Fundoscopic Appearances of Retinal Pathologies

This article aims to provide an overview of the fundoscopic appearances of common retinal pathologies which may be asked to identify in an OSCE scenario.

Normal Appearance of the Retina

• The key parts of the retina to recognise are the optic nerve head (optic disc) and the macula.
• The optic nerve is found by tracing any of the blood vessels to the point of coalescence.
• The macula is found lateral (temporal) to the optic nerve head. The central part of the macula, the “fovea” is about the same diameter as the optic disc and appears darker than the rest of the macula due to the presence of an additional pigment.

Diabetic Retinopathy

• Diabetic retinopathy is a form of micro-angiopathy causing damage to the small blood vessels of the retina as a result of hyperglycaemia.
• The most important risk factors for developing diabetic retinopathy are the duration of diabetes and poor diabetic control. Other vascular risk factors like hypertension, hyperlipidaemia and smoking also contribute to the risk of developing diabetic retinopathy.

Clinical Signs of Diabetic Retinopathy

• The spectrum of diabetic retinopathy is show below

Background Diabetic Retinopathy

Microaneurysms

• Microaneurysms are localised outpouchings of capillaries that leak plasma constituents into the retina.
• May be clinically indistinguishable from small dot and blot haemorrhages (see below).

Dot and blot haemorrhages

• Dot and blot haemorrhages arise from bleeding capillaries in the middle layers of the retina.
• They may look like microaneurysms if small enough. It is not particularly important to be able to distinguish between small haemorrhages and microaneurysms as they are both parts of pre-proliferative retinopathy.

Hard exudates

• Hard exudates are waxy yellow lesions with relatively distinct margins arranged in clumps or rings, often surrounding leaking microaneurysms.
• NB: They are called “hard exudates” to distinguish them from “soft exudates”, an older term for cotton wool spots (see below).

Pre-proliferative diabetic retinopathy

The presence of retinal ischaemia represents a progression from background diabetic retinopathy to the pre-proliferative stage.

Cotton wool spots

• Cotton wool spots appear as small, fluffy, whitish superficial lesions.
• They are accumulations of dead nerve cells from ischaemic damage.

Other signs

• Other signs of pre-proliferative retinopathy include venous changes and intraretinal microvascular anomalies (IRMA) but you would not be expected to know or recognise them at the undergraduate level.

Proliferative diabetic retinopathy

• Insufficient retinal perfusion eventually leads to the development of new vessels on the retina (neovascularisation).
• These new vessels may either be at the disc, termed “new vessels at the disc” (NVD), or over the other areas of the retina “new vessels elsewhere” (NVE).

Advanced diabetic retinopathy

• The final stage of diabetic retinopathy involves the development of scar tissue which pulls the layers of the retina apart, eventually leading to retinal detachment.

Pan-Retinal Photocoagulation (PRP)

• Pan-retinal photocoagulation is the primary treatment for proliferative diabetic retinopathy.
• The rationale behind the treatment is to convert ischaemic retina to infarcted retina, which cannot produce further neovascularisation.
• Clinically it is seen as clusters of burn marks on the retina which have been created by the laser used in the treatment process.

Diabetic Maculopathy

• Diabetic maculopathy refers to any diabetic changes over the macula.
• The term is typically reserved for sight-threatening features such as macular oedema.
• You are unlikely to be asked to identify oedema as it is hard to visualise using a direct ophthalmoscope.

Hypertensive Retinopathy

Chronic Hypertension

• Grade 1 disease – The changes of early hypertensive retinopathy are subtle, with generalised arteriolar narrowing.
• Grade 2 disease – Development of areas of focal narrowing, and compression of venules at sites of arteriovenous crossing (AV nipping).
• Grade 3 disease – Development of features similar to those of diabetic retinopathy, namely retinal haemorrhages, hard exudates and cotton wool spots.

Malignant Hypertension

• Malignant hypertension typically presents with grade 4 hypertensive eye disease, which includes all the features of grade 3, with the addition of optic disc swelling.
• Other features include headaches, eye pain, reduced visual acuity and focal neurological deficits.
• Initial management typically involves intravenous antihypertensives and emergency hospital admission.
• The image below shows extensive haemorrhages, cotton wool spots, optic disc swelling and a ring of exudates around the macula (macular star).

Optic Nerve Pathologies

Glaucomatous Disc Changes

• Glaucoma is defined as a progressive optic neuropathy that is associated with visual field loss and raised intraocular pressure (IOP).
• Glaucoma results in irreversible loss of nerve fibres, leading to an appearance of “cupping” or an increased vertical cup-to-disc ratio (C/D ratio).

Papilloedema / Optic Nerve Swelling

• Papilloedema refers to optic disc swelling secondary to raised intracranial pressure.
• “Optic disc swelling” is a general term referring to any cause of a swollen optic disc.
• Causes of optic disc swelling include intracranial space-occupying lesions, optic neuritis (multiple sclerosis), malignant hypertension and uveitis (tuberculosis, sarcoidosis etc.).
• Optic disc margins appear blurred and small haemorrhages may be noted.

Optic Nerve Atrophy

• Primary optic nerve atrophy is caused by inflammation (optic neuritis), glaucoma or general retinal ischaemia.
• Secondary optic nerve atrophy is caused by longstanding papilloedema.
• A pale optic disc is noted in optic nerve atrophy.

Vascular Occlusive Diseases

Central Retinal Artery Occlusion (CRAO)

• Central retinal artery occlusion presents with sudden, profound loss of vision.
• It is caused by emboli obstructing the retinal artery (e.g. stroke, giant cell arteritis).
• Classical appearance is of a “cherry red spot”. This occurs due to the intact reflex of the fovea standing out against a pale, ischaemic retina.

Central Retinal Vein Occlusion (CRVO)

• Central retinal vein occlusion occurs secondary to atherosclerotic thickening of the central retinal artery compressing the central retinal vein at a common crossing point.
• Occlusion of the vein results in retinal hypoxia, and the resultant endothelial cell damage leads to extravasation of blood.
• Fundoscopy typically reveals severe tortuosity, engorgement of retinal veins, deep haemorrhages, cotton wool spots and optic disc swelling.

Macular Pathology

Age-related Macular Degeneration (AMD)

• Age-related macular degeneration is a degenerative disorder of the macula and the most common cause of irreversible blindness in the elderly population.
• The most common form of AMD (90% of cases) is the “dry” variant, termed so as it produces no exudation or neovascularisation.
• Early signs of AMD include the presence of yellow-white deposits which are termed “drusen”.

References

Reference Images

1. Normal fundus photograph provided courtesy of Yandle on Flickr for re-use under CC BY 2.0.
2. All diabetic retinopathy, optic nerve pathologies, and CRVO photographs provided by Community Eye Health on Flickr for non-commercial reuse under CC BY-NC 2.0.
3. Photograph of AV nipping originally provided by Frank Wood for re-use under CC BY 3.0.
4. Photograph of a cherry red spot originally provided by Fieß et al. and BioMed Central Ltd. Under CC BY 2.0.
5. Photograph of AMD provided by National Eye Institute on Flickr for re-use under CC BY 2.0.
6. Ophthalmic Atlas Images by EyeRounds.org, The University of Iowa are licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.
   
7. Blausen.com staff (2014). “Medical gallery of Blausen Medical 2014”. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. [CC BY 3.0 ]. Modified by Dr Lewis Potter.

Reference Texts

Kanski JJ, Bowling B. Clinical Ophthalmology: A Systematic Approach. Edinburgh, Elsevier/Saunders; 2015.

Vaughan CJ, Delanty N. Hypertensive emergencies. Lancet. 2000; 356:411–417.