As our patient population ages, there is a commensurate increase in the number and types of ophthalmic disease states that present to our offices. One of the more common is glaucoma.
Every one of us has been to conferences and lectures where various nuances of glaucoma are discussed, and we are aware of the diagnostic thresholds needed to be met to characterize an individual as having glaucoma or not. Frankly, that is the easy part. The hard part is to stabilize the patient, in the short term and, ideally, throughout the rest of their lives.
We know that the damage done by glaucoma is essentially irreversible, so improvement and structural repair is not one of the outcomes we can expect. Realistically, there are only two outcomes that are on the table for these patients: stability or progression. If a patient is progressing, whatever therapy they are undergoing needs modification to prevent further damage.
But how exactly do we monitor progression? In particular, how can we ascertain early, subtle progression? Of course, progression is seen in worsening visual fields as well as worsening OCT studies. But where exactly do we look with our OCTs to determine subtle progression?
Fortunately, there are several ways to do this. With the Heidelberg Spectralis as our glaucoma workhorse OCT, the GMPE advanced glaucoma software coupled with the outstanding image quality makes subtle progression easier to see. Glaucomatous structural damage can occur in any of three places: the circumpapillary RNFL, the macular ganglion cell layer, and the neuroretinal rim itself. Furthermore, each of these three regions also have individual sectors that can be analyzed. For example, the inferior temporal sector is often times the first to show damage in glaucoma.
Here is a good example of the utility of the Spectralis with the GMPE software: A Caucasian male has been a patient for many years, and he is compliant with his medications and scheduled surveillance. Figure 1 shows a more common method of evaluating structural change in the perioptic RNFL scans, with the current scan data (dark line) overlaying the baseline scan date (light gray line).
The damage is centered in the inferior temporal sector, and the difference between baseline and follow-up scan in this area is only 1 micron, which is pretty stable. The remainder of the TSNIT graph remains stable, but remember that we are only looking at the innermost RNFL circle scan diameter. There are three different diameters that can be evaluated, each of which is in a 360-degree pattern around the optic nerve.
In Figure 2 below we see the fellow eye’s BMO-MRW scan (essentially the neuroretinal rim tissue thickness), again, current scan compared to baseline. Note the relative stability of the current scan.
There is some variability in this scan from baseline, and the question then becomes, “Are we seeing a trend toward progression?” This is where the progression analysis of the Spectralis is immensely helpful.
Figure 3 shows the trend over time of the data points measured in the neuroretinal rim of this patient. While this image might not appear to be very flashy, the data clearly shows that the global neuroretinal rim has remained stable over the past 8 years. In the bottom right corner of this image, we can see that the particular sector selected is that of the global neuroretinal rim characteristics. With the click of a button, you can analyze each individual sector, such as the inferior or superior temporal sector.
Furthermore, on the bottom of this scan, there are four separate options for progression analysis. What we are looking at in this figure are the metrics for the BMO-MRW scans, but there are also options to analyze each of the three different RNFL circle diameter scans. Within each of those, they can further be dissected to analyze individual sectors of each circle scan.
Clearly, this patient is stable. Compare and contrast that, though, to a different patient seen in Figure 4. This image also shows the neuroretinal rim characteristics over time but with clearly identified deterioration. The deterioration seen here is specific to the superior temporal sector of the patient’s neuroretinal rim.
Having the ability to look for deterioration in many places with a simple mouse click makes for better patient care all the way around, whether the patient is stable or in need of modified therapy.
This editorial content was supported via unrestricted sponsorship.
