Choosing Target Distance for IOL When Spectacle Dependence is Unavoidable
Posted , 7 users are following.
All the discussion about what IOL to choose seems to revolve around maximizing spectacle independence. So, it's all unhelpful for me, because I have more corneal astigmatism in the right eye (-8.25) than any IOL can correct. Given I will always wear glasses even after surgery, I am thinking I should ask for intermediate targeted IOLs, on the theory that that will give me the best with-glasses reading and computer vision. Is that theory sound?
My doctor recommended toric IOLs, targeting distance, and I did not engage him in much discussion on it. But upon reflection, I wish I had, and plan to next time I see him. Isn't it true that I will get my best reading and computer vision if my IOL target is intermediate? Progressive lenses are a compromise at best. They bother me most when reading and using the computer. So wouldn't it be best if the glasses were doing zero correction in that zone?
My full prescription now is Right: -3 sphere, - 8.25 cyl, , +2,25 add. Left: -5 sphere, -2.25 cyl; +2.25 add. I also have prism 1.5 BU right, 1.5 BU down. The docs think the diplopia is an artifact of the very strong and very-different-between-the-2-eyes spectacle lenses. They think prism will not be necessary once most of the correction moves into the IOLs.But toric IOLs can only handle about -4 cyl (they go to -6 cyl but that's equivalent to -4 at the cornea.
LASIK is not an option -- the cornea is too thin as it is, so you would not want to shave anything off it to reshape it. The diagnosis for the right eye is pellucid marginal degeneration -- kind of a beer belly in the cornea. Nevertheless, the eye doc says the astigmatism is regular where it matters, in the small central area I see out of. Regular, but huge.
I've had topography done at regular intervals for many years. The conditon is stable.
I'm 72. My occupation requires a lot of computer work. I also like to read and write.
My decisions will not be constrained by cost considerations. I saved enough to retire early and then didn't retire. I'd gladly pay many thousands for any improvement in vision.
I live in the Boston area, so have easy access to top-notch docs. There is a Massachusetts Eye & Ear Infirmary office within walking distance of my home.I went elsewhere for my first cataract consultation, because I thought I wanted light-adjustable IOLs and MEEI does not do that. But I was told light-adjustables would be a poor choice for me because (a) they don't go as high on astigmatism correction as non-adjustables and (b) why go to the trouble and expense of light-adjustables when you're going to wear glasses anyway? -- Whatever error there is in the IOL can be counteracted by the new glasses prescription. I could do light-adjustable for the left eye, which has astigmatism within range of what toric light-adjustable IOLs can handle, but it's pointless if I don't have a goal of spectacle independence.
I've been wearing progressives for decades. The reading experience is not good, so I've switched to mostly audiobooks. I'd love to have good reading vision again.
I am a precise kind of person. I notice all the shortcomings of my vision. I don't like the distortions that result from the high-power progressives. I would like my world to have straight lines again. I would like to see characters clearly on the page with both eyes at once. I would like a larger reading corridor. My optometrist has remarked that small tweaks on my prescription at each annual exam matter more to me than to most other people. She says "You notice small errors that others would not, and your are very consistent about what's better what's worse when I test you repeatedly on small changes to your lenses. Most people would not spend the money to get new glasses for the small improvements that seem to matter a lot to you. They wouldn't even notice."Then she gives me the new prescription she says should make very little difference and I see dramatic improvement.
1 like, 35 replies
Myope_PSC jimluck
Posted
I just searched for 12D cyl Toric IOLs and got results so maybe expand your IOL brand considerations.
For computer vision, single vision lenses are great. I hadn't thought of doing that before until David mentioned it a while back. I used progressives before surgery might get progressives now that I'm post-op but I'll probably never use them for computer use other than a quick glance. My +1D dollar store readers give a much better computer viewing experience than my progressives ever did so real single vision glasses that also correct residual cylinder should be fantastic.
jimluck Myope_PSC
Edited
You're right! Thank you!But it seems there's a potential catch -- everything I find on high-cylinder toric IOLs is from other countries.I can't find anything on them suggesting availability in the USA.These are all custom IOLs. Nothing off-the-shelf goes that high. But apparently, in Europe and India at least, custom high-cylinder IOLs are available. I have sent emails to two of the manufacturers in Europe asking if they work with any doctors in the USA.It might be that they are not approved by the FDA. I may need to become a medical tourist!
RonAKA jimluck
Posted
The other thing to consider is that the effectiveness of toric IOLs drops off very rapidly if they rotate even small amounts out of position. I would expect that the higher the toric cylinder power the more sensitive they will be to this effect.
Dave13852 jimluck
Posted
Hi Jim,
What target diopter would you want targeted for the intermediate vision?
jimluck Dave13852
Posted
I don't know that terminology. I would target 2 feet.
RonAKA jimluck
Posted
You can estimate the peak vision distance of a myopic target power by dividing 1 meter by the myopic power. For example -2.0 would give you half a meter or about 18", and -1.5 D would be 2/3 of a meter or about 2 feet. I find -1.5 D gives you pretty good reading but some +1.25 D readers on top of that are needed for very fine print in dimmer light.
RonAKA jimluck
Edited
An interesting and somewhat challenging situation. Off the top, have you had your eyes measured for IOLs and what cylinder correction is needed? It seems your high astigmatism is based on the eyeglass prescription, which is not always an accurate predictor of the degree of cylinder needed in an IOL. Some of the astigmatism may be in the lens which will be removed in the cataract surgery. Regardless I think it would be a good idea to get a toric which will correct as much of the cylinder as possible, and leave as little as possible for the eyeglasses to correct.
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The pros of correcting sphere fully for distance is that the prescription in the top part of a progressive eyeglass lens will be minimized. Myopic corrections result in lenses that are thin in the middle and thick at the edges. This of course can be minimized with high index lenses in your glasses. Choosing an intermediate target like -2.00 to -2.5 D would potentially allow you to read without glasses depending on the residual astigmatism. It would also minimize the correction in the lower half of a prescription lens to essentially zero. So there are pros and cons to each way of going. I think there is always benefit in asking yourself "What do I want to see with my glasses off?". That may guide you in your decision. I would postpone that decision until after your eyes are measured so you will know what the residual astigmatism really will be.
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As for a lens you may want to consider a B+L enVista Toric. It is a bit different than other monofocal IOLs in that it has a neutral (zero) SA correction in it. Tecnis uses -0.27 um to theoretically correct SA to zero, and AcrySof has -0.20 um. B+L claims a neutral correction which will result in a total SA of +0.27 um in the average person is more tolerant of less than perfect eyes. To get more information try a google search of the following:
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enVista Simplifeye Brochure pdf
RonAKA
Edited
You could also get real fancy and target a mini-monovision solution for close to intermediate vision without glasses. Perhaps a -3.0 D in the non dominant eye, and -1.5 D in the dominant eye. I find that my eyes can easily handle a difference or anisometropia of 1.5 D. That would give you good vision from about 8" to 3 feet without glasses if the residual astigmatism is not that bad.
jimluck RonAKA
Edited
Thanks RonAKA. My eyes have been measured up the wahzoo with all the fancy instruments and I have many pretty color pictures to prove it.The astigmatism is all in the cornea, I surmise from all the conversations I have had, though I have not asked exactly that question. But my messed-up cornea is all they talk about and they say I will have lots of residual astigmatism in the right eye with torics, but not the left. They say the best vision would be achieved by scleral contacts and no cylinder in the IOL, but then I'm wedded to contacts for the rest of my life. I'm going to give them a try before deciding on my IOL. They assure me they are very comfortable and effective, buy obviously a bother to put in and take out and care for.
Dave13852 RonAKA
Posted
Ron,
Only 3 feet without glasses even with 1.5D in one eye? I know the formula for the near vision but is there one also for the distance vision i.e. how you calculated 3 feet without glasses in the last example you gave for Jim with the monovision?
RonAKA Dave13852
Posted
I only gave rough estimates. If you want to know more exactly the range of good vision (20/30 for example) you have to look at the defocus curves for the specific lens you are considering. I just gave numbers for a typical monofocal. I have one -1.5 D eye and I can see TV reasonably well at 8 feet or so, but it is certainly more crisp with my 0.00 D distance eye. There is quit an individual to individual variability on how well one can see in off focus distances.
jimluck
Edited
Could someone please explain the cylinder range being offered for these 3 IOLs on the Zeiss website?
One type goes from -10d to + 32 cylinder, and the other two go from +1 to +12.
My glasses are -8.25 on the right side. So a naive reading of this would say only the first type would work for me. But I have read elsewhere that positive and negative notation is used for cylinder and they are equivalent, in some sense.
I don't think these are approved for use in the USA.
RonAKA jimluck
Posted
These IOLs provide an unusually wide range of powers. Normally an IOL ranges from +5 to +30 D for sphere. These would be suitable for someone that is a -11.0 or so on eyeglasses to about +8.0 D. The AT Torbi 709 seems to be able to go from -10 D to +32. On the hyperopic (far sighted) end that is similar to other lenses but a -10 D would be for someone that is extremely myopic. I didn't even know that IOLs went into the minus range. This would be for someone that is about -22 D myopic!
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On cylinder it appears these lenses go up to +12 D. Sign does not matter as they all have a high spot and low spot. IOLs are just implanted at the angle that offsets the high and low spots on the cornea.
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Assuming you do not want a MF the AT Torbi 709 would be the one you would be looking for. Detailed specs can be found by googling this:
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at torbi 709 datasheet en pdf
jimluck
Edited
Now I am pursuing options abroad, since no IOL approved in the US has enough cylinder correction for my astigmatism. The most promising option seems to be Canada, being both the closest foreign country and one where I have family to visit.I called the Canadian distributor for HumanOptics, a European lens maker which brags it has provided custom IOLs for patients needing up to 40 d cylinder in their IOL.
The distributor would not give me names of doctors who have used their lenses but did give me names of hospitals and clinics. I called them and got doctor names and in one case the Herzig clinic in Ottawa and Toronto, I got as far as talking to someone and sending her my topos and other ophthalmological records.
Then I emailed my ophthalmologist and told him what I was doing and asked for his help in choosing which foreign doctor to trust with my right eye.He replied (on a Sunday!) the he knows Dr. Herzig and will get in touch with him to discuss my case!
Meanwhile I learned something else: While emailing with an Ophthalmologist in Zurich he looked at my topos and said I only need a 7 cylinder.I thought I would need a 12, because my glasses are 8.25 cylinder and I read there is a 1.46:1 relationship between IOL cylinder and equivalent glasses cylinder. So I recounted all this to my local ophthalmologist in another email and he said "Your topo shows 6.6, which means your IOL will need to be about 10. We, of course, will calculate this many more times before making a final lens selection."
RonAKA jimluck
Posted
Yes, an IOL power of 10 D gives about 7 D at the eyeglass plane. I would ask for the IOL calculation printout from the IOLMaster 700 program. It will show what you need.
RonAKA jimluck
Posted
One place you might want to consider is Visionmax in Edmonton. There is a Dr. Senekal that is very experienced. He started out in South Africa and has studied in Europe so he may be familiar with the lenses you are interested in. Both my wife and I had cataract surgery in his clinic but not by him. Our surgeon has his own office but seems to rent time at this clinic to do surgeries once a week. This clinic is in the very south part of Edmonton about as near as you can get to the airport (the airport is 25 km south of Edmonton), and the clinic is within walking distance of some hotels.