The authors evaluated retrospectivel the examination protocols of 208 children (400 eyes)treated by cryocoagulation on account of active retinopathy of prema- ture infants (ROP).The objective was to assess the optimal timing for the onset of examination to record in time the threshold stages of ROP in children with different grades of maturity.The baseline point was the finding that before the 5th postnatal (pnt)and 31st postconception week (pcw)the threshold stage was not diagnosed in any child of the group.The highest incidence of threshold stages in all children was between the 36th and 37th postconception week.The first examination made between the 5th-6th postnatal or at first during the 31st postconception week is sufficient to cover initial threshold stages of ROP in children with different birth weights.Screening based on combination of the postnatal and postconception age is more accurate than evaluation by one criterion.Premature examinations are misleading and not valid for screening.

        Key words: retinopathy of the premature,threshold stage of ROP,screening, postnatal and postconception age