Friday, June 3, 2011

Tutorial: Optics for Optometric Instrumentation

Please answer this tutorial question;

How does the focimeter works in determining power of ophthalmic lenses? Please explain it in point form.

Due date: 12/ June/ 2011


  1. salam..

    my answer is

    -focimeter measured the back vertex power of an opthalmic lens
    - first the lens that going to be measured is put against a stop between a standard lens and afocal telescope.
    -the adjust the movable target whether to front or back in a distance x to produce a parallel ray which is neccessary at the telescope objective lens
    -focused image now is at the second focal plane of telescope and can be seen via the telescope
    -the reading at the scale at this time is the back vertex power of the opthalmic lens

  2. •Lens is placed against the stop lens between a standard lens and afocal telescope.

    •Then, the moveable target should be adjusted to get a clear image as here the ray that passes through the lens will be parallel towards the telescope.

    •Ray will pass through the eyepiece and here the examiner can determine the power of ophthalmic lenses.

    •With this optical principal of the focimeter, centre of the lens stop will falls at the anterior focal point of the standard lens and the dioptric scale is linear.



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