The Van Herick Technique: A Simple yet Invaluable Methodology in Glaucoma Detection

Timely detection of glaucoma is fundamental in ocular assessment, making the initial patient encounter crucial for identifying warning signs. This article focuses on the slit lamp as an essential tool in the fight against this disease, highlighting the widely used Van Herick technique and its clinical value in diagnostic support for glaucoma.

Van Herick Technique

The Van Herick technique involves assessing the depth of the anterior chamber at the limbus using a slit lamp. Among its benefits, this non-contact technique is quick and straightforward. The goal is to estimate the width of the angle of the anterior chamber. To perform this technique correctly, it’s important to shift the illumination system approximately 60 degrees from the center towards the temporal region. Subsequently, the slit beam is narrowed to its maximum in an optical section and positioned on the limbus so that the corneal thickness can be observed, traversing the anterior chamber to the iris surface to establish a comparative pattern. Afterwards, the corneal thickness is compared with the shadow of the anterior chamber, which extends from the endothelium to the iris.

In an assessment scheme, the Shaffer scale can be used to classify Van Herick into four grades based on the size of the anterior chamber compared to corneal thickness:

  • Grade 1: Anterior chamber depth (ACD) ≤ 25% of corneal thickness.
  • Grade 2: ACD = 25% of corneal thickness.
  • Grade 3: ACD > 25% and ≤ 50% of corneal thickness.
  • Grade 4: ACD equivalent to 100% of corneal thickness.

Various studies have identified a consistent cutoff point where a grade 2 or lower on the Shaffer scale is highly suggestive of glaucoma. However, reported sensitivity and specificity values vary among authors, affecting the predictive value of Van Herick for angle closure.

Foster et al. (2000) proposed a modified scale dividing Shaffer’s grade 1 into three subcategories (0%, 5%, and 15%) and adding a new grade corresponding to 75% to bridge the gap between grades 3 and 4 of the traditional Shaffer scale. This modification aimed to increase the sensitivity and specificity of the test, though some still assert that a Shaffer grade 1 is sufficient to reliably suspect angle closure.

In more recent research, Sihota et al. (2019) introduced a new evaluation system termed “Van Herick plus.” This method involves tilting the slit lamp illumination system to 30 degrees with 40X magnification at the objective lens. The slit beam is minimized and dimmed with a height of 3 mm, positioned on the lower limbus to avoid pupil miosis that could affect angle opening.

This approach estimates angular opening by relating peripheral corneal thickness (PCT) to ACD, categorizing it as grade I (1/2–1) and grade IV (>1). This technique demonstrated good agreement with angles estimated by advanced methods such as OCT.

Despite varying reports on sensitivity, specificity, and inter-observer reproducibility, Van Herick has shown high agreement in narrower angles compared to advanced techniques like OCT or Scheimpflug camera. Therefore, the Van Herick technique remains a valuable tool in identifying narrow angles, accessible to a broader population, particularly where access to advanced technology is limited. When combined with clinical data from patient history and fundus examination, this test provides valuable information in comprehensive patient assessment.

Advancements in Optical Quality of Ophthalmic Lenses
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