Foveal Microstructure Analysis in Eyes with Diabetic Macular Edema Treated with Vitrectomy.

INTRODUCTION

The purpose of this study was to evaluate baseline and postoperative factors affecting outcomes after vitrectomy for diabetic macular edema (DME) using optical coherence tomography (OCT).

METHODS

Vitrectomy combined with inner limiting membrane (ILM) peeling and additional laser photocoagulation therapy was performed on 36 eyes of 30 DME patients. Evaluations included the logarithm of the minimal angle of resolution (logMAR), best-corrected visual acuity (BCVA) and OCT parameters at baseline and 1, 3, 6, and 12 months postoperatively. Correlations between OCT parameters and BCVA were assessed at each follow-up visit. Correlations among postoperative BCVA and preoperative BCVA, foveal macular thickness (FMT), outer foveal thickness (OFT), and photoreceptor outer segment (PROS) length were evaluated using multiple regression analysis.

RESULTS

BCVA significantly improved from 0.50 ± 0.25 to 0.34 ± 0.26 at 12 months postoperatively (P < 0.001). Mean FMT improved significantly from 526.4 ± 120.4 to 384.6 ± 120.5 at 1 month, 325.2 ± 100.3 at 3 months, 304.1 ± 102.5 at 6 months and 274.2 ± 86.6 μm at 12 months postoperatively (P < 0.001, respectively). OFT 1 month after surgery was significantly decreased 46.5 ± 14.7-40.2 ± 14.4 μm (P = 0.017), although at 3, 6, and 12 months it did not differ from the baseline value. PROS length 1 month after surgery significantly decreased from 31.7 ± 6.9-28.8 ± 6.8 μm (P = 0.015) and that at 3 months and 6 months recovered to the baseline value. PROS length 12 months after surgery was significantly increased to 34.3 ± 7.2 μm from baseline (P = 0.023). Mean FMT was not correlated with BCVA at any time point. Mean OFT and PROS length at 3, 6, and 12 months were correlated with BCVA. In multiple regression analysis, PROS length had the greatest effect on VA 12 months postoperatively (P = 0.0262, standard regression coefficient = -0.366).

CONCLUSION

Current surgery helps DME patients to maintain VA and foveal structures. The results suggest that PROS length predicts visual outcome in DME patients following vitrectomy with ILM peeling and additional laser photocoagulation.