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  • Category: Science & Technology

    Correcting the eye vision using spectacles

    After the eye test an opthalmologist prescribes us spectacles or glasses and we get them from the optician shop and use for seeing the things clearly. Let us try to understand what is the basics of prescribing glasses for the eye.
    Our eye is a small ball like part in which there is a lense on the front and a screen at the back called retina. We can visualise our eye ball akin to a camera. The light from an object falls of the eye lense and then it is focused on the retina screen. As the retina is sensitive for light it feels that image and the brain comes to know about it. Sometimes what happens is that the eye ball geometry gets slightly deformed or distorted due to which the image is not properly focused on the retina screen making the image hazy and unclear.
    In such cases an outside lense in form of a spectacle is added and the combined effect of this lense and eye lense brings the image exactly on the retina screen.
    If the image was forming between the eye lense and retina wall then a concave lense is used in the spectacle and if it is formed after the retina wall then a convex lense is used to focus the image correctly.
    A person who cannot see far but can see the near things clearly is said to be suffering from myopia and is prescribed a concave lense while a person who can see the far things clearly but not the near things is said to be suffering from hypermetropia and is prescribed a convex lense for his spectacles.
    Do you wear spectacles? What type of lenses your spectacle has? Please share.
  • #25769
    We learned about lenses and vision correction by using lenses or spectacles when we studied physics in the upper primary classes under section Light.

    It was then that we learned about convex and concave lens. It was during those classes that we were taught about Myopia and Hypermetropia(Short sight and Long sight). The lessons became very practical to us then itself because there were one student with long sight and two students with short sight in our class and they were wearing relevant pecs. Though till then we were teasing them for wearing specs, after the class we stopped teasing and started supporting them better.

    I had a fancy for specs and wanted to wear specs. So I imagined some reason and told my doctor to prescribe specs, but he refused saying that I was alright and no need to wear specs.

    But later when unsolicited, I was prescribed bifocal specs (for Presbyopia)as I had entered into my forties. I am still using specs, with progressive lens.

  • #25770
    Very interesting information shared by Venkiteswaran. Yes, people having multiple vision problems are prescribed bifocal or progressive lenses. But what I was given to understand was that using bifocal lenses is a bit inconvenient and many people go for two separate spectacles - one for reading and other for driving or seeing the far objects. Is it so? Can you please throw some light on that.

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