0812 - Diseases of the Eye Flashcards
Explain the aetiology of Cataracts
Basically an opacity of the lens. 3 types - Nuclear, cortical, capsular.
Nuclear - hardening at the core of the lens that expands out through the layers. Associated with ‘brunessence’ of the lens, causing reduce transmittance of light, increased scatter and increased flourescence. Things appear red and blurry. Associated with aging.
Cortical - Changes to lens proteins that start at margin of lense and spread through the more superficial layers to the optic axis.
Capsular - Modification of the lens capsule, anteriorly or posteriorly. Often occurs subsequent to eye surgery.
Explain the aetiology of Glaucoma
Spectrum of disorders that affect the retina leading to progressive loss of ganglion cells and their axons (optic nerve) as they pass through lamina cribrosa. Axons are compressed, leading to GC death.
2 types - open and closed angle. Closed angle, pressure pushes iris forward, closing off trabecular meshwork. Open - Trabecular meshwork gets clogged by proteins etc.
Explain the aetiology of AMD
Lesion in central visual field, cf peripheral due to degeneration of the photoreceptors in the macular region and death of retinal pigment epithelial cells. 2 types - dry and wet - Dry (ARMD) - Drusen (white spots) appear prior to degeneration and slow and steady vision loss. Wet - there is neovascularisation and bleeding - vision loss is sudden after a bleed.
What is the mechanism of GC death in glaucoma?
Decline in the retrograde supply of neurotrophins to GC from their axon terminals
Release of excitotoxic amino acids by damaged GC
Apoptosis of GC.
What is the prevalence of Cataract in Aus?
Most prevalent eye disease in Australia (31% over 55s). But easily treated so not a major problem. Oestrogen is protective, so mostly hits postmenopausal women. ATSI people can’t afford the surgery and public doesn’t normally cover it, also poor health literacy etc.
What is the prevalence of AMD in Aus?
13.5% over 55s (650,000 cases), early stages in 25% of over 60s, with 1.9% of population having end-stage disease and legally blind.
WHat is the prevalence of Glaucoma in Aus?
Age related incidence. Cause of 8% of visual impairment.
Define legal blindness
Vision that cannot be corrected beyond 6/60
Explain visual impairment
Any diagnosed condition of the eye or visual system that cannot be corrected to within normal limits.
Why is glaucoma often undetected?
Vision loss is peripheral at first. Central vision still good, so you don’t realise you’re losing vision until they have significant vision loss.
Why does AMD have a major impact on a sufferer’s quality of life?
Loss of central vision.
