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Old Aug 4th 2015, 05:50 AM   #1
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Can any one explain Retinoscopy concept in lay mans terms but detailed please

Retinoscopy concept in lay mans terms but detailed please
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Old Aug 5th 2015, 04:00 PM   #2
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Because of the shape of the eye and the focusing action of the lens
if a a parallel beam of light shone into the eye, any light reflected back from the retina should come back along exactly the same (but reversed) path.
That would be the case for for a perfect eye.
by beaming the light into the eye at different angles the entire retina can be scanned.
Observing how closely the reflected beam matches the original indicates how well the retina and lens are working.
You have GOT to Laugh !
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Old Aug 6th 2015, 06:17 AM   #3
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Thank you somuch for reply, it would be nice if you can explain the procedure of retinoscopy and along with it the optics involved. Step by step with explanation and optics involved in lay man terms? Thanks in advance
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Old Dec 21st 2015, 08:49 AM   #4
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I'l have a go !
there is more to a lens than "meets the eye" ... if you get my meaning ?
The simple biconvex lens that you find by dissecting an eye is only half of the story. The curved window at the front, which allows Light to enter he eye (the ???), combines to form a compound lens. I you swim under water you doubtless are aware that vision is NOT clear? This is because replacing the normal outside environment (air) with water has changed the refractive index of the lens and so the eye becme defocussed.

Unfortunately lenses are not the answer to the maidens prayer as is so often taken for granted. Light reaches the retina by multiple paths:
(a) straight down the middle (normal incidence)
(b) by travelling off-centre to strike the lens combination near its outer periphery and so be refracted on to the Retina.
As with everything in life you may not it have it both ways and this second wave, travelling a longer path, arrives at the Retina in a slightly different spot. This blurrs the image as sent to the Brain.

Now increase the intensity of the illumination. The Retina objects and so the Iris closes down to restore a comfortable level. In doing so it blanks off the outer regions of the lens and the "abberration", is reduced. The "depth of field" also is increased.

All this has assumed that the eyeball is perfectly spherical which is seldom true. As a result those final spots on the Retina do not fall where they are intended but are brought to focus either before theRetina or behind it. This results either in short-sightednes or in long-sightedness.

I believe that Retinoscopy is more about testing the degree of sphericality and checking the medical condition. Moving the source of the Light causes the beam to be deflectd to different areas.

Ken Green
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