Patients who had been diagnosed with DME and had received IVR or IVA using the TAE regimen for more than 24 months without any additional treatment were studied. All of the patients were examined in the Department of Ophthalmology of the Mie University Hospital between April 2014 to November 2018. The procedures used in this study were approved by the Institutional Ethics Review Board of the Mie University Hospital (#702), and the study was registered at http://www.umin.ac.jp (UMIN ID 000033728). The procedures adhered to the tenets of the Declaration of Helsinki and a signed informed consent was obtained from all patients.
Each patient had a comprehensive ophthalmological examination including measurements of the best-corrected visual acuity (BCVA) and intraocular pressure, examination of the anterior segment by slit-lamp biomicroscopy, examination of the fundus by indirect ophthalmoscopy, and the macular structure by spectral-domain optical coherence tomography (SD-OCT).
The inclusion criteria were; presence of DME, age at least 20 years, and BCVA pretreatment of 20/320 or better. The diagnosis of DME was made by the clinical findings, fluorescein angiography, and a central retina thickness (CRT) greater than 250 μm in the SD-OCT images. The exclusion criteria were; prior ocular surgery within 6 months, macular laser photocoagulation, and intravitreal or sub-tenon injections of steroids within 3 months of the beginning of this study. In addition, eyes with ocular inflammation, drusen, severe proliferative diabetic retinopathy, retinal hemorrhage which involved the intra- or subfoveal spaces, an epiretinal membrane, any history of pars plana vitrectomy, glaucoma, and media opacities that significantly affected the BCVA were excluded. Patients with uncontrolled systemic medical conditions or history of thromboembolic events were also excluded. Diabetes control was evaluated by the HbA1c levels (normal range:4.6–6.2%), and renal dysfunction was evaluated by the estimated glomerular filtration rate (eGFR; normal range: 60–120 ml/min/m2).
Intravitreal anti-VEGF injections
Intravitreal anti-VEGF injections were performed under local subconjunctival or topical anesthesia. Each patient received 0.5 mg of ranibizumab (IVR group) or 2 mg of aflibercept (IVA group) intravitreally with a 30-gauge needle that was inserted 4 mm posterior to the corneal limbus under sterile conditions. All patients received topical levofloxacin hydrate, (1.5% Cravit ophthalmic solution) for 1 week after the injection.
All patients were given 3 consecutive monthly injections, the loading phase, as described in detail [24, 27], and they continued the therapies with IVR or IVA injections with a modified TAE regimen.
Modified-TAE regimen for DME
In the maintenance phase, the follow-up injection intervals were applied according to a modified-TAE regimen as described in detail [24], and the initial treatment interval was set at 8 weeks. The injection interval was extended by 2 weeks if the CRT was <350 μm at 2 consecutive examinations, and the injection interval was shortened by 2 weeks if the CRT was >350 μm or increased by more than 20% of the baseline value.
Measurements of best-corrected visual acuity (BCVA)
The BCVA was measured with a Landolt chart at every visit. The decimal BCVA was converted to the logarithm of the minimum angle of resolution (logMAR) units for the statistical analyses.
Optical coherence tomography (OCT)
The measurements of the CRT were made on the images recorded by a Heidelberg Spectralis OCT instrument (Heidelberg Engineering Inc, Heidelberg, Germany). For qualitative and quantitative analyses of the OCT images, the fast macula protocol was used to obtain the images with an automatic real time mean value of 9 which acquired 25 horizontal lines consisting of 1024 A-scans per line. The CRT was defined as the thickness between the internal limiting membrane and the retinal pigment epithelium at the fovea, and the value was automatically calculated from the center subfield of the macular thickness map using the bundled software.
Statistical Analyses
The results are presented as the means ± standard deviations (SDs). Paired t tests were used to determine the significance of the differences between corresponding pairs in the two groups. Two-way repeated measures ANOVA and post-hoc t tests with Bonferroni’s corrections were used to determine the significance of the changes in the BCVA and CRT. Two-tailed P values of <0.05 were significant. The statistical evaluations were performed by Statcel 4 Statistical Program (Statcel; OMC, Saitama, Japan).