The Van Herick technique is a straightforward and effective way to assess the anterior chamber angle^1,2.

By using a slit lamp to observe the gap between the corneal endothelium and the iris surface, this method allows practitioners to quickly determine if further investigation is needed without discomfort to the patient. Moreover, it offers great interobserver reliability², making it an ideal test for primary care optometry.

The technique’s simplicity makes it a valuable tool in both routine eye health assessment and when preparing to dilate pupils safely¹. Combined with proper training and experience, Van Herick remains an essential part of evaluating eye health and preventing serious complications.

This guide looks at the Van Herick technique in more detail; providing both a “how to” guide and context around this method.

Why Do We Use the Van Herick Technique?

Understanding anterior chamber angles is vital for identifying potential risks and ensuring safe clinical decisions. The Van Herick technique allows practitioners to evaluate these angles quickly and effectively¹, offering insight into the likelihood of angle closure. It’s a reliable² method to decide whether dilation can proceed without triggering complications, such as acute angle closure glaucoma^1,2,3,4.

The mechanism involved in acute angle closure is the sudden obstruction of the anterior chamber angle⁴ and the drainage provided by the trabecular meshwork² within⁴, causing a significant increase in the intraocular pressure of the eye. A dilating pupil causes the iris to bunch up⁴ as it dilates peripherally^2,4. This, in turn, raises the thickness of the peripheral iris region⁴. This occludes the angle, causing the spike in pressure².

This test is especially important for patients more likely to have shallower anterior chambers, such as those with hyperopia^1,5, advanced cataracts^1,5, older age¹ or certain ethnicities such as the Inuit^2,4,5 and East Asian^4,5 populations. The ability to perform this non-invasive procedure during routine exams makes it a practical and efficient tool for safeguarding eye health.

By providing clear indications of whether further investigative and more sensitive³ tests, such as gonioscopy², are needed. The technique ensures early intervention and can help prevent sight-threatening emergencies. Its role in managing patient safety and supporting thorough clinical care reinforces its value in both routine practice and specialist clinics; especially when combined with gonioscopy.

A Step-by-Step Guide to the Van Herick Technique

I will now describe how to perform the Van Herick technique.

Step 1: Set up the slit lamp

Position both yourself and the patient comfortably. Adjust the beam height to around 4mm and set it to an optical section. Instruct the patient to look at your ear with their non-tested eye to ensure they are looking straight ahead.

Step 2: Position the optical section

Move the beam to the temporal limbus and angle it to exactly 60 degrees^1,2. Use medium magnification (16x–25x)¹ to allow yourself the best chance to view the structures adequately.

Step 3: Observe the gap

Focus on the dark gap between the corneal endothelium and the iris surface. Compare this gap’s width to the corneal section.

Step 4: Use the grading system

Evaluate the anterior chamber angle using the Van Herick grades (0–4), ranging from closed to wide open. A table demonstrating this grading can be seen below:

Van Herick Grade	Gap to Corneal Section Ratio	Probability of Angle Closure
Grade 0	No gap	100% (closed angle)
Grade 1	<1 : 1/4	Likely
Grade 2	1 : 1/4	Possible
Grade 3	1 : 1/2	Unlikely
Grade 4	1 : 1 or greater	Impossible

Step 5: Repeat for the other eye

Follow the same process on the second eye, again instructing the patient to look at your ear with their non-tested eye for guidance and fixation.

Step 6: Measure the nasal angle

Shift the beam to the nasal limbus, shifting the 60-degree angle from the temporal side to 60-degrees nasal. Move the slit lamp’s viewing system towards the temporal side to avoid obstruction from the nose¹. Ask the patient to look straight into the viewing system to ensure the patient’s eyes are aligned appropriately for the illumination system. Estimate the angle again using the table above.

Step 7: Compare nasal and temporal angles

Complete the procedure for both eyes. Comparing nasal and temporal angles can provide a more comprehensive understanding of the anterior chamber, especially if there is a risk of angle closure.

Common Mistakes

Even though this test is simple, the Van Herick technique can lead to inaccurate results if not performed correctly. Here are some of the most common errors students and practitioners should be aware of:

Incorrect illumination angle
Ensure the beam is set to exactly 60 degrees. Angles less than 60 degrees make the anterior chamber appear narrower¹, while wider angles falsely widen the gap, potentially misrepresenting the angle grade.

Misplaced optical section
The optical section must be placed precisely at the limbus. Shifting it onto the cornea will widen the gap and skew your assessment¹.

Neglecting the nasal angle
While the temporal angle is often sufficient, failing to assess the nasal angle (especially if the temporal angle is narrow) can lead to inadequate assessment of the anterior chamber.

Not adjusting the viewing system when assessing the nasal angle
Many students fail to do this – as it feels unusual to move the viewing system. If the viewing system is not moved, the illumination system (when adjusted for) will either touch the patient or block the light from reaching the eye, preventing assessment.

Forgetting patient eye alignment
When assessing the temporal angle, instruct the patient to look at your ear to maintain alignment. For nasal measurements, have the patient look straight down the viewing system to achieve accurate positioning.

By paying attention to these details, you can ensure the reliability of your Van Herick assessments and reduce the likelihood making a false interpretation.

Practical Benefits and Limitations of the Van Herick Technique

The Van Herick technique is a popular choice among practitioners for good reasons. Its simplicity and speed make it ideal for routine eye examinations, allowing quick assessments of anterior chamber angles without causing any discomfort to the patient. It’s a non-invasive technique allows it to seamlessly integrate into everyday practice, and it doesn’t require specialist equipment beyond a slit lamp.

However, the technique has its limitations. It can only be used to assess the temporal and nasal angles¹, leaving the superior angle unexamined⁶—the angle most prone to occlusion^1,6. While it provides conservative estimates, this can be enough to flag potential issues requiring further investigation, such as gonioscopy. Gonioscopy offers a more detailed view³ but is more invasive and requires additional expertise and equipment¹.

Despite these drawbacks, the Van Herick technique remains a practical tool for detecting risks associated with narrow angles, especially when time and patient comfort are priorities.

Conclusion

The Van Herick technique remains a key test in the anterior eye assessment. Its simplicity and accessibility make it an invaluable tool in routine clinical practice, offering quick and effective insights into a patient’s risk of angle closure or other complications. While its limitations mean it may not replace more comprehensive methods like gonioscopy, it provides a reliable foundation for deciding when further investigation is needed.

Mastery of this technique comes with practice and attention to detail, ensuring both patient safety and confidence in your assessments. If you are a student, do practice this technique regularly as it is frequently assessed – both in undergraduate clinics and in other assessments post-graduation. By incorporating the Van Herick technique naturally into your routine, you enhance your ability to deliver thorough and proactive eye care.

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Further Reading

1. Prokopich CL, Hyrnchak P, and Elliott DB (2007). Ocular health assessment. In: Elliott DB Clinical Procedures in Primary Eye Care: 3rd Edition. Philadelphia: Butterworth Heineman pp. 260-262.
2. Javed A, Loutfi M, Kaye S, and Batterbury M (2017). Interobserver reliability when using the Van Herick method to measure anterior chamber depth. Oman Journal of Ophthalmology 10(1): 9-12.
3. Johnson TV, Ramulu PY, Quigley HA, and Singman EL (2018). Low sensitivity of the Van Herick method for detecting gonioscopic angle closure independent of observer expertise. American Journal of Ophthalmology 195: 63-71.
4. Zhang X, Liu Y, Wang W, Chen S, Li F, Huang W, Aung T and Wang N (2017). Why does acute primary angle closure happen? Potential risk factors for acute primary angle closure. Survey of Ophthalmology 62(5): 635-647.
5. Shalaby WS, Reddy R, Razeghinejad R, and Katz LJ (2024). Contemporary approach to narrow angles. Journal of Ophthalmic & Vision Research 19(1): 88-108.
6. Foster PJ, Devereux JG, Alsbirk PH, Pak Lee PS, Uranchimeg D, Manchin D, Johnson GJ, Baasanhu J (2000) Detection of gonioscopically occludable angles and primary angle closure glaucoma by estimation of limbal chamber depth in Asians: modified grading scheme. The British Journal of Ophthalmology 84: 186-192.