Perimetry identifies visual function changes in diabetic retinopathy

By Sarah Guy, medwireNews Reporter

Perimetry could be adopted as a method to measure changes in visual function among individuals with diabetic retinopathy, show promising results from a prospective longitudinal study undertaken in Sweden.

While only two patients with the condition in the study showed retinal progression - defined as a two-step change in the Early Treatment Diabetic Retinopathy Study (ETDRS) scale - during the 18-month follow-up period, deterioration of retinal sensitivity occurred frequently among participants.

Specifically, by 18 months from study entry, half of the eyes examined deteriorated more than five test points out of a total of 54 in standard automated perimetry using the Swedish Interactive Threshold Algorithm (SITA).

"New treatment strategies to prevent disease progression at early stages of diabetic retinopathy would be of great interest," say Karl-Johan Hellgren (Lund University, Malmö) and co-investigators.

"The results [of this study] will be relevant for adopting perimetry as one possible measure of change in visual function, which should be a primary end-point in randomized clinical trials," they add in Acta Ophthalmologica.

A total of 76 patients aged 18-75 years with Type 1 or 2 diabetes were recruited to the study between September 2006 and May 2009, among whom 42 eyes had no retinopathy (ETDRS level 10) and the remaining 39 eyes had mild or moderately severe retinopathy (approximate ETDRS levels 16-45).

After 18 months, 61 eyes showed no retinopathy progression, one-step progression had occurred in seven eyes, and two eyes showed two-step progression on the ETDRS, report Hellgren et al.

In all, 30 eyes had deteriorated on the SITA by at least five test points at the 12-month follow up, and 21 eyes showed significant deterioration on this measure at both the 12- and 18-month follow up. Indeed, at this latter time point, almost no improvement in participants' visual fields was seen, with a median improvement score of zero.

"The pathophysiology behind deterioration of test points despite stable none to mild/moderate diabetic retinopathy can only be speculated upon," remark the researchers.

"The retinal vasculature constitutes a minor part of the retina, whereas the main part consists of neural tissue. Experimental data suggest that impaired glucose metabolism affects the neural retina and that neuronal retinal defects are among the earliest detectable changes in diabetes," they conclude.

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