According to a study published online April 14 in Clinical & Experimental Ophthalmology, describes that the choroidal thickness changes in patients with untreated diabetes mellitus over time

To examine the choroidal layer thickness in diabetes mellitus (DM) patients and normal individuals, and to compare the findings based on the medical history of systemic DM treatments, and stage of diabetic retinopathy (DR). Choroidal thickness changes in diabetic retinopathy improve understanding the pathophysiology and management of this disease.

Hiroaki Endo, from Teine Keijinkai Hospital in Sapporo, Japan, and colleagues examined the choroidal layer thickness in 268 eyes of 134 patients with diabetes mellitus and 72 healthy controls (92 eyes) to compare the findings based on the medical history of systemic diabetes mellitus treatments and stage of diabetic retinopathy (DR).

The introduction of optical coherence tomography (OCT) into clinical practice has changed ophthalmology, and with the progression of new technology, the ability to obtain a true, non-invasive “optical biopsy” of the posterior segment is almost achievable.

Choroidal thickness can be measured using SD-OCT high definition raster scans in the majority of eyes. Choroidal thickness across the macula demonstrates a thin choroid nasally, thickest choroid sub-foveally, and again thinner temporally, and a trend toward decreasing choroidal thickness with age.

Central choroidal layer thickness (total, inner, and outer layers) was measured using enhanced depth imaging OCT. DM patients were divided into two groups; the DM treated group (88 cases), and the untreated group (46 cases). These two groups were further classified into four groups; no DR (NDR), mild/moderate non?proliferative DR (mNPDR), severe NPDR and PDR.

The researchers observed a strong correlation between masked raters of choroidal thickness measurements, proving high reproducibility. In the untreated diabetes mellitus group, the total and outer choroid thicknesses in mild/moderate non-proliferative DR (NPR) were significantly thinner versus healthy controls.

In severe NPDR, the choroidal outer layer thickness in the untreated group was considerably thicker than standard controls. However, in the group treated for diabetes mellitus, there were no significant differences regarding choroidal layer thicknesses and all stages of DR.

"The choroidal thickness significantly changed in the diabetes mellitus untreated group, and the main anatomical changes might result from the outer layer," the authors write.