Most times I drive without sunglasses. Not so these last several days. A sun almost overhead in Tucson and 90+ degree temps, every last bit of moisture in the air is removed. There is little moisture in the air to soften the sun rays. Or perhaps it isn't the moisture at all, but the sun rays reflecting from every light colored surface that causes eye strain.
With a wide brimmed hat and less reflection on the hiking trails, my eye sight is not bothered.
When driving and not hiking, my eyes are strained from the intensity of the sun. Back to wearing sunglasses when driving -- especially during the middle day light hours.