Optical Coherence Tomographic Reflectivity Of Photoreceptors Beneath Cystoid Spaces In Diabetic Macular Edema

Abstract

Purpose: : Several studies using optical coherence tomography (OCT) demonstrated that foveal photoreceptor status significantly influence visual function in diabetic macular edema (DME), although it remains ill-defined how disrupted blood-retinal barrier (BRB) exacerbate the disturbance of photoreceptors. Here we investigated the association photoreceptor changes and cystoid spaces which are believed to be induced by vascular hyperpermeability in DME.

Methods: : Consecutive 50 eyes from 40 patients with clinically significant macular edema (CSME) on which the images of spectral domain (SD)-OCT (Spectralis OCT, Heidelberg Engineering) with enough quality were obtained were included. Eyes with serous retinal detachment were excluded. In the cross-hair images with 30 degrees dissecting the fovea, the status of the junction of inner and outer segments (IS/OS) were graded into three; ‘intact’ IS/OS means the highly reflective band, ‘faint’ one is the distinct band with markedly decreased reflectivity, and ‘disrupted’ did not present the distinct band. Additionally, external limiting membrane (ELM) was classified into intact or disrupted. We then evaluated the association between cystoid spaces in outer plexiform layer (OPL) and photoreceptor changes beneath them.

Results: : Logarithm of the minimum angle of resolution (logMAR) was significantly associated with the transverse length of disrupted IS/OS or disrupted ELM in 500 µm from the foveal center (r=0.542, p<0.001 and r=0.221, p=0.036, respectively). The transverse length of faint or disrupted IS/OS beneath cystoid spaces was 14.5±13.9 % (vs. total length), whereas the length of such types of IS/OS beneath OPL without cystoid spaces was significantly shorter (4.2 ± 8.9 %, p<0.001). Furthermore, eyes with cystoid spaces extending from inner nuclear layer (INL) to OPL were accompanied with disrupted ELM with significantly higher frequency (p<0.001).

Conclusions: : These data suggest that the status of foveal photoreceptors were influenced by cystoid spaces in OPL in DME.

Keywords: diabetic retinopathy • photoreceptors • macula/fovea