ObjectiveTo observe the efficacy and safety of individual dose of intravitreal conbercept (IVC) in the treatment of retinopathy of prematurity (ROP) before type 1 threshold.MethodsA retrospective case study. From January to July, 2019, 23 cases (46 eyes) of children with type 1 pre-threshold ROP were included in the study. Among them, 14 cases (28 eyes) were male and 9 cases (18 eyes) were female. The mean gestational age at birth was 28.06±1.73 weeks. The average birth weight was 1.14±0.19 kg. The mean corrected gestational age was 34.38±1.41 weeks at the time of first intravitreal injection of IVC. The axial length (AL) of children was measured by A-mode ultrasound before IVC for the first time. According to the calculation of AL, the corresponding injection dose range was 14.23-16.19, 16.20-17.57, 17.58-18.63 mm and the injection dose of IVC was 0.015, 0.020, 0.025 ml (including IVC was 0.15, 0.20, 0.25 mg, respectively). The first IVC dose was 0.015 ml. On the first day before IVC and on the first and seventh days after IVC, 2 ml of arterial blood was taken from children, serum vascular endothelial growth factor (VEGF) concentration was detected. The follow-up time after treatment was ≥1 year. After one year of follow-up, the effective rate and recurrence rate of IVC for the first time were tested by χ2 tests. The short-term changes of injection times, injection intervals, retinal vascularization time and serum VEGF concentration in children were tested by t test.ResultsRetinal neovascularization subsided and vascular buckling decreased in all eyes. Iris neovascularization subsided, 1-3 weeks after IVC for the first time. Within one year after the first IVC, 16 eyes underwent IVC twice with or without new blood vessels at the junction of the vascular area. The average corrected gestational age was 40.56±3.81 weeks. The injection dose of IVC was 0.015 ml and 0.020 ml for 2 eyes and 14 eyes, respectively.The mean interval from IVC for the first time was 40.89±8.99 days. Of the 16 eyes who underwent IVC twice, 8 eyes showed neovascularization again in the retinal area with or without blood vessels. The average corrected gestational age was 43.00±1.41 weeks. The injection dose of IVC was 0.020 ml and 0.025 ml for 3 eyes and 5 eyes, respectively. The mean interval of the second IVC was 28.60±6.07 days. The mean interval from the first IVC was 69.20±12.40 days. At the end of follow-up, all eyes were treated effectively (100%, 46/46). The mean time of retinal vascularization was 46.31±3.42 weeks. The average number of injections was 1.52±0.76. On the first day before IVC and on the first and seventh days after IVC, the average serum VEGF concentrations were 111.21±148.71, 25.60±27.71 and 42.99±38.01 pg/ml, respectively. Serum VEGF concentration was significantly lower than that before IVC on the 1st and 7th day after IVC (Z=−4.054, −2.779; P＜0.05). Serum VEGF concentration was higher 7 days after IVC than 1 day after IVC, and the difference was statistically significant (Z=−2.505, P＜0.05). All eyes were not treated by laser photocoagulation or vitrectomy. No eye complications such as lens opacification, endophthalmitis and retinal detachment related to drugs or treatment methods were found in all patients.ConclusionIntravitreal injection of individualized dose of IVC is effective in the treatment of type 1 pre-threshold ROP. Seven days after treatment, serum VEGF concentration of patients’serum decreases.