Moshirfar Majid, Milner Dallin, Patel Bhupendra C.
University of Utah/John Moran Eye Center; Hoopes Vision/HDR Research Center; Utah Lions Eye Bank
University of Colorado School of Medicine
Cataracts are the world’s leading cause of remediable blindness. While some cataracts, may be congenital, secondary to trauma, or drug-induced, most cataracts are age-related. Age-related cataracts are due to the opacification of the lens. The crystalline lens is a biconvex structure that focuses light on the retina. It is transparent with a diameter of 10 mm and an axial length of around 4 mm. The lens consists of fibers that are derived from lens epithelium, a thin surrounding capsule, and zonular fibers that allow for accommodation in conjunction with the ciliary body. With age, the lens stiffens, leading to farsightedness known as presbyopia. While one of the main functions of the lens is to focus light, it is not a passive optical element. In order to maintain transparency, the lens has a microcirculation pathway driven by sodium channels that deliver nutrients to deeper fibers through extracellular inward flow. Intracellular outward flow is maintained through gap junctions and is used to remove waste. The lens also serves as a UV filter that protects the retina. Finally, the lens acts as an oxygen sink with some of the highest concentrations of the antioxidant glutathione (GSH) in the body. Glutathione scavenges reactive oxygen species, is a co-factor for repair enzymes, and is thought to be released into the aqueous humor to be used by the avascular tissues such as the cornea and trabecular network. With age, oxidative damage can accumulate, causing an opacification of the lens. Regardless of the etiology, the treatment is cataract surgery when the visual function is affected. Cataract has secondary complications such as glaucoma and uveitis when it is allowed to progress on its natural course. With newer and well-developed techniques, cataract surgery is one of the most successful clinical managements in medicine with direct improvements in visual acuity as well as large improvements in activities of daily living and decreased mortality. While as many as 95% of patients will have improved visual acuity, cataract surgery does have complications. The most common include posterior capsule opacification and cystoid macular edema. Rare but serious complications include endophthalmitis and retinal detachment. Cataracts are one of the most common ophthalmic pathologies characterized by the opacification of the lens. In 2013, the United States had more than 22 million people who had cataracts. In 2020, that number is expected to reach 30.1 million. Incidence increases with age; 43-year-old to 54-year-old patients have an incidence of 8.3%, while patients over 75 have an incidence as high as 70.5%. Women are slightly more affected, with an average incidence of 26% and men 22.6%. In 2015, 3.7 million cataract surgeries were performed in the United States with data suggesting that the incidence of cataract surgery will continue to increase.
白内障是全球可治愈性失明的首要原因。虽然有些白内障可能是先天性的、继发于外伤或药物所致，但大多数白内障与年龄相关。年龄相关性白内障是由于晶状体混浊引起的。晶状体是一个双凸结构，可将光线聚焦在视网膜上。它呈透明状，直径为10毫米，轴向长度约为4毫米。晶状体由源自晶状体上皮的纤维、一层薄薄的周围囊膜以及与睫状体协同作用以实现调节功能的悬韧带纤维组成。随着年龄增长，晶状体变硬，导致远视，即老花眼。虽然晶状体的主要功能之一是聚焦光线，但它并非一个被动的光学元件。为了保持透明，晶状体有一条由钠通道驱动的微循环途径，该途径通过细胞外内向流动将营养物质输送到更深层的纤维。细胞内的外向流动通过缝隙连接得以维持，并用于清除废物。晶状体还充当紫外线过滤器，保护视网膜。最后，晶状体作为一个氧阱，体内抗氧化剂谷胱甘肽（GSH）的浓度在此处是最高的。谷胱甘肽可清除活性氧，是修复酶的辅助因子，并且被认为会释放到房水中供角膜和小梁网等无血管组织使用。随着年龄增长，氧化损伤会不断累积，导致晶状体混浊。无论病因如何，当视觉功能受到影响时，治疗方法就是白内障手术。如果任其发展，白内障会引发青光眼和葡萄膜炎等继发性并发症。随着技术的更新与完善，白内障手术是医学上最成功的临床治疗手段之一，可直接提高视力，显著改善日常生活活动能力并降低死亡率。虽然多达95%的患者视力会得到改善，但白内障手术确实存在并发症。最常见的包括后囊膜混浊和黄斑囊样水肿。罕见但严重的并发症包括眼内炎和视网膜脱离。白内障是以晶状体混浊为特征的最常见眼科疾病之一。2013年，美国有超过2200万人患有白内障。到2020年，这一数字预计将达到3010万。发病率随年龄增长而上升；43岁至54岁的患者发病率为8.3%，而75岁以上的患者发病率高达70.5%。女性受影响略多，平均发病率为26%，男性为22.6%。2015年，美国进行了370万例白内障手术，数据表明白内障手术的发病率将持续上升。
