Vision Matters – the pilot’s eye test

When you think of a flight medical, one of the first things that pops into your head must surely be the eye test. It certainly was one of the most limiting requirements during the pioneering days of aviation, when the need for glasses was deemed cause for disqualification.

Visual standards

While many air forces still avoid initial candidates who don’t have 20/20 vision, thankfully this hasn’t been the case for civilian pilots for many years.

For the aspiring pilots out there, I want to state that there is no published limit as to how bad your eyesight may be, provided you are able to meet the corrected standard. Quite poor, uncorrected  vision will, however, be subject to an eye specialist report and possibly the wearing of contact lenses.

Vision deterioration over time

The point of this article isn’t really to talk about initial certification, but to draw awareness to your eyesight later in your flying career as the eyes change. And boy, do they change!

When you’re born, your eyes have a range of about 14 dioptres. A dioptre is a measurement of the optical power of a lens, based on some clever maths. Suffice to say, 14 is a lot.

By the time you reach the age of 45, this number has dropped to about four diopter. The ability to focus nearby or ‘accommodate’ becomes severely restricted after that. This is due to the lens in the eye progressively losing its elasticity. We call this “presbyopia”, literally meaning “old eyes”.

In the seventh decade, due to further lens changes, the eyes also become somewhat myopic or near-sighted, firmly cementing one in the “brille” and “pille” phase!

All this naturally results in some humorous, albeit potentially serious repercussions for the flight medical and safe operation of an aircraft.

Near, intermediate and far vision acuity

Many pilots, especially those who started off with pretty good visual acuity, will put up a considerable fight in their attempt to pass the near-vision test without reading glasses.

It is important to note that even though one may still be able to just about scrape through the required level, without at least a third of available accommodation in reserve, the eyes will quickly become strained.

It’s also worth mentioning that, while you may meet the standard in the examination room, all humans  have a degree of myopia at night.

This means that your real world performance in a dark cockpit may not necessarily be up to scratch. Although I’m often reminded that iPad screens can zoom nicely, quick-reference handbooks and emergency checklists on paper do not!

The current regulations require the AME to assess not only the far and near visual acuity, but also for the intermediate acuity, which is basically the distance to your instrumentation. The concern is that glasses that correct for both distance and near vision, may create a ‘dead spot’ where there is an area of poor correction.

I’ve had pilots attempting to use three different pairs of spectacles to get through the eye test! Although meeting the individual requirements, this is clearly not a suitable solution. Imagine flicking between different pairs as you are busy hand flying an ILS approach!  

Discussions with your optometrist

It’s important to let your optometrist know that you are a pilot and to select a frame that is big enough to allow enough space for all the required corrections.

While talking about optometrists, I should also mention that sometimes they will elect to correct the one eye for distance and the other for near vision. This is an especially popular configuration for older contact lens wearers.  

This is not an acceptable approach for pilots, as the one eye will be quite myopic and the field of vision will be hampered.

Insurance considerations

Lastly, I would like to add that if you are restricted to flying with reading glasses but don’t need them practically (I’m specifically addressing the crop sprayer and aerobatic pilots), please don’t forget to still carry them on your person. Failure to do so exposes you to all sorts of  liabilities and lack of insurance cover if there is an incident.

In summary, although it may be possible to meet the minimum requirements for visual acuity, this doesn’t necessarily mean that you have the optimal or most comfortable solution.

It is well worth spending a bit of time and effort finding something that works well. At the very least, you won’t have an AME rolling his or her eyes at you!