Determinants of retinal and choriocapillaris microvascular alterations in pediatric β-thalassemia: an OCTA study

To evaluate retinal and choriocapillaris microvascular changes observed using optical coherence tomography angiography (OCTA) in pediatric patients with β-thalassemia and to identify hematologic and clinical predictors of these changes.

This cross-sectional observational study included 120 eyes of 120 children (< 18 years): 40 with thalassemia major, 40 with thalassemia intermedia, and 40 age-matched controls. All participants received a thorough ophthalmic examination and OCTA imaging (6 × 6 mm scans) to assess vessel density (VD) in the superficial capillary plexus (SCP), deep capillary plexus (DCP), and choriocapillaris (CC), as well as foveal avascular zone (FAZ) parameters. Clinical data included hemoglobin level, serum ferritin, transfusion history, hydroxyurea use, and splenomegaly. Correlation and regression analyses were conducted to determine predictive factors of the associated OCTA changes.

In both thalassemia major and intermedia, the area and perimeter of the FAZ was significantly greater as compared with controls (p < 0.01). SCP whole VD was significantly lower in thalassemia intermedia compared with controls (p = 0.023), while DCP whole VD was significantly lower in both thalassemia groups (p < 0.001). Choriocapillaris flow was also significantly reduced in thalassemia patients (p < 0.001). Serum ferritin levels and blood transfusion rate showed limited and inconsistent correlations with OCTA parameters. In contrast, hemoglobin level demonstrated significant positive correlations with VD across multiple SCP and DCP regions. Multivariable regression analysis indicated that hemoglobin was the only independent predictor of superficial and deep whole VD (p = 0.015 and p = 0.002, respectively).

Children with β-thalassemia exhibit significant subclinical retinal and choriocapillaris microvascular alterations detectable by OCTA. Hemoglobin level, rather than iron indices, is the strongest determinant of retinal vascular density, suggesting that chronic anemia-related hypoxia plays a central role in retinal microvascular compromise in pediatric β-thalassemia.