Ophtho1- Cornea

  1. What are the 4 layers of the cornea?
    [superficial] epithelium--> stroma--> Decemet's membrane--> endothelium [deep]
  2. Describe the normal histo properties of the corneal epithelium. (3)
    • non-keratinized, stratified squamous epithelium
    • superficial cells have microvilli
    • basal cells have anchoring fibrils to anchor to stroma
  3. How long after injury does it take for a corneal epithelial injury to heal? What about corneal stromal injury?
    • Epithelial injury heals in 24-48 hours
    • Stromal injury heals in 4-7 months
  4. Describe the physiologic properties of the corneal epithelium and the clinical implications of this.
    lipophilic--> fluorescein is not take up by intact epithelium
  5. Describe the clinical presentation of an epithelial corneal ulcer (superficial). Why does this occur?
    focal corneal edema because lipophilic layer is disrupted and the hydrophilic stroma is exposed and able to absorb tear film fluid
  6. Describe the clinical presentation of a deep corneal ulcer in which the endothelium is damaged.
    diffuse corneal edema
  7. Describe the innervation of the cornea. What are the clinical implications of this?
    • sensory innervation to outer 1/3 of cornea by ophthalmic branch of trigeminal nerve
    • superficial ulcers are more painful than deep ulcers b/c only outer third is innervated
  8. What is Descemet's membrane?
    basement membrane of the endothelium
  9. What is a desmetocele?
    elastic properties allow Descemet's membrane to bulge forward in very deep ulcers
  10. Describe a desmetocele diagnostically.
    donut stain with fluorescein because Descemet's membrane does not stain but the stroma around the edges does
  11. Describe the properties of the endothelial layer of the cornea. (3)
    • post-mitotic (you lose them as you age and they do not regenerate)
    • heal by cellular enlargement and migration
    • when they go below a certain threshold, you get diffuse corneal edema
  12. Describe corneal metabolism. (3)
    • oxygen is mostly from the tear film, some from aqueous humor
    • glucose mostly from aqueous humor, some from tear film
    • waste removal is through aqueous humor
  13. In cats, corneal infection is usually ___________; in dogs, corneal infection is usually ___________.
    viral; aerobic bacteria
  14. What diagnostic test should be a part of the yearly PE in small breed dogs and dogs with bulgy eyes?
    schirmer tear test (these breeds are prone to chronic dry eye)
  15. What is a dermoid/ choristoma?
    "hairy eyeball"; hair on cornea (normal tissue in an abnormal place)
  16. What is infantile corneal dystrophy?
    superficial transient opacity seen in dogs less than 10 weeks old
  17. How can you determine the chronicity of ulcerative keratitis?
    blood vessels in cornea= chronic (>5-7 days)
  18. What is ectopic cilia?
    abherent hair growing toward eye (leads to ulcerative keratitis)
  19. If you look at an ulcer and see depth, then you know...
    it is midstromal or deeper.
  20. What are the levels of corneal ulcers? (5)
    erosion--> superficial--> midstromal--> deep--> desmetocele
  21. Describe superficial corneal ulcers. (2)
    • extremely painful
    • heal within 72 hours of removal of cause
  22. If a superficial corneal ulcer has not resolved i 3-5 days, then... (3)
    • cause is still present
    • ulcer is infected
    • indolent ulcer
  23. What is an indolent ulcer?
    • recurrent, non-healing chronic erosion
    • failure of attachment of the epithelium to the underlying basement membrane
  24. What are the hallmark features of an indolent ulcer? (6)
    • superficial
    • non-painful to mildly painful
    • loose or redundant epithelial borders
    • middle-aged to older dogs
    • chronic
    • boxers predisposed
  25. Why aren't indolent ulcers super painful if they are superficial ulcers?
    don't break the basement membrane and expose the stromal nerve endings
  26. What is the treatment of an indolent ulcer? (4)
    • remove loose, redundant epithelium
    • grid keratotomy (gently break BM with 25g needle)
    • diamond burr
    • topical therapy (tetracycline) (oral doxy works just as well)
  27. The bulk of corneal disease in cats has a relationships to ________.
    Herpes felis
  28. What is ophthalmia neanatorum?
    herpes keratitis in <4 weeks old kittens; bilateral purulent d/c; severe corneal ulceration; often with URI
  29. Describe herpes keratitis in adolescent cats.
    ulcerative keratitis and conjunctivitis, URI, uni- or bi-lateral
  30. Describe herpes keratitis in adult cats.
    classic dendritic ulcer with NO URT signs
  31. How is herpes diagnosed in adult cats?
    dendritic or punctate superficial corneal ulcers is pathognomonic
  32. What causes recrudescence of herpes keratitis in adult cats?
    stress and immunosuppression
  33. What is the treatment for herpes felis?
    • antiviral agents topically (Idoxuridine, Trifluorothymidine, Cidofovir)
    • antivirals systemically (Famciclovir)
    • L-lysine
    • avoid steroids when possible
  34. How do you handle midstromal corneal ulcers?
    there is always associated anterior uveitis- do culture and sensitivity!
  35. What are signs of anterior uveitis? (3)
    pain, constricted pupil, red iris
  36. What is the treatment of anterior uveitis? (4)
    • Topical antibiotics (neomycin-bacitracin-polymyxin) (4th gen cephs- Levofloxacin, Gatifloxacin- second line treatment when neopolybac doesn't work)
    • atropine (as needed to dilate pupil)
    • NSAIDsĀ 
    • NO TOPICAL CORTICOSTEROIDS!
  37. ____________ are contraindicated in all active corneal ulcerative disease.
    Steroids
  38. How do you diagnose a desmetocele?
    • fluorescein negative centrally
    • must do culture and sensitivity
  39. How is a desmetocele treated?
    • perforation is imminent- go to surgery
    • conjunctival flap or corneal-conjunctival transportation (NO THIRD EYELID FLAP)
  40. What does "melting corneal ulcer" mean?
    • enzymatic breakdown of the cornea; enzymes originating from microorganisms, neuts, and cornea itself
    • ALWAYS CULTURE AND CYTOLOGY
  41. What are the most common etiologic agents of melting corneal ulcers? (2)
    Pseudomonas or Strep (can be sterile)
  42. What is the treatment for melting corneal ulcers? (4)
    • same as for deep ulcers but more aggressive
    • Topical antibiotics q1-2hrs(Ofloxacin, Levofloxacin, Gatifloxacin- fluoroquinolones)
    • Anticollagenase (serum frozen sterilely, tetracycline)
    • +/- surgery (debride melting portion)
  43. The only 4 basic changes that can result in a change in corneal transparency (4 that are non-staining/ non-ulcerative):
    • edema
    • pigmentation
    • scar
    • infiltrate (cellular or non-cellular/crystalline)
  44. All corneal lesions result in a ______________.
    decrease in the transparency of the cornea
  45. Differentials for diffuse corneal edema. (4)
    • anterior uveitis
    • glaucoma
    • anterior lens luxation
    • endothelial dystrophy (old chichis and bostons)
  46. A dog comes in with scleral redness and diffusely blue eye. What test do you perform?
    • intraocular pressures!
    • it's either anterior uveitis (normal pressures) or glaucoma (high pressures)
  47. ____________ should be performed in all eyes with diffuse corneal edema.
    Intraocular pressure measurement
  48. Chronic superficial irritation is associated with ___________ and leads to ____________.
    corneal vascularization; corneal pigmentation
  49. What are causes of corneal pigmentation? (3)
    • chronic superficial irritation
    • sequestrum
    • melanoma
  50. Corneal sequestration is unique to _______, especially __[breeds-1]__.
    cats; Persians, Himalayans
  51. When does corneal sequestration occur?
    following chronic irritation or ulceration of the cornea
  52. What does corneal sequestration look like clinically? (4)
    • brown-black corneal lesion
    • painful
    • vascularized
    • fluoroscein negative
  53. Corneal sequestration is associated with ____________ and is exacerbated by ____________.
    herpes; steroids
  54. Never do a(n) ____________ in a cat.
    grid keratotomy
  55. What is the treatment for corneal sequestration in cats? (4)
    • superficial keratectomy +/- conj graft
    • topical antibiotics
    • atropine
    • artificial tears
  56. Epibulbar (limbal) melanoma is generally ___________.
    benign
  57. What clinical findings lead to a diagnosis of a corneal scar? (3)
    • history
    • presence of vascularization
    • lack of pain
  58. Describe nodular granulomatous episclerokeratitis.
    • non-neoplastic, inflammatory mass located at the corneal-sclearal junction
    • made up of lymphocytes, plasma cells, and histiocytes
    • DOGS- cockers, collies
  59. What is the therapy for NGEK? (3)
    • topical steroids (Dex)
    • topical immunosuppressive (Cyclosporin, tacrolimus)
    • systemic immunosuppressives (azathioprine, cyclosporin)
  60. What is chronic superficial keratitis (pannus)?
    immune-mediated disease that begins in the inferior temporal limbus- exacerbated by UV light
  61. Describe pannus clinically.
    • corneal vascularization and pigmentation that will, if not controlled, advance across the entire cornea
    • dogs- GSD, greyhound
  62. What is the therapy for pannus? (3)
    • topical steroids (Dex)
    • topical immunosuppressive (Cyclosporin, tacrolimus)
    • decrease UV exposure
  63. What is eosinophilic keratitis? Describe it clinically.
    • pink-red, raised proliferative lesion with superficial white plaque that invades from the limbus
    • non-painful
    • mast cells and eosinophils on cytology
    • CATS
  64. What is the therapy for eosinophilic keratitis? (3)
    • topical immunosuppressive (Cyclosporin, tacrolimus)
    • topical steroids (Dex)- be careful...cats have herpes!
    • Ovaban- be careful...side effects (DM, mammary carcinoma, pyometra, weight gain)
  65. What kinds of non-cellular corneal infiltrates can you get? (2)
    • cholesterol
    • mineral
    • [crystalline materials]
  66. Non-cellular corneal infiltrates often appear __________ clinically.
    birefringent
  67. How does corneal dystrophy appear clinically? (4)
    • non-painful
    • non-vascularized
    • often bilateral
    • occur in predisposed breeds (hereditary)
  68. What is the therapy for corneal dystrophy?
    none (absolutely no steroids!!)
  69. Corneal degeneration occurs most commonly due to ___________.
    previous corneal inflammation
  70. Causes of corneal degeneration. (6)
    • previous corneal degeneration
    • hypothyroidism
    • hypercholesterolemia of cushings
    • hypercalcemia
    • diabetes
    • chronic topical or systemic steroids
  71. The prognosis for corneal trauma is poor if... (5)
    • laceration involves the limbus
    • significant hyphema is present
    • lens is perforated
    • large uveal prolapse through the incision is present
    • no consensual PLR is present
  72. With corneal perforation/ laceration, if vitreous and retina cannot be visualized, then a(n) _________ is required.
    ultrasound
  73. What is the treatment for corneal perforation/ laceration?
    consider enucleation or prosthesis if no consensual PLR, large uveal prolapse, US shows significant blood in vitreous or retinal detachment
  74. What are the differences between the epithelium and endothelium in:
    a- number of cell layers
    b- mitosis and healing
    c- corneal edema that results from defect
    • a- epithelium is 8-15 cell layers thick; endothelium is 1 cell layer thick
    • b- epithelium heals by mitosis in basal layer (stratified squamous); endothelium does NOT undergo mitosis and heals by cellular enlargement and migration
    • c- damage to epithelium--> focal edema; damage to endothelium--> diffuse edema
  75. How does the cornea maintain deturgescence? What is the role of carbonic anhydrase?
    • cornea maintains deturgescence (relative dehydration) by evaporation of tears, mechanical barriers of endo- and epithelium, Na+K+ATPase pump of endothelium
    • fluid flows down osmotic gradient from corneal stroma to aqueous humor; this gradient is maintained by Na+K+ATPase pump; carbonic anhydrase supplies the needed bicarb ion for co-transport with Na+ into aqueous humor
  76. What are the properties of the cornea that allow it to remain transparent? (4)
    smoothness/ tear film, orderly arrangement of stromal collagen, absence of blood vessels and pigment, and deturgescence
  77. What are 3 categories of drugs used to treat corneal ulcers and reasons for their use?
    • Anticollagenase: used for melting ulcers, inhibit MMPs, and inhibit melting
    • Antivirals: used for herpes keratitis in cats
    • Antibiotics: treat infection, improve healing time
  78. What is the difference between a third eyelid flap and a conjunctival flap?
    • conj flap provides blood vessels and fibroblasts to the cornea and is the txt of choice for a desmetocele
    • third eyelid flaps only protect only protect the eye from outside trauma and increase the chance of infection (BAD)
  79. How is a dermoid treated? What are the most commonly affected breeds?
    • Removed by superficial keratectomy
    • dachshunds, dalmations, dobies, GSDs, St. Bernards
  80. List 6 causes of a corneal lesion that does not retain fluorescein.
    • Desmetocele/ deep corneal ulcer
    • corneal sequestration
    • corneal dystrophy/ degeneration
    • pannus
    • eosinophilic keratitis
    • fibrous histiocytoma
Author
Mawad
ID
322650
Card Set
Ophtho1- Cornea
Description
vetmed ophtho1
Updated