Retinal Vascular Diseases: Pathology and Clinical Features

Comprehensive vocabulary flashcards covering the pathology, pathogenesis, clinical features, grading systems, and management classifications of diabetic retinopathy, hypertensive retinopathy, and retinal vascular occlusions.

Type 1 Diabetes Mellitus

A major classification of diabetes characterised primarily by insulin deficiency.

Type 2 Diabetes Mellitus

A classification of diabetes characterised primarily by insulin resistance.

Duration of Diabetes (Retinopathy Risk)

The single most important risk factor for diabetic retinopathy according to Klein et al. (Wisconsin Epidemiologic Study of Diabetic Retinopathy); approximately $90\%$ of patients have diabetic retinopathy $30\text{ years}$ after diagnosis, compared to only $5\%$ at initial presentation.

Retinal Capillary Occlusion (Diabetic Pathogenesis)

Capillary closure occurring in both superficial and deep vascular networks caused by basement membrane thickening, endothelial cell damage, red blood cell alterations, and increased platelet stickiness.

Pericyte Degeneration

The selective loss and degeneration of capillary mural cells (pericytes) induced by elevated glucose, compromising vascular structural integrity and leading to microaneurysm formation and leakage.

Hard Exudates

Intraretinal lipid deposits formed secondary to chronic breakdown of the blood-retinal barrier and persistent fluid leakage from damaged retinal capillaries.

Background Diabetic Retinopathy

The earliest stage of diabetic retinopathy characterized by microaneurysms, dot and blot haemorrhages, flame haemorrhages, and hard exudates outside the fovea.

Pre-proliferative Diabetic Retinopathy

An advanced stage of non-proliferative retinopathy signifying worsening retinal ischemia, characterized by cotton wool spots, intra-retinal microvascular abnormalities (IRMA), and venous changes including beading and looping.

Intra-retinal Microvascular Abnormalities (IRMA)

Abnormal dilated capillary shunt vessels connecting arterioles to venules across areas of retinal capillary non-perfusion to bypass occlusion.

Proliferative Diabetic Retinopathy (PDR)

Advanced diabetic eye disease characterized by neovascularisation at the disc (NVD) or elsewhere (NVE), pre-retinal haemorrhages, vitreous haemorrhages, and tractional retinal detachment.

Pre-retinal Haemorrhage

An accumulation of blood trapped between the internal limiting membrane and posterior hyaloid face, classically demonstrating a horizontal fluid level and boat-shaped appearance.

Clinically Significant Macular Oedema (CSMO)

An ETDRS-defined criterion for diabetic macular oedema meeting any of: retinal oedema within $500\,\mu\text{m}$ of the foveal centre; hard exudates within $500\,\mu\text{m}$ of the foveal centre if accompanied by adjacent thickening; or retinal oedema of $\ge 1\text{ disc area}$ situated within $1\text{ disc diameter}$ ($1500\,\mu\text{m}$) of the foveal centre.

Ischaemic Diabetic Maculopathy

A form of maculopathy wherein the macular fundus appearance is relatively normal despite significantly degraded visual acuity due to widespread parafoveal capillary closure.

Diabetic Refractive Shift (Lens Osmotic Mechanism)

Reversible changes in lens power where acute hyperglycaemia induces sorbitol accumulation, creating an osmotic gradient that pulls water into the lens to cause an increase in lens diameter by $0.3\,\text{mm}$, a decrease in refractive index ($1.42$ to $1.40$), and a myopic shift (mean $\approx 3\,\text{D}$), followed by transient hyperopia after strict glucose control.

Diabetic Third Cranial Nerve Palsy

An extraocular muscle motor palsy resulting from microvascular ischaemic insult to the oculomotor nerve, presenting with ptosis and a 'down and out' globe orientation, characteristically sparing the pupillary light reflex.

Arcus Senilis

A white or grayish corneal peripheral stromal ring resulting from lipid infiltration, which in younger patients serves as a significant clinical indicator of systemic hyperlipidaemia.

Accelerated (Malignant) Hypertension

Blood pressure elevated to $\ge 180/120\,\text{mmHg}$ (frequently exceeding $220/120\,\text{mmHg}$) associated with acute end-organ damage manifest as retinal haemorrhages, cotton-wool spots, and optic disc swelling (papilloedema).

Vasoconstrictive Phase

The earliest pathophysiologic stage of hypertensive retinopathy wherein arteriolar autoregulatory tone produces generalized arteriolar narrowing.

Sclerotic Phase

The chronic phase of hypertensive retinopathy caused by persistent elevated blood pressure, leading to vessel wall hyalinization, smooth muscle loss, arteriovenous crossing abnormalities, and broadening of the arteriolar reflex (copper and silver wiring).

Focal Intraretinal Periarteriole Transudates (FIPTs)

Small ($< 1/4\text{ disc diameter}$), round or oval white intraretinal lesions caused by leakage of plasma macromolecules along deep retinal arterioles; a sign specific to hypertension.

Keith–Wagener–Barker Classification (Grade 4)

The most advanced tier of hypertensive retinopathy under the Keith–Wagener–Barker system, characterized by Grade 3 findings (arteriolar nipping, retinal oedema, microaneurysms, cotton-wool spots, haemorrhages) plus optic disc swelling (papilledema) and macular oedema.

Salus' Sign

An arteriovenous crossing sign characterized by the deflection or deviation of a retinal vein out of its normal trajectory as it passes under a sclerotic arteriole.

Gunn's Sign

An arteriovenous crossing abnormality characterized by apparent tapering and concealment of the vein on either side of an overlying sclerosed retinal arteriole.

Bonnet's Sign

An arteriovenous crossing phenomenon marked by banking or distal dilation of the retinal vein due to compression at the arteriovenous crossing point.

Elschnig's Spots

Focal, non-perfused choriocapillaris lesions presenting as circumscribed retinal pigment epithelial alterations, pathognomonic of hypertensive choroidopathy.

Siegrists Streaks

Linear hyperpigmented streaks arranged along sclerosed choroidal vessels, observed in hypertensive choroidopathy in severe hypertension.

Central Retinal Vein Occlusion (CRVO)

A venous obstructive disorder caused by thrombosis of the central retinal vein at or posterior to the lamina cribrosa, presenting with blot and flame haemorrhages, cotton-wool spots, venous tortuosity, and optic disc oedema distributed across all four retinal quadrants.

Branch Retinal Vein Occlusion (BRVO)

A localized retinal vein occlusion typically occurring at an arteriovenous crossing due to mechanical arteriolar compression, occurring up to $7\times$ more frequently than CRVO, with two-thirds localized to the superotemporal quadrant.

Hemi-retinal Vein Occlusion (HRVO)

A retinal venous occlusion occurring at the optic disc that produces extensive intraretinal haemorrhages and vascular changes involving one hemisphere (half) of the fundus.

Central Retinal Artery Occlusion (CRAO)

An acute interruption of central retinal arterial perfusion leading to sudden, complete, painless monocular visual loss, a dense RAPD, profound retinal whitening/oedema, vascular attenuation, and a macular cherry-red spot.

Amaurosis Fugax

A transient ischemic attack causing sudden, temporary monocular vision loss classically characterized as a curtain falling over the field of vision to complete darkness, carrying a substantial risk for impending stroke.

Rubeosis Iridis (NVI)

Neovascularisation of the iris emerging secondary to widespread ocular ischaemia (commonly following ischaemic CRVO or proliferative retinopathy), which starts at the pupillary margin and can trigger intractable neovascular glaucoma ('100-day glaucoma').

Vasoformative Substance (VEGF / IGF-1)

Soluble growth factors released by hypoxic retinal tissue that diffuse throughout the intraocular environment to stimulate pre-retinal and iris neovascularisation.