The knowledge of the genetic basis of many eye diseases is constantly increasing. Besides retinal degeneration, developmental defects of the anterior segment, cataracts, and the development of the basic structure are often associated with genetic defects. Moreover, a lot of genetic syndromes involve eye abnormalities. The impact of genetics has become more and more evident in ophthalmological practice. Although genetic counselling is usually carried out by human geneticists, the increasing availability of therapeutic options requires ophthalmologists to have some basic knowledge of the genetic causes and how to identify them. The first step in this regard is to recognise potential genetic eye disorders and to initiate an adequate genetic analysis to confirm the diagnosis. This review discusses possible and necessary investigations within the patient's family facing ophthalmologists after the genetic cause of an eye disease has been identified.