GSTM1 and retinopathy of prematurity: PRBC - Packed red blood cell; ROP - Retinopathy of prematurity; BPD - Bronchopulmonary dysplasia; Hb - Hemoglobin; RDS - Respiratory distress syndrome; TLC - Total leucocyte count; ALC: Absolute lymphocyte count; ANC - Absolute neutrophil count; AMC - Absolute  monocyte count