Gonioscopy of the anterior chamber angle. Diagnoses of Narrow Angles by the Van Herick Technique Atalie C. Thompson, MD, MPH,1 Daniel M. Vu, MD,1 Lisa A. Cowan, MD, PhD,2 Sanjay Asrani, MD1 Purpose: To identify which factors are associated with a deep-appearing anterior chamber on slit-lamp examination by the Van Herick (VH) technique in eyes with a diagnosis of narrow angle (NA) on gonioscopy.
They are graded Wide through IV, with Wide being the most open. See Table 2 for detailed description of the the Shaffer classification system.
1,2 Perhaps, clinicians find it difficult to obtain adequate views due to improper technique, poor patient cooperation or lack of practice. Letters (A-C) are used to describe the level of iris insertion. This is named for the configuration or shape of the iris as it runs from the papillary margin to the insertion.
Although anatomically narrow angles may not be the talk of the town in glaucoma ... whereas an angle with PAS will not move and the iris will remain over angle structures.
The first line is parallel to the trabecular meshwork and the second a tangent to the anterior iris surface approximately 1/3 of the distance from the most peripheral portion of the iris. Therefore, it is critical to be aware of the symptoms and take action immediately if you experience any. While many eyes have narrow angles by gonioscopy, only a small percent of these will ultimately get angle-closure disease. The definitive treatment for angle-closure glaucoma is to prevent iris blocking of outflow by making a laser hole in the iris— iridotomy. Schlemm’s canal drains the aqueous humor after passing through the trabecular meshwork. Identifying this structure helps to differentiate open angles from closed angles. We will discuss these below, moving from most anterior to posterior. The anterior ciliary body band can be seen in eyes with deeper angles. The typical view through most goniolenses is illustrated by these idealistic schematic diagrams.
Patterns of care for open-angle glaucoma in managed care.
See Table 4. A thin slit beam is angled approximately 60 degrees and aimed at the cornea peripherally near the limbus. It is then followed by a letter without parentheses, which denotes the insertion after compression. The trabecular meshwork is a very important landmark for diagnostic purposes, incisional surgery, and laser surgery.
Depending on the severity, this can decide a treatment approach or indication for a peripheral laser iridotomy. 2003 Jun;121(6):777-83. We will discuss them below. The Scheie system is based upon visibility of the anatomical structures of the angle. It also uses a number system, but is in reverse of the Scheie system. Proper documentation is important so that you are able to follow patients over time and so that other may interpret your findings. Foreign bodies can also be found on gonioscopy.
The amount of pigmentation may vary from person to person, and even from quadrant to quadrant as noted above. An example is (B)D30P1. Although the value of gonioscopy is evident, two separate studies reviewing patient records show that less than half of primary open angle glaucoma (POAG) patients had a single gonioscopy procedure during their initial glaucoma workup. This system describes the iris insertion, angularity, configuration, and pigmentation of the posterior trabecular meshwork. For example, a Grade 4 angle in the Shaffer system is wide open, while a Grade IV in the Scheie system is anatomically closed with no structures visible!
This is noted by its white color during gonioscopy. The angle of the iris is defined as the angle between two lines. Because it is done without gonioscopy, no angel structures can be identified and it does not replace gonioscopy. See Table 1 for an in depth description of the Scheie system.
The ratio is then used to provide some information on the width of the chamber angle. Numbers (0-3) are used to describe how much trabecular meshwork is present.
In a recent study, only 45% of patients had received gonioscopy within either 12 months prior or 6 months following the initial diagnosis of POAG (Arch Ophthalmology 2003; 121:777-783)The Academy uses cookies to analyze performance and provide relevant personalized content to users of our website.American Academy of Ophthalmology, Glaucoma, Section 10.
AS-OCT imaging allows us take detailed cross-sectional images of the anterior segment of your eyes and precisely measure parameters such as the width of the angle,thickness of the iris and anterior chamber depth. It is done at the slit lamp and is most helpful before dilation. It is a valuable skill that should be used by all ophthalmologists, not just glaucoma specialists. Gonioscopy grading systems were established to provide a standardized description of the anatomy of the anterior chamber angle. As discussed above, gonioscopy is extremely useful in determining how open or narrow an angle is and the possibility of it becoming closed. PubMed PMID:
If a letter is in parentheses, this means it is the originally viewed insertion prior to compression. A clinician must possess this knowledge in order to properly manage his or her patients.
There are also many normal variations that one must be aware of. It can also be present with hypotony.
While narrow-angle glaucoma is very rare, when it occurs, it causes damage rapidly. There are many other goniolenses available for use, including modified versions of the aforementioned, which prove valuable for surgical use (Although the details vary based on the type of goniolens used, in general the gonioscopy process involves:
There are also many other indications and uses for gonioscopy. The width of the angle is determined by the site of insertion of the iris on the ciliary face, the convexity of the iris, and the prominence of the peripheral iris roll. There are 10 to 20 angle-closure suspects for every person that gets the disease.
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