Eye diseases represent a significant source of health impairment in humans. Twin studies offer an excellent model to dissect the genetic basis of human diseases. In this review, we discuss the potential advantages of using twin-based studies in investigating the genetics of eye diseases--from heritability estimation to identifying underlying genetic and epigenetic changes. We also discuss some of the notable findings of twin studies exploring the genetics of eye diseases. Finally, we suggest other novel approaches that can be utilized to tap the potential of twin studies to provide a more complete understanding of genetic factors underlying ocular diseases.