“How the eye works”

Today in my physics class, we learned, among other topics, how the eye works.  Before I share what I was taught, I want to show a quote from Liberman’s book (pg. 18) that I was reminded of:

I was taught that vision is a mechanical function that works just like an optical lens — a “camera” in the eye.  In my textbook, the chapter on the optics of the eye was preceded by a chapter on general optics.  First we learned how light moved through lenses and prisms, and then we applied this to the vision process.  In fact, we studied the eye as if it were a camera that just happened to be located in the head.

The book’s copyright is in 1995, so Liberman must have learned that information over 13 years ago.  Now, over a decade later in 2008, I learned the following:

  • The current chapter (Chapter 24)  we are learning from is on the combination of lenses and how light rays move through them.  Section 24.2 was on the camera.  Section 24.3 was on the eye.
  • We learned that the lens is at a fixed distance from the retina.  This is the major difference between a camera and an eye; while a camera’s focus is changed by moving the lens, an eye’s focus is changed by changing the shape of the lens.  Cameras and eyes are similar because they both have a converging (plus) lens and a film/retina that the light rays are captured on.
  • Then we learned the terms near point, far point, and the equation for the refractive power of a lens (measured in diopters).  Additionally, we learned about how light rays hit the retina in a normal eye, a myopic eye, and a hyperopic eye.

Wow, science has advanced so far in the mechanics of the eye in the past decade! 🙄 Anyway, I just thought I would share this information in case anyone wanted to know what is currently being taught on how the eyes (do not) work.

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4 thoughts on ““How the eye works”

  1. sorrisi says:

    Hi Mark! I don’t want to rain on this, but actually this theory of the lens accommodating is what has been taught for over 100 years!! Dr. Bates proved that an eye without a lens can also accommodate (focus), which means than not only can/does the lens focus, but the shape of the eye must as well. Changing the shape would then move the position of the lens closer or further from the retina depending on the elongation/shortening of the eyeball.

    His book goes into massive detail on this if you’re curious!

  2. mark825 says:

    I have read Bates’ book (twice). My post was written sarcastically because I don’t believe what I was taught; I believe what Bates said that the eye changes shape, and, therefore, the distance from the lens to the retina does change. I agree with what you said. 🙂

    The aim of my post was to point out that even in 2008, the mechanics of the eye is still taught the same exact way as it always has been (since Helmholtz “proved” his theory of accommodation).

  3. sorrisi says:

    Sorry Mark! I completely missed the sarcasm, I was a bit confused about the post…

    Will give you the benefit of the doubt next time!

    Hope you’re well,
    S

  4. mark825 says:

    That’s ok. I made a few edits to the post to try and make my intention more clear.

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