Idea: functional measure of reading distance.

Not sure. I was thinking that this could serve as an indicator of the degree of EDOF a lens has. So a wider defocus curve would result in a lower distance.

It would be interesting to see that distance vs focus distance graphed for various people.

What confounds that is the degree that brightness would pay.

For me, if I got the near eye set to -1.5 vs -1.75, how far out would I need to read a small font label.

When I was doing testing I concluded that the simplest way was to use the Jaeger test at 14" in sunlight.

Sunlight for the Jaeger test seems too strong for a more-useful test. Normal room lighting would be informative to me. Or in-between would be average store lighting.

Full noon sunlight would be more repeatable, because normal room lighting, without a light meter, would vary a lot.

I often make a pinhole with my fingers to read stuff in stores.

I use a reading lamp over my shoulder in a room with window blinds closed. There's also phone apps, but I couldn't be bothered to figure out the impact of variations in screen size and how to make sure the brightness setting is the same every time.

I like sunlight because it is a known fixed light level without having to measure it. F16 @ 1/60 second is the nominal camera setting for a good sunlight exposure in the old days of film!

https://en.wikipedia.org/wiki/Sunny_16_rule

"On a sunny day set aperture to f/16 and shutter speed to the [reciprocal of the] ISO film speed [or ISO setting] for a subject in direct sunlight."

Maybe you were using Kodacolor-X or Kodachrome-X, which were ASA 64.

I guess that would make another interesting graph-- typical acuity vs lux.

I have thought that the chart an optometrist places at a short distance was too-greatly illuminated when they turned on the associated lamp.

Yes, I was thinking back to the old Kodak fixed camera days, and probably ASA 64.

What you may want to test for is binocular 3D vision at 2-3 feet. There may be a loss with the -2.0 D as the near eye, compared to -1.50 D. But if it is at a distance that is not important to you, then it may be a good option. Is there a loss in adjustment ability if you jump all the way from plano to -2.0 D in one light adjustment. Will you be able to fine tune from there? Or would it be better to jump to -1.75 D and then count on one or possibly 2 more steps to go up and down from there?

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The other aspect that will be hard to simulate at this point will be the eventual total loss of accommodation in the distance eye once you go to an IOL, which would seem inevitable. However, if you are at plano now with the LAL eye, this would be the time to estimate what it will be like.

Yes, intermediate vision is definitely the main tradeoff for more near vision. My computer screen is at ~30"-32", and I am comforted by the fact that I can read it pretty well already with the LAL eye near plano. Hard to test binocular vision with one eye remaining natural, but monocular intermediate vision is clearly worse at -2.0 than at -1.5. Hopefully intermediate will still be ok either way when I eventually get a new distance lens, and perhaps this is where the apocryphal EDOF cabability of the LAL will help.

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I was not able to discuss the adjustment strategy in any depth with the surgeon - he said it's too early to figure it out now, and much will depend on the measurements three weeks out. My biggest question right now is the amount of astigmatism they'll need to correct, and whether there'll be enough room within the available 4.00 D to cover both astigmatism and desired myopia. You raise some good questions, and I suspect it may be better to target -1.5 or so at first to avoid overshooting the mark. My doctor and others have mentioned the idea of 'creeping' toward the final goal with the near-vision eye.

What astigmatism did your far eye have pre-surgery?

Regarding "whether there'll be enough room within the available 4.00 D to cover both astigmatism and desired myopia." remember that the lens at implant already has a target that could be aimed at where you want to end up. So the needed adjustment could go either way to hit your target.

Now if that LAL Plus changes the plan, we will see.

Yes, I am much less concerned about the far eye, for the reason you suggest. I expect to need very little adjustment from the plano target, and hopefully will have plenty of adjustment available for any astigmatism. Also, I don't plan to get the far eye surgery any time soon. I will not be using LAL+. My surgeon advises against it because of my previous LASIK, and also I think it makes sense to avoid EDOF and go for the best achievable distance vision with that eye.

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It's the near eye I just got operated that I am concerned about. Pre-op astigmatism on that eye was small, just -0.25 D. But that was including lens and cornea. With the lens gone, residual astigmatism could be substantially greater. I had a 'corneal wavefront' scan that reported 1.30 D of "total" corneal astigmatism, but it was unclear just what that meant - there are correctable astigmatisms, with the rule, against the rule, and other astigmatisms like 'oblique' and 'second' order astigmatisms that may not be correctable, at least not with LAL.

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So the math I'm doing now is:

+0.25 D post-op hyperopia (guesstimate)

+1.30 D of astigmatism to be corrected, maybe

+2.00 D of myopia to get my preferred reading vision

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That's already 3.55 D of the available 4.00 D adjustments. And I've heard sometimes the adjustments produce fewer diopters than expected and you may not get the full 4.00 D. So, I'm a little concerned. But I am encouraged by my pretty good vision right now - close to 20/20 when tested the day after surgery. I figure even if they don't correct any astigmatism and just get me a couple diopters of myopia, the outcome should be pretty good. So, I'm not too worried, but I do want to try for the sharpest near vision I can get.

" I had a 'corneal wavefront' scan that reported 1.30 D of "total" corneal astigmatism, but it was unclear just what that meant - there are correctable astigmatisms, with the rule, against the rule, and other astigmatisms like 'oblique' and 'second' order astigmatisms that may not be correctable, at least not with LAL."

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Normally corneal astigmatism regardless as to whether it is with the rule, against the rule, or oblique can be well corrected with a toric or I assume with the LAL. It is just a matter of orienting the correction with the specific axis of the astigmatism. Now if the astigmatism is irregular that starts to become a bit of an issue. If you have been given the opportunity to see the topographical scan of the cornea it should give you a good idea how regular you astigmatism is. You should see a symmetrical hourglass or bow tie shape or similar at an oblique angle. But if the steep area is offset then the surgeon will have to make an estimate as to the best way to correct it, or perhaps that may be built into the computer system that maps out what the correction should be. You may have some higher order astigmatism due to the prior refractive surgery that cannot be corrected.

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On the total range of adjustment possible you will want to hope that they can go as far as you want. But with your commitment to monovision, I think I would have started at -1.0 D to -1.25 D, and adjusted from there. But that ship has sailed now!

"Normally corneal astigmatism regardless as to whether it is with the rule, aainst the rule, or oblique can be well corrected with a toric or I assume with the LAL."

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My scan showed significant amounts of both WTR/ATR and oblique astigmatism. I would not expect that both types can be corrected well with a standard toric lens. I could be mistaken about that, but it seems like it would be difficult to correct both with a single, standard toric lens. Perhaps it could be done with LAL, though. I guess I will find out!

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Yes, I agree that a more myopic initial lens target may have been better. My hindsight has been measured at 20/12...

WTR only means that it is a more common orientation of the axis angle. It is when the angle is close to 0 deg or 180 degrees or essentially horizontal. Astigmatism in children or younger adults is generally with the rule. ATR is more common in older adults and develops later in life. The axis of the cylinder is closer to 90 degrees. Both types are equally well corrected with the same standard toric lens. The only difference is the angle that the surgeon implants them at. Oblique is just an angle in between like 45 degrees. Again equally well corrected with a standard toric.

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To see the difference between regular and irregular astigmatism google this. Irregular astigmatism is often associated with keratoconus. The images in this article are probably from a Pentacam. I have one eye that has irregular astigmatism and the Pentacam image looks much like the one on the right. This is much harder to correct and a standard toric may or may not help. I recall from a previous discussion that the LAL is not capable of programmed custom lens configuration to handle irregular astigmatism.

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vision and eye health keratoconus What is it

Those search terms do not seem to work. Here is a clip of the image I am talking about.

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Once the astigmatism is corrected, I believe your surgeon is correct - take smaller steps. Some EDOF will be created on the first adjustment. My surgeon told me as well as the optometrist, people are amazed at how well they see with -1.25 diopters in the near eye. If you had chosen a more myopic LAL Target such as -1.0 diopters, you would not benefit from as much EDOF. That is my understanding. I wish somebody else would chime in. Also, the ophthalmologist that performs the LDD treatments just had LAL's implanted in both of her eyes. She chose -1.5 diopters for her near eye.

This is my dilemia: I would like to be intermediate/near in both eyes and wear glasses for distance. Should I Target the LALs -0.25 diopters to take advantage of EDOF? Or should I Target the LALs -0.75 to be certain I don't run out of macromers. Should I consider the LAL + and Target -0.75? I have given up on having it all: far - intermediate - near, like Deanna81707.

I have made an appointment Thursday afternoon with yet another ophthalmologist. This will be my fourth ophthalmologist! I will be sure to ask him how much EDOF both the LAL and the LAL Plus have.

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I believe @JDvision and @trilemma both had astigmatism corrected.

@JDvision has much experience on light treatments and using diopters. trilemma has much experience on lens trials after getting her LAL in her distant eye.

RonAKA it's just Amazing about everything!

Those search terms do not seem to work. Here is a clip of the image I am talking about.

After looking at your images, I had suspected that the colors mapped the prescription/focus at each point. Instead I see it is mapping thickness, but that will relate to prescription.

I expect there will come a time where they map many points and adjust the RxLAL accordingly-- as they now do with LASIK.

"Oblique is just an angle in between like 45 degrees. Again equally well corrected with a standard toric."

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Yes, I get that. My question is, what if you have both WTR astigmatism AND oblique astigmatism in the same eye? That's what my wavefront scan shows. I'm thinking that a toric lens can correct either one of those two just fine, but it cannot correct both. Is that right?

Currently it is only done with wavefront guided, sometimes called custom Lasik. That may be a future enhancement of LAL.

I am not sure what you are looking at to see the oblique astigmatism. Very few people have pure ATR (90 deg) astigmatism, or WTR (0 or 180 deg). The actual axis is somewhere in between and I guess that could be called oblique. Not hard to correct at all, as a toric lens can be implanted at any angle you choose. The problem comes in when the astigmatism is irregular and not centered on the middle of the eye. Then how do you adjust the axis of the standard toric lens to get the best correction? With a phoropter you do that by trial and error, based on what you see. Which is better? One or two? I believe with an IOLMaster and the Pentacam they do it by measuring the steepest part of the cornea and the least steep. They are always different by 90 degrees. The outcome of the measurement process forces the angle difference. So, in the case of the irregular astigmatism there must be some compromise in how that is calculated by the instrument as the actual topography is not 90 degrees apart. I know when you enter data in an IOL power calculator you only enter one angle for the K1 and K2. The other angle is just calculated to be 90 degree different.

I am looking at a wavefront scan report done on my eyes a few weeks ago, using a Carl Zeiss ATLAS machine according to the printout. It shows on the same eye (OS) BOTH -1.010 of primary WTR/ATR astigmatism and -0.551 of primary oblique astigmatism. There are also measurements of secondary astigmatisms, both WTR/ATR and oblique.

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You seem to be suggesting that I can't have two (or four) different astigmatisms on the same eye, and I certainly could be misunderstanding the report. But the above is what the report says. Perhaps the multiple astigmatisms are just a different way to mathematically describe a single, irregular astigmatism?

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The report is mostly numbers, no imaging that could look like a bow tie or not like a bow tie, though there is a circular keratometry graph showing numbered slices of the cornea in three concentric sections: central, midperiphery, and periphery. There are also Zernike polynomials provided, one for each listed corneal aberration, so perhaps there is some math to be enjoyed here.

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Thanks for your comments. Again, the reason I am interested in this is minor anxiety about my new LAL, and wanting to understand how much adjustment will be used up for astigmatism and how much will be available for myopia. I suppose all will be revealed in good time...

Those numbers do not mean much to me. On a quick look at some Zeiss Atlas reports I found on the internet, I do see numbers and angles for steep and flat K factors. That is normally what is used to calculate astigmatism. I think in most cases the surgeon uses the IOLMaster to get all the measurements to calculate IOL power which includes the K factors and angles, but I do not believe it includes the topographic map. That would be additional data the surgeon may look at to verify the results given by the IOLMaster. I suspect they are mainly looking at the topography to determine if there are unusual issues with the eye. That may be the case for post refractive surgery patients. But, at the end of the day they still can only enter the data for the K factors. There are some formulas that can accept the TK numbers which include both the front and back of the cornea, and apparently can be helpful in getting a more accurate calculation providing the formula accepts the data like the Barrett does. Some formulas also accept prior to laser surgery measurements if they are still available.

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I think with LAL they will make corrections based on their experience and then you will tell them based on the phoropter corrections what you would like to see changed - like angle and magnitude of cylinder. This would be an upside of LAL where you based on what you see provide feedback on what works and what does not.

One thing you might want to consider if you have all the data is to use the Kane Formula to calculate what lens power, cylinder power, and the angle predicted by the Toric Version of the Kane formula. That would give you some idea what cylinder is there to be corrected.

"I suspect they are mainly looking at the topography to determine if there are unusual issues with the eye. That may be the case for post refractive surgery patients."

Yes, I believe the doc was looking for secondary aberrations, and found some significant ones in my corneas, no doubt due in part to my old LASIK.

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I do see two sets of three numbers for each eye (6 numbers per eye) labeled "Sim Ks (3mm)". One in D (dunno what D stands for here, but the values are in the range of 37-40), one in mm, and one that looks very much like an angle in degrees (the two angles differ by 90 degrees for each eye). I'm guessing those include the K factors you're referring to.

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I probably won't figure out what all this says, but I am looking forward to seeing what the LAL can do with it. I may wear out their phoropter in the process!

Will take a look at that Kane formula. Thanks!

I see a comment by a surgeon named Hunter Newsom discussing multiple simultaneous astigmatisms in Ophthalmology Management' a few months ago:

'Yes, the issue with 0.50D to 0.75D of astigmatism is what axis to correct. I recently had a patient with 0.50D to 0.75D of cylinder at six different axes. For a patient like that, the LAL should be the standard of care.'

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There was no further explanation, but this gives me the impression that LAL can indeed be adjusted to separately correct multiple astigmatisms on the same eye. And that a standard toric lens can not.

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Also, that cornea sounds like a real mess! I hope mine is not that bad...

I would think the comments must be specific to post refractive surgery eyes. Even eyes with keratoconus are not that complicated. The story will be told in the cornea topography display. If you look at the images at the link below there are some that are pretty messed up alright. If you look at Pentacam images of eyes with astigmatism and even irregular astigmatism they are not that irregular.

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CRST REFRACTIVE SURGERY | OCT 2019 Navigating a History of Refractive Surgery