@chechnya The auto-refractor is SUPPOSED to do this. The last time I had an auto-refractor measurement it was fro -9 diopters. (My visual acuity was in fact 20/40). You can not "digitize" or "automate" this process -- in my opinion. You need the "feedback" from the person as this video demonstrates.
Doing the left eye, shouldn't you have made adjustments to the sphere as you dialed in more cyl. power, to maintain the spherical equivalent? Also, for the same eye, when checking axis, isn't it important to reach neutrality, get reversal, then go back to neutrality?
@Commando303X Yes, I should have; then I wouldn't have needed to adjust so much at the end. As for the axis, it depends on how much time you'd like to spend refracting. It's very different scenarios if your refracting a patient seeing an ophthalmologist for medical reasons who needs only the manifest and no prescription will be written, verses a 2.5+ cylinder patient being seen complaining about his glasses.
Good to see the tutorial. The mistake in the left eye was made because you forgot the critical 2for1 rule of refracting. The sphere is changed by 0.25 in the opposite direction of the cylinder when changing the cylinder by 0.50. In this case you changed the LE cyl from +1.25 to +1.75 but failed to compensate in the sphere to keep the circle of least confusion on the retina. If you had added -0.25 to the sphere prior to the next power determination then the cyl would have come down.
@greenroneye1 Very true, I had forgotten to do this. I've been trying that recently after reading your comments and found my accuracy improved on the first go around, thanks!
I like the instructional value of this video. I do think that a motivated person should first read his Snellen with no phoropter. If you wish to teach the general concept to a person, simple hand-held spherical lenses (and a Snellen at 20 feet) would get the concept to the person in a manner that he could understand this process. Thanks!
@otissumnerbrown True, that would be informative. As this was originally a video made for a coworker with a solid vision background, I went straight to the refraction bit, assuming she knew the basics.
@Commando303X Yea, the editor I used rounds to the second, making the slides choppy. You can watch the unedited video; I just uploaded it on my channel.
@SilmaYevrah Do you place the knobs according to the axis when searching for the cylinder power or make sure that the white and red dots are btw the white arrow. Need clarification? And is the tech following the white dot only for cylinder axis? And instead of adding an additional 75 diopters at the end, why didn't you use the duochrome to ensure that the sphere was correct? Thanks.
@dstewart1117 To refine cylinder power, you align the white and red dots of the Jackson-Cross cylinder with the axis arrows, so yes. Refracting in plus cylinder, you add cylinder power if the patient chooses the white dots on the axis, or reduce power if the white dots are perpendicular, (opposite in minus power.) You only "follow" the dots when refining axis, turning the axis knob towards the white dot in plus cyl., or red dot in minus.
@dstewart1117 I find duochrome useful for finding sphere power in the first steps of refraction, not for balancing at the end, i.e. s/p cornea transplant patients where you can't get an auto-refract. However, if you have a nice and bright projector with duochrome and like using it to confirm your manifest, go ahead. Refraction isn't an exact science, there's some art to it aided by many tools. Find the ones you like and use them.
This was very helpful. I am studying for my COA and am learning to refract at work.
The balancing of the lens confused me a little and also why did you ask her if she was right handed or left handed. Thanks for all the information. I learned alot.
I didn't explain how to balance for lack of time. It's not always necessary, but helpful with some patients, especially high myopes, as giving them the manifest refraction in their glasses can be uncomfortable.
To balance:
1. add +0.75 to both eyes
2. ask which of the blurry eyes is better. The better eye may be overcorrected with too much minus. Add +0.25 to the better eye.
3. repeat step 2 until the patient says both eyes are the same or they alternate
3.5. if the patient alternates between their eyes, find out which is their dominate eye and let that one be the "better" eye. This is why I asked what hand she was; usually a right handed person in right eyed.
4. add - 0.50 back to both eyes and ask what they can see. Then ask if they like one more - 0.25 OU.
5. you now have your balanced prescription
Remember, balancing is only helpful on patients you fear you can overcorrect. Presbyopes and pseudophakics rarely need it.
Another note, balancing will more than likely NOT be on your COT practical exam. It's computer-based, and I don't think it's capably of sucking up minus like a human :). Good luck on your COA!
really cool
IBMaccMartelli 2 months ago
How is this not digital yet?
chechnya 4 months ago
@chechnya The auto-refractor is SUPPOSED to do this. The last time I had an auto-refractor measurement it was fro -9 diopters. (My visual acuity was in fact 20/40). You can not "digitize" or "automate" this process -- in my opinion. You need the "feedback" from the person as this video demonstrates.
otissumnerbrown 2 months ago
some video like this one, in spanish? please =C
CitrusLuifer 7 months ago
Doing the left eye, shouldn't you have made adjustments to the sphere as you dialed in more cyl. power, to maintain the spherical equivalent? Also, for the same eye, when checking axis, isn't it important to reach neutrality, get reversal, then go back to neutrality?
Thanks.
Commando303X 1 year ago
@Commando303X Yes, I should have; then I wouldn't have needed to adjust so much at the end. As for the axis, it depends on how much time you'd like to spend refracting. It's very different scenarios if your refracting a patient seeing an ophthalmologist for medical reasons who needs only the manifest and no prescription will be written, verses a 2.5+ cylinder patient being seen complaining about his glasses.
SilmaYevrah 1 year ago
Good to see the tutorial. The mistake in the left eye was made because you forgot the critical 2for1 rule of refracting. The sphere is changed by 0.25 in the opposite direction of the cylinder when changing the cylinder by 0.50. In this case you changed the LE cyl from +1.25 to +1.75 but failed to compensate in the sphere to keep the circle of least confusion on the retina. If you had added -0.25 to the sphere prior to the next power determination then the cyl would have come down.
greenroneye1 1 year ago
@greenroneye1 Very true, I had forgotten to do this. I've been trying that recently after reading your comments and found my accuracy improved on the first go around, thanks!
SilmaYevrah 1 year ago
I like the instructional value of this video. I do think that a motivated person should first read his Snellen with no phoropter. If you wish to teach the general concept to a person, simple hand-held spherical lenses (and a Snellen at 20 feet) would get the concept to the person in a manner that he could understand this process. Thanks!
otissumnerbrown 1 year ago
@otissumnerbrown True, that would be informative. As this was originally a video made for a coworker with a solid vision background, I went straight to the refraction bit, assuming she knew the basics.
SilmaYevrah 1 year ago
It's awkward to have the video freeze and present text in the middle of the speaker's comments...
Commando303X 1 year ago
@Commando303X Yea, the editor I used rounds to the second, making the slides choppy. You can watch the unedited video; I just uploaded it on my channel.
SilmaYevrah 1 year ago
@SilmaYevrah Do you place the knobs according to the axis when searching for the cylinder power or make sure that the white and red dots are btw the white arrow. Need clarification? And is the tech following the white dot only for cylinder axis? And instead of adding an additional 75 diopters at the end, why didn't you use the duochrome to ensure that the sphere was correct? Thanks.
dstewart1117 1 year ago
@dstewart1117 To refine cylinder power, you align the white and red dots of the Jackson-Cross cylinder with the axis arrows, so yes. Refracting in plus cylinder, you add cylinder power if the patient chooses the white dots on the axis, or reduce power if the white dots are perpendicular, (opposite in minus power.) You only "follow" the dots when refining axis, turning the axis knob towards the white dot in plus cyl., or red dot in minus.
SilmaYevrah 1 year ago
@dstewart1117 I find duochrome useful for finding sphere power in the first steps of refraction, not for balancing at the end, i.e. s/p cornea transplant patients where you can't get an auto-refract. However, if you have a nice and bright projector with duochrome and like using it to confirm your manifest, go ahead. Refraction isn't an exact science, there's some art to it aided by many tools. Find the ones you like and use them.
SilmaYevrah 1 year ago
This was very helpful. I am studying for my COA and am learning to refract at work.
The balancing of the lens confused me a little and also why did you ask her if she was right handed or left handed. Thanks for all the information. I learned alot.
loveNpeaceToU 1 year ago
@loveNpeaceToU Glad it was helpful!
I didn't explain how to balance for lack of time. It's not always necessary, but helpful with some patients, especially high myopes, as giving them the manifest refraction in their glasses can be uncomfortable.
To balance:
1. add +0.75 to both eyes
2. ask which of the blurry eyes is better. The better eye may be overcorrected with too much minus. Add +0.25 to the better eye.
3. repeat step 2 until the patient says both eyes are the same or they alternate
SilmaYevrah 1 year ago
@loveNpeaceToU
3.5. if the patient alternates between their eyes, find out which is their dominate eye and let that one be the "better" eye. This is why I asked what hand she was; usually a right handed person in right eyed.
4. add - 0.50 back to both eyes and ask what they can see. Then ask if they like one more - 0.25 OU.
5. you now have your balanced prescription
Remember, balancing is only helpful on patients you fear you can overcorrect. Presbyopes and pseudophakics rarely need it.
SilmaYevrah 1 year ago
@loveNpeaceToU
Another note, balancing will more than likely NOT be on your COT practical exam. It's computer-based, and I don't think it's capably of sucking up minus like a human :). Good luck on your COA!
SilmaYevrah 1 year ago