Lecture: Practical Tips for Dispensing Spectacles: From Prescription to Perfect Fit

SARAH WASSNIG-RIGLAR: Hi, everyone, I’m just going to share my slides here. Okay. Hello, everyone. And thanks to Cybersight for having me. We’ll talk about dispensing spectacles from an optometrist’s point of view today. Most countries, and rightly so, optical dispensing requires a course. It is a regulated profession which I would be very much lost without. Today we’ll talk about common issues that need troubleshooting from the point of view of the optometrist. We’ve all been in the situation where our patient has dispensed glasses only to return a couple of days later, maybe a week or so or a month later, saying that something just isn’t quite right. So the dispensing team knock on your door books them in to see you. By the time the patient gets back to the optometrist, usually the dispensing team has done a wonderful job of checking the lens parameters, checked that the prescription is what it should be, place the frame back on the patient and make sure the pupil is going straight through the lens center. That the frame is sitting on the nose properly, that the temples have been adjusted to be straight on the face. I think one of the most common mistakes in dispensing is taking all the measurements on a brand-new frame and then adjusting the frame later on to the patient’s face. So you want to make sure you make all of those frame adjustments and make sure the frame is straight before taking any of those critical measurements. But it still happens, despite all this, my team tells me the patient says there’s still something wrong. So they may come. One of the first questions my team and I go through, especially if it’s a high prescription, is what were the heights and PDs on the previous pair of glasses that the patient was happy with. And this is particularly important with varifocals. So a little bit of an overview here of the lens marking. This is what your very focal lens looks like when it’s marked up. And when you’re ensuring you have the correct height, you want the patient looking through the distant area of the lens without fitting crosses. The best way of doing this is the same as checking your PDs, when you’re taking heights, you’re seeing directly across from the patient at the same eye level. You’re going to close one eye. Hopefully you can wink, if not, cover one eye, and get them to look at your open eye. Your going to mark on the lens where their pupil is looking through. Hopefully that corresponds exactly to where the fitting cross and the distance area is. So this dispensing case happens quite a lot, where the patient’s previous glasses in varifocals, for whatever reason, had heights that were either set a little too high or a little too low than ideal. In this case you can see the heights are set a little too high. So when this patient is wearing their varifocals, perhaps mainly in the office, the height of the old pair, when they’re looking through their lenses, they’re looking through a touch of the intermediary. And a latent height can get away with this quite easily. When they’re sitting at their computer, looking straight ahead, they’re accessing that aspect of the lens. Today we have big, giant screens, held up high, so this is handy for the patient. Now the reason they hate your new varifocals is when they look straight ahead they’re now looking through the distance area because you’ve brought the heights back down. They need to bring their chin up a little bit in order to see their desktop screen. Also they’re going to find that they really need to bring their eyes down in order to access that near area. It’s going to be a bit lower than what they’re used to. You’ve got two options here, really. And this entirely depends on the patient’s lifestyle and their needs. You can increase the height by the same amount as their old pair, or you can suggest an occupational lens where the center point of the lens is mostly dedicated to that intermediary, and then you have a touch of distance at the top of the lens. With the newer occupational lenses, you can set that top kind of distance area to be a little bit further away, up to four meters away. So it means that you can have almost like a very focus way, you have mostly intermediate and a tiny bit of distance and a little bit less normal reading. In this case we change the lens over to an occupational lens that had that sort of four-meter distance point. And that meant that they could be in board meet presentations and dip their chin down slightly to see their presentation. We often get patients coming in reporting that their varifocal is not doing the job. Varifocals, when they were first invented, they worked really well because our computer screens sat low down on the desk so when you looked over the computer screen, you were looking straight ahead and you could see in the distance, and down at the intermediate, and even further down for your reading. And now a lot of our VDU screens and desktop screens are a lot higher. This is an interesting case. We get these quite often, where a lot of patients who were previously happy with their varifocals and their VDU screen, they’re having a lot of time, a lot of effort, rather, now, particularly with their laptop and their vision is off. And the common dispensing pitfall is these patients are perhaps too tall for their add. In this case we have an expected add of plus 2 for a 58-year-old, I’m sure that sounds right, but that’s 6’5″. I don’t know about you, I have armrests, so the patient tends to sit their hands on the armrests and hold the paper quite close, regardless of sort of how tall they are. So I always assume, if someone is tall, and they’re holding the near chart at 40 centimeters, they probably in day to day life have a longer working distance. And I want to knock that add back slightly. Their face is just further away from their near work such as a laptop screen compared to someone like myself who is 5’3″. Decreasing the add, but unfortunately the best thing to do is to trial this in a trial frame. So a trial frame refraction is important, a good example of sitting at a desk with the near chart where their laptop would be, and play around with the add until they find something that’s comfortable. Unfortunately there’s no patient height formula. That would be really good if there were, though. In the case of previous single vision lenses, where the optical centers don’t match their PD, so it’s going back a little bit to checking what the previous pair of glasses were, you need to think about the prism that was induced by that decentered lens. So this is an image from an article in 20/20 Magazine. When we’re dispensing prism, we can intentionally beef into the lens in order to create the prism that we want. I’m not going to go into prism today in depth because I actually think it serves a lecture to itself. A patient who has come in with decentered lenses, what impact will that have on binocular systems, taking into account the type of lens they have, whether it’s positive or negative. Now in a new pair of glasses, you’ve got the lens centered in the middle of their visual axis, now how does that impact the binocular system and are they having any issues because of that difference? So I have a bit of a cold, sorry, I’m going to take a sip. So in case 4, all the measurements check out. We’re happy with how the lens is sitting. Is there something wrong with the refraction? So we come across a case of two different adds or loss. These lenses usually come back with a latent who is going into varifocals for the first time, something just doesn’t feel right. Up until now they’ve been prescribed single vision near which have worked really great, but the varifocals is just not working. The main point in this case here is accommodation is even in both eyes. If you’ve got uneven adds, then you’ve actually got your distance prescription a little bit off. So when you test a latent monoculi, you’ve tested one, after a little while, by testing this one you’ve managed to relax the system a little bit so this one is a little bit more relaxed when you test it. So at the end of the testing of a latent, always binocular balance. You’ve got a few ways of doing this. I find the Humpheries binocular balance the easiest way to do this. This is going to be fuzzy, you say to the patient, this is going to be clear, otherwise they’ll panic and say I can’t see now. And when I add this lens into your add a plus or two five, is it clearer, the same, or does it make it a little bit worse? If you add it in and say, oh, yes, that’s much better, and add another plus or two five, you know you’ve undercorrected that hyper in that eye. You keep going and they say that’s worse, and then you want to knock that back. Then you want to switch to the other eye and do the same, when I add the plus or two five, is it a little bit better, is it a little bit worse, or the same? I’ll mention this in a little moment, I do tend to sort of undercorrect them in the distance slightly. I would rather give them a slightly higher add then fully correct in the distance, because mainly they’re not going to like it and I don’t want them coming back again. So I find another nifty thing to do is whilst you’re checking your near add, when you’ve got their glasses on and they say yes, that looks really, really clear, and you cover the one eye, say this is your left, this is your right, does one seem a little bit clearer than the other. And then say, look, my right eye is a little bit clear, so we’re going to pop a plus 025 in the left, and they say that’s about equal. And then you know you’ve undercorrected that left eye in the distance by about a plus 025. So rather than keeping those uneven adds, you want to make sure that actually you continue balancing in the distance until you know you’re nice and happy with the distance prescription. So for example, this patient here is most likely plus 175 in the right and a plus 075 in the left. I present this in the distance and compare the two eyes, asking if each one is clearer than the other, making sure they’re comfortable. And then for comfort I might just knock it box an 025 in both eyes so I have a plus 150 in the right eye and a plus 050 in the left eye and then I would adjust the reading add to a plus 125. This also makes more sense, considering they’re 48, so it all kind of fits together a little bit better. There are times when you see a patient who has two different adds than the classic one, if they’ve had cataract surgery in one eye. Here we have a young presbyopic patient. They left the left eye as it was because they were so young. So if we’re prescribing reading glasses for this patient, we would expect an add without plus 225, 250, depending on their working distance, their height, et cetera, in the right eye, to do the accommodative work of that plastic IOL lens. Speaking of accommodation, this brings us to case 5:00. We have a 37-year-old carpenter. He comes in needing to replace his clear lenses. He’s happy with his sunglasses, he’s got 2:00 pairs of glasses, the clear pair from 2018, the sunglasses pair from 2020. And he’s happy with his vision in both pairs, he’s not having any issues, he just wants to update his frame, scratched lenses. He’s worn glasses since childhood. We’ve added an antifatigue add. We assume he’s probably got some of his hyperopia and undercorrected there or uncorrected. So he comes in seeing me and he hates his new glasses, he’s finding the sides really frustrating and they give him a whopping headache by the end of the day. My first question is, is accommodation balanced? Just like our previous patient, I do a Humpheries binocular balance and I land with this refraction up here. So it’s a little bit off but not too far off, it’s okay, it’s fine. But we’re going to balance it out anyway. My next thought is what is his actual prescription and how much are we actually undercorrecting him by. I do retinopathy and discover we’ve uncorrected him by a plus 125. My last thought is, does he need an add at this stage. He should have enough accommodative power at 37 to cope with an undercorrect of plus 125. So I do retinoscopy and discover that MEM is about a plus 050 lag, which is a perfect place for a — a perfect place for the accommodation to be sitting. In this case we remove the antifatigue aspect of his lens and put him back into single distance vision of his lens. For those thinking, remind me again what MEM is, MEM, we’re using an retinoscope. We attach it to words that are nonsensical and don’t make a sense. Whilst they’re reading, we’re checking the level of their accommodation, so where they’re accommodation is relative to the plane of the retinoscope. This is something I believe we’ve covered already in our binocular vision test, quite a few years back, we’re probably looking at 2020, 2018 mark. So go back into the archives, and there are some detailed slides there on how to do MEM retinoscopy. It allowed us to cheaply supply a small supportive add to patients who are patients who are struggling with their accommodative demand, early presbyopia. I have nothing against the MEM lens, it’s brilliant. If we have done MEM on the patient and discover a high lag on accommodation, then we know despite his age, despite being 37, he doesn’t have the accommodative power to cope with being undercorrected at nearby plus 125. And so the best way to choose his add, I think, is to go back to that MEM and add a little bit of 025 to both eyes until you get an MEM that’s within normal range. If we have done retinoscopy and discovered the perfect solution, given the level of hyperopia that he’s uncorrected by, there’s no way his accommodative system could cope with that, especially towards the end of the day if he’s doing a lot of near work. Then we add a small prescription to again support that accommodative system at near. So moving on to troubleshooting a patient who presents with a complaint of not being able to find the correct near spot or coming in with the complaint of having incredibly narrow near area or like this patient in case 6 who is just persisting with single vision distance because they hated varifocals and they never quite felt right when they were reading. When someone says I really hate varifocals, always have, because when I’m reading I could never get the reading that I wanted, then I always check convergence ability. In this patient we already know she has an exophoria without her glasses. With her glasses she has moderate exophoria. When this patient is looking down through her glasses, she isn’t actually converging as much as we would expect. So this is my patient here. Sorry about my little cartoon here. When we’re prescribing varifocals, the manufacturer insets the near area inward 3 or 4 millimeters to accommodate, this is referred to as the near inset. So what if, however, our patient isn’t converging? They’re missing the middle of that near area rather than going bang straight through the middle of that near area, they’re just catching the edge of it or missing it altogether. No wonder the patients find vision bothersome and restrictive. We adjust this by asking the manufacturer to bring the near set inwards but not quite as inwards as they would usually. So in this patient we’ve brought the near inset to 2 millimeters in both eyes, then we can see, looking straight through the near portion, she loved them straight away, which is great. This is a terrible slide, I tried so hard and as a result got my slides in late, I could not draw how I would do this. I probably should have taken some photos of my colleagues. But I do a mirror test. This is a made-up test, as far as I know. A colleague of mine, one of my very first colleagues and mentors, taught me this test and I use it on a weekly basis, if not more. So the first thing I do is I mark up the patient’s PD, distance PD, on their lenses. So just the same as we were before. You’re in line with them and their visual axis, they’re looking at your open eye, you’re dotting up with the center of their pupil and vice-versa for the other eye. When I have both marks in place, I hand them a hand-held mirror and I’ve drawn a cross with a marker on the center of that mirror. I get them to that the cross for me, and then, holding that sort of at their usual working distance, then ignoring me, I then, looking at the mirror, their reflection on the mirror, I dot on the lens where they’re looking at. It’s a rough way to do it, but it’s easy, and it requires no technology. So I know there are apps out there, and there’s things that manufacturers supply on their tablet where the patient plays a little game, presses buttons, and they can tell you where their near inset should be. But if you don’t have any that have kind of technology or you just don’t have the ability to work it out like me, this is what I do. Sorry. These also, actually, strangely enough, are a really good way to confirm that someone needs more pantoscopic tilt, which is the distance from the back surface of the lens — sorry, the angle from the temple to the back surface of the lens. So if you tilt the lens, bottom of the lens closer to the cheek, it’s going to be a little bit — that angle is going to decrease slightly. So a common complaint is the varifocal wearer, not a big change in prescription, gotten on well with the varifocals, nothing much has changed except their frame and suddenly their near vision is really rubbish. My first thought is, is this patient even looking through the lens. Usually you can tell, if you’re thinking there’s too big a gap there, you’re not looking through the lens. I hand them the mirror and they’re looking at the cross there and I can see straight away, through the reflection, are they looking underneath the lens or actually catching the lens? Of course the ability to adjust pantoscopic tilt on the frame will entirely depend on the make of the frame. You’ll be less successful on rimless frames rather than the rimmed frame. Sometimes it might just be a case, if this isn’t actually the frame for the patient, they need to pick a new frame. A monocular patient, one of the 101 dispensing tips is to provide a balanced lens. This is really important. The lens that’s over the eye that’s the no working, you want to still in that lens put a power that is about the spherical equivalent to the other lens as the same sort of index, the same sort of coating. So when someone’s looking at the patient, cosmetically it looks island to the other eye, it has equal magnification. It also has equal weight. If you’ve got a really thick lens on one side, you don’t want then zero on the other and the frame kind of tilting if it’s not — if it’s not a particularly sturdy frame. Something, though, that is less often taken into account is when dispensing varifocals from a monocular patient, you want to think about where the near add is and you want that inset to about zero. This also applies to patients who have a really large strabismus, it’s way out and doesn’t do much at all, or perhaps the patient is really, really amblyopic in one day. Essentially they’re monocular because they’re so heavily relying on one eye. So it’s also actually particularly important if the patient has lived with this for a really long time. The reason being is, when they hold something, and we’ll have a look here, when they hold something at near, they tend to hold it a little bit slightly off to the side of the dominant eye, which is really interesting, so that dominant eye doesn’t need to converge, doesn’t tend to converge. I also do this, this is another — a good example, I have a left micro esotropia. My right eye is slightly more dominant, also it means my left eye can sit inwards a little bit, it feels a little more comfortable like that. And I do this without even realizing, I also do it in presentations and photos, I put my head at a slight again, and I’m just trying to make it as comfortable as possible for me, but without even realizing. So you want to make sure that if you’ve got a monocular patient using varifocals, that they’ve got that inset at zero instead. So one aspect of a prescription that’s often forgotten in dispensing is adjusting for the back vertex distance, the distance from the front surface of the eye to the back of the lens. Once the prescription gets over plus or minus 4, it starts to impact the power of the lens. It really depends, obviously, on how big a shift you’re making. This is a really common chart that we see all the time in contact lens clinics, where it’s discussing the effects of a zero back vertex power that a contact lens has compared to a standard back vertex power of about 12 millimeters in spectacles. You can see here the closer the lens gets to the eye, your myopic prescriptive lens because less minus and hyperopic becomes a higher plus. That’s for contact lenses. What about for the difference between two frames on the same patient? So when the prescription is high, this actually makes the clinical difference. So here I’ve got a patient who is a minus 10.75, and on one frame they have a BVD of 10 millimeters and on a different frame, they have a BVD of about vertex distance of 18 millimeters. And this depends on the replacement of the nose pads and the bridge of each frame. Each frame is going to see differently on different noses. So for example, this 1075, it was tested at 14 millimeters in our trial frame. With the frame that’s 10 millimeters back vertex distance, I need my dispensing team to order in a minus 1050 lens. And for the 18 millimeter back vertex distance I need my team to order a minus 11.25 lens. Now, to be completely honest, I plug my prescriptions into an Internet conversion software rather than doing the conversion of each meridian by hand. However, this is the formula off to the side, and this is how it works. It’s something you need to know. But I guess thanks to technology and the Internet, we don’t actually have to do it in practice nowadays quite as often. Keep in mind you’re doing this for both meridians, both the still and the N sphere. It begins to contact, at 4 or so, it needs to get a lot higher in glasses for that sort of small adjustment in BVD to start making a distance. So we have a 47-year-old female coming in for an update of their lenses. And she wants to keep the same frame. So I trial frame refraction here at 13 millimeters, and this is the suggested refraction we get. And these are the lenses that are just ordered. So someone’s forgotten to adjust the BVD and something just doesn’t feel right. With the lens that we’ve ordered as they are without adjusting for BVD, she’s overcorrected by minus 025 and she’s a little uncomfortable. So for our case here, with the frame set at 11 elements and tested at 13, we do our math and we get a compensated prescription. This is the prescription that the exact power, once BVD has been compensated for, this is the exact power of the lens. Obviously I can’t order a minus 11.24 lens. So my given prescription is rounded up or down to the closest 025. The right lens is easy. I’m going to adjust it to a minus 11.25. It’s the closest. And with the sills are pretty close to the middle. I ran to the highest number since that’s what she’s been wearing in the past. The left eye, I had two choices. I could round to minus 9 or round down to 8.75. I chose 8.75 for two reasons. She’s already slightly overcorrected in her left eye, her nondominant eye. She’s just on the cusp of presbyopia. I prefer to undercorrect slightly to assist her with her near work rather than add to her near demand by overcorrecting her slightly. These cases also are pretty high prescription. So when you’re dispensing it, you’re going to want to think about the patient looking through the optical centers so you don’t accidentally induce prism. So you want to take height as well as PDs. And you also want to think about how you’re going to make the lens as light, as thin as possible, so both weight and appearance. So as you know, we want to pick a lens material that provides us with the lightest and thinnest appearance possible, and the higher the index of that plastic material, the density is allowing for higher prescriptions to be made up in a much thinner lens. This is a nifty table illustrating what happens to the lenses with high indices and it gives you a pretty good visual. But a common complaint is everything checks out perfectly, you redo the prescription, nothing is wrong with the lens. It’s sitting perfectly. But the patient is complaining about it’s clear but visually just uncomfortable. And in high prescriptions, one of my first thoughts is have we changed the index of the lens compared to their old glasses, so were their old glasses a 1.6 index and now we change it to a 1.74. And if we have, that will be it. Change it back to the 1.6 index and the patient will say, oh, this is so much more comfortable. The patient obviously still wants a thinner and lighter lens. So going down in index, we also need to think about how we’re going to achieve the thinnest lens. When it comes to this, it heavily leans on dispensing at this point. And the reason is, you want to pick the right frame for the patient, so we can order in the smallest blank size lens possible. So we have two examples here. On the left, there’s a large amount of excess that we would cut off the blank lens when we’re glazing the lens and putting it into the frame. On the right, we have the smallest amount of wastage. And why does this matter? The larger the lens, the thicker it will be. If we have a minus lens, its thickest point will sit in the periphery, and a positive lens, its thickest point will be in the center. So we want to order the smallest blank size we can get away with so we get the thinnest edge or center, depending on whether it’s a minus or a positive, that we can. One way of doing this is to ensure that the patient’s PD is as central in the frame or in the eye as possible. So if frame PD, the distance between the two centers of the frame, are pretty close to equaling the PD so the distance between the two pupil of the patient, then we’re going to be able to get the smallest blank size possible. So you can see with the example on the left, also if this was a negative lens, we would have a really thick edge on the lower temporal side of the frame because we’ve had to decenter all way up to that top corner. Additionally, the smaller the eye sides or the smaller your frames, the smaller the blank lens you’ll need to glaze into the frame. Often you’ll get patients with really high prescriptions coming with actually quite small frames, and they’ve done this in the past to minimize the thickness of the lens. This is math. I’m not going to go through the math with you, but it’s all there. This is how you find the minimal lens blank you need for this patient in this frame. I need to emphasize this, this isn’t just a patient or frame-specific value. The blank size depends on that patient in that frame. So the blank size will change with every frame, with every patient. This is a classic case of, everyone has prescribed the perfect lenses, however the patient is so uncomfortable because they’ve been prescribed a prescription that they usually don’t wear. So this patient, he doesn’t wear glasses except for near work, they’re happy with distance vision except they would like varifocals now for the convenience, they don’t want to keep looking for their reading glasses and taking their reading glasses on and off. And you can see in their reading glasses, they’re wearing a lower astigmatic prescription than what their actual astigmatic prescription is. So you want to check the full prescribing or full dispensing. Are we happy to make such a big change to someone’s prescription, particularly if it’s a big change to their astigmatism, or will this result in their feeling headachy or slightly nauseous? They’re walking around most of the day with the right eye undercorrected and they’re relying on their left eye to do all the work. You pop that new prescription on and the distance vision in their right eye is looking so much clearer, it also looks really, really weird and makes them feel a little bit sick. So we trial frame this in the clinic. I think it’s the only way to do it, to be honest. We have them walk around. We put in the full prescription, we say everything is coming up for me, everything is crooked, I don’t feel good. Then you take that down in 050 steps. I’m going to adjust my spherical equivalent to ensure my sphere, to ensure the spherical equivalent remains, until the patient says yes, yes, this feels fine, this is going to be okay. And then get them to sit down with the trial frame prescription that you’ve got, and then let’s put in the add and make sure that they’re feeling comfortable. Keeping in mind that they’re not really using that right eye in their day to day life and weren’t until they got presbyopic lenses anyway. You want to make sure your optical centers are aligned with the PD. And hopefully with full-time wear, with these varifocals, slowly you’ll increase the amount of astigmatism that they can tolerate in that right eye over time. But if the patient is comfortable, there’s really no need to push it just so you can achieve their best corrected visual acuity in their glasses. Last but not least, coatings. I think we can all generally agree on a standard hard coating. I think we can all generally agree there are noticeable advantages to the patient with antireflective coatings. They tend it find them a lot clearer. Every now and then someone will come back and say, I really don’t like the coating that you’ve put on, you can try changing manufacturer or you might just say, okay, antireflective coatings aren’t for you. They do tend to craze in heat and things like that, so advise your patient not to leave their glasses on the dashboard and things like that. But generally, I think we agree that a hard coating, antireflective coating, and now a UV coating is becoming sort of standard care. But the most available coating is a blue light filter, and this is a typical patient coming in, wearing glasses only to protect themselves from blue light emitted from computer and tablet and phone screen. So this is sort of the last topic we’re going to finish on. And it’s, “Is blue light really an issue?” The Cochrane Group about a fantastic meta-analysis, these authors gathered the up-to-date research on blue light filtering spectacles and ranked them on their quality of research and outcomes. They compared them all and found there’s actually little to no effect on symptoms of eye strain with short term computer use. There’s very little to no effect of critical flicker-fusion frequency, and possible effects on sleep quality. At this point here we don’t prescribe a blue light filter. We tell our patients, if they insist upon one, we tell them why we don’t believe it’s something they don’t require. If they really insist on it, no worries, if it makes someone feel better, but at this point, there’s really been not a lot of evidence to justify prescribing blue light filters, and we need a lot more of randomized uncontrolled trials to be done on this, particularly looking to visual performance and sleep. They’ve just brought out some — done some studies on macular health. But yes, a lot more needs to be done before we can say this is absolutely something that we need to be thinking about in our dispensing process. So that brings me to the end of our presentation here. I am going to get out of my slides here. Okay. And it looks like we have a few questions. I love that someone just answered a question [laughs]. What point should we keep in mind while fitting prisms for abnormal posture and the person underneath went ahead and answered them, thank you, that’s lovely. How much can access — if someone’s not having any issues, I would generally keep them as close to their axis as possible, unless it really dramatically improves their vision, I might go halfway if it’s a really, really big change. Obviously the higher the prescription, the less I can get away with tweaking without causing them to feel a little bit sick and unwell and having those adjustment issues. Oh, my gosh, this person — I love that this person is answering these questions. How to cure astigmatism, unfortunately not. I wish we could do that. A little bit out of the field of dispensing, though. Hyperopia patient, which type of glasses are beneficial? I think — I’m not quite sure if this is where you were going, but I think one of the things that I would consider with a hyperopic patient, how much of the hyperopia am I going to correct? If it’s at near, I’m going to correct almost all if not all of their hyperopic prescription. If it’s a little bit of a distance, I might lower their hyperopic prescription and increase the add accordingly, often my dispensing team will pop back in and say, this add seems way too high for this patient’s age, just want to check if this is not a typo. Sometimes it is a typo but most often than not it’s because they’re actually a latent hyperopia so I’m going to give them a slightly higher add to support that. Objective refraction, high minus, would this be the final prescription for the first time pediatric patient. I tend to see a lot of pediatric patients so I tend to want to say no, I would cyclo that kid, I would definitely cyclo that kid. Does an uneven add dispense a varifocal lens? You just want to know why it’s uneven. If you’ve got a legitimate reason as to why that person would have an uneven add, then go for it. If not, if you’re getting an uneven add, then you just want to really adjust the distance so you’re not getting that uneven ad, if they’re going to be using varifocal lenses. Unilateral pseudophakia, I think I would go with a contact lens. A little bit out of the dispensing wheelhouse, but that’s what I do. I’ve solved so many pantoscopic problems, it is so often an easy solution. Correlating for happy by focal users shifting to a PAL. When I’m thinking about corridor length, I only ever change corridor length if they’re a high myope. If they’re a high myope, what they usually tend to do is they’re going to bring their face wherever they’re looking, because anywhere outside of the very center of their lens is a little bit blurry. So you’ll find the high myopes when they’re reading, they tend to bring their chin down a little bit, more so than people who perhaps don’t wear glasses where they might actually bring their eyes down. So you want to think about prescribing a shorter corridor in someone who is a high myope because they’re going to catch that reading area rather than being like I have to do this and this is really uncomfortable. So in terms of corridor length, that’s probably the only time I really adjust for it. For a happy bifocal user, I see so very few bifocals nowadays, I think that I would go — I think that you could go for either. I think that I would maybe go for a shorter corridor. I don’t think that’s a bad idea. They’re going to catch that reading area a lot quicker. They’re already not using an intermediary. I guess you want to know if they’re using a screen and what their intermediate use is in their daily life. In the clinic, how (indiscernible), we can’t. I don’t know. That’s a really good question for dispensing opticians. I think you would have markings on a varifocal lens that would indicate those kind of things but on a single vision lens, unless it has markings on it, I don’t think you’re going to know. I love this question, it’s probably a really good sort of indication we’re getting a lot of those kind of things, that’s a good indication that perhaps we should go back and do a lecture on prescribing for strabismus. What happens if the PD is far from the center of the eye? So when you decenter the lens, and so the lens center is quite far from what the actual PD is, and it’s going to induce some prism, sometimes we intentionally do this as a nice, cheap, easy way of inducing prism that we want to be in the glasses. But sometimes it’s done by accident, because someone hasn’t taken PD correctly or at all, maybe it’s done online or something like that, and so that’s something that might just happen, just because that’s just how things have worked out. And so if those glasses are inducing prism, just kind of think about, okay, if they’re inducing prism, maybe they’re assisting with convergence or something like that, then if I straighten them all up and they’re looking through the center of them now and they don’t have that convergent support, it’s not going to be an issue for them. So this person — I love this, they say, I’ve been on Cybersight for a long time, I’ve had so many people actively answer questions themselves, I think it’s really cool. The higher the index of the lens, the index is actually not really talking about how thick or thin the lens is, it’s talking about how it affects the reflection of the light. And so you get a lot more aberrations with the higher index. (Indiscernible). So for that question, I think that’s probably — I would more consider if it’s a pediatric patient or not, are they amblyopic, regardless of whether they’re in the substantive refraction that comes up, and so that’s more sort of a clinical thinking of your final refraction. But yeah, I would — it depends on whether or not you actually need to correct that full astigmatism in order for that eye to stay healthy. Yes, so not really with the Miracheck. I try to do it, sometimes they don’t come in wearing a frame or something, in that case I’ll grab a frame and do it. But I’ll usually do it with whatever frame that they’re complaining about, these are their lenses, this is what I don’t like, we’ll do whatever they’ve got. But yeah, otherwise I would just do any plastic lens and any frame. I would like to know more about prescribing add during monocular case. Yeah, I think in the monocular case, you want to prescribe an add, obviously whatever that eye requires. I mean, you’re going to do it in exactly the same way. You’re going to add your — you’re going to take the patient’s age and estimate what the add is, you’re going to pop that add in front, and then give them a plus or minus option, does this improve your near vision. So it’s done in the exact same way, you’re just not doing it in both eyes. In terms of prescribing, in the prescription I would put this patient requires for varifocal methods. I know it’s weird, I did a crummy job at drawing on PowerPoint, so the first thing I do, and we might sort of — we might sort of — I did reduce the near add for the — we might sort of end on this, because we’re sort of running out of time here, I see the clock ticking up in the top corner there, so we’re running out of time. But the mirror test, I am directly across from the patient. They’ve got their glasses on. I’m going to get them to look at my open eye. I’m going to dot where the center of their pupil is looking through that lens. I’m going to get them to look here and I’m going to do the same thing there. Then I’m going to give them a mirror. The mirror is about — I’m trying to do this where you can say, they’re going to hold the mirror at their working distance, so it’s right in the middle of the two of us. And then I’m going to get them to look at a cross that I’ve just drawn on the mirror, just look at the center of that cross for me. Whilst they’re looking at the center of that cross, they’re also going to have a more natural head position, so if they’re like this, then I know that they really use their eyes, if they’re like this, I know they’re bringing their chin down slightly. Whilst I’m looking in the mirror, I am dotting where the near point is on their glasses. So where their pupil is looking through on the lens. Then I do it for the same, yeah. And it’s pretty rough, but it’s probably one of the things that I use most. And it’s probably the best trick that I’ve ever come across, thanks to Ian Clemens, who was my very first mentor at school. But I hope that makes sense. Give it a go on each other and sort of see — some colleagues, and see if it works, and give me some feedback. I should have taken some photographs or something, sorry about that. I’m going to leave it there, and I’m going to leave it there because I see that we’re sort of getting close to the end of our time. But thank you so much, everyone, for listening, and keep your questions coming to these guys. If there’s — on Cybersight, we’ve got mentors on Cybersight who are really excited to answer your questions, both on dispensing but also on prescribing and refraction, we’ve got a lot of optometrists there, so please send those questions to Cybersight, to the mentors, and we’ll answer it, as many as we possibly can. Thanks so much, everyone, I really, really appreciate it.