Choroidal thickness reduced in diabetic macular oedema patients

Patients with diabetic macular oedema (DME) have smaller choroidal thickness measurements in affected and unaffected eyes compared with healthy individuals, spectral-domain optical coherence tomography (SD OCT) imaging results reveal.

The clinical trial included automated analysis of SD OCT scans and fluorescein angiograms for 115 patients with clinically significant but untreated DME in one eye, plus eyes from 20 healthy individuals.

Total choroidal thickness was significantly reduced in the eyes directly affected by DME and the nonoedematous fellow eyes of the patients than that of the control eyes, at 175 µm and 177 µm versus 190 µm, respectively.

And choroidal thinning was found to occur over the entire posterior pole of DME eyes and fellow eyes, “suggesting a systemic pathophysiologic mechanism unrelated to the presence of retinal disease”, say Christian Simader, from Medical University of Vienna in Austria, and co-authors in the American Journal of Ophthalmology.

“This finding was further supported by the fact that choroidal changes did not correlate with the level of retinal pathology”, they add.

Indeed, there was no significant correlation between retinal thickness and choroidal thickness, as measured using a fovea-centred or peak of oedema-centred Early Treatment Diabetic Retinopathy Study grid.

Nor was there any correlation for other measurements of retinal thickness and choroidal thickness, such as eyes with DME versus control eyes or fellow eyes, peak of oedema versus healthy control or fellow eyes.

However, a “minimal” negative correlation was found between the average retinal leakage area in DME eyes and choroidal thickness, indicating that “a tendency for a thinner choroidal layer with larger leakage areas can be assumed”, the authors suggest.

Noting that poor quality fully automated choroidal segmentation images did not affect results, the team concludes: “With these fast and reliable automated procedures, large populations can be analyzed and choroidal disease can be quantified reliably and correlated with associated retinal disease in an attempt to further improve our understanding of ocular vascular disease in diabetes.”

Am J Ophthalmol 2014; 158: 1039–1048.e1

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