Vitrectomy for diabetic macular edema: Effect of glycemic control (HbA)_1c), renal function (creatinine) and other local factors

Aims: To determine the effect of preoperative factors on the foveal thickness following vitrectomy for diabetic macular edema. Methods: Fifty-eight eyes of 47 patients underwent vitrectomy for diabetic macular edema. In all eyes, no clear, visible vitreomacular traction was present. Twelve eyes were pseudophakic before vitrectomy, and 31 eyes underwent concurrent phacoemulsification and intraocular lens (IOL) implantation. Multiple logistic regression analysis was used to assess the independent effect of age, history of photocoagulation, diabetic retinopathy status, preoperative posterior vitreous detachment, HbA_1c and serum creatinine levels within 2 weeks before surgery, lens status after surgery and follow-up period on the foveal thickness determined by optical coherence tomography. Results: The median pre-operative visual acuity was 20/100 (range from 20/500 to 20/20), and the median postoperative visual acuity was 20/70 (range from 20/500 to 20/13). The preoperative visual acuity (logarithm of minimal angle of resolution; logMAR) was 0.73 ± 0.36 (mean ± SD; 20/107 Snellen acuity), and the mean postoperative logMAR visual acuity was 0.60 ± 0.39 (20/80), which was significantly better than the mean preoperative value (Wilcoxon signed rank test, p = 0.011). The mean ±n SD of preoperative foveal thickness was 475.9 ± 172.5 μm, and the mean postoperative foveal thickness was 277.3 ± 171.9 μm. The mean postoperative foveal thickness was significantly thinner than the preoperative thickness (Student's paired t test, p < 0.0001). Multiple logistic regression analysis showed that a preoperative low HbA_1c and postoperative pseudophakia were independently associated with the decrease in foveal thickness (p = 0.01, p = 0.04, respectively). Conclusions: The greater reduction in foveal thickness in eyes with an IOL probably resulted from a relatively larger amount of vitreous being removed during the vitrectomy. Because the decrease in foveal thickness may be related to the preoperative glycemic control and the amount of vitreous, these factors should be considered in the planning for vitrectomy.