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Editors Selection IGR 13-1
Structure: HRT for daily practice
Comment by Luciana Alencar on:
26325 Predicting the onset of glaucoma the confocal scanning laser ophthalmoscopy ancillary study to the ocular hypertension treatment study, Weinreb RN; Zangwill LM; Jain S et al., Ophthalmology, 2010; 117: 1674-1683
Can we use HRT-based structural assessment instead of stereophotograph- based cup-to-disc ratio (CDR) to predict which ocular hypertensive patients are at higher risk for progression? In their latest analysis from the Confocal Scanning Laser Ophthalmoscopy (CSLO) Ancillary Study to the Ocular Hypertension Treatment Study (OHTS), Weinreb et al. (1177) continue to provide us with important information about the value of structural assessment in predicting progression.
In this investigation, they estimated the predictive ability of the Glaucoma Probability Score (GPS), and compared it with the Moorfields regression analysis (MRA), several stereometric parameters and stereophotograph-based subjective horizontal CDR. The GPS, which was not available at the time of the first OHTS CSLO publication, is a new analysis available with the HRT 3.0 software that calculates the likelihood of glaucoma without the need to manually draw a contour line to the optic disc. Contour lines are needed for several HRT calculations and it is widely known that they add undesired subjectivity to the examination, as well as increase interobserver variability. The study included over 800 eyes and followed state-of-the-art methodological standards. Their principal findings were that the predictive ability of models including GPS, MRA, stereometric parameters or stereophotograph-based CDR were similar, in agreement with previous studies. Moreover, they showed there was no additional benefit of including any GPS and most MRA results (except nasal inferior and temporal superior) to models already containing the subjective CDR (besides IOP, CCT, PSD and age). The latter was not done on the previous report due to statistical issues resulting from the strong correlation between the two, which was resolved for this publication (longer follow-up and more endpoints).
These findings have important practical implications on the use of the HRT on daily practice. Nevertheless, one should take into account the fact that protocols in large randomized clinical trials do not always represent the way the same instruments or techniques can or should be used routinely in clinical practice. It is possible that in different scenarios (contour lines drawn without stereophotographs, CDR assessment performed at the slit-lamp, variably skilled examiners, etc.) the additive effect of the HRT to risk models would have a slightly different impact.
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