Assess whether the time to legal blindness is the same or different between the RHO group and the RPGR group. For simplicity, assume that legal blindness in a particular eye is an absorbing state (i.e., once they become legally blind in an eye, they remain legally blind). Also, do not include eyes that are legally blind at baseline in the analysis, since they have already reached the endpoint. The format of the data set is given in FIELD.DOC?

An important endpoint for RP patients is legal blindness. For visual field, legal blindness is usually defined as <20° diameter of equivalent circular field area in the better eye. The equivalent circular field area for a 20° diameter is πR2 = π(10°)² = 314 degrees squared. For example, ID 156 reached this endpoint at the fifth visit (approximately at 5.06 years of follow-up) in the right eye and at both eyes at the sixth visit (approximately 6 years of follow-up).