长期以来，人们只知道糖尿病和可能会损害视力的糖尿病性视网膜病变之间存在联系，但现在还有一种严重的眼部疾病－青光眼，似乎也是它的一个并发症。

青光眼

　　《眼科学》杂志一项最新的研究显示：与没有糖尿病的妇女相比，患有糖尿病的妇女患原发性开角型青光眼（一种最常见的青光眼）的几率要高出70%。

    这篇文章的主要作者，哈佛眼科学助理教授Louis Pasquale博士说：“研究显示2型糖尿病病人更容易患青光眼。”

    据美国国家眼病研究所称，美国现在有2，000，000的原发性开角型青光眼患者，现已成为导致失明的主要原因之一。
　　但糖尿病和青光眼之间的联系还没有被最终证明。

　　匹兹堡大学医学院眼科学院院长，UPMC眼科中心主任Joel Schuman博士说：“很多疾病，像糖尿病，似乎已经成为很多人口研究中的一个危险性问题了，但是糖尿病和青光眼之间是否真正存在联系，现在还不能确定。”

　　还有一篇发表在《眼科学》杂志上的文章在对荷兰的4，000人进行了研究，结果未能证实两者之间存在联系。

　　但是，Pasquale的研究规模显然要大得多，共有76，000名妇女参加了这个长达20年的护士健康研究项目。而且现在的数据足以向美国糖尿病协会证明糖尿病人更容易患青光眼。

　 当眼内的液体压力超过正常范围之后，就会发生青光眼。它可以破坏视神经，导致视力缺失甚至失明。早期发现，早期治疗可以防止严重视力缺失。现在，美国有50，000，000人有可能因为青光眼而导致视力缺失。

　　Schuman称糖尿病可以通过多种途径导致青光眼。一种是造成眼内压的增高。而且，他说，糖尿病还可以让视神经变得更容易受到破坏。

　　他说，现在人们已经知道还有一种青光眼—新生血管性青光眼，和糖尿病有直接联系。这种类型的青光眼，由于提供视网膜的氧量会减少，所以视网膜会发出信号要求获得更多的氧气以及生成更多的血管。当这些新血管产生之后，它们就会形成疤痕，阻塞眼睛正常的引流系统，最终导致眼内压力增高。

　　糖尿病患者保护眼睛最重要的措施就是定期检查，Schuman说。青光眼的早期症状一般并不明显。　　　　糖尿病专家，芝加哥西北纪念医院的David Oyer医生建议糖尿病人应该每年都要找眼科医生去做一次检查，以排除是否患有青光眼或是其他严重的与糖尿病相关的眼部疾病。

　　“减少并发症产生的最重要措施就是设法减低餐前，餐后的血糖水平，”Oyer说。他建议每3到6个就要检查一次A1C水平，而且尽量将值降到7以下，最好低于6.5。美国糖尿病协会称，A1C（即糖化血红蛋白，或HbA1c）可以为患者提供过去2到3三个月平均血糖控制的大体状况。

　　Schuman接着说，经常性的锻炼也许会有所帮助，“就像对身体的其它部分一样，锻炼对眼睛也有好处。经常性的、充分的锻炼可以降低眼内压，而且还可以改善眼睛的血液循环，”他说。

Diabetes Seems to Heighten Glaucoma Risk

While diabetes has long been associated with the potentially sight-stealing disease diabetic retinopathy, it appears that another serious eye disease -- glaucoma -- may also be a complication of the metabolic disorder.

A　recent study in the journal Ophthalmology found that women with diabetes have about a 70 percent increased risk of developing the most common form of glaucoma -- primary open-angle glaucoma -- compared to women without diabetes.

"The study supports the notion that type 2 diabetes is associated with an increased risk of glaucoma," study lead author Dr. Louis Pasquale, co-director of the glaucoma service at the Massachusetts Eye and Ear Infirmary and an assistant professor of ophthalmology at Harvard Medical School, said in a prepared statement.

Primary open-angle glaucoma affects an estimated 2 million Americans, according to the U.S. National Eye Institute, and it is one of the leading causes of blindness.

Yet the link between diabetes and glaucoma hasn't been proven conclusively.

"There are a number of things, like diabetes, that appear to be a risk factor in a lot of population studies, but the association between diabetes and glaucoma is somewhat controversial," explained Dr. Joel Schuman, chairman of the department of ophthalmology at the University of Pittsburgh School of Medicine and Medical Center, and the director of the UPMC Eye Center.

Another study, also published in Ophthalmology, failed to find a link between diabetes and glaucoma in a trial that included almost 4,000 people from the Netherlands.

But, Pasquale's study was significantly larger, including more than 76,000 women enrolled in the 20-year-long Nurses' Health Study. And, the available evidence is convincing enough for the American Diabetes Association to conclude that the risk of glaucoma is increased in people with diabetes.

Glaucoma occurs when there's a gradual increase in the normal fluid pressure inside the eyes. This causes damage to the optic nerve, resulting in vision loss and blindness. Early detection and treatment can help prevent serious vision loss. About 50 million Americans are at risk for vision loss from glaucoma.

Schuman said there are a number of ways that diabetes could increase the risk of glaucoma. One way is by causing elevation in pressure within the eye. Or it's possible, he said, that diabetes could increase the susceptibility of the optic nerve to damage.

He said there's also one form of glaucoma that's known to be directly related to diabetes -- neovascular glaucoma. In this type of glaucoma, there's a reduction of oxygen supply to the retina, which causes the retina to send out signals for more oxygen and for new blood vessels to form. When these new blood vessels form, they cause scarring and block the normal drainage system in the eye, causing pressure to build up in the eye.

The most important thing someone with diabetes can do to protect their eyes is to get regular eye exams, Schuman said. Glaucoma generally has no early symptoms.

"There's no way to detect glaucoma without an exam, and the only way to prevent the loss of vision from glaucoma is to treat the disease early. You can't get back nerve damage that's been lost," he said.

Diabetes specialist Dr. David Oyer, of Northwestern Memorial Hospital in Chicago, said he recommends that people with diabetes have their eyes checked once a year by an ophthalmologist for glaucoma and other serious eye diseases associated with diabetes.

"The most important thing for reducing your risk of complications is to keep your blood sugar down both pre- and post-meal," Oyer said. He also recommends getting your A1C level checked every three to six months and keeping that number below seven, preferably below 6.5. A test of A1C (also known as glycated hemoglobin, or HbA1c) provides a snapshot of your average blood glucose control for the past two to three months, according to the American Diabetes Association.

Schuman also said regular exercise might help. "Exercise is good for the eye, just as it is for the rest of the body. Regular, vigorous exercise does lower eye pressure and probably affects circulation to the eye," he said.