Abstract Purpose: To assess the association between retinal nerve fiber layer (RNFL) thickness and visual acuity in a family from Siracusa (Sicily) with autosomal dominant optic atrophy (ADOA) due to a heterozygous c.869G>A OPA1 mutation. Methods: Affected family members underwent complete neuro-ophthalmological evaluation, including visual acuity testing, colour vision testing, tonometry, visual field testing, colour fundus photography, pattern visual-evoked potential (PVEP) testing, and pattern electroretinography (PERG). Patients and age-matched control subjects were scanned by spectral-domain optical coherence tomography (SD-OCT) to assess circumpapillary RNFL thickness. Results: All patients showed the characteristic optic disc pallor and central scotomas in the visual field. PVEP testing and PERG also showed alterations consistent with ADOA. The average circumpapillary RNFL thickness was thinner in ADOA patients than in control subjects (60.87 ± 6.58µm and 108.13 ± 6.53µm, respectively; p = 0.0001). The visual acuity in patients with ADOA correlated significantly with the circumpapillary average RNFL thickness (r = -0.845, p = 0.008). Conclusions: OCT-measured peripapillary RNFL thickness is reduced in ADOA patients compared with healthy subjects and correlates significantly with visual acuity in patients with ADOA. The photoreceptor layers are morphologically unaffected.