By: Bob Decot (1948-1994)
As we get older we experience a condition known as presbyopia, meaning “old eyes”. This is the time in our life most commonly described as “our arms not being long enough to read a newspaper or menu”. Simply put, we are not able to focus on objects close up as well as in the past. To focus on objects closer than optical infinity, we use a process known as accommodation. When we accommodate, the ciliary muscles connected to the crystalline lens inside our eye contract, thereby making the lens thicker and more curved. This increases the dioptric power of the eye and enables us to focus on closer objects.
When we are young this lens is very flexible. However after about 10 years of age there is a gradual loss of this flexibility that usually goes unnoticed until about age 40. At this point our accommodation decreases rapidly. This is the point at which we require glasses or perhaps bifocals with prescription called “plus lens power” for close work and reading. Plus lens power enables you to focus on objects closer to your eye.
Also at this time, you notice the sights on your rifle or pistol are becoming increasingly blurred. Rifle and pistol shooters need a clear sight picture. If you look at the sights through your bifocals, you notice that the sights are now sharp, however everything down range is out of focus.
It is not possible to have clear vision at both near and far simultaneously. When you were young you could look at the target and then fixate on the sights. As you age and lose accommodation this becomes more difficult. You must now substitute an optical system, i.e., a lens to make up for your lack of accommodation.
The answer to your dilemma is simple. You now require additional ‘plus lens power’ in relation to your distance prescription, the same type of power that is present in your bifocal, only less because the sights being farther than reading material. How much less? The answer is dependent on many factors: the type of shooting you are doing, the type of sights you are using, your barrel length, the range of your targets and your distance correction. Keep in mind that the more plus lens power added, the more the targets down range will be out of focus. While you have lost some of your accommodation, you still have some accommodation available.
You should make an appointment with your optometrist or ophthalmologist for a complete eye exam and refraction. Whether you wear glasses all day long or not, you can benefit from this practice. With a proper explanation of your needs the doctor will be able to give you a “shooting prescription.” This will be a prescription for a shooting and should not be used as everyday wear.
So you don’t necessarily need a second pair, Decot glasses are available with interchangeable lenses. This frame is appropriate for normal wear, and with the insertion of a single lens, your glasses may then be used for shooting. This is a very practical solution. You will have a pair of bifocal glasses for distance and reading, and with the insertion of the shooting lens for proper sight picture, the non shooting eye with your reading bifocal correction, provides you with the ability to see closer up for reloading.
Dependent on your shooting sport, some generalities can be stated. Pistol and rifle shooters require some additional plus power. Remember, plus power is the same type of power that is in your bifocals or reading glasses. For shooting you will require less power than for reading. Rifle shooters will require less additional plus power than pistol shooters, because of the rifle sights being farther from the eye than pistol sights. Younger shooters will require less plus power than the more mature shooter because they still have much of their accommodation available. Pistol shooters normally require less than half the power that is prescribed for reading. It is important to explain to your doctor that you don’t want the target to be too blurred. The more plus power added, the clearer things up close become. You don’t want to be totally corrected at arms length because the target will be excessively out of focus.
You have lost some of your accommodation, but not all. You must impress upon your doctor that you are aiming for short periods of time and wish to be able to use most of the accommodation you still have available, while keeping enough in reserve to avoid eye fatigue.
Different types of shooting will have different requirements, therefore it is important the person dispensing your glasses is knowledgeable of the various options available to you. In shooting sports where movement is required, the simplest solution is putting the shooting prescription in single vision in the lens of the aiming eye only and the normal distance correction in the lens of the non aiming eye. This will allow you to move from station to station easily and acquire the front sight quickly as well.
In shooting sports. where movement is not required, the best solution is an upside down bifocal lens, with the additional power required for shooting in the bifocal, placed slightly above the pupil. Now you have clear vision down range while moving, and need only drop your head slightly to have a clear sight picture. You must tell your optician that an important consideration here is the type of bifocal you choose. The optician can show you the types available. Bifocals have different amounts of image jump.
This means that when you move from the distance portion of the lens into the shooting correction you get a prismatic effect. This makes objects seem to be displaced or jump. To minimize this optical phenomenon it is advisable that you choose a flat top 35 style bifocal. This bifocal has a straight line dividing the distance prescription from the reading or shooting prescription. The reason for this is the optical centers on these lenses are ground close or on the bifocal segment line, minimizing image jump. Another reason for choosing one of these lenses is the wide field of view. Choosing a smaller bifocal will result in your having to search for it while trying to find a good sight picture. Bifocals of this type are available in powers from +0.75 diopters to +3.00. The requirements for a clear sight picture should be only from +0.75 to +1.25 depending upon your age, sport, and distance correction.
Our opticians at Decot Hy-Wyd will be able to fabricate a lens according to the doctors prescription to meet your needs and provide you with a frame appropriate to your needs. Frame styles and lens colors available for specific use are readily available and your Decot optician can demonstrate these options.
While some above information is technical, your optical professionals will be happy to explain any of the ideas provided here. This should provide a starting point in the quest for a good pair of shooting glasses.
For any additional information call Decot Hy-Wyd Sport Glasses Inc. 1-800-528-1901.s selecting the lens color that will give me that extra edge to make my hunt even more successful. Colors such as Gold-15 and yellow may be utilized in a multitude of different hunting applications. As well as proving useful in low light situations, I find that a yellow tint is extremely effective when hunting Quail in the high deserts of Arizona. Its’ light gathering properties illuminate those areas under trees and bushes that quail like to use to for cover. Over the years I have found my Light Target Orange and Light Medium Target Orange lenses extremely effective when hunting deer and even elk. I use these colors in the minutes just before sunrise and immediately following sunset for increased amounts of light and to offer contrast.
Other lens colors such as bronze can be very instrumental when hunting in the higher elevations and vast open wilderness of Alaska. Bronze lenses provide superior contrast between the lavish green surroundings and such large game animals as the caribou. I have found many people that prefer using a V-Lite Rose lens for hunting quail and pheasant in the mid-west. And, whether I’m fishing or just driving, there is no substitute for a pair of polarized lenses. Bronze and Target Sun Polarized lenses are a favorite for those hunters who are extremely sensitive to glare.
The professionals at Decot Hy-Wyd can answer any of your questions regarding the right lens for your hunting needs. Call 800-528-1901.