Topic 9: Retina Flashcards
Describe the retina
a thin, transparent membrane
externally bound by bruch’s membrane and internally by vitreous
extends from ora serrata to optic nerve head (firmly attached at the ora serrata & ON)
Subretinal space: potential space between RPE & NR. during retinal detachment, NR separates from RPE
Explain the arrangement & segregation of the retina
Total 10 layers, outer retinal pigmented layer (1) & inner neurosensory layer (9)
Explain pathway of light in the eye
light first hits ganglion cells and then nerve impulses get initiated (phototransduction) by photoreceptor cells.
Explain the structure of RPE
outermost, single layer of cuboidal/columnar cells, attached to bruch’s membrane
apical surface forms into microvilli that contains melanin
microvilli contains tip of outer segment from photoreceptor, & pigment
state the functions of RPE
absorbs stray light at periphery retina - to avoid light scattering
provide pathway for metabolites to receptors & removes waste from receptors
metabolises & stores vitamin A
microvilli gives mechanical stability to tips of receptors
phagocytosis of membrane discs (rods)
forms PART OF blood-retina barrier: protects outer third of retina (photoreceptors) from diffusion of large molecular toxic substances (from choriocapillaries)
describe structure of neurosensory retina
firmly attached to RPE @ora serrata & ONH margins, held together by vitreous elsewhere
contains 3 main types of neurons: photoreceptor cells, bipolar cells, ganglion cells (other: HC, AC)
9 layers: (outermost) PRL, ELM, ONL, OPL, INL, IPL, GCL, NFL, ILM
State and describe the regional variations of retina
(1) optic nerve head: no rods, no cones = blind spot
(2) macula: rods & cones, cones > rods
(3) fovea: rods & cones, cones»_space; rods
(4) foveola: only cones, no rods
(5) peripheral retina: rods & cones, rods > cones
describe/explain optic disc
ONH/optic papilla= neural rim + optic cup
pinkish area containing all nerve fibres = neural rim
slight central depression = optic cup
ONH lies 3mm nasal to macula
no photoreceptors
NOTE: lamina cribosa is where the optic nerve pierces the sclera
explain retinal blood supply
inner retina (layers until BPC): central retinal artery and vein
outer retina (PRL, RPE): choriocapillaris (branches of ciliary arteries)
briefly describe what is present in each layer (NR)
PRL: outer seg of rods & cones
ELM: separates outer-inner seg of PR from PR cell bodies
ONL: PR nuclei
OPL: synapses btwn PRC, BPC & HZC
INL: nuclei of BPC, HZC & AMC
IPL: synapses btwn BPC, AMC & GLC
GLC: GL nuclei
NFL: axons of GLC
ILM: separates retina from vitreous
describe functional differences between rods & cones
(R vs. C)
(1) peripheral vs central vision
(2) monochromatic vs colour vision
(3) scotopic vs photopic vision
describe structural differences between rods & cones
(R vs C)
(1) rod shaped vs cone shaped outer seg
(2) contains rhodopsin in membrane disc vs contains erythrolabe, cyanolabe, chlorolabe in membrane infoldings
(3) rod foot (spherule) vs cone foot (pedicle)
describe functional differences btwn peripheral and central vision
(P vs C)
(1) scotopic vs photopic vision
(2) monochromatic vs colour vision
(3) motion & flicker detection vs visual acuity function
(4) poor vs high resolution
(5) sensitive to low vs modertate-high light levels
describe structural differences between peripheral vs central vision
(P vs C)
(1) rod density higher vs cone density higher
(2) thinner (all layers are 1 cell layer thick) vs thicker (ONL & GCL take up 9-10 layers)
name the layers of retina in the foveolar region
RPE, PRL, ELM, ONL (only cone nucleus), OPL, ILM
