Background: Optical coherence tomography (OCT) has enabled objective measurement of macular thickness in diabetic and branch retinal vein occlusion (BRVO) associated macular edema (ME). Recent advances in OCT with higher resolution enabled segmentation of the individual retinal layers, quantification of the thickness of retinal layers and qualitative evaluation of lesions in individual layers.
Objectives: Studying the changes of parafoveal outer plexiform-inner nuclear layers thickness (OPINLT) and changes of parafoveal ganglion cell layer (GCL) thickness at the thickest parafoveal point after single injection of ranibizumab in patients with ME caused by diabetic retinopathy (DR) or BRVO.
Patients and Methods: The present study included 36 eyes of 30 patients (21 males and 9 females, mean age was 52.87±7.56 years old). All patients had single intravitreal injection of 0.5 mg (0.05 mL of 10 mg/mL) of ranibizumab (bilaterally in 6 patients and unilaterally in 24 patients) for treatment of ME caused by DR or BRVO. OCT images were taken preoperatively, and one month after intravitreal ranibizumab injection for all participants using spectral OCT SLO combination imaging system. Foveal thickness was measured. Parafoveal measurements were obtained at the thickest parafoveal point (1200 μm from foveal center) in the superior, nasal, inferior and temporal parafoveal sectors. Parafoveal measurements included parafoveal thickness, OPINLT, isolated GCL thickness and GCL-IPL thickness (GCIPLT).
Results: The study included 30 eyes with diabetic ME caused by moderate to severe non-proliferative diabetic retinopathy (NPDR) or early proliferative diabetic retinopathy (PDR); 17 eyes with cystoid macular edema (CME) and 13 eyes with diffuse macular edema (DME), in addition to 6 eyes with CME due to BRVO. As regards changes of participants' best corrected visual acuity (BCVA) and foveal thickness, there was a statistically significant improvement in BCVA mean value from 0.36±0.19 preoperatively to be 0.7±0.27 one month after injection, and statistically significant decrease in mean foveal thickness from 342.64±110.04 μm preoperatively to be 249.55±68.90 μm one month after injection. As regards total parafoveal thickness, there was statistically significant decrease in mean parafoveal thickness of the participants in each parafoveal sector after injection and the postoperative parafoveal thickness mean values were higher in the superior and nasal sectors. As regards detailed segmented parafoveal measurements, there were statistically significant decrease in both OPINLT and GCIPLT mean values in all parafoveal sectors after injection. By further analysis of isolated GCL, the present study results have shown that the changes of GCL mean thickness in each parafoveal sector were not statistically significant. In addition, preoperative and postoperative GCL thickness mean values were higher in the superior and nasal sectors.
Conclusion: OPINLT and GCIPLT decreased significantly at the thickest point of parafoveal area after single intravitreal ranibizumab injection for treatment of ME caused by DR or BRVO, while isolated GCL thickness did not change significantly after injection. It was proven also that GCL which contains the cell bodies of ganglion cells (GCs) was proven to be the least affected layer by ME.