Axial Length as a Factor Associated With Visual Outcome After Vitrectomy for Diabetic Macular Edema

PURPOSE. To investigate whether axial length predicts visual acuity outcome after vitrectomy for diffuse macular edema secondary to diabetic retinopathy. METHODS. Fifty-one eyes of 41 patients with diabetic macular edema (DME) who underwent vitrectomy were reviewed retrospectively. Clinical data, including axial length measured by partial coherence interferometry, postoperative best-corrected visual acuity (BCVA), and postoperative status of integrity of the photoreceptor layer observed by optical coherence tomography, were recorded. The relationship between axial length and postoperative BCVA or visibility of the junction between the inner and outer segment (IS/OS) line at 12 months after surgery were analyzed. Logistic regression analyses were performed to examine predictors related to postoperative BCVA. RESULTS. Median BCVA improved significantly (P < 0.0001) after surgery (0.4 logMAR units; range, 0-1.5) compared to baseline (0.69 logMAR units; range, 0.22-1.22). Median axial length was significantly longer (P = 0.017) when postoperative BCVA was below 0.4 logMAR units (23.51 mm; range, 22.30-26.10) compared to over 0.4 logMAR units (23.02 mm; range, 22.10-24.65). A significant negative correlation was observed between postoperative logMAR and axial length (n = 51, rs = -0.35, P = 0.012). Median axial length was significantly longer (P = 0.039) in eyes with visible IS/OS line (23.54 mm; range, 22.39-26.10) than in those without visible IS/OS line (23.02 mm; range, 22.13-24.65) at 12 months after surgery. Multivariate logistic regression analysis showed that short axial length (odds ratio: 0.3, P = 0.009) increased the risk of poor visual outcome after surgery. CONCLUSIONS. Longer axial length predicts better postoperative BCVA after vitrectomy for diffuse macular edema secondary to diabetic retinopathy.