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Medical Forum / General / Vision / November 2007Toric Silicon Hydrogels?
Which brands of silicon hydrogels are available as toric lenses? If more than one, what are the differences between them? > Which brands of silicon hydrogels are available as toric lenses? If more > than one, what are the differences between them? The two that I know of are: Purevision Toric and Acuvue Advance For Astigmatism. I have used both. I recently switched from Acuvue Advance For Astigmatism to Purevision Toric. I found the Acuvue Advance seemed to retain deposits and were much less comfortable after about ten days. While the Purevision are thicker and take a bit of getting used to, I find them extremely comfortable and easy to handle. For me, they last a full 30 days while maintaining comfort. At least, that has been my experience. > > Which brands of silicon hydrogels are available as toric lenses? If more > > than one, what are the differences between them? [quoted text clipped - 10 lines] > handle. For me, they last a full 30 days while maintaining > comfort. At least, that has been my experience. I think Colin summed it up pretty well. Both lenses are pretty good and are an excellent addition to my toric fitting sets. I trial most of my toric patients in one of these lenses. In contrast: 1. Av Adv Astig-- hard to handle due to soft "low modulus" nature of the plastic; tend to get deposits quickly in many people; considered to be quite comfortable by most all wearers; very little rotation and easy to fit on patients; would be the obvious winner except for the first two points. 2. PV Toric-- smaller diameter plus tougher "high modulus" plastic that folds less and is easier to handle; gets deposits much less than Av Adv does; not considered as comfortable due to the high modulus nature of the lens; this lens is preferable for 1st time wearers since it's easy to insert and remove them but their comfort usually isn't as good as AV Adv is probably due to the high modulus plastic. If a patient habitually takes out their lenses at night, and doesn't has significant problems with contact lens comfort, then there are many other HEMA-based torics that work quite well also. Thanks for all the info. I have been wearing N&D on both eyes, monovision. At my eye checkup this week, the eye doc suggested trying a toric lens on the right eye, to help with the astigmatism on that eye. He gave me the Acuvue Advance one. I was surprised at how much better my distance vision is with the toric lens. (I didn't know I was so astigmatic.) I also find the lens comfortable, no different from the N&D in my left eye. However, I notice the right eye is red, after wearing the Advance in it for just a couple days (including sleeping in it). (I am used to sleeping in the N&Ds.) Also, the lens fell out this morning, while rubbing the eye. Anyone know why the eye might turn red with the Advance (with no discomfort), and why it would fall out? My eye doc didn't mention the Purevision toric as an alternative, but perhaps I should ask him if I can try that too. Which of the two has the higher dK? Thanks again. >Thanks for all the info. > [quoted text clipped - 18 lines] > >Thanks again. Acuvue Advance are not designed for extended wear. It's dK/t is 85.7, higher than any other non-extended wear lens I know of, so it's probably OK for a few days, but they don't recommend it. PureVision's dK/t is 110. If you find the N&D lenses comfortable, you will likely have no problem with PureVision. They felt identical to me (horrible - it's not the modulus, but the sharp edges, versus the very smooth edges of Acuvue lenses) when I tried them. And unlike N&D, which has a very small optical zone, PV lenses provide excellent night vision.  Signature- Mike Ignore the Python in me to send e-mail. >> Thanks for all the info. >> [quoted text clipped - 23 lines] > probably OK for a few days, but they don't recommend it. PureVision's > dK/t is 110. With the Acuvue, if I closed my eyes for even a few minutes, they felt quite sticky afterwards. > If you find the N&D lenses comfortable, you will likely have no > problem with PureVision. They felt identical to me (horrible - it's > not the modulus, but the sharp edges, versus the very smooth edges of > Acuvue lenses) when I tried them. And unlike N&D, which has a very > small optical zone, PV lenses provide excellent night vision. I find the PureVision Toric extremely comfortable even with the sharp edges, more so than the Acuvue, but I find on occasion with the Purevision regular contact in my other eye, I do notice the sharpness. Night vision is a big plus for the Purevision. I am using monovision, so might be different, but couldn't stand the Acuvue at night when under street lights, as I had serious halo effect. This is not a problem with Purevision. In fact, I get better vision with Purevision with monovision than I do with either regular contacts or glasses. However, I have had cornea problems in the past, so the Purevision has a bit of a bandage effect for me, more so than with the Acuvue. However, other's mileage may vary. Colin > Acuvue Advance are not designed for extended wear. It's dK/t is 85.7, > higher than any other non-extended wear lens I know of, so it's > probably OK for a few days, but they don't recommend it. PureVision's > dK/t is 110. I wonder why my optometrist, knowing that I wear N&D as EW, gave me the Advance rather than Purevision? (He may not have had the Purevision toric in stock, but he could certainly have ordered one.) He told me the Advance was EW, and didn't even mention Purevision. I'll have to ask him to try the Purevision. Thanks for the info. > Acuvue Advance are not designed for extended wear. It's dK/t is 85.7, > higher than any other non-extended wear lens I know of, so it's > probably OK for a few days, but they don't recommend it. PureVision's > dK/t is 110. Strange. I just called the optometrist office, and spoke directly with him, and asked about the Purevision. He said that the Advance is also for extended wear, and also said that it has a much higher dK than the Purevision lens. I couldn't argue with him about it, but told him I would like to try the Purevision anyhow. He said OK, he would order me one to try. Perhaps next year though, I should go to a different eye doc. It doesn't seem like he is very knowledgeable. > Strange. I just called the optometrist office, and spoke directly with > him, and asked about the Purevision. He said that the Advance is also for > extended wear, and also said that it has a much higher dK than the > Purevision lens. Both wrong, of course but it isn't rare for doctors to allow overnight wear with Advance. The more primitive Acuvue (AV2) is still FDA-approved for overnight and it is significantly LESS permeable than AV Advance, and there are others still approved, like Biomedics 38, that are even "worse". Permeability isn't the be-all-end-all of overnight wear, but Advance is significantly better than older lenses. We don't always know why a company doesn't submit a lens for the "overnight" FDA labeling. Sometimes it's because the approval process is expensive when they have another lens in the pipeline. I'm looking forward to a toric Oasys. Some day. My rep didn't know about one but she didn't act worried when I told her some people sleep in Advance. -MT Is there a chart somewhere on the net that shows the dK of all the silicone hydrogel materials? Thanks for the info. >Is there a chart somewhere on the net that shows the dK of all the silicone >hydrogel materials? > >Thanks for the info. There used to be a free search function at www.eyedock.com, but it's now subscription-only. But if you search for the lens name and "dk" on Google, you'll usually find a figure. Just check a few different results to reduce the odds of you seeing a typo or just plain incorrect figure. Signature- Mike Ignore the Python in me to send e-mail. > > Strange. I just called the optometrist office, and spoke directly with > > him, and asked about the Purevision. He said that the Advance is also for [quoted text clipped - 15 lines] > > -MT i believe that the expense of FDA approval is one factor for why some companies don't seek out extended wear certification for products that could almost certainly attain it, but more likely its good ol' product positioning. CIBA, for example, could almost certainly get EW certification for 02 Optix but why undercut their existing customer base who already pays 3 times more for Focus N&D? Similarly Vistakon probably tries to position Oasys as their "EW-preferred" lens so as to justify why someone should pay so much extra for it. I think marketing has a lot to do with EW certification in recent years. my Vistakon rep has "hinted" that the entire AV Adv toric line will likely be "updated" within the next year or so with a more Oasys-like material. I think Vistakon is sensitive to the problems that Advance has with increased deposits in many patients. I am one of the guilty eye docs who, under certain circumstances, will put people into Av Advance for EW. I do that for patients who are obvious CL abusers who will sleep in whatever lens they buy and will only buy inexpensive ones. I guess I figure I'd rather have them sleeping in Advance (or preferably 02 Optix) than in polymacon or some other old plastic like they currently use. it's picking the lesser of two evils I guess. > I am one of the guilty eye docs who, under certain circumstances, will > put people into Av Advance for EW. I do that for patients who are [quoted text clipped - 3 lines] > other old plastic like they currently use. it's picking the lesser of > two evils I guess. But why choose between those two choices? Why not recommend that they get N&D, Purevision, etc., if they want EW? >> I am one of the guilty eye docs who, under certain circumstances, will >> put people into Av Advance for EW. I do that for patients who are [quoted text clipped - 6 lines] >But why choose between those two choices? Why not recommend that they get >N&D, Purevision, etc., if they want EW? Perhaps his patients, like me, find those lenses incredibly uncomfortable. My Oasys disappear in my eyes after a few seconds when I put them in. N&D and PureVision were still horrible after more than an hour, so I gave up trying the latter (the former I gave up as soon as I saw they were incapable of focusing a star image at night, due to the small optical zone). I expect there are people for any given lens who can't stand the feel of it. Signature- Mike Ignore the Python in me to send e-mail. >>But why choose between those two choices? Why not recommend that they get >>N&D, Purevision, etc., if they want EW? [quoted text clipped - 8 lines] > I expect there are people for any given lens who can't stand the feel > of it. I guess, that since before I wore the N&Ds I was wearing RGPs for thirty years, the N&Ds felt very comfortable to me. I would like to try the new Biofinity lenses, however, as they are supposed to be so comfortable. (In my left eye, which doesn't need toric.) (They are approved for thirty days wear in other countries, but have not yet gone through that process here in the USA, (Why does our FDA always take longer to test these things?) so they are listed in the USA for now as being for daily wear.) Have you considered Biofinity? Oasys is approved for EW, correct? > Oasys is approved for EW, correct? Yes, and about half the price of N&D. -MT >> Oasys is approved for EW, correct? > > Yes, and about half the price of N&D. > > -MT When you discuss price, do you mean price per lens, or price per month? With N&D you change lenses every month, according to the recommended schedule. Are Oasys lenses also changed monthly? If they are changed every two weeks, and the lenses cost twice as much, the monthly cost is the same. I'm sure the manufacturers set the price per lens, according to the replacement schedule. Is there really such a difference in the overall cost, of the different SH brands? I usually buy N&Ds online, and the price is usually about $50 per box of 6. That is a 6 month supply, for one eye. So, a yearly supply, for both eyes, costs around $200. Is the yearly cost of Advance or Oasys a lot less? > costs around $200. Is the yearly cost of Advance or Oasys a lot less? Not if Oasys are replaced exactly as the manufacturer recommends. You're right about that. -MT >> costs around $200. Is the yearly cost of Advance or Oasys a lot less? > > Not if Oasys are replaced exactly as the manufacturer recommends. You're > right about that. > > -MT How often is it recommended that Oasys be changed? Two weeks? Are you suggesting that many users do not replace lenses as the manufacturer recommends, but keep the lenses longer? Is there really a difference between lenses that indicate that some can be kept longer than others (some for only one day, others for a month, others in between), or is the designation of the wear length of lenses made entirely for economic reasons? (It's clear though, that they are going to charge considerably more for a lens changed once per month, than for one changed every day.If not, they would lose a lot of money on the monthly lenses.) > How often is it recommended that Oasys be changed? Two weeks? Yes, but that's two weeks of overnight wear. I don't have many patients wearing lenses that long, so I sometimes forget. When lenses are removed at night, they are 6 to 20 times safer, so I confess that I tolerate one-month replacement in Oasys when they aren't worn overnight. I recommend 2-week replacement for overnight wear, but I'm pretty sure half of them go beyond 2 weeks. > Are you suggesting that many users do not replace lenses as the > manufacturer recommends, but keep the lenses longer? Nah. Never happens. :) If you aren't sleeping in them and they still feel new at 2 weeks, it's hard to say they MUST be discarded. > Is there really a difference between lenses that indicate that some can be > kept longer than others (some for only one day, others for a month, others > in between), or is the designation of the wear length of lenses made > entirely for economic reasons? It's the manufacturer's decision to push for one approval or another. Each approval must be supported by large-scale trials at the manufacturer's expense. I don't know the process very well. I do know that people will pay $10/gal for water when you call it "bottled." -MT >>> Oasys is approved for EW, correct? >> [quoted text clipped - 7 lines] >schedule. Are Oasys lenses also changed monthly? If they are changed every >two weeks, and the lenses cost twice as much, the monthly cost is the same. Where I get my lenses (lens.com), Oasys are currently $18.24 per box of six lenses when you buy eight boxes (i.e. 48 weeks worth if you replace them every two weeks). N&D are $42.99 per box if you buy at least four boxes. If you do the math, and use the "official" lifetime of the lens, that's about $0.43/day for Oasys, and $0.48/day for N&D. That's not that big a difference, so you might call Oasys a premium lens as well, but worth it in my opinion. PureVision comes out to $0.34/day, feels the same as N&D, and has good night vision. Signature- Mike Ignore the Python in me to send e-mail. > <p.clar...@gmail.com> wrote in message > [quoted text clipped - 10 lines] > But why choose between those two choices? Why not recommend that they get > N&D, Purevision, etc., if they want EW? Price. Focus N&D pricing is exorbitant. Purevision is better but still much higher than lenses with similar Dks. > Price. Focus N&D pricing is exorbitant. Purevision is better but > still much higher than lenses with similar Dks. What is the pricing like on Biofinity, the new monthly lens by Coopervision? They are not even available online, so I assume one can only get them (in the U.S., at least) through eye docs. I would guess more expensive than N&D and Purevision. How much for a six lens box? Also, those are currently only rated for daily wear in the US, although they have been approved for 30 day continuous wear in other countries. Are docs recommending their use for EW here anyhow, since they have been approved for it in other countries? |
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