In terms of visual acuity, the progression of both dominantly inherited macular dystrophies is quite different. This is not reflected in the amplitudes of the b-waves in the Ganzfeld ERGs, which decrease normally for both entities. Implicit times of the cone-b waves were more markedly prolonged in ML compared with ZMD. In-depth longitudinal documentation of the natural course of those dominantly inherited macular diseases should facilitate patient counseling.

Sebaceous cell carcinoma is a rare entity. Depending on its histological differentiation it can be highly malignant. Infiltrative, and can metastasize. The mortality may reach 30% if low differentiation is present. As illustrated in the present case, the lesion may masquerade a chalazion. Therefore, in case of atypical lesion of the eyelid region complete surgical removal followed by a histopathological examination should be performed.

Patient history and clinical testing raised the suspicion of a hereditary macular dystrophy. By means of Ganzfeld and multifocal electroretinography the course of the disease could be observed. However, definite diagnosis could only be established by genetic identification.