Lecture: An Introduction to Subjective Refraction

This live webinar covers an overview of subjective refraction, including a step-by-step guide for the procedure. Clinical tips are discussed, as well as potential pitfalls to avoid.

Lecturer: Diane Russo, OD, MPH, FAAO, New England College of Optometry, Boston, USA


(To translate please select your language to the right of this page)

DR RUSSO: Hi. Good morning, everyone. So I’m just sharing my screen here. So welcome. I’m Dr. Diane Russo. I’m an associate professor at the New England College of Optometry. And today we’re going to be discussing the fundamentals of subjective refraction. So this is really meant to be more of an introduction to subjective refraction. So I know that this is quite a broad audience. Joining us today. And so I tried to come up with a presentation that could address multiple needs of the participants. Some of this you may already know. Some of it may be new to you. And so we’ll see how many of you will still have questions at the end of this. There may be some things that we don’t have a chance to get to, depending on, again, level of experience of each of the participants. So this is really meant to be an introduction to subjective refraction. So specifically what we’ll be covering today is going over the components of the phoropter, particularly those that are relevant for subjective refraction. And then we’ll be going through the steps of subjective refraction step by step. We’ll be going through full refraction, left eye, right eye, and binocular balance. And as we go through this, I’ll describe some tips for troubleshooting subjective refraction, based on my own experience and tips and tricks that I use during refraction. I should also mention that the steps that I describe today in the presentation are a very basic outline of subjective refraction, and so it doesn’t have to be done exactly this way. There are multiple ways to do each of the techniques that I’ll show you, and so today I’m just gonna be covering one type of technique for each portion of the refraction. But you can manipulate this and change the steps based on what your needs are, based on your patient population, the setup of your clinic, what your time constraints are, and also what your experience is. So what I’m describing today is very similar to how I would conduct subjective refraction when I was first starting to practice. Although now I don’t follow every single one of these steps, because I’ve been doing this for a number of years, and so I don’t necessarily have to go through each step, step by step. And so just keep that in mind, as we’re going through the presentation. That you can adjust these steps based on your experience and your patient and clinic needs. So just looking at the phoropter, and again, we’re really only gonna be covering the parts and components of the phoropter that are relevant for subjective refraction, so there will be many other components of the phoropter that we will not talk about today. But the phoropter is a complex lens holder, and will allow you to efficiently and easily change the power of the lenses. It’s most commonly used for subjective refraction, and that’s how we’ll be talking about it today, but you can also use this for binocular and accommodative testing, and all this testing can be done both at distance and at near. So again, I’ve just highlighted some important parts of the phoropter for the procedure we’re going to talk about today. This knob here is for leveling. That will make sure that the phoropter is straight in front of your patient’s face. And then the pupillary distance knob or the interpupillary distance knob will adjust the width of the phoropter, so that the oculars are directly in front of each of your patient’s eyes. The auxiliary knob here — you can see each one of these writings is a different type of lens. But we’re only going to be really focusing on two of the auxiliary lenses today. The Jackson Cross Cylinder unit, which is right here, we’ll call that the JCC, and that will be for our cylinder axis and power refinement that we’ll go over. This is the window here for the sphere power. This is the window looking for the cylinder power. This is where you can see the cylinder axis, and then there’s also an indicator for cylinder axis here. And then there’s a knob to control the cylinder power, as well as this knob here, to control the cylinder axis. So this is just a general overview. I have a few more pictures that are magnified, so you can see each of these components a little bit closer up. So this is that auxiliary knob that I was talking about just a moment ago. So the two components of this that we’ll be focusing on are the O here and the O here, and that means that the ocular is open. So your patient can see through that. And so right next to this O for open, you’ll see the OC, which means occlude. And so when you have the OC in front of the ocular, it will be blacked out. And so the patient won’t be able to see through that lens. So really, there’s lots of other… Again, lenses in this auxiliary lens holder. But we’re really only going to be focusing on open and closed for today’s presentation. This is a close-up view of the sphere dial. So this is the dial that you can change up or down, to adjust the sphere power, and then in this window is where you read the sphere power off the phoropter. So you can see here this is zero. This is plano. There’s no prescription here. For cylinder, there’s a few more bells and whistles that come with the cylinder. So here’s the axis indicator. So this is in two places. One right here, which is a round ocular, where the patient looks through, and then you also have the axis indicator here. Your cylinder power window, again — this will tell you the power. This is a zero, so there’s no power in front of the ocular at this moment. And then the two knobs associated with adjusting the cylinder. So this knob here adjusts the axis. So you can see right now this axis is at about 42 or 43. And you can rotate this to adjust the axis, and then this knob you can turn to adjust the cylinder power. The JCC unit here rotates. So you can flip it in front of the ocular, and then take it away, and it locks into place when you flip it in front of the ocular. So this is the entire JCC unit. You’ll see that there are two red dots and two white dots. And these correspond to the axis. In the red dot’s case, the minus cylinder power. So this is minus order. And where the white dots are is where you’ll have the axis for the plus a quarter. JCC units can come in different powers. As you’ll see right here, this is plus or minus a quarter. And that by convention is what you will see most often on the phoropter. For the trial frame refraction, when you have a handheld JCC, those may come in different powers. They can be plus or minus one, plus or minus two, but by convention, we most typically see plus or minus a quarter in the phoropter. And then this is just another close-up of the interpupillary distance. This is the knob to adjust the PD scale, to make sure that the oculars are lined up with your patient’s eyes. So what is the goal of subjective refraction? So generally the goal is to develop a prescription, to come up with a prescription that allows the patients to see clearly, but also comfortably. And that is not always the same. So there may be times where you come up with a prescription that the patient can see clearly out of, but they may not be comfortable in it. And something that most commonly comes up in that respect is if you have someone with a lot of astigmatism. And one of the questions that I received from someone that had registered for the meeting is: What is a high amount of cylinder or a high amount of astigmatism? And that will vary, depending on if the patient has worn glasses at all. If the patient has never worn glasses, then a diopter or 1.5 diopters may be a lot. But if the patient has been wearing glasses for many years and they have 2.5 diopters of cylinder, if you have to make adjustment for that, that may not be as big of an issue, because they’re already used to having correction for astigmatism in their glasses. So again just keeping in mind that the goal of refraction is to come up with a prescription that the patient can see clearly, but also comfortably, out of. So these are the steps that we’ll be making our way through. Sorry. My lights went off in my office. And so we’ll go through this step by step, for the right eye, and then the left eye, and we’ll be finishing up with binocular balance. So where do we begin? When you’re starting refraction, where do you start? And there are basically four different places that you can start from. So the first is retinoscopy results. The second would be autorefraction and lensometry measurements, or from scratch, which I’m saying is from no objective finding. So if you have none of the above, no retinoscopy, autorefraction, or lensometry, you can still do a refraction, but it’s a little different how you conduct that. That is beyond the scope of the lecture for today. So for today’s lecture, we’re going to be assuming that you have some sort of measurements to work off of. So we will be starting from our retinoscopy findings for the procedure today. But you can modify this a little bit, if you have autorefraction or lensometry findings. Either just starting exactly from those findings, or you can add maybe a half diopter less minus or more plus, to start, if you’re worried about maybe giving the patient too strong of a prescription. But we will be starting from the retinoscopy findings. We will also be assuming a working distance of 50 centimeters, which is a 2 diopter working distance equivalent. These are our retinoscopy findings. And you may be saying… Wow. Those are really different prescriptions between the right eye and the left eye, which we don’t see very often. This is not based off of a real patient. I made these examples up for the purpose of the presentation today, so that we can get some experience working with hyperopic prescriptions, as well as myopic prescriptions. Lower amounts of astigmatism and higher amounts of astigmatism. We will also be assuming for this lecture the use of a Snellen acuity chart. By no means do you have to use the Snellen chart, but that is what we use here by convention. So we’ll be using that. The visual acuity, the VA units, I have reported in the 20-foot equivalent, because that’s what we use here, but I also have the meters equivalent. Because I know that’s also commonly used. And these can be adapted. The directions, as I go through this, can be adapted for how you record units for visual acuity, and whatever chart you use. Even though this will be in the context of Snellen charts with a 20-foot acuity, you can adapt this to your needs very easily. So our first step is to do an initial sphere check. So remember, we’re starting with our retinoscopy findings in the right eye, occluding the left eye, because we’re doing monocular subjective refraction first, and finishing up with binocular balance. So we can see in the phoropter here we have a +3 sphere. This is a little bit difficult to see, but this is a -1 cylinder at axis 180. So this is our first question. So what is the expected refraction based on the retinoscopy findings? With a working distance of 50 centimeters that I had mentioned before, which is a 2 diopter equivalent? And just as a reminder, this is the retinoscopy finding. Okay, excellent. So it seems like the majority of you put C, and that is correct. The reason that it’s +1-1 axis 180 is we know it’s a 2 diopter working distance, because of the 50 centimeter working distance, so we have to subtract the 2 diopters from the +3 sphere, and that’s why we ended up with +1. If it was 1.5 diopter working distance, which I know some individuals and providers use, then would have been the +1.50. But because we use a 50 centimeter working distance, then the sphere power should be +1. So we know going into this what our refraction should be around. It may not be exact, but it should be pretty close to +1-1 axis 180. So now we’re about to start the refraction. So I would usually open up the Snellen chart so that you can see multiple lines. I usually will start with around maybe the 20/60 line at the top, and I’ll tell the patient or ask the patient: Tell me as soon as you can read the top line. And so once I give those instructions, I’ll start reducing the plus power by a quarter diopter at a time. So change a quarter, change a quarter, change a quarter, and so in this case we’re reducing… We’re always reducing the plus. So I go from +3 to +2.75, +2.50, +2.25, and as I’m changing the sphere power, I’m making sure to prompt the patient to say… Let me know as soon as you can see that top line. If they’re never able to read the top line, it could be that maybe you won’t be able to correct the patient to read the bottom of the chart, and so in that case, you may just need to increase the letter size. They could also be having trouble reading the chart if your retinoscopy findings are a little off, or if there’s a high amount of cylinder, and maybe the axis is off a little bit. So there are a few variables that can impact whether or not they’re able to read the chart at this step. And so if they’re having difficulty, you can always just increase the letter size. Once the patient can read the 20/60 line, I will say the next set of instructions are: Okay, let me know what the lowest line is that you can read. What is the lowest line that you can read? Because now I know that they can read the top line. But they may already be able to read lower than that. So I’ll say: What’s the lowest line that you can read? And now at this point I start to change, again, that quarter diopter. So maybe I’m at +2 at this point. I know this is +2.75, but that was just to show how you change a quarter diopter at a time. So maybe we’re at +2 at this time. So I’ll change it to +1.75 and say… Okay, what’s the lowest line that you can read here? And see how far they can read down the chart. If the patient is having difficulty at this point — many of my patients have difficulty reading all the way across one line. Or sometimes they’re getting multiple letters wrong. And I’m not sure which letter, which line they’re reading from. So isolating lines at this point can be very, very helpful. With the patient population that I work with, I almost always isolate lines, and sometimes it takes a little bit longer. But it’s a little bit easier for me to keep track of what line they’re reading. So, again, you can adapt this, based on the needs of your patient population. So as, again, you’re changing… You’re taking out that working distance — remember, we’re working toward getting closer and closer to that +1 sphere — we want to see what the best acuity is for the patient at this point. And so as we’re working through this refraction in our example, we get to +1.25 sphere power. We haven’t changed the cylinder at all. And at this point, the patient is 20/25. And so if the patient’s vision is not improving, let’s say we go from +1.25 to the +1, and their vision isn’t getting any better, they’re still 20/25, then I would just leave them at +1.25, because the additional change to the power that you made did not make any difference. So that was our initial sphere check. Now we’re ready to start refining the cylinder. So there’s two components to this. The first is refining the axis. The second is refining the power. So we’re gonna start with the axis. The target that you use for this point is one line above the best vision that you were able to get on the initial sphere check. So for our patient, they were able to read 20/25, so we’ll go to the 20/30 line. If your patient was only able to get to 20/30, you would then show them the 20/40 line. So it’s one line above your initial sphere check visual acuity. And you isolate that one line. You would then insert the JCC, so you rotate the JCC into place. It clicks in. And you want the JCC to be an axis position. We’ll talk in a moment about what the difference is between axis and power position. And the directions that you give the patient at this point are: I’m going to be showing you two different views of this one line. I want you to tell me if one looks better than the other, or if they look about the same. So that’s sort of my general instructions that I’ll give to start. And then we’ll see how it goes from there. You may get various responses from your patients, but that’s generally how I start the directions for this step. So what does axis position mean, versus power position? So axis position is when you have the red and white dots here. So you have your red dot here, white dot here. On either side of the arrows. And so here’s our arrows at 180. Because that was the axis that we found on our retinoscopy. So this is 180. We have another arrow actually here. There is one here. It’s just getting cut off in the picture. And so on either side of the arrow, you have your red and white dots. And that is axis position. We’ll talk in a moment how that is different from power position. So again, I use some shapes to make it a little bit easier to point out. So this is where our axis is, at 180. And so our dots are on either side of those arrows. So we’ll tell the patient: This is view one. There’s a little wheel right here. And you rotate that wheel to go from view one to view two. So we say: This is view one, and this is two. And you’ll notice, as we go from view one… So we have the red dot up here… To view two… The white dot is now up here. So the dots flip. They swap. So view one, view two. And I’ll say: Which is clearer? Or do they look about the same? And if your patient is hesitating, maybe they’re not quite sure how to answer, you can also say: You know, both views may be blurry. But is one better than the other? Because very often both may be a little bit blurry, but what we’re trying to get after is: Is one better than the other? Or are they equally blurry? And equally blurry is okay. So in our example, if the patient chooses view one… So this is just, again, a picture of view one… What adjustment should you make? And just for clarification, when I say you rotate clockwise, you rotate this way, you rotate to the right, and rotating counterclockwise is rotating to the left. Okay, excellent. So it looks like the majority of you answered that you would rotate the cylinder clockwise, which is correct. So just for clarification, clockwise would be to the right. And I have some arrows showing you this. So in our scenario, the patient chose view one. And that’s what you see here. If you imagine that this is split in half, you have your red and white dot on this side, your red and white dot on this side, and you need to rotate the arrows in one direction or the other, you see your arrow here… Arrows… And it needs to either go clockwise or counterclockwise. So when we’re refining the axis, we always want to rotate your arrows toward the red dots. That’s the key. And so in this scenario, if we were going to rotate toward the red dots, we would be rotating to the right, which is clockwise. We’re rotating in this direction, towards the red dot. Because we’re rotating toward the red dot, when we’re doing axis refinement. And you would repeat this. Is it better… One or two? Three or four? And you would go back and forth, making adjustments. Always rotating your axis toward the red dots, based on the patient’s response. Until the axis is finalized. And what do I mean when I say the axis is finalized? It’s either when the patient tells you that the views look the same — although very often that will not be the case — because we’re giving a choice, patients may feel that they have to choose one or the other, even if you tell them it can look the same. It may never look exactly the same, and that’s okay. But if a patient is going back and forth, so let’s say… You know, in this example, the axis is moved from 180 to 170, let’s say they’re going back and forth and maybe at one point they choose to rotate clockwise, so then you take them to 165, and then the next time you give them a choice, they want you to rotate it counterclockwise, which would be closer to 170. So they’re going back and forth. At that point, you just choose one, and then you move on, because you could be going back and forth for a long time. One question could be: How much of an axis change do you make? So if we’re starting at 180, and the patient wants us to rotate the axis clockwise, based on their responses, how much do you rotate the axis? Do you rotate it 5 degrees? 25 degrees? And the rule of thumb is that… The smaller the amount of cylinder power, the larger the amount of axis change you can make. So for our example — let me put that in context — we have 1 diopter of cylinder power here. So that’s a smaller amount of cylinder. And so if I’m making adjustments, and starting at 180, if the patient wants me to rotate it clockwise, which is what they chose in the example I showed, I would maybe change it to 165. And go from there. So I might make a 15-degree change. Because it’s a smaller amount of cylinder. But if you have a larger amount of cylinder — say, 2 diopters of cylinder power — then I would make smaller axis changes. Like maybe 5 degrees. And we’ll see that in the example when we get to the left eye. So we, in this example, we’ve repeated these steps. And now we’ve finalized our axis to be at 170, as opposed to the 180, which is what we found on our retinoscopy findings. Now we’re ready to refine the cylinder power. So we want to switch the JCC to power position. And you can regive the same directions, but very often, your patient won’t notice the difference between — you know, axis and power refinement. So I just continue to give the same directions. Is it better one or two? Three or four? One or two? Three or four? And so when you’re giving those options, they won’t necessarily know that… Okay, now we’re doing the axis, versus now we’re doing the power. So the directions are the same. Tell me if one looks better than the other, or if they look about the same. And so power position, now, is a little bit different than axis. Because before, we had the red and white dots on either side of the arrows. And now we want the red and white dots lined up exactly with the arrows. So you can just rotate the JCC, and it clicks into place, so that now you can see the white dots are lined up with the arrows. You can see the arrow there. This is where our axis is oriented. So the white dots are lined up. And it doesn’t matter if you line the white dots or the red dots up initially. As we give those choices, 1 or 2, the red and white dots will swap. So it doesn’t matter where you start. You may also have noticed at this point that I’ve been saying 1 or 2, 3 or 4. And then going back to 1 or 2. Technically, you can give whatever number options you want to the patient, but I don’t know how many providers really go above 10, if they’re giving options. But I usually stick with 1 or 2, 3 or 4, just to keep it simple. And then just go back and forth between those. But you could say 1 or 2, 3 or 4, 5 or 6, 7 or 8, up to 10. But I think for simplicity, I personally stick with 1 or 2, 3 or 4, and then go back to 1 or 2 again. So now we’re doing our power refinement. So we say this is 3 and this is 4. And what you’ll notice is: In 3, our white dot is lined up with the arrows, and then using this wheel here, we flip the JCC. So for option 4, now the red dots are lined up with the arrow. So 3 and 4. So this is our third question. So if the patient chooses view number 3, which you have pictured here, what adjustment should be made? Okay. So we’ve got some… We’re a little bit split between increasing or decreasing the power, which is good, because we’ll talk about that. The answer is we will decrease the cylinder power. Which just a little bit of a majority of you answered. So if our patient chooses number 3, it means that they chose the white dots. And when you choose the white dots, the patient chooses the white — that means you want to decrease the power. If they choose the red dots, you want to increase the cylinder power. So in our example, they chose the white. So you would want to decrease the cylinder power, and we always go in quarter diopter steps. So in this case, we’ll decrease the cylinder power from 1 diopter to 0.75. And here again is a little reminder. For power refinement, if they choose the red, you increase the power. If they choose the white, you decrease the power. And the same is when we were refining the axis. You do this until you finalize the power. So you would now say: Okay, I showed them 3 or 4. Now 1 or 2. And see what they choose. Your power will be finalized in a similar way that your axis is finalized. So if the patient says that both views look the same, then you can stop there. If they never say that they look the same, and they’re going back and forth, so they make one option, they want you to increase power, they make another option, they want you to decrease power, and you’re going back and forth, you just choose one. Some providers may choose to always choose the lower power. I don’t know if it really has a large impact, especially if we’re talking about a quarter diopter of cylinder power at this point. You just pick one and move on. Otherwise this could be a very time-consuming part to the procedure. So at this point of our refraction, we’ll say we were finalizing that power at that 0.75, so now we have refined our axis and power. It was -1 axis 180, and now we ended up with -1.75 at axis 170. So we’re done with the cylinder, and now we’re going back to our second sphere check. And so our sphere was — this is where we ended up, our sphere and cylinder power, after our initial sphere check, plus the cylinder power and axis refinement. So to begin the second sphere check you can add +.5 or +.75. It doesn’t really matter. In this example I chose the +.75. So we increased the sphere power from +1.25 to +2. So now the target for the second sphere check is opening up the chart, so that there are multiple lines visible. Usually you want the 20/20 line at the bottom. It depends on what your initial best sphere would be, acuity-wise, at that step. But if all is going according to plan, you would want to open up the chart with the 20/20 line at the bottom. And you start to reduce the plus power in quarter diopter steps, asking the patient: What’s the lowest line that you can read? So if you’re starting at +2, instead of the +1.25, you would say: What’s the lowest line you can read? And let’s say maybe they’re able to read the 20/40 line. Then you would take away + 0.25, so you go from +2 to +1.75. What’s the lowest line you can read? And then +1.75 to 1.50. Same thing. What’s the lowest line you can read? Once they’re able to read the 20/20 line, you stop. So in our example, once we got to +1.25, you’re able to read 20/20, and we stop. Of course, this is working out so nicely in our examples. But very often, patients may not be able to read 20/20. And so you can use these steps. What I’m showing you is meant to be a building block, building blocks for refraction, so that even if they’re not correctable to 20/20, you can still use these steps to get the best vision that they’re able to achieve. So even if their best vision is 20/30, or even 20/50, whatever it is, you can still use these same steps to get there. Once we’re done with our second sphere check, we can include check tests. And I’ve chosen to cover the +50 check test. But another way that you can do this is Duochrome. I did not include this, because I just sort of chose one procedure for each step of the subjective refraction process. But if you were going to use something like a check test, the +50 or the Duochrome, this is where you would do it. And so essentially you would take whatever the results of the second sphere check were. Add +50 to that, so ours is +1.25, so it would go up to +1.75, and ask the patient: What happens when I do this? Say they’re able to read the 20/20 line. Say keep looking at that line. What happens when I do this? The hope is that they say: I can’t read it anymore. Or it gets blurry. If they’re not sure what you’re trying to ask, say: Does the bottom line get blurry when I do this? And if the answer is yes, that’s good. If they say: No, I can still read it. It’s perfectly clear. That means that you overminused the patient. So you gave them more minus power than they actually needed, and so you may want to reduce it. So let’s say in this example — I go from +1.25 to +1.75, and they can still read that 20/20 line perfectly, then I would probably give them the +1.75. Or maybe +1.50. But definitely not the +1.25, because they’re still able to read very clearly, with the more plus. And so I don’t want to give them more minus power unless they need it, because that can cause them to overaccommodate, which can cause headaches, and we don’t want to do that. So that’s it for our right eye. So we have finished the right eye from beginning to end. And now we’re ready to move on to the left eye. And so to begin this step, you would occlude the right eye. So remember, we were using the open in front of the right eye, to refract the right eye. And we had the left eye occluded. Now we want to occlude the left eye, So this is now closed. And these are gonna be the exact same steps that we went through for the right eye. But you’ll see how things may seem a little bit different, depending on the type of prescription that we’re working with. So we started with a hyperopic prescription. Now we’re going to be working with a myopic prescription. Also with higher amounts of cylinder power. And so you see that the way that you think about it may have to change a little bit, because now we’re working in minus sphere, as opposed to plus sphere power. Because the prescription itself — the refractive error itself — is different. So this is our retinoscopy finding. In the left eye, to begin with. And so, again, we start opening up the chart with the 20/60 line at the top, telling the patient: Tell me as soon as you can read the top line. And so you reduce the plus sphere power by a quarter diopter at a time. And so if you think about it, before we were reducing the plus, we’re always reducing the plus. But when you’re working with hyperopic prescriptions, it’s easy to think of reducing the plus prescription. But when you’re thinking in terms of myopic prescriptions, you should also then be thinking of increasing the minus power. It’s the same thing. You’re just thinking about it in the opposite way. So we’re still reducing the plus power. But we’re increasing the minus. And so it’s, again… We’re doing the same thing. We’re just thinking about it a little differently. Because now we have a myopic prescription. So as we change that a quarter diopter at a time, once the patient can read the 20/60 line, for each adjustment that we make, we’ll ask: What’s the lowest line that you can read? And so once we’ve gotten in our example… 2 minus 3.50 to the sphere power, what’s the lowest line you can read? And they can read the 20/30 line. And let’s say I change it to -3.75. They’re still able to read the 20/30 line. I go one more, and now it’s -4, and they’re still only able to read the 20/30 line. So in that case, I went from 3.50 to 4 diopters and the VA didn’t change at all. So what I would do is go back to the first lens where that patient was able to read that line of acuity. So in our example, it was -3.50. So instead of keeping it at -4 or even 3.75, I would go to -3.50 and then go to change the cylinder, because this additional sphere power did not improve our patient’s vision at all. So I would not give that to them at this point. Now we’re moving on to the cylinder axis refinement. We’re doing axis first and then power. We want to isolate one line above the best level of acuity that the patient was able to read. So they were able to read 20/30, which means we want to show them the 20/40 line. Insert the JCC in the axis position. Remember, that means that the red and white lines are on either side of the arrow. So we can see here this is where our arrow is lined up. And the red and white dots are on either side of the arrow. Same directions as before. I’m going to show you two views of this line. I want you to tell me if one is clearer than the other, or if they look about the same. This is view one. Okay? And you can see that there’s — the white dot is on this side. And this is view two. And so they’ve swapped. And so if in this case the patient chooses view number one, what adjustment should be made? So this is our fourth question. And so this picture here is the picture of view number two, and this is the one that they’ve chosen. Okay. Very good. So it seems like the majority of you said to rotate the cylinder axis counterclockwise, and that is correct. So if you remember from our discussion earlier, you always want to be rotating toward the red dots. And so if we were to… This is the way I think about it in my mind. It doesn’t have to be the way that you think about it. But I sort of split this in half, and if I see where the arrow is, I know I need to turn it towards the red dots. And so in this case I need to turn it to the left. Rotate the axis to the left. Because that’s where the red dot is. So that’s counterclockwise. And again, you would repeat these same steps, making adjustments, either rotating the axis right or left, until the axis is finalized. Which is when either the patient says that both views look the same, or if they’re going back and forth between two values, you just choose one. And remember, this is sort of that other tip: Because we’re working with the higher cylinder power, we’re working with 2.25 diopters of cylinder, we want to make smaller axis adjustments. So instead of every time the patient makes a choice, maybe rotating it 15 or 10 degrees, we might only want to use 5-degree changes in this case, because the cylinder power is much higher, and so the patient’s vision will fluctuate significantly, if you make large axis changes. And so in our case, we had initially started with an axis of 1.16. As we rotate it counterclockwise and then go counterclockwise again, we ended up with an axis of 1.25. So that was the axis refinement. Now we’re ready to change the power. And so we switch the JCC into power position. Which is when the red and white dots line up with the arrow. And again, it doesn’t matter if you start with the red dots or the white dots lined up with the arrow. Because as you change the options 3 or 4, 1 or 2, those dots swap. But you do want to make sure that one set of those dots are lined up with the arrow to start. So this is option 3. You can see that the white dots are lined up with the arrows. And this is 4. Now the red dots are lined up with the arrows. So for our fourth question, if this patient chooses view number 4, or maybe this is our fifth question… What adjustment should be made? Okay, excellent. So the vast majority of you chose increase the cylinder power, and that’s correct. So what we had discussed a little bit earlier was that if the patient chooses the red dots, you want to increase the cylinder power. If they choose the white dots, you want to decrease the cylinder power. So because they chose red, we want to increase the power by a quarter diopter. So you’ll see that we went from a power of 2.25 to now 2.50. And then again you would repeat this, showing is it better 1 or 2, 3 or 4, making adjustments based on the patient’s responses, until the power is finalized, which is when either the patient says the views look the same, or if they’re going back and forth between two powers. So let’s say the patient makes one choice to increase the power, and they want us to go up to 2.75, and then the next choice they want us to decrease the power to go to 2.50. So now we’re going back and forth between 2.50 and 2.75. You just choose one. I probably, by convention or habit, will choose the lower power. So I might go with the 2.50 at this point. You can always change it later, if you need to. The point is to just choose one and keep going, because otherwise you can go back and forth and lose a lot of time during the refraction. So now we’re done with the power refinement, and we have settled on -2.50 as the power. So now we’re ready for our second sphere check. And to start, we have the -3.50, which is the endpoint of our initial sphere check, with -2.50, axis 125. So we’re ready for the second sphere check, and you add either +.50 or +.75. It doesn’t matter which one you use. In this case, I added the +.75 and open up the chart. You usually put the 20/20 line on the bottom, and then you ask the patient: What is the lowest line that you can read? As you reduce the plus power, or increase the minus. So you go from maybe 2.75 to -3. What’s the lowest line you can read? From -3 to -3.25. Same thing. What’s the lowest line you can read? And once the patient is able to read the 20/20 line, that’s your endpoint. As we change the sphere by a quarter diopter at a time, in our example, we wound up getting to -3.75, and the patient is able to read 20/20 there, so we would stop. Again, this is our check test. I’ve chosen the +50 check test. It’s quick, it’s easy for the patients to understand, so we settled on -3.75, we added +50, it becomes -3.25, and I ask: What happens when I do this? Let’s say they were able to read the 20/20 line. I say: What happens to the line when I do this? Can you still read the line, or does it become blurry? If it does not become blurry, the patient can still read it easily. Then you’ve given them too much minus power, and so you then probably should reduce the minus power by maybe half or at least a quarter, depending on how easily they’re able to read the line. So let’s say in our example we had finished with -3.75, but when I showed them -3.25, they can read that bottom line easily. No hesitation. They get every single letter correct. Then I would probably give them the 3.25, or maybe even check their vision with a -3. Because it seems that we definitely probably gave them too much power. Now we’ve finished with the right and left eye monocular subjective refraction, so we’re ready to binocular balance. There are several binocular balance techniques that you can use. I’ve chosen one that I think is fairly straightforward. For the clinician and also for the patient to understand. There are pros and cons to every binocular balance technique. So you may not want to use this one all the time. But I just chose one, because it’s something that I more commonly use. One of the questions that someone had asked as part of the registration was: Do you have to binocular balance? And not necessarily. So the point of binocular balance is to make the stimulus to accommodation equal in both eyes. So you don’t want to have one eye having a much stronger prescription than the other. And so the vision is then clear and comfortable. But as you do this, you may not need to binocular balance every patient. Certainly patients that are not able to accommodate, so our older patients that we know have presbyopia, that’s not as much of an issue. But even on younger patients that can accommodate, I don’t binocular balance all my patients. It depends on your comfort level, the preferences of the patient, how much you can rely on your monocular subjective refraction results. So you don’t have to binocular balance every patient. But if you are, then I will outline this one procedure for you. So this is successive, alternate occlusion. It only works — any binocular balance technique will only work if you have equal best corrected VA between the two eyes. So if both eyes are 20/20, then you can do this. If both eyes are 20/25, then you can do this. If one eye is 20/20 and one eye is 20/40, you shouldn’t be doing binocular balance, because the vision is never going to be equal between the two eyes, and so it invalidates the procedure. So if you have equal vision between the two eyes, and the patient is young enough to accommodate, you may want to binocular balance. To start this, you can either add +.75 or +1 sphere power to both eyes. You want to isolate one line for this procedure. You can use either the 20/50 or the 20/60 line, depending on how much plus power you add. But you do want to make sure that the patient is able to read all the letters on the line with each eye. So let’s say you add +1, and you show the patient the 20/60 line. If they’re not able to read the 20/60 line, then I would go to the 20/70 line. You want to make sure with each eye that they can read that line. And the directions are that I’m going to cover one eye at a time. Both eyes will be blurry, but I want you to tell me which is clearer, or if they look the same. So this is our refraction. If we were to add +75 to each of the eyes. And so we say: This is view 1, where you occlude the left eye, and you can occlude it in the phoropter, or you can just cover with your hand. Which is usually what I’ll do, because it’s quicker. So view 1 with the right eye open. And view 2, with the left eye open. So you have your right eye occluded. Or you can just use your hand. So I find it easier just to cover one hand and then the other, as opposed to opening up and then closing. So view 1, versus view 2. So in our case, let’s say the patient chose view 2, which is with the left eye open. They said that’s clearer. So whichever eye the patient says is clearer, you add 0.25 diopter of plus power to that eye. So in this case, it was -3. They said the left eye was clearer. So we would change it to -2.75. And then you would do the same thing again. Is it better 1 or 2? And see what the patient says. If the patient never reports that they’re equal, so they’re always saying that one is better than the other, that’s okay. That’s a common endpoint. I would leave the dominant eye slightly clearer. You may need to then check eye dominance. Most of the patients that I work with have right eye as their dominant eye. And so very often I will leave that eye as the clearer eye. And then move on. And so then you would open up both eyes, and show them the VA chart. Open up to multiple lines, with the 20/20 at the bottom. And reduce the plus power by a quarter diopter at a time, asking the patient: What’s the lowest line that you can read? Take out another plus a quarter, what’s the lowest line you can read? Until they’re able to read the 20/20 line. And so in our example, we reduced the plus power we had added, so we end up with +1.25, -0.x170 in the right eye and -3.50, -2.50 in the left. Someone asked: do you have to check binocularly and monocularly again? It depends. You may not have to check monocular acuity again, because you’re pretty certain they’re around the same monocular acuity as when you originally checked, but if you made a larger change, you may want to check the monocular acuities as well. So some future considerations that we, again, didn’t have time to cover in today’s lecture, was: How to adjust the refractive procedure if there’s no cylinder power found on your objective testing. So when you have a sphere power, on your retinoscopy findings. How to start a subjective refraction without any objective findings. And what are the different methods for cylinder determination, the check tests, and binocular balance. I mentioned for cylinder determination, we used JCC in this presentation, but you can also use the Fan-Chart or the Stenopaeic Slit. It depends what equipment you have at your disposal. The check test. We used the 0.50, but there’s also the 0.1 or the Duochrome. And then there’s binocular balance. You can use the successive occlusion, or the Risley Prism, or there are some techniques using polarization, so that the patient is truly binocular. Again, there are many ways to do these different periods, different procedures, so I just chose one for the presentation today. I know some of these are covered in future webinars. The trial frame webinar may address some of these, but we were constrained by time today. So we wanted to have a brief overview. These are some of the references I used, in addition to my own clinical experience, and I’m happy to take some questions now with the remaining time we have.
>> Thank you, Dr. Russo. You can just stop sharing your screen, and we have a couple of questions. Do you want to open the Q and A box?DR RUSSO: Sure. Yes. I see many. Okay. So I had read one of the questions at the top here, from Penda McDonald, and this also brought up a couple of questions that came… Sorry. That came up from the registration. So a number of individuals had asked about cycloplegic refractions, and refracting children. And so this question somewhat addresses that. They were asking about… Can you see the questions? Or should I read them?>> If you don’t mind reading them.DR RUSSO: So this first question was asking about a 14-year-old who is reading 1/1 without correction, but who is getting migraines and tearing when they’re reading, and they wanted to know what are appropriate tests for this person, and what glasses should be prescribed, or solution to be prescribed to relieve these symptoms. And so this is a little bit more complicated, because the patient is getting migraines and tearing so from a refractive standpoint, this could be some hyperopia, latent hyperopia, there could be astigmatism there. So from a refractive standpoint, using cycloplegic drop would be very important for this patient. Especially given that they’re 14. Because the tearing could be because of eye strain. That they’re experiencing from having uncorrected refractive error. And so I would start there, to see if there’s any uncorrected refractive error, because the tearing and the migraines could be occurring because they’re related to the same issue. But you would have to investigate that first. You might also need to do some binocular or accommodative testing. But the first thing to start with would be the refraction in that case. What do you think about bifocal versus progressive glasses? What do you recommend for presbyopic patients? So this, in my experience, for the most part, boils down to patient preference. The only… One of the few times where I might recommend specifically a progressive, as opposed to a lined bifocal, is if the patient is doing a lot of work on the computer. Because if you’re doing the lined bifocal, then you’re missing that intermediary distance. But again, it depends on if the patient is willing to get used to the progressive glasses. Because there is an adjustment period — much more so for progressives than for bifocals. The other question was: How can we prescribe glasses in the case of hyperopic anisometropia amblyopia? So that is a really good question. Again, a little bit beyond the scope of our talk today. I was assuming the best case scenario, that our patient is able to read 20/20 in both eyes. But very often that doesn’t happen. And so when you’re taking into account hyperopic prescription, that there is anisometropia, and also amblyopia, one of the important aspects of this is knowing what the dry refraction is. So without any drops. What is the power in each eye? And then once you’ve instilled the cycloplegic drop, what the power is in each eye. A number of questions that I received was: How to do a cycloplegic refraction. Before this lecture. And this may vary from clinician to clinician, but I don’t usually spend very much time on cycloplegic refraction. Usually I will spend more time on cycloplegic retinoscopy. And compare that to the dry retinoscopy or the dry refraction. Because cycloplegic refraction can take a lot of time, and it may be difficult for the patient to respond reliably, especially if they’re a young child. So in this case, if you have someone who is hyperopic with anisometropia and amblyopia, I would definitely try to approach it by looking at what the dry retinoscopy and dry refraction findings are, compared to probably the cycloplegic retinoscopy, and trying to decide from there what they would maybe be most comfortable in. You can either — depending on what your findings are, prescribe the dry refraction or maybe sort of cut the cycloplegic retinoscopy in half. It’s hard to give you a straightforward black and white answer, without having specific values. But that’s how I would approach it. The next question is: How do you work with kids? Do you use… I’m not sure what Refractyl… What exactly that is. At what age can you trust kids for a subjective refraction? Another great question with kids. I tend to approach refraction in a similar way with children. If you can use the phoropter — you may not be able to. You may have to use the trial frame refraction. So that may be something that’s addressed more specifically in the future trial frame refraction webinar. But you would use similar steps to refract children. But to the exact point that this person is asking… You know, at what age can you trust the child’s responses… So the general rule of thumb is that if a child is very young, but is able to, say, read from the acuity chart, so let’s say maybe they’re 5, 6, or 7, it will vary depending on how the responsive the child is. If they’re 5 but you feel like they’re really responding well and able to follow directions, then you can maybe rely on their responses. If they’re maybe shy or you’re not getting a lot of responses, then at that point you may need to rely on your objective testing. So in that case, I wouldn’t spend quite as much time on subjective refraction. I would do a dry retinoscopy, a cycloplegic retinoscopy, and then prescribe based on my objective findings. So the question is: Why is 6 by 6 the normal standard VA and not 6 by 9? We, I believe… I’ve seen in the literature that it’s usually 6 by 6, but I know by convention here we use 20/20. Some of it may depend on the age of the patient. And what the expectation is. I know with children a lot of times we don’t necessarily push to get to 20/20, depending on their age and their refractive error. But typically by convention, 20/20 is the standard, I know, at least here. And so that’s what we use. Let’s see. What do you do if a patient has high cylinder power but he is going to wear it for the first time? How can we Rx in a child, adult, and older? So with high cylinder power — and I sort of mentioned this a little bit during the presentation — some of the variables are how much cylinder, how old the patient is, and have they worn astigmatic prescriptions in the past. So if it’s a young patient, let’s say 8 or 9, and they have 2 diopters of cylinder, and they’ve never worn glasses, you might be able to give them the full 2 diopters of cylinder. You might. You might not. But if it’s a, say, 60-year-old patient with 2 diopters of cylinder, that has never worn glasses, I almost would certainly not give them the 2 diopters. The older the patient is, the more difficult it is for them to adapt to astigmatism correction. And so this, I would say… The most helpful procedure that you can do in this case is trial frame. So if you are in the phoropter, and you’re doing your refraction, and you get a prescription with a high cylinder, regardless of how old the patient is, you can put that into a trial frame, and have the patient walk around, see how they feel, and that will tell you whether or not they’ll be able to tolerate the prescription that you’re thinking of giving them. The next question: How do you prescribe prism? And whom should you consider in prescribing? So that is a much more complicated question than we’ll be able to address. So I would say… Because I didn’t talk about prism at all today, purposefully. Because, again, we wanted to do just a more basic lecture on subjective refraction. So that would actually maybe be a really good topic for a future webinar. Specifically talking about prism. Because it depends why you’re prescribing it. Is it to alleviate diplopia? Is it to alleviate asthenopia? So that’s maybe a good topic for a future webinar. Okay. What is the difference between showing the single line chart in the JCC, versus showing the multiple line chart in the second sphere check? Does this add to difficulty of reading for the patient? Yes. So I think exactly yes. When you show the single line in the JCC, isolating that line allows the patient to focus on one line. Because you don’t know… If you were to open up, let’s say, the whole chart, and let’s say you had between 20/50 to 20/20 lines being shown, you don’t know if the patient — let’s say they start looking at the 20/40 line, and as you’re refining the axis and the power, maybe their vision gets a little bit clearer, so maybe they’re looking at the 20/25 line. And now you started the procedure with one target and ended it with another. Which may be difficult. And so the patient may be giving you responses that you don’t understand, but it’s because the target has been changed. So isolating the line is a way to simplify the procedure. And control the target. When you’re doing the second sphere check, at that point, you’re trying to get the best level of acuity. The goal is not necessarily to record or obtain the best level of acuity for VA, but to control the target that you’re presenting to the patient. And so it is a little bit easier for you to control the target, certainly, but then for the patient to focus on one target, if you isolate the line on the JCC. The next question is: Do you fog the other eye? So if you’re starting with retinoscopy, your retinoscopy findings are fogging. And so just for anyone that’s not familiar with the term “fogging”, it’s when you purposefully blur the patient’s vision with plus power, to try and control their accommodation. And so you could purposefully fog the patient’s other eye while you’re refracting the one eye, but in the presentation today, I just occluded one eye and then the other. But the other tests that I include, whenever I would suggest adding plus power, so for the second sphere check, to begin the binocular balance, any time I was including adding plus power to the directions, that was meant to partially fog the patient. And that’s done to control accommodation. So as I mentioned in the beginning, you can adjust this based on your patient population needs, and so if you’re working with an older patient population, you do not need to include those fogging steps, because especially if they’re presbyopic, then they’re not accommodating, and so you don’t need to control their accommodation quite as much. The next question is: How do you determine the endpoint for high myopic patients? And so the endpoint should generally still be the same. Whatever visual acuity standard that you are using, and so in the presentation I used 20/20, that is what you should be working toward. If you have highly myopic patients, or really any patient with high refractive error — it could be hyperopia or astigmatism — you should still be trying to get them to that visual acuity standard. But their vision may be reduced for other reasons. Their vision could be reduced because of amblyopia, their vision could be reduced because of some kind of pathology, if they have a cataract or retinal issue. And so the endpoint that you’re trying to get to should be the same, but you may not be able to get there, based on the type of refractive error that you have, if you suspect there could be amblyopia, or in the case of highly myopic patients, you could have other retinal pathologies that could be reducing acuity. What’s the highest cylinder power we can prescribe in those with high regular astigmatism? So I’m not entirely sure how to answer that question. The highest cylinder that you can prescribe? I think it depends on what the patient needs. And I think, again, it goes back to the goal of subjective refraction, and what I had just talked about with another question, which is: What does the patient need? So what makes their vision clear, versus what can they tolerate? What will they be able to see comfortably through? And so what’s the highest cyl that you can prescribe? I would say the highest amount of cylinder that the patient needs that they can tolerate without feeling uncomfortable. And so trial framing will be helpful there. Oh, this is a good question. If a patient has a -3 sphere with a -0.25 cylinder, do we need to prescribe the cylinder? This is a really good question, because I think you’ll get many different responses depending on the clinician that you’re talking to. I very often do not prescribe 0.25 of cylinder. Because it’s such a small amount of cylinder. It usually does not make a difference. However, some patients are very, very sensitive to blur. And they need the quarter cyl. So do you need to prescribe it? I think the answer to that depends on if your patient truly appreciates a difference. So what I would show them is the -3 with the quarter cylinder, and then take it out. And say is it better 1? Put the quarter cylinder in, or 2, take the quarter cylinder out. And if they say yes, I would say… Okay, is there a big difference between 1 with the cylinder in and 2 with the cylinder out, and see what they say. So based on their responses, you can decide whether or not to prescribe. But more often than not, the patients won’t need the quarter. But that’s one way to check. Are there glasses protection for computers? So that’s another good question. So technically, yes. I know that those are on the market. I think it depends. So the sort of twofold reasons that I’ve been seeing glasses come to market for the computers: One is if there’s maybe a small amount of plus power in them, to alleviate accommodative demand, to then alleviate asthenopia. The second reason I’ve seen them on the market is with a filter for blue blockers, to block the blue light that comes off the computer. I don’t know if the evidence is quite there to substantiate the blue filtering lenses. But certainly the use of low plus power to alleviate accommodation and subsequent asthenopia could be a reason to prescribe glasses for the computer. There’s a question about binocular balance with the prism, with the autorefractive error. With the autorefractor. So I know I had mentioned one binocular balance you can use that utilize the Risley prisms, and I use that often. I’m not familiar with the use of the autorefractor. But with the phoropter, I think yes, that might be a little bit of a typo, but yes — you can use it with the Risley prisms. I just didn’t have time to cover that today. How do you refract a patient after unilateral cataract surgery? So I think the trick there is whether or not the patient is having the other eye done. So if a patient, let’s say, has cataracts in both eyes, and they’re having one done, and then waiting a little while, and then having the second done, you may wait and not give any glasses in between. If they have only one cataract in the one eye, and they’re not gonna be having the surgery in the other eye, then you would just refract the same way. Just the same steps that I gave you, you would go through that the same exact way. Something that may be key there is trial framing. So putting the prescription that you find in the phoropter in a trial frame, and showing it to the patient, to see if they can comfortably see. Because what I think you’re getting at there is noticing that after cataract surgery the prescriptions can be very different, and that might be uncomfortable for the patient. So you would still refract the same way. The difference is: What would you actually end up prescribing? And so showing the patient in the trial frame what you’re finding in the phoropter will be helpful in determining that. Can we build our refraction on autorefractor, not retinoscopy, in a three-year-old? Well, I would say if you can get a three-year-old to sit in an autorefractor, maybe. More often than not, the pediatric optometrists that I have worked with do not use an autorefractor for children. The main drawback is that it will show an artificially high myopic prescription or just more minus, because they’re overaccommodating while they’re sitting in the autorefractor. So theoretically, you could, if you could get the child to sit in the autorefractor, but I don’t think most pediatric practitioners do that, because of the impact on accommodation, and they don’t want to overminus the child. Do you recommend doing retinoscopy in the phoropter or the trial frame? I by convention use the phoropter most of the time. So I’ll do retinoscopy in the phoropter. If you were to do it in a trial frame, or in free space, if you had a lens rack, that’s a little bit quicker. So it’s a rack of lenses, so there’s usually one for plus lenses and one for minus. And that’s a quick, easy way to do it. If you choose to do it in a trial frame, you certainly can. It may take a little bit longer, depending on how proficient you are. So if you don’t do it very often, then it may take you longer. But if you do it all the time, then there’s certainly no reason that you shouldn’t be doing retinoscopy in the trial frame as well. Let’s see. A couple of questions down. If there is no retinoscope, is that a little skip a self-refractor? I’m not exactly sure what that question is getting after. If you don’t have retinoscopy findings, but you have access to an autorefractor or a lensometer, you can work off of either of those findings. If you don’t have any of those, you can start from no objective findings. We just didn’t have time to cover that today. So that is an option. It’s not to say if you don’t have objective findings that you can’t conduct a subjective refraction. It’s just your approach to that would be a little bit different. The next question: Can binocular balance be done at a distance other than the 20 feet or 6 meters? Certainly. You can do this type of testing that’s any distance that you choose, theoretically. The closer you are to the patient, you may have to consider if you’re stimulating their accommodation. But you can certainly do this at different distances, and the steps that you would follow would be exactly the same. It’s just how you record the acuity findings, which would be a little bit different. The last question is: If a patient has strabismus, can we use the phoropter? Yes. You can still use the phoropter. But if you occlude one eye at a time, assuming the patient is able to take up fixation if one eye is occluded, so let’s say the right eye is the dominant eye and that’s the eye that fixates, whereas the left eye is the eye with the strabismus, you could occlude the left eye and refract the right eye and occlude the right eye and refract the left eye, and once the right eye is occluded, the left eye will take up fixation. If you’re having trouble with that, you could do the trial frame refraction and not use the phoropter, but you should be able to use the phoropter with patients who have strabismus. I know there’s a planned trial frame lecture coming up, so that may be helpful for many of you to participate in as well, and see how the two lectures complement one another. So I think that is it with the questions.>> Yes, thank you so much, Dr. Russo. I think this is a good place to stop. Thanks for staying on to answer everything. Have a good day, everyone.DR RUSSO: Thank you.

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April 30, 2018

Last Updated: October 31, 2022

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