Tears: How I Miss Thee!
Tears are an integral part of vision. When eyes get dry, vision
worsens. This is an obviously important concept for pilots
especially making an approach after a long flight.
Dry eyes have many causes but the one most common in aviation is altitude. As we ascend, the relative humidity decreases and our eyes tend to dry out. This occurs in unpressurized aircraft and even more in pressurized aircraft since pressurization removes water vapor. As our tears dry out, their coating over the cornea of the eye changes which affects our vision. This coating is an integral part of our eye’s focusing system.
Tears are composed of three substancesoil, water, and mucous. The outer layer is an oily one that is secreted by meibomian glands which are located on the edge of your eyelids. These are the glands that cause styes when they get plugged up. The water layer is from the lacrimal glands and is the middle, thicker layer of the tear. The bottom layer which spreads the tear evenly across the eye is the mucus layer.
Decreased humidity will cause evaporation of the water and mucous layer which then will affect vision. Certain medications will increase the dryness such as birth control pills, diuretics and ACE inhibitors used to treat blood pressure, and antihistamines/decongestants. Underlying conditions can also increase dryness such as being over 40 (Is that a condition!?), menopause, arthritis, diabetes, and Vitamin A deficiency. Previous Lasik eye surgery can also cause dryness.
There are ways to help prevent dry eyes and the visual changes associated with dry eyes. Staying hydrated is very important not only for dry eyes but a multitude of reasons. Also, avoid rubbing the eyes as this can irritate the lacrimal glands and decrease their output of the watery portion of the tear.
Flax seed oil, in capsules or liquid, when taken on a regular basis, can also increase eye lubrication. Omega 3 oils in supplements and fish like salmon will also help increase production of the oil component of the tear but it must be an ongoing part of ones diet.
Regardless of prevention, on long flights eyes will get dry. I keep a supply of artificial tears in the plane and will put them in my eyes about 15 minutes before descent to make sure my vision is the best it can be (although it does take away one of my excuses for hard landings). I prefer the unit dose artificial tears because they do not have preservatives and avoid the contamination that can occur with multidose bottles.
Do not use Visine or other constricting eye drops (e.g. get the red out). These are bad for your eyes in general and actual make the eye drier by causing constriction of blood vessels.
While we are on the subject of eyes, sun protection should be mandatory for all pilots and passengers. There are multiple brands and lots of personal choices but the major importance is protection from ultraviolet radiation. This is not just a comfort issue but can protect the eye from developing cataracts which can be promoted by bright sunlight. Sunglasses should be marked as filtering 99% of ultraviolet radiation.
Polarizing sunglasses are not particularly good for pilots because they cause difficulty with certain types of displays. If you are looking for a cheap but good quality lenses (and there are lots of bad quality lenses out there), American made safety work glasses sold in hardware stores are the best value out there. Make sure to look for American made because the foreign made lenses are not reliable.
You can judge the quality of a lens by looking at something square like a ceiling tile. Close one eye and hold the lens out from the open eye. Move the lens slowly up and down and side to side. Good lenses will keep the square’s borders straight. If the line moves or gets wavy during the motion, look for another pair.
Dry eyes have many causes but the one most common in aviation is altitude. As we ascend, the relative humidity decreases and our eyes tend to dry out. This occurs in unpressurized aircraft and even more in pressurized aircraft since pressurization removes water vapor. As our tears dry out, their coating over the cornea of the eye changes which affects our vision. This coating is an integral part of our eye’s focusing system.
Tears are composed of three substancesoil, water, and mucous. The outer layer is an oily one that is secreted by meibomian glands which are located on the edge of your eyelids. These are the glands that cause styes when they get plugged up. The water layer is from the lacrimal glands and is the middle, thicker layer of the tear. The bottom layer which spreads the tear evenly across the eye is the mucus layer.
Decreased humidity will cause evaporation of the water and mucous layer which then will affect vision. Certain medications will increase the dryness such as birth control pills, diuretics and ACE inhibitors used to treat blood pressure, and antihistamines/decongestants. Underlying conditions can also increase dryness such as being over 40 (Is that a condition!?), menopause, arthritis, diabetes, and Vitamin A deficiency. Previous Lasik eye surgery can also cause dryness.
There are ways to help prevent dry eyes and the visual changes associated with dry eyes. Staying hydrated is very important not only for dry eyes but a multitude of reasons. Also, avoid rubbing the eyes as this can irritate the lacrimal glands and decrease their output of the watery portion of the tear.
Flax seed oil, in capsules or liquid, when taken on a regular basis, can also increase eye lubrication. Omega 3 oils in supplements and fish like salmon will also help increase production of the oil component of the tear but it must be an ongoing part of ones diet.
Regardless of prevention, on long flights eyes will get dry. I keep a supply of artificial tears in the plane and will put them in my eyes about 15 minutes before descent to make sure my vision is the best it can be (although it does take away one of my excuses for hard landings). I prefer the unit dose artificial tears because they do not have preservatives and avoid the contamination that can occur with multidose bottles.
Do not use Visine or other constricting eye drops (e.g. get the red out). These are bad for your eyes in general and actual make the eye drier by causing constriction of blood vessels.
While we are on the subject of eyes, sun protection should be mandatory for all pilots and passengers. There are multiple brands and lots of personal choices but the major importance is protection from ultraviolet radiation. This is not just a comfort issue but can protect the eye from developing cataracts which can be promoted by bright sunlight. Sunglasses should be marked as filtering 99% of ultraviolet radiation.
Polarizing sunglasses are not particularly good for pilots because they cause difficulty with certain types of displays. If you are looking for a cheap but good quality lenses (and there are lots of bad quality lenses out there), American made safety work glasses sold in hardware stores are the best value out there. Make sure to look for American made because the foreign made lenses are not reliable.
You can judge the quality of a lens by looking at something square like a ceiling tile. Close one eye and hold the lens out from the open eye. Move the lens slowly up and down and side to side. Good lenses will keep the square’s borders straight. If the line moves or gets wavy during the motion, look for another pair.
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