Formation Opticien Examen de vue CCR Cylindres croisés- Jackson Cylinder (ENGLISH)


On this video we will develop the research of astigmatism with the method of Jackson Cross Cylinder, when you have followed the method of the fog for a visual acuity superior or equal to 10/10. There is a course with several cases, so do not hesitate to play the video again. Case 1: ASTIGMATISM RESEARCH You introduce this tool, it’s called the Jackson Cross Cylinder (CCR). You have 2 positions either this one, or this one with P in the axis. There, it is parallel and perfectly in the axis at 0 °. Can you see it ?
– Yes… P as power, so if you do P it’s because you’re in search of power. Astigmatism is primarily the search for the axis. Do you see the red axis? Well, for CCR you have to focus only on red dots! Indeed, when we carry out the research of the axis with the CCR, we turn the axis of the red dots between 45 ° 135 °as here which represents the axis of the negative cylinder, it will be enough for us to retain the position of the red dots better perception. I show you a cloud of points, you will tell me in which position the symbols look sharper to you, blacker or more contrasted: rather in position 1? rather in position 2? where is it the same? – Number 2.
– This one?
– Number 2 yes. There you have to go at 45 ° because the red dots were at 45 °. Look, we start again. Position 1? Position 2? or is it the same?
– Number 2 You see the red dots they are at 45 °. How do you know that the red dots are at 45 °? Because between the handle of the CCR and the red dots there will always be 45 °.
– OK. So you go to 45 ° and you start again. Position 1? Position 2? or is it the same?
– Number 1. Here she tells you prefers red dots when they are 0 °. So there we must position ourselves in the bisector at about 15 °, that is to say in the bisector between 0 ° and 45 °. Look, we start again. Position 1, Position 2, or is it the same: she tells me this position so 45 °. Then Position 1, Position 2, or is it the same: she tells me it’s position so 0 °.
– Yes. So here we position the axis in the bisector at about 15 °. Then we add (-0.50) diopter to the cylinder and +0.25 diopter to the sphere. Then we will refine the axis in steps of 5 ° in 5 °. Position 1, Position 2, or is it the same?
– Number 2. You can see the handle here it is set at 15 °. She prefers when the red dots are downward, and we always go towards the red dots so at 10 °. Position 1, Position 2, or is it the same?
-Number 1. So there the red dots are upward, so we went downward too much and we have to go up to 15 °. Position 1, Position 2, or is it the same?
– Number 2. ` We have to go up again to 20 °. Position 1, Position 2, or is it the same?
– Number 2. So here she maks us downward to 15 °, and in this case it is preferred to keep the axis the closest to 180 °. Then we put P in the axis “P like power”, we’ve finished looking for the axis we now we pass on to the power. Position 1, Position 2, or is it the same?
– Number 1. Here she asks us to increase the power of the cylinder. Position 1, Position 2, or is it the same?
– Number 2. Here she asks us to increase a second time, so we add a spherical equivalent of 0.25. Position 1, Position 2, or is it the same?
– It’s the same. So that’s it, we can remove the CCR and then check the sphere to be sure to be on the convex max correction and move to biocular balance. Case 2: ASTIGMATISM RESEARCH So look at the Jackson Cross Cylinder (CCR), it is the tool that you can rotate here. You set it well at 0 ° and look here you have the handle that is perfectly parallel to the axis. – OK You only look at the red dots. You have them either in this position or in this position. Knowing that there is always 45 ° between handle and the red dots. – OK. You are going to tell me in which position the symbols look sharper to you, blacker or more contrasted: rather in position 1? rather in position 2? or is it the same? – This one. Position 1, Position 2, or is it the same?
– The first. Position 1, Position 2, or is it the same?
– The same. One more: Position 1, Position 2, or is it the same?
– The same. Position 1, Position 2, or is it the same?
– The same. Position 1, Position 2, or is it the same?
– The second. Position 1, Position 2, or is it the same?
– The second one again. Case 3: ASTIGMATISM RESEARCH I show you a cloud of points, you are going to tell me in which position the symbols seem to you sharper, more black or more contrasted: rather in position 1? rather in position 2? or is it the same? – Number 1. So there, you always have 45 ° between the two. There the red dots are at 135 °. Is it good? So you go to 135 °. Position 1, Position 2, or is it the same?
– Number 1 So there she tells you 180 °. So the framing of the axis is between 135 ° and 180 °. After you put yourself in the bisector, you add (-0.50) to the cylinder and +0.25 to the sphere. And we start again: Position 1, Position 2, where is it the same? – Number 1 So you turn your handle by 5 degrees. How do we know it’s 5 °? Well because by steps of 5 ° to 5 °. And how do we know in which direction we are going? Because we always go in the direction of the red dots. You see the red dots they are to here, or there. We move all the time of 5 ° to 5 ° compared to 135 ° that we had befine? No compared to 150 ° the bisector. So here we set at 145 °. Position 1, Position 2, or is it the same?
– Number 1 She tells us to lower because the red dots are downwards. Position 1, Position 2, or is it the same?
It’s the same ? – The same Position 1, Position 2, or is it the same?
– Number 1 When she says red it is necessary to increase the cylinder. Position 1, Position 2, or is it the same?
– Number 2 When she says red we have to increase, and we have just increased twice, so you add +0.25 to the sphere. – But why when it is red? When the red dots are in the axis of the handle, you have either the reds or the whites. When she says she prefers the red dots the cylinder is increased and when she says to prefers the white dots the power of the cylinder is lowered. – ok! Position 1, Position 2, or is it the same?
-Number 2 So you lower Position 1, Position 2, or is it the same? -The same. THAT’S IT!

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