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Ahmed Abdel-hay, Sobha Sivaprasad, Ahalya Subramanian, Evgenia Konstantakopoulou, David Edgar, John Barbur; Chromatic sensitivity in diabetic patients treated with Ozurdex. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4920.
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Clinical trials that compare treatment modalities for diabetic macular oedema (DME) rely on measurements of macular thickness using Optical Coherence Tomography (OCT) to monitor the effectiveness of therapy. Changes in macular thickness do not, however, correlate with change in visual acuity. It is therefore of interest to establish whether changes in colour thresholds can be used to evaluate the efficacy of Ozurdex in the treatment of DME. The purpose of the study was to measure the changes in red-green (RG) and yellow-blue (YB) thresholds during treatment with Ozurdex using the CAD (Colour Assessment & Diagnosis) test which isolates the use of colour signals and provides age-corrected, normal statistical limits (Expert Rev.Ophthalmol. 6:409-420, 2011). The test quantifies accurately the severity of colour vision loss and indicates statistically significant changes in both RG and YB thresholds.
13 patients (mean age 56 ± 9.5 years) with DME undergoing treatment with Ozurdex were recruited. RG and YB colour thresholds were measured using the CAD test at baseline and 24 weeks post-injection. Visual acuity was measured using ETDRS letter chart and central sub-field retinal thickness (CST) using the Heidelberg Spectralis SD-OCT scan.
All diabetic patients (n=13 eyes), had significant loss of RG and YB chromatic sensitivity at the baseline measurement (p<0.05). The age specific, monocular, upper normal limits for a 56 years old subject (i.e., µ+2σ) are 2.66 for RG and 2.85 for YB. In this study, the mean ±σ for RG was 22.08 ± 11.57 and for YB was 16.12 ± 3.90 pre-injection. There was significant improvement in mean RG threshold post-injection: mean= 19.93 ± 10.92 (p<0.05). No significant changes were found in YB threshold: mean= 15.72 ± 4.76 (p=0.23). The severity of colour vision loss (RG and YB) measured with the CAD test showed negligible correlation with visual acuity or central sub-field thickness (r2=-0.05) and (r2=0.17), respectively.
RG and YB colour thresholds provide a sensitive measure of functional change in diabetics, but the loss of colour vision shows poor correlation with visual acuity and central retinal thickness. These preliminary findings also suggest that RG loss, as measured with the CAD test, can be used to monitor the efficacy of treatment in DME.
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