Retina Flashcards
General retina information
What is the retina?
Layer
Location
Appearance
- Innermost layer of the eye
- Neural layer
- Located between choroid and vitreous
- Transparent but appears reddish due to choroid and retinal pigment epithelium
General retina information
What is the ora serrata?
Anterior limit of the neural retina
General retina information
Where is the retina thickest?
The retina is thickest in the macular region and thins out as the retina goes further out in the periphery
General retina information
What is the function of the retina?
The retina receives light and transmits neural impulses to the brain for interpretation
Photoreceptors transform photons into neural signals via phototransduction and sends the signal to the optic nerve and then the brain
Zones in the retina
What are the retinal zones?
Try to picture them in your head too!
- Posterior pole (central retina)
- Peripheral retina
- Ora serrata
Peripheral retina consists of mid-periphery, equator, and far periphery
Vitreous base straddles the ora serrata and far periphery
Posterior pole
What is the posterior pole?
Identify:
1) Retinal portion
2) Function
3) Vision type - photoreceptors
- Central retina - takes up a small part of the total retina
- Designed for visual acuity and detecting detail and color
- Critical for good photopic vision due to majority of cones being here
Posterior pole
What key structures can be found in the posterior pole?
- Optic nerve
- Macula
- Vascular arcades
- Arcuate retinal nerve fibers
Where is the temporal optic disc located in relation to the fovea?
3.4 mm away from the fovea
Peripheral retina
What is the peripheral retina?
Identify:
1) Retinal portion
2) Function
3) Vision type - photoreceptors
- Makes up most of the retina - includes equator, mid-periphery, far periphery
- Detects gross form and motion - objects appear less detailed and clear
- Critical good scotopic vision - majority of rods found here
Peripheral retina
What key structures can be found in the peripheral retina?
- Short ciliary nerves
- Long ciliary nerves
- Short ciliary arteries
- Long ciliary arteries
- Vortex veins
Peripheral retina
What are short ciliary nerves?
Describe:
1) Amount of short ciliary nerves
2) Location
3) Pathway
4) Meridian and division
- 8-10 per eye
- 2, 4, 8, 10 o’clock (in between notches)
- Ciliary ganglion (origin) -> nasociliary branch (V1) of CN V (sensory); CN III and CN VIII (sympathetic and parasympathetic) -> sphincter of iris -> ciliary body -> cornea
Represents the vertical meridian of the retinas
Divides peripheral retina into the nasal and temporal half
Peripheral retina
What are long ciliary nerves?
Describe:
1) Amount of long ciliary nerves
2) Location
3) Pathway
4) Meridian and division
- 2 per eye
- 3 and 9 o’clock
- Nasociliary branch (V1) of CN 5 (origin) -> conjunctiva -> cornea -> dilator muscle of iris -> ciliary body
Represents the horizontal meridian (180 axis)
Divides retina into superior and inferior half
Peripheral retina
What are the short ciliary arteries?
Describe:
1) Origin
2) Amount
3) Interaction
- Arises from ophthalmic artery
- Divides into 10-20 branches
- Entwine with short ciliary nerves
Peripheral retina
What are the long ciliary arteries?
Describe:
1) Origin
2) Amount
3) Interaction
- Arises from opthalmic artery
- Divides into 2 branches
- Entwine with long ciliary nerves
Peripheral retina
What are vortex veins?
Describe:
1) Composition
2) Function
3) Amount
4) Location
- Composed of tributary veins that come together at ampulla
- Drains vasculature of choroid
- About 4-8 per eye
- Oblique regions of the retina (IN, IT, SN, ST)
Peripheral retina
Where is the equator located?
- 2 DD posterior to the tributary veins
- Right at the posterior edge of the ampulla of a vortex vein
DD is disc diameter
Kind of like the more central edge or border of the ampulla
What is the vitreous base?
Identify:
1) Description
2) Function
3) Anterior border
4) Posterior border
- Site of strongest attachment of the vitreous to the retina
- Straddles ora serrata
- Extends 1.5 mm into pars plana anteriorly
- Extends 2-3 mm into the ora serrata posteriorly
Posterior border is closer to 3 mm when nasal and closer to 2 mm when temporal
How is the retina measured?
Identify:
1) Typical unit/measurement definition
2) Conversions for DD, microns, mm, and degrees
- Disc diameter: optic disc size equivalent
- 1 DD = 1,500 mircons
- 100 microns = 0.1 mm
- 1 degree = 300 microns
Retinal testing
Fluorescein Angiography
Identify:
1) Purpose
2) Application
3) General description of the image
- Highlights the optic nerve and retinal+choroidal circulation
- Useful for detection of subclinical retinal/choroidal/optic nerve changes secondary to vascular conditions - diagnose retinal, choroidal, optic nerve head vascular disorders
- Vasculature should be highlighted white with a grey/darker retinal background
Aids in treatment decisions and guides retinal laser therapy
Image will show leakage of dye if there is damage
Retinal testing
Optical Coherence Tomography (OCT)
Identify:
1) Purpose
2) Application
3) General description of image
- Visualizes all layers of the retina
- Instrumental in diagnosing various pathologies (ex: macular edema, vitreomacular traction)
- Grey scale image that’s layered like sand art with a small blip in the center
Retinal testing
Optical Coherence Tomography Angiography (OCT-A)
Identify:
1) Purpose
2) Application
3) General description of image
- Visualize vessels of the retina and choroid non-invasively and is based on active blood flow
- Provides good view of blood flow structure - not really for leakage
- Similar grey-scale image to FA (grey retina/background with white vasculature)
Retinal testing
Fundus Autofluorescence (FAF)
Identify:
1) Purpose
2) Application
3) General description of image
4) AF result interpretation - increased AF
5) AF result interpretation - decreased AF
- Reflects lipofuscin at the RPE layer/level
- Useful for detecting issues with RPE
- Image is “opposite” of FA - vasculature appears dark/black with a lighter grey retinal background
- Increased AF means excess lipofuscin accumulation
- Decreased AF means loss or death of RPE cells
Lipofuscin is formed when RPE ingests shedded outer segments of photoreceptors via phagocytosis - it’s a normal wear and tear pigment
Retinal testing
B-Scan Ocular Ultrasound
Identify:
1) Mechanism
2) Purpose
3) Application
4) General description of image
- High frequency sound waves are transmitted from a probe to the eye using transmission gel
- Helps in localizing and defining shape and extension of posterior segment pathology
- Useful for detecting retinal detachments or other posterior segment pathology
- Image shows darker area as vitreous and optic nerve and the lighter area as retina
Literally ultrasound for the eye
Retinal layers
What are the main layers of the retina in order from anterior to posterior (inner to outer)?
Anterior/inner - closer to vitreous; Posterior/outer - closer to choroid
- Internal limiting membrane (ILM)
- Retinal nerve fiber layer (NFL)
- Ganglion cell layer (GCL)
- Inner plexiform layer (IPL)
- Inner nuclear layer (INL)
- Outer plexiform layer (OPL)
- Outer nuclear layer (ONL)
- External limiting membrane (ELM)
- Photoreceptor layer
- Retinal pigment epithelium (RPE)
Mneomonic: INGIIOOEPR (“in geeoo EPR)
Retinal layers
What retinal layers make up the inner layers?
(between what layers is the distinction between inner and outer made)
- Internal limiting membrane
- Retinal nerve fiber layer
- Ganglion cell layer
- Inner plexiform layer
- Inner nuclear layer
Distinction is between INL and OPL
Retinal layers
What retinal layers make up the outer layers?
(between what layers is the distinction between inner and outer made)
- Outer plexiform layer
- Outer nuclear layer
- External limiting membrane
- Photoreceptor layer
- Retinal pigment epithelium
Distinction is between INL and OPL
Retinal layers
What layer is contained in the OPL?
Henle fiber layer
Retinal layers
What three components make up the photoreceptor layer?
- Myoid zone
- Ellipsoid zone
- Outer segments of photoreceptors
Retinal layers
What is the interdigitation zone (IDZ)?
Junction that sits between the photoreceptor layer and RPE
Retinal layers - RPE
Retinal pigment epithelium (RPE)
Describe:
1) Location
2) Composition
3) Unique traits
- Outermost layer (deepest) - lies between Bruch’s membrane and the photoreceptor layer
- Single cell thick - composed of pigmented hexagonal cells which appear more cube-like when viewed as a cross section
- Highly metabolic and appears darker due to melanin (contained in melanosomes and lipofuscin)
Melanin is densest in the RPE cells at the macula followed by the equator
Retinal layers - RPE
RPE Melanin
Identify:
1) Densest melanin in RPE
2) Effect of age on melanin
3) Pigment distribution
- Melanin in RPE is densest at the macula followed by the equator
- Increasing age results in more melanin/pigment due to increased pigmented bodies, lipofuscin, and breakdown of phagocytic material
- Pigment distribution is unequal - gives more granular appearance (primarily seen/is more apparent at the macula)
Retinal layers - RPE
What types of junctions are found in the RPE?
Identify:
1) Junction types
2) Function
- Zonulae occludens (tight) - forms BBB, prevents passage of material in between cells but can sometimes allow material through
- Zonulae adherens (anchoring) - forms BBB, prevents cells from sliding out of position and can sometimes allow material to pass through
- Desmosomes (anchoring) - provides structural support between RPE cells and can sometimes allow material to pass through
- Hemidesmosomes (anchoring) - provides structural support between RPE cell and basement membrane (Bruch’s) by connecting intermediate filaments with strong adhesion
- Gap junctions - permit electrical and chemical communication between RPE cells
Retinal layers - RPE
RPE Physical Appearance
Identify:
1) Physical appearance at macula
2) Physical appearance in periphery
3) Density pattern
- RPE cells are longer and narrower at the macula
- RPE cells become wider and flatter further out in the periphery and ora serrata
- RPE cells are most dense at the macula (fovea) and decrease in density further out in the periphery
Mnemonic: Macula is a model - long and narrow shape
Retinal layers - RPE
RPE Cell - Basal
(try to visualize diagram)
Identify:
1) Location
2) Organelle present
3) Function
- Closest component to Bruch’s membrane
- Majority of mitochondria found here
- Strong adhesion to innermost layer of Bruch’s membrane (basement membrane of RPE)
Retinal layers - RPE
Why is there such strong adhesion to Bruch’s membrane at the basal component?
- Basal aspect contains infoldings of plasma membranes which allows tight adherence
- Innermost layer of Bruch’s membrane is composed of extracellular matrix proteins that includes large adhesive glycoproteins that bind strongly to the basal surface
- Hemidesmosomes in the basal aspect allow stable adhesion to Bruch’s
Bruch’s membrane separates RPE from choroicapillaries
Retinal layers - RPE
RPE Cell - Central
(try to visualize diagram)
Identify:
1) Location
2) Organelle present
- Between basal component and apical component
- Large oval nucleus
Retinal layers - RPE
RPE Cell - Apical
(try to visualize diagram)
Identify:
1) Location
2) Organelle present
3) Function
- Closest to photoreceptors
- Microvilli - extend to outer segment tips of photoreceptors
- Composed of melanin granules which help to absorb scattered light and stabilize free radicals
Retinal layers- RPE
What junctions are present at the RPE - Photoreceptor interface?
- No intracellular junction connect the RPE to the photoreceptors - results in potential space in between the RPE and photoreceptors (sub-retinal space)
Retinal layers- RPE
How does the RPE-photoreceptor interface stay attached?
- IOP
- Osmotic pressure
- Vitreous
- Apical microvilli of the RPE
- Interphotoreceptor matrix (IPM) is composed of sticky proteins and glycosaminoglycans
Retinal layers - RPE
What are some functions of the interphotoreceptor matrix (IPM)?
- Sticky proteins and glycosaminoglycans found in the extracellular space between RPE and photoreceptors - helps with RPE-photoreceptor attachment
- Matrix surrounds outer segments of photoreceptors - provides support, allows exchange of nutrients, provides optimal orientation to capture light, and helps with transfer of pigment and nutrients
Retinal layers - RPE
Where is the RPE-photoreceptor interface absent?
Identify location and clinical significance
Absent along the peripapillary ring around the optic disc as well as the ora serrata - retina is strongly attached at these areas and will never detach
Retinal detachment
Describe:
1) What condition is
2) Clinical consequence
- Separation between the RPE and photoreceptor layer
- Separation prevents photoreceptors from getting nutrients from the choroid and leads to photoreceptor death
Retinal layers - RPE
What are the functions of the RPE?
- Absorption of scattered light - improves optical quality and reduces photo-oxidative stress on the retina
- Control fluid, nutrient, and waste product transport to and from the sub-retinal space and photoreceptor layer
- Visual pigment regeneration and synthesis
- Essential for the visual cycle
- Synthesis of signaling molecules (PDGF, PEDF, VEGF, TGF)
- Phagocytosis of photoreceptor waste
- Involved in regeneration and repair if there is retinal damage
- Stores vitamin A
- Synthesizes IPM
- Acts as the outer-blood retina barrier (tight junctions in RPE)
Retinal layers - RPE
What are the signaling molecules synthesized by the RPE and their functions?
Identify:
1) Signaling molecule
2) Function
- PDGF - controls cell growth and healing
- PEDF - neuroprotectant
- VEGF - stimulates normal vascular growth and neovascularization
- TGF - controls inflammation
Mnemonic: PDGF - growth and flourish
Mnemonic: PEDF - defense
Mnemonic: VEGF - veggies need new (neo) water (vascular)
Mnemonic: