Objective: To estimate the incidence and severity rates of retinopathy of prematurity (ROP) at Songklanagarind Hospital.

Methods: A prospective descriptive study was conducted of premature infants born weighing 2,000g or less at Songklanagarind Hospital between the 1st October 2004 and the 30th September 2006. During serial eye examinations, the incidence, severity and timing of ROP were recorded. ROP was categorized according to International Classification for Retinopathy of Prematurity.

Results: Of 126 premature infants, 20 (15.9%) developed ROP. The average (± SD) birth weight and gestational age were 1,158± 365 g and 29± 2.4 weeks, respectively. The incidence of ROP and pre-threshold ROP was 31% and 22% among infants of  ≤  1,500 g. The incidence of ROP and pre-threshold ROP among infants of  ≤  1,250 g was 40% and 33.3%. The onset of ROP was 33-38 weeks of postmenstrual age or 4-10 weeks after birth. Eight of 20 infants progressed to a high-risk pre-threshold stage of ROP and required treatment. No stage four or stage five or zone 1 ROP was observed.

Conclusions: The incidence and time of ROP onset at Songkhlanagarind Hospital were similar to those reported in several other studies but the incidence of pre-threshold ROP was high. The ROP screening in premature infants with birth weight  ≤  1,500 g or  ≤  32 weeks gestational age is recommended and should begin at 32 weeks of postmenstrual age or four weeks after birth.