Deciding the power of monofocal lens for Cataract

Thanks so much lucy24197, this sure helps. How about the eye with your distance set to -0.5D, can you see car dashboard/gps with that or can you see what you are cooking with that ?

I can see my car dashboard well enough. I have an ancient vehicle with analog high contrast gauges and no GPS, so I don't know how a modern electronic dash would compare (it certainly wouldn't be as fun to drive.) As far as cooking goes--it depends on the type of cooking you do. If you're just dumping a can into a pot and want to see if it's sticking while you heat it, it would probably be fine. If you're the type that uses garlic powder, might be ok. If, like me, you peel fresh garlic and cut any questionable bits off the cloves with a very sharp knife, and then use that very sharp knife to mince the garlic into oblivion, I would be very unhappy with the -0.5 and no glasses. I need to really see well when it comes to preparing food.

Thanks rwbil all good suggestions I will keep those in mind for sure.

Such a detailed reply RonAKA. I am grateful to you. I was thinking of mini-mono vision as well with one eye -1.25 and other eye -0.25 . That is what I am going discuss with my doctor on the next visit when I am going for the measurements. The question really is what is the closest distance where I will be able to read without reading glasses with this kind of vision. According to lucy24197, it may be 27" (more than 2 feet).

According to the defocus curve from a recent clinical study of 45 Tecnis 1 implants, your monocular visual acuity (VA) at 40 cm (=2.5D) in the -1.25D eye should/could be about 0.25 logmar (better that 0.3lm = 20/40), and that in the -0.25D eye sh/could be about 0.5 logmar. You should have decent reading vision for a 6" in smartphone screen at that distance from the near eye. Not sure how the binocular vision may work out (as the far eye would have a blurred image at 0.5lm); not sure if you'd be able to make your brain to show you only the good image. I'll try to post the defocus image, but I'm unsure it will come through.

I think there is variability between individuals as to how close you can see with a monofocal IOL. My AcrySof IQ Aspheric monofocal in my right eye left me with 20/20+ distance vision, and a residual prescription of 0.00 Sphere, -0.75 D Cylinder. I can read a computer screen with difficulty down to 18-20 inches, and under that not so much. I can easily see the dash in my truck, car, and instruments on my motorcycle with this eye. I am simulating -1.25 D in my non operated eye and I can see dash instruments better with my distance IOL than I can with the -1.25 D eye.

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I find the Jaeger eye chart for reading helpful in determining what my vision is. You can find a copy to print out at the All About Vision site. With my simulated -1.25 eye I can see the smallest J1 text fairly easily. When I correct my distance vision IOL eye with some +1.25 readers I can read the J1 text as well, but I have to hold the page a bit further away. It is not quite as easy. It seems I may be getting a little more than -1.25 with my simulated vision eye. It is still the natural lens so there may be some remaining accommodation even though I am 72. In any case I am going to get some dollar store +1.5 D readers to see how that works with my IOL eye. Working with this eye may be the better way to simulate what I will get when it comes time to do my second eye for closer vision. This is why it is best to do the distance dominant eye first and then use the time between eyes to evaluate monovision with contacts, and also with readers on your new IOL eye.

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IOL powers come in steps of 0.5 D, which does not allow the precision that 0.25 D steps in eyeglasses or contacts give you. Each eye will be an individual decision. You should ask your surgeon after your eye is measured what the closest lens options will give you. For example in the distance eye one power might give you a residual of +0.25, and then next power available -0.25. You really want the -0.25 option. As my surgeon told me, "Nobody ever thanks me for making them far sighted". It may not be that clear cut though and you should have that discussion. On the near eye, if you go that way, it is probably best to target a range of -1.25 to -1.50 D. There will be a decision required there too on the best available of the 0.5 D power steps. I would expect with your eyes you will be looking at an IOL power of around 12.5 D for the distance eye and about 14.0 D for the closer eye. They use a different range of powers than an eyeglass lens.

The important thing to note in that graph is the error bars on the Tecnis 1 data points. Those that got the best vision in the study were essentially the same as the Eyhance people (average I assume). This shows the variability from person to person of the outcomes of an IOL.

I agree, but that applies to just about every defocus curve out there, as it's clinically generated and hence a zillion unknowns & random variables come into play. So taking the mean with the caveat of "errors may apply" is the best we can do.

BTW, looking closer at the VA curves (of IQ, Vivity, Tecnis1 & Eyhance) side-by-side, I'm beginning to be convinced that the following blended monovision config may work very well (in your case & others'):

• IQ set for Plano in the Dominant eye
• Eyhance set to -1.0D offset/refraction in the non-dominant eye (NDE)

I call this the IQHance Vision Renewal Solution (on budget and with no halos)!

It should give (in the average case where the above targets are well met)

• better than 20/20 for distance
• better than 20/30 for near
• no significant loss of stereo-acuity for distance/driving vision
• (likely) no significant dysphotopsias

I'll post some images soon (and/or send you over PM) along with my reasoning based on them. Perhaps you may want to consider it?

And, excellent intermediate vision, I'd add. The config should give better than 20/25 VA (i.e. => 0.1 logmar) over the entire 0-2D range (i.e. ∞ down to 50 cm) (again, in "average eyes" cases).

I have already plotted the IQ and Vivity defocus curves and contrast sensitivity myself with various offsets using data from the Vivity package inserts on a spreadsheet graph. I think combining the Vivity and IQ gives an improved contrast sensitivity outcome, and two IQ lenses actually a little better still. For defocus the Vivitiy at -0.75 D and IQ is pretty good for close vision, and about the same as IQ at -1.25 and the other at plano. The advantage of the Vivity at -0.75 and IQ plano is in the distance vision. The Vivity -0.75 D retains better distance vision than the IQ at -1.25.

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There used to be a good PDF article on monovision which showed the tradeoffs. The full article seems to have been taken down, but the basic summary information and the graphs are still there. They concluded that -1.5 D offset was ideal. I concluded that -1.25 which they did not specifically plot may be even better. But with testing of my IOL eye, I am now tending to agree with them and a -1.5 D offset may be ideal.

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Optimal amount of anisometropia for pseudophakic monovision K. Hayashi, Motoaki Yoshida, +1 author H. Hayashi Published 1 May 2011 Medicine Journal of refractive surgery

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Here is another good article, where they talk about hybrid monovision when a lens like the Vivity is used in the non dominant closer eye.

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Monovision Strategies: Our Experience and Approach on

Pseudophakic Monovision Misae Ito CO* and Kimiya Shimizu

Department of Ophthalmology, Sanno Hospital, Japan

I agree a -1.0 D offset is probably about ideal for the Eyhance, and -0.75 D for the Vivity. And for a monofocal solution -1.25 to -1.50 D.

There are a lot of issues with predicting what near vision will be. One of the most difficult is that "decent reading vision" can be defined differently from person to person. One person might think that being able to identify words is "decent", another may feel that they need to read easily and at normal speed for vision to be "decent." When I use some old glasses to adjust my eye to -1.25D, I can make out a 6.5" smartphone screen at 40 cm (just under 16"), but I wouldn't find it to be acceptable for general use. I could dial the phone just fine, I wouldn't want to read important emails or texts with my vision like that--I can make out the words but would be prone to errors. I don't get sharp vision at -1.25D unless the phone is held out at basically arm's length--about 25" for me. It would be nice if defocus curves were standardized, with statistically significant sample sizes, but for now they're probably about the best information the layperson has for predicting visual acuity. And one must take into consideration they are only averages and everyone's eyes are different. The best you can do is really think about what range of vision is most important to you to be glasses free, decide how much you are willing to risk getting that glasses free range vs getting a larger range of vision, get as educated as you can, hope for the best & plan for the worst.

**no significant loss of stereo-acuity for distance/driving vision

My only advice is try and test this first with contacts if possible. I just had cataract surgery and my vision slowly improved over several days and I can tell you for me the difference in the image the eyes presented the day after surgery did make a difference. With time it might smooth out, but again if at all possible test it out as everyone is different.

Even now for close vision, my 2 eyes are close in vision and bilaterally my close vision is better than either eye is individually.

If you look closely at the defocus curve that you've posted, the average best distance vision was less that 20/20. Other defocus curves, other studies, other groups of people come out better. It's terribly frustrating when you're trying to make a lens selection. As far as dysphotopsias, I have negative dys. in both eyes with the Tecnis monofocal. It's not terribly bothersome--much like seeing the rims on a pair of glasses, but it's there. (The only time it gets a little freaky is when I close my eyes with light shining in my face and I see the dark rims. My brain is used to "glasses frames" when my eyes are open, but when they're there when my eyes are closed it feels really strange.) I am also having some glare/halo issues, but they may be due to some complications from the surgery and I am hoping they'll resolve. A monofocal/eyhance combination would probably work very well for individuals with healthy eyes. Just trying to say that everyone has different results; there are no absolute best choices. It's a very personal decision, and unfortunately most doctors do not take the time to work with patients to determine the best approach to make a patient happy.

For sure we seem to get different outcomes. On my iPhone 8+ which seems to have about a 6" diagonal screen I can fairly easily read the Apple stocks screen with +1.25 readers using my 0.0 D IOL distance eye. Much more green today than the red on Friday! Reading white numbers on a green background is the hardest, but I can see them fairly easily at about 14". They are somewhat easier to read at 12" with -1.5 D readers. And if I stretch my arm out to full length and take my time I can read it with my 0.0 D eye with no help from readers. It is not comfortable though. With the Jaeger chart I can read the J1 with bright cloudy daylight with both 1.25 and 1.5 D readers. I can hold it a bit closer and read easier with the +1.5 readers. At least for me, this seems to confirm a good monofocal target is -1.25 to -1.5 D. My left and right eyes are reasonably similar and I would expect similar results for each...

Would this Eyhance configuration work in a high myope (-10.50 in contacts)?

hi lucy....i see that you posted this 19 months ago. are you still having negative dys and glare/halo issues? i thought this was not supposed to be an issue with monofocals which is why I was leaning towards this conservative approach....thanks

I was having no glare or halos, and very, very rarely see the negative dysphotopsia. When I do see it, it's not very noticeable unless I'm trying to see it. About a month ago I had a YAG capsulotomy done on my distance eye, and now see some halo/starbursts when I look directly into a bright light, like a bright LED flood light. Lights were very clean and sharp before YAG.

thank you

Hi RonAKA,

My cataract surgeon has suggested -1.75 D but I am confused as how that can be a choice since IOL powers come in steps of 0.5. In other words, how can there be gradients of -2.0 D, -1.75 D and -1.5 D? I am obviously missing something important here... Could you clarify? Many thanks.

There are two things to understand about this issue which can be confusing.

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1. The lenses do come in power steps of 0.5 D with most of the common lenses. However that is measured at the lens position in the eye. At the cornea plane which is the more common measurement method used for contacts and glasses, each step represents about 0.38 D. So the outcome impact of a step change is that amount not 0.5 D.
2. The other factor is that a target is just a target, not an outcome. When they measure your eye and process the measurements in the IOL power calculation program the surgeon can enter a target of plano, or some other target. I recall those targets are in 0.25 D steps. However because the target is set at -1.75 D you will not likely get that outcome. What the computer program does is consider that target along with your eye measurements and then predict what each IOL power option in that range will give you as a predicted outcome. It is unlikely one will be exactly -1.75 D, but there will be one just above that, and one just below that with a difference of about 0.38 D between them. You and your surgeon should consider which one is most appropriate for you given your priorities for vision. This is why it is important that the surgeon show you the IOL Calculation sheet because it will include what "target" is chosen, and then toward the bottom it will display several IOL power choices and what the predicted outcome of each is. It is just one click of the mouse for them to printout the IOL Calculation sheet and it is worthwhile asking for it.

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   Hope that helps some

A third factor is that eyes don't come in half -diopter steps. Your eye might need a +18.7 d IOL to reach emmetropia, for example, and another person's eye might need +14.316.

Each person faces a limited menu of targets and the menu is different for each patient. Something in the vicinity of -1.75 under correction is apparently on the menu for you, which means -2.0 is not. For another patient getting the same model IOL -2.0 might be on their menu and-1.75 not, because they have a different lens power needed for emmetropia -- call that a starting point -- and those starting points are distributed continuously by mother nature, not in discrete jumps of 0.5 diopters.

I think you misread what I have said. The reality is that when you combine the measurements of your eye with the available powers of IOLs, you have range of options to choose from. You will only know what the choices are if you look at the IOL Calculation sheet. Yes, you cannot get a perfect lens for your eyes, but you can pick the best of what is available.