IVR injection frequency tied to inferior subfield thickness in diabetic macular oedema
The baseline inferior subfield retinal thickness may predict the frequency of treatment for diabetic macular oedema (DME) during the first year in eyes administered pro re nata (PRN) intravitreal ranibizumab (IVR) injections, a new study shows.
The study included 68 eyes of 63 centre-involved DME patients who had received IVR injections for at least 12 months. Three IVR injections were administered monthly according to PRN dosing.
Spectral-domain optical coherence tomography (SD-OCT) scanning was performed to measure the mean retinal thickness at baseline. The outcome was the relationship between the thickness parameters at baseline and the number of IVR injections over a follow-up period of 12 months.
Of the 68 eyes, 10 received three loading doses, 34 received four to seven annual injections and 24 received at least eight injections.
There was a significant positive association between central subfield thickness and the number of injections received during the first year (p<0.001). Injection frequency was also related to the thickness of the fovea (p<0.001) and the nasal (p<0.001), temporal (p=0.002), superior (p=0.023) and inferior (p<0.001) subfields of the parafovea.
In 54 eyes with cystoid macular oedema (CME), height of the foveal cystoids spaces was significantly associated with treatment frequency (p=0.002). The disruption of the EZ line and external limiting membrane (ELM) was also associated with the number of injections (p=0.032 and p=0.002, respectively).
Multivariate analysis showed that the number of IVR injections was significantly associated only with the retinal thickness in the inferior subfield (p<0.001).
Treatment frequency was not related to the height of serous retinal detachments (SRD; p=0.130), baseline ophthalmic findings, systemic factors and improved visual acuity.