Fonda G E
Saint Barnabas Low Vision Center, West Orange, NJ 07052.
Ophthalmology. 1989 Sep;Suppl:1-5. doi: 10.1016/s0161-6420(89)32984-8.
Visolett nonfocusable magnifiers are optically designed paperweights. The general magnification is 1.8X, and 4X through the bifocal. Using glass index 1.806, the general magnification is 2.47X. A Visolett is one of the most useful nonspectacle magnifiers because it diffusely concentrates the illumination on the field of vision, complementing the magnification. The optics differ from hand-held and stand magnifiers, in that the magnification does not increase with the dioptric power. However, the magnification of the bifocal does increase with the dioptric power and by decreasing the distance of the object from the focal point. The advantages are that they are simple to use, allow binocular vision, and almost double the magnification when used with a spectacle magnifier. Visoletts are preferred to stand magnifiers.
维索莱特不可聚焦放大镜是经过光学设计的镇纸。一般放大倍数为1.8倍，通过双焦点部分放大倍数为4倍。使用折射率为1.806的玻璃时，一般放大倍数为2.47倍。维索莱特是最有用的非眼镜式放大镜之一，因为它能将光线漫射到视野上，与放大功能相辅相成。其光学原理与手持放大镜和台式放大镜不同，即放大倍数不会随屈光度增加而增大。然而，双焦点部分的放大倍数会随屈光度增加以及物体与焦点距离的减小而增大。其优点是使用简单，可实现双眼视觉，与眼镜式放大镜配合使用时放大倍数几乎能翻倍。相较于台式放大镜，维索莱特更受青睐。
