Van Herick angle grading is a non-contact method used in eye examinations to assess the depth of the anterior chamber angle. This technique estimates how open or narrow the eye’s drainage angle is. It serves as a quick screening tool to identify individuals at risk for angle-closure glaucoma.
What is Van Herick Angle Grading?
This non-invasive technique estimates the depth of the eye’s anterior chamber angle. This angle is a recess where the cornea, the clear front surface of the eye, meets the iris, the colored part. Its primary purpose is to identify individuals at risk for angle-closure glaucoma.
A narrow angle can impede the natural outflow of aqueous humor, the fluid that nourishes the eye and maintains its internal pressure. If fluid drainage is impaired, eye pressure can build up. Elevated pressure, if unmanaged, can damage the optic nerve and lead to vision loss, a condition known as glaucoma.
How is the Grading Performed?
The procedure uses a slit lamp, a standard instrument in eye care clinics. The patient sits with their chin on a rest and forehead against a band. An eye care professional directs a narrow light beam onto the peripheral cornea, near its edge.
The beam is angled at about 60 degrees from the observer’s view. The examiner observes the space between the corneal light reflection and the iris. This non-contact method ensures the procedure is quick and comfortable for the patient.
Understanding the Grading Scale
The Van Herick grading system compares the depth of the peripheral anterior chamber to the thickness of the cornea. This comparison results in a numerical grade, typically ranging from Grade 4 to Grade 0, indicating the angle’s estimated width.
Grade 4
This signifies the widest angle, with anterior chamber depth equal to or greater than corneal thickness. This indicates a very open angle, posing low risk for angle closure.
Grade 3
The anterior chamber depth is about one-quarter to one-half the corneal thickness, indicating a sufficiently open angle.
Grade 2
The anterior chamber depth is approximately one-quarter of the corneal thickness, indicating a potentially narrow angle where closure is possible.
Grade 1
This represents a very narrow angle, with anterior chamber depth less than one-quarter of the corneal thickness, suggesting a high risk of angle closure.
Grade 0
This indicates a closed or nearly closed angle, with no visible space between the cornea and iris, posing an immediate risk of angle-closure glaucoma.
Implications of the Results
Van Herick angle grading results provide valuable information about a patient’s risk of angle-closure glaucoma. A lower grade (Grade 1 or 2) indicates a narrow or potentially occludable angle, suggesting a higher risk. This does not mean the patient has glaucoma, but it prompts further investigation to confirm the angle’s status.
Based on the grading, an eye care professional may recommend follow-up actions. These include regular monitoring of eye pressure and angle status, or additional diagnostic tests like gonioscopy. Gonioscopy offers a direct, 360-degree view of the anterior chamber angle and is considered the gold standard for assessment.
For significantly narrow angles, preventative treatments like laser peripheral iridotomy may be suggested. This procedure creates a small opening in the iris to improve fluid flow and reduce angle closure risk. Early detection and proactive management help preserve vision.