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Today I saw a doctor, I right eye is -17, he said it is too high power for sympony, my left eye is -11, my left eye could use it,
Do you know anything about this? Thankyou
0 likes, 8 replies
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dennis39810 lovewater07757
Posted
lovewater07757 dennis39810
Posted
softwaredev lovewater07757
Posted
I am guessing the doctor didn't realize this. It is very likely you *can* use the Symfony then since the lens power required is based on your eye measurements which the cataract wouldn't have changed. Even a rough guess at the IOL power needed should be done based on your prescription before the cataracts. I was more myopic than that, in the range of perhaps -6 and -9.5 or so (though the -9.5 might have been partly the cataract, it was just before it was diagnosed, I forget the prescription before that).
Although cataracts can alter refractions, usually the impact is only minor, so the doctor may not have realized it wasn't in your case. In some cases it can be drastic. I was one of those odd cases, my problem eye went from -9.5D to eventually -19D before cataract surgery, changed by the cataract, and I used a +10D Symfony (and the results suggest a +11D would have worked better for that eye, it wound up slightly hyperopic).
softwaredev lovewater07757
Posted
Also, I'll say that I suspect the lens power choice for you can be fairly accurate since you were a moderate myope (there is no one standard for how to describe myopia, but usually high myopia starts at -6, and moderate from -3). Usually they determine the risk of whether a lens power calculation will be off based on whether the axial length measurement is long, but usually a moderate mype won't have have that long an axial length measurement. My eye that was about -6D wound up with a lens that hit the power target, it was 0D at the first few exams after surgery, 2 years later it was -0.25D (and -0.25D astigmatism), which is close enough to still give me at least 20/15 vision in that eye. It might be minor measurement fluctuation since they only measure to the nearest 0.25, so I might be like -0.126D or something.
softwaredev lovewater07757
Posted
I wrote this before seeing your other post. If you weren't a high myope before surgery, its likely you *can* use the Symfony. I wrote this assuming you were always that myopic (as the doctor likely assumed), so I'll go ahead and post it to explain his thinking, and to suggest what someone else who really is that myopic could do:
They only make the IOL in certain lens powers, just like they only make contact lenses in certain powers. (if you wear contacts you are probably aware that not all models come in powers you can use). The Symfony site says currently they make it in: "+5.0 D to +34.0 D in 0.5 diopter increments". Unfortunately the power of an IOL can't be exactly determined from your current prescription. The lens power of the whole comes from 2 parts, the natural lens and the rest of the eye. Two people with the exact same prescription could have different lens powers in their natural lens since the rest of the eye is different also.
That said, back before they developed ways to measure the eye to try to get more accurate ways to determine the lens power, they made just a very rough guess: "In 1977, the state-of-the-art for estimating IOL power for emmetropia was to simply add +19.0 D to the pre-cataractous refraction.". So a very rough guess for the IOL powers you'd need would be +2D for the right eye and +8 for the left eye. Even if those guesses are off by 2.5 dipoters in either direction, it means the power needed for your right eye is lower than the lowest power Symfony (+5), but there would be a lens for your left eye. I don't know how much the rough guess could be off, if its possible your right eye could use a +5 lens but there is a good chance it won't.
They usually won't get a better estimate for the IOL power you need until they've taken a bunch of eye measurements for things like the axial length, which usually isn't done until the preop exam the week of your surgery when they need to order the lens.
That said, there is another issue to consider. They don't have an exact formula for determining the lens power, their formulas are based on a statistical analysis of the eye measurements and the lens powers that worked for them. For people who low (or no) prescriptions before surgery, the estimates are usually fairly accurate. For people with high prescriptions there is a greater chance the lens power choice will be off for various reasons. So for someone highly myopic, there is a good chance that even if they made lower power IOLs, that the lens power might be off after surgery. If the lens power is off, for those looking to be free of glasses, they can fine tune the end result using laser correction. The small adjustment they need to make using the laser is fairly accurate, and even those who weren't candidates for LASIK when they had high prescriptions can usually get a smaller tweak done since it alters less tissue.
Since you might have needed a laser adjustment anyway, another alternative then is just to use the lowest power Symfony in that eye, +5, knowing that it'll leave you hyperopic (farsighted) and plan to correct that via laser. They usually wait a bit for the vision to stabilize before doing the laser correction to be sure to get it right, so for perhaps 3 months (or however long they prefer to wait) you'd need to wear correction. That would be a little more correction than usual after cataract surgery (but still small compared to what most people who go for LASIK with a high prescription get), a few diopters probably, so it depends on if you are a candidate for that much laser correction (most would be, but you'd need to check). Alternatively, if they need to do a few diopters of correction, they could insert a piggyback 2nd lens, a monofocal, that corrects the other few diopters. Which solution is best depends on the patient and the doctor's preference.
softwaredev
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oops, I meant if you weren't a high myope before needing cataract surgery.
lovewater07757 softwaredev
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Thank you Soft, so much info. Yes, actually my cataract is the bad result of vitrectomy. I did vitrectomy in both eyes in 2010, at that time, I am -4, -4, mild myopia, although the surgeon said vitrectomy won't cause cataract , ,,,,,, five years later, I found I need to change glasses every month, from -4 to -11, -17.
?I am not sure my cataract surgery would be difficult, since I have vitrectomy alreay.
softwaredev lovewater07757
Posted
Unfortunately I don't know anything about how a victrectomy will impact cataract surgery, I've never needed one nor had reason to research it. I've researched some eye issues in depth due to my own needs, and out of curiosity reading related material while I was at it and since then to watch how IOLs advance, in case one day its worth the risk of an upgrade. Other eye issues I don't know enough about to comment on, I don't have a medical background. I just have enough science&math background to be able to make sense of studies, and of basic optics.