Laser touch-up

Eye care
1

After my cataract operation my right eye came out +0.75 or +0.5 sph, -0.50 cyl, axis 15, Base 6/6+

Would it be advisable to request a laser touch-up to adjust it to be 0 sph ?

I think the margin might mean it could go down further, say to 0.5 sph, but would that be a problem ?   The other eye hasn't yet been done, but is scheduled for July. I plan to request normal distance (I suppose 0 sp).    My original prescription was very myopic - sph -15 

(I am not keen on having a distance lens in one eye and a reading one ibn the other in case I don't get used to that, and it wouldn't cover middle distance anyway.

I think the two eyes will not be quite the same strength anyway, and so should together give me a slightly greater range of focus, which will be useful.

The surgeon mentioned multifocal lenses but said he didn't recommend them.  A friend has trifocal lenses and is pleased with them.

2

Unfortunately as you are likely aware, there is more of a risk of the lens power being off for high myopes so your 2nd eye's results might be off also. I'd seen at least one study suggesting taking the results of your first eye into account may not make much difference for the accuracy of the 2nd eye. So you really might consider seeing where the 2nd eye winds up before figuring out what laser correction to get.

Although it sounds like you don't want full-on monovision with an eye targeted for near, you seem to apprecaite the possibility that one might wind up a bit myopic, e.g. micro or mini-monovision, to give you a bit more range of vision. So I'd suggest waiting until you get the 2nd eye done, then doing a contact lens trial to see where you want your eyes set permanently with a laser adjustment. I don't know if you are used to contacts (many high myopes prefer them, though you wouldn't have been able to use most standard off the shelf brands which are lower power with myopia that high), but if you tried them and didn't like them in the past, the experience for a short trial might be different since the contact lenses can be thinner for a small correction, and modern contacts are more comfortable than the older ones were  if you hadn't tried them recently. For small corrections, most places would have sample disposable lenses in stock to try. 

You could try a contact lens trial that includes also trying to see what the result might be for some sort of reasonable margin of error, e.g. to see if you targeted this eye for a slight bit of myopia and wound up a little more myopic, whether the result would be ok. 

Since you have one eye done, you could also consider trying a multifocal contact lens in that eye to see if you like multifocal correction to consider whether to get a premium lens for your 2nd eye. (I'm guessing the 2nd eye has a cataract which would interfere with getting good results with a multifocal contact in that eye). The optics of a multifocal contact aren't the same as premium IOLs, you might like a premium IOL even if you don't like a multifocal contact, but if you do like the multifocal contact it would suggest you might like a premium IOL.

​

In my case I liked multifocal contacts, and like the Symfony IOLs I got even better. They are extended depth of focus rather than multifocal. Although some surgeons confuse the two types of lenses since they are experts in medicine rather than optics, the different optics leads to a lower risk of night vision artifacts with the Symfony than a trifocal, and better intermediate with the Symfony, at the expense of not as good really close vision (which many consdier a good tradeoff since really close near isn't used as often, but each person's preferences vary). 

Your eye is farsighted which does reduce its near and intermediate vision, however the cylinder means it isn't quite as bad. Astigmatism means the lens power of the eye is different at different angles. If you are +0.5 sph -0.5 cyl then in one direction the eye is +0.5 but in another it is 0D, averaging out at +0.25D. If you are +0.75 sph -0.5 cyl, then its +0.5D. Unfortunately the very limited range of depth with a monofocal means either of those will still have a noticeable impact on the workable range of vision without correction.

In terms of "the margin", unfortunately I haven't been able to get any good sense of the margin of error for small corrections.(which I'd be curious about since I have one eye that was left +0.5D, but my other eye makes up for it, and I have the Symfony IOL so its reductoin in near isn't as bad as with a monofocal  and so correcting it hadn't been a priority, I'm 2 years postop now and hadn't bothered yet).

Most laser surgery is done to correct several diopters and presumably some aspects of the error involved migh be a % of the attempted correction, in which case they'd be much less for a small correction of less than a diopter and so anecdotal reports claim they are much more accurate. You can see if your surgeon has any comments on the margin of error with their particular technique and equipment, but there is a good chance they don't have it for small tweaks (and studies tend to be for multiple models of laser, etc, and the real margins likely vary between lase models, with techniques and even software updates to the laser).

 

You can be a bit myopic and not see too much reduction in distance vision, so personally I'd likely target -0.5D or -0.25D rather than 0D for my +0.5D eye. My other eye has at least 20/15 distance vision (they didn't have a line below that, and that line was easy) and its at -0.25 sph -0.25 cyl, though the check before that it was 0 sph, -0.5 cyl.

 

3

Many thanks. One eye test found my post op eye is +0.75 sph, -0.5 cyl, another found it was +0.50 sph, -0.75 cyl, but I know the strength can vary over the day, or perhaps eyes are on the border of the two measurements. 

I suppose the priority is whether to request the surgeon to aim at 0 for the next eye?   That sounds safer than requesting 0.5 as it might then come out at -1, which would probably mean wearing glasses for driving, cycling, walking etc.   The surgeon's idea is that I wouldn't need glasses for the above. 

Then after the 2nd eye is done, decide whether to request a very subtle adjustment down for the 1st eye.

The symfony lens sounds great.  I will ask the surgeon whether it is available in the UK and on the NHS, although it would be worth paying privately if there is a high chance of success.

My optician said that multifocal lenses have less contrast (could be a problem reading in dim light) - maybe that doesn't apply to the symfony ?    A friend is happy with trifocal iols, but still needs 1.5 diopter reading glasses, and he basically only needs reading and distance, not the mid - range as I do!

4

PS the reading from the other optician (I think this is possibly the more accurate one), was +0.50 sph, -0.75 cyl x 170, 6/6+

5

1. Actually, there is hardly any difference between the 2 readings. For all practical purposes, those are the same. One has usually more variation than that during the day. For example, when you get up in the morning, it is slightly different from what you have later in the day.

2. Regarding the laser enhancement, I have had good experience with that in both of my eyes.

3. If you had your cataract surgery recently, Your right eye is probably still changing changing. You may want to wait until your left eye has also gone through the surgery to make a final decision on your right eye.

4. I have a Symfony lens in my right eye for distance( and a monofocal lens in left for reading).  I have good day vision with the Symfony lens, but have had night vision issue of seeing multiple concentric circles around lights with Symfony lens. I have discussed this issue in my post, "Has Any One Else Noticed this Unusual Vision Issue with Symfony Lens" on this forum. Many other people seem to have had this issue. Rather than repeating that discussion here, you may want to read the comments there.

6

re: "That sounds safer than requesting 0.5 as it might then come out at -1, which would probably mean wearing glasses for driving, cycling, walking etc. "

If your other eye has good distance vision, then your binocular distance vision is likely to still be good. That  is well within the range of monovision many people have who don't wear correction for distance. 

Even for monocular vision for that eye, although studies only give average results since it depends on the person's natural depth of focus and other aspects of their eye, and it depends on the model IOL you got,  typical results would put monocular distance vision for someone with a monofocal IOL at -1D to be 20/40 or even 20/32 or better, so it  might fall into the 20/40 range acceptible for driving even for that eye. What is important is binocular vision, and again that should be good if the other eye is good. 

In my case it was the reduction in depth perception that steered me away from monovision. I'd worn monovision contacts to deal with presbyopia and like them, and not noticed any issues with depth perception as the difference between the eyes increased for a few years. However then I tried multifocal contacts and noticed things seemed more subtly 3D than they had before so I preferered that. However a minor amount of monovision, <= 1D is likely to not have much impact on stereopsis. Since my other eye has at least 20/15  distance vision, I figure even if I aimed for -0.5D and got -1D that it'd still be ok. 

Multifocals do reduce contrast sensitivity. Multifocal IOls are likel better than soft multifocal contacts due to higher quality optics. When I wore soft multifocal contacts I did notice reduced vision in dim light, e.g. trying to see the menu in a dimly lit restaurant I have a weekly meeting at so I was used to what it was like. However I never considered it to be a real problem, I mostly forgot about the issue after I first noticed it. Multifocal IOLs do split light and see some reduction in contrast sensitivity, thought the newest trifocals don't see much reduction, and the Symfony is better than multifocals due to its different optical design that extends the depth of focus rather than splitting it into multiple focal points.

The Symfony was a noticeable improvement in dim light over the multfocal contacts. Its contrast sensitivity is reported in a number of studies to be comparable to a monofocal, and others just show a slight reducton but still better or comparable to age matched subjects with their natural lens. 

Altough its only an anecdotal data point, I know someone here who is about the same age as me who got the Crystalens (and did a long writeup about it), which is a single focus lens which may accommodate a bit, but he sees more of a reduction in dim light than I do. In a well light auditiorum after a talk we met and he held a file folder over a near vision chart to cast a shadow, and it reduced his near by some lines, but didn't change mine a bit. 

 

Its suprising your friend needs readers, most people with trifocals don't. Perhaps 10-20% of people with the Symfony need low power readers, but most with trifocals don't since near vision is where they excel. There is a slight drop off in intermediate with a trifocal (though its still good usually, not as good as the Symfony), and I preferred that since intermediate is useful for computers and everyday social and household tasks, even for where to place your foot on a rocky/icy trail, etc. I figured I could always get readers for the occasional needle threading or other close tasks. 

In my case with the Symfony I have at least 20/15 distance vision (they didn't have a line below that to check and that was easy), at 80 cm its 20/20 plus a bit, and best near is 20/25. At 40cm exactly they didn't have a 20/25 line, so it was 20/30 but I saw some on the 20/20 line so its likely 20/25.

The Symfony is available in the UK, but I'd seen mention the UK only covers monofocals on the NHS. I'd considered going to the UK for my surgery a couple of years ago to get the Symfony.  I'm in the US where the FDA is slow about approving new IOLs and keeps us several years behind the UK and elsewhere. The Symfony was finally approved here 1.5 years after I got my surgery, though we still  don't even have any trifocals approved here. So I had to travel outside the US to get a better IOL, and Canada and Mexico didn't yet have the Symfony.   I wound up instead going to the Czech Republic, where I gather many folks in the UK go for medical tourism.

Google "High rates of spectacle independence, patient satisfaction seen with Symfony IOL" for one   summary of the major study data for the Symfony. Since the Symfony was new when I got it there wasn't much data out, so I keep checking out of curiosity to be sure I placed the right bet, and it all seems to confirm my impression of it. The better near for the trifocal is tempting when I see it, but in reality I don't usually need any more near so the better intermediate makes more sense. One study put the Symfony as having better acuity from 46cms out than the other premium IOLs at the time, a year or so ago I think. 

There is a risk of problematic night vision artifacts with any premium IOL however, a tiny but vocal minority, so there is the need to be prepared for a very tiny chance of a lens exchange with a premium IOL.

 

7

I am a high myope as well, and my cataract surgeon likewise told me that I was not a good candidate for multifocals (including the Symfony).

In my case, my right eye was so myopic that no toric or multifocal lenses even existed in my required power — I needed a +3.0 D lens, but the available premium lenses in the US seem to start at +5.0 D.

I don't know what power you need, as the formulas are based on various parameters and are apparently less accurate for high myopes.  However, a website says that the old 1977 state-of-the-art for power estimation (prior to modern IOL power calculations) was simply to add +19.0 D to the pre-cataractous refraction.  If your original prescription was -15.0 sph, that would indicate something like a +4.0 D lens.  Not sure whether there are multifocals in that range for you?

Even though my left eye was barely (+5.0 D lens) in the range for premium lenses, my surgeon still did not recommend a multifocal.  I wound up getting a toric lens in that eye.

I'm not sure about the exact reason against multifocals in my case, but the OD (who is different from the surgeon) thought that one reason might be related to contrast sensitivity.  I seem to remember reading that high myopes may have a higher predisposition to macular degeneration, so I would be loath to get any lenses that would reduce contrast sensitivity.

8

I have a related question on this.  I remember reading somewhere about multifocal lens not recommended for people who have had lasik (perhaps due to thinning of the cornea) but maybe it also depends on how much thinning.  My question is if this is true, then could one be more likely to develop more complications with a multifocal / premium lens down the road even if they have lasik (or maybe PRK) AFTER a cataract?

 

9

The only issue regarding the cataract surgery after LASIK is that the measured cornea readings may be slightly off at the time of the cataract surgery, which may make the calculated value of the IOL power to be slightly off. Thus, the standard recommendation is to be sure that there is a good record of the cornea readings before and after LASIK so that the related information is available at the time of the surgery.

Other than the fact that any surgery, including LASIK, has a risk (although very small for LASIK), there is no additional risk because of having LASIK done after the cataract surgery. Just for reference, my eye surgeon includes free LASIK enhancement after a multifocal, toric, or any other premium lens. Of course, that made it a very easy decision for me to have a LASIK enhancement after getting a Symfony toric lens. I needed that primarily to correct the remaining astigmatism and I am glad that I had that done.

10

​2. Perhaps monofocal iols, followed by a laser touch up to bring the left eye's over-correction down to the range 0 to -0.5, and the left eye also adjusted if necessary, is the safest option.  

3. My left eye was had cataract surgery in mid October - might it still be changing ?

4. It does seem as if any premium lens, including the symfony, has some risk of seeing concentric circles around lights at night.  That could be a problem for driving. My optician also mentioned premium lenses give less contrast, although a friend is happy with Trifocal iols, but still 1.5 diopter needs reading glasses.  

5. Am I right in thinking there is a very low risk with a small lasik adjustment, because the degree of thinning involved in the procedure is very small ?

 

11

I may have been a little confused, but I thought that you have had the cataract surgery in your right eye and are going to have the cataract surgery in your left eye in July. Will appreciate it if you can clarify that so that I am saying the right thing when I suggest any steps.

Have three other questions for you:

1. Which is your dominant eye; right eye or left eye?

2. Are you open to using some amount of monovision, where the eyes have the best focus in slightly different regions? I have had success with this and don't need glasses for reading or intermediate or distance. However, others may have some difficulty in having their brain used to it (it took me about 5 minutes to adjust to it when I first tried it with contact lenses)

3. How important is it for you to not have to use glasses for reading or for intermediate distances?

Regarding your question about LASIK, there should be very low risk of using LASIK enhancement because the required re-shaping of the cornea should be small. Any way, when the time comes, the LASIK surgeon will evaluate that during consultation (which many LASIK places offer free of charge).

12

Thanks for checking - the left eye was done in October, the right is scheduled for July this year.  

1.The right eye is dominant.

2. I would like to try monovision, but would prefer not to have this with iols as it wouldn't be reversible if I didn't get used to it, would be difficult to work properly during a trial period, and I think a lens exchange might be too risky, as I am very myopic (about -15).   

3. I don't mind using glasses.  My concern is how I will manage focusing on distances from close reading and mobile, to reading music about a metre or yard away.  Varifocal glasses are probably the answer, but they make take time to get used to.  Previously I could read and see in the distance (slightly under-corrected) with a single pair of glasses, and am using my right eye with the old -15 glasses at the moment.

13

If there aren't premium IOLs in that range, someone could usually get a laser correction afterwards to bring them into that range, and those who are extremely myopic are likely going to need one any way due to the lens power being off if they are trying to avoid the need to wear correction for some distance. For those who need a toric lens, I'd read that perhaps 29% or so wind up with >0.5D of residual astigmatism and are likely also to wish a laser touchup anyway. The Symfony is more tolerant of residual astigmatism than a monofocal in terms of the resulting visual acuity, and more tolerant reportedly than   multifocals.

  

Just as with phones and computers, technology improves all the time. Unfortunately some surgeons had poor experiences with early multifocal IOLs and haven't given newer technology a try, including things like the Symfony that aren't actually multifocals (even though they use diffractive optics which confuses some people). Some surgeons are inherently conservative and would rather never hear a complaint, even if it doesn't give patients an option they might be happier with in the long run. 

For many patients even the minuscule risk of a lens exchange isn't worth it, while for others like me the idea of perhaps rarely needing correction the rest of my life (after having been a high myope needing it all the time, though not as high as you folks) is worth some risk. 

 I have noticeably better dim light vision with the Symfony than I did with multifocal contacts before I had a cataract, and I had no complaints with multifocal contacts (nor do many others) even though I noticed the difference in dim light when I first tried them. Its rarely a  problem so I just never thought about it after noticing it.

There is some loss of contrast sensitivity with multifocals due to light splitting, though less so compared to older multifocals. The Symfony makes up for extended its depth of focus via correcting for chromatic aberration which overalll leads to little loss of contrast sensitivity. Overall some studies show it as comparable to monofocal control IOLs, or at most merely a slight reduction but still better than the average person the same age with a natural lens due to the reduction in image quality with a natural lens even when it doesn't officially yet have a cataract (though the results I saw were for those a bit older, I'm guessing for those in their 40s or 50s like me it may be a very slight reduction, made up for by the greater range of vision).

Monovision can also reduce contrast sensitivity in lower light for some distances where you are only using one eye because you don't have two eyes gathering light. 

I figured in the unlikely case I did have some other eye health issue develop in the future, that I could get a lens exchange to a monofocal, but that the odds are high I'd never need it. However everyone's risk tolerance is different. 

14

In addition to concerns over the lens power being more difficult to get right after lasik, the concerns are usually over earlier generations of laser correction where the cornea may have been left more irregular and less smooth than modern methods (picture by analogy a high resolution display screen where you can't see the pixels, vs. a lower resoltion one where you can see pixels and images aren't as smooth).

Although some surgeons who aren't up to date  or don't have the equipment may rule out a multifocal for someone with past laser correction, better surgeons can do eye scans to look for the size of irregularities, the higher order aberrations, to determine whether a diffractive IOL (a multifocal, or the Symfony extended depth of focus lens) would be a problem (though it shouldn't often be with the Symfony, it takes fairly large irregularities to cause problems for it). 

The corrections made after cataract surgery now are usually small (which means even those with corneas too thin for large corrections are candidates) and are done using modern technology which leaves the cornea regular enough to interact ok with a diffractive lens. 

I'd read that some surgeons prefer PRK rather than Lasik after cataract surgery, but not all, I hadn't explored the reasons other than that its a smaller correction than people usually get done with a laser.

 

15

re: 3, usually its only 3 months after surgery before they consider a laser enhancement. In this case though again I'd suggest doing the IOL in your other eye first to see where it winds up. I'd suggest a contact lens trial now perhaps to consider where to target that eye, and whether to go for a premium lens,  then doing a contact lens trial after the 2nd eye is done to decide on level of laser correction.

re: "the left eye also adjusted if necessary, is the safest option. "

It is the lowest risk option in terms of not needing future surgery. Everyone needs to decide based on their own risk preferences.

The risk tradeoff is that a monofocal IOL is guaranteed to provide a lower range of good vision than a premium lens, while there is a tiny risk with a premium lens of problematic night vision artifacts leading to another surgery.  A larger range of vision is a safety issue in that it leads to less distracted time driving when trying to see dashboard or maps, and studies show progressive(/varifocal) glasses reduce reaction time due to the need to move the head and not merely the eyes, and that in the elderly monovision correction or progressives or bifocals lead to a higher risk of falls (due to either depth perception reduction in monovison, or looking through the wrong part of glasses, etc). 

 re: " It does seem as if any premium lens, including the symfony, has some risk of seeing concentric circles around lights at night. "

Yup, though the risk is very low with the Symfony (but unfortunately someone winds up being the "statistic" and posting about it, and some who do seem to have trouble grasping that others really don't have the same problem). Even many folks with monofocals have trouble with halos, they are merely shaped differently, and the odds aren't that much different with the Symfony.

I addressed 4 in other posts. re: 5, yup the risk is lower with smaller corrections.

16

I think it probably best to have my right eye cataract done, and to wait to see the resulting prescription after a month or two.  

Then to ask the surgeon to reduce the strength of the monofocal iol in my left eye, as I am not very comfortable with it being at +0.50, cyl -0.75.   Distance is clear, but not mid distance - eg the tv isn't in focus at about 9 foot away.  

If the margin of error is plus or minus 0.5, then I suppose it could be reduced from +0.5 down to 0, and then if it overshoots, it will end up as -0.5, which would be fine.  

(The surgeon said a reduction from 0 down to -0.5 is not a good idea, lest it goes down to -1 and I would then be back for another touch-up).

I could make another appointment specifically to ask him this, and also whether he could look into the suitability of the symfony lens - although the reduced contrast might make reading in low light conditions awkward - or if I developed macular degeneration when older - if this is more likely for high myopes ?  

 

17

re: "I would like to try monovision, but would prefer not to have this with iols as it wouldn't be reversible if I didn't get used to it, would be difficult to work properly during a trial period, and I think a lens exchange might be too risky, as I am very myopic (about -15).   "

Monovision with IOLs is reversible with a laser correction. Again, I'd suggest a contact lens trial beforehand (though it depends on how bad the cataract is in your other eye how accurate that would be, and if you are young enough to retain some accommodation in your natural lens in that eye it wouldn't be quite the same). 

If you work at a desk job then monovision shouldn't be a problem, and regardless you can always wear correction over it while working to balance it out while you adapt in non-work time. Most people adapt quickly. I'd suggest its likely harder to adapt to progressive(/varifocal) glasses than monovision. I mostly wore contacts before surgery and only wore glasses rarely as a backup, so I  didn't wear progressives long enough to adapt to them, though I tried to force myself to wear them fulltime for a week or two I think it was to at least be somewhat used to them.

Although its true that a high myope has higher risk of some complications after lens surgery, the risks are still very  low. In fact at least one study suggested that high myopes actually don't have a higher risk of retinal detachment after modern cataract surgery, that they merely have a higher risk to begin with and that the surgery doesn't noticeably change that. Unfortunately some of the data on retinal detachment that serves as scare stories is very old and based on the far more traumatic older generations of lens surgery before modern equipment and techniques. Lens exchange isn't exactly the same as cataract surgery, but not much different aside from the need to chop up the artifical lens, but that is distant enough from the retina that its unlikely to change the stats much.

In terms of halos, I recently ran into this article giving perspective and making me wonder if they should be comparing incidence of halos with phakic eyes in studies and not merely vs. a monofocal control:

"The study, titled Needs, Symptoms, Incidence, Global Eye Health Trends (NSIGHT), surveyed 3,800 spectacle and contact lens-corrected subjects, 15 to 65 years of age, from seven countries (China, Korea, Japan, France, Italy, United Kingdom and the U.S.) to better understand the eye-related symptoms that vision-corrected patients experience. The NSIGHT data provided valuable information on how often patients experience halos and glare and the degree to which they found them bothersome. 

About half of the spectacle and contact lens wearers surveyed reported suffering from the symptoms of halos (52 per cent and 56 per cent, respectively) and glare (47 per cent and 50 per cent, respectively) more than three times a week. More than four of five patients who experienced these symptoms found them bothersome (84 per cent and 89 per cent for halo and glare, respectively). " 

18

Thanks for the information.

I think that the following straightforward approach may work out best for you:

1. Since you need only a slight change in the presciption for the left eye (you are probably seeing close to 20/20 in that eye right now anyway), you should postpone any laser enhancement in that eye for 5-6 months. By that time, your vision in the right eye also would have stabilized after the cataract surgery. which may affect the best choice for the left eye.

2. There is more than one way to do it, but my suggestion would be to target the right eye for about 40 inches distance (which corresponds to about -1.0 D spherical correction). If that is achieved and you don't have an issue with the slight amount of monovision (most probably, you won't), you will probably be seeing better than 20/25 at distances from 26 inches to far away. If you find that the monovision does not work at all, you can get LASIK enhancement to get the best focus to about -0.5 to 0 D range (just as you may get LASIK enhancement to correct any significant astigmatism or deviation from target, as you are planning for the left eye).

If the above approach works, you will still be using glasses for reading, but that is relatively easier to do.

19

I have also read of conservative surgeons who avoid multifocals due to possible complaints, but that's not the case with my surgeon. I know that he uses Symfony IOLs for other patients, but he did not recommend it in my case.

It is still early for me, so I don't have a post-operative refraction yet.  However, the monofocals are quite acceptable in terms of spectacle reduction, which was a surprise because I was much more interested in the Symfony before talking to my surgeon. The astigmatism seems to have been effectively corrected by the toric lens in my left eye and by LRI in my right. I seem to be myopic in both eyes but more myopic in my right.  That results in a quite usable range, as I can see distance clearly with my left (and acceptably with my right), whereas intermediate vision is quite clear with my right (and acceptable with my left).

I can drive and use my desktop computer comfortably without glasses.  I can also use my phone at arms length, though it helps to bump up the font size a bit. Reading glasses are necessary for small print and long reading sessions, but that's fine.

Night vision degrades in my right eye but seems fine in my left, which has a different IOL design (aspheric) than my right. So night driving is comfortable using both eyes.  While driving, I can see both distance and intermediate (GPS) just fine.

In terms of numbers, I was at 20/40 (one week out) right eye and 20/25 (one day out) left eye.

I guess I'm saying that being left slightly myopic (with astigmatism corrected) post-op, with one eye more for distance and the other more for intermediate seems to have worked out so far in terms of usable range.  Hopefully it stays that way.

So, for r28705, I would also think that targeting slightly myopic for the other eye might be more useful than targeting 0 D. That also might reduce the chance of winding up hyperopic in the remaining eye as well.

20

I could ask the surgeon to aim at -0.5 in the other (right) eye, but am not sure if there is a risk it might then come out at -1, as there is a margin of tolerance, especially if you are highly myopic?   Not an easy decision!  decision !