High myope facing 2 x cataract surgery - lens choice?

Oops, I meant its common for people with monofocals to need to wear correction for 2 of 3 distances (depending on where their monofocals are set for). The only reason for correction for all 3 distances is if either they have residual astigmatism which wasn't addresed in surgery (via a toric lens or incision), or if the lens power was off (and they didn't choose to correct it via laser). Usually the lens power choice is fairly accurate for most people, but there is some chance it'll be off, and the risk is higher with high myopes. Monovision can often provide vision for 2 of the 3 visual ranges, and for some minority of lucky people all 3, but its best not to expect all 3. Its best to plan for average/typical results, be prepared for the worse, and hope for the best.

 

I'm currently using contacts that correct for my nearsightedness (-14, so 20/40 would be a massive improvement), hobby was flying, which I started in a country less lenient than my current one (UK), I would want a class 2 medical though, which is pretty clear on multifocals not being permitted. I've always had issues with glare and halos, so that would be a major drawback of a multifocal implant. If I have to have my eyes cut open I want to see some improvement and not be significantly impaired in another way. As I indicated, quite young so want to make sure the choice I make is a good one :-)

Since the US allows pilots to have  multifocal IOLs, it seemed surprising the UK didn't also. So I checked out of curiosity (I do expect to get a pilot's license someday, I started in the past and then got too busy and hand't gotten back to it). The UK's CAA does explicitly state: 

"Note: multifocal and bifocal implants are NOT compatible with certification.  Monovision is not recommended and pilot would require well-tolerated multifocal spectacles in order to meet the distance and near vision standards.  Accommodating lenses may be acceptable following a review with a consultant aviation ophthalmology adviser."

That suggests that the Crystalens accommodating lens might be an option if you'd like to try for more of a range of near vision than a monofocal allows (though that would be an out of pocket cost to get a premium lens). Although it merely says "Monovision is not recommended" rather than saying it isn't allowed, I notice that in their section on presbyopic correction that they say:

"The following types of contact lens correction are not acceptable:

Monovision – this is where the dominant eye is fully corrected for distance and the non-dominant eye is corrected for near.  The distance visual acuity in the ‘reading eye’ will often fall below the appropriate acuity standard.  It can interfere with depth perception and does not give optimum distance vision."

The fact that they don't allow   contacts using monovision makes me wonder if in the future they might ever change things and   explicitly disallow monovision with IOLs, or if they'd merely only "not recommend" it (though I guess if they disallowed it with IOLs, then laser correction could get rid of the monovision). 

I'll note that their guidance for presbyopic correction indicates that they don't allow the use of reading-only glasses, that all glasses used for rading must include distance vision as well, i.e. bifocals, trifocals or progressives/varifocals. 

I will note that their guidance notes that "All IOLs must be monofocal.", and explicitly disallows multifocals. However that seems to merely mean one focal distance (rather than multifocal) since it then goes on to suggest that accommodating lenses can be acceptible. That raises the question of where they stand on the Symfony since it is *not* a multifocal, it merely extends the single focus range farther. If  that were of interest it might be worth getting confirmation from them, its possible the ambiguity might mean they leave it up to the examining doctor.. or that it isn't allowed.    It uses diffractive optics, which lead some doctors who are more knowledgeable about medicine than optics to confuse it with multifocals, but it is viewed as a different category. The FDA data for approval of the Symfony and the Crystalens actually suggest there may be less risk of problematic halos&glare with the Symfony than the Crystalens (though comparing 2 studies can be misleading since they may ask questions differently and have different patient characteristics). 

Your issues with halo&glare likely relate to having required a large prescription. Unfortunately there is no IOL yet which has no risk of halos&glare, even monofocals give problems for some people. The Syfmony does have a risk  of halo&glare issues comparable to monofocals, though not as low as the best monofocals like the Tecnis one usually used as the control lens for it in studies. In my case I decided since I was 52 when I had surgery (not as young as you, but still potentially living the results for a few decades) it was worth the low risk since I could  get a lens exchange to  a monofocal if needed, and if I didn't need it then I'd benefit with for decades with a more convenient range of vision. I was old enough that I did have experience with the issue of losing near vision due to presbyopia, and definitely didn't like the thought of losing even more due to cataract surgery. I'd already been battling it using multifocal contacts, and didn't like progressive glasses. 

I recall before I had my surgery that there was  dispute in the literature over whether the Crystlens is truly an accommodating lens, even though its placed in that category, or whether rather than actually moving to change focus if it is really merely extending the depth of focus statically.  They seemed to have difficulty actually getting confirmation the lens moved at all, though its unclear if its not moving why some patients would see no more near than a monofocal. I don't know if the issue was ever resolved, i hadn't looked into it recently.

 

1. Unless there is something else wrong with your eyes, you should be able to get 20/20 distance vision (which is 6/6 in metric system) after cataract surgery using monofocal lenses, although like for many others (including me), the eyes may need LASIK enhancement for the correction of astigmatism and possible errors in the IOL prescriptions.

2. Each of the two eyes can be set to achieve the best focus at whatever distance one chooses.

3. Thus, if you can use monovision, you may be able to set the dominant eye for best focus at distance while the other eye is set for the best focus at about 18 inches. This is essentially what I have. The Symfony lens gives me more  range in the right eye for good focus than a monofocal lens, but before that, I could work fine with the contact lens in that eye without significant natural eye focus adjustment (which is what I would have achieved with a monofocal lens in that eye). Stated another way, setting the monofocal lenses for different distances can help you achieve what one achieves with the multifocal lenses without the glare or halo problems associated with the multifocal lenses. In either case, you have good vision in 2 small distance ranges, but one can choose what those need to be.

4. The big question is whether your eyes / brain can adjust to monovision. It took me less than 5 minutes to be comfortable with contact lenses set for that. But other people have issues with that. In you case, since you are wearing contact lenses, you can try using a contact lens set for about 18-20 inches on the non-dominant eye for a day or two to see if you have any vision issues. (the prescription for this eye will be less powerful by about 2.0 or 2.25 deiopter than what you have now). If you don't have an issue with the 2 eyes set for different distances, the monovision may be a good choice for you.

5. However, please remember that unlike many others who have cataract surgery at an age where they are used to not having much of a natural focussing range, it is likely that you still do. Thus, although with 2 monofocal lenses and using monovision, you will be able to achieve results similar to multifocal lenses at 2 distances selected by you, everything will not be in good focus from 16 inches to infinity.

Just to add a little to what I said above, if you can use monovision and want to use monofocal lenses, the best target focus distances for each eye may depend on the range over which you want a good vision without glasses and the range over which you are willing to use glasses, if required. Just as an example, if depending on your life style, you will like to have good vision from about 16 inches to about 80 inches (which allows to not used glasses most of the time you are home), but are willing to use glasses for distance, you may want to have the best focus distance for the dominant eye at about 40 inches and the non-dominant eye at about 18 inches. If you achive 20/20 at these distances, you will probably have at 20/25 or better vision between 16 and 80 inches, but it will probably be about 20/40 at large distances (thus requiring glasses for driving etc). You should give this some thought because if you think that you would prefer this, you may want to try contact lenses and glasses combination to achieve this. Actually, this combination may be easier to get used to. Also, with this combination, there will be less difference between the vision range achievable with this combination versus what you will achieve with the two monofocal lenses.

The major issue with monofocals is figuring out what distance range you'd prefer to not need correction for, expecting to wear correction for the others. The default is to set them for distance, which is partly I suspect because it  means if somehow your glasses break then you can still see to drive (or fly) except for struggling with dashboard/map, though keeping spares around alleviates that concern. 

If you do go with monofocals,  even though the CAA doesn't recommend monovision (and seem to expect you to wear glasses that correct it while flying, so you are using both eyes for every distance an depth perception isnt' reduced, and of course you should wear such correction often enough to be well adapted to it). It might be worth considering at least a bit of monovision and then if the CAA ever disallows it getting a laser correction. If I hadn't gotten a premium lens, I likely would have gone for monofocals set to make it easy to function at home/office/computer. The distance a lens focuses best at in cm is (100 / -dioptric_power), but you get some level of decent vision a half diopter or so in and out from that (depending on the monfocal and the person).   I'd likely have set one eye around -0.5 (focusing at around 2 meters = 6 feet 7 inches)  which would allow good walking around vision, even at distance it might be good enough to match  the  driving standard (but just in that eye) and the other at -1.5D (focusing 67 cm = 26 inches) to not have too much of a level of monovision, but have that eye for computer distance  and  between the two eyes good for most social interaction distance and  good enough for many household tasks, even if not for much reading. That would have left a need for glasses for driving and reading.    I usually use desktop computer monitors which are a bit further away than most people use laptops, so a little closer in, -1.75  might be good for a laptop, or even -2 to deal with laptop and perhaps smartphone (though increasing the level of monovision makes it harder to adapt to, thats still in the range most adapt to, but the more you have the more you only use 1 eye for a particular distance and the less stereovision you have).

One problem in your case is that you are a high myope, which means there is more of a risk that the lens power choice will be off a bit. They can fine tune it via laser correction afterwards. However   another option might be to look into the light adjustable lens, which is usually done as a single focus lens but where they can modify the lens using a special UV light that alters the lens after it has been implanted to fine tune the correction before making it permanent.  Its not the most convenient procedure since you need to wear special UV glasses for some days to shield the lens  until they finish adjusting it, and then they alter the lens so UV won't change it after that. I haven't examined the details on the lens to know how its other attributes compare to other monofocals like its risk of halos&glare. I know they are doing research on putting extended depth of focus patterns on the lens, but I haven't seen any published data on it,  and you'd also need to see if the CAA would aprove that use of it. 

There is data around the net showing the average vision you get with whatever IOL model you consider vs.  how many diopters of defous (which can be converted to distance), often in a graph called a defocus curve showing visual acuity vs. distance (though the 0 point of the graph starts wherever your IOL is focused at). Unfortunately it can be hard to assess what a particular visual acuity means in terms of subjectively how blurry it is. However if you google

"The following is a list of environmental print that correlates to the acuity on a Near Vision Snellen Test Chart. " it gives some idea of what visual acuity allows you to read what size print.

I should add one of the reasons I mentioned the light adjustable lens is that I don't know if your prescription is stable. Most people's vision stabilizes by their late teens/early twenties, but some small minority don't see it stabilized until their late twenties, and some high myopes can see minor fluctuations even after that after that. Although people can get laser correction multiple times (sometimes they require a fine tuning laser adjustment), its best to limit how often you do it since its not a perfect procedure. I figured someone young might consider the light adjustable lens to get the refraction right to begin with, and then if their prescription does shift over years or decades, get a laser touchup later if they wish to avoid correction. However as I said I hadn't checked into the details of the LAL enough to be sure how it compares to other monofocals, since it may  still be  better to use a good monofocal and get laser correction if needed.

 

Cheers all, and Sue, you touched on my main concern about blurriness for close (how blurry is blurry), and you've reassured me that it's not my current kind of blurry :-) I'm told my surgeon is good, so fingers crossed. I've had a stable prescription for the last ten years, so the initial cataract (rapid onset) took me by surprise. I currently have one very blurry eye even with correction (cannot see top line of eye chart - other than black something against white), so can't test out monovision - although that's likely what I could consider my current vision. I find it quite tiring with the blurry eye when reading and driving. LASIK was ruled out for me years ago, my corneas are too thin, so not sure much correction can be done post surgery, as it is they need to work on my retinas before the main surgery. Discussions with surgeon to come on lenses and what's best, I may well need to let the flying go completely if his recommendation is for lenses that are not approved. I could always fly with friends, not the same, but eyes more important :-)

A minor laser correction post-cataract surgery of a diopter or less is vastly different from a correction of 14 diopters or so.  I'm sure you have some idea how thick your glasses need to be compared to those with low prescriptions, similarly there is much more tissue altered with a large laser change than a tiny one. It is very possible minor tweaks after cataract surgery  would work for you, I'd suggest checking on that. I'd also suggest you consider talking with an opthalmologist who does pilot medicals about whether they might allow the Symfony, or at least to confirm that there would be no problems with the Crystalens.

It is true that whatever happens, your vision at distance and intermediate are likely not going to be anything like the blur you have now without correction. Even if you need to wear correction, glasses and contacts will be thinner.  

Sue posted decent results, but again results vary with each person so its good to hope for the best, plan for average, but be prepared for the worst. 

Ultimately unfortunately it will be up to you and not just what your doctor recommends (and you might consider getting more than one opinion if possible, given you'll live with the results a long time perhaps), which is made more difficult since you haven't had to deal with the loss of near vision in presbyopia to at least have some clue what you are in for to keep the issues in perspective.    Elderly folks with full presbyopia have had years to adapt to the slow loss of near and its not much of a change for them to lose their near and deal with multiple pairs of glasses or progressives/varifocals or whatever since they've adapted to it. Even those with early presbyopia have at last gotten used to the idea their near is going away, though in my case that led me to try to fight the issue off with multifocal contacts, and then a premium IOL. I was 49 when the cataract was diagnosed, old enough to have to deal with presbyopia, but not old enough to have become resigned to it.  Part of it is a matter of convenience, but that adds up over decades.

I disliked the way progressives/varifocals narrowed the field of view that was in good focus, unlike multifocal contacts, and unlike the Symfony IOLs I have, and I also figure safety wise its useful to have a wider range of view .There are some studies showing a reaction time difference between those wearing glasses and those wearing contacts or not needing correction).

re: "once I put my contacts on pre cataracts"

I would suggest again then considering trying multifocal contacts when they are ready to prescribe correction. There are off the shelf contacts for low powers that are likely more comfortable and convenient than you needed for high myopia preop. (I know when the cataract shifted my problem eye to be highly myopic and the usual brands didn't work, the brand that didn't wasn't as comfortable, actually I got  GPC bumps from  irritation from it).

Some people aren't as satisfied with high adds, which unfortunately are more useful with a monofocal IOL. Some people first using multifocal contacts start with lower adds to adapt and then increase the add, though even a low add might provide some utility. Different brands have different optical designs so if the first doesn't work well the others might. It isn't clear if you'd want to try  multifocal contacts set to  even out your monovision, or added on top of it to provide a wide range of vision for each eye. 

 

Alternative with glasses you can get bifocal or trifocals, including ones without prescription in the top part, or no-line progressive glasses (called varifocals some places). 

They do make sunglasses with reading segments (even for sports I recall seeing Tifosi, and perhaps others, having sunglasses with a litte area for  reading), or there are actually seperately sold stick-on little reading lenses you can attach to existing non-prescription glasses. I think there are also clip-ons that'd work over sunglasses.

re: "I expect someone who is already presbyopic wouldn't find it as disconcerting, as they've had a gradual reduction in near vision over time to get used to."

Yup, though of course there are degrees of presbyopia. Some early presbyopes like myself hadn't fully lost all our near before cataracts and knew enough to dislike the idea of losing the rest. Some with multifocal contacts are able to not worry about presbyopia usually, which is why I went for a premium IOL to continue that.

 

 

re: "shifted my problem eye to be highly myopic and the usual brands didn't work, the brand that didn't wasn't as comfortable, "

oops, of course I meant the brand that did work wasn't as comfortable. I should have said when the cataract   shifted my eye from highly myopic, -9.5D or so, to extremely myopic, -19D or so (glasses prescription, I forget the contact prescription numbers which were less)