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Mark Seamone, Katherine Milton, Micheline Deschenes, Michael Fielden, Amin Kherani, R Geoff Williams, ; A comparison of spectral domain optical coherence tomography and multifocal electroretinography findings in hydroxychloroquine retinopathy. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3597.
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Hydroxychloroquine can cause ocular toxicity in the form of pigmentary retinopathy that is associated with debilitating visual impairment. The early detection of hydroxychloroquine retinopathy is essential to the visual prognosis of affected individuals. Currently, multifocal electroretinogram (mfERG) is considered the gold standard for detecting early-stage hydroxychloroquine-induced retinal pathology. However, accessibility to mfERG is limited and discrepancies in mfERG recordings are often noted upon serial examination of individual patients. Spectral domain ocular coherence tomography (SD-OCT) is a newly described method of ocular imaging that allows for high-speed analysis of retinal pathology. In this manuscript, the ability of mfERG and SD-OCT to detect hydroxychloroquine-induced retinal injury was compared.
Patients receiving hydroxychloroquine for a minimum of 5 years (or with clinically apparent disease) were selected on the basis of mfERG findings (N=15). Individual eyes were assigned an mfERG grade (mfERG grade 1-3) reflecting the observed degree of retinal pathology (N=30). Two retinal specialists who are experts in SD-OCT analysis compared SD-OCT abnormalities with mfERG findings for each grade.
SD-OCT abnormalities were not observed in individuals with grade 1 and 2 mfERG findings. However, SD-OCT was capable of detecting retinal injury in eyes with grade 3 mfERG abnormalities. Commonly observed irregularities included focal and generalized macular thinning, degradation of the IS/OS photoreceptor junction and thinning of the outer nuclear layer (ONL). Interestingly, when eyes with grade 3 mfERG abnormalities were sub-divided into groups of moderate and end-stage hydroxychloroquine toxicity, thinning of the ONL consistently preceded injury to the IS/OS junction. In support of these observations, ONL thickness was decreased in individuals with moderate and end stage toxicity upon quantitative analysis.
These results suggest that mfERG can detect hydroxychloroquine toxicity prior to SD-OCT. Nonetheless, thinning of the outer nuclear layer upon SD-OCT analysis should raise clinical suspicion of hydroxychloroquine-induced retinal injury. This information is of clinical significance as it suggests that SD-OCT should be used in conjunction with mfERG for the early detection of hydroxychloroquine retinopathy.
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