Ballios Brian G, Weisbrod Daniel, Kohly Radha, Muni Rajeev H, Wright Tom, Yan Peng
Department of Ophthalmology and Vision Sciences, University of Toronto, 340 College Street, Suite 400, Toronto, ON, M5T 3A9, Canada.
Department of Ophthalmology and Vision Sciences, University of Toronto, 160 College St., Room 1106, The Donnelly Centre, Toronto, ON, M5S 3E1, Canada.
Doc Ophthalmol. 2020 Oct;141(2):181-185. doi: 10.1007/s10633-020-09759-y. Epub 2020 Mar 7.
The available literature regarding Oguchi disease is limited, with around 50 cases described to date. Caused by mutations to either the SAG gene coding for arrestin (Hayashi et al. in Ophthalmic Res 46:175-180, 2011) or the GRK1 gene coding for rhodopsin kinase (Yamamoto et al. in Nat Genet 15:175-178. https://doi.org/10.1038/ng0297-175 , 1997), Oguchi disease is an autosomal recessive condition with a good visual prognosis. The clinical diagnosis of the condition is based on the presence of night blindness (nyctalopia), as well as fundoscopic observation of the Mizuo-Nakamura phenomenon. The Mizuo-Nakamura phenomenon refers to a fundus discolouration described as a golden-brown colour with a yellow-grey metallic sheen most prominent in the peripheral retina; after prolonged dark adaptation, the fundus appears normal. The prevalence of Oguchi disease is highest in Japan, particularly with SAG mutations (Nakazawa et al. in Retina 17:17-22, 1997), although patients from Europe, Pakistan and India have also been described. Formal diagnosis requires genetic testing.
Wide-field fundus images were obtained in both dark-adapted and light-adapted retina. Optical coherence tomography and dark-adapted electroretinography responses were used to further characterize the clinical phenotype.
Existing descriptions of Oguchi disease have been limited by available technology. The flashes required for 45°-montage photographs in a dark-adapted eye quickly cause light adaptation. Recent advances in technology enable the capture of larger retinal areas in a single image. Wide-field 133° images were obtained of the native and dark-adapted fundus in natural colour. To our knowledge, these represent the first reported single-wide-field images of Oguchi disease, showing the characteristic Mizuo-Nakamura phenomenon in true colour. Genetic testing revealed a novel homozygous mutation in GRK1.
Here, we demonstrate how characterizing this condition with single-shot true-colour wide-field imaging has distinct advantages over scanning laser technology, which applies artificial colouration, or stitched true-colour images. Images captured with wide-field systems create a much better representation of the native and dark-adapted fundus than can be observed by the ophthalmologist using direct fundoscopy and are essential in the clinical characterization of new mutations.
关于小口病的现有文献有限，迄今为止报道的病例约有50例。小口病是一种常染色体隐性疾病，视力预后良好，由编码抑制蛋白的SAG基因（林等人，《眼科研究》46:175 - 180，2011年）或编码视紫红质激酶的GRK1基因（山本等人，《自然遗传学》15:175 - 178。https://doi.org/10.1038/ng0297 - 175，1997年）发生突变所致。该病的临床诊断基于夜盲症（夜视力减退）的存在以及眼底镜检查中观察到的水尾 - 中村现象。水尾 - 中村现象是指眼底变色，呈现金棕色并带有黄灰色金属光泽，在外周视网膜最为明显；经过长时间暗适应后，眼底看起来正常。小口病在日本的患病率最高，尤其是由SAG基因突变引起的病例（中泽等人，《视网膜》17:17 - 22，1997年），不过欧洲、巴基斯坦和印度也有病例报道。确诊需要进行基因检测。
在暗适应和明适应的视网膜上获取广角眼底图像。使用光学相干断层扫描和暗适应视网膜电图反应来进一步明确临床表型。
小口病的现有描述受到现有技术的限制。在暗适应眼中拍摄45°拼接照片所需的闪光会迅速导致光适应。技术的最新进展使得能够在单张图像中捕获更大的视网膜区域。获取了自然颜色的暗适应眼底的133°广角图像。据我们所知，这些是首次报道的小口病单张广角图像，真实地展现了特征性的水尾 - 中村现象。基因检测发现GRK1基因存在一种新的纯合突变。
在此，我们展示了与应用人工着色的扫描激光技术或拼接的真彩色图像相比，单次真彩色广角成像在表征这种疾病方面具有明显优势。广角系统拍摄的图像比眼科医生使用直接眼底镜观察到的能更好地呈现暗适应眼底的原貌，对于新突变的临床特征描述至关重要。
