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Anterior chamber depth measurement by optical pachymetry: systematic difference using the Haag-Streit attachments
1International Centre for Eye Health, ICEH/LSHTM, Keppel Street, London WC1E 7HT, UK. rupert.bourne@lshtm.ac.uk
The British Journal of Ophthalmology
|January 21, 2006
Summary
Accurate anterior chamber depth (ACD) measurement is crucial for glaucoma. Method B, a simpler technique, consistently yields deeper ACD measurements than the recommended Method A, highlighting the need for standardized measurement protocols.
Area of Science:
- Ophthalmology
- Optometry
- Glaucoma Research
Background:
- Accurate anterior chamber depth (ACD) measurement is vital for identifying primary angle closure glaucoma suspects.
- Haag-Streit recommends deducting corneal thickness (Method A) for precise ACD.
- Ophthalmologists often use a simpler method (Method B) measuring from endothelium to lens.
Purpose of the Study:
- To compare the agreement between two methods of measuring anterior chamber depth (ACD).
- To quantify the difference in ACD measurements obtained by Method A and Method B.
Main Methods:
- Two independent studies were conducted in Denmark (n=127) and Thailand (n=109).
- Method A: Corneal epithelium to anterior lens surface (includes corneal thickness).
- Method B: Corneal endothelium to anterior lens surface (excludes corneal thickness).
Main Results:
- Method B consistently yielded significantly deeper ACD measurements than Method A in both populations (p<0.001).
- The difference in ACD increased with increasing chamber depth, showing a positive correlation.
- The methodological difference was comparable to age-related ACD reduction per decade.
Conclusions:
- Clinicians must recognize that Method A and Method B produce different ACD results.
- Standardizing ACD measurements using a consistent method, such as the Haag-Streit optical pachymeter, is recommended.
- Understanding this methodological difference is important for accurate glaucoma risk assessment.
