Optics Course : Astigmatic fan/Dial : principle behind and how to use.

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Astigmatic fan /Dial is of help for the subjective diagnosis of astigmatism as well as for the description of the correct glasses. This video explains the idea behind it use and how to practically make us of this simple technique at hand.
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[@tarekhussein2186]

Great and simplified Dr Adel .. thanks a lot

[@adelabdelshafik]

Great that you found it useful

[@husseinalshadeedi3024]

Thank you sir for the clear explination

[@adelabdelshafik]

Welcome

[@hamedabuhuryra8349]

Sir In the example at 4:49 the vertical meridian is myopic by -1,so sholdn't the horizontally focused rays come on front of the retina as we know that astigmatic lens give focal line parallel to the axis for a point source of light?

[@adelabdelshafik]

would you re see the video up to 6.30 minute , this part explains that each point of the object will be extended in a vertical direction so on looking at a cross, the vertical line of the cross will extend vertically so only its extreme ends will be blurred , on the other hand the horizontal line all its points will extend vertically so the whole line will be blurred. Here we are not dealing with a cylindrical lens. in case of a cylinder we follow rays and see which meridian will come to a focus on the retina. Hope I made myself clear. my regards

[@hamedabuhuryra8349]

@@adelabdelshafik thanks alot dear prof 🌹

[@adelabdelshafik]

@@hamedabuhuryra8349 welcome

[@047heenasingla6]

Thank u so much sir Bcoz of this vedio i could understand why vertical line would be seen more sharp if there is problem in vertical meridian. 🙏🙏

[@adelabdelshafik]

Welcome. Glade to hear your opinion.

[@bladesociety]

Thank you for this excellent explanation, Dr. Abdelshafik. One clarification though. If we follow your explanation with the cross on mark 5:52, shouldn't the blackest line on the astigmatic fan on mark 11:00 be the vertical one as the dots will be perceived as vertical oblongs (I'm referring to the diagram with the horizontal line on the retina)? Thank you so much, Dr, I have understood everything up until this particular point.

[@adelabdelshafik]

" shouldn't the blackest line on the astigmatic fan on mark 11:00 be the vertical one" : would you re phrase, I could not catch your point of view.

[@sachinmdesai]

Thanks for the lecture sir

[@adelabdelshafik]

Welcome, glade you find it useful.

[@sachinmdesai]

@@adelabdelshafik Having a good teacher is a valued privilege sir. I and many others like me value your painstaking efforts. Please keep spreading the knowledge to us all. Thanks again!

[@falahibrahim8447]

Very helpful

[@TrainLiu]

Thank you very much! OTL

[@adelabdelshafik]

welcome

[@sumitdhingra1619]

hii sir.....please make a video on GHT in detail

[@adelabdelshafik]

kzbin.info/www/bejne/gHyWZJ2Vpbqjb6s

[@AbhishekSingh-lu8tw]

Sir, one question 07:21 Why we put cylinder perpendicular to sharp dark line if it indicates astigmatic meridian (axis)? Cylinder axis should be placed correctly waiting for reply

[@adelabdelshafik]

When you apply a cylinder with its axis at 180 degrees, the effect of this cylinder will appear at 90 degrees

[@karemoptom]

Thanks a lots sir

[@AbhishekSingh-lu8tw]

Sir you didn't explain MADDOX V test! 😭😭😭

[@vahidovahido]

Perfect

[@adelabdelshafik]

Thanks, glade you find it useful.

[@learnerstockmkt6143]

hello sir........................ sound is very low

[@adelabdelshafik]

Would watch the video on other device, The sound level is average, would you check again and let me know.

[@learnerstockmkt6143]

@@adelabdelshafik ok sir

[@AbhishekSingh-lu8tw]

Sir please try to speak louder, not here but in all videos. Except this your videos are perfect. hope you don't mind

[@adelabdelshafik]

OK. Will do

[@AbhishekSingh-lu8tw]

@@adelabdelshafik Make a video on JCC