L26 - Nervous Layer Flashcards
(38 cards)
What are the three layers of the eyeball?
Fibrous layer (sclera, cornea), vascular layer (iris, ciliary body, choroid), nervous layer (pigment layer, neural layer/retina).
What is the Latin word for retina and what does it mean?
Rete; it means “net”.
Where does the retina extend from and to?
From the optic disc to the ora serrata.
What is the surface area of the retina?
About 1,094 mm².
Where is the retina thickest and thinnest?
Thickest near the optic disc (560 µm), thinnest at the foveal floor (100 µm), thinner towards the periphery (180 µm at equator, 100 µm at ora serrata).
How far is the fovea from the optic disc edge?
11.8° or 3.4 mm temporal to the optic disc edge.
What is the size of the optic nerve head?
1.86 × 1.75 mm.
What is the cross diameter of the macula?
3 mm of intense pigmentation, surrounded by a 1-mm-wide zone of less pigmentation.
How much retinal distance does one degree of visual angle correspond to?
288 μm on the retina.
How does fundus color vary by pigmentation?
Lightly pigmented individuals have a blonde fundus (sub-retinal elements visible); darkly pigmented individuals have a more pigmented fundus (sub-retinal elements not seen).
What are the main visible landmarks of the retina?
Retinal blood vessels, peripheral retina and ora serrata, optic disc, area centralis (macula) with fovea and foveola.
What arteries supply the retina?
Central retinal artery and posterior ciliary artery.
What veins drain the retina?
Arcade veins → central retinal vein; choroidal veins → vortex veins.
What are the three retinal zones?
Zone 1 (near periphery), Zone 2 (mid periphery), Zone 3 (far periphery).
What is the ora serrata?
Transition zone between retina and pars plana; underlying the vitreous base; associated with increased risk of retinal detachment.
What is the width and location of the ora serrata?
Width: 2.1 mm temporally, 0.7 mm nasally; 6 mm nasally and 7 mm temporally from the limbus; 25 mm nasally from the optic disc.
What is the optic disc?
Circular or slightly oval area (about 1.5 mm), contains a depression known as the physiological cup.
What are the dimensions of the optic disc?
Vertical diameter: 1.86 mm; horizontal diameter: 1.75 mm; 3.4 mm from the macula.
What is the normal cup-to-disc ratio (CDR)?
0.3 to 0.4.
What is the ISNT rule?
Neuroretinal rim thickness order: Inferior > Superior > Nasal > Temporal.
What is the area centralis (macula)?
Located at the posterior pole, temporal to disc, elliptical, 5.5 mm diameter, corresponds to 15° of visual field.
What are the subdivisions of the area centralis?
Umbo (0.15 mm), FAZ (0.5 mm), fovea (1.5 mm), parafoveal area (2.5 mm), perifoveal area (5.5 mm), foveola (0.35 mm).
What is the macula lutea?
Oval yellow zone, 3 mm diameter, yellow color due to xanthophyll, histologically more than 1 layer of ganglion cells (6-8 layers).
What is the fovea?
Centre of area centralis, 4 mm temporal to disc, 0.8 mm below horizontal meridian, 1.85 mm diameter, 0.25 mm thick, corresponds to 5° of visual field.
