Podcast
Questions and Answers
What is the main function of the cornea?
What is the main function of the cornea?
- Vision
- Protecting the eye
- Light absorption
- Refracting light (correct)
The cornea is completely opaque.
The cornea is completely opaque.
False (B)
What is the thickness range of the cornea in most species?
What is the thickness range of the cornea in most species?
0.5-2mm
The __________ is the anterior limiting membrane of the cornea.
The __________ is the anterior limiting membrane of the cornea.
Which of the following is NOT a congenital disorder of the cornea?
Which of the following is NOT a congenital disorder of the cornea?
Match the following corneal conditions with their descriptions:
Match the following corneal conditions with their descriptions:
The corneal epithelium is replaced every 4-8 days.
The corneal epithelium is replaced every 4-8 days.
Keratitis is the inflammation of the __________.
Keratitis is the inflammation of the __________.
What characteristic distinguishes ciliary blood vessels from conjunctival blood vessels?
What characteristic distinguishes ciliary blood vessels from conjunctival blood vessels?
Corneal ulceration can only be superficial.
Corneal ulceration can only be superficial.
What does hypopyon refer to?
What does hypopyon refer to?
The process by which the normally avascular cornea gets invaded by blood vessels as a defensive mechanism is called __________.
The process by which the normally avascular cornea gets invaded by blood vessels as a defensive mechanism is called __________.
Match the types of superficial keratitis with their descriptions:
Match the types of superficial keratitis with their descriptions:
What is the common treatment for superficial keratitis?
What is the common treatment for superficial keratitis?
Pigmentation of the cornea is a specific response to inflammation.
Pigmentation of the cornea is a specific response to inflammation.
What is the initial symptom of superficial keratitis?
What is the initial symptom of superficial keratitis?
Identify the breed predisposed to degenerative pannus.
Identify the breed predisposed to degenerative pannus.
Superficial keratitis can result in blindness if left untreated.
Superficial keratitis can result in blindness if left untreated.
What treatment is indicated for moderately advanced cases of superficial keratitis?
What treatment is indicated for moderately advanced cases of superficial keratitis?
The condition known as keratoconjunctivitis sicca is secondary to __________ insufficiency.
The condition known as keratoconjunctivitis sicca is secondary to __________ insufficiency.
Match the treatments with their corresponding conditions:
Match the treatments with their corresponding conditions:
Which of the following is a potential cause of pigmentary keratitis?
Which of the following is a potential cause of pigmentary keratitis?
Pigmentary keratitis only occurs in the superficial layers of the cornea.
Pigmentary keratitis only occurs in the superficial layers of the cornea.
What is a symptom of pigmented keratitis?
What is a symptom of pigmented keratitis?
Which of the following is NOT a symptom of interstitial keratitis?
Which of the following is NOT a symptom of interstitial keratitis?
Removal of pigments in pigmentary keratitis is indicated if vision is impaired.
Removal of pigments in pigmentary keratitis is indicated if vision is impaired.
What are two mechanical causes of ulcerative keratitis?
What are two mechanical causes of ulcerative keratitis?
____ is a systemic disease that can cause interstitial keratitis in dogs.
____ is a systemic disease that can cause interstitial keratitis in dogs.
Which treatment method is commonly used for interstitial keratitis?
Which treatment method is commonly used for interstitial keratitis?
Match the cause with its associated type of keratitis:
Match the cause with its associated type of keratitis:
Which of the following is true regarding the treatment of pigmentary keratitis?
Which of the following is true regarding the treatment of pigmentary keratitis?
Corticosteroids are recommended as a treatment for ulcerative keratitis.
Corticosteroids are recommended as a treatment for ulcerative keratitis.
What is the initial treatment step for iris prolapse?
What is the initial treatment step for iris prolapse?
Iris staphyloma involves the protrusion of the iris through a ruptured corneal ulcer.
Iris staphyloma involves the protrusion of the iris through a ruptured corneal ulcer.
What is the treatment for hypopyon?
What is the treatment for hypopyon?
The _____ membrane flap is a treatment option for iris staphyloma.
The _____ membrane flap is a treatment option for iris staphyloma.
Match the following conditions with their treatments:
Match the following conditions with their treatments:
Which treatment is used for anterior synechia?
Which treatment is used for anterior synechia?
In hypopyon, topical antibiotics are ineffective.
In hypopyon, topical antibiotics are ineffective.
What is the purpose of injecting sterile saline solution into the anterior chamber during iris staphyloma treatment?
What is the purpose of injecting sterile saline solution into the anterior chamber during iris staphyloma treatment?
Study Notes
Anatomy of the Cornea
- The cornea is the transparent outer layer of the eye, responsible for focusing light
- It is horizontally elliptical or pear-shaped in horses and cattle, and nearly circular in dogs and cats
- The thickness of the cornea varies between 0.5-2mm and differs from the center to the periphery
- Canine and bovine corneas are thickest at the center, while equine corneas are thickest at the limbus
- The cornea consists of five layers: epithelium, Bowman's layer, stroma, Descemet's membrane, and endothelium
- Epithelium is constantly desquamated and replaced every 4-8 days
- The stroma forms 90% of the thickness of the cornea
- Descemet's membrane is the basement membrane of the endothelium
Congenital Disorders of the Cornea
- Microcornea is an abnormally small cornea
- Macrocornea is a large cornea within an otherwise normal globe
- Dermoids are ectopic pieces of skin present on the cornea or conjunctiva
- Coloboma of the cornea is the absence of a full segment of the cornea, a rare condition
Acquired Disorders of the Cornea
- Keratitis is inflammation of the cornea.
- Symptoms: pain (photophobia, blepharospasm), discharge, conjunctiva and ciliary blood vessel injection, loss of corneal transparency, corneal vascularization, ulceration, pigmentation, hypopyon
- Types of Keratitis:
- Superficial Keratitis:
- Superficial Punctate Keratitis: fine circular to large white opacities
- Superficial Abscesses: green-yellowish swellings, often due to trauma or foreign body
- Pannus: chronic diffuse inflammatory condition, characterized by subepithelial connective tissue infiltration and vascularization
- Keratoconjunctivitis Sicca: secondary to lacrimal gland insufficiency
- Exuberant granulation tissue: builds up on the cornea surface after injury
- Pigmentary Keratitis: pigment deposition in the cornea, often due to irritants like trichiasis, distichiasis, entropion, or prior keratitis
- Interstitial or Deep Keratitis: inflammation of the stroma, Descemet's membrane, and endothelium
- Causes: extension of infection from superficial layers, systemic diseases (canine distemper, infectious hepatitis, leptospirosis), traumatic injuries
- Symptoms: corneal opacity, deep vascularization, conjunctival and ciliary injection, hypopyon
- Ulcerative Keratitis: inflammation of the cornea with ulcer formation
- Causes: mechanical (abrasions, foreign bodies, entropion), infectious (bacterial, viral, fungal, chlamydial), metabolic, neurotrophic
- Treatment:
- Iris Prolapse: protrusion of the iris through a corneal ulcer
- Iris Staphyloma: protrusion of the iris covered with fibrin and epithelium
- Hypopyon: accumulation of inflammatory exudate in the anterior chamber
- Anterior Synechia: adhesions between the iris and corneal endothelium
- Panophthalmitis: severe purulent inflammation of the eyeball
- Superficial Keratitis:
Treatments for Corneal Disorders
- Superficial Keratitis: topical corticosteroids, antibiotics, yellow mercuric oxide
- Superficial Abscesses: opening and suction, curettage, superficial keratectomy
- Pannus: topical corticosteroids, subconjunctival corticosteroids, beta radiation, chemical cauterization, superficial keratectomy, periotomy
- Exuberant Granulation Tissue: periotomy, surgical removal
- Pigmentary Keratitis: elimination of the cause, superficial keratectomy if vision is impaired
- Interstitial Keratitis: topical atropine sulfate, corticosteroids, antibiotics
- Ulcerative Keratitis: topical antibiotics, atropine, surgical repair of wounds
- Iris Prolapse: re-positioning or amputation of the iris, suturing corneal wound, third eyelid flap
- Iris Staphyloma: excision of the protruded iris, suture of corneal wound, nictitating membrane flap
- Hypopyon: paracentesis, aspiration, alfapsin enzyme injection
- Anterior Synechia: atropine, surgery to remove adhesions
- Panophthalmitis: enucleation, exenteration, evisceration
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Description
Explore the intricate anatomy of the cornea, its structure, and its various congenital disorders. Learn about the layers of the cornea, its variations across different species, and specific congenital conditions like microcornea and coloboma. This quiz will enhance your understanding of both normal and abnormal corneal conditions.
