MFSD8 and retinal degeneration: To address whether the CLN7−/− mutation confers retinal degeneration in the BD macaques, we performed longitudinal optical coherence tomography (OCT) and quantified the thickness of retinal layers in the fovea (central 1 mm), parafovea (1–3 mm eccentricity) and perifovea (3–6 mm eccentricity) in BD6 compared to age-matched CLN7+/+ controls (Fig. 3A).