Advice needed on postop cataract patient

[ilanh]

I have an 80yo patient who had surgery 3 months ago. The patient received IOL implants in a monovision strategy ie: -2.25 OD and -0.50 OS. BCVA postop was 20/30 OU. Uncorrected vision for distance was 20/30 and for near was J1. The vast majority of patients on whom we use this approach can see very well for both distance and near without glasses. We generally try to keep the anisometropia under 1.50D and we correct the non-dominant eye for near. This patient however complains that he has a "pulling" sensation at both distance and near. He claims that he is uncomfortable both with and without his glasses. His symptoms seem to suggest anisometropic asthenopia despite a relatively meager difference of 1.75D. I would like to modify his glasses with prism so that he is more comfortable. Any suggestions on how to do this? I could put slab off for his reading, but what about this distance? How much prism and in what direction?

[npdr]

Prismatic correction presupposes a binocular conflict. If the patient is complaining of blurred vision I am not completely satisfied that it is a binocular problem.

Central fusion continues up to 20/20 in one eye and 20/60 in the other eye. If the distance vision in the poorer seeing eye is less than 20/60, the central fusion is lost and peripheral fusion is what is keep the patient from seeing diplopic.

Only 50% of the population can "retinal switch" or go back and forth easily with monovision (of <1.50 to 1.75D) The other half cannot switch even with 1.00D difference.

I believe you may have a patient who is unable to do retinal switching, may have central fusion retained because the vision is still better than 20/60.

The solution? Put a bifocal contact on the near seeing eye and see if this works. At 1.75D difference, I doubt that you will get vertical spectacle prismatic effect unless there was vertical before surgery.

I have heard and seen some patients who have had veretical or horizontal deviations increase after cataract surgery and seems to be related to the anesthesia given.

[ilanh]

Prismatic correction presupposes a binocular conflict. If the patient is complaining of blurred vision I am not completely satisfied that it is a binocular problem.

Only 50% of the population can "retinal switch" or go back and forth easily with monovision (of <1.50 to 1.75D) The other half cannot switch even with 1.00D difference.

I believe you may have a patient who is unable to do retinal switching, may have central fusion retained because the vision is still better than 20/60.

The solution? Put a bifocal contact on the near seeing eye and see if this works. At 1.75D difference, I doubt that you will get vertical spectacle prismatic effect unless there was vertical before surgery.

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Your observation on retinal switching on monovision most likely applies to contacts or lasik, not intraocular lens implants. I've done monovision IOL's on hundreds of patients and the intolerance rate for anisometropia of 1.50 is negligible. I think of it like a continuum ie: monovision with glasses works horribly; with contacts/lasik works better; with IOL's works best. This patient is not a candidate for contacts.

[braheem24]

You have 2 options for a multifocal.

1. Slab-off.

2. Fit him in a fairly shallow "B" frame (30mm) fit his bifocal at regular placement. Ask the lab to put the O.C. at 15mm or whatever half of the "B" measurement.

The shallow "B" forces him to not stray too far from the O.C.

Make sure the lenses have matching B.C. to reduce image size imbalance.

You would in essence be splitting his vertical imbalance between the distance and near. Number 2 is not the textbook approach but it works, it's your call.

[Robert Martellaro]

This patient is not a candidate for contacts.

Or monovison for that matter.

Sorry, but I strongly disapprove of pemanent monovision. It seems like too much of a two steps foward, one step back approach.

The visual comfort with eyeglasses will be best (if there are no other complications) when you align the OCs on the vertical meridian with the pupil center and the position of gaze, eliminating vertical prismatic imbalance. Image size disparity can be minimized or eliminated by manipulating the BC and CT of the right lens. Fit as close to the eyes as possible.

I hope this helps your patient see more comfortably.

[npdr]

Your observation on retinal switching on monovision most likely applies to contacts or lasik, not intraocular lens implants. I've done monovision IOL's on hundreds of patients and the intolerance rate for anisometropia of 1.50 is negligible. I think of it like a continuum ie: monovision with glasses works horribly; with contacts/lasik works better; with IOL's works best. This patient is not a candidate for contacts.

The presumption about retinal switching does occur with IOL's as well. I've followed hundreds also and I find that I have had to fiddle with the glasses prescription to keep the patient happy with the outcome.

I think that back in the days of aphakic contacts, everyone up to 96 y/o was able to be fit with a contact lens. If the contact lens intolerance is due to pathology, that might be deciding, but not being a candidate because of just age isn't quite true.

[drk]

I'm in agreement w/ RM: I don't like IOL mono.

I think np and ilan are likely right with this being EOM strain from fusion, but you need to prove it:

• You could eliminate the disparity w/ a SV CL (dist and/or near) for proof of palliative effect.
• You could use a prism bar to measure fusional vergence reserve very simply, with SpRx.

If so, you may need conductive keratoplasy on the more minus eye! It's simple enough if you have a colleague that does it.


Another brain-storm could be that it's EOM not related to mono. He may be simply adjusting to life w/o specs. Again, angles in the 9 cardinal positions, vergence reserves need evaluated. Don't sleep on the vertical deviations!

PM me for how-to's.

[ilanh]

I'm surprised at how many negative comments regarding monovision IOL's. npdr mentioned that he's followed "hundreds". I find that unusual since very few people are doing as many of these as I do. It took me many years to amass hundreds of cases (since not all my cases are monovision). RM and drk both mentioned that they disapprove of permanent IOL monovision. Is this a theoretical disapproval or based on actual experience? I have hundreds of patients who have had this done, always shooting for an anisometropia no greater than 1.50. About 95% of them have wound up close to -0.25 to -0.50 in the dominant eye, and -2.00 to -2.25 in the reading eye (with the help of LRI's and toric IOLs). The reading has uniformly been excellent even with such a low add due to the magic of pseudoaccomodation (up to 1D extra). I have followed these patients for years and they spend 90% of their day without glasses. In 5 years of doing this I have had no more than 2 or 3 disgruntled patients. The vast majority have been thrilled. I am not posting this to blow my own horn, but am genuinely intrigued as to what others have experienced and why they are not as impressed with this as I am. I have surgery tomorrow on 8 patients and 5 of them are getting monovision.

[DragonLensmanWV]

Or monovison for that matter.

Sorry, but I strongly disapprove of pemanent monovision. It seems like too much of a two steps foward, one step back approach.

The visual comfort with eyeglasses will be best (if there are no other complications) when you align the OCs on the vertical meridian with the pupil center and the position of gaze, eliminating vertical prismatic imbalance. Image size disparity can be minimized or eliminated by manipulating the BC and CT of the right lens. Fit as close to the eyes as possible.

I hope this helps your patient see more comfortably.

I agree completely. I have 1D difference and that is easily bearable.
And if the difference is too great, then their glasses will be less than optimal.

[npdr]

I'm surprised at how many negative comments regarding monovision IOL's. npdr mentioned that he's followed "hundreds". I find that unusual since very few people are doing as many of these as I do.

I work with some of the most advanced surgically inclined surgeons over the last 6 years within a 9 ophthalmologist group.

[drk]

My experience is from CL fitting and long-term refractive surgery post-ops. It's difficult to get monovision to work, period.

I think, as has been mentioned, that one diopter is the magic number. Anything one diopter or less is "OK". Anything greater than that poses big problems for overspecs.

Surgeons love monovision, but long-term care docs, no so much. It's overly ambitious--most of the oldsters are more than fine with spectacle correction, plus their vision will be better. No need to be a cowboy. I think you like the idea more than they do.

Not only that, but "what if": ARM, pre-retinal fibrosis/macular hole, etc.? Let them have their binocularity.

Also, seniors have worse reaction time driving, dark adaptation issues, etc. Why not give them full correction OU? They need it.

[ilanh]

I work with some of the most advanced surgically inclined surgeons over the last 6 years within a 9 ophthalmologist group.

npdr, just out of interest, do your docs do any fusional testing before deciding on monovision? Or do they simply correct the dominant eye for distance and the non-dom for near? Do they have strict limits on the amount of anisometropia that they induce? Do they insist on elimination of cylinder in every case? The last issue is very critical because if you've left more than 0.50 of cylinder in the dominant eye you defeat the purpose. The near eye can have up to 1D of cylinder with no problem. For this reason, I always insist on either a toric IOL or limbal relaxing incisions in the dominant eye. Also, I never do monovision IOLs in patients who have any macular pathology at all. I've also done a fair amount of presbyopic lenses (restor) and have been much happier with the monovision.

As an analogy: Have you noticed how successful monovision contact lens fittings are in patients when the anisometropia is small ie: in an emerging presbyope? I've found that if I can keep anisometropia less than 1.00 in a monovision contact lens fitting or lasik, my success rate is very high. Much above this I often fail if I'm doing a first time fit. However, if a young person starts with a low monovision anisometropia they will almost never have a problem ratcheting it up to higher levels as they get older. The reason being, they've gotten used to it. One of the main reasons for monovision contact lens failure is not giving it enough of a chance. However, with IOL's many of these issues are resolved. Firstly, the IOL is closer to the retina than the cornea or than glasses (this is probably the main reason for success). Second, the anisometropia can be kept to 1.50 in ALL age groups (can't do this with contacts or lasik). Third, the patient has no other choice but to get used to it (can't take it off like you can with contacts). I would be quite interested to see if others have had the same degree of success (but one has to compare apples with apples)

[npdr]

ilanh,

1. I do fusional testing, but that doesn't mean they follow it or the patient wants to bide by it.

2. I do trials of monovision with cl's. I believe that a rough estimation to an IOL may be approximated by the patient's reaction with a threshold of 1D of disparity. In my opinion, a 1 D disparity that causes patient dissatisfaction should be a precautionary note.

3. I have found that modified bifocal and modified monovision do equally well for planned anisometropia. I think a hyperope will do much, much better than any myope.

[Bev Heishman]

I have worked with a similar situation. After exhausting many options, PRK was done to the undercorrected eye. Distance was then 20/25 with no imbalance. Rx OD .00 -.50 x 90 & OS -.25 -.50 x 78 with a +2.00 Add OU.

The patient still complained of multiple problems in wearing an overcorrection that included bifocals, Freeform progressives and NVO's.

I finally used an Office lens for close and a pair of SV DVO. Pt likes the office and it works. However can not tolerate DVO at all.

The patient was sent to a physician who specializes in neuro/muscular ophthalmology. With the testing done it was determined that there was a resulting aniseikonia present. Patient was told that they would always have this present and not be able to tolerate any full time distance correction. Apparently the binocular visual system is very sensitive.

Pt is happy with the answer and wears the Office lenses to do near vision tasks.

My question is are the optics of the IOL producing this? Patient had a 1.25 imbalance for the entire time they wore spectacles prior to cataracts developing and never had problems.

[npdr]

'...My question is are the optics of the IOL producing this? Patient had a 1.25 imbalance for the entire time they wore spectacles prior to cataracts developing and never had problems.

The presumption is that if the power of a lens is placed near or at the nodal point of the eye, there should be no magnification differences, thus no hint of aniseikonia.

However, there are instances where this doesn't hold true. One is the axial length which can introduce a slight size difference.

I believe that the issue of dissatisfaction with monovision IOL, monovision CL's and bifocal soft lens (simultaneous vision) is more related to retinal switching which only 50% of the population has.

[fjpod]

Ilan, I'm not so sure prism will have any positive impact in this case as far as I can tell from your brief case history. It's not like you had the patient in a multifocal spectacle Rx and he was complaining about vertical imbalance.

I am not saying I know better than you, but I do co-manage many cataract cases, and when we attempt a bit of monovision, we shoot for the dominant eye to be plano, and the nondominant eye to be -1.00.

I noticed you made his left eye dominant for distance. In my experience, unless there is some other extenuating circumstance, like low vision, or amblyopia in the right eye, we almost always make the OD dominant for distance. Did you test carefully several ways for ocular dominancy before surgery?

In other words, I don't think you have a prism balance problem here, nor the anisometropia. I think it might be which eye is dominant for distance.

[jediron1]

I have an 80yo patient who had surgery 3 months ago. The patient received IOL implants in a monovision strategy ie: -2.25 OD and -0.50 OS. BCVA postop was 20/30 OU. Uncorrected vision for distance was 20/30 and for near was J1. The vast majority of patients on whom we use this approach can see very well for both distance and near without glasses. We generally try to keep the anisometropia under 1.50D and we correct the non-dominant eye for near. This patient however complains that he has a "pulling" sensation at both distance and near. He claims that he is uncomfortable both with and without his glasses. His symptoms seem to suggest anisometropic asthenopia despite a relatively meager difference of 1.75D. I would like to modify his glasses with prism so that he is more comfortable. Any suggestions on how to do this? I could put slab off for his reading, but what about this distance? How much prism and in what direction?

This is a fairly mild rx to be precribing or wanting to elevate it with slab or prism. But I guess it can't hurt. I would go with a slab in OS a min. Of 1.5 and go with 1base up prism in OD. You should be able to simulate this in the chair which trial framing them.

[drk]

I've never had a "pulling sensation" as a CC for anisometropia. In, like, 20 years of practice.