OPH - Macular Degeneration & Retinopathy

Question 1

Age-Related Macular Degeneration (AMD)

Macula
Pathophysiology
Risk Factors
Drusen
Wet AMD

Answer 1

1. ) Macula - responsible for central and colour vision
   - the highest concentration of photoreceptor cells
   - 4 layers: photoreceptors –> retinal pigment epithelium (RPE) –> Bruch’s membrane –> choroid
2. ) Pathophysiology - degeneration in the macula that causes a progressive deterioration in vision
   - degeneration of photoreceptors, atrophy of RPE
   - classified into dry (90%) or wet (10%)
3. ) Risk Factors
   - ↑age, women, FH, smoking, HTN, CVD
   - hypermetropia, light-coloured iris
   - White or Chinese ethnic origin
4. ) Drusen - undigested cellular debris from degeneration of RPE cells accumulates as ‘drusen’
   - yellow/white deposits of proteins and lipids appear between RPE and Bruch’s membrane,
   - normal part of the ageing process but larger (‘soft drusen’) and greater numbers is an early sign of AMD
5. ) Wet Age-Related Macular Degeneration
   - drusen–> inflammation–> macrophages – > ↑VEGF
   - VEGF (vascular endothelial) stimulates the growth of new blood vessels from the choroid into the retina
   - vessels can leak fluid or blood and cause oedema and more rapid loss of vision so has a worse prognosis

Question 2

Management of AMD

Clinical Features
Examination/Investigations x6
Management

Answer 2

1. ) Clinical Features
   - progressive loss of central vision (can inc scotoma)
   - ↓visual acuity esp for near objects
   - visual fluctuation, worse at night
   - metamorphosis: visual distortion where straight lines appear curved/crooked/wavy
   - presents as difficulty reading text, recognizing faces and vision problems in dim light
   - wet AMD presents more acutely (days/weeks) and often progresses to bilateral disease
2. ) Examination/Investigations
   - slit lamp: diagnostic for AMD
   - OCT (1°) or fluorescein angiography: wet AMD
   - fundoscopy: drusen, macular oedema (wet), well-demarcated red patches suggest leakage in wet AMD
   - Snellen chart: reduced visual acuity
   - visual field testing: central scotoma
   - Amsler grid: assess the distortion of straight lines
3. ) Management
   - dry: lifestyle (↓smoking, control BP, vitamin supp…
   - wet: intravitreal anti-VEGF injections once a month can slow or reverse progression (start w/in 3mths)
   - anti-VEGF: ranibizumab, bevacizumab, pegaptanib

Question 3

Diabetic Retinopathy

Pathophysiology
Complications
Management

Answer 3

1. ) Pathophysiology - hyperglycaemia causes damage to the small blood vessels of the retina, leading to:
   - vascular occlusion and leakage of the retinal vessels
   - retinal ischaemia and neovascularisation
   - risk factors: duration of diabetes, poor diabetes control, other vascular r.f. e.g. HTN, smoking, obesity…
2. ) Complications
   - retinal detachment, vitreous haemorrhage
   - rubeosis iridis –> glaucoma
   - optic neuropathy, cataracts
3. ) Management
   - mild NPDR: lifestyle (control diabetes/HTN, exercise, weight loss, ↓cholesterol, stop smoking)
   - mod-severe NPDR: follow up every 3 months
   - PDR: pan-retinal photocoagulation w/in 2wks (↓VEGF production by ↓O2 demand from the peripheral retina)
   - central involving DM: IV anti-VEGF medications e.g ranibizumab, bevacizumab, IV Iluvien if persistent
   - vitreoretinal surgery (keyhole surgery on the eye) may be required in severe disease

Question 4

Classification of Diabetic Retinopathy

Non-Proliferative (NPDR)
Proliferative (PDR)
Diabetic Maculopathy

Answer 4

1. ) Non-Proliferative - aka background retinopathy
   - mild: microaneurysms
   - moderate: blot haemorrhages, cotton wool spots, hard exudates, venous beading
   - severe: presence of microaneurysms and blot haemorrhages in 4 quadrants WITH venous beading in 2 quadrants WITH IrMA in any 1 quadrant
2. ) Proliferative - ↓blood supply to retina –> release of VEGF –> formation of new blood vessels which are not as effective which can create some problems:
   - recurrent vitreous haemorrhage
   - retinal (traction) detachment: vessels grow into the vitreous, forming fibrous bands suspending the retina
   - rubeosis iridis: neovascularisation at the iris and drainage angle resulting in ↑IOP –> glaucoma
3. ) Diabetic Maculopathy - macular oedema caused by leakage of the vessels close to the macula
   - can cause ischaemic maculopathy which is a sight-threatening emergency
   - types: focal, diffuse, ischaemic, central involving
   - central involving is thickening within 400µm from the centre of the fovea, treat w/ anti-VEGF therapies

Question 5

Fundus/Retinal Changes in Diabetic Retinopathy

Microaneurysms 
Blot Haemorrhages
Cotton Wool Spots
Hard Exudates
Venous Beading
Intraretinal Microvascular Abnormalities (IrMA)
Neovascularisation

Answer 5

1. ) Microaneurysms - outpouchings of capillaries due to weakness caused by damage to blood vessel walls
   - leak plasma constituents into the retina
   - present in mild NPDR
2. ) Blot Haemorrhages - bleeding capillaries in the retinal middle layers due to ↑vascular permeability
   - difficult to differentiate from microaneurysms
   - present in moderate NPDR
3. ) Cotton Wool Spots - accumulations of dead nerve cells from ischaemic damage from arteriolar occlusion
   - appear as small, fluffy, whitish superficial lesions
   - present in moderate NPDR - sign of retinal ischaemia
4. ) Hard Exudates - leakage of fluid and lipids into the retina due to increased vascular permeability
   - yellow/white deposits of lipids in the retina
   - present in moderate NPDR
5. ) Venous Beading - irregular constriction and dilation of venules in the retina due to vessel wall damage
   - walls of the veins are thicker and no longer straight and parallel and look more like a string of beads
   - present in moderate (late-stage) NPDR
6. ) Intraretinal Microvascular Abnormalities (IrMA)
   - dilated and tortuous capillaries in the retina which can act as a shunt between arterial and venous vessels
   - present in severe NPDR
7. ) Neovascularisation - development of new blood vessels on the retina caused by the release of VEGF due to insufficient retinal perfusion
   - vessels can be at the disc (NVD) or elsewhere (NVE)
   - occurs in proliferative diabetic retinopathy (PDR) (also in wet AMD)
   - can lead to vitreous haemorrhage and retinal detachment

Question 6

Hypertensive Retinopathy

Pathophysiology
Signs on Fundoscopy
Keith-Wagener Classification
Management

Answer 6

1. ) Pathophysiology - damage to the small retinal blood vessels due to systemic hypertension
   - either due to chronic or malignant hypertension
   - malignant hypertension often presents as grade 4
2. ) Signs on Fundoscopy
   - flame haemorrhages and hard exudates due to damaged vessels leaking blood/lipids into the retina
   - cotton wool spots due to ischaemia to nerve fibres
   - silver/copper wiring: arteriole walls become thickened and sclerosed –> ↑ reflection of the light
   - arteriovenous nipping: arterioles cause compression of the veins where they cross due to sclerosing
   - papilledema: ischaemia to optic nerve –> swelling (oedema) and blurring of the disc margins
3. ) Keith-Wagener Classification - 4 stages
   - 1: mild narrowing of the arterioles
   - 2: focal constriction of blood vessels and AV nipping
   - 3: cotton-wool spots, exudates and haemorrhages
   - 4: papilledema: blurring of the optic disc margin
4. ) Management
   - control BP and other risk factors e.g. smoking, lipids