setting: University-based practice. patient: A 48-year old Jewish Italian male with clinically, functionally, and molecularly confirmed ESCS, attributable to homozygosity for the R311Q mutation in the NR2E3 gene, presented with sudden visual acuity (VA) loss (20/200) and metamorphopsia in the left eye resulting from acute, late-onset, asymmetric macular RS. intervention: Open-label, off-label treatment with the oral CAI acetazolamide. main outcome measure(s): Best-corrected VA, retinal thickness, and retinal microanatomy, assessed by Stratus optical coherence tomography (OCT) criteria.