Binoculars for people who wear bifocals or have other visual needs
With practice, it’s easy for eyeglass and even bifocal wearers to use binoculars with your glasses on—after all, you don’t want to miss quick-flying birds in the second or two it takes to remove or push up your glasses. Whether you have progressive bifocals or ones with a line, or even if you have trifocals, your eyes will quickly adjust to looking through the glasses and the eyepieces to get a clear look if you match the right binoculars with the right eyewear.
Selecting the Right Binoculars: As with all glass, you lose some light through eyeglass lenses—and the problem is compounded when you have photogray or photochromic eyeglasses. So brightness is an important factor. Binoculars with a large exit pupil (at least 4, with 5 or more being optimal), give you both a brighter view and a bigger “window” to improve the chances that your eyes. In other words, if you want 7x magnification, make sure your glasses are at least 7x35. If you want 8x, make them at least 8x40. And if you want 10x, make them at least 10x50. To maximize the exit pupil while simplifying binocular use, 7x or 8x are the best magnification powers.
As is true for all eyeglass wearers, your binoculars should give you long enough eye relief to give you as big and clear an image as you’d get without glasses. You can tell how long the eye relief is by looking at the size of the eyecups--the longer they are, the farther from the eye the binoculars should be. Your binoculars should have eye relief comparable to how far from your eyes your eyeglasses will hold them: Thick glass lenses in heavy frames will require binoculars with longer eye relief than thinner plastic lenses in small frames.
Selecting the Right Eyeglasses: Clear eyeglasses with full UV protection give your eyes great protection from the sun while not compromising your birding vision. If you need additional protection from bright sunlight, try using a wide-brim hat. If you must resort to sunglasses when birding, it's better to have prescription sunglasses than clip-ons or the thick ones that are worn over eyeglasses.
The whole point of eyeglasses, be they standard, binocular, or trifocal, is to give you good vision. Once you and your eye doctor have chosen the best prescription for you, choose frames that are relatively close-fitting. These will allow you to hold the binoculars reasonably close to your eyes. Whether you go with plastic or glass lenses, make sure they are guaranteed against scratching.
If you are buying standard bifocals, ask that the line be set as low as possible, so you can get as much of the magnified picture as possible through the upper lens. If you need bifocals, don't wear just distance glasses for birding--you won't be able to take field notes or consult a field guide without the lower bifocal lens.
Using Binoculars with Glasses: First, make sure the eyecups are in the down position. If the eyecups are extended, the binoculars will be too far from the eyes for the optimal eye relief, and your view through the binoculars will be significantly smaller than it should be. When properly selected, you should get your largest, best view when the binoculars are held directly against the eyeglass lenses.
Practice looking at non-moving objects in the house or yard, and after a few tries your eyes will automatically look through the eyepiece at the right spot for your glasses. If you wear bifocals, practice pulling up your binoculars so you get as much of the view as possible through the upper section of the bifocals.
Binoculars for Those with Special Vision Needs: People with cataracts, macular degeneration, and other vision problems may find binoculars a godsend. Binoculars magnify light as well as the size of the image, and those with a large exit pupil may brighten your view considerably. Select a pair with low magnification and good close focusing for indoor use. The Leupold Wind River Katmai 6x32 was the top-rated birding binocular in the mid-price class as rated by the Cornell Laboratory of Ornithology in The Living Bird, Winter 2005. With the low magnification and high exit pupil, this pair could be ideal for a great many birders and others with special vision needs.
~ Laura Erickson