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cataract IOL power confusion
hello ,i am 35 been diagnosed with moderate cataract ,and decide to get the surgery done since i am already having extrem mayopia my question is about the power of the IOL that will be used for my surgery, i been using comtact lense - 26 for almost 10 years now ,i am thinking i need a strong IOL power to correct the most of my vision error ,but my doctor told me the calculation he ce up to is that the IOL would be - 5.0 D as the lowest power available and i will need eyegalsses of atleast - 6 after the surgery ,i am just worried because what - 5.0 D are going to do against -26 i knpw that the IOL are going to be inside the eye not like contact lense but still, can anyone please explain toe how my doctor came up with those calculation ?, if i end up with -6 after the cataract surgery that would'nt be bad but just want to know more ,thanks.
thanks everyone ,i appreciate your help, i understand now that the measurements they made involve the power of the cornea and how large is the eye as the distance between the IOL and the retina have to be taken into consideration ,i am learning more about the cataract surgery,i hope everything will go well.
1 Comments
Take your time, get it right, get several opinions. This forum is full of people who regret rushing into cataract surgery not understanding all the variables, risks and complications.
re: "I am just worried because what are -5.0 D are going to do against -26"
Right now you are seeing through two lenses, your natural lens and your contact lens (and the rest of the eye has lens-like properties also, but that won't change by replacing the natural lens with an IOL). The contact lens needs to offset the power of your natural lens which is too strong. Right now you need a -26 contact lens because your natural lens power is too strong, e.g. the equivalent (at the contact lens plane) of being +26 too strong.
Your natural lens has a positive power, which might be for instance the equivalent to a +20 contact lens (to just use a typical number, I'm just explaining how to think about it, not giving precise numbers). So to replace it with a lens to give you perfect vision you'd wish to reduce its power by that 26, adding in the -26 correction your contact lenses give you now, which means (+20 - 26) = -6. I'm just explaining the concept, that isn't how they actually determine the lens power because they don't know exactly what the power is of your natural lens since they can't measure it directly. (again the rest of the eye acts as a lens, so testing your vision with a chart is based on the power of the rest of the eye as well as the power of the natural lens, and they don't know how much is from what).
They determine the lens power by taking measurements of your eye and comparing them to measurements of other people's eyes and the IOL power that worked for them. It isn't an exact process, it is based on statistics, and although it works well for most people, for those with high prescriptions there is a greater chance of the IOL power being off a bit. So even if they do find a lens they hope will give you perfect vision, there is some chance it might be off a bit. It seems better to risk the lens power being off in the direction of being a bit myopic rather than hyperopic since myopia is easier to correct using a laser if you wish to do so.
If you are left -6 myopic after cataract surgery, you could consider either laser correction or an ICL (implantable collamer lens, or sometimes called an implantable contact lens), though surgeons disagree over the risks of an ICL, the doctor here seems skeptical of them, but others think they are a good option so its something you'd wish to research carefully if you discover you need further correction after surgery.
As the doctor mentioned, its likely good to check around to see if another surgeon can get a lens that will come closer to correcting your vision entirely.
Right now you are seeing through two lenses, your natural lens and your contact lens (and the rest of the eye has lens-like properties also, but that won't change by replacing the natural lens with an IOL). The contact lens needs to offset the power of your natural lens which is too strong. Right now you need a -26 contact lens because your natural lens power is too strong, e.g. the equivalent (at the contact lens plane) of being +26 too strong.
Your natural lens has a positive power, which might be for instance the equivalent to a +20 contact lens (to just use a typical number, I'm just explaining how to think about it, not giving precise numbers). So to replace it with a lens to give you perfect vision you'd wish to reduce its power by that 26, adding in the -26 correction your contact lenses give you now, which means (+20 - 26) = -6. I'm just explaining the concept, that isn't how they actually determine the lens power because they don't know exactly what the power is of your natural lens since they can't measure it directly. (again the rest of the eye acts as a lens, so testing your vision with a chart is based on the power of the rest of the eye as well as the power of the natural lens, and they don't know how much is from what).
They determine the lens power by taking measurements of your eye and comparing them to measurements of other people's eyes and the IOL power that worked for them. It isn't an exact process, it is based on statistics, and although it works well for most people, for those with high prescriptions there is a greater chance of the IOL power being off a bit. So even if they do find a lens they hope will give you perfect vision, there is some chance it might be off a bit. It seems better to risk the lens power being off in the direction of being a bit myopic rather than hyperopic since myopia is easier to correct using a laser if you wish to do so.
If you are left -6 myopic after cataract surgery, you could consider either laser correction or an ICL (implantable collamer lens, or sometimes called an implantable contact lens), though surgeons disagree over the risks of an ICL, the doctor here seems skeptical of them, but others think they are a good option so its something you'd wish to research carefully if you discover you need further correction after surgery.
As the doctor mentioned, its likely good to check around to see if another surgeon can get a lens that will come closer to correcting your vision entirely.
1 Comments
Some high myopes actually require no IOL power 0.00 to leave them plano (0.00) or slightly myopic. In the days when IOLs were much more restricted in power and number of companies that made them sometimes NO IOL was put in the eye and it worked fine for this small subset of people. Subsequently it was shown in controlled studies that putting an IOL in with 0.00 power was a better option when they became available as it stabilized the inside of the eye and reduce the risk of retinal detachment and posterior capsular opacification. Several companies now make low power and no power IOLs.
First read this very carefully: http://www.medhelp.org/user_journals/show/1648102/Consider-ALL-the-Options-Before-Your-Cataract-Surgery-Working-Through-Whats-Best-For-You ;
Then see at least two more cataract surgeons. Look for one that specializes in cornea/refractive/cataract/Intraocular lens. There are a number of IOL companies that have special order series so that you could have a post operative refractive error of -1.50 to plano after surgery. You need to see several surgeons so that you get a better answer than getting a IOL that leaves you -6.00 Ideally you would not be any more myopic than -2.50 if you chose mini-monofocal near bias.
Then see at least two more cataract surgeons. Look for one that specializes in cornea/refractive/cataract/Intraocular lens. There are a number of IOL companies that have special order series so that you could have a post operative refractive error of -1.50 to plano after surgery. You need to see several surgeons so that you get a better answer than getting a IOL that leaves you -6.00 Ideally you would not be any more myopic than -2.50 if you chose mini-monofocal near bias.
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