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S. Pasadhika, G. A. Fishman, D. Choi, M. Shahidi; Perifoveal Inner Retinal Thinning as an Early Sign of Hydroxychloroquine Retinal Toxicity. Invest. Ophthalmol. Vis. Sci. 2010;51(13):320.
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To study macular multi-lamellar thickness measurements using spectral-domain optical coherence tomography (SDOCT) and image segmentation in patients with chronic exposure to hydroxychloroquine.
This study included 8 patients with chronic exposure to hydroxychloroquine (Group A) and 8 age-similar, gender- and race-matched controls (Group B). None of the Group A patients had clinically-evident retinal toxicity, evaluated by funduscopic examination, color vision testing, multifocal electroretinography and Humphrey visual field examination. SDOCT macular scans were obtained in all subjects. An image segmentation technique was used to measure thickness of 6 retinal layers (retinal nerve fiber layer (RNFL), ganglion cell + inner plexiform layers (GCL+IPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer + photoreceptor inner segments (ONL+PIS), and photoreceptor outer segments (POS)), at 200 µm intervals of the vertical and horizontal scans. A mixed-effects model was used for multivariate analysis.
By measuring total retinal thickness, either at the central macular (2800 µm in diameter), the perifoveal region 1200-µm-width ring surrounding the central macula), or the overall macular area (5200 µm in diameter), there were no significant differences in the thickness between Groups A and B. On an image segmentation analysis, selective thinning of the inner plexiform + ganglion cell layers (p=0.021) was observed only in the perifoveal area of the patients in Group A compared to that of Group B by using the mixed-effects model analysis.
Our results suggest that chronic exposure to hydroxychloroquine is associated with thinning of the perifoveal inner retinal layers, especially in the ganglion cell and inner plexiform layers, even in the absence of functional or structural clinical changes involving the photoreceptor or retinal pigment epithelial cell layers. This may be a contributing factor as to why most patients who have early detectable signs of drug toxicity present with paracentral or pericentral scotomas.
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