Bill Harvey: The narrows
Harvey discusses anterior chamber angle grading and its value
Author: Bill Harvey
My anterior chamber angle can be recorded variously as 0.2, 20% or grade 1, depending on whether you prefer a decimal grading, percentage grading or old-fashioned VH grading.
Over the last few weeks, I have noticed a worrying trend among graduate trainees when it comes to van Herrick. They are required to show a record of a patient with a VH grade of 3 or less. All but one was unable to answer the question ‘what does grade 3 mean?’, while many claimed it difficult finding a patient with VH grade 3 or less. The ubiquity of grade 4 in record cards, despite most elderly hyperopes likely to have narrow angles, does reinforce the view that van Herrick is not well done. Does it matter? Well, when a majority of trainees have told me that they would refer anybody with grade 2 or less to hospital, then yes it does.
Most authorities on angle closure suggest that the real value of van Herrick is to either detect inter-eye asymmetry or a narrowing of angle over time. When a cornea:gap ratio reduces from 1:1 to 2:1, the old-fashioned grading would record this as grade 3 in both cases. Surely, we should all be using a better grading, either 100% to 50% or 1.0 to 0.5, if changes in angle are to be recorded?
As primary care focuses on reducing unnecessary referrals, it is worth remembering that a grading of less than 0.25 (25% or grade 1) is equivalent to a Schaffer grade 1, so a significant risk of angle closure. Should I be worried? No. I have had gonioscopy and anterior OCT and no iridocorneal contact found, while VH has remained stable over the years. And yet, I have never been referred to the eye hospital.
As we keep more of our narrow angle patients, try giving them the new College of Optometrists leaflet; it is well written.
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