If you are one of those aeroplane drivers whose pristine eyeballs can discern the sex of a gnat on a telephone pole as you pass it at 180 mph, inverted and pulling 7 G’s, however, squinting at an approach plate in fading light tends to strike terror in the central portion of your personal cardiovascular hydraulic system, then read on for some practical, common sense suggestions.
Your eyeballs are going to change. It is part of nature. The aging human eye looses its ability to change its focus to near objects. You can’t stop it. Forget the eyeball “strengthening exercises”, they will only cause eye muscle fatigue and discomfort (fortunately the exercises are harmless). They, along with various vitamins and ‘natural’ supplements NEVER do any lasting good because loss of near visual acuity is part of the natural aging process that we have not found a way to halt or reverse in spite of the miracles ad’s promise!
I have fit glasses for pilots for forty+ years. The FAA requirements for near vision are very liberal. You gotta see 20/20 DISTANT for First and Second class certification (either with or without glasses) but 20/40 is acceptable for near vision. If you can see 20/20 easily in the distance, each eye separately and without glasses, you do not need to go out and spend a pocket full of $$ getting “prescription” reading lenses. Wally-World, your local drug or grocery store have a whole turnstile of “cheaters” that are inexpensive, safe and FAA acceptable.
None of us AME’s are going to fuss at you if you have a pair of eyeball helpers with you as long as you can make at least 20/40 on the near vision (that’s usually about the middle row on the chart). Come on, ‘fess up, how many of you have been carrying a pair of el cheapo reading glasses in the flight bag for 2-3 years before old doc puts the “Must have available lenses for near vision” on your ticket. All that means is, they should find the glasses within 30 feet of the body when they pull you out of the twisted aluminum. The FAA doesn’t give a hoot as long as you can read the approach plates. Having a “restriction” on the medical certification for glasses is part of life, it does not make you a less qualified pilot. EVERYBODY will wear glasses sooner or later. Nope, the light bulbs are not getting dimmer. Vanity, thy name is pilot!
Now that we got that settled, let me educate you a bit and offer some practical tips on where to start. First a short course in optics. You probably do not remember but in physics 101 class the topic of how light focuses was discussed. Lenses focus light – some more than others. Lenses are “rated” by their strength or ability to bring light to a focus. A diopter is a unit of measure of lens strength. ONE diopter will bring a light beam to focus in one meter or about 39 inches. A TWO diopter lens will do the same job in one half a meter or about 19 inches, i.e., “twice” as strong. A big light bulb should have just gone on. The last time you looked at that bin of “arm shorteners” at Kmart, etc., you saw some numbers on the glasses. These are marking the strength of the glasses in diopters.
To begin with, your first pair of reading assistants will probably be about plus 1.00 to 1.50 diopters. The +1.25 is a very commonly available low end strength. When you get to be an old dude like me, your eyes will not focus up close at all and glasses must do all the work. Therefore, (here comes the second light bulb!) if I want to read something at about 18-20 inches and my eyeballs are permanently focused at infinity due to natural aging, a plus TWO diopter lens between my eyes and the book will make everything clear ! BINGO! Most people like to read a little closer and a +2.25 to 2.50 reading lens is usually quite comfortable.
As you get older, you will need increasing strength, up to +2.50 or so. There is some disadvantage to increasing strength because you reach a point where the Jepps are clear but the Kollsman window on the altimeter needs you to lean forward to see it. This situation indicates the need for “multi-focal” lenses, which I’ll discuss in a few paragraphs.
Bottom line is: If you put on one of those “dime store” reading glasses and your eyeballs say, “Thank you!” you probably are pretty close to the strength that you need. Try several different strengths while reading something at your usual working distance in the airplane. Pick the one that ‘feels good’ and the great news is: USING READING GLASSES WILL ABSOLUTELY NOT MAKE YOUR EYES CHANGE ANY FASTER OR SLOWER!
Note: I have only talked about “plus” power lenses. There are “minus” power lenses too, but that is a whole ‘nuther story. We are not going to go there.
Now that we have established that you ain’t gonna make it to age 60 without some glasses, the next question is WHAT KIND should you get? Answer: That is 100% a personal choice. They are all simply mild magnifiers.
Most first-time neophyte glasses wearers do not like the “frame” around their field of vision caused by eyewear construction. Consequently a good place to start your reading glasses experience is with a pair of ‘granny glasses’. These ‘half-eye’ glasses sit low on your nose allowing a clear field of distant vision, light weight, inexpensive, readily available and one size will fit almost everybody. If you can’t see yourself in ‘granny’ glasses they are also made in full lens versions. You just have to deal with the off/on routine. Sure, the other crewmembers will rib you, but THEIR time is coming.
What do you do if you see the panel OK but need more strength to see the approach plates? (Or vice versa.) This is more of an issue for the over 50 crowd where the eye re-focuses less and less. The instrument panel needs about +1.25 to 1.75 diopters to be in clear focus and the approach documents need about +2.00 to 2.50. Does that mean two pairs of glasses? Well, two pair would work but that would mean a lot of fiddling around when you should be flying. The magic word at this point is multi-focal lenses. There are two types: progressive (or “no-line”) and trifocals.
The eye has lost its (natural) ability to refocus from distance to intermediate (the panel) and near (the approach plate). You therefore need a lens that will do all of this. There is no simple lens made that will do all that. Before you go looking up the address for the Old Pilot’s Home hear me out.
What are “progressives”? A progressive lens (may be called “no line”, “line-less” or multi-focal) is one in which you cannot readily see the magnification change. While these are more popular with the under 50 crowd, they require very careful fitting of the glasses frame and centering of the lenses to the eyes. Most failures of the patient to “adapt” to progressive lenses is not usually due to the lenses, but to poor fitting by the technician. I’ll discuss progressive lenses more later.
What are “trifocals”? The trifocals are actually two readily seen lens segments stacked on top of each other. A weaker one positioned above a stronger one. An example would be: +1.25 over +2.50. The upper lens is usually only 7-8 millimeters or about 1/3rd of an inch high and the bottom will be ½ to 5/8th inch high. Bifocals (one segment) and trifocals are much more tolerant of fitting. If you need clear vision at two distances, they are elegantly simple, less expensive and, for the most part, easy to learn to use. Anyone who has them will tell you that, at least initially, knowing exactly where the sidewalk and steps are can be challenging.
The type of lenses you use is a personal choice. I have had pilots who wore traditional trifocals while flying and progressives the rest of the time. NOBODY likes to wear glasses when they first put them on, but if you need ‘em you’ll adapt.
So far I have been addressing the needs of the age related simple loss of the ability to focus closer than infinity. As long as you can see 20/20 distant your “cure” is simple. However, most of us will develop just a little distortion of the eyeball lens with time. This may begin to cause a bit of difficulty keeping that Chuck Yeager spot-the-bandits-at-50-miles set of eyes. Again, join the other 90% of the flying population over 50. A natural firming up of the internal lens may not take place uniformly and thus creates some slight warping or astigmatism. This will require some corrective lenses for distant vision as well. Do not despair, they make a handy framework with which to build in your above mentioned reading glasses.
At this juncture in life, you are going to get acquainted with your friendly optometrist. (Opto = light, metry= to measure). An eye exam (refraction) will determine exactly what prescription you need for distant vision. Note: all that’s needed to see more closely is to add those PLUS diopters to the bottom of your glasses. It is no more complex than that. The refraction prescription is exactly the opposite of your eye’s error so everything works out neutral, Chuck Yeager.
The current trend is to recommend PROGRESSIVE lenses. Progressive lenses work fine but there are some very definite differences from traditional bifocal/trifocal lenses. Almost everyone will learn to use and/or like them – the current acceptance rate is over 85%, or more. If your optometrist recommends progressive bifocals, make certain they will agree to remake your glasses with conventional bifocals or trifocals if you cannot “adapt” to them – adapting usually takes about three weeks. When I was dispensing glasses my experience was with the high end, brand name, progressive lenses and the satisfaction rate was almost 100%. Carole and I attended a meeting where a new type of progressive lens was introduced. This lens is made by the HOYA company and is called their "iD" lens. It is manufactured differently than all other progressive lenses. It is MUCH easier to use and quicker to adapt to. We were very impressed and have both ordered the lenses for ourselves. Consider asking for the HOYA brand lens at your eyecare source.
The careful fitting required for successful use relates to how the lenses are made. Without going into all the optics involved, they essentially increase in strength depending on how low in the lens you are looking through. In other words, if you are looking at the panel, you will be looking through a low power bifocal. When you shift your gaze to the Jepp chart, you will be looking at a closer object but through a stronger part nearer the bottom of the lens. All this without any demarcation line.
You can help the optician fit your lenses correctly in the frame if, when you pick out a frame, take it to the airplane. Sit in your usual crew position and with a sharp pointed Sharpie carefully dot across the sample lens exactly where the glare shield fits into your field of vision. None of the bifocal (or magnification area) should be above this line but it should start immediately below it. The most common problem I have “fixed” with outside prescriptions is correcting a too-low bifocal. (Ever see a customer at the grocery store tilting their head back to see a price?) This will help the optical shop place the lenses at the correct height. Discuss your occupation with your eye care professional.
Just a practical note about progressive lenses: the optical property you are looking through is very critical in width and angle. The sharply focused “field” straight ahead is narrower than a conventional bifocal (about the width of a standard 3 1/8th” panel instrument) and gets a little broader when reading printed material (about two newspaper columns wide). The areas outside these are still better than with no glasses but slightly fuzzy. This is the reason they MUST be fit accurately. We measure down to ~0.5 millimeter or about 1/32nd of an inch with an optical device.
The vision out at about 45° and down may be distorted a little. The pattern in the rug may look like it is a little wavy as you walk across it. This is a mild property of some progressives but usually is not noticed after a few days of use.
The other consideration is the narrow field of clear near vision. It will force you to point your nose at what you want to see and then tip your head back or forward to focus clearly. Once you get the hang of it, it is pretty neat to be able to focus at almost any distance from far to near. The pointing your nose and tipping your head becomes natural very quickly. The problem sometimes is that scanning the instrument panel now requires swiveling your noggin more which, of course, includes your inner ears. Most airplane drivers are not bothered by this extra head movement but in turbulence, just be aware of it.
There are a number of brands out there; I do not have a recommendation, however, in years past I have personally worn and dispensed Zeiss, Hoya, Sola, and Varilux with excellent success. Stick with a good name brand. While not inexpensive their optics are outstanding. I would tend to avoid the kiosks and “fast food” eyeglass places as their lenses frequently are made off shore. Go where you will see the same person next time you’re in. Look for a company's certification plaque on their office wall, e.g., Zeiss, Varilux, etc.
The shop you go to for glasses will probably offer you additional services, sort of like air-conditioning and cruise control in your car. Your eyeware professional will recommend a lens material, however, polycarbonate is the most common and outstanding (same stuff they make DVD's out of). I suggest you avoid glass (heavy) and plastic (scratch easily).
ALL lenses come with ultraviolet blocking “built in”, don’t pay extra for that. DO get anti-reflective coating (A/R) on BOTH sides of the lenses. Ask how the coating is applied. Vacuum coated is best. Do not accept a dipped A/R coating because it is not nearly as durable. Getting the BACK of your sunglasses lenses anti-reflective coated also will greatly reduce the reflections from your face onto the back of the lens! There is not much of any reason to not get a good anti-reflective coating on any lenses. Do inquire about the guarantee on the coating (usually two years).
Polarized sunglasses while outstanding for every day use, especially when back coated with A/R, will NOT work in pressurized air machines with laminated windscreens. If you want to try them, buy a pair of clip-on's for $15.00 but the rainbow of color in the windows will be distracting. The EFIS will black out completely and you have to tilt your head to horizontal to see it. Annoying during a 200' and ½ mile viz approach!
Need help with the overheads? Lenses are available with a mild bifocal in the top. Of course, you can take your $4.95 cheaters and put them on upside down!
If distant vision is your concern, check your eyes against one of your kids who can spot a Dairy Queen 12.8 miles down the road. See who can read the sign, billboard, or road marker first. Obviously if you tie you probably both have excellent distant vision. The same applies if you can ace the eyeball machine while getting your FAA medical. Tip: check each eye separately by covering one eye – don’t crush your eye shut with tightly clenched eyelids, that mashes your eyeball slightly out of shape temporarily and can throw off keen distant vision just a ‘skosh’.
Any questions I missed? Get in touch.