent, deformed, painful & haemorrhagic
  • Function is impaired
30
Q

Tumours of the third eyelid: Treatment

A
  • Surgical excision/extirpation of the third eyelid
  • (Radiotherapy)
31
Q

What are the only indications for the extirpation of the entire third eyelid?

A
  • Irreparable traumatic injury
  • Malignant tumour