Evaluation of photoreceptor outer segment length in hydroxychloroquine users

This study aims to evaluate the photoreceptor outer segment (PROS) length in patients who use hydroxychloroquine (HCQ) prior to the development of retinopathy.

In this prospective, single-centre, comparative study, 44 patients using HCQ for ≥5 years, 30 patients using HCQ <5 years, and 45 age- and sex-matched healthy controls were enrolled. The participants underwent a detailed ophthalmologic examination, spectral-domain optical coherence tomography (SD-OCT) imaging, and 10-2 automated visual field testing. The PROS length was defined as the distance between the inner surface of the ellipsoid zone and the inner surface of the retina pigment epithelium. The measurements were performed subfoveally and at 500-1000-1500 µm temporally and nasally to the foveola.

The mean PROS length of long-term users (≥5 years) was statistically greater than the controls at all measurement points (p < 0.001 at all points). Although the subfoveal PROS length was comparable between the long-term and short-term users (p = 0.148), the parafoveal PROS length measurements (nasal 1500 µm, nasal 1000 µm, nasal 500 µm, temporal 1000 µm, and temporal 1500 µm) of the long-term users were significantly greater than those of the short-term users (p < 0.001, p = 0.002, p = 0.027, p = 0.018, p = 0.001, respectively). No significant difference was found between the short-term users and the controls (p = 0.815, p = 0.395, p = 0.093, p = 0.079, p = 0.133, p = 0.686, p = 0.341, respectively).

The PROS length was greater in patients who used HCQ ≥5 years. Possible retinal pigment epithelium toxicity may have caused this finding.