This study was performed to investigate the efficacy of the treat-and-extend regimen using aflibercept for treating diabetic macular oedema (DME). This prospective, multicentre, interventional, single-arm, 104-week clinical trial included 48 patients with DME visual impairment. The patients' eyes received five consecutive intravitreal injections (2 mg aflibercept) every four weeks with two-week adjustments based on central subfield macular thickness (CSMT) changes. Injections were deferred when CSMT was stable. The number of injections, best-corrected visual acuity (BCVA), CSMT, and diabetic retinopathy severity scale scores were analysed. Compared to baseline, BCVA improved by + 9.1 letters at 52 weeks and was maintained with + 9.4-letter gain at 104 weeks (P < 0.001). Between baseline and 104 weeks, CSMT decreased from 489 to 298 μm (P < 0.001) and eyes with vision ≥ 20/40 increased from 17.4 to 43.5% (P = 0.007). The mean number of injections decreased from 8.5 in year one to 3.9 in year two. The injection interval was extended to ≥ 12 weeks in 56.5% of patients. The treat-and-extend regimen of aflibercept in DME showed 2-year efficacy comparable to that of fixed dosing regimens. The flexible dosing of this regimen reduced the number of injections in year two while maintaining efficacy.