Association between external limiting membrane status and visual acuity in diabetic macular oedema

To evaluate the association between the foveal external limiting membrane (ELM) status and visual acuity (VA) in diabetic macular oedema (DMO).

We retrospectively reviewed the spectral domain optical coherence tomography images of 127 eyes from 127 patients with DMO and evaluated the correlation between the logarithm of the minimal angle of resolution (logMAR) VA and the statuses of the foveal ELM, inner segment/outer segment (IS/OS) and cone outer segment tips (COST); foveal macular thickness (FMT); and presence or absence of hard exudates (HE), serous retinal detachment (SRD) and vitreous adhesion. The integrity of the ELM, IS/OS, and COST was classified into three categories (absent, disrupted and complete).

There was a strong correlation between VA and the statuses of the ELM (r=0.699, p<0.001), IS/OS (r=0.716, p<0.001) and COST (r=0.471, p<0.001). There was no correlation between FMT and logMAR VA (r=-0.036, p=0.687). However, when we analysed the correlation between FMT and VA by dividing patients into those with FMT ≤250 μm and those with FMT >250 μm, there was a positive correlation between FMT and VA in eyes with FMT ≤250 μm (r=-0.601, p<0.0001) and a negative correlation in eyes with FMT>250 μm (r=0.290, p<0.01). Other factors HE, SRD and vitreous adhesion did not correlate with VA.

In DMO, the ELM status may be as closely related to VA as the IS/OS status.