Dryja T P
Department of Ophthalmology, Harvard Medical School and the Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, USA.
Am J Ophthalmol. 2000 Nov;130(5):547-63. doi: 10.1016/s0002-9394(00)00737-6.
To compare the clinical findings of the various forms of stationary night blindness caused by mutations in identified genes encoding proteins of photoreceptors or the retinal pigment epithelium.
Review of the visual acuities, visual fields, fundi, dark-adaptation curves, and electroretinograms from patients with stationary night blindness caused by mutations in the genes RHO, GNAT1, PDE6B, RHOK, SAG, RDH5, and CACNA1F, respectively encoding rhodopsin, the alpha subunit of rod transducin, the beta subunit of rod cGMP-phosphodiesterase, rhodopsin kinase, arrestin, 11-cis retinol dehydrogenase, and a retinal L-type calcium channel.
In the evaluated forms of stationary night blindness, the time course of dark adaptation and the characteristics of the electroretinogram indicate that rod photoreceptors are present and that they function, although abnormally. In night blindness resulting from defects in rhodopsin, the alpha subunit of rod transducin, or the beta subunit of rod cGMP phosphodiesterase, rod photoreceptors respond only to light intensities far brighter than normal, and the sensitivity of rods to light is similar to that of normal individuals who are not dark adapted. In fundus albipunctatus and in Oguchi disease, the rod photoreceptors can achieve normal sensitivity to dim light but only after 2 or more hours of dark adaptation, compared with approximately 0.5 hours for normal individuals. In each of these forms of stationary night blindness, the poor rod sensitivity and the time course of dark adaptation correlate with the known or presumed physiologic abnormalities caused by the identified gene defects. Patients with some forms of stationary night blindness, such as fundus albipunctatus and Oguchi disease, may develop degeneration of the retina leading to severe loss of vision in later life.
The identification of the mutant genes causing forms of stationary night blindness refines the classification of these diseases and enhances our understanding of the underlying physiologic defects. Ophthalmologists must be aware that although these diseases are traditionally categorized as "stationary," some of them lead to reduced visual acuity or constricted visual fields, especially in older patients. Efforts to develop therapies for these diseases should concentrate on these more severe forms.
比较由编码光感受器或视网膜色素上皮蛋白的已鉴定基因突变引起的各种形式的静止性夜盲的临床特征。
回顾分别由基因RHO、GNAT1、PDE6B、RHOK、SAG、RDH5和CACNA1F突变导致的静止性夜盲患者的视力、视野、眼底、暗适应曲线和视网膜电图，这些基因分别编码视紫红质、视杆转导蛋白的α亚基、视杆cGMP磷酸二酯酶的β亚基、视紫红质激酶、抑制蛋白、11-顺式视黄醇脱氢酶和视网膜L型钙通道。
在评估的静止性夜盲形式中，暗适应的时间进程和视网膜电图的特征表明视杆光感受器存在且功能异常。在由视紫红质、视杆转导蛋白的α亚基或视杆cGMP磷酸二酯酶的β亚基缺陷导致的夜盲中，视杆光感受器仅对远高于正常的光强度有反应，并且视杆对光的敏感性与未进行暗适应的正常个体相似。在白点状眼底和小口病中，视杆光感受器在暗适应2小时或更长时间后才能达到对暗光的正常敏感性，而正常个体约需0.5小时。在这些静止性夜盲的每种形式中，视杆敏感性差和暗适应的时间进程与已鉴定的基因缺陷引起的已知或推测的生理异常相关。某些形式的静止性夜盲患者，如白点状眼底和小口病患者，可能在晚年发生视网膜变性，导致严重视力丧失。
导致静止性夜盲形式的突变基因的鉴定完善了这些疾病的分类，并增强了我们对潜在生理缺陷的理解。眼科医生必须意识到，尽管这些疾病传统上被归类为“静止性”，但其中一些会导致视力下降或视野缩小，尤其是在老年患者中。开发这些疾病治疗方法的努力应集中在这些更严重的形式上。
