toric monofocal or plain monofocal
Posted , 7 users are following.
I have astigmatism in both eyes and was wondering about the advantages and disadvantages of choosing a toric distance monofocal over a plain distance monofocal.
Specifically I have read that torics can shift and cause problems. Can a shifted toric be re-aligned?
Wearing astigmatism correcting distance glasses with a plain monofocal would be inconvenient because I prefer not wearing glasses all the time. Would I get the blurred double vision associated with astigmatism if I do that? Also I believe my near vision with a plain monofocal would cause dizzyness.
If anyone with astigmatism has experience with plain distance monofocals please let me know the problems I'd face. I have surgery within a week or so and any help would be appreciated.
Also how do I simulate the extent of blurriness(loss of focus) of near and intermediate? Does it vary depending on how myopic your current cataract eye is or is it the same extent of loss of focus independent of the extent of myopia ?
0 likes, 11 replies
RonAKA kdf123
Edited
The first question I have is whether or not you have had your eyes measured for IOL cataract surgery? That is the only way to know how much astigmatism you will have post surgery if you do not use a toric lens. Normally if the predicted residual astigmatism (cylinder) is more than 0.75 D then it is worth it to get a toric lens, but only if eyeglasses free vision is a priority. Eyeglasses will easily correct astigmatism. Unless you have irregular astigmatism eyeglasses or a toric IOL should correct astigmatism
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Toric lenses can shift, but it usually happens right away. That is the reason for having an eye exam 24 hours after cataract surgery. They need to check the position and adjust it if necessary. For what it is worth Alcon AcrySof and Clareon IOLs have a reputation for being more stable in the eye, and not rotating out of position.
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If both eyes are targeted for distance, then near vision will not be clear. It will be similar to an older person that has presbyopia. It should not make you dizzy, but just make you look for your reading glasses.
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I have a monofocal in both eyes and have a residual astigmatism of -0.75 D in both eyes. In retrospect I wish I would have gotten a toric in my near eye. I have one eye set for distance, and the other set for near.
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Your near vision will primarily be determined by your refraction after surgery. Most surgeons will target to leave you with -0.25 D of myopia when you want distance vision. This is because if they go into the plus side or hyperopia both near and distance vision will be reduced.
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Those wanting mini-monovision typically will do the distance eye first, and then wait until it settles down after surgery, and a vision refraction done at 6 weeks, and then make the decision on whether or not to target the same for the other eye, or target for more near vision in the second eye.
JN9008 RonAKA
Posted
Agree with you that if the residual astig post surgery is < -1, then perhaps it's not necessary to have Toric. There are some points that are interesting in your reply/comment. You said your residual in both eyes is -0.75D. what was it before surgery? You also mentioned "Most surgeons will target -0.25D of myopia when setting IOL to distance." so as to avoid going to the + side (hyperopia). My question is: there's still no guarantee not to go over to the plus side (slightly hyperopic) right? So maybe it's even safer to target say -0.5 or -0.75 to minimize the chance of going over?
RonAKA JN9008
Posted
I am at -0.75 D cylinder in both eyes after surgery with non toric monofocals. I was more like -1.50 D cylinder before surgery.
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The best IOL formulas like the Hill-RBF 3.0 are up in the 90% within +/- 0.5 D, so there is some risk of ending up at +0.25 D. But, that is not the end of the world - probably 20/20 still. Yes, you can target -0.50 or -0.75 D, but that is putting 20/20 distance vision at risk.
mart27056 RonAKA
Posted
Ron - Is this change in astigmatism pre and pro surgery typical. That is, does cataract surgery generally reduce astimatism to some degree?
RonAKA mart27056
Posted
Pre cataract surgery your eyeglass tests measure the total of the astigmatism in the cornea plus the astigmatism in the lens. Astigmatism has an angle (axis) as well as a magnitude. For that reason the addition is on a vector basis. If the angle of the lens astigmatism is the same as the cornea astigmatism the total is the simple sum of the magnitude (cylinder diopters). However if the angle is opposite the astigmatism in the lens can cancel out the astigmatism in the cornea.
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For this reason you can't accurately predict post surgery astigmatism simply based on your pre surgery eyeglass prescription. What you really need to know is how much astigmatism is in the cornea only. That is what will remain after surgery, as the astigmatism in the lens is gone as the whole lens is removed. Post surgery astigmatism is done with special instruments that measure the slope of the cornea around the complete axis of the eye.
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I think in general astigmatism does go down after cataract surgery, but it also can go up, if the lens and cornea astigmatism offset each other.
JN9008 RonAKA
Posted
Very informative! Will they (Cataract surgery clinic) be able to test or at least estimate /predict the corneal astigmatism during the pre-op measurement? This is important so we can decide what to do if your Cyl in the glasses in say -1.0D.
RonAKA JN9008
Edited
They should tell you what the estimated residual astigmatism (cylinder) is predicted to be. There may be an extra charge for the needed measurements. As I understand it, an instrument like the IOL Master will be needed to measure the eye to calculate the IOL sphere power. It can also give slope measurements which will predict the residual cylinder and axis. A second instrument like a Pentacam can produce a coloured topographical map of the eye to show the pattern of the astigmatism. It also provides a estimate of the residual astigmatism.
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They should tell you what is estimated by the IOL Master as well as the Pentacam, but you may have to ask.
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If your surgeon is cooperative you should ask for a printed copy of the IOL Master calculation sheet. It should show the predicted outcomes of the various range of powers close to what you need. It is a very useful document to have so you know what was targeted and then after surgery you can compare what you got based on an eyeglass prescription at 6 weeks, to what was predicted. That is important information which can be used to make a more accurate prediction with the second eye, but again only if the surgeon is cooperative and diligent. Some will just wing it and do both eyes at the same time for expediency, or do them so close together that there is no settled refraction from the first eye to base any adjustment on.
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The other information to be aware of is that if you have astigmatism and decide against a toric lens, they will make your estimated refraction based on a spherical equivalent value. 50% of the cylinder is added to the sphere prediction to get a predicted spherical equivalent outcome. So, to some degree sphere will be used to correct some of the cylinder.
mart27056 RonAKA
Posted
Thank you for that clarification Ron. I have gone through two sets of measurements for iol's in the past couple of months. The corneal astigmatism from the first set of measurement was -0.88 RE and -0.75 LE. On the second set of measurements the results were quite different: -1.15 RE and -0.54 LE. They used the IOLMaster 700.
Due to the inconsistent results I have been scheduled for another round of measurements in a couple of days. Do you know if this level of inconsistency is common? The technician told me the surgeon has sometimes requested up to five measurements to ensure they are working with the correct numbers. I'm not sure if they are using any other instrument like the Pentacam for comparison but I will ask that question on my next visit.
RonAKA mart27056
Edited
I got two numbers for estimated cylinder, and I believe one was from the IOLMaster and the other from a Pentacam. They differed by about 0.3 D, and the surgeon said that he finds the actual outcome is somewhere between the two. If they are only using the IOLMaster I would ask for a Pentacam measurement.
RonAKA kdf123
Posted
Another thing to consider is that leaving some astigmatism uncorrected (cylinder) can improve your closer vision, but it will come with a cost of reduced visual acuity at distance. It is not likely to help much with near vision, but it can improve intermediate (1.5 to 3 feet) vision some.
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The critical information you need to know to make a good decision is the predicted amount of cylinder in each eye if a non toric lens is used.
kdf123
Posted
Thanks for the detailed reply. My surgeon has the exact eye measurement but Im about -5 RE and -2 LE. Not sure about exact astig numbers.
I also have several vision problems.
Black floaters, blurred floaters and vitreous flashing in the sides of both eyes.
Would trifocal(multifocal) lenses be an option with all my vision probs?
I believe that MFs are not a good choice if you have vision problems. Is that true?
Would monofocal plus like Vivity, Eyehance or RayOne be options for me?
My apologies for all the questions. Seeing how its a one time decision you have to live with I'd like to weigh all the options.