ObjectiveTo observe the effect of mild anemia on prognosis of hyperplastic diabetic retinopathy (PDR) treated by pars plana vitrectomy (PPV). MethodsA retrospective case-control study. From January 2021 to December 2022, 147 PDR patients with 147 eyes who received PPV treatment at Shenyang He Eye Hospital were included in the study. There were 147 eyes in 147 cases, 82 eyes in 82 males and 65 eyes in 65 females. Age was 25-79 (53.54±12.74) years old. A hemoglobin (Hb) of 90 to 120 g/L in men and 90 to 110 g/L in women was defined as mild anemia. According to Hb results, the patients were divided into mild anemia group and non-anemia group, with 39 cases (39 eyes) and 108 cases (108 eyes), respectively. The best corrected visual acuity (BCVA) test was performed using the international standard logarithmic visual acuity scale before and after the surgery, which was statistically converted to minimum resolved logarithmic (logMAR) visual acuity. The logMAR BCVA of the affected eye was 0.2-2.5 (1.60±0.62) before surgery. According to whether the BCVA improved by more than 3 lines 6 months after surgery, the affected eyes were divided into BCVA improved by more than 3 lines and BCVA improved by less than 3 lines, 117 eyes and 30 eyes, respectively. The patient's body mass index (BMI), BCVA at 6 months after surgery, and the occurrence of neovascular glaucoma (NVG) and recurrence of vitreous hemorrhage (RVH) were recorded. Independent sample t test was used for comparison between groups. Multivariate logistic regression analysis was performed to analyze the influencing factors of increased BCVA ≥3 rows after surgery. ResultsSix months after surgery, the logMAR BCVA of patients in mild anemia group and non-anemia group were 0.97±0.87 and 0.68±0.63, respectively. BCVA increased ≥3 in 26 (66.7%, 26/39) and 91 (84.3%, 91/108) eyes, respectively. logMAR BCVA (t=2.234) and BCVA increased by ≥3 rows of eyes (χ2=5.460) between the two groups, the differences were statistically significant (P=0.027, 0.019). Logistic regression analysis showed that baseline logMAR BCVA [odds ratio (OR) =4.291, 95% confidence interval (CI) 1.918-9.600, P＜0.001)], BMI (OR=1.248, 95%CI 1.057-1.472, P=0.009), the number of retinal laser photocoagulation during surgery (OR=1.001, 95%CI 1.000-1.002, P=0.038), mild anemia (OR=0.360, 95%CI 0.131-0.993, P=0.048), postoperative NVG (OR=0.156, 95%CI 0.033-0.726, P=0.018) and RVH (OR=0.264, 95%CI 0.086-0.808, P=0.020) were independent factors for BCVA improvement ≥3 lines after PPV. ConclusionsMild anemia has a certain effect on BCVA improvement after PPV of PDR. Mild anemia, post-operative NVG and RVH were independent risk factors for increasing BCVA ≥3 lines after PPV in PDR patients.