Dr. Weinreb: So, I’m going to be talking about spectral OCT and is it ready for glaucoma management

Some of you probably have these instruments. Some of you are considering having these instruments. My message this evening is that the technology is changing. It’s advanced to the point where I believe that it provides an essential component for glaucoma diagnosis and detection of glaucoma progression

Many of you are familiar with the glaucoma continuum. Glaucoma is a continuum where you go from undetectable disease ultimately to asymptomatic disease, and some patients progress through the continuum to functional impairment. And, the continuum begins with acceleration of retinal ganglion cell apoptosis

And, in 2011, our current practice is to stage the disease and predict loss of function, and we stage the disease by basically deciding where on the continuum a patient falls. We predict loss of function doing risk analysis, looking at some of the risk factors for glaucoma, including intraocular pressure, age, condition of the visual field, condition of the optic disc, and also central corneal thickness. And, as we continue to learn more about risk factors, we’ll be able to better predict loss of function

However, one of the questions that often is posed is should we rely on structural testing or functional testing, and one of the important messages that I want to deliver this evening is that we should be relying both on structure and functional testing. In fact, structure and function are complementary. We need them both if we’re going to diagnose and follow glaucoma

And, the state now of technology and the state of our software has sufficiently advanced so that, for the first time, we’re able to combine structure and function in one printout in order to better manage our patients

In my opinion, the stereoscopic optic disc photograph is still the gold standard for detecting structure progression in glaucoma. However, it’s time-consuming, it’s impractical, and as most of you know, the state-of-the-art technology for it, which is a simultaneous stereo camera is not generally available. In fact, most of you do not have a digital simultaneous stereo camera

I perform photographs in my own practice at baseline, which means when I first see the patient and then if I suspect there might be a change, I might obtain photographs again to compare with the baseline. But, in general, at this time I rely upon my imaging, and I’m relying upon my imaging with the HD OCT

Imaging allows all of us to be experts. It allows expert examination by non-experts. If you’re someone who has spent a career learning how to assess the optic disc and detect progression, you don’t necessarily need sophisticated technology. There are probably less than a handful of people in the world who are experts at examining the optic disc

The high specificity to detect outside normal limits on retinal nerve fiber layer, optic nerve head and macular examination is now available, and I’ll be talking about some of the new technology that allows us to do that

As we move forward from 2011, in addition to staging the disease and predicting loss of function, we also need to detect progress, and typically in the past this has been an event-based analysis, and that means we look at a patient and we say has there been a significant change in that patient? Has there been an event that is now detectable through our clinical examination

The new technology allows us to do something that’s much more powerful than an event-based analysis. It allows us to do a trend-based analysis. In other words, it allows us to measure the rate of change to estimate the likelihood and expected severity of functional loss. All of you are already doing this with your visual field examination. Most of you are using the Humphrey Visual Field Analyzer, and most of you probably like--if you’re like me, you’re using the VFI technology and you’re using analyses like GPA to determine whether there is a change in the visual field

The same types of analyses are available now with the HD OCT, and I’m going to show you some of those analyses. The GPA on Cirrus can confidently measure the change and the rate of change of structural parameters

There are a number of advantages with imaging. Imaging acquisition is relatively easy. This allows us to do more frequent exams. Imaging is more reproducible than we can possibly do with our subjective evaluation of stereo photographs. And, imaging allows clinicians to make earlier and more informed clinical decisions

Here’s a case example of a patient that we’ve seen in my practice. On the left, we’re looking at a patient with a large optic disc who has a very thin rim, and if you look carefully, you might be able to see a retinal nerve fiber layer defect here. This patient has severe visual field loss

On the right we’re looking at an eye, also large optic disc, but it’s not quite as clear that this patient has glaucoma. It just might be a large optic disc with a thin or narrow neural retinal rim. The visual field also isn’t too bad

But, here you look at the HD OCT and you can see, in that same eye that we--the visual field was not that damaged, you can see there’s extensive loss of retinal nerve fiber layer thickness here, and you can see it also very nicely in the thickness map

Imaging also allows clinicians to measure features not otherwise possible. One analysis that has been increasingly popular because of its sensitivity and specificity for detecting glaucoma and glaucoma change is the ganglion cell analysis

Well, what is the ganglion cell analysis? In order to understand it, we need to talk a little about the anatomy of the macular and the optic nerve. The retinal ganglion cells number about 700,000 to 1.5 million, about 1 million retinal ganglion cells, and you know there’s about 1 million retinal nerve fibers. The nerve fibers are the axons of the retinal ganglion cells

The density is greatest in the macular, where the retinal ganglion cells can be six cells deep, and 50 percent or more of retinal ganglion cells are located in the central four and a half millimeters. And, this area is represent only about 7.3 percent of the total retinal area, but the retinal ganglion cells in the macular are lost in glaucoma

So, even though it’s a very small area, there’s a very large concentration of retinal ganglion cells there, and by assessing the macular, we can detect changes in the retinal ganglion cells, their axons and their dendroids

Well, how do we do that? Well, the ganglion cell complex consists of the nerve fiber layer--the innermost layer of the retina--and the retinal nerve fibers are the axons of the retinal ganglion cells. The ganglion cell layer and the inner plexiform layer of the retina--the inner plexiform layer is the dendroids of the retinal ganglion cells

With HD OCT, we can look at the thickness of the retinal nerve fiber layer, the ganglion cell layer and the inner plexiform layer. As you lose retinal ganglion cells in glaucoma, the complex begins to thin. It begins to diminish

Available now with the Cirrus you have ganglion cell analysis. Here’s a depiction of the new software. On the left compared to the right, you can see a loss of retinal ganglion cells depicted here with the color coding, just as you’re familiar with the standard examination of the peripapillary retinal nerve fiber layer

Imaging also allows clinicians to have an objective measure of progression. And, again, before, our measures were subjective. Here’s a terrific example in--right out of a manuscript that I published with Professor Christopher Leung from Chinese University Hong Kong. What you’re looking at here is a series of HD OCT Cirrus images, and on the top you’re looking at the peripapillary retinal nerve fiber layer thickness. Here you can see the color-coded thickness map, and here you can see the same patient imaged at the same time with the HRT

Interestingly, in this particular patient, if you look at the change over time of optic disc topography with the HRT, there’s virtually no change at all. You can see with the Cirrus, the retinal nerve fiber layer began to change very, very early, and you can see progressive changes here that are highlighted in the thickness map

With new software, one can look at the thickness of the retinal nerve fiber layer over time, and you can do the type of trend analysis that we do with visual field testing

Here’s another example, a 31-year-old male who was followed over time. In this particular patient, we’re looking here at the visual field test and the change over time, and you can see the visual field isn’t changing very much at all. But, yet, when we begin to look at the thickness map over time, you can see clearly that there’s changes in the retinal nerve fiber layer even though we’re not yet seeing changes in the visual field

So, this new technology not only measures rate of change, but is very sensitive for detecting change, something that’s critical to our practices

And, then the third case is a 75-year-old male, and in this particular patient--again, the patient was followed serially over time, and what we’re looking at here over a series of different visits is we see progression, progression of the retinal nerve fiber layer, and you can also see progression of changes in the optic nerve head because we’re now able to objectively assess the optic nerve head

Imaging allows us to obtain data that are digital. The data are objectively processed and analyzed, and they can be exported to an electronic medical record for analysis and storage. The new forum software can store patient data in one location and electronically bring all patient records to the point of care

So, what does that mean? So many of you have already converted to electronic medical records. Those of you who haven’t will--many of you will be converting over the next year or two. And, for those of you who have not converted or are not going to be converting in the next year or two, there’s no question that you’ll be converting over the next five years.

And, it doesn’t matter whether you practice in Iowa, in San Francisco, in Hong Kong or somewhere else. Electronic medical records are our future, and here’s one reason why. I mean, an electronic medical record provides seamless integration of the medical record. It allows us to have a dynamic, flexible view, to store all the data that we acquire. Our instruments can become connected, and then we have end-to-end bi-directional communication among the instruments

And, perhaps most importantly to glaucoma, it allows us to combine data. Structural and functional data, as well as other data, can be combined

Here’s an example of new software--again, available with the Cirrus--that allows us to combine the visual field with the assessment of the retinal nerve fiber layer, the optic nerve head, or the ganglion cell analysis. We can put them on the same printout, and that’s something that you can have available in your office either on a video monitor or as a printout

Imaging allows rates of progression to predict who is the highest risk of functional impairment and blindness. Remember, we need to allocate limited resources for glaucoma management to those patients who are most in need, and we do that by determining who has the highest rate of progression

Here’s one type of analysis that we’ve developed at the Hamilton Glaucoma Center at University of California, San Diego. It was developed by my colleague, Felipe Medeiros, and this uses a Bayesian analysis, a very complicated mathematical analysis to combine structural and functional measurements to obtain a view of the data that’s not otherwise possible

On the left, we’re looking at a series of visual fields in a patient that initially seemed to be getting worse over time, over several years, but ultimately the visual field looked very much at the end like it did at the beginning

There’s no statistically significant difference in the visual field here and here. And, if we rely just on analyzing the visual field, we’d say this is a patient that hasn’t changed

Here you can see serial optic disc photographs, and we can see serial GDX as well as the visual fields. Combining all these data with a Bayesian analysis, we find that even though there’s no statistically significant change in the visual field, when we put all the data together, we see that the structure function of the patient is significantly changed. This is a patient that clearly has progressed and we need to advance therapy. In this particular patient, they’re on maximum medical therapy and they need surgery

In addition, when we look at a group of patients, the analysis allows us to detect more cases that are progressing with similar specificity. This is one type of analysis, and there are many others that can be done, you know, once we have the data in a digital format being stores and being able to be analyzed in our electronic medical record

Both the World Glaucoma Association consensus initiative and the American Academy of Ophthalmology preferred practice patterns now recommend imaging as part of routine clinical care. However--and this is a big however, because you need to be aware of these points--there are some caveats

Imaging alone is not 100 percent accurate, so still we rely on our good clinical judgment and all the clinical information that we’re acquiring with our slit-lamp exam and everything else that we do. The assessment of quality is very important, as poor quality is susceptible to artifacts

And, then there are these atypical patients that when I see them in my clinic, I just throw up my hands and don’t know what to do. These are typically the high myops or tilted discs. These are patients that are not in our normative database

And, normative databases may not be representative of all patient populations. They’re also based on statistics, so there’s always a low probability that a patient outside normal limits is just a normal at the low end of the distribution

So, in conclusion, is this technology ready for glaucoma management in practices? Well, with all the new technology being introduced and the experience now of using these instruments over several years, in my opinion, the answer is an unequivocal yes

Thank you