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A new add-on glaucoma module has the capability of creating an anatomic map of each patient’s eye by using two fixed landmarks. The module also includes an extensive reference data base.
Reviewed by Donald C. Hood, PhD
Glaucoma specialists have a new tool in their clinical armamentarium through an add-on module designed to improve diagnostic accuracy through a comprehensive analysis of the optic nerve head, retinal nerve fiber layer, and ganglion cell layer as well as use of an extensive reference data base.
The Glaucoma Module Premium Edition for Heidelberg Engineering’s Spectralis OCT imaging platform received FDA 510(k) clearance last fall. The add-on module, which has been on the market internationally for a number of years, has several distinctive features, said Kester Nahen, PhD, managing director, Heidelberg Engineering.
“One is that for the first time we are customizing or individualizing the scan protocol to the anatomy of the patient,” Dr. Nahen said. “There’s quite a variation from patient to patient in the way that the optic nerve head is oriented, relative to the fovea, what we call the fovea-to-Bruch’s membrane opening angle.
“And the Bruch’s membrane opening center is the center of the optic nerve head,” Dr. Nahen said. “With the OCT, we’re able to identify those landmarks, and we are then able to place any subsequent OCT scan according to these coordinates.”
The glaucoma module’s proprietary Anatomic Imaging System (APS) technology creates the anatomic map based on the two fixed landmarks.
“This is quite a unique feature that we have on our OCT system,” Dr. Nahen said. “This is individualized medicine in glaucoma care. We’re taking the anatomy of the individual patient into consideration, and then we’re using optimized scan protocols for the different anatomic structures that we’re studying.”
One of the options in the new glaucoma model is a star-pattern or radial scan that looks at the thickness of the neuroretinal rim.
“We’re not using a standard protocol that could also be used in the retina,” Dr. Nahen said. “We have come up with a scan pattern that is specific to glaucoma.”
The star-pattern scan is focused on the center of the Bruch’s membrane opening, and the end of the membrane opening is also identified on every scan, as it is a stable anatomic structure that can then be used to take cross-sectional measurements of the minimum rim width of the neuronal tissue that exits the eye.
Deterioration of the Bruch’s membrane opening minimum rim width is important in monitoring glaucoma progression, and the measurements from the scan can be compared with a reference data base included in the module. In the United States, this age- and disc-size adjusted reference represents the racial and ethnic mix of the population, making it more valuable to local clinicians.
The series of scan patterns included in the module will provide extensive information with multiple applications, said Donald C. Hood, PhD, the James F. Bender Professor of Psychology and Professor of Visual Sciences (Ophthalmology), Columbia University, New York.
“If you complete the full package on a patient, from a clinical research or clinical diagnosis point of view you have a lot of information as well as high quality scans,” he said.
“By having radial scans within the disc, it allows you to take a close look at the damaged regions around and in the disc,” he added. “It also will help differentiate damage due to glaucoma from damage due to other optic neuropathies.”
Dr. Hood tests patients and interprets OCT images in his lab and also conducts clinical research. His lab uses different OCT systems and software packages, including those from Heidelberg Engineering, with the goal of improving the use of this technology for diagnosing and understanding glaucomatous damage.
Filling the gap
The new glaucoma module for the Spectralis OCT may help eradicate what Dr. Hood sees as a shortcoming in glaucoma diagnosis.
“Glaucoma specialists in general are underutilizing the OCT,” he explained. “They tend to look at summary statistics on commercial reports. What I’ve been trying to do is get them away from these summary statistics and get them to look instead at the scan images and thickness maps.”
The module for the Spectralis OCT is set up so that users can both view reports and look at individual scans.
However, Dr. Hood is also working with Heidelberg Engineering to design an improved format for a one-page summary in the glaucoma module that will describe the key features from an imaging session for the clinicians who prefer to view a single report. It will be included in the module in the near future.
Donald C. Hood, PhD
Dr. Hood has received grants from Heidelberg Engineering of equipment and support for his laboratory at Columbia University.