Monofocal issues?
Posted , 7 users are following.
Has anyone gotten monofocals and had vision issues other than needing readers? Is this really the lens with the least amount of potential issues? thank you
0 likes, 17 replies
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Notes on Monofocal issues?
RonAKA aspen88
Edited
Yes, I would say that the monofocal lens has the lowest risk of optical side effects. They are not zero risk however. They will be free from the optical side effects that are the result of the bifocal, trifocal, and EDOF tricks put into those types of lenses. But they will not be zero risk free from issues that could impact any lens. Some possible ones are:
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So, like I say, monofocals have lower risk but are not zero risk. The J&J Tecnis 1, Alcon Clareon, and B+L enVista are three good lenses and with a good surgeon who takes care with the measurements and calculation of the required power should give you the lowest risk outcome. At an extra premium in cost and time/travel for the extra appointments, the LAL lenses can reduce the risk of refractive surprise.
RonAKA aspen88
Edited
The first response I gave assumes use of monofocals with the targets for both eyes set the same, usually distance, but sometimes for near or intermediate. If you do monovision with one eye set for near and the other for distance there are some additional risks which can be minimized with planning. Some will not adapt to the differential between the eyes. This used to be a more common issue when ophthalmologists tried to correct the near eye to give perfect very near vision by targeting -2.5 D to -3.0 D, while targeting for distance typically in the dominant eye - i.e. full monovision. The more common approach now with mini-monovision is to target just enough myopia to do the common tasks such as computer work, read books, and read the iPhone etc. For most that requires -1.50 D. With the distance eye targeted to -0.25 D or very slight myopia this minimizes the differential between the eyes, and minimizes the risk. It also eliminates the "hole" created at intermediate distances which will occur with full monovision.
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The next way to reduce risk with mini-monovision is to simulate it first with contact lenses. If you like the effect with contact lenses you are very likely to be happy with IOL mini-monovision.
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A typical plan to reduce risk is to do the distance eye first and let the eye fully heal (6 weeks) before you make the decision on the second eye. You can use the break between eyes to use a contact in the non operated eye to simulate mini-monovision and to confirm that is what you want to do. And if there is a bad miss by the surgeon to the myopic side you could also consider switching which eye is to be the near eye. And if you decide you do not like mini-monovision you still have the common option of doing both eyes for distance. And if the first eye is a little off for distance the surgeon gets a second chance to nail the second eye.
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And last with a monofocal lens there is always a plan B if things do not turn out as expected. A monofocal lens surprise can always be corrected with eyeglasses. However with EDOF lenses which stretch the focal point, or bifocal/trifocal lenseswhich provide multiple focal points, you cannot undo that effect with eyeglass lenses. You are stuck with it short of a complete lens explant. And with mini-monovision I think it is always worthwhile to plan on getting progressive eyeglasses to fully correct both eyes for difficult situations like night driving. I have a pair, and that is about the only time I would use them, and only when driving in the country with no street lights.
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So there are some additional risks, but they can be mitigated with careful planning.
aspen88 RonAKA
Posted
thank you for the detailed explanation, RonAKA. Do you think there is much difference in the Technis vs Acrysoft vs Clareon? is the measurement accuracy determined by the technician not the surgeon in which way there is no way of knowing?
RonAKA aspen88
Edited
There are a couple of differences between the lenses that I can think of. One is asphericity. The average cornea has +0.27 um of asphericity. In theory the best visual acuity is obtained when asphericity is reduced to zero. The Tecnis lens has -0.27 um to achieve that. Alcon believe better vision is obtained by leaving some positive asphericity so they build in -0.20 um which leave you with +.07 um. B+L believes more positive asphericity makes the lens more tolerant and increases the depth of focus. The put zero in the lens which leaves you at +0.27 um. See this article for an explanation.
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CRST The Science Behind the AcrySof IQ IOL Mutlu Karakelle, PhD
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The other way the J&J and Alcon lenses differ is that J&J typically use clear lenses with no blue light filtering, only UV. Alcon believe the lens should deliver a colour balance similar to a young adult and they put blue light filtering in to achieve that. The result is that the Alcon lens will deliver a natural colour balance while the J&J will increase the blue from the natural position.
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The Clareon and AcrySof IQ lenses are very similar except the Clareon is made from an improved material, and has sharper edges to provide more resistance against PCO.
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Yes, the technician takes the measurements, but there can be a difference in instruments used. The IOLMaster 700 takes about 1/3 the time to scan the eye, compared to the Lenstar 900. This makes it easier for you to hold still for the whole duration and get good readings. The technician has to be patient and keep taking the readings until they get good ones.
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The skill of the surgeon comes in when the readings are converted to a lens power. They need to select the right formula to use and the correct target. Some surgeons apply a personal correction factor on top of the computer result. Ideally they will use more than one formula and make the final decision based on experience.
aspen88 RonAKA
Posted
thank you for sharing your knowledge! i am amazed how much you know about this stuff!
aspen88 RonAKA
Posted
someone mentioned before to take several measurements to make sure it is correct. how do i read the measurements and what do i exactly look for? i have a copy of my initial evaluation.
RonAKA aspen88
Posted
If it was an IOLMaster Calculation sheet then google this for some help as to what it means.
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Zeiss IOLMaster 700 Quick Guide Printing Functions EN PDF
aspen88 RonAKA
Posted
i guess the surgeon's office don't provide this information and it will be beyond my capability to compare. but thanks for the info!
RonAKA aspen88
Posted
What is most important is that the surgeon shows you what the lens power choices are for your eye, and what the predicted spherical equivalent (SE) will be for each power choice. They are not going to be exact numbers in 0.25 D steps. There is likely to be one above your desired power and one lower. You should be involved in making the decision as to which one. For example if your objective is excellent distance vision you may have a choice of a SE of +0.10 D, or -0.30 D. While the power choice that gives +0.10 D is closer to your target than the other one, it is much more risky. When you go positive that means far sighted, and the more positive you go, the more near vision you lose. If I had those choices, and I actually did, I would go for the -0.30 D outcome. Being slightly myopic is the safer choice.
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As far as measurement accuracy goes and how many times should they be measure, that is kind of out of your hands. You need to go to a clinic with experienced staff and have the latest technology equipment. I would suggest that if you can find a clinic that has the IOLMaster 700 and Pentacam for topography, then you are off to a good start. There is another fairly common instrument used called the Lenstar 900. It is very accurate also, but it takes about 3 times as long to do the scan compared to the IOLMaster 700. It is much harder to stare without moving your head or eye for the longer time. The IOLMaster makes it easier to get a good reading. I went to a clinic for a Lasik evaluation and they had a terrible time trying to get good readings on my eyes. Not sure if it was the staff or the instrument, but I suspect it was a little of both. Before they "said" they had good readings they had made several attempts with 3 different staff members. It does not inspire confidence in the outcome. I went to another clinic and there was no problem at all.
Lynda111 RonAKA
Edited
The skill of the technician measuring your eye is very important. Some are better than others. I would look for one who is a Certified Ocular Technician. Not all are.
Also, if you have deep eye orbits or if you have ptosis (eyelids that are not above the pupil) it can make accurate measurements more difficult. It helps to use lubricating eye drops like( Systane Hydration preservative free) to make the reading more accurate. I had my eyes measured by technicians at the offices of three different cataract surgeons. Only one got my measurements without difficulty. She used the Pentacam. The other two technicians kept saying it saying they were having "problems" with my measurements.
Lynda111 RonAKA
Edited
As Ron said, "You should be involved in making the decision about your lens power."
That is the ideal. Most of the time, the cataract surgeon will just suggest near or distant vision. If you want to get technical about it, you will have to be insist on it and be knowledgeable yourself. The majority of patients aren't inclined to do that, and most still have pretty good outcomes. But some patients want to dive into optics, and that's great, but you want a surgeon and a technician who will cooperate with you.
aspen88 RonAKA
Posted
what did your eyes end up being? how long did you test monovision?
RonAKA aspen88
Edited
Based on the latest eye exam on a spherical equivalent basis I am -0.4 D in the distance eye, and -1.6 D in the near eye.
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I tested monovision with contacts many years ago and liked it, but didn't like the contacts so went back to glasses. Then prior to surgery on the first eye I tested with contacts for a short while. But after surgery I almost exclusively wore a contact in my non operated eye to simulate near vision. That went on for 18 months or so before the second eye was done. I found much better contacts to use, so it was quite tolerable.
RebDovid aspen88
Edited
According "What intraocular lens would ophthalmologists choose for themselves", a 2019 article in Eye, published by The Royal College of Ophthalmologists, the authors analyzed 328 survey responses received from senior ophthalmology residents and practicing ophthalmologists. " In the setting of no astigmatism, 61.3% of respondents would choose a monofocal IOL set for either distance or monovision for their own surgery. For corneal astigmatism >1.25 D, 60.3% of respondents would choose a toric monofocal lens and only 6.9% would want a femtosecond laser or manual LRI for their
own surgery. Of the respondents, 34.6% perform femtosecond laser-assisted cataract surgery, but only 15.3% would want femtosecond cataract surgery performed on themselves. Also, 67.7% implant presbyopia-correcting IOLs (diffractive echelette, multifocal, or accommodative). When correcting for patients’ corneal astigmatism >1.25 D, 65.7% of respondents preferred a toric monofocal IOL."
aspen88 RebDovid
Posted
thanks, RebDovid. that is very interesting that most of them would choose monofocals themselves. i wonder what their rationale is but seems that if they choose it, it is still the "best" choice overall.
lucy24197 RebDovid
Edited
If you want it from the horse's mouth, look for "limitations with the Vivity IOL." There's a video by one of the top US cataract surgeons, and about 12:18 in he talks about the lenses he would choose and what other opthalmologists he's done surgery on have chosen--monofocal lenses in order to get the best image quality.
As far as issues, I had negative dysphotopsia at first--it's largely gone away. Someone asked about it the other day so I've been looking for it and now see it again on occasion, but it's not a big deal and I wasn't seeing it at all until I looked for it. Kind of like when you're wearing glasses and catch the frame out of the corner of your eye.
I have Tecnis monofocals. I've heard a lot of people say that things looked blue after surgery in general after cataract surgery; I've never experienced that. Things just look clean now. When I put on my readers with a blue light filter, they put a dingy yellow cast on things IMO. (Part of that may be that they're REALLY cheap readers.) As far as needing readers goes, I have my near eye at -1.75D. I can get through the day without glasses, but for serious reading (or reading where I'm holding something close, like reading in bed, or really fine print with low contrast) i use readers. I would not be functional without glasses with -1.5D as a target. If your near vision is more important to you than distance, I'd think hard about -1.5D as a target. If you have some glasses that correct your vision to plano, get some cheap -1.5 readers and stack them to see if -1.5 will give you enough near vision.
RonAKA lucy24197
Posted
Keep in mind that of the monofocals available the Tecnis 1 has the lowest amount of depth of focus because they use a -0.27 um aspheric correction to bring asphericity to as close as possible to zero. The AcrySof IQ and Clareon do not fully correct asphericity with a -0.20 um correction, and have a bit better depth of focus. The enVista is a neutral asphericity lens that makes zero correction to leave you at +0.27 asphericity, and has the largest depth of focus of these choices.
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Near vision varies from person to person, and those who are older and have lower smaller pupils tend to see closer.