During this live webinar, we will discuss the best techniques and technologies used to diagnose and clinically treat diseases of the posterior segment. We will go over the optimal lenses to examine different patients from a retinopathy of prematurity (ROP) patient in the neonatal intensive care unit (NICU) to an adult patient with diabetes who needs to be evaluated for clinically significant cystoid edema (CSME). The speaker will also discuss which lenses provide the best visualization for different anatomic regions of the posterior segment at the slit lamp and also with the indirect headset, including tips and tricks to help during laser procedures like pan-retinal photocoagulation (PRP), treating horse shoe tears, and CSME. Questions received during registration and during the webinar will be discussed.
Lecturer: Dr. KV Chalam, Loma Linda University Health, California, USA
Good morning. My name is Dr. KV Chalam, I’m Professor and Chair of the Retina Services at University of Loma Linda in California, United States. This morning, I’m going to cover an area that is near and close to my heart. That is visualization of the posterior segment and various lenses we use to maximize the visualization, both for clinical evaluation, as well as for laser procedures. We’ll have around 45 minutes of lecture and roughly around 15 minutes for any questions the audience may have, so that I want to make it more of an interactive session than a monotonous one-way lecture. I’m going to start sharing the screen.
As I mentioned, this is the topic is visualization of the during diagnostic and laser procedures.
This is my place of work. And coming to the lecture itself, what are the goals today? We’re trying to see all of the retina, so let us start with some fundamental basics. How much of the retina is actually there to see and how do we measure the amount of retina visible? What are the factors that influence what we see? How do we overcome the issues of the cornea, how do we overcome the size of the pupil and how do we overcome the spherical shape of the retina, it is not a flat surface and because of the curvature of the eye, how do we work on them and what kind of utilities do we have with the lenses?
So how much retina is there? This is around 11.5 to 12.5 square centimeters. It is round in shape, more of the temporal side than on the nasal side. It is larger in surface in myopes than hyperopes,
This shows you various parts of the retinal area, inferotemporal, this is all what we want to see.
How do we measure, you know? Just want to avoid the confusion that when we see the degrees, visual angle versus the eye angle. Visual angle is the angle that has been traditionally used for like 100 years. Where do you measure the angle of seeing from the nodal point of the eye. So the maximal area that is recognized is only 170 degrees if you measure that way. You know, commercially the instrument sellers have used the visual angle and so in that situation we have 200 and 240 degrees of retina that we are saying can be seen on measure.
So a simple example. So nodal point that is basically the visual angle and the center of the eye designated by E is the eye angle.
So this is just a you know, I’m sure everybody that is listening to this webinar will relate to this picture, and we want to see the all the way in the 3-dimensional form. So what are the limiting factors for us to accomplish? We want to examine the vitreous, we want to examine the optic nerve, including the margins, we want to check the macula, we want to check the vasculature and the peripheral retina and the choroid in a 360-degree fashion.
So those are the components we want to get a glimpse of so we can diagnose and evaluate the treatment strategies including laser and other modalities.
So like in camera, one of the fundamental problems we have is, if the pupil is very, very small, the amount of area that you are going to see is going to be smaller.
Because the — any examining instrument is going to throw light in the eye and capture back the image that is illuminated by the observer. As you can see on the left-hand side, with the undilated pupil, the angle of visualization increases when you dilate the pupil.
So these are the three dimensional illustrations, as you can see here, the pupil, the larger it is, the wider it becomes. Undilated pupil, dilated pupil.
So what are the medications we commonly use to dilate the pupil in the most effective and fastest is tropicamide, phenylephrine, we need to make sure the patient is not hypertensive. Cyclopentalate, atropine, the optimal effect is usually seen with either tropicamide or phenylephrine, and the larger the dilated diameter, the larger the visualization of the area, logically.
And what are the different types of examinations once the pupil is dilated that we can perform in the clinical setting? We can use a slit lamp and you know, both contact and non-contact lenses to get a glimpse of the either the macula or the retina, depending on what we want to accomplish.
The second or maybe the third one is the binocular indirect ophthalmoscopy, where you are basically having a lens between you and the patient and with the ability to go around the eye and examine various areas.
Argumentally with the binocular indirect ophthalmoscopy, you get a better view, whereas the slit lamp you get one view.
Those are the advantages and disadvantages of both modalities. We’ll go over one by one and the various lenses you can use and the tricks and tips.
So the types of lenses you can use, you can have the contact lenses, you know how important the lens I am describing here. You have noncontact, convection lens, concave lens, Hruby lens, which we don’t use very much anymore. Indirect. So let us go back to the simple optics of what actually is happening. So fundamentally you need to have light that is thrown into the eye, otherwise you can’t actually see.
The light source then passes through a biconvex lens into the eye. Then the image is captured back with the binocular lens again, between the examiner and the patient and so there’s a fundus picture.
So we use the biconvex lenses and I’m going to go into the specifics of the various lenses.
So the types of images: So you can get a direct image or an indirect image and often the indirect image is what we get.
The direct image, as you can see is you see the disc and the macula the way it is. The indirect image you have to compute mentally and reverse it backwards for you to administer whatever treatment modalities one may plan.
And the second thing is what kind of lens design we want to have? The simple is basically bi convex lens. As you go away from the sample point, you tend to have both climatic and spherical distortion as you can see like a battle ship right here. What we mean by that you’re continues will you changing the radius of the lens from center of the lens to the periphery and so when you do it on both sides, then the distorted image of the spherical nature becomes undistorted and that’s what you really want, as much as you possibly can, when you’re both examining, as well as treating the patient.
So you know, how do you — there are four ways of competence we want to pay attention to. Obviously it is examiner. The examiner should be good at knowing the correct working distance, steady hand and eye coordination, flexibility of the wrist and the systemic methodology of examining in a sequential fashion, and make it secondary nature. As far as the illumination is concerned, the brighter the intensity, obviously the more you can see, but you have to be careful about two things: The brighter the intensity, the higher the intolerance of the patient, the brighter the intensity, the more annoying would be the reflection of the lens you would be places. Because remember you have the front surface of the lens, back surface, the corneal surface and maybe the intraocular lens. So you have four reflecting surfaces coming back at you unless you are interrupted separating the illumination pathway from the human pathway.
The third is the lens. The more high quality it is the better, the more as stratospheric it is, the better and the second is the antireflection coating. This is basically the coating placed on both sides of the lens. So that way it neutralizes the reflections that are coming off.
And lastly, of course, the patient, cooperation, the gaze and fixation on you know, responding to the commands of the examiner and lastly, the corneal surface is the most important thing, it cannot be dry. You know, that impairs the quality of the image that you’re getting back.
And lastly, pupillary dilation, we already mentioned and of course the clear media.
So let us start with the simple thing, which is basically direct ophthalmoscopy, a lot of us carry in your pocket when you’re going around. The advantage, are it is clear, it is very highly magnification, but the most important advantage is its field of use is very small. Even in the most delighted pupil you can’t really get a large amount of area to affect the visualization, stereopsis is not that good either.
Illumination in the hand is throwing the light and at a 45-degree angle put the light into the patient and the image you’re trying to get back. Of course the separation of the angle of illumination from the angle of — that basically gives you the image.
So you can examine especially the posterior part of the eye, the disc and the macula are fairly usually visualized, but beyond that it’s a fairly hard thing to get a good view.
So that leads us to indirect ophthalmoscopy, which has been available since the 1960s, it is an instrument you carry around and the batteries are already incorporated so you don’t have the boxes to carry anymore and this is the brightness knob, and of course it’s binocular so you can have two viewpoints from which you can see. You can also control the size of the light so that you can in a small pupil to get the illumination path and the examination path separated.
So what are the optical principles behind it? S fairly simple. So you have the observer, you are putting the lens in between and throwing the light so the area that is illuminated is going to come back and form a clear image between the observer and the patient.
And so there are four lenses we normally use. You know, commonly practiced and as a compromise is usually a 20 diopter lens. One of the problems is the smaller the diopter, the larger the wavelength, the focal length.
So the area for you to hold the lens in the air is not particularly easy, so we normally compromise it to 20 diopter lens. You’re in perfect visualization with the +20. Of course, the +30 is even more easier to hold, but the image size is smaller, and so details may be difficult to view because of that.
And then we’re going to perform an indirect ophthalmoscopy examination in a systemic fashion, you always start with the superior part, you see in the temporal and then the inferior, and then nasal.
So make it a routine that you follow this systematic clockwise fashion so that way no areas escape. Remember, we have to comprehend in our brain what actually is image for us to come to a complete conclusion of the pathology or otherwise.
So this is basically a comparison graph showing the field of view that you see on the horizontal and magnification that you see on the vertical.
14D is and 20 is in between and 40 is the biggest field, but much more balancing act. But for routine practice, the 20 diopter is a compromise easier to carry around, unless you have something like this the choroid where you want to magnify few, like in 14 diopters, as I already mentioned, one of the problems with the 14 diopter lenses, you have to hold it in the area and try to have the patient, the lens, and you, in a longitudinal fashion, which is sometimes difficult for an untrained person.
So the second thing that I mentioned is the reflective images because you’re going through two surfaces of the lens, and the cornea, as well as if somebody has an intraocular lens.
So one way is to tilt the lens to avoid the glare and the second way is the basically anti-reflective coating on either side, so it neutralizes the illumination coming back and as you can see from the left-hand side to the right-hand side, you don’t have any reflections.
This becomes really important, because the more illumination you use, especially for a medial opacities, the higher the reflection, so one has to be cognizant of those things.
so what are the advantages and disadvantages? Of indirect ophthalmoscopy? Produces an inverted reversed image. But the magnification is 2 to 5 times magnification. It is called indirect because of the use of condensing lens to view the fundus, and …
So as a result, larger fields of the retina can be viewed. Retina anterior to the equator can be examined, 3D stereoscopic view of the retina and good depth of focus and …
So what are the lenses? We already mentioned them. So I’m going to one by one. This is a 20 diopter lens that is most commonly used in clinical practice. One other thing I did not mention is the diameter of the lens. In the manufacturing process, higher the lens power, the more difficult to make the, so that’s why you see the 20 diopter lenses to be larger in in diameter. So the 20 diopter lens is a double aspheric lens, magnification is roughly 3 times. Field of view is 55 to 65, or 60 degrees. Of course, the field of view is also dependent upon the pupil dilation. The larger the dilation, that’s why you have the dynamic range, rather than one just one particular number.
So it has to be held roughly 5 centimeters from the patient’s eye. That’s why I was mentioning, if you use 3 fingers together and hold it on the forehead it becomes easy.
The second indirect lens is the 28 diopter lens. Extremely useful in pediatric had examinations and also the noises when one starts the ophthalmoscopy learning, it can be daunting in the beginning to be holding a 14 or 20 diopter lens, it can be difficult to make it still. So start with the 28 diopter which is easier to hold and also get a much larger view of the retina and then you can learn the skills after the practice of it.
So the downside is of course, the magnification is less. It only magnifies 2.2 roughly. And the field of view, however, is larger, 70 degrees.
Easier to view pathology and in the periphery, especially in the postoperative cases or if the patient has —
The 30 diopter is not really that different, 30 and 40, just put for the comprehensive sake. Just a picture of the same issues.
So as I already mentioned earlier you want to perform in a clockwise examination, you need to be also alert to which hand to use depending on which eye you’re examining, you know, left eye for the left eye and right hand for the right eye and start in the clockwise fashion, you start close and you bring it to you until you get an image and once you get an image, you basically hold on to that and continue the examination.
So sequence of how do you go about it, patient should be placed in a reclining chair and reclined until the patient lies flat or parallel to the floor. Light beam from indirect should be a straight line to get a great image. And using the indirect lens, view the posterior pole to examine the optic nerve and macula and then go to the periphery until you get it. I’m also referencing a YouTube video which I don’t have time to go on the video to show you, but if you’re interested, it is there, and you can look at it. It is basically a five, six-minute video of various phases of indirect ophthalmoscopy.
So here is a comprehensive set of photographs. As you can see here, you can see, start in the center, infratemporal, temporal, you know, this is the posterior pole, and the superior part of it. So this gives a picture of all the areas you can see, and these photographs were taken with a 28 diopter examining lens.
So one other agent that I have not mentioned is a scleral depression as I alluded earlier. Viewing is fairly easy and it gets a little tricky to get the peripheral retina, which is anterior to the equatorial region. That is where the scleral depression comes into picture. As you can see on the left-hand side here is an examination of a normal peripheral retina. On the right-hand side you already have a scleral buckle with basically scleral depression.
So the how do you examine the peripheral retina and what are the tricks? One thing you have to be careful of is when you’re dealing with a scleral depression, you’re rising the intraocular pressure which makes it fairly uncomfortable for the patient. So you stop and systematic just like in ophthalmoscopy and the try to and that is how you look at it. Nasal will be more difficult than the temporal and superior and infratemporal tend to be easier for the scleral depression.
So here is an example of a horse horseshoe tear.
And with the horseshoe configuration as you can see here and luckily there isn’t much detachment here, so it is amenable to treatment and so we’re doing an indirect ophthalmoscopy. So a laser basically focusing on the left-hand side, we’re using laser retinopexy as you see here.
Use the indirect lens, 20 to 30 diopter depending on whether or not you have a scleral depression. Bring in the area of interest, adjust the power duration and interval depending on the spot size of the laser. Especially the anterior part of it is where you need to be focusing to get a good retinopexy.
So here is an example of a freshly done, this is two tiers here, here is one and this is one. This is a retinopexy being done.
So what about the kids? Pediatric patients, including in the NICU? As you can see in the bottom, you can change the size of your illumination, the largest to the smallest, so if your pupil is not really dilated you go to the smaller illumination size. Larger when the pupils are very well dilated. It’s an important thing, especially in pediatric patients.
So here is an example of an examination in the intensive care unit, we ophthalmologists are often called to monitor. So proper dilation and anesthesia is the key to successful examination of infants. We often use often cyclopentalate, 5% to 1% placed 10 minutes apart 3 times to get adequate dilation.
And sterile speculum is placed in each eye and pediatric depressors are used separately in each eye.
So usually 28 diopters is the one I normally use. Adequate positioning with the help of the support staff is important. So without that, it’s very difficult to do this.
We use pacifiers or oral sucrose for the infant and careful examination you need to perform.
So here is an example of retinopathy of prematurity. You have + disease and angiogram showing toughening of new vessels, nonperfusion versus perfusion, in which case we basically do the laser treatment, which is shown here, basically the laser spots here, a little bit of hemorrhage beyond the area of perfusion. As you can see here, it is basically contiguous to each other and three months later you can see a nice scar formation.
So now let’s move on to the slit lamp based contact biomicroscopy. As I mentioned, you have noncontact lenses and then you have contact lenses, I’ll try to describe various lenses we use, the rationality and optics behind them and in what situations they’re more relevant.
So slit lamp stereo biomicroscopy, you can see from the antero lateral segment as you can see here, but most likely the vitreous as well as the retina.
Here are the examinations of the anterior, then you have the vitreous and of course, the posterior segment, you can move the slit lamp back and forth from the anterior to the superior, you can concentrate on various parts of the retina or other parts of the vitreous cavity.
So you don’t want to be too close or too far. Obviously how do you know that? If the peripheral retina is not illuminated, you’re too close. And if it is loss of field of view, you hardly see anything, then it is basically you’re too far,
The correct distance illuminates the entire pupil and you can get a very precise view of the retina so that’s very important. And especially when you’re starting out, this can be a little challenging until you get used to it.
Classic example of a 90 diopter lens examination.
So patient is positioned appropriately at the slit lamp, illumination angle. This is one important trick in this is you try to separate the area of illumination angle from area of examination. Of course this becomes difficult in a small pupil, but the larger the pupil, the fundus visualization is much better in the reflected light than on direct light, because if you do a coaxial examination, you — so try to dilate the pupil and try to keep the illumination angle very separate. The larger the angle, the more comfortable the more area, you would see. you try to decrease the area of illumination, and of course you have the magnification that is really key of the slit lamp and good optics of a slit lamp will be 10X or 16X depending on what slit lamp you use.
So this is a comprehensive optics of the system. Patient’s eye, you’re putting in your contact lens, this is the slit lamp you’re watching it here, so the distance the amount of area you’re going to see, and I’m going to go into the various lens and the optics of individual lenses.
So there are usually four lenses that are available, starting with a 60 diopter, roughly remember the diopter of a normal human eye is 60 diopters, so it measures basically 1 and you have a 66, a 78 and a 90. As I mentioned from a manufacturing point of view, the higher the dioptic power, the more difficult to make. So you tend to have the small diameters as the power goes up.
So here again, the cartoon that I mentioned earlier, the field of view you would get affects the magnification. 60 diopter, you get the higher magnification, but the field of view is less. And whereas with the larger lens, of course the magnification can be compensated by your slit lamp, so that is the advantage of biomicroscopy.
So this is a group of lenses, I’m talking basically 60, 78 and a 90 diopter. This is performed at slit lamp, can be performed with a dilated and dilated pupils, stereopsis is basically good, and field of view is greater than indirect lens.
Most commonly used is a 90 diopter lens. Magnification is.75, around 7mm in front of the patient’s eye, so this can be a little tricky if somebody has deep-set eyes, so you have to be careful of that. And angulation is very important to get a good view. It is 26mm diameter basically.
So to ask the patient to look below and above, you get a little bit better view.
It is not 97, sorry for the typo. Magnification is roughly .9 and working distance is 8mm.
The third option is 60 diopter lens, obviously gives you much wider view and the diameter of the lens is roughly 31mm, so it gives you a wider field.
So my favorite lens is basically 132 diopter, we call it a super pupil lens. The advantage of it is you can get a very good view through a very small pupil or with a complicated cataract, this is a good lens for examination. The reason is the amount of the diopters. Magnification is smaller, but you can use slit lamp to get rid of that. Working distance is 3mm, good for dynamic funduscopic examination, saves time.
Now, moving on from noncontact to contact biomicroscopy, it’s very important, but especially in performing the procedures, the contact biomicroscopy eliminates the problems you may have with a corneal surface. It takes a little longer, but on the other hand if you want to focus and get the details, especially of the 3D relationships between the vitreouses and the retina in various parts of the fundus, so this is the method of choice. Wider angle of visualization, you need a coupling agent, it is stabilization of view during the laser procedures, so it won’t allow the movement of the eye, which is really vital when you’re doing intraventional treatment.
The dilated pupil, the larger the dilation, the better the view. The 3D are better much visualized with this procedure.
Again, this is the optics of the system. Once we have the contact lens, the images basically come as a surgeon or examiner you basically look at the end of the slit lamp.
So where does the image form? Because of the contact lens as you can see the amount of area you see is much, much wider, and then the image forms in front of the lens. Which you then capture through your biomicroscope and visualize that.
So the common lens I normally use is basically 130 degree quadraspheric lens. Antireflective coating, it reduces astigmatism across the corneal surface and the lens itself. the laser spot magnification is roughly 2 times and the image is half the size of aspheric because the lens is roughly 150 diopters in terms of power.
So one way to get around the size of the quadraspheric lens was a high refractive wide field lens. The same 150 diopter lens can be made much smaller in size, so this is a lens that is also because of the weight is also reduced, and the parameters are more or less the same. It produces 2 times the magnification, and then the image is half the size:
The next one is a super quad photocoagulation lens. You have to be careful with people with deep-set eyes, this may be difficult to hold for a longer period of time during procedures.
The next one is a transequator lens. It is in between the macular lens and the quadraspheric lens. Roughly gives you 110 degrees. Good for focal laser, you have to make sure you’re not shooting the macula.
Laser spot magnification is 1.14 and image size is .7.
The macular photocoagulation lens. 70 degree area. It is one to one image, so you have to look at the spot size, you don’t have to change laser spot size for the lens. Again, the higher the magnification, the higher the height of the lens, which makes it difficult to hold on the lens in perpendicular fashion for a period of long time in the slit lamp area.
This is a comparison table of magnification of area centralis, the Mainster is the other manufacturer you have, and here is a table comparing lens heights, as I said, the larger the height, the more difficult to hold, so you have to be careful about the area of examination, both static and dynamic.
So we are now going into the laser part of it, which is diabetic retinopathy which is one of the most common things we as retinal surgeons do.
In the center, you have the nonproliferated diabetic retinopathy with macular edema, and on the right side you have some vitreous hemorrhage. So all of them obviously need a treatment. So what are the lenses we use and what are the sequence of events we basically do? So I normally use a super quad lens and a transequator to provider the largest field. Then you change to the super quad lens for the various quadrants. I normally try to do them in four sittings and when I do, and when I do, I usually start with the transequater and move to the super quad.
The biggest advantage is unlike in binocular retinal laser, here you have the control of the patient eye movement so you don’t catch the macula inadvertently, so that’s the greatest advantage.
So here is the first part of the treatment where you’re using a transequator lens, you can see the large dots here, and the last one is basically after the completion of the pan photocoagulation.
A mow for the macular edema, you need to confirm with either an angiography or OCT. Use them as cues to exactly where you want to place your laser, if it is a focal laser or your fundus photograph as a guide to being the laser itself.
So the macular laser, as you can see, this is an area centralis. Goniosol is used as a coupling agent. Magnification and detailed view macula can be altered by the slit lamp application that you have. And focus fluorescein at various wavelengths.
He also used to do macular laser with age-related macular edema which we don’t do that very much anymore. The laser can be applied effectively and eliminate the need for prolonged use of the anti-VEGF agents.
So I’m coming to the conclusion of the lecture. So what are the lenses I use? I’ve given you a description of the plethora of various things that are used in the market. I normally use a 20 diopter for the examination part. For a routine examination.
Use a super pupil XL in the clinic for visualization in the slit harm and I use a digital wide field lens for the macular because of its antireflection coating which is spear your.
As for the lasers, my two favorite lenses are the transequator, because it’s kind of a compromise between the area centralis, gives a good stable view and also protects from inadvertently using damage to the macula.
I use the quad R aspheric, for when you put a quadraspheric, sometimes it may be difficult to actually see until you get the initial view. So you put your slit lamp in a thin beam and a small beam and try to get the glimpse of the fundus. Once we get it, it’s very easy to then hold on to that and expand the magnification and examine the various parts and deliver the care that you really need.
I think that concludes my my lecture and now the next 15 minutes for any interactive questions that I’m happy to answer.
>> Lawrence: Perfect, thank you Dr. Chalam. We have a few questions if you want to open the Q & A screen next to the chatbox.
>> Dr. Chalam: OK, all right. So let us start answering the questions. So examination methods along with chart testing, inadequately detected: (Indistinct)
I’m not sure what the question was. Yes, it is true, you know, it is basically clinical examination, you start with the examination, then you use your clinical examination with various lenses to figure out what’s going on, then you implement various tests to conform or refute what you thought you saw. And routinely used these days to evaluate the macula, and of course you can get a wide-angled field and you also use a — 20 hertz to confirm what we thought was there.
So the next question (reading indistinctly)
So the — I would think probably most of them have ophthalmoscopy. What you’re trying to realize is before you call the ophthalmologist, I don’t know, whether it is an eye care provider, you’re trying to figure out if there is any papular edema, and at least most medical students in the United States are trained on, and of course after did have after, then they do the examination that we talked about earlier.
So the next question is. If I want to purchase only two lenses for PRP, which should I purchase? I would
I would probably buy a quadraspheric lens and a transequator lens, those are my to-go lenses, because the transequator gives you great magnification, but to start the in the posterior pole area, follow by quadraspheric lens, if lasering the four quadrants.
The next question was: What is your preferred systemic fundus ophthalmoscopy and which quadrant first?
Well, I start always with the posterior pole, you know, because I can recognize the relationship between the disc and the macula, and then after that, I basically go to 4:00 and as I describe in the lecture, go in a clockwise location, 12:00 starting in the equator to the periphery, and if it is a right eye, it is 3:00 next, which is basically the nasal side, then 6:00, which is the inferior, 9:00 which is the temporal side. That is how I go in a sequential fashion.
The next question is: Do you do scleral depression directly or to — eyelid? I do the scleral depression with the eyelid. Doing it directly is extremely painful. Especially of course during surgery, I do directly, but not in the clinic. In the clinical setting I do through the lid margins. I try to avoid the tarsus, so that when you try to get the scleral pressure you avoid the tarsus, that gives you posterior to the equator to the anterior, and by manipulating away from the globe, you know, you start perpendicular and you manipulate away from the globe and then you go in four quadrants, sequentially starting clockwise.
I think that’s the questions that I have so far.
>> So Chalan, if you scroll down there …
>> Oh, I got you. The next question … (reading indistinctly)
I think it’s basically a comment rather than a question here. So yes, you know, I agree with what is being said here. And of course, it really depends on the underlying pathology, it’s not like one area, so we have to see what the underlying pathology is, then obviously modulate the treatment based upon that.
Obviously is a destructive procedure, so you basically don’t — you always leave one spot in between the spots, so that way the peripheral visual fields are not really affected badly.
So let me see, …
The next question is, please when I use 200 microns more, the effect of laser energy is very poor and.should I use a special lens for better effect? What would you advise for this? OK, so the if you use area centralis, this is 200 microns more is not the absolute, because is it modified by the lens is that you use? For example, if you use a quadraspheric lens, you’re half the size, right so your 200 microns on your laser machine becomes roughly 400 microns if you use a quadraspheric lens, if you want to get a one-on-one, then you have to use the area centralis, which is basically your 100 microns more is 100 microns more. So there are three things you can do, either you can increase the energy itself, or you can decrease the laser spot size, and so depending on the clinical situation, that’s what I would do.
So the next question do you have any tips for — in predisposed patients? Very good question.
So in these cases basically use teardrops before you do, difference between you’re doing a noncontact examination or a contact examination. If the patient already had some amount of corneal edema, I would use glycerin drops in the clinic, because it desiccates the cornea — and it’s actually useful especially in patients who may have high intraocular pressure or in cases where they’re already predisposed.
Once you do that, then you want to keep your examination to very short time. So you need to be specific in what you’re doing and try to do that as fast as you can. So that would be my answer for Dr. Hamad Samir.
So the next question is, is there a standard lens for chain of retinopathy of prematurity and secondly how — (reading indistinctly.)
Again, this is variable. My go-to lens is a 28 diopter lens, it is a good compromise between magnification and being a large area, so I don’t want to spend too much time doing the examination, because you already had the patient’s eye open, you need to make sure the cornea is reduced in a glare basis, so you don’t loss the visibility.
So examination often depends basically on the scleral depression and the sclera tends to be much softer in a neonatal than in adults and because of that it may be much easier to accomplish. Yes, I do scleral depression to [unclear]
What are your recommendations for presentation of condensation and review in case of a facial mask? Another practical question. I tend to have basically a paper tape placed on the nose of the patient, so that the air from the nose doesn’t come between what you’re examining.
These days of using the facemask, put the tape on the facemask and so the nasal air doesn’t come to the eyes and make it away from the eyes.
Lenses are used for capsulotomy. You know, I normally use — if I do I use a lens called a Krieger lens, that is basically a direct ophthalmoscopy lens. It causes a direct image and you go from anterior to posterior and it stabilizes the eye so that the eye does not move. So it’s called a Krieger capsulotomy lens.
Thank you for your lecture. Yes, you know, the time is a constraint covering a large area so I couldn’t do all. We used to do drawings in the past. We don’t do that as much in the past. Because of the contact lens biomicroscopy, you can actually see the whole retina in such an easy way.
Which lens would you prefer during [unclear]
The lenses I use I use a flat lens. So I use a flat lens for the — to start the case. Then I use a miniaturized SSVXL. That’s what the lens I normally prefer. It is a miniaturized aspherical lens. But I also use so to summarize the answer to your question, a flat lens to start the case, a noncontact lens, either a Merlin or a Sight, and then for contact I use an SSVXL.