Participants and examination
This study consists of the medical records of 131 VLBW infants admitted in NICU. The World Health Organization (WHO) defines VLBW, a subgroup of low birth weight, as the birth weight between 1000 g and 1500 g.(12) Babies were born with a BW of ≤1500 g and/or a GA of ≤30 weeks and those with available ROP examination records and data of weights at the sixth weeks of life were included in the study.
Infants with unstable clinical course preventing ROP examination were excluded from the study. The initial screening for ROP was performed in the fourth weeks of postnatal life. Time intervals between examinations were repeated weekly or bi-weekly based on the guidelines described by the American Academy of Pediatrics, the American Academy of Ophthalmology, and the American Association for Pediatric Ophthalmology and Strabismus.(13) After pupillary dilation with 2.5% phenylephrine and 0.5% tropicamide eye drops, eye examinations assisted with binocular indirect ophthalmoscopy, 28-diopter lens and scleral indentation with an eye speculum were performed by the same ophthalmologist (SG).
The retinal findings indicating the stage of disease, location by zone and presence of plus disease were classified regarding to the current International Classification of ROP.(14) In accordance with the international classification, patients were divided into three different groups as follows; the absence of any stage of ROP (no-ROP), the presence of any stage of ROP without needing any treatment (Type-2 ROP) and severe ROP that indicates the need for an urgent intervention via laser photocoagulation or intravitreal injections (Type-1 ROP).