Abstract
PurposeTo evaluate changes in colour vision following intravitreal injection of Dexamethasone implant (Ozurdex) in patients with diabetic macular oedema (DMO). Both red-green (RG) and yellow-blue (YB) chromatic sensitivity were assessed using the Colour Assessment & Diagnosis (CAD) test which isolates the use of colour signals and provides age-corrected, statistical limits for normal trichromats. To determine whether colour changes and visual acuity (VA) post-treatment relate to central sub-field retinal thickness (CST).MethodsFourteen patients with DMO who were undergoing treatment with Ozurdex were recruited for this study. RG and YB colour thresholds were measured using the CAD test, best corrected visual acuity was assessed using the ETDRS chart and CST was measured using spectral domain optical coherence tomography (SD-OCT). All tests were performed monocularly at baseline and 24 weeks post injection.ResultsAll patients (n = 14 eyes), had significant loss of RG and YB chromatic sensitivity at baseline (p<0.05). The mean age was 56 ± 9.5 years. The age specific, monocular, upper normal limits for a 56 year old subject are 2.66 for RG and 2.85 for YB. In this study, the measured, pre injection thresholds (mean±SD) were 22.6 ± 11.3 for RG and 16.2 ± 3.76 for YB. There was significant improvement in RG threshold post injection (i.e., 19.2 ± 10.8 (p<0.05)). No significant changes were found in the YB thresholds with corresponding mean and range values of: 15.8 ± 4.6 (p = 0.23). CST pre-treatment was 542 ±135 μm. After treatment and by week 24 the CST values decreased to 435 ±127 μm.ConclusionsRG colour thresholds provide a sensitive measure of functional change in diabetic subjects with macular oedema. The YB system is damaged severely in the DMO patients studied and shows little or no recovery post treatment. The improvement in VA and particularly in RG colour vision correlate well with the measured decrease in CST. The results suggest that the improvement in the RG chromatic sensitivity can provide a useful biomarker for monitoring the efficacy of treatment in DMO.
Highlights
Diabetic macular oedema (DMO) affects 20% of patients with DR [1] and can cause vision loss independent of the grade of retinopathy.Inflammation plays an important role in the pathophysiology of DMO and is mediated through the expression of prostaglandins, leukotrienes and vascular endothelial growth factor (VEGF) [2]
After treatment and by week 24 the central sub-field retinal thickness (CST) values decreased to 435 ±127 μm
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Summary
Diabetic macular oedema (DMO) affects 20% of patients with DR [1] and can cause vision loss independent of the grade of retinopathy. Inflammation plays an important role in the pathophysiology of DMO and is mediated through the expression of prostaglandins, leukotrienes and VEGF [2]. More recently antiVEGF has been introduced for use in the treatment of DMO. Steroids can be useful in the treatment of DMO by blocking the production of VEGF and other inflammatory mediators [5,6,7,8]. The use of steroids is, associated with raised intraocular pressure (IOP) in up to 50% of patients and cataract formation in 40% of the injected eyes [9]. Similar to antiVEGF drugs such as ranibizumab, the effect is short-lived and patients require frequent injections with higher cumulative risks of side effects
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