Lecture: Ultrasound B Scan of the Posterior Segment

During this live webinar, we will discuss the basics of ultrasound B scan, its indications, examination techniques and common posterior segment conditions seen on ultrasound B scan. Questions received from registration and during the webinar will also be discussed.

Lecturer: Dr. Sashwanthi Mohan, Specialist Ophthalmologist, Medcare Eye Centre, Dubai, United Arab Emirates


Good evening, everyone. I’m Dr. Sashwanthi Mohan. I’m an ophthalmologist specialized in the retina. Thank you for the opportunity. It is a vast topic but today I will be focusing on the ultrasound B scan of the posterior segment of the eye. I want to give you some tips. B stands for brightness modulation scan, a noninvasive technique where two-dimensional brightness display is obtained. The brightness intensity to the proportional to the echo amplitude. It provides a 2D cross-sectional view of the structure. In 1956, Mundt and Hughes discovered the A scan. Baum and Greenwood discovered the B scan in 1958. Knowing all this, let’s move on to the first tip. Before we learn how to do a B scan, we need to understand the physics and principle behind it. Two important terms you need to remember. One is the acoustic impedance, the ability of a medium to resist the transmission of ultrasound waves by virtue of its density. Another important term is echo, a part of a sound wave which is reflected back towards the source of emitted energy from the interface between the two media. It’s created at the junction of the two media with two different acoustic impedance. The greater the difference in the acoustic impedance of the two media, the stronger the reflection of the sound wave. So as you can see in this picture, there is this diagrammatic representation. The dense are the medium, the stronger the echo. Less dense medium will give you a weaker echo. What is the frequency of sound waves we use in ophthalmic ultrasound? Most of you got it right. We know what the basic principle is. An electronic pulser source generates a signal and the transducer is stimulated. A sound wave is projected onto the ocular tissue. Once it’s projected, it gets reflected back and is collected by the transducer and is amplified by a receiver which is then displayed on the monitor as the 2D display we see on the B scan images. This is 10 megahertz, the most common one we use. The strength of the echo in the B scan is depicted by the brightness of a dot. Coalescence of multiple dots on the screen forms a 2D representation of the examined tissue. Gain is a procedure of increasing or decreasing amplitude of echoes that are displayed on the screen. The higher the gain, the greater the ability to detect the weaker echoes. Time gain compensation is a technique used to enhance returning echoes from deeper structures by reducing those from the structure closer to the surface. Now we know the principle and the physics. Let’s come to when to do a B scan. We always need to know the indications as to why we’re doing a B scan. These can be divided into opaque ocular media and clear ocular media. In the opaque ocular media, certain modifications of the B scan such as — the anterior segment, when we can not view the posterior segment, we need to use a B scan to see the posterior segment. In hemorrhage, retinal detachment, in some cases of trauma, we need to use the B scan. In clear ocular media, we use it in some anterior segment diseases such as to accidents iris and ciliary body tumors. In posterior segment, we want to look at retinal detachment and also during followup, or to look for optic disc anomalies, or to see choroidal detachment. We also do it in ocular trauma to look at the location. Tip 3, know your instrument. So the most important instrument of a B scan is the probe. We need to know how the probe functions so that we know how to orient the probe. So first showing you the B scan probe parts. There is an insulation cover, a piezoelectric crystal. It also has a backing material and a matching later. The backing material is located behind the crystal and it is made up of damping material which helps to dampen excessive vibrations from the probe. The matching layer is present in front of the crystal which sends the reflection between the probe and improves transmission. A very important thing to remember here is the probe marker. As you can see, a dot is present here. This is what signifies what the probe marker is, it’s important to understand the orientation of the scans. So this is a very important tip to remember when you’re doing a B scan. To remember orientation, remember when the probe marker points to the top of the scan, that the probe marker, the dot on the probe, will point to the top of the scan. If it’s pointing nasally, the nasal part is at the top of the scan. Another thing to remember is the patient’s ocular direction. If the patient is looking superior, the entire span will cover the area towards which the patient is looking. This is important, especially in transfer scans. So before we go to what is abnormal, we need to understand how a normal B scan looks before we do a B scan for an abnormal case. Let’s look at the anatomy of a normal B scan. Cornea and iris will not often be seen. The lens echo is hyperreflective in normal patients. Vitreous is — there are none in the vitreous. Retina and choreoid and sclera are one collection with a spike. The optic nerve head. Another important normal finding is this. This is called IOL patients. Patients in cataract surgery might have a normal posterior segment but this is not abnormal. Let’s look at way different examination technique. So B scan is usually done in a reclining or supine position. However, we do it in sitting position or sometimes even in prone position in special situations like silicon oil or gas filled eye. We also do it in sitting position to check for shifting fluid in exudative detachments. The probe is placed over the cornea with the eyelids closed. We can place it directly over the conjunctiva is better, since the eyelid is a structure, it would get absorbed. It is directly placed over the cornea although it is not as comfortable for the patient. A coupling jelly is always used with the probe because air will attenuate the ultrasound waves when ultrasound waves pass through it. The image documentation should always be doing stationary as well as dynamic. I’ll explain how later. So coming to the poll question 2, all of the following are B scan orientations except axial, sagittal, longitudinal, or transverse. Okay, thank you. So sagittal is not the usual B scan orientation we do. The B scan orientations are axial, longitudinal, or transverse. Axial is directed towards the center of the lens and optic nerve. Transverse is the most commonly done scan, it covers 6:00 hours. The longitudinal is not very commonly used. It gives you an antero posterior extent and is used rarely in retinal tumors and tears. A routine screening B scan in abnormal patient, we need to do four transverse scans which scans the coordinates of the eye, superior, nasal, inferior, and temporal, and two axial scans, horizontal and vertical. This will gives a good idea of the structure. If we find any abnormality, we can go ahead with a longitudinal scan. The special examination techniques, topography. We have to look at the location, extent, and shape of any leagues we’re describing. Quantitative is a reflective, internal structure, and sound attenuation. The reflectivity is based on the spike. Sound attenuation is increased as the sound waves pass through the particular leagues. Then we look at the kinetic scans. First is the aftermovement. That happens when the patient refixates, when the eye is moving. Vascularity, spontaneous motion when the eye is steady and the probe is also steady. The eye should be fixated and the probe should be steady, and vascularity will occur in certain tumors where you will notice rapid spontaneous motion inside the tumor. Conviction motion is the slow spontaneous movement which is seen in, for example, longstanding hemorrhages. Axial scans. Axial scan is done with the eye in primary gaze. The probe is centered on the cornea. The beam is directed to the center of the lens and intersects the optic nerve. So we get a picture of the lens and optic nerve in the same scan. There is horizontal, vertical, and oblique. The most common are the horizontal and the vertical. The probe marker should be towards the nasal site. The vertical axial scan, the probe marker should be towards the superior site. Oblique, it should be the upper of the two meridians being scanned. Poll question 3. In which axial scan can you see the macular? Vertical, horizontal, both vertical and horizontal, or D, oblique? The correct answer is horizontal. Let’s see how. In the vertical axial scan, the marker points superiorly. We can see the superior and inferior of the optic disc. The macular cannot be seen in the vertical axial scan. In horizontal scan, the marker points nasally. We can see the macular which is right below the optic disc, horizontal axial scan. Let’s look at how to do a horizontal axial scan. The patient should look straight with either eyes open or in this case the patient closes his eyes with the eyelids closed. The marker should point nasally. The patient is closing his eyes. The marker is pointing nasally, as you can see. As I described earlier, the macular will come below the optic nerve head on the corresponding axial scan. In this scan it will give you the lens, the optic nerve with the macular below the optic nerve and the axial length can be measured. Transverse scans are the most common scans. Transverse scans, the eye is inferior, nasal, or whichever direction you need to do. The probe should be parallel to the limbus on the opposite side. The probe marker is placed superiorly for nasal and temporal transverse scans and nasally for the superior and inferior scans. 6:00 hours are examined in this type of scan. 6:00 hours examined, the transverse scan gives us a good view of the lateral extent of any leagues. For superior transverse scan the patient obviously has to look superior. The patient is looking superior, the marker is pointing nasally. This scan gives us the superonasal and superotemporal. Since the marker is pointing nasally, it’s superonasal or superotemporal. As you can see, the patient is looking down, the marker is pointing nasally. This will give you the inferonasal and inferotemporal scan. The marker points superiorly, and the scan will give you the superonasal at the top or inferonasal at the bottom. This is the temporal transverse, the patient looks laterally. The marker points superiorly, as you can see, and the scan will give you superotemporal at the top of the scan and inferotemporal at the bottom of the scan. The limbus to fornix approach, the limbus will give you the posterior pole, and as you go towards the fornix it will give you the anterior periphery. This is anterior scans in both horizontal and vertical. For horizontal, the marker should point nasally. Patient looks up to do the superior anterior scans. As you move towards the fornix, will you get more anterior scans. In the posterior scan, the probe is at the limbus. Towards the fornix you will get more anterior scans. The vertical, you move it towards the canthus. As the probe is moved towards the canthus, you will get more anterior scans. You can examine the entire eye with this scanning technique. Coming to tip 8, longitudinal scans which are not very commonly done, but we do do it in retinal tumors or retinal tears, especially retinal tumors to look further. In this, the eye is always in the direction of interest. The scan, the probe will be perpendicular to the limbus. The probe marker is directed towards the limbus. It gives the anteroposterior extent. Let’s take the example of a longitudinal scan of the nasal quadrant. The first picture shows that the eye is looking straight and the scan is pressed — the patient — the probe is at the limbus. Then you ask the patient to look slightly medially and move the probe towards the canthus. Again, as the patient looks more medially and the probe is moved away from the limbus, you will get a more anterior scan. As you can see with the images, as the probe is moved away from the eye, away from the limbus and the patient looks more medially, you will get more anterior scans. This is 3:00. And an important scan is the longitudinal macula view. In this scan, the probe is kept nasally. The marker is directed towards the pupil. And the patient is asked to look out. So in this scan the optic nerve will come below the macula, like the actual scan we saw. This gives us — the macula comes in the center, the optic nerve comes below the scan and the patient has to look out nasally. This is the longitudinal macula view. Coming to tip 9, which is common conditions on the B scan. I tried to cover as many conditions as possible. The first one is asteroid hyalosis, an abnormal finding, it’s a pathological findings. Multiple homogenous densely packed medium to high reflective dot echoes with a clear space between it and the retina. So this clear space is the hemorrhage, right behind this high reflective dot echoes, is what is asteroid hyalosis. Vitreous hemorrhage, in this picture you see multiple low reflective mobile dot echoes and short lines in the vitreous with low amplitude spikes on the corresponding A scan. When the organization hemorrhages, there will be membranous opacities with higher reflectivity. As the hemorrhage becomes more dense and more longer duration, there is an increase in opacities. It is important to correlate in case of any opacities in the vitreous. Posterior vitreous detachment, it’s a low reflective membranous and is freely mobile. An important thing to remember, in this video you can see one with a blood line PVD with a high reflective echo. A black line is an expression that occurs where there is hem ridge. It can have more reflectivity. Coming to inflammation/vitreitis, as you can see, in the first image there are loculations can occur. Sometimes it is very different to differentiate between endophthalmitis and retinochoroidal thickening. The few differentiating points can be that in hemorrhage, the posterior vitreous attachment will be more extensive. In inflammation, that is one thing. The other thing is the vitreous capacities in inflammation will be more evenly distributed whereas in hemorrhage is settles due to gravity with layering of blood. This is not a hard and fast rule. There can be times where the diagnosis can be confusing if there are clinical systems that do not point to either. So coming to the poll question 4. All are features of retinal detachment on B scan except, A, high reflective echo, B, poor aftermovements, B, not attached to optic nerve head, or C, persists in low gain. So the correct answer is not attached to optic nerve head. The attachment is usually attached to the optic nerve head and it’s a high reflective echo which persists in low gain. Let’s look at it. So when we talking about retinal detachment, we need to divide it into rhegmatogenous, which is high reflective membraneous echo with poor aftermovements and extending to all quadrants, it is a total retinal detachment. When it does extend to all quadrants, it is a total retinal detachment. The reflectivity is high. There is a high A scan spike. There is attachment to the optic nerve head. It is restricted aftermovements. Extension, we need to see by the scan which quadrants it extends to. And it persists in low gain. Looking at the first video, we can see that this is a total retinal detachment, attached to the optic nerve head. We need to look for shifting fluid, we need to see — and typically it will be a bolus attachment but we have to look for shifting fluid by making the patient from the supine sitting position and seeing if the fluid level changes. But sometimes a bolus detachment can also giving you shifting fluid. We do the scan when there is hemorrhage to see the leagues. The hemorrhage will be concave and not convex. You can see attachments to the posterior vitreous in detachment. Choroidal detachment, it is smooth, dome shaped, high reflective membrane. You can see both the choroidal are attached to each other. It is never attached to the optic. As you can see, the membranes are separate and there is no attachment to the optic disc, it is not mobile. There is a double high speak called the M spike. One is the retina, one is the choroid. The choroidal detachment can be serous. There is no space behind it. It can also occur where opacities might be present. Hemorrhagic, there is multiple moderate to high reflective dot echoes behind the membrane. It is important to differentiate between the two. Now that you’ve seen so many membranes, we need to see how to different them when we see them on the scan. Very important to differentiate PVD from RD from CD. So PVD, it is not attached to the optic nerve head. In RD, it will be attached to the optic nerve head. Choroidal attachment is not attached to the optic nerve head. The PVD is low to moderate reflective membrane with corresponding low to moderate A scan spike. RD is high reflective membrane with corresponding high A scan spike. Choroidal detachment is high reflective membrane with a double or M spike on A scan. PVD disappears in low gain. RD and CD, it persists in low gain. PVD is dynamic scan, PVD will have good aftermovements. RD will have poor aftermovements and CD will have no movements. Very important are tumors. I’m just taking a few tumors as example. Choroidal melanoma is common for B scan. There will be low to medium internal reflective echoes. There will be sound attenuation through the lesion, that is, the lesion, even the A scan spike will show slowly decreasing reflectivity through the lesion. There will be internal vascularity. Less echoes will be present at the base of the tumor. We need to measure the height and the base in tumors. The high is measured when the sound beam is directed perpendicular at the tumor base which will give you two high A scan spikes. Then you measure the distance between them. The base, you have to measure both the transfers and longitudinal base. Transverse base will give you the diameter. Other important tumors are retinoblastoma with a high surface reflectivity and internal medium to high reflectivity echoes. It has internal calcification with orbital shadowing. You have to remember the retinoblastoma. Intraocular foreign body, in this one you can see bright opacity with orbital shadowing of anything behind it. You can see there is shadowing right behind it, extremely high reflective echo. Reverberation occurs in spherical foreign bodies. As you can see, it always persists in low gain. In which condition will you see T sign ultrasound? That’s right, posterior scleritis is the answer. So in posterior scleritis, a T sign, fluid accumulation in sub-Tenon’s space. It’s a hypocholucen area. Silicon oil filled eye also, with a total cataract of silicone oil injection. However, silicon oil filled eye ultrasound is not very easy to do, because the speed of sound in silicone oil is much slower than in that of the vitreous. In the first image, the eye appears longer than normal. Prone is the ideal position but not very comfortable for the patient. It’s preferred to scan prone or sitting position to scan the normal ocular wall. It shows you the elongated eyeball. The thin arrow shows how the normal eyeball looks when the patient is in the prone position. The third image is showing you, again, the thin arrow showing you an elongated eyeball and the thick arrow is showing you a detachment in the normal eyeball. So we have to do it in the prone or sitting position or we will not get accurate results. In spite of that, it is not very accurate to detect because there is high sound attenuation of sound waves through the silicon oil in silicon oil filled eyes. Some of the conditions are — this is one, hyperreflective globular shadow noted in inferior vitreous located in dislocated lens. There is a high reflective echo over the high reflective echo known as the optic nerve head. The other indication, we want to see what the cause is. For that we have to look for optic nerve head cupping. The optic disc is best seen in vertical transverse or longitudinal macula scan. As you can see, there is excavation of the optic nerve head. But usually a 0.5 cupping minimum has to be projected by the ultrasound. In this we can see hyperechoic edges with hypo echoic center in vitreous. This is high reflective echo with acoustic shadowing, gives a pseudo optic appearance. Choroidal is a calcified tumor. It’s made of bone, so it’s high reflective echo, which is causing an orbital shadowing. Coming to my final tip, how to report a B scan. Once you have done the B scan, we should not give a direct diagnosis. It has to be done in a systematic manner. First start with the eye reporting. This, it’s important to always mention which eye you’re doing and when position, sitting, supine, or prone, depending on the indication. As I mentioned, in gas-filled eyes you need to do it in sitting positions. Then you start from the first echo that you see in a typical B scan. You do the lens echo, or sometimes when the patient has some capsule, you might get an echo, you have to report accordingly. The vitreous, which with the cavity, you specifically mention the cavity. The patient is already — always compare both eyes. If you’re mentioning vitreous is showing a few low reflective dot echoes. Always the compare both eyes, it’s very important, especially in cases of inflammation where there are few opacities but you still suspect something, it’s important to compare both eyes. Then you talk about retina status, if detached you have to mention if there is a high reflective membrane echo extending, mention specifically which quadrants or all quadrants and whether there is a subtotal or total. Then you also talk about the choroid status and if this choroidal detachment, if it’s hemorrhagic. The optic nerve shadow, if you see any elevation. Elevation can be seen, or you can have an optic disc which shows up as excavation. And then you do the axial length, it should be done in the horizontal scan, always compare both eyes. It’s specifically important if you want to see if the length is okay. Always compare the length in both eyes. You want to decide which eye to operate when both eyes have undergone trauma, you choose the eye with better prognosis. It’s important to compare both eyes, never do B scan for just one eye and leave the other eye. Always compare the normal eye with the eye you’re doing. Two very important things before I conclude. Always interpret a B scan along with the corresponding A scan because you need to know the amplitude of the A scan spike in relation to reflectivity of the membrane. Clinical correlation is a must, especially in cases of hemorrhage, you have to see what the patient is presenting with and clinically correlate and see what the opacities are matching. These are my acknowledgements. And thank you, I hope I have made your ultrasound — understanding of the ultrasound B scan a little easier. It’s a very big topic, and hopefully I’ve covered a little bit. Thank you. >> Thank you, Dr. Mohan. We have a few Q&A questions, if you would like to stop your screen share, you can open up the Q&A. >> DR. SASHWANTHI MOHAN: Sure. So the first one is the — for that it depends on, if there is no view of the retina itself, the optical coherence tomography gives you a little more in the scans. The B scan is a very good indication for B scan, especially in opaque media but also very good indication to alert, it’s much better picked up on B scan than on optical coherence tomography. The second question is, do we perform B scan with closed or open eyes. Actually open eyes, like I told you, will give you a better scan, because the eyelids are not hindering with the ultrasound sound waives. Closed eyes is more comfortable with the patient. Closed eyes also give you a good scan, so it doesn’t matter, you can perform both ways but you have to use a liquid coupling jelly no matter what you do. Posterior staphyloma, you will see an excavation at the macula area, you can find it on longitudinal macular scan or you can see it on vertical — horizontal axial scan and you can see an excavation, a dip in the macula area. Disc drusen, I also showed you a picture. There will be a high reflective echo. It will also persist when you change the gain. And this will be a very high spike, 100% reflective spike. There will be shadowing at the optic disc. I showed you a picture, I can show it again if that’s what you want to see. This picture is an optic nerve head drusen, you can see a high spike, it persists in low gain. It typically showed you an optic nerve head drusen. Somebody asked for retinal break or tear. Yes, you can see a retinal break or tear by ultrasound but not always. Depends on how big the tear is and how big the break is. A retinal tear will look like a gap in the retinal detachment. When you see a retinal tear, you can see a gap. Sometimes it will be attached to the posterior vitreous also. You can see like a flap. And in tears you can see there’s a double linear echo with one side attached to the optic disc. Another way to see a break a little better is using a 20 megahertz one which will give you a better resolution and clearer view of a retinal break or tear and you can use longitudinal scans to give you a clearer view I of the tear oblique. Technique of using A scan and B scan, typically all the latest B scans come up with the A scan itself. There will be a vector available, a pattern available where you can make sure both A scans and B scans can be, that only gives you a complete report. Almost all will have it. So using B scan in papilledema, you can use the B scan, yes. Subarachnoid fluid, you won’t see it around the optic nerve. We need to do third degrees laterally. You have to make the patient look laterally. If there is a decrease in the size of the optic nerve by more than 5 millimeters, it’s a pseudo papilledema. Siliconized, you have to do it in sitting position or prone position. It’s not always easy to distinguish. If you can see additional membrane in the sitting position, then you might have a detachment in the silicon. If the patient is having both asteroid hyalosis and hemorrhage, it is honestly difficult to distinguish. Sometimes the particles are a little more reflective, maybe that physical way of differentiating. But it is not easy to distinguish if the patient has co-existing hemorrhage. You have to distinguish — you have to compare both the eyes, as usual. More than 0.2 millimeters difference between both the eyes, then you have to suspect one eye has increased choroidal thickness. Optic nerve head drusen can also be seen when they are not calcified. There will be a high reflective echo. Between metallic IOFB or nonmetallic, not easy to differentiate. Typically you have to get the CT scan, UFB, you need to do an ultrasound on the patient who presents you to because it is a medicolegal case. But the CT scan is the best way to distinguish between the intraocular foreign bodies. Yes, closed eyes can result in bells phenomenon with a negative result. But you will be seeing all the quadrants and you will be able to get an actual scan, we get proper axial scans. You have to keep asking the patient with his eyelids closed, look centrally, and you’ll be able to do the scans and get an accurate result in spite of that. Definitely, without closed eyelids, it is more accurate than with the closed eyelids. B scan, if you want to look for CMVN, you can use a 20 megahertz probe to look for anything in the macular area because it gives you better resolution. There are cases where we do it typically in a break through hemorrhage that we see, to see if it’s any hemorrhage that occurs. B scan in the soft globe, if there is an open injury, no contraindication for B scan is an open globe injury, unless you’re expecting a foreign body, then you have to take certain precautions. But ideally, in open globe injure, it is contraindicated. Soft globe, yes, you can go ahead and do a B scan. Best position for the patient for a good B scan is definitely a supine or reclining position except for certain indications that I told you where you will require sitting or prone position. My first question, yes, I was talking about B scan per segment, 8 to 10 megahertz, that is the answer for that question. Yes, artifacts are some things that you can see. In the field of diagnosis, for example, gas will cause a huge reverberation artifact. That’s why you need to make the patient sit in the sitting position and then do the scan. Even lens can sometimes interfere with your diagnosis of pathologies but not always. Usually you will be able to see, because the resolution is still good, you will be able to have a good enough idea of the posterior segment pathologies. So while measuring the choroidal thickness, you can’t separate the RCS complex separately. You have to measure the entire thing. And that’s the only way to measure. We have to just take the retina along with it and it’s not visible separately unless obviously it’s detached, then in choroidal thickness, you typically measure it in the papillary area and you have to compare it to the other eye. Always measure the choroidal thickness and compare it with the other eye. So it’s present in the front, that’s the echo you’re seeing after that, there will be a clear space between the asteroid hyalosis. They will settle inferiorly. So synchysis scintillans present with vitreous echoes which do not settle, yes, this can happen, there are many reasons. We always have to make sure what the clinical presentation is and then compare it, and then [inaudible]. So choroidal coloboma would be more the — the excavation will also be present and it will be more — the edges will be sharper, sharper excavation. That’s how you differentiate. Again, it’s not easy to differentiate between both. Choroidal coloboma can involve the optic nerve, that can be one of the differentiating factors. What gain is used routinely? That depends on the machine you’re using. Depending upon how your machine is set, the gain will change. The low gain and the high gain, again, will depend on how the machine is set, that will answer the question what is a low gain. So it really depends on the machine. I realize it changes between each machine, the gain settings change between each machine. So I have not covered orbital ultrasound but you can look for muscle swelling with both transfer scans which will give you a lateral extent of the lesion. And longitudinal scans. So you can do it in thyroid diseases and measure the swelling. But that was not covered in my presentation because I wasn’t talking about orbital ultrasound. But you can measure muscle thickness in ultrasound, orbital ultrasounds. The main reason to perform axial scan is, you can take a rough axial link and you also have to look for how the optic nerve looks and how the lens is and to make sure the optic nerve head is okay or not. That is one reason for axial scan. And the other reason, you are looking at — for horizontal axial scan you’re looking at macula and vertical axial scan you’re looking at the optic disc, those areas are covered by axial scan, that’s why the axial scan is important. It may not look very different from eye with vitreous in it. Any membrane, you have to suspect. Any membrane that you see, you have to look towards RD. Muscle thickness, I’ve already answered how to look for. Ultrasound orbit is a great reference manual, there is another manual by Dr. Abbas, that is also a very good manual that you can see for ultrasound. I borrowed one of the pictures, it’s a very nice manuscript. This is the one for the silicon oil, by Dr. Asha Abbas, a very good book. So vitreous evaluation [inaudible], if you’re suspecting an ophthalmitis, look for choroidal thickness, look for associated retinal detachment or choroidal detachment, these are also very important. In some cases, it may not be present in posterior detachment but also look for that. If you’re just going to give an intraocular injection, you can see how the vitreous opacities are decreasing or increasing and based on that, decide on surgical intervention. The choroidal thickness has to be right next to the optical nerve. You can find hemorrhages, it’s not always the case. Again, very important clinical correlation. So choroidal thickening, you can use it to see evidence of thickening. Nowadays with enhanced imaging, OCT and SSOCT, it gives us a good choroidal thickening, that’s the modality for monitoring choroidal thickness. B scan is obsolete for thickening unless you cannot see, unless there’s medial opacity. So intraocular lens, when it’s dropped, it will typically have elevation in the dropped area also, that’s how you differentiate between intraocular lens and fragments, intraocular lens, whatever you see anteriorly, you will see the same you can see posteriorly. I think most of the questions have been covered. Anything else that I’m missing? Some are repeat questions. The choroidal nevus, the best way to do is to look for subretinal fluid, then you have to monitor more frequently. Always look for subretinal fluid and the thickness and measure the height and the base. The nevus may not come up on a B scan because it’s relatively flat compared to melanoma. If you can pick it up, then you can follow it up that way and look for fluid and any changes in the height and posterior and lateral nevus. Any other questions? I think I’ve answered most of them, almost everything else, some of them are repeat questions. Any adjuvant, whether you’re reviewing the posterior segment and you have to do the B scan and the B scan is not giving you a clear answer and everything is distorted, and the patient is responding with no perception of light, you can do a VP. If there are waveforms remaining, especially in trauma cases, that’s a good adjuvant for especially trauma. B scan is recommended in all ages. You can do B scan at any age, depending on the indication. Again, as I mentioned, B scan is not as important for choroidal thickness anymore since the advent of OCD and enhanced OCD. Those are better things for polyps and CSCR compared to B scan. I think I’ve answered most of the questions. Thank you so much for having me.

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