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Repeated anti-VEGF injections may alter RNFL thickness
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A significant change in retinal nerve fiber layer thickness is associated with repeated intravitreal ranibizumab injections used to treat age-related macular degeneration, according to a study.
“Our findings indicate that whether because of the pressure elevations produced immediately following the injection procedure or because of the drug’s toxicity, significant [retinal nerve fiber layer] thinning occurred in the treated eyes, whereas no significant changes were detected in the control group,” José M. Martínez-de-la-Casa, MD, PhD, and colleagues said in the study published in Investigative Ophthalmology & Visual Science.
The researchers undertook a prospective longitudinal cohort study that compared 49 eyes of 49 patients with neovascular AMD and 27 fellow eyes without AMD.
All eyes with AMD were treated with 0.05-mL intravitreal injections of Lucentis (ranibizumab, Genentech) once a month for 3 months after diagnosis. Further injections were given if exudative lesion reactivation on the retina developed.
Retinal nerve fiber layer (RNFL) thickness and macular thickness measurements were obtained by spectral-domain optical coherence tomography at baseline and at 3, 6 and 12 months.
IOP measurements were obtained before injection and 1 hour after injection.
“Now it is well known that the more important IOP spikes occur in the first minutes after the injection,” Martinez-de-la-Casa said. “But when we designed our study, we had not much information regarding this point, so we decided to measure the IOP 1 hour after the injection. This was probably a weak point in the design of our study, and it would be interesting in the future to correlate the IOP spikes with the RNFL loss.”
After the injection, the incidence of IOP elevation spikes greater than 5 mm Hg was 0.4%, and no patient required an IOP-lowering treatment for spikes greater than 10 mm Hg, according to the study.
The mean baseline RNFL thickness recorded over 12 months for the AMD group was 105.7 ± 12.2 µm, and mean baseline RNFL thickness for the fellow eye group was 101.8 ± 11.6 µm.
When compared with baseline data, a significant RNFL thickness reduction of 5.6 ± 9.1 µm was found in the AMD group (P < .001); the 1.3 ± 9.6 µm reduction in the fellow eye group was not significant. Measurement differences between the groups were not significant during follow-up.
“In theory, RNFL modifications could be induced by the intraocular volume increase produced by the injection or through a direct toxic effect of the drug on the RNFL,” the authors said.
Although RNFL loss was significant in the AMD group, the study authors said this difference was only of relative clinical significance in a patient with an initially normal RNFL thickness. If a patient already had a compromised RNFL at the start of treatment, intravitreal injections could worsen the patient’s clinical outcome.
“In patients with glaucoma and considerable prior RNFL thinning scheduled to receive anti-VEGF treatment, it would be prudent to more closely monitor IOP elevations and to record any RNFL modifications by OCT,” the authors said.
Martinez-de-la-Casa said he believes this study will give further attention to patients with concomitant diseases other than AMD.
“In these patients, it could probably be useful to monitor their IOP more closely and even to use medications to avoid IOP spikes before the injections, as we sometimes do with other treatments, such as laser trabeculoplasty,” he said. – by Ashley Biro