Ocular Flashcards
Define Aqueous flare
Aqueous humor turbidity caused by inflammatory cells and/or protein in the anterior chamber. Pathognomonic for breakdown of the blood-eye barrier.
Define PIFM
Preiridal fibrovascular membranes- proliferation of vessels on anterior face of the iris. Can overgrow and cause peripheral anterior synechiae.
Define synechiae (anterior/posterior)
Anterior synechiae- adhesion of the iris to the cornea.
Posterior synechiae- adhesion of the iris to the lens, causes iris bombe.
Caused by increase in adhesiveness due to fibrin and/or PIFM.
Define iris bombe
Pupillary block causing distended iris into anterior chamber.
Define keratitis
Inflammation of the cornea.
Define uvea
Vascular tunic of the eye including iris, ciliary body and choroid.
Describe uveitis
Inflammation of the vascular system of the eye (the uvea) causing migration of neutrophils and macrophages out of vessels and into eye, proliferation of lymphocytes and plasma cells that form perivascular cuffs/lymphoid follicles, and release of inflammatory mediators in the aqueous humor.
Define cyclitis
Inflammation of the ciliary body
Define cataract
Any opacification of the lens. Can be caused by chronic uveitis.
Characterize glaucoma
Optic neuropathy characterized by retinal ganglion death, optic nerve cupping, optic nerve axonal loss, and vision loss. Caused by increase in intraocular pressure.
Define Goniodysgenesis
Abnormal development of the iridocorneal/filtration angle where a thick bank of uveal tissue blocks normal aqueous flow and predisposes animals to glaucoma.
Define Peripheral anterior synechiae
Adhesion of the iris to the iridocorneal angle/overgrowth of PIFM covering angle, results in secondary glaucoma.
Define Persistent pupillary membranes
Remnant iridal tissue connecting iris to lens or cornea, may cause focal corneal opacity or focal cataract, usually clinically insignificant.
Define Hypopyon
Settled neutrophils and macrophages that migrate into the anterior chamber, contributes to aqueous flare.
Define Hyphema
Blood in the anterior chamber due to spontaneous hemorrhage of the fragile new vessels of preiridal fibrovascular membranes on the anterior iris.
What is the role of the epithelium and the endothelium in maintaining optical clarity in the cornea?
Epithelium is hydrophobic barrier, endothelium pumps water out to dehydrate
What are the three characteristics that make the cornea transparent?
Dehydration
Avascularity
Regular array of collagen lamellae and keratocytes
- What are the most common causes of corneal opacification? Explain 3 of them.
Foreign body, scarring (white, indistinct borders), neoplasm or inflammatory infiltrate (yellow/creamy, indistinct borders), deposits (white, crystalline, sharp borders), pigment (brown/black, sharp borders), vascularization, edema (blue haze, indistinct borders)
- Name 3 causes of corneal edema and explain their pathogenesis.
Epithelial ulcers- loss of hydrophobic barrier, movement of water into stroma
Stromal vascularization- leaky blood vessels
Endothelial defects- diffuse deep corneal edema due to loss of pump function because of: endothelialitis (CAV-1, Bovine herpesvirus), degeneration, trauma, glaucoma, uveitis
- Explain the pathogenesis and lesions associated with keratoconjunctivitis sicca in dogs, in acute and chronic cases. Name two common breeds affected.
Dog breeds commonly affected: King Charles Cavalier Spaniels, Cocker Spaniels, Lhasa Apsos, Shih Tzus, Bulldogs, Pugs, Boston Terriers, Pekingese
Defect in aqueous component of tear film from lacrimal gland/3rd eyelid gland
Causes: autoimmune, infectious, removal of 3rd eyelid, neurological disease
Acute: corneal ulcerations, mucopurulent ocular discharge
Chronic: corneal epithelium undergoes epidermalization- thickening, pigmentation, neovascularization, inflammation, ridge formation
- What is the best place to look histologically to find fungus in mycotic keratitis of horses?
Descemet’s membrane and deep corneal stroma
- What is the causative agent of bovine pink eye? Which are the physical factors related to the spread of disease in bovine pink eye?
Moraxella bovis
Corneal irritation by UV light, flies, or long grasses
- Name 3 morphologic/histopathologic hallmarks of equine recurrent uveitis?
Lymphocytic inflammation of the uvea
Eosinophilic membrane coating ciliary processes
Intracytoplasmic inclusions in non-pigmented ciliary body
- What is the definitive cause of Equine recurrent uveitis?
Likely incited by Leptospira infection followed by immune-mediated recrudescence
Multi-factorial and not fully understood
- What are the most common causative agents of systemic mycosis that also affect the eye? Which most commonly affects dogs and cats? What do they all cause?
-Blastomycosis (most common in dogs)
-Cryptococcosis (most common in cats)
-Coccidiosis (SW US only)
-Histoplasmosis (most common in dogs and cats)
All cause pyogranulomatous chorioretinitis
- What is the definitive cause of lymphoplasmacytic uveitis in cats? What is this disease characterized by?
Idiopathic
Bilateral anterior uveitis
Iridal nodules = lymphoid follicles
- Name the consequences of uveitis that might be responsible for the development of glaucoma?
Lymphoid follicle proliferation can obliterate the iridocorneal angle, block aqueous flow, and lead to secondary glaucoma
- Retinal detachment occurs when there is a separation between which layers?
Neurosensory retina and the retinal pigment epithelium
- Name several pathologic processes which might be responsible for retinal detachment.
Serous detachment – breakdown of blood-eye barrier and exudation from choroid vessels into subretinal space
Traction – vitreal traction bands pull on retina to detach
Rhegmatogenous - vitreous dissects through a retinal tear into the subretinal space
- What are the most common ocular lesions observed in animals with systemic hypertension?
Hypertensive vasculopathy/chorioretinopathy, serous retinal detachment
- What are the most common causes of secondary glaucoma?
-Uveitis: peripheral anterior synechiae, posterior synechiae iris bombe, inflammatory cells/fibrin clogs trabecular meshwork blocking aqueous outflow
-Trauma/Hyphema: blood cells clog trabecular meshwork
-Lens luxation: trauma or spontaneous lens stuck in anterior chamber blocks outflow of aqueous
-Neoplasia: obliteration or obstruction of iridocorneal angle with neoplastic cells
- How are the following abnormalities related to the potential development of glaucoma? A. Peripheral anterior synechiae
PIFM grows over iridocorneal angle to block access to trabeular meshwork
- How are the following abnormalities related to the potential development of glaucoma? B. Hypopyon/hyphema
Neutrophils, macrophages, and/or RBCs block trabecular meshwork
- How are the following abnormalities related to the potential development of glaucoma? C. Goniodysgenesis
Congenital malformation of iridocorneal angle results in incomplete rarefaction of the pectinate ligaments between the iris root and limbus which cover the entry to the iridocorneal angle and block aqueous outflow
- How are the following abnormalities related to the potential development of glaucoma? D. Neoplasia
Neoplastic cells can directly obliterate the iridocorneal angle or sloughed neoplastic cells and/or RBCs can clog the angle and block outflow
- Characterize the morphologic hallmarks of goniodysgenesis.
Presence of a thick band of uveal tissue extending from the iris base to the terminus of Descemet’s membrane of the cornea and covering the iridocorneal angle
- Describe the optic nerve and retinal lesions associated with glaucoma
Retinal atrophy, cupping of optic nerve head, end stage: buphthalmia (eye enlargement), lens luxation, phthisis bulbi
- What are the most common primary ocular tumors in the dog and cat?
Dog: Melanocytoma (80%), Malignant melanoma (20%), anterior uvea
Cat: Diffuse Iris Melanoma (FDIM)
- Distinguish between feline diffuse iris melanoma and anterior uveal melanocytic tumors in dogs. Characterize the likely metastatic behavior of each. What is possible secondary outcome of both tumor types?
FDIM: grossly dark freckles in iris that coalesce over time. Metastasis occasional.
Melanocytic dog tumors: Single pigmented mass in anterior eye that grows and can take over the globe. Metastasis rare.
Both can cause secondary glaucoma.
- What is the cell thought to be responsible for feline post-traumatic sarcoma?
Lens epithelial cells released during lens capsule rupture
- Describe the common biologic behavior of conjunctival and corneal squamous cell carcinoma in the horse and ox. Is metastasis likely?
Horse: Arise from third eyelid margin
Cattle: Arise from conjunctiva at limbus, less often eyelids or cornea
Both associated with viral infection and UV light and can metastasize late.
- Name several tumors that commonly metastasize to the eye.
Lymphoma
Histiocytic sarcoma
Melanoma
Hemangiosarcoma
Mammary adenocarcinoma
