Van Herick Method - AC Depth

 Van Herick's Method - AC Depth

With an optic section of the limbal cornea, orient your beam at about a 60 degree angle and compare the width of the corneal section and the width of the shadow adjacent to it.

1:1 – Open angle, VH grade 4

1:1/2 – Open angle, VH grade 3

1:1/4 – Narrow angle, VH grade 2 (Angle Closure Possible)

1: <1/4 – Angle closure likely, VH grade 1

(van Herick et al, 1969). A narrow slit beam is placed perpendicular to the most peripheral part of the cornea. The oculars are adjusted to give a view at an angle of about 60° from the light beam. The depth of the anterior chamber is graded by comparison to the thickness of the cornea.If the anterior chamber is thicker than the cornea, the angle is a wide-open grade 4. If the thickness of visible aqueous is one-quarter of the corneal thickness or less, the angle is dangerously narrow, or “slit” 

Table 1 - Fraction Grading, by region

Chamber Depth in Corneal Thickness	Angle Grade
≥cornea	4
1/4 to 1/2	3
1/4	2
<1/4	1
Slit	Dangerously Narrow

Table 2 - Van Herick's technique Grading of the anterior chamber

Grade	Estimated Angle	Probability of Closure
Grade 0	0°	Closed
Grade 1	≈10°	Very likely
Grade 2	≈20°	Possible
Grade 3	≈30°	Unlikely
Grade 4	≥45°	Impossible

Table 3 - Van Herick grading expressed as a ratio 

Ratio	Angle Closure	Angle Grade
1:1	Open Angle	VH grade 4
1:1/2	Open angle	VH grade 3
1:1/4	Narrow angle	VH grade 2
1: <1/4	Angle Closure likely	VH grade 1

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