Presbyopia 1: Why Do We Need Reading Glasses?

Presbyopia is the need for reading glasses that imposes itself on just about everyone sometime after age 40. In this video we explore how presbyopia happens. The traditional and leading theory is that the lens progressively loses flexibility, while the focusing muscles retain their ability to contract long after the lens can no longer respond.
The traditional answer is glasses (reading glasses, bifocals, progressives) or contact lenses, which work well. However, the desire to be free of optical devices has led to alternative treatments:
Video 2 covers pharmacologic (eyedrop) treatment of presbyopia.
Video 3 covers surgical treatment of presbyopia, old and new.
Video 4 is a summary of the three subject videos.
0:00 Introduction
02:02 How the Eye Focuses: Accommodation
08:52 Mechanism of Presbyopia
19:38 Reading Glasses and Bifocals
23:50 Adjustable Focus Glasses
28:06 Alternative Theories of Presbyopia

[@gth042]

Thank you for this! Thank you also for sharing references. I learn best from source-chasing.
It is a shame so much OCT data is discarded -- a lot of points to fill in.

[@assimil8or]

Great video. Very informative 👏

[@Gabriell...R]

Você é um professor excelente!
You're a great professor!

[@mleii1169]

I have a question that I'm wondering if you might know the answer to.
With regards to astigmatism, what might cause the distance to the test to change which direction the lines are blurry and clear? Close up the horizontal lines are more clear and the vertical most fuzzy, but when at a distance that is not say reading distance to perhaps a monitor and further away it's the opposite. So when further away the horizontal lines are now fuzzy yet the vertical lines are now clear. If it were the shape of my eye lens or cornea wouldn't they be the same or similar direction no matter the distance?