Retinal function, structure changes in proliferative diabetic retinopathy revealed

By Shreeya Nanda, Senior medwireNews Reporter

Patients with proliferative diabetic retinopathy (PDR) exhibit marked visual dysfunction and structural changes in both the inner and outer retinal layers, research findings indicate.

Overall visual impairment was worse and structural alterations more severe in individuals who had undergone panretinal photocoagulation (PRP) compared with those who had not, say Thomas Gardner, from University of Michigan Medical School in Ann Arbor, USA, and colleagues.

Retinal function was evaluated using a number of tests, including contrast sensitivity, frequency doubling perimetry (FDP) and photostress testing. And semiautomatically segmented spectral-domain optical coherence tomography scans were used to quantify thickness of retinal layers.

Log contrast sensitivity was significantly reduced in the 30 PRP-treated PDR patients and the 15 untreated PDR patients compared with 15 age-matched healthy controls, at 1.42 and 1.56 versus 1.80. The difference between treated and untreated PDR patients was also significant.

The FDP mean deviation was –8.20 for patients who had undergone PRP, –5.48 for those who had not and 1.07 for the controls, with both treated and untreated groups differing significantly from the control group.

Photostress recovery time and dark adaptation speed were significantly longer in PRP-treated patients relative to the healthy controls, at 151.02 sec versus 70.64 sec and 12.80 min versus 9.74 min, respectively. But with corresponding values of 93.21 sec and 10.22 min, treatment-naïve patients were comparable to controls.

PRP-treated patients had significantly thickened nerve fibre layers compared with treatment-naïve participants and controls, at an average thickness of 48.41 μm versus 41.67 μm and 38.09 μm, respectively.

By contrast, retinal pigment epithelium (RPE) was significantly thinner in both the treated and untreated patients than in controls, at 25.64 μm and 25.92 μm versus 29.03 μm.

These findings “augment the current body of evidence for RPE degeneration in diabetes by demonstrating in vivo the presence of RPE–photoreceptor complex pathologic features in treated and untreated patients with PDR”, comment the researchers.

They conclude in Ophthalmology: “Improved understanding of the pathogenesis of visual dysfunction in individuals with PDR and in those who have undergone PRP could lead to the identification of therapeutic targets for these patients.”

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