CRISPR as a therapeutic tool for inherited retinal degenerations: Advances, challenges, and future directions.

Inherited retinal diseases (IRDs) are a genetically diverse group of disorders characterized by progressive photoreceptor degeneration, leading to vision loss and blindness. With over 320 associated genes and significant phenotypic variability, effective treatment remains challenging. Recent advances in genome editing, particularly CRISPR/Cas-based technologies, have revolutionized therapeutic approaches by enabling precise and customizable DNA and RNA editing. This review explores the application of various CRISPR strategies-such as gene knockout via non-homologous end joining (NHEJ), exon skipping using dual-sgRNAs, homology-directed repair (HDR), base editing (BE), prime editing (PE), RNA editing with Cas13, and epigenetic modulation through CRISPRa/i-in preclinical models of IRDs. Emphasis is placed on allele-specific targeting, gene-agnostic approaches, and mutation-independent strategies to address dominant and recessive forms of disease. We also highlight recent clinical milestones, including the first human trial using CRISPR gene editing for CEP290-associated Leber congenital amaurosis. Finally, we discuss critical challenges, including delivery constraints, immune responses, and off-target effects, along with emerging solutions such as engineered Cas variants, split-intein systems, and advanced off-target detection methods. Together, these advances underscore the transformative potential of CRISPR technologies in treating IRDs and lay the foundation for future clinical translation.