Cataract Surgery

[yaox127]

Hello forumers so I wanted to ask regarding the monofocal in cataract surgery. I read even for a monofocal there were different brands like multifocals but many people weren't picky about them. Are there differences between the brands of monofocals? What indicates a "good monofocal". Not trying to sound picky here but wanted to know for my own good. Thanks in advance!!

[SoftwareDeveloper]

Although all cars may provide basic transportation, that doesn't mean there aren't important differences for a prospective buyer to consider. Similarly, monofocals aren't all the same, even if the differences between them are smaller than the differences between premium lenses, but unfortunately there don't seem to be many studies done on them. If you are an area with multiple good surgeons, you might be able to hunt for one that will give you a good choice.

Just as many doctors may merely write a prescription for eyeglasses, neglecting to consider differences between the sort of lenses you can buy to fill that prescription, many don't consider the differences between monofocal IOLs since medically they are mostly the same and they fill the basic function. However just as the material eyeglasses are made of can impact the visual quality due to chromatic aberration, the same is true of IOLs. This trade publication discusses the issue of the different lens materials and their impact on chromatic aberration, noting:

http://eyeworld.org/supplements/EW-December-supplement-2014.pdf
" Cataract surgery with an IOL with an Abbe number greater than that of the natural lens (47) can improve CA, so that our cataract patients could actually experience better vision quality than they did as young adults. "

There are some IOLs that claim to have a larger depth of focus than other monofocal IOLs (i.e. providing better intermediate&near than a standard monofocal), but I haven't investigated the claims in depth since there unfortunately doesn't seem to be much data. I've seen claims of that for IOLs like the SoftTec HD, and a few weeks ago I saw a similar claim made for the Envista IOL here:

http://eyetube.net/series/daily-coverage-new-orleans-2016/eekid/

Though I hadn't seen data. There is a Hoya lens that I think there is credible evidence has an extended depth of focus, its been studied by Dr. Graham Barrett, the iSert Gemetric 751, but oddly I'd heard it wasn't being commercialized last I checked on it even thought its FDA approved (though I recently read Bausch&Lomb are going to market Hoya lenses, so perhaps that might be changing).

Although people mostly hear of issues regarding halo&glare with multifocals, there is a risk of problems with those issues even with monofocals, and the risk varies. Unfortunately I haven't seen a good head to head comparison between them (it might exist, I hadn't researched it much), however I noticed the issue when reading the data submitted to the FDA for approval of multifocals from Alcon and Tecnis. They used monofocal lenses as controls in the study and gave data regarding the level of problems people had with them. Unfortunately its possible the studies used different questions so the data may not be directly comparable (thats why you want a head to head comparison in the same study), but the data is different enough that it suggests its worth looking into, here is data on the monofocal control lenses in studies on Tecnis and Alcon lenses:

Tecnis:
http://www.accessdata.fda.gov/cdrh_docs/pdf/P980040S049d.pdf
"Table 20
Ocular Symptoms (First Eyes( at 6 Months)
Halos 4.1%
Glare 1.4%
Starbursts 0%"

Alcon:

http://www.accessdata.fda.gov/cdrh_docs/pdf4/P040020S050c.pdf
"Table 1
Rates of Visual Disturbances, 6 Months After Surgery
Halos 39%
Starbursts 39%
Hazy Vision   34%"

Different lenses also have different rates of PCO, an issue that a minority of patients get where the lens becomes cloudy later due to cell growth and a YAG laser treatment is needed to clear it up, but I hadn't checked on those figures.

Given that most people get monofocal IOLs, it is unfortunate that there aren't more comparison studies or marketing  literature comparing them in more detail.

[JohnHaganMD]

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[yaox127]

Thanks for all the information SD! Many surgeons however don't go into detail on which monofocals they tend to plan to use and vision counselors do not know as well when deciding on the lenses. An interesting story I had was a clinic offered an "extended depth of focus" IOL that cost about 900$ per eye that wasn't covered by insurance. I have never heard of these types of lenses so I had to do some more research from their clinic. I was told "Naturally an IOL that could correct astigmatism and provide extended range of vision will become an option for our patients"

Sounds like one of those monofocals that give you extra range of vision but isn't necessarily a multifocal. But I've never heard of a lens that corrects both astigmatism and provides extra range of vision unless Toric IOLs differ among one another too between brands, then that is an entire new story to me as it's my first time hearing about it. Do Torics differ among one another as well or am I missing an entire different lens?

Also I've been getting different opinions in correcting astigmatism. I will quote a few here:

"My current approach to patients who want near and distance uncorrected vision and who also have significant astigmatism is to use a non-toric multifocal implant and to correct the astigmatism on the cornea.  This works well and is a more physiologic approach than using a toric implant which corrects the corneal astigmatism in the lens (as opposed to correcting the corneal astigmatism  on the cornea as I do)."

"Get the Symfony toric. Astigmatism correction using a lens is much more precise than corneal methods as corneal methods rely on patient wound healing which is variable."

So the first doctor seems to prefer a procedure for the cornea prior to using a multifocal implant. The second doctor (that participated in the Symfony trials) had a different opinion and said a Toric verseion lens itself was more precise. May I know your thoughts on this concern?

[JohnHaganMD]

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[SoftwareDeveloper]

Toric monofocals would differ between each other just as other monofocals would in terms of things like chromatic aberration and depth of focus, PCO and halo&glare risk, etc. There are also premium lenses that have toric versions like the Trulign which is the toric version of the Crystalens, and apparently the toric version of the Symfony was approved along with the non-toric (which I was surprised at, given they still hadn't approved toric multifocals so I would have guessed they'd need a separate approval process).


Doctors differ in the degree of astigmatism they prefer to correct via an incision  on the cornea, or via lens. Usually they prefer to correct a small amount of astigmatism on the cornea, since as one of your quotes notes, that is where the astigmatism exists so it makes sense to fix it there. What they do is to make an incision and then the eye will reshape itself. The problem is that everyone's eye is different and so they can't predict exactly how much the cornea will reshape in response to the incision, so the correction isn't precise.That is one reason they prefer to correct larger amounts of astigmatism with a toric lens since its more predictable overall (though there is some potential for the lens to rotate a bit). That said, there are some surgeons that use laser incisions and feel that data shows them to be accurate enough to use to correct even a few diopters of astigmatism.

You don't mention how much corneal astigmatism you have. They need to determine with  a corneal scan, it isn't the same as your prescription since that includes includes lenticular astigmatism, i.e. astigmatism from the natural lens,  which goes away when the lens is removed. Though your prescription astigmatism would give some general ballpark idea of if its likely to be low or high since usually most astigmatism is from the cornea (though cataracts can impact astigmatism so an older prescription would be a better guide).

[JohnHaganMD]

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[JohnHaganMD]

First you likely will not have a choice on monofocal IOLs because surgicenters cannot afford to stock every brand and power. Second all over the world monofocal technology is excellent. It's just like automobiles. You may quibble about which is best but Ford, GMC, Honda, Toyota, BMW and others all make excellent autos.