How does an optician arrive at the correct power of a lens to improve eye sight.?

Question

i.e.how does he precisely calculate the power of our spectacle lenses.

Answer 1

function of optima

Answer 2

The obvious and best-known method is refined trial and error, asking the clssic "better or worse?" questions of the person in the chair.  This doesn't depend on any single answer but is a cross-checked procedure, and there are refinememts such as the use of a duochrome (read and green target to help decide the final balance of an Rx.

The other route needs no information from the subject, but relies on examining and analysing the movement of light reflected from the back of eye.  This can be done by a computerised auto-refractor or by a hand-held simple retinoscope, the examiner's brain providing the computing power. (With a straightforward eye, the computer is as good as me, and a lot faster.  With a difficult eye, I'm usually better )

With retinoscopy, an Rx can be assessed for people who can't or won't communicate (grumpy teeenagers making a significant showing, here.) but in ordinary cases it provides a good starting point and cross-check for the first technique.

I'd never rely on an autorefraction or retinoscopy alone, unless I had to.

Answer 3

its quit easy they usually do the trial nd error method i.e they randomly chose a lens from there kit and will place it in front of ur eyes is special spectacle and asks u about the site based on that they try different lens until u get a perfect vision

These days some sophisticated machines are available which precisely calculate the power of lens needed by you

Answer 4

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