**Background:** Paramacular choriocapillaris atrophy is a rare, poorly understood choroidal dystrophy characterized by atrophy of the choriocapillaris in the paramacular region, often with foveal sparing. Recent histology suggests that pathologies categorized as choroidal dystrophies are primarily caused by alterations at the level of the retinal pigment epithelium (RPE). The etiopathogenetic mechanism of foveal sparing remains unresolved, but a disease-independent mechanism allowing survival of foveal cones is hypothesized. This study presents a case of paramacular choriocapillaris atrophy with foveal sparing and multimodal imaging findings.
**Methods:** A 73-year-old female patient presented with impaired vision and photophobia in both eyes during a routine ophthalmological examination. She denied visual field defects and night blindness. Medical history included type II diabetes and arterial hypertension for 5 years; her deceased sister was legally blind at age 60. A complete ophthalmological examination was performed, including best-corrected visual acuity (BCVA) using ETDRS charts, applanation tonometry, and biomicroscopy of anterior and posterior segments. Diagnostic tests included fundus autofluorescence (FAF), fluorescein angiography (FA), optical coherence tomography with angiography (OCT/OCTA), computerized perimetry, and electroretinography (ERG). Immunological and infectious histories were negative. Genetic testing was performed at BluePrints Genetic Laboratory in Finland using a panel of 314 genes for retinal dystrophies and 37 mitochondrial genes.
**Key Results:** Right eye BCVA was 0.7, left eye BCVA was 0.6. Anterior biomicroscopy revealed incipient corticonuclear cataracts; intraocular pressure was normal. Fundus examination in mydriasis showed an optic disc with clear margins, a fovea with spared structure, and a bilateral, concentric zone of grayish atrophy within the temporal arcades with visible choroidal vessels. No retinal vessel attenuation, pale papillae, or bone spicule pigmentation were detected. FAF demonstrated a zone of hypoautofluorescence corresponding to the atrophic area, while the fovea showed hyperautofluorescence in both eyes. Numerous hyper/hypoautofluorescences were seen at the boundary of preserved and atrophic chorioretina, most intense at the optic disc and upper temporal arcade. Early-phase FA showed lack of filling of retinal vasculature and choriocapillaris causing a hypofluorescent zone, with hyperfluorescence surrounding the fovea and margins of the atrophic area; later phase showed leakage from preserved choriocapillaris. A 'window defect' was observed in the peripapillary area and along lesion borders, especially in the upper temporal arcade region. OCT revealed normal RNFL thickness for age, parafoveal atrophy of outer retinal layers, and sparing of the external limiting membrane (ELM), ellipsoid zone, and RPE in the fovea. Circular intraretinal edema was detected at the boundary of the fovea and parafovea. OCTA showed reduced retinal capillary plexus and choriocapillary layer. Visual field testing indicated relative and absolute central and paracentral scotomas. ERG showed diffuse photoreceptor dysfunction and reduced oscillatory potentials with delayed implicit time, despite an apparently intact fovea. Genetic testing identified heterozygous variants of uncertain significance in BEST1 (c.1681A>G, p.(Thr561Ala)), RP1L1 (c.2107C>G, p.(Arg703Gly)), and TTLL5 (c.3425C>T, p.(Thr1142Ile)). No likely pathogenic variants were found.
**Clinical Implications:** This case highlights the diagnostic challenge of paramacular choriocapillaris atrophy, which can mimic other choroidal/retinal dystrophies such as central areolar choroidal dystrophy (CACD), Stargardt disease type I (STGD1), and pseudo-Stargardt pattern dystrophy (PSPD). The absence of a clear genetic etiology supports the diagnosis of paramacular choriocapillaris atrophy. The foveal-sparing phenotype is clinically significant because it preserves central visual acuity, which has implications for prognosis and eligibility for future therapeutic trials, such as gene therapy. The presence of circular intraretinal edema at the fovea-parafovea boundary may indicate disease progression toward the fovea. Understanding the natural history of foveal sparing is crucial as new treatments (e.g., gene replacement) are being evaluated. Long-term follow-up with multimodal imaging (FAF, SD-OCT, OCTA) and functional tests (visual fields, ERG) is recommended to monitor disease progression and identify prognostic markers.