This article was originally published in a sponsored newsletter.
There is no question that the utilization of OCT technologies has transformed our ability to render earlier diagnoses and treatments for patients with a variety of diseases. However, with increasing technological advances, it can be difficult to keep up with incorporating such technologies into our offices. More equipment generally translates to more occupied square footage in the office, so we should remember to keep both space and cost in mind when selecting new equipment.
One of the many benefits to the Spectralis platform (Heidelberg) is its variety of imaging capabilities that are needed on any given clinic day. Of course, OCT is paramount on this list, but other functions, such as fundus autofluorescence, OCT angiography, the glaucoma module premium edition (GMPE) software and multimodal imaging are just as useful.
Take, for example, this case of a 68-year-old Caucasian female with advanced glaucoma in both eyes and a pronounced epiretinal membrane (ERM) in her left eye. As you can see in the multimodal image in Figure 1, the ERM is readily evident and is representative of what we would see in vivo. The Spectralis multi-color imaging system uses three separate wavelengths of light to image the posterior segment. Each wavelength highlights different areas of the retina, from the choroid (infrared) to the deep retina (green) and the retinal nerve fiber layer (RNFL; blue). Note the pronounced ERM, the significant loss of RNFL in the inferior temporal (IT) sector and the significant glaucomatous cupping.
Of course, with glaucoma patients, it is imperative that we periodically scan the regions of the posterior segment that demonstrate progression of glaucoma so we can initiate therapy modification if we see progression.
One of the significant image areas in the context of glaucoma is the circumpapillary RNFL. In this case however, there is notable loss of RNFL tissue in the IT and superior temporal (ST) sectors of the perioptic RNFL, and furthermore, the temporal RNFL is affected by the ERM. It is not uncommon for ERMs to change configuration, especially in the first 6 to 12 months of their development, which makes detecting glaucomatous changes in the RNFL difficult to discern from changes due to the ERM.
This is where our macular scans are helpful. When scanning the macula for glaucoma, we can view either full retinal thickness or ganglion cell layer thickness. Not surprisingly, when there are ERMs such as this, total retinal thickness will be significantly altered, making interpretations related to glaucoma impossible. Therefore, it is best to use the ganglion cell layer scans in cases like this because the ganglion cell layer is less influenced by ERMs than total retinal thickness, as seen in Figure 2.
Note in Figure 2 that there is still some distortion due to the ERM, especially in the perifoveal region, but the IT and ST sectors of the ganglion cell layer (especially the IT sector) clearly show thinning associated with glaucomatous damage.
Lastly, we can image the optic nerve itself using the GMPE software to evaluate the Bruch's membrane opening minimum rim width (BMO-MRW) measurements in the neuroretinal rim, as seen in Figure 3.
While the RNFL circle scans in this patient do not give us accurate information as to the stability of the glaucoma (because of tissue alteration due to the ERM), the macular ganglion cell layer analysis and the BMO-MRW analysis do give us great information related to glaucoma without the confounding interference from the ERM. If the glaucoma worsens as we follow this patient over time, the loss of tissue will be seen in the latter two scanning techniques and not the RNFL scans.
Previously, we would have to go to different instruments to obtain this variety of images. With the Spectralis unit as the core of the technology though, these additional imaging modalities are incorporated into the same unit, making imaging a seamless process for our patients.
