Acquired Macular Disorders

Question 1

Size of macula, fovea, foveal avascular zone, foveola and umbo

Answer 1

Macula - 5-6mm, more than one layer of ganglion cells, has yellow xanthophyll carotenoid pigments
Fovea - 1.5mm same size as optic disc! Depression at centre of macula
FAZ - between fovea and foveola, varies, average of 0.6mm
Foveola - 0.35mm. Thinest part of retina, centre floor of fovea, NO ganglion cells, just cone photoreceptors
Umbo - centre of foveola

Question 2

Signs of macular function

Answer 2

VA (distance and near!)
Contrast sensitivity
Amsler grid
Plus lens test (look for hypermetropic shift in e.g. CSR)
Usually not affected but need to be tested: pupils and colour vision

Question 3

Symptoms of macular dysfunction

Answer 3

Blurred vision, positive scotoma, metamorphopsia, micropsia, macropods, difficulty with dark adaptation (poor vision in dim light and persistence of after-images), and less frequently trouble with colour discrimination

Question 4

Mechanism of dark appearance of fovea in FFA

Answer 4

1. Absence of blood vessels in FAZ
2. Blockage of background choroidal hyperfluorescence by high density of xanthophyll
3. Blockage of background choroidal hyperfluorescence by RPEs which are larger and containing more melanin and lipofusin than elsewhere

Question 5

Five phases of FFA

Answer 5

Choroidal, arterial, arteriovenous, venous, late/recirculation

Question 6

Cotton wool spot vs exudate vs drusen

Answer 6

Cotton wool spot - ischaemia of nerve fiber layer -> oedema, white fluffy appearance
Exudate - lipid deposit from leaky vessels, hard yellow appearance, usually in inner nuclear (where outer retinal capillary plexus is)/outer plexiform layer
Drusen - multi-constituent deposit between RPE and Bruch membrane near macula seen in AMD, but can also be in peripheral fundus. Soft yellow appearance.

Question 7

Two types of classification of AMD

Answer 7

1. Dry vs wet
   - dry, 90% of AMD. Geographic atrophy is the advanced stage of dry.
   - wet, rapid progression. Main manifestations are CNV, PED but also retinal angiomatous proliferation (RAP) and polypoidal choroidal vasculopathy (PCV)
2. Stages
   - normal aging: drupelets only, no AMD pigmentary abnormalities
   - early AMD: medium drusen, no AMD pigmentary abnormalities
   - intermediate AMD: large drusen or any AMD pigmentary abnormalities
   - late AMD: neovascular AMD or GA

Question 8

Risk factors for AMD

Answer 8

Age
Race (white!)
Family history (tripled risk if first degree relative)
Smoking (doubled risk)
HTN
Diet: High fat intake and obesity; and high antioxidant intake have protective effect (substantial evidence from AREDS studies 1&2)
Aspirin: increase risk of neovascular AMD more so than other antiplatelet alternative?
Less certain ones: cataract surgery, blue iris colour, sunlight exposure and female

Question 9

Age related drusen is common by which decade?

Answer 9

The sixth decade, uncommon before the fourth decade - presence of drusen prior to this should prompt consideration of other causes (Doyne honeycomb retinal dystrophy, cuticular drusen, type 2 membranoproliferative GN)

Question 10

Is drusen singular or plural

Answer 10

Plural! Singular is druse 🙄

Question 11

Drupelets vs medium drusen vs large drusen and their risk of progression to late AMD in the next 5 years

Answer 11

Drupelet - <=63microns, little rush unless associated with pigmentary abnormalities
Medium drusen - between 63 and 125microns, small risk if alone, but 10% risk if associated with bilateral pigmentary changes
Large drusen - >125microns, 13% risk alone and 50% risk if associated with bilateral pigmentary changes 😱

Usually estimated by comparison with retinal vein at optic disc margin as its diameter is roughly 125microns

Question 12

Risk of intravitreal injection

Answer 12

Serious infection of the eye, bleeding, retinal detachment, inflammation of the eye (sterile uveitis), increase IOP and damage to the lens (which could lead to cataract)