rljones
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 p.5 #2 · Cataract surgery and photography | |
I did not see this thread until tonight, so sorry for any delay. I hope I don't rain on any one's parade, but I'll nevertheless be direct in my opinions for future readers (well, based on current technologies).
I'll comment on a few issues raised in the OP. I can speak with some authority as I'm an ophthalmologist in private practice for a number of years as well as a photographer for a number of decades. [Furthermore, I trained under, and was the last associate of, one of the surgeons, Dr Richard P Kratz, who helped Dr Charles Kelman create the technique of phacoemulsification ('phaco') cataract surgery that we all use today.]
1) All diffractive multifocal (MF) implants (IOLs) have lower contrast than single focal (SF; aka 'basic') IOLs. This is without dispute (honest dispute). A simple thought experiment can help to illustrate the loss of contrast. Consider 100% of light, under a given condition, passing through a SF IOL. All of the light is being used for a distant object: this is maximum contrast with present IOL technology.
Under those same lighting conditions, looking at the same distant object, a MF IOL has only about 50-60% of the light (the exact percentage varies with different models) being used for that object. The rest of the incoming light (~40%) is for intermediate and near objects. This ~40% reduction in light for the distant object means a loss of contrast. Such loss is particularly notable at night, when humans already don't see well. So imagine driving on a dark, rainy night with low contrast vision. Do any of you like low contrast lenses for your cameras?
I do implant this style of IOL but only after having a similar, detailed discussion with the patient. If the importance of being without glasses after cataract surgery is paramount, then the lower contrast of MF IOLs may not be of concern for some patients and therefore such an IOL is a good choice. The Vivity IOL has slightly less distance loss of contrast than the other good diffractive IOL, the Pan-Optix; this latter model has better near focus as a trade-off with slightly lower contrast than Vivity (both are made by Alcon).
[There is also an astigmatic-correcting feature (unfortunately named 'toric' IOLs), which can be added to all of the IOL types described in this post. I shall not comment on this feature, except to say that it can be useful for distance-focused IOLs when combined with the right measuring equipment, proper formulas and good surgical technique.]
2) The one non-diffractive MF IOL presently sold in the US is the B&L Crystalens IOL. The problem with this IOL is that it does not work as advertised: it cannot properly focus up close as it depends upon muscle function (ciliary body). Since the average age for cataract surgery in the US is ~70 years, this means that these muscles have not been working for about 30 years. Accordingly, it's no wonder that this style of MF IOL does not focus well at near: the muscles are too weak to move it very much. This IOL does shift focus from distance to intermediate range (~1D of accommodative power), but not distance to reading range (which would require ~2 to 3D of focusing power, which the muscles no longer possess)––where intermediate is 2 to 3 feet and reading is ~16 inches. To get around the poor near focus with this IOL, some surgeons focus one eye at intermediate and the other eye at distance; the intermediate eye can then focus from intermediate to near (~1D) and the distance eye from distance to intermediate (again, ~1D). But this type of asymmetric correction does not provide the patient with true binocular vision. I do not use this IOL (and, it is not popular in Europe).
3) SF IOLs, which have the maximum contrast, will require glasses for some tasks. This is annoying for some patients. For example, if both eyes are focused at distance with SF IOLs, then readers will be required. Conversely, if both eyes are focused at near, distance (TV and driving) glasses will be needed. Occasionally, some patients ask for 'mono-correction'. This is where one eye is focused at distance (preferably the dominant eye) and the fellow eye is focused at near (or maybe, intermediate distance). I recommend such mono-correction only be done in patients who've worn contact lenses in this format. Even with mono-correction, patients often still use glasses for night driving (in order to change the near eye into a distance eye for better night vision).
For the above reasons, I would have basic (SF) IOLs placed in my eyes whenever I need cataract surgery. I personally prefer the idea of having the IOLs with maximum contrast in my eyes, using glasses as needed, over the convenience of lower contrast IOLs without the need of glasses. My preferred SF IOL for the past few years has been the B&L Akreos MICS.
4) Laser-assisted cataract surgery. Here, I'll be blunt (and probably offend many ophthalmologists). In my opinion, this is an over-hyped, over-priced and un-necessary technique, primarily useful for surgeons with meager manual dexterity. I'm trained in it but neither need nor use it.
Edited on Oct 02, 2021 at 10:39 AM · View previous versions
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