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Editors Selection IGR 19-2
Clinical Examination Methods: Detecting Visual Field Progression
Comment by Murray Fingeret & Vincent Michael Patella on:
75703 SITA-Standard perimetry has better performance than FDT2 matrix perimetry for detecting glaucomatous progression, Wall M; Johnson CA; Zamba KD, British Journal of Ophthalmology, 2018; 0:
The authors compared the abilities of FDT Matrix threshold perimetry and Humphrey SITA Standard to identify glaucomatous progression. Using their own progression analysis, the authors concluded that the Matrix at best performed similarly to the HFA and was probably slightly inferior in identifying glaucomatous progression. We believe that their analysis was suboptimal and that better methods are available and can be applied to their data.
Matrix was designed to test different visual processes than those assessed by HFA. The two devices also have different dynamic ranges.1 Despite these differences, the authors converted the data from one device to be comparable to the other, prior to assessing how well each device detected progression. This data conversion was not only unnecessary, it also threatens their basic conclusions, to the extent that the data conversion cannot ever be exact.2
Fortunately, methods exist to determine the number of statistically significant progression events that each device is capable of detecting, based only upon measurement variability and dynamic range.3 This approach avoids having to resort to inherently inexact data conversion formulas and also avoids adoption of an arbitrary rate of progression as a surrogate for statistically significant progression events. For example, Jampel found that Standard Automated Perimetry (SAP) Mean Deviation (MD) values could be analyzed to detect 7.5 statistically significant progression steps, while optic nerve rim area and cup shape measurement made with an imaging device could detect 5.7 and 2.3 steps respectively.
Jampel's method encourages us to dream. What if we could measure 30 or even 50 progression steps between normal and blind? How might glaucoma management improve? Couldn't we quickly sort out which glaucoma suspects actually are progressing and which ones are not?
We invite the authors to have another go at analyzing their data and getting to the bottom of the very important question that they have posed.
References
- Artes PH, Hutchison DM, Nicolela MT, LeBlanc RP, Chauhan BC. Threshold and variability properties of matrix frequency-doubling technology and standard automated perimetry in glaucoma. IOVS. 2005;46(7):2451-2457.
- Fredette MJ, Giguère A, Anderson DR, Budenz DL, McSoley J. Comparison of Matrix with Humphrey Field Analyzer II with SITA. Optom Vis Sci. 2015;92(5)527-536.
- Jampel HD, Vitale S, Ding Y, et al. Test-retest variability in structural and functional parameters of glaucoma damage in the glaucoma imaging longitudinal study. J Glaucoma. 2006;15(2):152-157.
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