Ophthamology: Chronic Visual Loss Flashcards
What is normal Intraocular pressure (IOP)?
8-21 mm Hg
Component of the visual field that is most commonly disrupted in glaucoma.
Arcuate (peripheral) visual field
What are two general mechanisms that lead to damage of the neurons that make up CN II?
- Ischemia to nerve fibers at the optic nerve head
2. Mechanical pressure on the nerves, usually from increased IOP, that prevents transmission of signals down the axons
What is a confrontational visual field test?
Simple preliminary test that measures the peripheral field of each eye individually. Used sometimes in in testing for chronic glaucoma because glaucoma affects the peripheral visual field in extreme vision loss.
How can cataracts lead to glaucoma?
The crystallization of the lens can push on the iris and close off the angle to the canal of schlemm and block outflow of the aqueous humor.
What are the 3 anatomical regions of the lens?
- Nuclear: inner most layer that contains the oldest lens cells
- Cortical: middle layer that contains growing lens cells
- Subcapsular: outer epithelial layer that produces new cortical cells that will eventually migrate inward
Describe “second sight”.
Patients that are farsighted will start to develop cataracts in the nuclear region (nuclear sclerosis) and caused an induced myopia or nearsightedness. They think that their vision is improving but in reality they are progressing to vision loss.
What is the leading cause of vision loss in the U.S.?
Dry macular degeneration
What is a common visual defect in patients with macular degeneration?
Metamorphopsia - distorting the center of the visual field.
What is Drusen?
Hyaline nodules found in Bruch’s Membrane (separates the Retinal Pigment Epithelium (RPE) from the inner choroidal vessels). They are seen in age-related macular degeneration (Dry). Appears as bright yellow spots on retina.
What is the cause of wet macular degeneration?
Neovascularization of leaky blood vessels in the macula. Appears as red spots in the retina and can often lead to sudden visual loss.
What is an Amsler Grid Test?
Series of black grid lines on white paper. The patient is asked to note any visual irregularities on the page. If they don’t see straight grid lines, suspect macular degeneration.
