Definition: SNIFR is a condition characterized by a splitting of the retinal layers in a star-like (stellate) pattern around the fovea, the central part of the macula responsible for sharp vision.
Location: The retinoschisis (splitting) occurs specifically in the Henle’s Fiber Layer (HFL), an avascular (no blood vessels) outer retinal layer.
Cause: It is nonhereditary and idiopathic, meaning it has no known genetic basis or clear cause.
Appearance on Imaging:
Optical Coherence Tomography Angiography (OCTA) shows no flow signals in the cystic spaces because the HFL lacks blood vessels.
The stellate pattern is visible due to radiating cystic spaces around the fovea.
Patient Profile: Typically affects older adults (median age ~67 years in the study), often with good visual acuity (e.g., 20/20).
Associated Features: No vitreomacular traction or peripheral retinal involvement is noted; it’s a localized foveal condition.
2. CARPET (Central Anomalous Retinoschisis with mid-Peripheral Traction)
Definition: CARPET is a newly described entity in the article, involving retinoschisis in the central macula (fovea) accompanied by tractional forces in the mid-peripheral retina.
Location:
Central Component: Retinoschisis occurs in the Inner Nuclear Layer (INL), a deeper retinal layer that contains bridging blood vessels between the superficial and deep capillary plexuses.
Mid-Peripheral Component: Evidence of vitreoretinal traction (pulling by the vitreous on the retina) in the mid-periphery, often with peripheral retinoschisis or breaks.
Cause: Likely related to vitreoretinal traction, though the exact mechanism isn’t fully defined; it’s not explicitly hereditary but linked to vitreoretinal interface abnormalities.
Appearance on Imaging:
OCTA reveals flow signals in the cystic spaces of the INL due to the presence of bridging vessels.
Wide-field imaging shows mid-peripheral tractional changes, such as retinal elevation or breaks.
Patient Profile: Seen in younger patients (median age ~47 years in the study) compared to SNIFR, with variable visual acuity depending on severity.
Associated Features: Includes vitreomacular traction or adhesion in some cases, and mid-peripheral findings like retinoschisis or retinal breaks.