IMPG1 encodes a chondroitin sulfate-, heparin-, and hyaluronic acid-binding proteoglycan that serves as a structural component of the interphotoreceptor matrix (IPM), the extracellular space between photoreceptors and retinal pigment epithelium 1. IMPG1 is expressed specifically by rod and cone photoreceptor cells 1 and plays a critical role in IPM organization, photoreceptor development, and nutrient trafficking 2. The protein undergoes SEA domain-dependent proteolysis during maturation, which is essential for normal retinal function 3. IMPG1 functions in a codependent relationship with IMPG2; when IMPG2 is absent, IMPG1 mislocalizes to the subretinal space, causing visual deficits 2. Blocking IMPG1 in developing retinal tissue impairs photoreceptor morphogenesis and IPM formation 4. Mutations in IMPG1 cause two distinct inherited retinal dystrophies: vitelliform macular dystrophy (VMD4) with late-onset moderate vision loss and normal RPE reflectivity on imaging 56, and retinitis pigmentosa (RP91) 6. These disease-associated mutations typically inhibit SEA domain proteolysis, disrupting IMPG1 maturation and localization 3. IMPG1 mutations account for approximately 1.45% of inherited retinal dystrophy cases 6.