Optical coherence tomography and vessel diameter changes after intravitreal bevacizumab in diabetic macular oedema

PURPOSE: To assess the effect of intravitreal bevacizumab on diabetic macular oedema (DMO) and retinal vessel calibres.

METHODS: We performed a consecutive case series study in which 10 consecutive eyes with diffuse DMO, two of which had not previously been treated, received an intravitreal injection of bevacizumab 1 mg, which was followed by two more injections at 6-week intervals. Fundus photography and optical coherence tomography (OCT) were carried out at baseline immediately before injection and at 1, 2.5 and 4 months after the first injection. Outcome measures were best corrected visual acuity (BCVA) in Early Treatment Diabetic Retinopathy Study letters, macular volume, foveal subfield thickness and vessel diameter measurement.

RESULTS: Intravitreal administration of bevacizumab was followed by a mean increase in BCVA of 7.3 +/- 17 (mean +/- standard deviation) letters between baseline and month 4, which was 1 month after the last injection (p < 0.0001). This was accompanied by a reduction in mean macular volume from 9.90 +/- 1.9 mm(3) to 8.96 +/- 2.4 mm(3) (p = 0.002) and in foveal subfield thickness from 447 +/- 117 microm to 388 +/- 117 microm (p = 0.03). Two eyes with early proliferative diabetic retinopathy lost all signs of proliferation without any evidence of fibrosis. Although there was a trend towards vasoconstriction, the changes in vessel diameters (arteries and veins) after 4 months of intravitreal Avastin injection were not statistically significant (p = 0.9 and p = 0.17, respectively). Foveal thickness in non-injected fellow eyes with DMO changed from 428 +/- 153 microm at baseline to 383 +/- 151 microm at 4 months (p = 0.1), which did not reach statistical significance.

CONCLUSIONS: Intravitreal bevacizumab 1 mg every 6 weeks was followed by a moderate reduction in DMO without normalization of foveal and macular thickness. Our observations suggest that a larger study where patients are examined sooner after injection is needed to elucidate the potential relationship between changes in retinal vessel diameters and thickness changes in DMO.