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Flashcards in Reviewing retina Deck (44):
1

Name 10 layers of retina 

From outwards to inwards

Chroid 

  1. Pigment epithelium
  2. Rods and cones
  3. Outer limiting membrane
  4. Outer nuclear layer
  5. Outer plexiform (molecular) layer
  6. Inner nuclear layer
  7. Inner plexiform (molecular) layer
  8. Ganglion cell layer
  9. Nerve fibre layer
  10. Internal limiting membrane 

Vitreous 

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Retinal pigment epithelium (RPE)

 

  1. Extension from where to where?
  2. Relationship to choroid?

Retinal pigment epithelium (RPE)

  • Single layer of cells which extend from the optic nerve to the ora serrata
  • The base of each cell rests on a basement membrane which forms part of the Bruch’s membrane of the choroid 

 

 

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The neural retina

  1. Photoreceptors ? 2 types?
  2. First order and second order neurons?

The neural retina

  1. Photoreceptors Rods & cones

 

  1. The bipolar cells form the 1st order neurones

The ganglion cells form the 2ndorder neurones & become myelinated after passing through the lamina cribrosa

NB: their axons form the optic nerve 

 

 

 

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Retinal blood supply

Sources of blood supply?

2 sources of blood supply to the retina:

  1. central retinal artery 
  2. choroidal blood vessels 

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  1. Greatest source of retinal blood supply? Supply what part of retina?
  2. What is the remaining? Supply what part of retina

 

  1. The choroid receives the greatest blood flow (65-85%) and is vital for the maintenance of the outer retina (particularly the photoreceptors) 
  2. The remaining 20-30% flows to the retina through the central retinal artery from the optic nerve head to nourish the inner retinal layers. 

 

 

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CENTRAL RETINAL ARTERY 

  1. How many branches in retina?
  2. Where do they emerge from? Describe their course?

 

  1. The central retinal artery has 4 main branches in the human retina
  2. The vessels emerge from the optic nerve head & run in a radial fashion, curving towards the fovea 

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Label the branches 

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CHOROID 

  1. What is it?
  2. Extension?
  3. Thickest and thinnest where?

  1. Thin, soft brown coat on the inner surface of sclera
    Extremely vascular
  2. Extends from the optic nerve to the ciliary body
  3. Thickest posteriorly (0.2mm) & gradually thins anteriorly (0.1mm) 

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CHOROID 

  1. Name of space between sclera and choroid
  2. Structure run across this space?
  3. What other structure it contains?

 

  1. There is a perichoroidalspace which sits between the sclera and choroid
  2. Suprachoroid lamina runs across this space (pigmented connective tissue)
  3. Short post. ciliary arteries & nerves are also here 

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CHOROID 

How many layers? Name?

 

  1. Vessel ( External)
  2. Capillary ( Middle)
  3. Brunch's membrane ( Internal) 

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CHOROIDAL LAYERS 

 Describe Vessel layer: Tissue? Vessels?

  • Loose connective tissue
  • Medium & large blood vessels embedded

 

 

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CHOROIDAL LAYERS 

Capillary layer?

Function? Density?

 

•Network of capillaries

•Arteries & veins from vessel layer are responsible for feeding & drainage of these capillaries

•Density of capillaries is greatest at the macula

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CHOROIDAL LAYERS 

Bruch’s membrane

Name components?

 5 components

  • Basement membrane of the endothelium of the capillaries of the capillary layer
  • Outer collagen fibre layer
  • Elastic fibre layer
  • Inner collagen fibre layer
  • Basement membrane of the pigment epithelium of the retina 

 

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CHOROID 

Primary function?

  • nourish the outer layers of the retina by blood supply → nutrition to the retina 

 

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Retinal vessels

Any variation in appearance? What's common?

  • vary in appearance between people
  • common variation is that in some people small arteries run from the disc to the macula = cilioretinal vessels 

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FUNDUS COLOUR 

  1. What factors detemine colour? 
  2. Relationship with other structure?

 

  1. how much MELANIN is in the Retinal pigment epithelium 
    Melanocytes in the choroid
    Haemoglobin in the retinal & choroidal vasculature
  2. Relationship between fundus colour and the person’s:
    Skin colour
    Hair colour
    Iris colour 

 

 

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FUNDUS COLOUR 

Variation between races?

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Retinal landmarks

Macula lutea

  1. Position in relation to disc and retina?
  2. Colour? 
  3. Name of depression?

 

Macula lutea

  1. At the centre of the posterior part of the retina
    Always temporal to the disc
  2. Slightly darker in colour to the surrounding retina
  3. Has a central depression = Fovea 

 

 

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MACULA 

  1. Distinguising Characteristics?
  2. Structure allowing light fall directly on photopigment?

  1. The macula contains only cones.
  • The density of the cones is greater than for any other region of the retina.

    2.The neural elements of the inner retina are pushed aside to allow light to fall directly on the photopigment-containing outer segments of cones ⇒ foveal pit. 

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The fovea
1. Vascular network? Metabolic nourishment?

2. Significance of this adaptation?

  1. Avascular 
    Metabolic nourishment from the choroid rather than directly from the blood vessels. 
     
  2. Prevents the scattering of light by retinal vessels, maximising the visual resolution provided by the fovea. 

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Looking at the retina & choroid
Ways to view retina?

  • Ophthalmoscopy
    Direct
    Indirect 
  • Photography
    Colour
    Red free
  • AngiographyFundus Fluorescein (FFA)
  • Optical Coherence Tomography (OCT) 

 

 

 

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Fundus Fluorescein Angiograms (FFA)
1. How to do it?

2. What is it? 

  1. Fluorescein (orange water-soluble dye) injected intravenously circulates in the blood

    2 types used when performing FFA

    Ensures that blue light enters the eye & only yellow-green light enters the camera 

  2. Photographing the passage of the dye through the retinal & choroidal circulations 

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FFA Filters

Name 2 filters?

  1. Blue excitation filter
    White light from the camera passes through this 
    Blue light emerges & enters the eye
    Excites the fluorescein molecules in retina
     
  2. Yellow-green barrier filter
    Blocks reflected blue light from the eye
    Allows only yellow-green light to pass through 

 

 

 

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FFA technique?

Patient sits on front of the camera

Fluorescein injected intravenously

Images taken at ~ 1 sec intervals, 5-25 seconds after the injection

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FFA –adverse effects ?

 

  • Skin & urine discolouration
  • Mild
    Nausea, vomiting
    Flushed skin
    Itching, hives
    Sneezing
     
  • Serious (rare)
    Laryngeal oedema
    Bronchospasm
    Anaphylaxis
    Syncope (lapse in consciousness) 

 

 

 

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FFA -phases

  1. Where does fluorescein enter eye and its course?
  2. Why difficult to see choroidal circulation?

 

 

  1. Fluorescein enters eye through ophthalmic artery & passes to choroidal circulation slightly before retinal circulation
  2.  b/c it fills quickly with free fluorescein & the RPE blocks the view of choroidal fluorescence 

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FFA -phases

  1. Phases? How many ?

5 phases : 

  1. Choroidal
  2. Arterial
  3. Arteriovenous
  4. Venous
  5. Late 

 

 

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FFA –phases -choroidal

  1. Other name ?
  2. Time?
  3. Appearance of choroid?
  4. What artery fills?

  1. Pre-arterial phase
  2. 8-12 seconds after dye injected
  3. Patchy filling of choroid as fluorescein leaks through the choriocapillaries
  4. Cilioretinal artery (if present) fills now 

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FFA –phases -Arterial

 

  • Arterial filling seen
  • Choroidal filling continues 

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FFA –phases -Arteriovenous
 

 

  • Complete filling of arteries & capillaries
  • Lines the venous walls leaving a strip
  • Choroidal fluorescence increases (not so obvious in highly pigmented eyes) 

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FFA –phases -venous

1. Early?

2. Mid?

3. Late?

  1. Early
    Complete arterial & capillary filling
     
  2. Mid
    Almost complete venous filling
     
  3. Late
    ​Complete venous filling
    Decreased concentration of dye in arterie 

 

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FFA –phases -late

Effects?

Intensity?

How long no longer seen?

How long to get eliminated?

  • Late/elimination phase - excrete via urine
  • Shows effects of continuous recirculation, dilution & elimination of the dye
  • Intensity of fluorescein becomes weaker
  • Fluorescein no longer seen on FFA after 10 mins
  • Eliminated from body within 24 hours 

 

 

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Hyperfluorescence

  1. Cause?
  2. Types?

  1. ↑ fluorescence could be c/b normal density of fluorescein in the fundus or ↑ in fluorescein content in the tissues
  2. Types of hyperfluorescence (abnormal)
    Transmission/window defect
    Pooling
    Leakage
    Staining 

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Hyperfluorescence

Transmission/window defect

Cause?

 

Atrophy/absence of the RPE 

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Hyperfluorescence - Pooling

Causes?

Dye pools in the anatomical space as a result of breakdown of the outer blood-retina barrier 

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Hyperfluorescence​- Leakage 

Causes?

Can arise from abnormal choroidal vessels (neovascularisation

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Hypofluorescence

  1. Cause ?
  2. Types? (3)

  1. ↓ in presence of fluorescein
    optical obstruction of normal density of fluorescein in the tissue or by low perfusion of tissue 
  2. Types of hypofluorescence (abnormal)
    Blockage of retinal fluorescence
    Blockage of background choroidal fluorescence
    Filling defects 

 

 

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Hypofluorescence
Blockage of retinal fluorescence

Causes?

  • Can be due to lesions anterior to the retina such as severe bleeding

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Hypofluorescence
Blockage of background choroidal fluorescence

Cause?

Caused by conditions which block fluorescence of BOTH choroid and retina

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Hypofluorescence- Filling defects

Cause?

Caused by vascular occlusion
or loss of vascular bed 

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43

What to look for in FUNDUS?

1. Disc?

2. Vessel?

3. Macula?

4. Peripheral retina?

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Look carefully at the

  1. Disc
    Clear/blurry edges?
    Oval/irregular shape?
    Cupping?
  2. Vessels
    Blockages/leakage?
  3. Macula
    Slightly darker red?
    Deposits/abnormalities?
  4. Peripheral retina
    Colour/abnormalities? 

 

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Optical Coherence Tomography​
Types of OCT

  1. Stratus OCT
  2. Cirrus OCT 

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