Week 1- Approach to Diseases of the Cornea And Conjunctiva Flashcards
(50 cards)
What contributes to corneal transparency?
Small collagen fiber diameter and lamellar arrangement, absence of blood vessels and pigment, dehydration maintained by endothelium, smooth surface, and high-quality precorneal tear film.
Why does the cornea have more refractive power than the lens?
Because of its curvature and the air-cornea interface, the cornea bends light more significantly than the lens.
List the major pathological corneal responses.
Corneal vascularisation (red), oedema (blue/grey), stromal melting (yellow/white), fibrosis (grey), melanosis (black), WBC infiltration (yellow/green), and stromal mineral/lipid deposition (white).
What is corneal oedema and how does it appear?
It is fluid accumulation in the corneal stroma, appearing blue or grey, often due to endothelial dysfunction or inflammation.
What is stromal melting (corneomalacia)?
A severe degradation of corneal collagen by proteolytic enzymes, often due to infection, leading to structural compromise.
What is pigmentary keratitis (corneal melanosis)?
A non-ulcerative condition with black pigmentation of the cornea, often due to chronic irritation or breed predisposition.
Differentiate between superficial and deep stromal corneal ulcers.
Superficial ulcers involve only the epithelium; stromal ulcers penetrate deeper and may approach Descemet’s membrane.
List some non-ulcerative corneal diseases.
Pannus, KCS, pigmentary keratopathy, eosinophilic keratitis, lipid/mineral dystrophy, endothelial dystrophy, degeneration, dermoid.
What is corneal sequestrum and in which species is it found?
A necrotic area of corneal stroma appearing dark brown/black, unique to cats, often due to chronic irritation.
What does the Schirmer Tear Test 1 (STT1) measure?
The aqueous component of tear film, measured in mm/min without local anaesthetic. Normal in dogs: 15–25 mm/min.
When is STT1 result diagnostic for KCS in dogs?
reading less than 5 mm/min indicates keratoconjunctivitis sicca.
What does tonometry measure?
Intraocular pressure (IOP). Tools include TonoPen (needs anesthesia) and TonoVet (doesn’t need anesthesia).
What are normal IOP values for dogs and cats?
Dogs: 15–25 mmHg, Cats: 12–19 mmHg.
What is the purpose of fluorescein dye in ophthalmology?
To detect corneal ulcers, assess tear film breakup time, evaluate nasolacrimal drainage, and identify aqueous leakage.
What is Rose Bengal dye used for?
Detection of punctate or dendritic ulcers, often caused by herpesvirus.
What does a positive Jones test indicate?
Normal nasolacrimal duct function, seen when fluorescein dye appears at the nostrils.
What are the signs of qualitative tear film deficiency?
Very watery eyes despite corneal dryness, often associated with chronic conjunctivitis or mucin deficiency.
How is cytology collected from the eye?
Use a cytobrush or blunt scalpel to gently scrape lesions after removing discharge and applying anesthesia.
What is the significance of conjunctival hyperemia?
May signal local conjunctivitis or deeper eye disease like uveitis or glaucoma. Requires differential diagnosis.
What is SCCED and what are its synonyms?
Spontaneous Chronic Corneal Epithelial Defect
What breeds are predisposed to SCCED?
Boxers
How does SCCED appear clinically?
Superficial
What is the main treatment goal in SCCED?
Stimulate epithelial-stromal adhesion by removing the hyaline membrane and supporting healing.
