A case of maternally inherited diabetes and deafness (MIDD)-associated macular pattern dystrophy with a 15-year follow-up is reported. On initial examination at age 37, visual acuity was normal, but chorioretinal atrophy at the posterior pole was already present in both eyes. At age 52, visual acuity remained normal in the right eye and was only slightly decreased in the left eye despite notable extension of the areas of chorioretinal atrophy in that eye. No evidence of diabetic retinopathy was present at any time. This case shows that visual acuity can remain stable in the long term despite extensive lesions of macular pattern dystrophy.