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Researchers explore common diagnostic questions for glaucoma
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Donald C. Hood, PhD, and Carlos G. De Moraes, MD, MPH, recommend that all patients with glaucoma or suspected glaucoma undergo visual field testing that includes more points in the macula, such as the 10-2 pattern, the G-program or a 24-2 hybrid, in addition to OCT testing that includes scans of the macula.
They explored four questions for clinicians diagnosing and monitoring patients with glaucoma and supply evidence to support their conclusions.
Question 1: When do you perform a 10-2 visual field test? Hood and De Moraes said to perform this test in patients in whom you would do or have done a 24-2 visual field.
This should include a patient with any of the following:
- an abnormal region on the retinal ganglion cell (RGC) analysis of an OCT scan of the macula;
- an abnormal region in the temporal quadrant or macular vulnerability zone of the circumpapillary retinal nerve fiber layer (cpRNFL) analysis of the OCT scan of the disc;
- one or more of the central four 24-2 points that are abnormal at less than 5% level on total deviation or pattern deviation plots;
- a visual acuity that cannot be corrected to 20/20; or
- complaints about glare or trouble reading that are not attributed to other causes.
The researchers added that they are not advocating performing a 10-2 test instead of a 24-2 test, but, rather, in addition.
Question 2: When do you perform an OCT scan of the macula? Everyone should have a scan that includes the macula, or at least everyone tested with OCT, they wrote.
Many clinicians do not obtain an OCT scan of the macular region for patients with glaucoma or suspected glaucoma, they said.
“This is a mistake since OCT disc scan, as typically performed, can miss damage seen on a cube scan of the macula,” researchers wrote.
It is important to obtain macular scans to avoid missing nonglaucomatous macular damage, which can contribute to the patient’s complaints and/or visual field abnormalities, they added. Epiretinal membranes, macular edema or holes and age-related macular degeneration are commonly missed.
Question 3: How do you know if the visual field and OCT tests agree? They suggest topographically comparing abnormal regions on the OCT to abnormal regions on the visual field.
Hood and De Moraes recommend using the RGC+ probability map associated with RGC+ thickness map, which most OCT instruments provide and is obtained by comparing the patient’s RGC+ thickness to a normative database, they explained.
They found that OCT and visual field showed agreement, with excellent sensitivity and specificity, if three or more 10-2 or 24-2 total deviation (TD) points at 5% or less or two TD points at 1% fell within the regions of abnormality on RGC+ and/or RNFL probability maps.
“For best agreement between structure and function, a 10-2 test, as well as a 24-2 test is needed; TD as well as pattern deviation, plots must be analyzed and typical summary metrics such as PSD and the average thickness of the OCT cpRNFL should be ignored,” they wrote.
Question 4: When do you look at OCT images? At the least, a circumpapillary image should be quickly examined in all eyes on which OCT imaging is performed, they said. “One can find an image of the cpRNFL on all OCT instruments, although it may take come searching.”
Clinicians can assess the quality of the scan and the accuracy of the segmentation lines marking the boundaries of the RNFL.
It is possible to see the nature of the damage in greater detail by looking at the circumpapillary image carefully, they added.
Also, a clinician can assess and follow damage in eyes with severe damage with this image.
They also recommend examining macular scans to avoid missing nonglaucomatous macular damage due to retinal conditions. – by Abigail Sutton
Disclosure: The authors report no relevant financial disclosures.
Perspective
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Edward Chu, OD, FAAO
With today’s glaucoma testing parameters and measurements for disease diagnosis and progression, clinicians have more information than ever before to make treatment decisions.
In this article, Hood and De Moraes address important glaucoma management questions through evidence-based review of recent studies. Specifically, with regard to macular involvement in glaucoma, the authors advocate performing a 10-2 visual field on any patient that is getting a 24-2 visual field and obtaining a scan of both the macula and optic nerve on everyone tested with OCT. With the information and analysis obtained through these tests, clinicians can make more informed treatment decisions by topographically comparing abnormal regions on OCT and visual field and determining whether they correlate.
The addition of macula testing to the glaucoma management paradigm may seem excessive; however, the current literature strongly supports adding these tests to our standard clinical work-up when warranted to avoid missing glaucoma diagnosis and/or progression. While questions still remain as to the optimal role for macula testing in glaucoma, recent studies have made it clear that having this additional information has enhanced our ability to take better care of our patients.
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