Understanding the Clinical Significance
of Common Retinal Lesions
Thomas F. Freddo, O.D., Ph.D., F.A.A.O.
Professor and Director
School of Optometry, University of Waterloo
Retinal Anatomy – reminders.
 Ophthalmoscopically visible vessels lie in the nerve fiber layer
 Where A and V cross, they share a common tunica adventitia.
 CRA gives rise to two distinct layers of capillaries in the retina
o Superficial capillary bed at the level of the ganglion cells
o Deep capillary bed at junction of INL and OPL
 Nerve fiber layer thickens progressively as it reaches the optic nerve
 The area round the disc is served by the radial peripapillary capillary plexus
o Diminished capacity for collateral flow in this region.
 So the area with the greatest dependent tissue mass in the nerve fiber layer has a
diminished capacity to provide collateral flow. It would make sense that a given amount
of vascular occlusion will be of greater clinical consequence in the peripillary region than
elsewhere.
Cotton-Wool Spots:
 Yellow, white, grey, fluffy lesions overlying or deflecting retinal vessels and most often
in the peripapillary region. 1/10th to 1/3 disc diameter.
 It is not an exudate, so the old term “soft exudate” should not be used.
 Expect them in HTN, DM and in conditions having a vascular occlusive component
o Collagen-vascular disease – immune-complex deposition
o Hyperviscosity/hypercoagulability states
o Embolic disorders
o Anemia
o HIV/AIDS
o Medications – such as interferon
 Cotton-wool spots as a solitary finding
o HIV retinopathy
 CWS earliest and most consistent finding in 50-60% of patients
o Interferon retinopathy
o SLE
 Pathobiology of CWS
o Correspond to areas of vascular occlusion and larger surrounding are of ischemia
o Cytoid bodies – Focal swelling in individual axons with lighter area appearing
like cytoplasm and a darker area looking like a nucleus but not basophilic
 Recent reconsideration of nerve fiber layer infarct concept.
o If the entire area of a CWS represents infarction, a significant sector defect should
result and it does not.
o Why cotton wool spots should not be regarded as retinal nerve fibre layer infarcts.
D McLeod British Journal of Ophthalmology 2005;89:229-237.
o Tso and Jampol’s definition of a CWS is “a disturbance of both retrograde and
orthograde axoplasmic transport...due to focal retinal ischaemia"
REMINDER – If a lesion is seen to cross a vessel, the lesion must in the nerve fiber layer or anterior to
that point (i.e. epiretinal or vitreal). If the vessel crosses the lesion, it is deeper than the nerve fiber
layer. Most such lesions are either in the OPL, between the photoreceptors and RPE or sub-RPE.
Hard Exudates:
 Yellow, punctuate lesions below the level of the retinal vessels.
 Expect them in diseases that affect capillaries and venules rather than arterioles
o DM
o Coats
o Capillary hemangioma
o Leber’s
o Arterial Hypertension! – how does this fit?
 Patterns
o Clustered punctate lesions
o Circinate pattern in macular region
o Filling the globe in Coats
White-centered Hemorrhage:
 Originally described by Moritz Roth
o Some now reserve the term Roth spot for those associated with sub-acute bacterial
endocarditis, the condition with which the lesion was originally described.
o A peri-papillary CWS with overlying flame-shaped hemorrhage, leaving a
window can mimic white centered hemorrhage.
 Expect them in
o Anemia or CO poisoning
o leukemia
o retinal phlebitis
o Candida albicans infection
o vascular diseases
o collagen diseases
o bacterial sepsis
o shaken-baby syndrome
o Can also be seen in diabetic retinopathy and hypertensive retinopathy
 What is the white center?
o In all cases studied by pathology, white center is a large fibin-laden clot.
Drusen:
 From the German word meaning granular nodule
 Differentiate from hard exudate by sharper border/window defect on FA
o Commonly present as incidental finding in non-macular retina
o A peri-papillary CWS with overlying flame-shaped hemorrhage, leaving a
window can mimic white centered hemorrhage
 Macular Drusen
o Hard – current literature suggests no concern for development of SRNVM
o Soft –
o Coalesced
 Other Drusen – Optic disc drusen – DDx disc edema; Giant drusen – astrocytoma in
tuberous sclerosis
Microaneurysms:
Retinal capillaries average 6 microns-and RBC is 7 microns
Continuous endothelium with tight junctions, surrounded by basement membrane, which
splits to encompass pericytes.
Occur at the edges of cotton wool spots or other areas of non-perfusion, ischemia. Primarily
occur in paramacular region and most readily seen with FA