Ocular, Pt. 3 Flashcards
What is glaucoma? How does it affect the eye? How is it treated?
elevation of the intraocular pressure due to degenerative changes in the optic nerve and retinal ganglion cells
painful, blindness
enucleation
Healthy filtration angle:
angle wide and empty so aqueous humor can be drained
- CC = ciliary cleft
- TM = trabecular meshwork
What is the cause of glaucoma in veterinary medicine?
decreased outflow and absorption of aqueous humor
- abnormal angle
- angle closure
- obliteration of trabecular meshwork
- pupillary block
- masses that obstruct angle
What are the 3 most common complications of increased intraocular pressure in glaucoma?
- deformation of optic nerve axons
- degeneration and death of retinal ganglion cell layers with limited regeneration (permanent blindness) and atrophy of all retinal layers
- stagnation of aqueous flow causing impaired nutrition and waste removal
What are 6 common morphologic changes to the eye caused by glaucoma?
- buphthalmos common in younger animals due to increased elasticity
- pressure onto fibrous tunic
- thinning of sclera and choroid
- staphyloma (outpouch of sclera)
- angle recession
- lens luxation
Glaucoma, cat:
synechiae of lens to iris (posterior)
How are the cornea, lens, and retina affected by glaucoma?
CORNEA - exposure keratitis due to desiccation (eyelid unable to lubricate eye due to buphthalmos)
LENS - cataracts due to stagnant aqueous humor, luxation
RETINA - loss of axons and retinal ganglion cells (most superficial layers most susceptible)
How is the optic nerve affected by glaucoma?
cupping of optic disc due to direct pressure and axonal loss/collapse —> blindness
What are the 2 classifications of glaucoma?
- PRIMARY - goniodysgenesis, open-angle glaucoma
- SECONDARY - neovascular, pigmentary, pupillary block, lens luxation, neoplasia
What is the most common primary glaucoma? What is the cause? What animals are predisposed?
goniodysgenesis
dysplasia of ciliary cleft and or trabecular meshwork
DOGS - middle aged Spaniels, Huskies, Labradors, and Basset Hounds
How are the eyes affected by goniodysgenesis?
both eyes at risk —> bilateral, but not symmetric
- no previous or concurrent primary ocular disease
Normal filtration angle:
What is characteristic of goniodysgenesis histopathology?
solid iris-like sheet of uveal strom from the base of the iris to Descement’s membrane, which obliterates the filtration angle and decreases aqueous humor absorption
- no ciliary cleft or trabecular meshwork
What is a neovascular cause of secondary glaucoma?
pre-iridal fibrobascular membrane formation
- formatiom of fibroblasts and blood vessels effacing the ciliary cleft and trabecular meshwork
How do posterior synechiae and tumors cause secondary glaucoma?
pupillary block obliterates filtration angle (iris to lens)
direct obstruction of filtration angle and formation of pre-iridal fibrovascular membranes
What are the 3 most common causes of glaucoma in cats?
- chronic lymphoplasmacytic uveitis
- diffuse iris melanoma - filtration angle obliterated by neoplastic cells
- intraocular hemorrhage (hypertension)
Retina anatomy:
What is the most common cause of retinal atrophy?
glaucoma —> degeneration/loss of ganglion cells to full thickness
What are 2 causes of retinal detachment?
- exudative chorioretinintis or trauma where fluid/exudate in the subretinal space detaches the retia from choriod
- hypoxic injury (hypertension)
What is a common sequel to retinal detachment?
retinal pigmented epithelial hyperplasia (tombstoning)
- granular, fibrinous, proteinaceous exudate
- cells are usually cuboidal
What are the most common causes of hypertensive retinopathy in dogs and cats? What does it result in?
- DOGS: end-stage renal disease, pheochromocytomas
- CATS: end-stage renal disease, hyperthyroidism
hemorrhage, retinal detachment with fibrinoid change, arteriosclerosis, and medial hypertrophy in arterioles
What are common causes of ocular trauma? What does this commonly result in?
- contusive, penetrating, perforating trauma
- laceration with sharp structures
- cat claws, foreign bodies (risk of implanting infectious agents)
- glaucoma, neoplasia
hemorrhage within aqueous chamber —> hyphema
What lens change is common with ocular trauma? What is especially common in cats?
- phacoclastic uveitis/endophthalmos due to lens rupture
- luxation
intraocular sarcoma
In what animals is post-traumatic ocular sarcoma common? How does it present?
cats and rabbits
prior history of ocular disease within the last 7 years with lens capsule rupture
What is the origin of post-traumatic ocular sarcomas? How do they act? How is it mostly treated?
spindle cells - lens epithelium; can be osteosarcoma or chondrosarcoma
highly infiltrative and aggressive with rare metastasis
prophylactic enucleation to decreases chances of local recurrence due to orbit infiltration
Post-traumatic ocular sarcoma (PTOS):
What is entropion? Ectropion? What are common sequels?
inversion or inward turning of the eyelid margin
lower eyelid droops away from the eye and turns outwards
keratitis and conjunctivitis
What is chalazion? In what animal is it most common? What are they associated with?
yellow to white nodules at the eyelid margin due to an inflammatory responst to Meibomian gland secretions (lipogranulomas)
dogs —> adenomas
What eyelid tumors are most common in dogs and cats?
DOGS = Meibomian gland adenomas > melanocytomas > papillomas
CATS: SCC
What is the most common eyelid neoplasia of dogs? What are they commonly associated with?
Meibomian gland adenomas
chalazion (lipogranulomatous inflammation)
How do eyelid melanocytomas look grossly?
BEIGN —> pedunculated or papillary
- common in older dogs
In what animals are eyelid squamous cell carcinomas most common? How do they act? What are they associated with?
horses, ruminants, cats —> ulcers, crusts, hemorrhage
slow progression over months to years (actinic keratosis —> SCC insitu —> invasive SCC)
nonpigmented, thin-haired sited have low protection against UV light
What is the conjunctiva?
mucous membrane of squamous epithelium and goblet cells that line the inner eyelide
- has a normal flora, lamina propria, and lymphoid cells
What are 2 common causes of infectious conjunctivitis in kittens?
- feline herpesvirus-1: keratoconjunctivitis with latent infection where immunosuppression reactivates the virus, leading to lymphocytic inflammation
- chlamydia - C. felis, C. pecorum (small ruminants, koalas) —> serous to purulent discharge
What is the most common cause of infectious conjunctivitis in ruminants?
Moraxella spp. —> infectious keratoconjunctivitis (pinkeye) trasmitted by flies with increased incidence of Herefords (lack hooded eyelids that protect from UV light)
What conjunctiva neoplasia is common in horses?
SCC —> erosion on eyelid, friable proliferative salmon pink lesion on cunjunctiva
What conjunctiva neoplasia is common in dogs? How does it act?
melanocytic —> malignant with common recurrence
(melanocytic neoplasms are benign at other places)
What are the most common sources of orbital neoplasia? What is a common cause in cows? What does it lead to?
any orbital tissue —> osteo(sarco)ma, fibro(sarco)ma, lipo(sarco)ma, hemangio(sarco)ma
lymphoma from BLV infection
exopthalmos
What is the most common primary orbital neoplasm in dogs? What is its origin? What does it cause? What are 2 characteristics of histopathology?
meningioma —> arachnoid meningioepithelial cells of the optic nerve
exophthalmos and blindness
- conical thickening/growth
- chondroid, osseous, myxomatous metaplasia
What are the 3 common types of lacrimal gland neoplasia? How can it be differentiated from nictitating membrane prolapse?
- adenomas
- adenocarcinomas
- SCC
neoplasia is most common in older animals and prolapse is common in younger animals
