For many people past the age of 40, focusing on close objects -- restaurant menus, for instance -- just gets harder and harder.

Most people with this condition, called presbyopia, eventually give in and get reading glasses, bifocals or glasses with progressive lenses.

But what if there were another alternative that didn't require people to carry an extra set of glasses or have only part of their field of vision in focus at any one time?

Zoom Focus Eyewear LLC, of Van Nuys, Calif., has just such an option, and with it won this year's Silver Innovation Award. The solution: eyeglasses, called TruFocals, that the wearer can manually adjust to give clear, undistorted vision whether reading a book, working on a computer or looking into the distance.

The judges praised the potential large-scale benefit of TruFocals. Richard S. Lang, one of the judges and a physician at the Cleveland Clinic, called the technology a paradigm shift in the way it addresses a problem 'that has been handled the same way for many years.'

For more than 100 years, researchers have tried to come up with adjustable eyeglasses; a Baltimore inventor filed a patent on the idea in 1866. But a workable product that's easy to adjust, thin, lightweight and accurate proved elusive.

Stephen Kurtin, a California inventor who previously devised one of the first word-processing programs, turned to the problem in the early 1990s. His solution, TruFocal eyeglasses, mimic the way that the lens of the human eye stretches and contracts to adjust focus.

Each TruFocal lens is actually a set of two lenses: an outer lens, and an inner lens made of a flat glass plate attached to a flexiblemembrane that contains a clear, silicone-based liquid. A manual slider on the bridge of the eyeglasses adjusts the focus by changing the shape of the membrane. The outer lens can be custom made to correct other vision problems besides presbyopia, including nearsightedness and astigmatism.

Once the TruFocal lenses are adjusted, the entire field of vision is in focus, unlike bifocals and progressive lenses, which keep only a limited area in sharp focus. So a user can adjust the glasses to focus only on the book he's reading, then look up and readjust them to focus solely on the TV across the room.

There were some false starts along the way. Mr. Kurtin considered using liquid-crystal electronics to adjust the focus, but the batteries proved problematic. The first model weighed seven pounds. But after nearly 20 years of refinements, the first TruFocal glasses were introduced in 2009.

There's a downside for the fashion conscious: The glasses come in one shape -- round -- and have been compared to the spectacles worn by Harry Potter. (They are sold in several colors, though.) The circular lenses are necessary to the workings of the technology; with any other shape, the flexiblemembrane couldn't keep a spherical shape when compressed.

TruFocals aren't the only glasses with adjustable lenses. But other products are mainly designed for users in the developing world, where optometrists aren't widely available; they are meant to be adjusted once by the user to correct the focus at a given distance and then set that way. The Zoom Focus product is aimed at wearers who want to make constantadjustments in their vision.

Michael Totty

• restaurant [´restərɔnt] n.饭店，菜馆 (初中英语单词)
• instance [´instəns] n.例子，实例，例证 (初中英语单词)
• reading [´ri:diŋ] n.(阅)读；朗读；读物 (初中英语单词)
• vision [´viʒən] n.视觉；想象力；幻影 (初中英语单词)
• solution [sə´lu:ʃən] n.解答；解决；溶解 (初中英语单词)
• adjust [ə´dʒʌst] vt.调整；校准；使适应 (初中英语单词)
• working [´wə:kiŋ] a.工人的；劳动的 (初中英语单词)
• computer [kəm´pju:tə] n.计算机；电子计算器 (初中英语单词)
• physician [fi´ziʃən] n.(内科)医生 (初中英语单词)
• patent [´peitənt, ´pæ-] a.专利的 n.专利品 (初中英语单词)
• accurate [´ækjurət] a.准确的；精密的 (初中英语单词)
• california [,kæli´fɔ:njə] n.加利福尼亚 (初中英语单词)
• actually [´æktʃuəli] ad.事实上；实际上 (初中英语单词)
• liquid [´likwid] n.液体 a.流动的 (初中英语单词)
• unlike [,ʌn´laik] a.不同的 prep.不象... (初中英语单词)
• conscious [´kɔnʃəs] a.意识的；自觉的 (初中英语单词)
• circular [´sə:kjulə] a.圆形的 n.通知 (初中英语单词)
• mainly [´meinli] ad.主要地；大体上 (初中英语单词)
• available [ə´veiləbəl] a.可用的；有效的 (初中英语单词)
• constant [´kɔnstənt] a.坚定的；坚贞的 (初中英语单词)
• progressive [prə´gresiv] a.进步的；前进的 (高中英语单词)
• potential [pə´tenʃəl] n.&a.潜在的；可能的 (高中英语单词)
• baltimore [´bɔ:ltimɔ:] n.巴尔的摩 (高中英语单词)
• inventor [in´ventə] n.发明者 (高中英语单词)
• previously [´pri:viəsli] ad.预先；以前 (高中英语单词)
• limited [´limitid] a.有限(制)的 (高中英语单词)
• solely [´səulli] ad.唯一；单独；完全 (高中英语单词)
• eventually [i´ventʃuəli] ad.最后，终于 (英语四级单词)
• alternative [ɔ:l´tə:nətiv] a.二中选一的 n.选择 (英语四级单词)
• flexible [´fleksəbəl] a.灵活的，柔韧的 (英语四级单词)
• membrane [´membrein] n.膜(片)；薄膜；隔膜 (英语四级单词)
• manual [´mænjuəl] a.用手(操作)的 n.手册 (英语四级单词)
• bridge [bridʒ] n.桥(梁)；鼻梁；桥牌 (英语四级单词)
• innovation [,inə´veiʃən] n.改革；革新；创新 (英语六级单词)