Zada M, Cornish EE, Fraser CL, et al. - Given that X‐linked retinitis pigmentosa (XLRP) accounts for a significant proportion of certifiable blindness in adults of working age, researchers sought to synthesize the best available evidence on the natural history of disease progression and to identify the best existing clinical biomarkers for disease progression monitoring, which will be critical in planned gene therapy trials for this condition. The inclusion requirements were met by a total of 17 reports. As the most helpful biomarkers of excellent interocular symmetry, reproducibility and functional correlation, the evidence suggested the ellipsoid zone (EZ) width on OCT and outer ring area (ORA) on FAF. XLRP progresses at a rate of 4 to 19% per year using different clinical biomarkers. The width of the EZ and ORA are the most robust biomarkers with the ability to be used in studies where one eye serves the other as a control.