1-7,8 Fundus Dystrophy and Degenerations Flashcards
AMD
- Which part of vision is affected?
- Effect on vision?
- Fast or slow effect?
- Fundus characteristics?
- Central
- Wavy vision with decreased sharpness
- Slow
- Fuzzy specks of yellow deposits around the macular. Macular drusen at bruch’s membrane (since not at retina, it’s fuzzy looking).
AMD risk factors
- Age (main risk factor)
- Family history
- White people with light irises
- Smoking (decreases antioxidants)
- UV
- High BMI
- Not enough veges/Vit. C + E supplements
AMD why affect central vision only?
- High O2 demand for high density of photoreceptors
- No retinal BVs or reliance on choroid
- Aging will thin choriocapillaris density + diameter leading to reduced blood flow at macula.
- Oxidative damage with age
- Cumulative light damage with age
RPE function
- Phagocytose outer segment of photoreceptors
- Tight junctions prevent blood from choroid getting to retina
- Absorb light
- Give nutrients to photoreceptors
- and other stuff…
AMD
- Initial pathophysiology
- Role of choroid in AMD?
- Chronic inflammation
- Lipofuschin is the lipid residue left over after RPE digest photoreceptor outer segments.
-> They accumulate with age and react with light to form ROS which are toxic to RPE.
-> RPE is damaged and can’t clear cellular waste as well (accumulates between RPE and bruch’s membrane) so they engorge with lipofushin which inhibit their ability to digest photoreceptors which means photoreceptors die. - Choroid thins with age
- Choroid loses vaculature with age
- Accumulation of membrane attack complex (MAC) in vasculature along with mast + macrophage activation.
- Lipofuscin can be stimuli for chronic inflammation. Site for drusen formation.
AMD:
- Atrophic
- Exudative (pathophyisiology)
Atrophic (dry/non-exudative):
- Most cases
- Progresses to geographic atrophy due to photoreceptor death
Exudative (wet):
- Slow progression of even more severe vision loss
- Drusen accumulates into soft drusen. Causes RPE detached.
-> Ischemic tissues release VEGF which stimulate neovascularisation below the RPE.
-> New vessels prone to hemorrhage so becomes wet AMD.
-> Can then scar which can lead to retinal detachment. Leads to more global blindness.
Appearance of AMD:
- Atrophic
- Exudative
Atrophic:
- OCT shows areas where photoreceptors are missing and choroid has died.
- Fundus angiography shows choroid visibility where RPE is missing
Exudative:
- Fundus photo shows diffuse fluid build up
- OCT shows pools of fluid between RPE and choroid causing RPE detachment and fluid can get into retinal layers causing retinal detachment (RPE from retina).
- Haemorrhage can be seen as pool of blood.
- Scarring can be seen around macular
AMD treatment?
- Dry AMD?
- Wet AMD?
- Originally, dietary antioxidant supplements.
- Now, intravitreal injections of Syfovre and Izervay (C3 and C5 inhibitors). Reduces inflammation which would otherwise lead to GA.
- Thermal laser photocoagulation (scar tissue formation to seal leaky BVs)
- Photodynamic therapy (laser activation of compound injected into bloodstream which destroys new BVs).
- Anti-VEGF therapy (inject into vitreous, prevent new BVs).
- The basis of myopic maculopathy arises from…
- How much myopia is needed for myopic maculopathy to occur?
- List all myopic maculopathy changes.
- Sclera is abnormally enlarged (axial myopia) but the retina and choroid get thinner when stretched.
- Any amount of myopia increases risk, with greater risk increase at higher levels of myope. RD included.
- Optic disc crescent
- Tessellated fundus
- Posterior staphyloma
- Chorioretinal atrophy
- Lacquer cracks
- Fuch’s spot
- Retinoschesis
Describe optic disc crescent
- In myopia, as the sclera is stretched, the retinal layers, choroid, RPE… all get pulled relative to each other. As a result, the different layers are revealed.
- This happens temporally due to a larger length of retina to ora serrata.
- Appears as this crescent that forms on the temporal side of ONH.
- May look similar to PPA but more uniform in shape and colour.
- No symptoms
Describe tesellated fundus
- In myopia, since everything’s stretched, RPE gets stretched which reduces its density which makes it more transparent. Now choroid is visible and the choroidal vessels are most visible.
- Appears as these blood vessels highlighted behind the retina.
- No symptoms
Describe chorioretinal atrophy and staphyloma
In myopia, retina and choroid can die (chorioretinal atrophy) if there’s extreme localised buldging (staphyloma)
- Sclera can be seen (whiter spots) since retina and choroid have died at some points.
- Retinal vessels can also become straighter as the eye grows.
Describe Lacquer cracks
- In myopia, breaks in Bruch’s membrane due to stretching can happen in extreme cases.
- Appears as fine irregular yellow lines, typically vertical
- New BVs can grow through cracks from choroid which affects vision.
- Poor central vision prognosis ;-;
Describe Fuch’s spot
In myopia, foveal choroidal neovascularisation. These can also haemorrhage which leaves raised scar and scotoma.
Describe macular retinoschisis in high myopia
- Inner retina adheres to ILM whilst outer retina ahderes to choroid. As choroid expands in myopia, the inner and outer retina are torn apart which splits the retinal layers.
- Can be visualisted in OCT.
