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Medical Forum / General / Vision / November 2005Prism Needed
Hi, Just been to the optician today... they want me to pay £58 to have some new lenses made, when my old glasses (OK, they were without PRISM - dunno if that makes a difference), my old glasses, frames included cost £39.... Anyhow, you may remember my fevered postings regarding how text does not seem to be staying on the paper etc,even though the LCD monitor looks fine... Im slightly longsighted by the way. Anyhow, apparently there is a convergence issues, one eye is trying to converge more than it needs to or something... that's the way it was explained to me, and reckon there's about between "four to eight" whatever of PRISM. Of course, Im not sure whether those will help at home, or whether I'll need to use them all the time as there's a prism... Now, at the test, they were using something with red lines, and seeing if it would pass through the white dot... Horizontal, was mostly fine, but the vertical line kept bouncing around and I had extreme difficulty with it passing through the dot. So on to the next test, something with the word OXO and a green line, either vertical or horizontal. The horizontal one was perfect: o ==x== o The green bar lined up perfectly with the x. But on the vertical line... well, it was very bizarre, the two lines were not lining up with each other, but both of them were lining up with the X! I know that sounds bizarre, but that's how it appeared. But the top line gave the appearance that it was bouncing around most of all, I couldn't get the the thing to sit still! So... advice... you ever hear anything like this? How the lines line up with the X, so they should line up with each other, but they don't? How they bounce around (that can't be right)??? The PRISM, will it really help for close up work? Why does it only happen at work, or, well, at the opticians? Will I need them for driving? And do PRISM lenses cost more? Thanks Simon Dear Simon, Answering bits in turn: > Hi, > [quoted text clipped - 18 lines] > Horizontal, was mostly fine, but the vertical line kept bouncing around > and I had extreme difficulty with it passing through the dot. I presume here you mean with the red line vertical it was moving around. The test sounds like a Maddox Rod Test. This is used to indicate ocualr muscle imbalance at distance. The two eyes are not aligning.There is a problem with this test in that it is a 'dissociation test' (the two eyes are effectively uncoupled) and often the answer does not truely correlate with the real world.I prefer using Mallet Distance Fixation Diparity Test. > So on to the next test, something with the word OXO and a green line, > either vertical or horizontal. [quoted text clipped - 11 lines] > appearance that it was bouncing around most of all, I couldn't get the > the thing to sit still! This test is Mallet Near Fixation Disparity Test( Mallet being the name of the test's designer). Again it is desinged to show up ocular muscle imbalance, this time at your reading distance (usually assumed to be 33cm but the advantage of the test is that it does not have to be used at that distance.) The test actually measures 'retinal slip' In effect the two eyes are not quite looking at the same point on any object of regard. By using aligning prism you can then correct the 'retinal slip' and by doing so eliminate any problems with near vision. > So... advice... you ever hear anything like this? How the lines line up > with the X, so they should line up with each other, but they don't? How > they bounce around (that can't be right)??? The fact that the lines are bouncing round shows that you have poor fusional lock at near. This is the advantage of the Mallet tests in that because they use polarised visors to ensure that each bar is only represented in one eye. The letters OXO act as a fusional lock and ensure that the eyes are looking at the same point on the test. >The PRISM, will it really > help for close up work? Why does it only happen at >work, or, well, at the opticians? At work is where you are getting the problems and the opticians - thats where the tests demonstrate the problem >Will I need them for driving? Depends on the degree of the problem. Some problems with ocular muscle balance only occur at near, some only occur at distance and some have different degrees at both. >And do PRISM lenses cost more? The big question depends on the prism power required. Under 3 then there should not be a cost over 3 the yes there will be an additional cost. > Thanks > Simon Hope this all helps Ian Hodgson - Isle of Man > Dear Simon, > [quoted text clipped - 11 lines] > I presume here you mean with the red line vertical it was moving > around. Yes. > The test sounds like a Maddox Rod Test. This is used to > indicate ocualr muscle imbalance at distance. The two eyes are not > aligning.There is a problem with this test in that it is a > 'dissociation test' (the two eyes are effectively uncoupled) and > often the answer does not truely correlate with the real world.I > prefer using Mallet Distance Fixation Diparity Test. I presume that came next... >> So on to the next test, something with the word OXO and a green >> line, either vertical or horizontal. >> >> The horizontal one was perfect: >> >> o ==x== o Hrm... Bloody Mozilla... it would have to rewrap this!! >> The green bar lined up perfectly with the x. But on the vertical >> line... well, it was very bizarre, the two lines were not lining up [quoted text clipped - 5 lines] > This test is Mallet Near Fixation Disparity Test( Mallet being the > name of the test's designer). Just been reading about this... quite interesting... havent seen anything about lines lining up with X's, but then, it's not supposed to from what I've read, the lines are supposed to line up with each other, in that case, the top line, was way over to the left. or maybe it was the bottom line way over to the right? I know the red line test thingy, the red line was way off to the right of the dot... I had the red line producing lens in the right eye on that test... > Again it is desinged to show up ocular > muscle imbalance, this time at your reading distance (usually assumed [quoted text clipped - 4 lines] > 'retinal slip' and by doing so eliminate any problems with near > vision. So I presume the two tests correlated with each other then in showing the same, what is it, ocular muscle imbalance? >> So... advice... you ever hear anything like this? How the lines >> line up with the X, so they should line up with each other, but [quoted text clipped - 5 lines] > only represented in one eye. The letters OXO act as a fusional lock > and ensure that the eyes are looking at the same point on the test. Does it mean anything worse than needing prism if I couldn't achieve that fusional lock? I must admit over recent weeks, I've noticed that my left eye is considerably weaker than my right eye, and it feels like Im doing a lot more seeing out of my right eye... That's worrying me slightly... And I am worried as to why I've only just had this phenomenon now, and it's coincided with me taking three weeks off sick after some toenail surgery. >> The PRISM, will it really help for close up work? Why does it only >> happen at >work, or, well, at [quoted text clipped - 3 lines] > At work is where you are getting the problems and the opticians - > thats where the tests demonstrate the problem Yes, but I mean, I don't really feel like I have the same sort of disparity at home, with my regular glasses being just fine in focusing the print. If needs be. Is there anything at all which hints that this problem might be more noticable when it's darker, or under fluorescent lights? >> Will I need them for driving? > > Depends on the degree of the problem. Some problems with ocular > muscle balance only occur at near, some only occur at distance and > some have different degrees at both. I only notice most of my problems at close up... although I've noticed the strange writing appearance of smudgy smearness anti alias fuzziness on the dry wipe board at work which is about, ooh, seven feet away from me. But driving home, Im fine... though my iPod will be a little fuzzy to read... until the next day... it will appear fine... I would wear these glasses for driving, but I just can't see the distance in them properly.... I know that's a normal phenomenon with longsightedness and having such reading glasses, but should I be letting my eyes readjust and readapt or just use the glasses solely for close up? and then I guess the same applies to the prism ones.... Should I be looking out for two pairs of glasses, one for my astigmatism and reading, and one for the astigmatism, reading, and prism? >> And do PRISM lenses cost more? > > The big question depends on the prism power required. Under 3 then > there should not be a cost over 3 the yes there will be an additional > cost. Yeah... it's about four to eight apparently... so I presume an additonal cost... but I have phoned specsavers, and with their "clear price", they reckon they can do prism glasses for £39 including the frame, or £39 in the exisitng glasses... sounds too good to be true. Question is, do I save myself £20, or keep at the same optician who did the test. and why don't specsavers do the tests for prism as a matter of course? Thanks Simon Why are you whinging about paying for new lenses? If you need them, they will be worth it. For 39 pound, you will get a frame that is a piece of sh.t with crap lenses. If that is what you want, that is what you get. Why don't specsavers do prism tests? Probably accounts for the quality of their opticians. They are as good as the quality of their glasses. \ Do yourself a favour, determine who you want to look after you and get the new glasses. dr grant > Why are you whinging about paying for new lenses? If you need them, > they will be worth it. Oh christ, not another one I need to show my bank balance accounts to... look, my finances are none of your goddamn business... But maybe when Im a bit more financially stable, I will go and pay over the odds for glasses... > For 39 pound, you will get a frame that is a piece of sh.t with crap > lenses. If that is what you want, that is what you get. Yes. And I did buy a frame that was a bit rough around the edges but you know what, it did it's job. I didn't know whether it would, I didn't know if that would solve my problems six months ago, but it did. And it only cost me £39 and was semi good looking... I know a friend who spent £200 on the highest quality rimless tinted coated UV protected lenses.... but hey.... they do the same job and at the moment, value for money is very important to me. Cya Simon > > Why are you whinging about paying for new lenses? If you need them, > > they will be worth it. [quoted text clipped - 3 lines] > a bit more financially stable, I will go and pay over the odds for > glasses... Some of us value our vision quite highly. My first retinal detachment cost almost US$10,000 to fix. It was worth it. The alternative was going blind in that eye. > > For 39 pound, you will get a frame that is a piece of sh.t with crap > > lenses. If that is what you want, that is what you get. I don't understand the frame thing. A little plastic, or a little metal. I was very heavily dependent on glasses for a long time. I'm now heavily dependent on reading glasses, but they are OTC. I pay US$18.99 at Costco for a three pack. I get three pair of lenses and three frames. They work just great.  SignatureDan Abel dabel@sonic.net Petaluma, California, USA There are several aspects to the frame thing. First, quality. Many stores are happy to sell goods that are made from inferior parts. The metals corrode, the welds are done badly, the hinges are cheap: in essence, they are not made to last, they are made down to a price. Second is the appearance: cheap frames look cheap. If that's how you want to look, so be it, but not for me. I want my customers coming back and selling cheap ugly glasses isn't what will do it. Thirdly is the margin. Specsavers may be happy to sell glasses for next to nothing, but they will also be paying low wages and provide poor service and support. I just spent over $100,000.00 on 2 new cameras and a visual field screener. How many pairs of $39.00 specs do I need to sell to cover the lease on these??? Ultimately, you get what you pay for. If Simon wants to look after him, Specsavers isn't the place. But Simon wants the best of both worlds. He wants an optometrist to spend hours working out the correct prescription, then go and buy cheap glasses elsewhere. How is it going to go when his glasses are not quite right and he needs to go back to the optometrist for a recheck, then go back to specsavers for and change in script??? dr grant > There are several aspects to the frame thing. First, quality. Many > stores are happy to sell goods that are made from inferior parts. The > metals corrode, the welds are done badly, the hinges are cheap: in > essence, they are not made to last, they are made down to a price. Good. As I expect my vision to change over the course of a year, Im not going to use my glasses 24/7 maybe a few hours at work or as needed (it's only the past couple of weeks in six months, that I've actually needed to use them), so Im not too willing right now to spend a large sum of money on fancy frames... especially if my vision changes, I just go and get my eyes rechecked, and get a new pair made up. There was also a reason for me buying a cheap pair in the first place, in that my vision was like +.75 in one eye, +.5 in the other, with a slight astigmatism. It was debatable whether I'd actually get any benefit... but I have. From this £39 pair. > Second is the appearance: cheap frames look cheap. If that's how you > want to look, so be it, but not for me. I want my customers coming > back and selling cheap ugly glasses isn't what will do it. Ahh. You must work in the south of england. There are a lot of people in the rest of the UK who might not be able to afford the latest designer glasses, so knowing I can get a pair of glasses that work, and relatively cheaply, is always going to be a factor for me. I can trust the optician to give me their honest opinion and not try to sell me a pair of glasses without giving me the results as I walk out the door... Price, Value for Money, Trust. Those do it for me. But everyone I've spoke to so far say that these particular glasses are pretty good... even the indepedent commented how they're really nice frames... I said "Yeah, I got them for £40" > Thirdly is the margin. Specsavers may be happy to sell glasses for > next to nothing, but they will also be paying low wages and provide > poor service and support. I just spent over $100,000.00 on 2 new > cameras and a visual field screener. How many pairs of $39.00 specs > do I need to sell to cover the lease on these??? Put in the conversion ratio if you're working in dollars... Then the lowest price for Specsavers is $39 * 1.8 = $70. My local specsavers just had installed all the latest computer technical wizardry and performed a more complete array of tests including glaucoma and something looking at a balloon, which is something the smaller optician never did. Their service and support has always been excellent too for me, even doing the usual writing letters for my GP for investigation of various issues. > Ultimately, you get what you pay for. If Simon wants to look after > him, Specsavers isn't the place. But Simon wants the best of both > worlds. He wants an optometrist to spend hours working out the > correct prescription, then go and buy cheap glasses elsewhere. So far, I've had a better experience at Specsavers... I was never hassled into getting glasses, I was given a prescription as I walked out the door with time to think, and the opportunity to go elsewhere, I wasn't given pressure selling tactics, I was given the opportunity to ask questions... the only thing the independent did differently, was that they actually performed less tests, but included one other one which Im sure is probably available on the computer system at specsavers somewhere... Dunno if you're in the UK, as far as I know, we pay £20 for an eye test, and I think that is fixed across all opticians, and we should be under no obligation to buy glasses from any particular place. Perhaps that's why it's not so good using an independent, because they'll try and force you to buy a pair of expensive glasses so they can increase their profit margins. It's not that I necessarily want to buy a useless pair of glasses, or a cheap pair of glasses, I just want to know if that £60 lens, is the same as the £40 lens at Specsavers! I think it would be. > How is > it going to go when his glasses are not quite right and he needs to > go back to the optometrist for a recheck, then go back to specsavers > for and change in script??? To be fair, Specsavers are my usual optician. They're an optician I trust, I only went to the independent after advice from my GP. The recheck issue is something I wasn't aware of. I didn't realise if they've misdiagnosed your prescription, that you're necessarily entitled to a change. But yes, that's a good reason for me staying where I am then... Cya Simon >>> Why are you whinging about paying for new lenses? If you need >>> them, they will be worth it. [quoted text clipped - 7 lines] > detachment cost almost US$10,000 to fix. It was worth it. The > alternative was going blind in that eye. Oh don't get me wrong... there are priorities with everything in life... and if I had any kind of medical issue that required money, that would be my first priority... but, here, Im just talking about a pair of what would essentially be reading glasses, that could work probably just as well as a £200 pair, the only difference is the frame isn't designer, and I don't have fancy tints and lens options, but if they work then I would consider spending more at a later time when it becomes more necessary to use them longer than a couple of hours a day. Also there's an issue is that the smaller independant retailers probably aren't as cheap as some of the more well known chain opticians... and frankly, the eye test there included more tests... it just didn't include the fixation disparity test... probably because six months ago, I didn't have the symptoms. All Im saying is, why spend £60 for something you can get for £20? Though if Im going to be getting something of higher quality... then I would pay it. Also the issue for me, with an underactive thyroid, I don't particularly want to spend exorborant sums of money for an eye problem that might very well just be temporary. >>> For 39 pound, you will get a frame that is a piece of sh.t with >>> crap lenses. If that is what you want, that is what you get. [quoted text clipped - 4 lines] > US$18.99 at Costco for a three pack. I get three pair of lenses and > three frames. They work just great. That's it exactly... why spend £200 on something you could get for £39... There's even a factory outlet store where I live offering glasses for about £20... And who says that the £60 lenses are of higher quality than the £40 lenses! Cya Simon Simon, 'Lots Snipped' and trying to follow several further posts 1) Mallet distance test uses red bars and OXO 2) Ideally it should be the two bars which are out of alignment with just a single X. By your description the two eyes are dissociating with the disruption caused by the polarised visor. This indicates that you are having severe difficulty in fusing the two images,one from each eye, into one. > So I presume the two tests correlated with each other then in showing > the same, what is it, ocular muscle imbalance? Corrolation between distance and near tests is not direct as some people have distance problems and others have near problems, some have both, and sometimes the amount varies between distance and near. > Yes, but I mean, I don't really feel like I have the same sort of > disparity at home, with my regular glasses being just fine in focusing > the print. If needs be. Problems at work may be occuring because the amount of close work you are doing is stressing the visual system. At the weekend or in the evening the may not be the same amount of visual stress. > Is there anything at all which hints that this problem might be more > noticable when it's darker, or under fluorescent lights? It is possible the fluorescent light may be exacerbating the problems, due to the fact that the lights flicker at 50Hz. Whilst not consciously visible it can be unconsciously visible. > and why don't specsavers do the tests for prism as a matter of course? They should at the very least distance and near Mallett (or similar) should be part of the routine exam. Regards Ian Hodgson - Isle of Man > Simon, > [quoted text clipped - 7 lines] > that you are having severe difficulty in fusing the two images,one > from each eye, into one. A severe problem? So I gather Im overcoming the issues so that I don't notice it, but would benefit from prism lenses then? >> Yes, but I mean, I don't really feel like I have the same sort of >> disparity at home, with my regular glasses being just fine in [quoted text clipped - 3 lines] > you are doing is stressing the visual system. At the weekend or in > the evening the may not be the same amount of visual stress. That might explain then why there is still a period of "visual" stress after work for a couple of hours, and then none in the morning, I guess. I've just returned to work after the weekend, and after having had my medication for hypothyroidism increased to 150mcg. I don't notice the same issues anymore while looking at paper, though it is blurry, I can fix this with my existing glasses. I am concerned therefore whether this fixation disparity is linked in any way to my underactive thyroid, where I learned from my GP that actually my TSH has jumped from 2.6 to at least over range (ie 5.5) just in the past month.... Now Im on 150 mcg of thyroxine, things seem to be getting better. I am curious therefore if there is a possible link, and therefore whether I should be getting prism glasses. Though maybe if I got them and just wore them when I felt eye strain that would be the best option? >> Is there anything at all which hints that this problem might be >> more noticable when it's darker, or under fluorescent lights? > > It is possible the fluorescent light may be exacerbating the > problems, due to the fact that the lights flicker at 50Hz. Whilst not > consciously visible it can be unconsciously visible. I have always had problems with fluorescent lighting. I find the light highly uncomfortable to work in and has always caused me eye problems. >> and why don't specsavers do the tests for prism as a matter of >> course? > > They should at the very least distance and near Mallett (or similar) > should be part of the routine exam. I don't recall anything like that sadly. Maybe I need to request it. Thanks for the advice. Simon Simon, Give the below my best suggestion, at long range, would be try and get your thyroid problems stabilised before anything else and then get a re-exam.General Health problems could be the cause. Regards Ian Hodgson - Isle of Man > I've just returned to work after the weekend, and after having had my > medication for hypothyroidism increased to 150mcg. I don't notice the [quoted text clipped - 7 lines] > getting better. I am curious therefore if there is a possible link, and > therefore whether I should be getting prism glasses. One further question, does strabismus = fixation disparity? The thing that got me is that those lines in the test kept bouncing around... will a PRISM lens necessarily help that??? (or is it just my mind trying to align the three elements on the Mallet test and failing? rather than trying to relax and see what's there?) I've been trying to read up on this, and don't get as much information which correlates to what I sense. And it wouldn't be too bad... but I only get this phenomenon under certain conditions, like at work, or maybe at the optometrist, and for a brief period outside of these times. It still hasn't happpened at home. Thanks Simon > One further question, does strabismus = fixation disparity? Not exactly. Think of FD as a tiny strabismus without diplopia, an angle small enough that the images are still percieved as single but yet not quite aligned on the fovea. It's measured in minutes of arc, rather than degrees or prism diopters. -MT >>One further question, does strabismus = fixation disparity? > [quoted text clipped - 4 lines] > > -MT Well if that's the case, and I am quite adament I don't have such a large strabismus, I know for a fact I don't see double (though i can do that at will as I please), why have they said I should go with "four to eight" something... in reference to prism lenses... Thanks Simon Simon, > >>One further question, does strabismus = fixation disparity? > > [quoted text clipped - 9 lines] > that at will as I please), why have they said I should go with "four to > eight" something... in reference to prism lenses... Strabismus ( aka heterotropia) is a manifest (ie apparent) squint and usually large. Fixation Disparity measures what is called a heterophoria, this is a hidden squint, or as I have stated earlier ocular muscle imbalance.Often the eyes are trying to overcome the diplopia by working extra hard. The idea behind the tests is to find out if this is happening. And give rise to convergence/divergence insufficiency. Correction of the problem is by either some form of eye exercises or spectacles using prisms. (Whilst Mike is correct in that the measurement is done in minutes of arc corrective lenses are done in prism dioptres.) The correction is usually split between the two eyes to give a better cosmetic result, but if the prism correction is low or not easily equalibly splittable then then highest prism value is placed in front of the eye exhibiting the fixation disparity. Regards Ian Hodgson - Isle of Man
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