Mixed Monofocal lens for Cataract Surgery
Posted , 5 users are following.
I am trying to understand what my vision will be like with my second cararact surgery.
I had distance monofocal done last january. My surgeon want to put near vision of-2.5
in my right eye this January. She said it will be similar to what I can see now.
My understanding is that one eye will see distance and the other near. Does anyone
have that mix of monofocal and are there any problems.
0 likes, 15 replies
RonAKA joan40698
Posted
Yes I have a monofocal set for distance (0.00 sphere) in my right eye, and another monofocal set for closer vision in my left eye (-1.40 D). I think it is a good idea and I am 95% free of eyeglasses. A week or more will go by without me needing glasses for distance, driving, watching TV, using the computer or reading my iPhone. The only concern I would have with your surgeon's plan is to target -2.50 D in the close eye. While that is a standard amount used as an Add in progressives or bifocals, it is quite a large differential between the two eyes. Most people are going to have trouble adapting to it. It also may leave a "hole" in the intermediate vision range around 18-24" where vision is not that good. My suggestion would be to ask for a target of -1.50 D in the close eye. You will not be able to see very small print especially in dimmer light, but like I say those situations are fairly rare. For those needs I have a pair of +1.25 D readers which I wear occasionally.
indygeo joan40698
Posted
As RonAKA wrote, 2.50 diopter difference is quite large. If you're going with another monofocal lens you'll want to go between 1.25 and 1.50 difference. If using an EDOF lens like a Rayner EMV for example, you could go - 0.75 and likely be well off.
Indy G
joan40698
Edited
Thank you very much for your input. I will contact my surgeon to discuss targeting my eye for -1.5.
I was having such a difficult time getting information regarding what -2.25 meant. When I messaged
her she said that she was targeting it for near and I would be able to see my i phone and there would be less dependence on glasses for reading . It would be similar to what I can see now without the cataract of course. Is there such a big difference between -1.5 and-2.25?
indygeo joan40698
Posted
Yes, a rather huge difference. Whereas maybe 5% of people might be able to tolerate a 2.25 diopter difference between eyes, perhaps 95% will find 1.50 diopter difference tolerable. You really do want to err to the lesser difference in my opinion. Test this out with contact lenses if you can.
Indy G
RonAKA joan40698
Edited
For sure for reading -2.25 will be better. That is why the "Add" you see on an eyeglass prescription for progressives or bifocals is usually +2.5 D. But with monovision you have to compromise a bit on the power for reading so you can tolerate it when looking in the distance. I have the equivalent of -1.40 D in my near eye and I can see down to about 12". But, I do use some +1.25 D readers for very small print in dimmer light - which is very occasionally.
RonAKA joan40698
Edited
As I recall I replied in another thread you can easily simulate what -1.5 D and -2.25 D will look like by using some cheap dollar store readers of +1.5 D and +2.25 D respectively. Look through your IOL operated eye only. That will be a close simulation of what -1.5 and -2.25 D will look like when it is being achieved with an IOL. You want the minimum power necessary to give you the reading ability you want. For most -1.5 D will do the trick. Some may get away with -1.25 D.
joan40698
Posted
Thank you so much for all the information. I spoke to my doctor today and she said that my right eye
now is -2.8 and I have been tolerating that for almost a year. I still use reading glasses for small
print and reading my kindle. I have no problem reading my computer without glasses as well
as walking and doing other activities as well as driving. She thought making it -2.00 might be a
good comprise. She did say if I wanted she would aim it for intermediate -1.5. I thought since I
am happy with the way I can see now that the -2.00 might be the better way to go.
RonAKA joan40698
Posted
If you are -2.8 D now and are tolerating it then -2.25 or -2.00 D is not going to be a shock to you and your vision. What can happen with that much differential between the eyes is that an intermediate distance can be left with weaker vision. You can also lose the 3D depth perception in that range and in closer. Perhaps that is the reason your need glasses to read your Kindle. The distance of it may be falling into that weak zone. I will see if I can post a graph that shows this effect. It will take a while to be moderated.
RonAKA joan40698
Edited
Here is a graph that shows combined visual acuity for -1.0 D, -1.5 D, and -2.0 D monovision. Notice the dip in the -2.0 D acuity line at the 0.7 to 0.8 meter distance.
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And here is a graph which shows the difference in Stereoacuity of the three degrees of monovision. This is a measure of your ability to see 3D and judge distance. A lower number is better. There is a small loss going from -1.0 D to -1.5 D, but a much larger loss going to -2.0 D.
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This said if you can tolerate a differential of 2.8 then the differences between these choices may seem minor to you and not worth worrying about.
indygeo joan40698
Edited
Joan, I think this could be a case of not knowing what you're missing and thinking what you've got now is good. In my case, 4 years ago I had a monofocal implanted in my left (distance) eye. My right (near) eye had mild cataracts and was naturally nearsighted. The difference between the eyes was a tad over 2.0 diopters. Although I found this somewhat tolerable (I mean, just that I was able to see out of my left eye was a huge win), I did wonder if I'd be better off with a smaller difference. I did struggle with an intermediate zone as pointed out in RonAKA's graphs. So when my right (near) eye cataract progressed to the point I was basically blind, I opted to go with the science and math of it and aim for a smaller difference. Ultimately, I chose an EDOF lens (the Rayner EMV) and offset it 0.75 D from my distance lens. Because of the extended depth of focus of the Rayner lens, I got an extra diopter or so of additional near vision. So it's kind of having your cake and eating it too. The difference is small plus I've gained excellent reading vision from about 11 inches out. I highly recommend you checking out articles and YouTube videos featuring famed ophthalmologist Graham Barrett and monovision.
Indy G
RonAKA indygeo
Edited
I believe Barrett advocates mini-monovision of -1.25. I suspect that may be true if you have no astigmatism and can actually get a -1.25 outcome. That is a pretty small needle to thread though.
indygeo RonAKA
Posted
Hi Ron,
I suppose Barrett's 1.25 offset is a small needle.. with a straight monofocal lens, but my understanding is the Rayner lens is quite forgiving in terms of a landing zone. A surgeon can target a -1.0D offset and wind up quite good even if he/she was off by 1/2 D either side because the defocus is not very steep. Since my "distance" eye was already set satisfactorily my surgeon said I was essentially low hanging fruit (with the Rayner lens at least) because he felt confident in hitting a monovision I'd be happy with, all things considered. By the way my near eye apparently has 1.0 D of astigmatism which I think is borderline in terms of having to do anything about it. It doesn't seem to affect me though.
Indy G
RonAKA indygeo
Edited
You pay a price of course for extended depth of focus in a lens in visual acuity. B+L present an interesting graph shown below. They use it to promote their enVista spherical aberration neutral IOL. In this graph they illustrate how increasing the depth of focus decreases visual acuity. They of course argue that their enVista uses the optimal amount of SA. They identify the common Tecnis 1 lens at 0 SA, and the Alcon AcrySof IQ at 0.1 SA, on the graph. Not sure where the Eyhance and Rayner lens would fit on this graph but it must be out somewhere in the range of the enVista. And, the Vivity perhaps beyond that. Alcon make the argument that SA should not be reduced to zero, base on a study of people that have super vision. They claim an SA of 0.1 is ideal... Not sure where an old fashioned plain spherical IOL would fit on this graph but I suspect it is to the right of the neutral position...
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indygeo RonAKA
Posted
Hi Ron,
Yes I agree theoretically there would be some visual acuity loss, but I think it's virtually undetectable, if detectable at all, in a real world setting. I can only speak from my experience with the Rayner lens in that I definitely have a "wow" factor every day since having it. I can resolve the tiniest of print at reading distance in normal light. It's like I'm going "into" the letters when I'm reading. It definitely has a "brighter" character to it than my older monofocal lens (maybe because it's new, I don't know).
For what it's worth, here are some early experiences.. and this was with targeting plano (i. e. Not monovision) :
--Patient Satisfaction
In the one-month postoperative period, patients reported high satisfaction with their refractive outcome, with 70% reporting spectacle independence at distance, intermediate and near. Patients
were entirely dysphotopsia-free; 100% reported no incidence of halo,
glare, starbursts or haze one month postoperatively (n=18). 100% of patients reported no difficulty negotiating steps, stairs or curbs with no depth perception or contrast sensitivity issues reported.--
70% spectacle independence even at near is quite impressive, given plano targeting. This is why even a minimal offset like -0.50 to -1.00 will likely yield excellent results in a monovision scenario.
My surgeon is rather high profile and this is his "go to lens" these days. He's abandoned Eyhance.
Regards,
Indy G
RonAKA indygeo
Edited
The claims made for the enVista are similar. They say the lens is more tolerant to less than perfect power accuracy, and also it is more tolerant to lens decentralization. It may be better for the less than perfect eyes. My brother just got an enVista lens about 18 days ago. Last I heard he was up to 20/25 vision. Will be interesting to see what he gets when the eye is fully healed.
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I found this article on Spherical Aberration which explains a lot. From what I read in it, an old fashioned low tech spherical lens without SA correction comes in at about +0.37, so a little further off to the right of the enVista with more depth of focus and slightly less visual acuity. I find it interesting that at the end of the day the old technology may be a better all around solution than these newer SA correcting lenses, like the Tecnis 1 which in theory bring SA down to zero.
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Eyeworld Understanding spherical aberration International January 2018 by Claudio Orlich, MD