I have problems too. I am now wearing Polorid prescription glasses that have little bifocal on the bottom. Some days they are wonderful and some days they aren't. I've come to the conclusion that the time that I take my "wonder medicines" and the time that I fly are an influencing factor on my depth perception. I always take my medicines in the morning. If I fly after 2:00 pm my depth perception is pretty good. If I wait until after 5:00pm it is much better. In the morning it is terrible. I'm 63 years old. Been flying for over 30 years.