Outer retinal circular structures in patients with Bietti crystalline retinopathy

Background Bietti crystalline retinopathy (BCR) is a distinct retinal degenerative disease characterised by retinal degeneration with many yellow-white crystals located mainly at the posterior pole area. Using spectral domain-optical coherence tomography (SD-OCT), the structural change in retina was investigated. Methods Patients diagnosed with BCR (n = 12), retinitis pigmentosa (RP, n = 292) and cone dystrophy (n = 16) were included in this study. The authors mainly examined fundus photographs and SD-OCT, infrared and fundus autofluorescence images of these patients. Results Crystalline deposits were detected in portions of the retinal pigment epithelium that lacked patchy degenerated lesions. SD-OCT revealed that most of the observed crystalline deposits were located adjacent to the inner side of retinal pigment epithelium layer. The change most frequently observed was circular hyper-refractive structures in the outer nuclear layer. Although the structures were considered to be previously reported "tubular formation" or "tubular degeneration", we determined that many of these circular structures were slices of spherical structures and were typically noted in areas suspected of ongoing active degeneration. Conclusion BCR has characteristic structures in the outer nuclear layer. Although the incidence of the structure varies, it may be characteristic of retinal degeneration and can be found in many retinal degenerative diseases.