Cherry Red Spot — Causes & Mechanisms

Classic cherry red spot: bright red fovea surrounded by perifoveal whitening (opacification of the inner retinal layers)

Anatomical Basis — Why Does a Cherry Red Spot Form?

• Surrounding macula: The thick inner retinal layers (ganglion cell layer, nerve fiber layer) become swollen/opacified → appear white/grey
• Fovea: No intervening inner layers → the normal red-orange color of the underlying choroidal circulation shines through
• Result: A bright red spot (fovea) against a white background (swollen perifovea)

Kanski (Clinical Ophthalmology, 9th ed.): "The cherry red spot is seen at the fovea because this area, devoid of ganglion cells, allows the underlying choroid to show through against the background of the pale, oedematous retina."

Classification of Causes

A. Vascular Causes

1. Central Retinal Artery Occlusion (CRAO)

• Sudden occlusion of CRA (embolic, thrombotic, or vasospastic) → stops blood supply to inner 2/3 of retina
• Ischemia → cytotoxic edema of the ganglion cell layer and nerve fiber layer → retinal whitening/opacification of parafoveal area
• The fovea receives its outer retinal nutrition from choroid (not CRA) → remains normally perfused and appears bright red
• Cherry red spot typically appears within a few hours of onset
• Resolves over 4–6 weeks as retinal cells undergo atrophy

Retinal and Ophthalmic Artery Occlusions (p. 12): "Retinal whitening is caused by opacification of the swollen, ischemic parafoveal nerve fiber layers. The cherry red spot is seen because the foveal center, free of nerve fiber layers, transmits the normal coloration of the underlying, unaffected choroid."

B. Storage Disorders (Lysosomal / Sphingolipidoses)

Kanski; Datta's Ophthalmology; Khurana — Comprehensive Ophthalmology: "In storage disorders, gangliosides or sphingolipids accumulate in the perifoveal ganglion cells, causing them to swell and turn opaque. The ganglion-cell-free fovea shows the red reflex of the choroid, creating the cherry red spot."

1. Tay-Sachs Disease (GM2 Gangliosidosis Type I)

• Enzyme defect: Hexosaminidase A deficiency (α-chain mutation)
• Storage material: GM2 ganglioside accumulates in ganglion cells
• Cherry red spot is a hallmark — present in nearly all infantile cases
• Associated: macrocephaly, hypotonia, exaggerated startle response, progressive neurodegeneration, death by age 2–3 years
• (Harrison's, p. 11857): "characterized by macrocephaly, loss of motor skills, increased startle reaction, and a macular cherry red spot"

2. Sandhoff Disease (GM2 Gangliosidosis Type II)

• Enzyme defect: Hexosaminidase A and B deficiency (β-chain mutation)
• Storage material: GM2 ganglioside + globoside in ganglion cells
• Phenotypically similar to Tay-Sachs; cherry red spot present
• Additional hepatosplenomegaly (due to globoside accumulation in viscera)

3. Niemann-Pick Disease (Types A & B)

• Enzyme defect: Sphingomyelinase deficiency
• Storage material: Sphingomyelin + cholesterol in reticuloendothelial cells and ganglion cells
• Type A (acute neuropathic): Cherry red spot in ~50% of cases; hepatosplenomegaly, neurodegeneration
• Type B (chronic): Milder; cherry red spot less common
• Khurana: Cherry red spot seen due to lipid-laden swollen ganglion cells in the perifoveal region

4. GM1 Gangliosidosis (Landing Disease)

• Enzyme defect: β-galactosidase deficiency
• Storage material: GM1 ganglioside, galactosyl oligosaccharides
• Cherry red spot present in infantile form (~50%)
• Coarse facial features, skeletal dysplasia, hepatosplenomegaly, neurodegeneration

5. Gaucher's Disease

• Enzyme defect: β-glucocerebrosidase deficiency
• Storage material: Glucocerebroside in reticuloendothelial system
• Cherry red spot is rare — seen occasionally in the acute neuropathic form (Type 2 Gaucher's)
• More common findings: pingueculae, perimacular halo

6. Metachromatic Leukodystrophy (MLD)

• Enzyme defect: Arylsulfatase A deficiency
• Storage material: Sulfatides in lysosomes of neurons and glial cells
• Cherry red spot occasionally reported in severe forms
• Primarily a white matter disease; optic atrophy may be prominent

7. Farber's Disease (Ceramidase Deficiency)

• Enzyme defect: Acid ceramidase deficiency
• Cherry red spot reported; rare condition

C. Traumatic / Other

Berlin's Edema (Commotio Retinae)

• Mechanism: Blunt trauma to the eye → concussive disruption of the outer photoreceptor layer at the macula
• Intracellular swelling in photoreceptor inner segments → whitish discoloration around fovea
• Fovea remains red against the white background → cherry red spot-like appearance
• (Kanski): This is a pseudo cherry red spot — the mechanism involves outer retinal disruption (photoreceptors) rather than inner retinal ischemia or ganglion cell swelling
• Resolves spontaneously in most cases; may leave macular pigment changes

Summary Table

Memory Aid

"TSNGG + CRAO + Trauma"

• T = Tay-Sachs
• S = Sandhoff / Silidosis (Mucolipidosis)
• N = Niemann-Pick
• G = GM1 Gangliosidosis
• G = Gaucher's
• CRAO = Central Retinal Artery Occlusion
• Trauma = Berlin's edema

• Kanski's Clinical Ophthalmology, 9th ed. — Retinal vascular disease; Fundus findings in systemic disease
• Khurana — Comprehensive Ophthalmology, 7th ed. — Diseases of retina; Ocular manifestations of systemic diseases
• Datta's Ophthalmology — Retinal conditions; storage disorders
• Harrison's Principles of Internal Medicine, 21st ed. (p. 11857) — Tay-Sachs, Sandhoff, lysosomal storage disorders
• Retinal and Ophthalmic Artery Occlusions (p. 12) — CRAO pathophysiology