Ranibizumab for DME: Short-Term Effects on Foveal Thickness Predict Visual Acuity Changes
Foveal thickness 2 hours post-injection correlated with acuity 1 month later.
Multiple clinical trials have shown improvement in vision and reduction in foveal thickness 1 week or 1 month after intravitreal injection of ranibizumab (Lucentis/Roche) for diabetic macular edema (DME). However, the structural effects of ranibizumab a few hours after injection and their ability to predict visual outcome 1 month after injection have been less well studied.
To assess the short-term anatomical effects of a single intravitreal injection of ranibizumab and their ability to predict visual outcome 1 month after injection, Yoshiro Minami, MD, and colleagues in the Department of Ophthalmology at Nayoro City General Hospital in Nayoro and at Asahikawa Medical University in Asahikawa, Japan, did a prospective interventional case series. For the purposes of the study, they defined short-term effects as those occurring within 1 day after injection.
The team enrolled 20 consecutive patients with DME (24 eyes) in the study and treated them prospectively with ranibizumab, 0.5 mg/0.05 mL, from April 2014 to May 2015. Inclusion criteria were a baseline foveal thickness of at least 300 μm and no history of ocular surgery (including laser surgery) or other treatment for DME in the previous 10 weeks. No patient enrolled in the study had a history of intravitreal injection with an anti-vascular endothelial growth factor agent or placement of a dexamethasone implant.
The team excluded patients from the study if the logarithm of the minimum angle of resolution (logMAR) of visual acuity was less than zero, or a Snellen chart equivalent of 20/200. After one patient withdrew and the team excluded five patients (two for low visual acuity and three who needed laser therapy within 2 months of injection), 14 patients (18 eyes) remained in the study.
The team then measured foveal thickness before and 2 hours, 1 day, 1 week, and 1 month after intravitreal injection of ranibizumab by using the macular map analysis protocol of the RetinaScan RS-3000 spectral-domain optical coherence tomography machine. The team also measured best-corrected visual acuity (BCVA) at the same time points (except for 2 hours after injection) by using a standard Japanese decimal visual acuity chart at 5 meters and by converting the decimal values into logMAR units to enable statistical analysis. They then compared the changes from baseline measurements at each time point.
They found that mean foveal thickness decreased significantly (P < 0.0001) from a baseline of 452 ± 77 μm to 429 ± 65 μm 2 hours after injection. Moreover, the mean logMAR of BCVA improved significantly (P = 0.032) from a baseline of 0.41 ± 0.24 to 0.32 ± 0.21 1 month after injection, or, in terms of Snellen chart equivalents, from 20/51 to 20/42. In addition, the team found that the change in foveal thickness noted 2 hours after injection correlated with the change in visual acuity noted 1 month after injection (r = 0.59; P = 0.01).
As a result, the team concluded that, in the DME patients they studied, the structural effects of an intravitreal injection of ranibizumab occurred within 2 hours, but the functional effects of ranibizumab became apparent 1 month after injection. They also concluded that the short-term structural effects of an intravitreal injection of ranibizumab might predict visual outcome 1 month after intravitreal injection of ranibizumab in patients with DME.
A report of the study, “Short-term effects of intravitreal ranibizumab therapy on diabetic macular edema,” appeared in mid-March in BMC Ophthalmology.
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