In Your Eyes: What They Reveal About Your Health
来源：华尔街日报    2012-08-24

        As an ophthalmologist, David Ingvoldstad sees much more about his patients' health than just their eyes. Thanks to the clues the eyes provide, he regularly alerts patients to possible autoimmune diseases like rheumatoid arthritis and lupus, monitors progression of their diabetes and once even suspected -- correctly, as it turned out -- that a patient had a brain tumor on the basis of the pattern of her vision changes.         
        Because the body's systems are interconnected, changes in the eye can reflect those in the vascular, nervous and immune system, among others. And because the eyes are see-through in a way other organs aren't, they offer a unique glimpse into the body. Blood vessels, nerves and tissue can all be viewed directly through the eye with specialized equipment.       
        With regular monitoring, eye doctors can be the first to spot certain medical conditions and can usher patients for further evaluation, potentially leading to earlier diagnosis and treatment. Clots in the tiny blood vessels of the retina can signal a risk for stroke, for example, and thickened blood-vessel walls along with narrowing of the vessels can signal high blood pressure. In some cases, examining the eye can help confirm some of the diagnoses or help differentiate disorders from each other.        
        'There's no question the eye has always been the window to the body,' says Emily Chew, deputy director of the epidemiology division at the National Eye Institute. She adds, 'Anybody with any visual changes . . . should be seeing someone right away.'         
        Scientists are working to advance their knowledge of what the eye can reveal about diseases. For instance, researchers are studying how dark spots on the back of the eye known as CHRPE, or congenital hypertrophy of the retinal pigment epithelium, are associated with certain forms of colon cancer, and how dementia-related changes are signaled in the eye, such as how the eye reacts to light. Other scientists, like Dr. Chew, are studying how to keep the eye healthier for longer, which could be good for the health of the eye as well as the rest of the body.        
        Companies are building enhanced technology that allow for better viewing of the eye. Scotland-based Optos, for example, created a machine that allows for better screening of the periphery of the retina. The machines can now be found in doctors' offices and research clinics. Instead of the typical 30-degree view of the eye, it offers a 200-degree view. Being able to see more of the periphery could mean earlier or more accurate diagnosis of various diseases and may also be coupled with intervention tools to improve treatment. Optos is currently funding a study of the use of retinal imaging to diagnose heart disease, according to Anne Marie Cairns, head of its clinical development.        
        The eye's job is to deliver vision by converting incoming light information into messages that the brain can understand. But problems in vision can indicate a problem outside of the eye itself.          
        One critical structure in the eye is the retina, which allows us to experience vision. It is made of brain tissue and contains many blood vessels. Changes in vessels in other parts of the body are reflected in the retina as well, sometimes more noticeably or sooner than elsewhere in the body.         
        The eyes can help predict stroke risk, particularly important to people with heart disease and other stroke risk factors. That is because blood clots in the arteries of the neck and head that might lead to stroke are often visible as retinal emboli, or clots, in the tiny blood vessels of the eye, according to the National Eye Institute.           
        The immune system's interaction with the eyes can be telling, too, yielding information about autoimmune diseases or infections in the rest of the body. Sometimes eye symptoms may appear before others, like joint pain, in patients.         
        For instance, inflammation in the optic nerve can signal problems in an otherwise healthy, young person. Along with decreased vision and sometimes pain, it can suggest multiple sclerosis. If the optic disc, a portion of the optic nerve, is swollen, and the patient has symmetrical decreased field of vision, such as a decreased right visual field in both eyes, they may need an evaluation for a brain tumor -- a rare circumstance.         
        If immune cells like white blood cells are seen floating in the vitreous of the eye, it could signal a local eye infection or one that is spread throughout the body.           
        Diabetes is one disease that can cause major changes in the eye. In diabetic retinopathy, a common cause of blindness, blood vessels hemorrhage and leak blood and fluid. When blood vessels don't function properly, they can potentially cause eye tissue to be deprived of oxygen and to die, leaving permanent vision damage.        
        Also, in diabetic patients additional blood vessels may grow in the eye, anchoring themselves into the sticky gel known as the vitreous, which fills a cavity near the retina. This condition can cause further problems if the retina tears when it tries to separate from the vitreous -- a common occurrence as people age -- but is tangled by growth of new blood vessels.         
        Usually diabetic patients who come in for eye exams already know they have the disease, and the primary purpose of an eye exam is to make sure they don't have diabetic retinopathy or, if they did have it, that the condition hasn't progressed, say eye doctors like Dr. Ingvoldstad, a private practitioner at Midwest Eye Care in Omaha, Neb. But once in a while there is a patient who has noticed vision changes but didn't realize he or she had diabetes until alerted during an eye exam that there were signs of the eye disease that is consistent with the condition, he says.           
        The American Academy of Ophthalmology recommends eye examinations whenever individuals notice any vision changes or injury. Adults with no symptoms or known risk factors for eye disease should get a base line exam by age 40 and return every two to four years for evaluations until their mid-50s. From 55 to 64, the AAO recommends exams every one to three years, and every one to two years for those 65 and older.         

　　戴维•英沃斯塔德（David Ingvoldstad）是内布拉斯加州奥马哈市（Omaha）Midwest Eye Care的私人执业医师，身为眼科医生，他从病人身上看到的健康问题远远不止眼睛本身。根据眼睛提供的线索，他会经常提醒病人注意风湿性关节炎和狼疮等可能患上的自身免疫系统疾病，监测糖尿病进程，他甚至曾经根据一位病人的视力变化模式怀疑她患上脑肿瘤──结果证明他的怀疑是正确的。 

　　由于人体系统是相互关联的，因此眼睛的病变可以反映出血管、神经和免疫系统等处的病变。由于眼睛在某种程度上是透明的，而其它器官则不是，因此通过眼睛可以从一个独特的视角了解身体简况。借助专用设备，血管、神经和组织都可以通过眼睛进行直接观察。 

　　使用常规监测，眼科医生可能是第一个发现某些健康问题的人，并能引导病人进行进一步检查，这可以帮助病人提前诊断和治疗。例如，视网膜毛细血管中的凝块表明可能存在中风危险，而血管壁增厚连同血管变窄表明可能有高血压。在某些情况下，眼科检查可以帮助确诊某些疾病，或帮助区分不同的病症。 

　　美国国家眼科研究所（National Eye Institute）流行病学部副主任埃米莉•周（Emily Chew）说，“毫无疑问，眼睛一直是身体的窗户。”她补充说，“任何视觉发生变化的人……都应该马上看医生。” 

　　科学家们正在努力增进对眼睛所能揭示的疾病的了解。例如，研究人员正在研究眼球后部被称为CHRPE（即先天性视网膜色素上皮细胞肥大）的黑斑与某些类型的结肠癌的关系，以及与痴呆症相关的病变在眼睛中的征兆，例如眼睛对光线的反应。也有些科学家，例如周博士，正在研究如何更长久地保持眼睛健康，这对眼睛健康和身体其他部分的健康都有好处。 

　　许多公司正在开发更高级的技术，以更好地检查眼睛。例如，苏格兰的Optos公司发明了一种机器，它可以更好地扫描视网膜边缘。现在，医生诊室和临床研究诊室中都能看到这种机器。它提供了200度视野，而不是通常的30度视野。可以看到更多边缘意味着能更早或更准确地诊断各种疾病，并可以与干预工具共同使用以提高治疗效果。据Optos临床开发部主任安妮•玛丽•凯恩斯（Anne Marie Cairns）称，该公司目前正投资开展一项使用视网膜成像技术诊断心脏病的研究。 

　　眼睛的功能是将入射光信息转化为大脑能理解的讯号，从而产生视觉。但视觉问题可能显示出眼睛本身以外的问题。

　　眼睛的一个关键结构是视网膜，它让我们能够体验视觉。它是由脑组织构成的，并包含许多血管。人体其它部位的血管病变也反映在视网膜中，有时比身体任何其它部位都更明显或更早。 

　　眼睛可以帮助预测中风风险，这对有心脏病和其他中风风险因素的人尤为重要。据美国国家眼科研究所称，这是因为颈部和头部动脉中可能导致中风的血块通常会在眼睛的毛细血管中显现为可以看到的视网膜栓塞或凝块。

　　从免疫系统与眼睛的相互影响中也可以得出关于身体其他部分自身免疫系统疾病或感染的信息。有时，眼科症状可能在病人出现其他症状（例如关节疼痛）之前显现出来。 

　　例如，视神经发炎可能表明其他方面健康的年轻人身体出了问题。视力减退且眼睛时而疼痛可能表明患有多发性硬化。如果视神经盘──视神经的一部分──肿大，且病人有对称视野缩小，例如双眼右视野缩小，那么他们可能需要检查是否有脑肿瘤──这是一种罕见的情况。 
如果在眼球玻璃体中看到漂浮的白血球等免疫细胞，那么可能表明存在局部眼球感染，或者遍布全身的感染。
　　糖尿病是一种可能导致重大眼睛病变的疾病。在糖尿病视网膜病变这种常见的致盲疾病中，血管会出血并渗出血液和液体。当血管无法正常发挥功能时，可能导致眼组织缺氧并死亡，造成永久性视力损伤。 

　　而且，糖尿病病人的眼睛还会有血管增生，这些血管将缠在玻璃体（粘稠的胶状物，充满于视网膜旁的空腔体里）中。当视网膜和玻璃体要分离──人们年老时常会发生的情况──但被长出的新血管缠住时，视网膜会破裂，导致更多的问题。

英沃斯塔德等眼科医生说，通常，进行眼科检查的糖尿病病人已经知道他们有病，而眼科检查的主要目的是确保他们没有糖尿病视网膜病变，或者当他们患上这种疾病时，确保情况没有恶化。但他说，偶尔会有病人出现明显的视力变化，但没有意识到自己有糖尿病，直到在眼科检查中被警告出现了与这种病症一致的眼科疾病迹象。

　　美国眼科学会（American Academy of Ophthalmology）建议，只要发现任何视力变化或损伤，就应进行眼科检查。没有眼科疾病症状或已知风险因素的成年人应在40岁时进行基础检查，且每2-4年进行一次复查，直到55岁左右。对于55岁到64岁的人，美国眼科学会建议每1-3年进行一次检查，对于65岁以上的人，美国眼科学会建议每1-2年进行一次检查。