Selective thinning of the perifoveal inner retina as an early sign of hydroxychloroquine retinal toxicity

Abstract

Purpose: To evaluate macular thickness profiles using spectral-domain optical coherence tomography (SDOCT) and image segmentation in patients with chronic exposure to hydroxychloroquine.

Methods: This study included eight patients with chronic exposure to hydroxychloroquine (group 1) and eight controls (group 2). Group 1 patients had no clinically evident retinal toxicity. All subjects underwent SDOCT imaging of the macula. An image segmentation technique was used to measure thickness of six retinal layers at 200 microm intervals. A mixed-effects model was used for multivariate analysis.

Results: By measuring total retinal thickness either at the central macular (2800 microm in diameter), the perifoveal region 1200-microm-width ring surrounding the central macula), or the overall macular area (5200 microm in diameter), there were no significant differences in the thickness between groups 1 and 2. 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 1 compared with that of group 2 by using the mixed-effects model analysis.

Conclusion: Our study 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 the reason most patients who have early detectable signs of drug toxicity present with paracentral or pericentral scotomas.

FIGURE 1

An example of a vertical scan through the foveal center in a control subject, displaying a retinal layer segmentation technique applied to spectral-domain optical coherence tomography (SDOCT) image. The retina is segmented with 7 boundary lines into 6 layers, including 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), respectively (from top to bottom).

FIGURE 2

Cartoon shows the central macular area (A) and perifoveal area (B), as referred to in this study.