Retina Flashcards
90% of cones are located in or outside of foveal region?
outside
what is definition of fovea? foveola?
fovea only has photoreceptors (highest density is at 4mm from center or 12 deg from fixation)
foveola only has cones.
describe attachment of cones vs rods to their respective bipolar cells?
cones attach 1 to 1 to their bipolar cells
many rods attach to 1 bipolar cell.
what is ILM
foot plates of muller cells–attached to posterior cortical gel of vitreous
what is ELM
zonular attachments between photoreceptors and muller cells.
central retinal artery divides in to how many branches?
4.
sometime there’s a cilioretinal artery
what are the 4 layers of retinal vessels?
- radial peripapillary capillary network (in RNFL)
- superficial vascular plexus (in ganglion layer)
3/4 deep capillary plexus (2 capillary beds on either side of the INL.
starting from which layer does the choroidal circulation supply the retina?
from outer plexiform layer outward
Functions of the RPE (7)
- absorbs light
- phagocytosis rod/cone outer segments
- participates in retinal and polyunsaturated fatty acid metabolism
- maintains subretinal space
- forms outer blood-ocular barrier
- Heals and forms scar tissue
- regenerates and recycles visual pigment
rods and cones shed their outer segment with daily circadian rhythm how?
rods shed discs in AM
cones shed them at dusk
–discs are phagocytosed by RPE cells
5 layers of Bruch’s membrane?
- basement membrane of RPE
- inner collagenous zone
- middle layer of elastic fibers
- outer collagenous zone
- basement membrane of endothelium of choriocapillaris
Choroidal blood enters through posterior ciliary arteries. The choroid has two layers . what are they?
- Outer larger caliber choroidal vessels (Haller layer)
2. Inner smaller caliber vessels (Sattler layer)
choroidal circulation
posterior ciliary arteries–>choriocapillaris–>venules–>vortex veins (4 or 5 per eye)–>superior and inferior ophthalmic veins
What is the leading cause of blindness in the developed world in people over 50
AMD
AMD risk factors (8)
Female sex, Family hx, HTN, HLD, CVD, highter waist to hip ratio in men, hyperopia, light colored iris
Race predilection of AMD
european americans highest, african americans lowest
Genetic associations with AMD?
lipid transport metabolism genes (APOE)
Collagen matrix genes (COL8A1)
all trans retinaldehyde photoreceptor clearaance genes ABCA4
and angiogenesis genes (VEGFA)
Genetic association is controversial as there are many modifyable risk factors.
size of small drusen vs intermediate vs large?
small <63microns, intermediate 63-124, large >124 (associated with risk of progression)
what are types of drusen shapes?
hard, soft, confluent.
soft and confluent are at more risk of progression to CNV and atrophy
appearance of drusen on FA?
small hard drusens can appear as window defects
large/confluent/soft drusens can have late staining
focal atrophy vs geographic atrophy of RPE?
geographic atrophy of RPE is when there’s continuous atrophy diameter >175 microns
GA generally are parafoveal until late stage when it will involve central vision.
AREDS study
vitamin C 500 mg, vit E 400 IU, beta carotene 15 mg, zinc oxide 80 mg, cupric oxide 2 mg.
Those with intermediate and advanced AMD had 25% less progression and 19% reduction in rate of vision loss in 5 years (>3 lines)
What is the 4 point grading scale for from AREDS study?
1 pt for 1 or more large drusen
1 pt for any pigment abnormalities
1 pt bilateral intermediate drusens
2 pts for any NV AMD
AREDS2 central question? outcomes?
tested whether replacing beta carotene with xanthophylls (lutein/ zeaxanthin) and adding omega 3 long chain polyunsaturated fatty acids would reduce AMD progression.
- lutein/zeaxanthin are similar to beta carotene and beta carotene had more risks of lung cancer in smokers
- LCPUFAs did not have significant effect in reducing progression of AMD.