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)