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Subfoveal choroidal thickness significantly reduced in patients with diabetic retinopathy
Enhanced depth imaging optical coherence tomography confirms previous histologic studies.
A prospective study using enhanced depth imaging optical coherence tomography to assess the changes in macular choroidal thickness in eyes with various stages of diabetic retinopathy found a significant reduction in subfoveal choroidal thickness in each of the diabetic groups compared with the control group.
“A further reduction of choroidal thickness may be detected in the presence of diabetic macular edema and may colocalize with the edema,” lead author Giuseppe Querques, MD, PhD, said. “These data favor the idea that, in diabetic eyes, decreased choroidal thickness may lead to tissue hypoxia and consequently increase the level of vascular endothelial growth factor, resulting in the breakdown of the blood-retinal barrier and the development of macular edema.”
Study group
In the study published in Investigative Ophthalmology & Visual Science, 63 eyes of 63 consecutive patients with diabetes were studied: 26 were women, 37 were men, and the mean age was 65 years old. Patients were equally divided into three groups: those without diabetic retinopathy (NDR); those with nonproliferative diabetic retinopathy (NPDR) but no clinically significant macular edema (CSME); and those with both NPDR and CSME. Twenty-one healthy age- and sex-matched participants were included in a control group.
“We were interested in the study of the choriocapillaris and wanted to evaluate them with enhanced depth imaging optical coherence tomography because this new imaging technique helps us understand, in vivo, the histologic studies regarding the choroid in eyes with diabetic retinopathy,” Querques said. “Previously published histologic studies reveal that in eyes with diabetic retinopathy, there is atrophy and dropout of the choriocapillaris. Some authors have demonstrated that there is a decreased pulsatile blood flow in diabetic patients.”
Results
The authors of the current study found that mean subfoveal choroidal thickness was significantly reduced in patients with diabetes compared with the control group (P < .001). There was no significant difference in mean subfoveal choroidal thickness among the three groups of patients with diabetes: 238.4 µm for NDR, 207 µm for NPDR without CSME, and 190.8 µm for both NPDR and CSME.
Best corrected visual acuity and central macular thickness did not correlate with subfoveal choroidal thickness in any subgroup, Querques said.
Mean BCVA was 0.13 logMAR for the three groups, whereas mean central macular thickness was 272.5 µm for NDR, 294.5 µm for NPDR without CSME, and 385.6 µm for both NPDR and CSME.
This compared with a mean BCVA of 0.05 logMAR and mean central macular thickness of 297.3 µm in the control group.
“However, in some of the patients with an asymmetric distribution of macular edema, the choroid was thinned in correspondence of all sectors of retinal thickening and conversely was thickened in correspondence of those sectors without retinal thickening,” Querques said.
The authors were favorably surprised, Querques said.
“Our results were in agreement with the histologic studies,” he said, and unlike at least one previously published study, the authors found an even further reduction of subfoveal choroidal thickness in the presence of CSME.
Newer technology
Enhanced depth imaging OCT is a recently introduced imaging technology.
“Choroid in vivo studying is still at the beginning,” Querques said. “At present, there is no treatment protocol specifically regarding choroid tissue as a target, even though a successful drug delivery system more selective to the posterior pole has recently been described.”
The authors acknowledged the study was limited because there was no histopathology to correlate changes detected with enhanced depth imaging OCT. – by Bob Kronemyer