Glaucoma-focused session with Angelo P. Tanna, MD, launches Northwestern University’s “Dinner with the Experts” series

Kicking off Northwestern University’s “Dinner with the Experts” series, Angelo P. Tanna, MD, leads a deep dive into OCT and perimetry for glaucoma progression on September 9, 2025. (Image credit: AdobeStock/FourLeafLover)

As part of its new “Dinner with the Experts – Cases, Updates, and Clinical Pearls” series, the Northwestern University Department of Ophthalmology will host a virtual glaucoma-focused educational session on September 9, 2025, from 6 to 7 pm Central time. This session, led by Angelo P. Tanna, MD, vice chair of the Department of Ophthalmology and director of glaucoma at Northwestern, will explore the critical role of optical coherence tomography (OCT) imaging and perimetry in detecting glaucoma progression—a topic of growing importance in clinical practice.

Although Tanna will lead the inaugural glaucoma session, the overall series is directed by Robert S. Feder, MD, who has helped shape the program’s vision and educational goals.

READ MORE: Q&A: Inside Northwestern University’s “Dinner with the Experts” educational series with Robert S. Feder, MD

Monthly sessions will follow from November 2025 through June 2026, each spotlighting a different subspecialty and speaker. All sessions are scheduled to take place from 6 to 7 pm Central time. To learn more or to register for any of the Dinner with the Expert sessions, email: ophevents@northwestern.edu

• Tuesday, September 9, 2025 | Glaucoma, Angelo P. Tanna, MD
• Tuesday, November 18, 2025 | Cataract and Refractive, Surendra Basti, MD
• Tuesday, December 16, 2025 | Uveitis, Timothy Janetos, MD
• Tuesday, January 20, 2026 | Oculoplastics, Liza M. Cohen, MD
• Tuesday, February 17, 2026 | Ocular Pathology, Paul J. Bryar, MD
• Tuesday, March 17, 2026 | Neuro-Ophthalmology, Nicholas J. Volpe, MD
• Tuesday, April 21, 2026 | Retina, Manjot K. Gill, MD
• Tuesday, May 19, 2026 | Ocular Oncology, R. Christopher Bowen, MD
• Tuesday, June 19, 2026 | Cornea, Robert S. Feder, MD

To learn more or to register for the session on September 9, click here. 

The Eye Care Network sat down with Tanna to preview the session and discuss emerging trends in glaucoma diagnostics.

Note: The transcript has been lightly edited for clarity and length.

This session focuses on “Using OCT imaging and perimetry to detect glaucoma progression.” Why is early and accurate detection of progression so critical in glaucoma care?

Angelo P. Tanna, MD: There are 2 types of errors that occur frequently in the diagnosis (and misdiagnosis) of glaucoma progression. Often, both with visual fields and imaging, mild but real disease-associated changes over time are dismissed as noise. On the other hand, in the case of imaging, changes attributable to normal aging, artifacts or non-glaucomatous processes such as the release of vitreous traction or an improvement of retinal edema, for example, are misdiagnosed as signs of glaucoma progression. Obviously, it is very important to correctly determine whether the glaucomatous disease process is stable or not because that drives treatment decisions that will have a real impact on patients' quality of life. Unnecessary therapies have the potential to cause harm and the failure to appropriately intensify therapy in patients with disease progression leads to further, usually preventable, vision loss.

OCT and visual field testing are both core tools for glaucoma specialists. How do these methods complement each other in clinical decision-making?

Tanna: In general, at earlier stages of the disease process, changes in structure measured by OCT may be more easily detectable than changes in the visual field. This is in part because the large variation in visual function among individuals translates to broad ranges of what is considered normal compared to the normative database. So, a person who performs well on visual field testing can experience a decline in visual function driven by glaucoma but still remain in the normal range with respect to the normative database. As the disease progresses, in general, the visual field, the macular ganglion cell–inner plexiform layer (GCIPL) thickness, and the microvascular density as measured with OCT angiography are more sensitive for the detection of progression.

It is noteworthy that the measurement of the retinal nerve fiber layer (RNFL) reaches a floor in advanced disease after which point changes in the average RNFL thickness over time are not highly informative. It has been shown, however, that with very careful scrutiny of the details of the visual field and various OCT-derived structural measurements, one can see changes occurring with both structure and function together, throughout the spectrum of disease severity. But this is more difficult in the real world in which patients are far from perfect at taking visual field tests and various artifacts and other limitations get in the way of obtaining ultra high-quality imaging. The bottom line is that we need both OCT imaging and visual field testing at most all stages of the glaucoma disease progression to reliably detect disease worsening in a timely fashion.

One of the program’s goals is to help clinicians identify artifacts in OCT and visual fields. What are some of the most common pitfalls or sources of error you see in practice?

Tanna: Visual field artifacts that commonly cause confusion include those associated with high myopia. The most common OCT artifacts include errors in segmentation of the tissue of interest.

Normal aging can influence OCT and perimetry results. How can clinicians distinguish true disease progression from age-related changes?

Tanna: Normal aging certainly influences both the thickness of the neural tissues that are measured by OCT as well as the threshold sensitivity to visual stimuli that is measured during visual field testing. In the case of visual fields, the software in the machine presents the physician with the difference between the patient's threshold sensitivity and that of an age-matched normative cohort. So, with visual field testing, when relying on mean deviation, pattern standard deviation, the visual field index, or Guided Progression Analysis as examples, the machine takes into account normal aging. So, any change you see can be considered to be independent of the normal, age-related deterioration in visual function.

With structural measures obtained with OCT, however, the story is different. Cirrus uses trend analysis to evaluate serial OCTs over time for statistically significant change beyond expected test–retest variability, but not normal, age-related decline. Other platforms such as Spectralis also do not adjust for age-related change in presenting serial OCT information of time. Distinguishing true disease-related change with OCT requires an assessment of the rate of change, considering the baseline measurement (the thicker the RNFL at baseline, for example, the greater the expected normal age-related change) and the spatial pattern of the change. In the case of the RNFL, both the inferotemporal and superotemporal regions thin most rapidly with age, just as is the case for glaucoma-related change, making it difficult to distinguish between disease versus age-related change. If, however, one observes a significant rate of change localized to one sector, one can more safely attribute that to the glaucoma disease process.

What are the key takeaways that you hope attendees will apply in their practices the next day?

Tanna: To learn to use OCT to detect glaucoma progression; to learn to use visual fields to detect glaucoma progression; to learn to identify artifacts in OCT and visual fields; and to learn to account for the influence of normal aging on serial measurements of the retinal nerve fiber layer and GCIPL.

Anything else to add that we haven’t touched upon or you feel is important for our audience to know?

Tanna: Another point I want to convey pertains to the assessment of the reliability of visual fields. I’ve seen physicians dismiss visual fields labeled as unreliable on the printout when in fact they are very reliable. The inventors of the Humphrey perimeter have said that the reliability indices are the least reliable part of the machine. The key to determining if a visual field is reliable is to have a dedicated technician verify that the patient’s fixation was good during testing. One can then ignore the gaze tracker and the fixation losses which can both falsely indicate poor reliability. False positive responses can be a problem; however, it has been shown that a false positive response rate can be substantially higher than the 15% level that triggers the “xx” and “*** Low Test Reliability ***” alerts. Looking for abnormally high sensitivity is a much better approach for identifying fields that are truly unreliable due to false positive responses.