PRK Monovision 16 yrs ago - cataracts now, what in theory is best approach
Posted , 7 users are following.
PRK correction was 16 years ago - had wonderful vision up until a year ago, with cataracts now at L 2.5+ and R 1.5+.
Have not yet engaged with ophthamologist in our new hometown, but wanted to check opinions from those of you who are apparently quite knowledgeable.
Records of the original PRK are no longer available, btw.
How would you approach this?
0 likes, 30 replies
trilemma georgeP3
Edited
RxLAL if practical, but not a lot of places do it. Plus there are 4 or 5 more visits than with conventional IOLs, so if driving a distance, that is a hardship.
RxLAL is said to be good for people who had corneal surgery, that somehow can complicate fitting a regular IOL.
RonAKA georgeP3
Edited
I would ensure to get as accurate as possible measurements of your eye. Suggest you find a surgeon that has the IOLMaster 700 and Pentacam. No reason not to stay with mini-monovision. It is the lowest risk way of getting a full range of vision without eyeglasses. For a lens I would suggest using a monofocal that has a lower sensitivity to issues with the eye. While it may be a bit harder to find, I would suggest the B+L enVista. Do the distance eye first with a target of -0.25 D, wait 6 weeks for the eye to fully heal, and then go ahead with the second eye with a target of -1.5 D.
georgeP3
Posted
So, I continue to read, but am not getting some of the physics ...
Please correct me, but my sense is that since my PRK monovision worked so well, and I was very confident with it, there is no real advantage to doing much more than trying to replicate it via lens replacement - so "ifs" - IF my corneal curvatures were exactly the same, had not changed, etc, then a perfectly clear replacement lens would net a very suitable outcome. However, with changes that may have occurred to my corneas, it is likely there is some benefit to being able to change the lens once it is implanted?
Another IF ... broadly, if the applied science has resulted in improved devices to assess my cornea and other refractive elements, then it would be reasonable to take advantage of that science just in case?
To confirm, my PRK gave me monovision, and if I did the LAL looking for the same outcome, it would called "mini-monovision?" If successful, could I potentially have better vision in both eyes, or better in-between vision? (is this called EDOF?)
And, a financial component ... insurance would probably cover a standard replacement lens - but, does this mean only a clear lens, or would this include a best guess at refractive improvements based on basic assessment?
I continue to try and understand more so I can choose the right surgeon - some have not invested in the LAL equipment (and, obviously tend to not recommend LAL). There is one surgeon in my geographic area and multiple trips are no problem if the outcome will be better. The PRK was expensive, but worth it.
To be clear, I have LOVED not requiring eyeglasses - and, until the cataracts started to affect my eyesight, I was extremely pleased with my PRK monovision. If there is a chance I can return to that same spot - or even better - I am willing to try it!
georgeP3
Posted
Looks like comments died out a bit ...
First appointment with local opthamologist today - 30 years experience, she said she had not yet ben convinced of the need for LAL although sees promise.
We discussed my previous PRK and how it would work with Vivity lenses - it sounds as if she believes I would, assuming the correct choice is made for each lens, end up with better than PRK in both eyes since the Vivity provides some EDOF - so, good long, better mid range where left and right would overlap, and better near.
trilemma georgeP3
Posted
Sorry... had missed your earlier question on EDOF. I guess you now know that monovision is not EDOF (extended depth of focus). EDOF divides up the light to focus a range of distances.
phil09 georgeP3
Posted
"...she said she had not yet ben convinced of the need for LAL"
Well, there is no need if your surgeon can hit the refraction target right on the nose without LAL. But surgeons are VERY quick to say that they offer no such guarantee, and that a substantial error is quite possible, especially if you've had prior refractive surgery like PRK.
If there is an error, the surgeon using LAL can make an adjustment. The surgeon using a non-adjustable lens can say "Oops, here are your eyeglasses." Or, "Let's discuss the next surgery we can try, to fix the first surgery."
I'm in about the same situation as you - I love my LASIK monovision, and hope to continue not needing glasses. I'm considering the LAL, but have made no decisions yet. Good luck to you.
Guest georgeP3
Posted
LAL was recommended because it's harder to get accurate target predications with the IOL Master in post refractive corneal surgery patients. So if they miss the target they can tweak it after surgery.
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Vivity has a modestly extended range that only promises "functional" near and it comes at the expense of contrast sensitivity. Although in good light you will not notice any contrast issues. To get good reading with Vivity you will still want one eye slightly nearer.
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If you were happy with regular monovision for 16 years I'd tend to think it might be best to stick with what you know. A lot of surgeons don't like monovision and don't suggest it but you'd think that when faced with a patient that lived happily with it for 16 years they'd be ok with it?
RonAKA phil09
Posted
I agree that LAL would be the most certain way of getting the best mini-monovision after prior PRK or Lasik surgery eyes. However, if the objective is only distance vision and you are planning to use readers (or progressives), then you get two chances at hitting an ideal distance vision with standard monofocal lenses.
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And using standard monofocals or more tolerant lenses like the B+L enVista are not out of the question for mini-monovision. With some additional care hitting targets without going to LAL is reasonable. Some ways to improve accuracy in target outcomes would include:
georgeP3
Edited
Thanks, All.
The ophthalmologist said the long target would be plano, and the short eye -0.50. Does this mean "tuning" the short eye (left non dominate) a bit shorter?
RonAKA georgeP3
Edited
Responsible surgeons do not actually target "plano". Your surgeon may be speaking loosely! Targeting plano or 0.00 D refraction is risky as achieving the target exactly is unlikely. When you target 0.00 D the error could be positive or negative. When you go into the plus zone above 0.00 D then you are becoming far sighted. Being far sighted reduces your distance vision AND your near vision. The plus side of 0.00 is considered a no go zone by most surgeons. For that reason they target -0.25 D or close to it instead of plano when the objective is 20/20 distance vision. In most cases -0.25 D still gives 20/20 vision.
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Targeting -0.50 D is almost insignificantly different than targeting -0.25 D. A step of 0.25 D is the smallest possible step in vision optics. From test to test it is common for results to vary by that much from one test time to another. It is in the "noise" range. But, yes if they actually hit -0.50 D it will give a slightly better close vision, and it will put getting 20/20 distance vision at risk. It does lower the risk of going positive more than targeting -0.25 D.
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So the bottom line is that this surgeon is essentially targeting distance vision in both eyes. Normal practice is to set the target for the second eye, after the refraction at 6 weeks after the first eye surgery. That way they can adjust the formula to be more accurate on the second eye. If these are monofocal lenses you are virtually certain to need readers of about +2.0 to 2.5 D power. You probably will get away being eyeglasses free for driving though.
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You have not mentioned lenses to be used, but I would suggest considering Bausch & Lomb enVista IOLs. They are more tolerant to less than perfect eyes, which is what you will have after PRK surgery. They are not as commonly used as other monofocals, so you may have to switch surgeons to get them though. They are also suitable for mini-monovision if you want to consider that. Common practice is to do the distance dominant eye first, see the outcome at 6 weeks, and then consider whether or not to do mini-monovision with the second eye. In that case the target would be -1.50 D instead of -0.25 D. That will give reading vision and avoid the need to carry around readers. So, you can leave options open until the second eye is done.
georgeP3
Posted
Sorry - I probably didn't provide enough detail.
I have been mono vision from PRK for 16 years - no issues, no glasses until the cataracts.
This surgeon recommends Vivity for both eyes, would implant the non-dominant (short) eye first, then wait a couple of weeks, then the long eye. This sounded like mini-monovision - or blended - although it isn't clear they are different terms for the same thing?
I questioned her carefully - asking if this was mini-monovision and if I would have better or worse vision than with the mono-vision PRK? She believes I would improve both short and mid range vision while retaining the same 20/20 (actually a bit better following PRK).
She did want the records from the PRK so I have asked if these are available - they may not be since it has been so long.
RonAKA georgeP3
Edited
If you want to compare your expected vision to what you have (had) with PRK monovison you would need to know what your refraction is for each eye as a result of the PRK. That is your eyeglass prescription which will have sphere and cylinder numbers. The near eye prescription would be the important one as it determines what your reading vision would have been like. IOLs are not going to be quite as good, and you may need slightly more myopia in the near eye to get the same vision because current IOLs do not have any accommodation ability to change shape and focus closer like a natural lens has (at least when you are younger).
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I looked at Vivity seriously. If you go with it, I would only do it in the near eye. There is really no advantage to a Vivity in the distance eye because the near eye will easily cover the intermediate range and the extended near vision of the Vivity would not be of significant value. I considered it for my near eye while having a standard AcrySof IQ monofocal in my distance eye, but got talked out of it by the surgeon. It would have been an extra $2,200 cost, and he indicated that he thought I had high expectations for good vision and would not be satisfied with it. The Vivity is an extended depth of focus lens and does compromise visual acuity some as it stretched the focus point. Contrast sensitivity is also compromised, quite a bit, which can make night driving more difficult. The advantage of the Vivity is that it does not need to be targeted for as much myopia to get good reading. A standard monofocal in a mini-monovision configuration would normally be targeted to give -1.50 D of myopia. The Vivity extends depth of vision by 0.5 D, so the near target if a Vivity is used can be lowered to -1.0 D, and essentially get the same near vision. This allows better distance vision with the near eye.
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The Vivity is certainly an option, and I recall there is a contributor here that has it in a mini-monovision configuration and is pleased with it. But, I would only do it in the near eye. When you use a standard monofocal like the Clareon or enVista in the distance eye, you get full contrast sensitivity with it, and that makes up for the loss in the Vivity eye.
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Blended vision and mini-monovision is essentially the same thing. The history of monovison is that full monovision (-2.0 to -3.0 D in the near eye) got a bad name due to people not being able to adapt to it. So, some vendors and surgeons use the blended vision term to avoid saying it is monovison. RxSight who market the LAL lens would be one example. Same thing different term for marketing purposes...
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My recommendation still would be to try and find a surgeon that uses the B+L enVista lens and just do standard mini-monovison with it. With your prior PRK you will likely benefit from a more tolerant lens to a less than perfect cornea. Alternately do Clareon in both eyes, or Clareon in the distance eye, and Vivity (targeted to -1.0 D) in the near eye. -0.5 D is not enough in the near eye with a Vivity to give good near vision.
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If you want to spend extra money on your surgery I think it would be better spent on getting your eyes thoroughly measured using both the IOLMaster 700 and Lenstar LS-900. The outcome should be compared using formulas known to work with previous PRK eyes, and if the predictions are not consistent then perhaps a third measurement with the Alcon Argos Biometer. This may mean seeing more than one ophthalmologist to get the measurements done.
georgeP3
Posted
Thank you for your thoughts and a quick update...
I made appointment with the only LAL practice in my area for mid December. I will delay the preop with the practice recommending Vivity near and far.
So, to help me understand, please. In theory, if I was seeing 20/20 plus and J1 with PRK monovision, and there had been no changes other than cataracts, why wouldn't a clear lens without correction in both eyes simply solve the cataract obscuration problem and return me to post-PRK sight?
Another subtlety I should have noted - the surgeon noted I was seeing 20/20 (barely) with right eye (1+ by the optical doc), but noted the left (rated 2+ for cataracts by the optical doc) was the biggest issue). Further, that the single biggest issue was how massively the glare affected the left eye (when the LED lights were used, the left completely blanked due to the glare - less so, but still problematic in the right).
Self tests-
Left eye - I can see very well any sort of very small print with left (short) from 6"-12" - blurrier at less than 6", blurrier after 12". Computer screen viewing works OK, but only with right (long) eye contributing. Left eye used to contribute to long vision, but no longer does this (cataract). Lots of dysphotopsia (glare, haloes, doubling and tripling images, ghosting) at night looking at traffic lights.
Right eye - blurrier and blurrier as gets inside 15" or so. Fine outside that - not as good as it was, and have more dysphotopsia at night than I once did.
I really appreciate everyone's comments and education - please keep trying to make me understand!
phil09 georgeP3
Posted
"In theory, if I was seeing 20/20 plus and J1 with PRK monovision, and there had been no changes other than cataracts, why wouldn't a clear lens without correction in both eyes simply solve the cataract obscuration problem and return me to post-PRK sight?"
You saw 20/20 after PRK only because your natural lens, in concert with other structures of your eye, properly focused light on your retina. If the natural lens is removed and replaced with essentially nothing, you will need very thick "aphakic" spectacles to properly focus and give you some decent vision. You can't just remove an important structure like the lens of your eye and expect it to still function normally. You need to replace it with an artificial lens to retain your good vision.
If I misunderstood your question, sorry about that!
RonAKA georgeP3
Posted
In theory, if I was seeing 20/20 plus and J1 with PRK monovision, and there had been no changes other than cataracts, why wouldn't a clear lens without correction in both eyes simply solve the cataract obscuration problem and return me to post-PRK sight?
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Good question. The complication is that your PRK correction to the cornea includes what is needed to correct the cornea error plus what is needed to correct the lens error. It is highly unlikely your lens error was zero, so you have to replace the lens with an IOL that basically has the same error as your natural lens. The second issue is that your natural lens will still have some accommodation or the ability to change shape to focus close. Current IOLs do not have that ability, so you will need a little more myopia in the near eye to see the same close up.
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The cataract is most likely causing the glare issues.
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The very best way to measure your current eye is with an eyeglass refraction (phoropter test - which is better? One or two?) Ideally you want it from before you had cataracts. Based on your comments about what is blurry, you may be around -2.0 D. Since IOLs have no accommodation you may have to put up with a little less than that with them. The standard mini-monovision is -1.50 D in the near eye. That is a good compromise to get near vision for reading and still retain some good intermediate vision out to 6-8 feet or so. It sounds like you may currently have a bit of a gap in that range from your near eye, and the distance eye with accommodation is making up for it. That will be lost with an IOL.
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There are good reasons to go for -0.25 D in the distance eye (very slight myopia to reduce the risk of going far sighted), and -1.50 D in the near eye. Overall those targets should give good vision from about 1 foot (possibly less) out to the moon with the two eyes combined.
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The up side of the LAL is that you may be able to go right to plano (0.00 D) with the distance eye, and right on -1.50 D with the near eye. And if you don't like -1.50 D in the near eye, they can give you more, or less than that with post surgery adjustments.
RonAKA phil09
Posted
Perhaps to clarify (or possibly confuse) a bit, if you take a person with perfect vision with perfect corneas and normal sized eye, and perfect lens in the eye, it would take an IOL power of about +19.0 D to maintain that perfect vision when lens removal is done in cataract surgery.