Stellate Multiform Amelanotic Choroidopathy (SMACH): Clinical Spectrum, Multimodal Imaging Diagnosis, and Management

The document traces SMACH to observations reported by Van Dijk and Boon in 2021, initially termed Serous Maculopathy due to Aspecific CHoroidopathy. Multicenter imaging work in 2023 found that SRF was absent in 41%–44% of eyes and could fluctuate spontaneously. A yellow-orange, non-pigmented choroidal lesion with radial digitiform projections was reported across affected eyes, prompting the updated name Stellate Multiform Amelanotic Choroidopathy while retaining the acronym SMACH. The condition is described as benign, non-progressive, unilateral, and centered on the inner choroidal stroma and RPE–Bruch’s membrane complex, without true macular neovascularization (MNV) or typical pachychoroid features.

• Age: Reported cohort mean 28 ± 19 years, range 7–68 years, with a predilection for adolescents and young adults but cases across a wide age range.
• Sex and laterality: A balanced sex distribution is reported in a primary cohort; the document describes SMACH as strictly unilateral, with no bilateral cases documented in the cited literature.
• Symptoms: Approximately 39%–44% are asymptomatic. Others may report metamorphopsia, gradual central visual reduction, distorted vision, or a paracentral scotoma.
• Visual acuity: Baseline acuity is generally preserved, with a reported mean BCVA near 20/25 and a range of 20/20 to 20/200; most patients remain stable over long follow-up.
• Fundus appearance: Yellow-orange amelanotic, multiform or dendriform lesion with sharp or subtle radial digitiform projections; overlying RPE may show stippling, hypo- or hyperpigmentation.
• Location: Approximately 67% subfoveal, 28% parafoveal, and 5% nasal extramacular with foveal sparing.

• Cross-sectional OCT: Inner choroidal hyperreflective fibrous-like change, mean lesion thickness 125 ± 90 µm (range 52–315 µm), and anterior protrusion/distortion of the RPE–Bruch’s membrane complex reported in 100% of cases.
• Outer retinal findings: EZ/IZ attenuation 61%; outer nuclear layer thinning 44%; external limiting membrane alteration 22%; foveal optical gaps 11%; focal staphyloma-like protrusions 11%. SRF is present in 56%–59% and absent in 41%–44% at presentation.
• En face OCT and NIR: Dense, bright, stellate lesions with radiating digitiform projections; the structural extent may extend beyond the visible fundus lesion and can remain apparent without SRF.
• OCT angiography (OCT-A): No true MNV is expected in typical SMACH. The document notes that non-neovascular intralesional flow may be seen and should not automatically be mistaken for active neovascularization.
• Fluorescein angiography (FA): Granular hypo-/hyperfluorescence, late staining, and uncommon focal RPE leakage are described.
• ICGA: Described patterns include classic early and persistent hypofluorescence, a focal leakage variant (reported as 17%), and an encircled pattern. The document states that diffuse choroidal hyperpermeability is absent in typical SMACH.
• Fundus autofluorescence (FAF): Reported phenotypes include normal FAF (33%), speckled hypoautofluorescence (39%), and hyperautofluorescent rims associated with acquired vitelliform material (17%).

The document highlights the risk of confusing SMACH with central serous chorioretinopathy (CSC), placoid or infectious chorioretinitis, idiopathic MNV, amelanotic nevus or melanoma, choroidal osteoma, metastasis, hemangioma, lymphoma, focal scleral nodule, and inherited retinal dystrophies. Features supporting SMACH include inner-choroid confinement, stellate digitiform projections on en face OCT/NIR, absence of typical pachyvessels or diffuse ICGA hyperpermeability, absence of true MNV, lack of deep optical shadowing or calcified bone lamellae, and long-term structural stability. The source gives clinical examples in which correct recognition prevented continued antibiotics or anti-VEGF injections after lack of response.

The precise cause remains under investigation. The document discusses three proposed, intersecting models: a localized congenital developmental anomaly of the inner choroid; focal hydrostatic pressure changes and fluid transudation across an altered RPE–Bruch’s membrane barrier, potentially explaining why some eyes develop SRF and others do not; and compensatory retinal mechanisms that may help preserve visual function despite chronic fluid or photoreceptor changes. Long-term observations are described as showing stable lesion dimensions, no malignant transformation, and spontaneous, indolent SRF fluctuations. Mean BCVA is generally reported as stable near 20/25, although rare long-term decline associated with outer retinal atrophy and ONL thinning is noted.

• Typical SMACH: Conservative clinical observation is described as the standard approach for most cases.
• Avoid routine overtreatment: The document reports that anti-VEGF injections and standard PDT have not benefited typical chronic-SRF cases in the cited series. It cautions against unnecessary anti-VEGF, systemic corticosteroids, topical NSAIDs, and empirical antibiotics when the diagnosis is SMACH.
• Exceptional focal-leakage variant: For persistent symptomatic SRF with late-phase focal punctate leakage on ICGA, targeted full-dose PDT directed to the leakage site may be considered. The source describes a reported case with rapid, complete, sustained SRF resolution and outer retinal restoration.

• Use en face structural OCT and NIR when assessing a non-pigmented inner choroidal lesion; the stellate digitiform pattern is highlighted as the key structural hallmark.
• Do not exclude SMACH because SRF is absent; fluid may be absent or fluctuate spontaneously.
• Differentiate intralesional flow from true MNV and evaluate for the absence of pachyvessels, diffuse hyperpermeability, active inflammation, deep mass features, or calcification.
• Explain the generally benign, non-progressive course while recognizing that rare long-term visual decline has been reported.

SMACH is presented as a distinctive inner choroidal disorder best recognized through the combination of clinical examination, en face OCT, cross-sectional OCT, and NIR, with angiography used to clarify selected diagnostic patterns. Accurate diagnosis helps avoid unnecessary invasive or pharmacologic treatment. Observation is the usual approach, while targeted PDT is discussed for the uncommon ICGA focal-leakage variant with persistent symptomatic SRF. These statements reflect the uploaded review’s synthesis of the cited literature.

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