After viewing a standardised teaching set (5 known monozygotic and 5 known dizygotic twins), you shall be asked to nominate which twin pairs are identical and which are not.

There are 50 random monozygotic or dizygotic twin pairs. The optic discs can be viewed stereoscopically (for example with the aid of a ScreenVu). For each twin pair you shall be asked to report how certain you are of the zygosity.

Prior to viewing, you will be questioned about which optic disc traits you feel are most inherited.

Before viewing your results (and comparing it to the international panel of experts) you shall be asked about how your decision was reached and questioned about the relative weighting you applied to specific optic disc traits.

• Begin Experiment

Background

Twin pairs were recruited as part of the Twins Eye Study in Tasmania which was approved by the relevant ethical committees of the University of Tasmania as well as the Royal Victorian Eye and Ear Hospital.

Stereoscopic optic disc slide photographs were taken (Nidek fundus camera 3-Dx/F, Nidek, Gamagori, Japan). All identifying information has been removed from each stereoscopic photograph prior to viewing by the optic disc grading team. Zygosity was determined through the typing of a minimum of 8 highly polymorphic short-tandem repeats.