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Vet 245 Ophthalmology Quiz Notes

Epiphora, eyelid disorders, and corneal conditions

  • Epiphora (overflow of tears)

    • Definition: excessive tearing beyond drainage capacity or due to ocular irritation.
    • Relevance: Common presenting sign in multiple canine/feline ophthalmic conditions; warrants assessment of tear production, drainage, and ocular surface irritation.

  • Ectopic cilia: diagnostic approach

    • Question: Which diagnostic test would be most useful in a case of ectopic cilia?
    • Answer: Fluorescein Dye Test (FDT).
    • Rationale: FDT helps reveal corneal ulcerations or epithelial defects caused by abnormal lashes irritating the cornea.
    • Other tests (for contrast): Schirmer Tear Test (STT) measures tear production; tonometry assesses intraocular pressure; corneal scraping is invasive and not the first diagnostic choice for ectopic cilia.

  • Entropia

    • Definition: rolling inward of the eyelids (usually the lower eyelid in dogs).
    • Significance: Can cause corneal or conjunctival irritation and damage if untreated.

  • Cherry eye (prolapsed third eyelid gland)

    • Exam statement: “In cherry eye the treatment of choice is surgical excision of the gland.”
    • Practical note: Historically, gland excision was common, but modern practice often preserves the gland via relocation or other techniques to maintain tear production and reduce risk of keratoconjunctivitis sicca.
    • Takeaway: Preservation techniques are generally preferred to maintain lacrimal function; excision can lead to tear film deficiencies.

  • Acute vision-threatening emergency (optic/ocular emergencies)

    • Statement in transcript: If left untreated in emergency situations, this condition can lead to loss of vision within hours.
    • Correct interpretation: This risk is most characteristic of acute glaucoma (angle-closure glaucoma) rather than all emergencies.
    • Related conditions to monitor: rapid pain, corneal edema, iris bombe, and rapidly rising intraocular pressure (IOP).

  • Glaucoma vs other conditions (context from multiple-choice options in transcript)

    • Conditions listed: Uveitis, Glaucoma, Melanoma, Viral Conjunctivitis.
    • Key contrast: Glaucoma is associated with increased intraocular pressure and potential rapid vision loss if not treated; uveitis can be associated with decreased IOP in many cases, though it can vary.

  • Corneal staining with fluorescein: corneal layers and staining pattern

    • Question: Which layer of the cornea does not pick up fluorescein stain when checking for ulcerations?
    • Answer: Endothelium (and by extension Descemet’s membrane behind it) do not take up fluorescein; stain highlights defects in the more superficial layers, particularly the corneal epithelium and, if compromised, the underlying stroma.
    • Practical note: Fluorescein staining is used to identify epithelial defects; a fluorescein-positive area typically corresponds to an epithelial defect with underlying stromal involvement.

  • Treatment protocol for a superficial corneal ulcer OS (left eye)

    • Transcript option selected as correct: Terramycin ointment OS every 4 hours, e-collar.
    • Important reasoning:
    • Avoid steroid-containing products (e.g., NeoPolyDex) in active epithelial ulcers, as steroids can delay healing and increase risk of corneal melting.
    • Terramycin (oxytetracycline) provides broad-spectrum antibiotic coverage suitable for superficial ulcers.
    • Use of an e-collar reduces self-trauma.
    • Other options discussed:
    • NeoPolyDex ointment OS every 2-4 hours narratively includes a corticosteroid; not ideal for epithelial ulcers.
    • Tobramycin drops OU every 4 hours could be used, but systemic analgesia and collar are consistent with standard initial care; however, a labeled plan focusing on a non-steroidal antibiotic ointment is preferred for superficial ulcers.

  • Tear film anatomy: mucous layer production and secretion

    • Question: Where is the mucous layer of tear film produced and secreted?
    • Answer: Conjunctival goblet cells (mucin component of tear film).
    • Contrast with other tear film components:
    • Meibomian glands produce the lipid (outer) layer to prevent evaporation.
    • Lacrimal glands produce the aqueous (middle) layer.
    • Nictitans (third eyelid) provides physical protection and may contribute to tear distribution.

  • Pannus (Chronic Superficial Keratitis) in German Shepherds

    • Case: Prianna Berkins, a 2-year-old intact female German Shepherd, presents with rubbing eyes, corneal granulation tissue near the cornea, mild scleral injection, and mucoid discharge.
    • Most prominent disease: Pannus (Chronic Superficial Keratitis).
    • Pathophysiology: autoimmune/inflammatory process leading to progressive corneal vascularization and pigmented granulation tissue, typically starting on the cornea near the limbus and advancing.
    • Breed tendency: especially common in German Shepherds; signal for long-term management rather than a one-time cure.
    • Management considerations: anti-inflammatory therapy, topical immunomodulators, and regular monitoring; prognosis varies with severity.

  • Intraocular pressure (IOP) changes with uveitis and glaucoma

    • Statement: With uveitis you would expect a decrease in intraocular pressure, and with glaucoma you would expect an increase in intraocular pressure.
    • Clinical correlate:
    • Uveitis often reduces aqueous humor production and can cause anterior chamber cell flare with low IOP.
    • Glaucoma causes impaired aqueous outflow or increased production, leading to elevated IOP.
    • Practical implication: Monitoring IOP is important in diagnosing and differentiating anterior segment diseases; treatment aims to normalize IOP and reduce inflammation where appropriate.

  • Quick-reference abbreviations and terms

    • OS: left eye
    • OU: both eyes
    • OD: right eye
    • STT: Schirmer Tear Test (tear production)
    • FDT: Fluorescein Dye Test (corneal staining/ulcer detection)
    • IOP: intraocular pressure
    • Pannus: chronic superficial keratitis in dogs, notably German Shepherds
    • Epithelium vs Endothelium: epithelial layer is where fluorescein staining indicates defects; endothelium is not stained by fluorescein in routine ulcer assessment

  • Connections to foundational principles

    • Tear film structure and stability rely on a balance of lipid, aqueous, and mucin layers for comfort and corneal health.
    • The cornea comprises multiple layers; staining techniques help localize defects and guide treatment.
    • Early identification and appropriate management of ocular emergencies (glaucoma, severe ulcers) are critical to preserving vision.

  • Practical and ethical considerations in veterinary ophthalmology

    • When choosing treatments, avoid steroid-containing regimens in active corneal ulcers to prevent delayed healing.
    • For conditions affecting tear production (e.g., cherry eye), preserve lacrimal tissue when possible to maintain tear film and ocular surface health.
    • Breed-specific diseases (e.g., pannus in German Shepherds) require tailored long-term management and regular monitoring.

  • Summary of key exam points

    • Epiphora is tearing overflow; consider tear production and drainage issues.
    • Ectopic cilia → FDT is the most useful diagnostic test among the options provided.
    • Entropia is inward curling of the eyelids causing corneal damage risk.
    • Cherry eye treatment is moving toward gland-preserving techniques rather than excision.
    • Acute glaucoma poses a rapid risk to vision; timely IOP management is essential.
    • Fluorescein staining highlights epithelial defects; endothelium does not take up the stain in standard testing.
    • For superficial corneal ulcers in the left eye, Terramycin ointment q4h with an e-collar is a commonly chosen regimen over steroid-containing products.
    • The mucous layer of the tear film is produced by conjunctival goblet cells.
    • Pannus is a common chronic inflammatory keratitis in German Shepherds.
    • In uveitis, expect decreased IOP; in glaucoma, expect increased IOP.