The Cirrus HD-OCT by Carl Zeiss Meditec is a full-spectrum optical coherence tomography (OCT) device that delivers cutting-edge retina and glaucoma diagnostics. Its PanoMap analysis feature offers a single-time-point feature, which combines information from both the macula and optic nerve head. This provides an integrated widefield assessment of retinal nerve fiber layer (RNFL) and ganglion cell/inner plexiform layer (GC/IPL) thickness, with optic nerve head assessment parameters — all compared to a comprehensive normative database.

“Cirrus HD-OCT, along with our integrated diagnostic platform, helps practitioners stay ahead by providing comprehensive glaucoma and retinal disease diagnosis and management across all levels of care,” says Jim Mazzo, global president of ophthalmic devices at Carl Zeiss Meditec.

Physicians have looked for evidence that OCT could be used to inform treatment decisions in glaucoma patients before change is seen on visual fields. A 5-year prospective study showed that Cirrus Guided Progression Analysis (GPA) can identify glaucoma patients who are at elevated risk for future visual field progression. On patients where Cirrus GPA analysis flagged likely change, the visual field was 4 times more likely to have significant change 1 to 2 years later (hazard ratio 3.95).¹

Compared to other OCT devices, only Cirrus has event- and trend-based progression analysis that can aid in identifying glaucomatous progression. The GPA tracks statistically significant changes based on event and trend analysis from 5,000 superpixels in the RNFL and GC/IPL thickness maps. Thinning of the RFNL has been determined to be predictive of detectable functional decline in glaucoma and glaucoma in the preperimetric stages.^2,3

Louis B. Cantor, MD, professor of ophthalmology at the Indiana University School of Medicine and director of the glaucoma service at the Eugene and Marilyn Glick Eye Institute, both in Indianapolis, Indiana, uses the device. He notes that because there is no single parameter to universally rely on to diagnose glaucoma or determine disease progression, “It is vitally important that clinicians combine information regarding intraocular pressure, visual function, and structure to the broadest extent possible. The more that various diagnostic tests align with each other, the stronger our assessment and any treatment recommendations become.”

Dr. Cantor says that the ability to more readily assess structural changes in glaucoma and correlate those findings with other clinical assessments aids in clinical decision making. “PanoMap’s single-page report is easy to interpret,” he adds. “PanoMap provides more detailed information regarding structural changes than alternative devices.”

How It Works

The Cirrus software compares measured values to a comprehensive age-matched normative database. By visualizing any deviations, defects in the macular GC layer can be correlated to defects identified in the peripapillary RNFL, according to the company.

With other devices, RNFL and GC thickness information are presented separately, requiring clinicians to combine and interpret the information. With PanoMap, deviations of RNFL and GC/IPL thickness are automatically combined in a single integrated view, which simplifies interpretation of the relationship between RNFL and GC/IPL thickness deviations.

“Structural analysis is critically important when evaluating any patient suspected of having glaucoma, in diagnosing glaucoma, and following up on glaucoma patients for progression analysis,” Dr. Cantor says.

Clinical Applications

Zeiss offers a complete glaucoma package with retinal wellness screening in PanoMap. It includes the combination of Cirrus HD-OCT glaucoma applications and Glaucoma Workplace, an eye care data management software platform that allows physicians to manage glaucoma at all stages.

The ganglion cell analysis (GCA) map feature aids in assessing potential damage to ganglion cells. A promising role for GCA can be found in a recent study that found the measurement floor for GCA thickness to be lower than that of RNFL thickness, allowing for valid measurements in advanced glaucoma.¹ The 5-year study examined the performance of Cirrus GPA event analysis of the RNFL thickness map (6 x 6 mm²).

Anterior-segment OCT images can aid glaucoma diagnosis. For example, the iridocorneal angle is made visible.^3-5 Advanced age, female gender, and hyperopia have been associated with a narrow iridocorneal angle.⁶

Benefits to Patients

Patient compliance is one of the first lines of defense when it comes to managing glaucoma progression. With guided progression analysis, GPA and color mapping of areas that have possible and likely thinning are easy to use for patient education, according to Zeiss. With glaucoma, defects in structure often show up before defects in visual fields.

According to the company, PanoMap can aid in identifying structural changes years before the disease affects a patient’s vision. It can also help visualize macular defects, which may trace back to the optic nerve head, as well as defects in the peripapillary region, including portions of the nerve fiber layer that do not reach into the macula. Glaucoma Workplace combines Cirrus structure and Humphrey field analyzer visual function information to aid in tracking glaucoma progression, allowing easy, consistent detection of change in visual function and structure. GP

References

1. Yu M, Lin C, Weinreb RN, Lai G, Chiu V, Leung CK. Risk of visual field progression in glaucoma patients with progressive retinal nerve fiber layer thinning, a 5-year prospective study. Ophthalmology. 2016;123:1201-1210.
2. Bowd C, Zangwill LM, Weinreb RN, Medeiros FA, Belghith A. Estimating optical coherence tomography structural measurement floors to improve detection of progression in advanced glaucoma. Am J Ophthalmol. 2017;175:37-44.
3. Tay EL, Yong VK, Lim BA, Sia S, Wong EP, Yip LW. Agreement of angle closure assessments between gonioscopy, anterior segment optical coherence tomography and spectral domain optical coherence tomography. Int J Ophthalmol. 2015;8(2):342-346.
4. Hu CX, Mantravadi A, Zangalli C, et al. Comparing gonioscopy with visante and CIRRUS optical coherence tomography for anterior chamber angle assessment in glaucoma patients. J Glaucoma. 2016;25(2):177-183.
5. Quek DT, Narayanaswamy AK, Tun TA, et al. Comparison of two spectral domain optical coherence tomography devices for angle-closure assessment. Invest Ophthalmol Vis Sci. 2012;53(9):5131-5136.
6. Rufer F, Schroder A, Klettner A, Frimpong-Boateng A, Roider JB, Erb C. Anterior chamber depth and iridocorneal angle in healthy white subjects: effects of age, gender and refraction. Acta Ophthalmol. 2010;88(8):885-890.