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Editors Selection IGR 8-4

Progression: Criteria for detection of progresive RNFL loss using OCT

Comment by Gadi Wollstein on:

48492 Detection of progressive retinal nerve fiber layer thickness loss with optical coherence tomography using 4 criteria for functional progression, Grewal DS; Sehi M; Paauw JD et al., Journal of Glaucoma, 2012; 21: 214-220

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Criteria for defining glaucoma progression is a controversial topic. Grewal et al. hypothesize that regardless of the functional criteria used for detecting progression, the rate of structural changes in progressing eyes will be higher than in non-progressing eyes. They compiled a longitudinal cohort of 76 healthy and glaucomatous eyes that were followed by perimetry and time-domain optical coherence tomography (Stratus) with a minimum follow-up period of 36 months. Four visual field (VF) progression criteria were used: 1. Guided progression analysis (GPA) likely progression; 2. Statistically significant slope of the visual field index (VFI); 3. Point-wise analysis with a slope of sensitivity loss greater than one dB/year in at least one point; 4. A more stringent point-wise analysis with three repeated confirmations of the progression. The rate of structural change was quantified using linear regression of retinal nerve fiber layer (RNFL) thickness measurements. The highest percentage of progressors was detected with the point-wise analysis (24%) followed by VFI (11%) and the remaining criteria had each 4% only. While baseline RNFL measurements were identical between progressors and non-progressors, there was a statistically significant difference in the rate of change between groups regardless of the criteria used except for the GPA analysis. The progression rate was significantly associated with IOP, age, central corneal thickness, disc hemorrhage, exfoliation and baseline VF global indices.

This nicely designed study supports other studies that demonstrated that functionally progressing eyes show a higher rate of structural loss than non-functionally progressing eyes. The unique aspect of the study is their finding holds true regardless of the selected criteria for functional progression. It should be noticed that the only criterion that did not follow this rule was the GPA analysis that is commonly used in clinic. The authors did not discuss this important finding that might be related to the small number of subjects that were defined as progressors by this criterion, lack of sensitivity of this criterion or other reasons.

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