Sponsored by NIDEKThe Importance of Iridocorneal Angle
Anatomy in Clinical Decision Making
Automated gonioscopy with the GS-1 allows you to permanently record anglefeatures, adding greater utility to an important examination technique inglaucoma patients and suspects.
BY CARLO E. TRAVERSO, MD
The usefulness of gonioscopy in patients withsuspected or confirmed glaucoma is wellestablished. While the most obvious reason toinspect the angle is to differentiate open- versus
closed-angle, there are in fact several featuresof angle anatomy that help to optimize clinical management.
One example is in an eye with an open, but narrow, angle thatwill likely require reevaluation in the future. In addition, findings
suggesting pigment dispersion or exfoliation pose a greater risk
for the onset of glaucoma, thus requiring monitoring. Moreover,closed-angle glaucoma actually describes a family of different
glaucomas that are characterized by different features, and eachmay require different treatment approaches.
Several systems have been proposed for grading gonioscopic
findings and classifying features of the iridocorneal angle (ICA)
anatomy. In my view, the Spaeth Gonioscopic Grading System,
first described in 1971,1 offers the most complete assessmentof anatomic features. This system includes a description of
the true iris insertion in addition to the angular approach, thedescription of the profile of the peripheral iris, and characterization of trabecular meshwork pigmentation. The merits ofthe various grading systems for characterizing ICA anatomy
have been debated for decades. My perspective is that using
the Spaeth system involves a short learning curve, but thereason why it is so valuable is that it encourages the clinicianto think beyond a binary characterization of the ICA as either
open or closed; this is unique among the existing systems.
Ultimately, whether a grading system is used or not, it isimportant to identify the various features of the ICA anatomy
and to direct decision-making accordingly.

LIMITATIONS IN IMAGING THE ICA
Ideally, all patients being assessed for potential glaucoma
would undergo a gonioscopic examination.2 Unfortunately,
studies suggest that up to 50% of glaucoma patients everreceive a gonioscopic examination.3,4 Several factors arebelieved to be contributing to the underutilization ofgonioscopy, including technical challenges in learning andAB

Figure 1. Single field image examples. Pigment disperion syndrome (A) shows finely dispersed
brownish pigment similar to cinnamon powder. In contrast, pseudoexfoliation (B) shows
blackish more granular pigment, often peculiarly distributed on and beyond the Schwalbe’s line
forming the undulating Sampaolesi’s line, specific to this condition.

performing the proper technique, lack of time, and patient
discomfort. Additionally, overreliance on advanced imaging
modalities may induce a decreased use of some of the essential
steps in examining the eye, including performing direct
ophthalmoscopy or gonioscopy.
Imaging is intended to complement the examination, adding
to, but not replacing, the clinical assessment. This is because
imaging platforms record measurements that are analyzed
by software that builds images emulating the real anatomy.
Imaging can be quite accurate and allows enhancement of
selected details that might be of interest, but the images
produced are not real. Viewing the anatomy and recording it
photographically might not be the best or the most feasibletechnique for all eyes and all conditions, but the image is real.
This is a subtle difference but one that can have relevant implications for making decisions.
During gonioscopy, the clinician views the anatomy, makes
notes on the various anatomic features, and characterizes thefeatures of the ICA. To take photographs during gonioscopy isobviously possible, but it is time-consuming and not simple.
In this regard, the recent availability of an automated gonioscopy platform, the GS-1 Gonioscope (NIDEK), is an intriguing
option that would be suitable for almost any style of practiceand particularly for those who manage a high volume of glaucoma cases.
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the technique required to perform a correct gonioscopic
examination and repeating it in different patients provides anopportunity to become familiar with the ICA anatomy. At thesame time, it may be important to document the results witha photograph. There is a multitude of scenarios where thiskind of photographic evidence could be relevant, including thecomparison of serial images as patients are observed over time;
documenting the angle in preparation for glaucoma surgery,especially when the placement of a stent is planned; andobserving and documenting the angle after glaucoma surgery
to confirm the position of any implanted device. In case of
primary angle closure, early lens extraction with IOL placement
has emerged as a viable treatment option in selected patients,5-7emphasizing the need for gonioscopic documentation. Besides
the clinical use, goniophotography would help in case a
medicolegal issue arises.

CONCLUSIONS

Figure 2. A circular stitching view of an EX-PRESS Glaucoma Filtration Device (Alcon).

Figure 3. A linear stitching view of an EX-PRESS Glaucoma Filtration Device.

AUTOMATED GONIOSCOPY IN REAL-WORLD SETTINGS
One important feature of the GS-1 is that the images aretaken and shown in color. This may become important, forexample, when trying to distinguish between brownish pigmentary deposits that suggest pigment dispersion syndrome
and the blackish appearance of trabecular pigment in pseudoexfoliation (Figure 1)—two entities that have different clinicalbehavior. These characteristics are typically observed withgonioscopy during the clinical examination and recorded in thepatient’s chart by hand. On the other side, attaching an actual
photograph from the GS-1 is far simpler and much moredefinitive. Moreover, such distinctions could not be made using
black-and-white gonioscopic photography.
In addition, the GS-1 captures a high-resolution image forup to 360° of the ICA. Similarly to popular imaging modalities,
such as anterior chamber OCT, ultrasound biomicroscopy, andthe Scheimpflug camera, the GS-1 may be operated by a technician, which is an advantage for workflow. A full-field image
called “stitching” can be created by covering the 360° of theICA on the circular and linear ways (Figures 2 and 3).
My impression is that the GS-1 should not completely
replace examination with a goniolens. On the contrary, learning
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The availability of automated gonioscopy changes how gonioscopy may be used in patients with suspected or confirmed
glaucoma for the better. It basically takes less than 1 minuteper eye examined, and it is possible for a technician to performgoniophotography, which is of benefit for the clinician, allowing more time for the clinician to focus on tasks that require
the expert input of the ophthalmologist.
In short, the GS-1 is an instrument able to improve theefficiency of gonioscopy, which is sometimes considered atime-limiting procedure. Since all the features are visible andrecordable, the GS-1 photographs are usable with the Spaethsystem to grade and classify the anatomy. In addition, because
the photograph obtained is an actual representation and not
a reconstructed image, it can be used for detailed recording ofthe ICA anatomy and allows for accurate follow-up. n1. Spaeth GL. The normal development of the human anterior chamber angle: a new system of descriptive grading. TransOphthalmol Soc UK. 1971;91:709-739.
2. Prum BE Jr, Herndon LW Jr, Moroi SE, et al. Primary angle closure preferred practice pattern guidelines. Ophthalmology.
2016;123(1):P1-P40.
3. Coleman AL1 Yu F, Evans SJ. Use of gonioscopy in medicare beneficiaries before glaucoma surgery. J Glaucoma.
2006;15(6):486-493.
4. Varma DK, Simpson SM, Rai AS, Ahmed IIK. Undetected angle closure in patients with a diagnosis of open-angle glaucoma.
Can J Ophthalmol. 2017;52(4):373-378.
5. Azuara-Blanco A, Burr J, Ramsay C, et al; EAGLE study group. Effectiveness of early lens extraction for the treatment of primary
angle-closure glaucoma (EAGLE): a randomised controlled trial. Lancet. 2016;388(10052):1389-1397.
6. Traverso CE. Clear-lens extraction as a treatment for primary angle closure. Lancet. 2016;388(10052):1352-1354.
7. Traverso CE, Cutolo CA. The effects of phacoemulsification and intraocular lens implantation on anatomical and functionalparameters in patients with primary angle closure: a prospective study. Trans Am Ophthalmol Soc. 2017;115:T7.

Carlo E. Traverso, MDn P rofessor and Chairman, Clinica Oculistica Universitaria, Department ofNeurosciences, Ophthalmology and Genetics, Ospedale Policlinico San Martino—
IRCCS, Genova, Italyn F inancial disclosure: Research Support (NIDEK); Travel Compensation (NIDEK)