Monday, January 23
Last blogged @ 22:05

Cotton Wool Spots (CWS) is the accumulation of mitochondria and ruptured cells within areas of the nerve fibre layers. It is caused by the vascular disease that stops/reduces the axoplasmic transport. It is a sign of ischemia or microinfarct. Ischemia is an insifficient blood blood supply. Microinfarct refers to the mini localised area of ischemic necrosis produced by the occlusion of arterial supply or venous drainage at that part. CWS reabsorbs over 6-8 weeks in which it will leave a groove in the nerve fibre layers and an arcuate visual field defect.

Hard exudates is the lipid and lipoprotein deposition between areas of functional and diseased retina. It is caused by an increased vascular permeability. It is seen as a well-defined, waxy, shiny area in the outer plexiform layer. It can be in the form of individual dots, circinate (circular or ring-shaped) or a macular star.

Retinal Oedema consists of 3 types namely Superficial, Deep and Cloudy. Superficial retinal oedema is seen as a diffuse haze in the nerve fibre layers. It is common at the optic nerve head and posterior pole. It occurs in hypertension and/or papilloedema. Deep retinal oedema is seen as a dense haze in the nerve fibre layers. It is common at the macula and posterior pole. It occurs in post-cataract surgery and diabetes. Cloudy retinal oedema is seen as white/opaque. It is caused by arterial occlusion and ischemia.

Retinal Haemorrhages consists of 6 types namely Pre-retinal, Flame-shaped, Dot-blot, Sub-retinal, Sub-RPE and Vitreous. Pre-retinal haemorrhage is posterior to the inner limiting membrane. It obscures the retinal blood vessels. It is seen as patches or boat-shaped/D-shaped. It may or may not be due to ocular disease(s). Flame-shaped haemorrhage is within the nerve fibre layer. It follows the stucture of the ganglion cell fibres. It is associatied with the vascular disease affecting th esuperficial and peripapillary capillary bed. Roth's spots is a flame-shaped haemorrhage with a white/pale cente and is associated with systemic inflammation. Dot-blot haemorrhage is between the inner nuclear layer and outer plexiform layer. It is seen as round dots because they follow the divergence of axons. It takes longer to resolve as compared to superficial retinal haemorrhage. Sub-retinal haemorrhage is between the sensory retina and RPE. It is seen as sark coloured with retinal vessels clearly visible above it. It is amorphous. It is associated with retinal detachment and retinal pigmented epithelium detachment. It resolves slowly. Sub-RPE haemorrhage is between the RPE and Bruch's membrane. It has the same appearance as a sub-retinal haemorrhage but with well-defined borders. It is associated with retinal detachment and retinal pigmented epithelium detachment. It resolves slowly. Vitreous haemorrhage is caused when blood leaks through the inner limiting membrane into the vitreous. It is seen in trauma and/or retinal detachment.

Microaneurysms is the saccular balooning of weakened endothelial walls. It is caused by capillary occlusion or venous stasis in the inner nuclear layer. It is seen as small, round, dark red dots, 1/2 the size of the central retinal vein. It is very leaky and may cause oedema.

Neovascularisation is the response of an ischemic attack. It is caused by the starved retina which releases angiogenic molecules VEGF (vascular endothelial growth factor) to promote new vessel growth. Areas of growth include everywhere (NVE), at the disc (NVD) and iris (NVI). It is a fibrotic proliferation and there is a risk of a tractional retinal detachment.