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While age related loss of retinal ganglion cells or decline of the retinalnerve fiber layer (RNFL) thickness with age has been suggested, such observation was based on cross-sectional data with linear regression analysis. Leung et al. examined the age-related change of the circumpapillary RNFL thickness measured by spectral domain OCT using both cross-sectional and longitudinal analysis. One hundred normal individuals were recruited for cross-sectional analysis, 35 of whom were randomly selected for longitudinal analysis. In the cross-sectional analysis, they found significant negative correlations between age and average, inferior and temporal RNFL thickness. The rates of decline were -0.33, -0.45 µm/year and -0.31 µm/year for average, inferior and temporal RNFL thicknesses, respectively. In the longitudinal analysis, the mean rates of change of average, superior, and inferior RNFL thicknesses were -0.52, -1.35 and -1.25 µm/year, respectively, after adjusting for baseline RNFL thickness, spherical error, disc area and signal strength. A greater baseline RNFL thickness was associated with a faster rate of change. This information is clinically relevant in evaluating glaucoma progression. When a clinician detects a decline of a RNFL using a trend-based analysis, the rate may be the sum of age-related change and the change derived from glaucoma progression.
When a clinician detects a decline of a RNFL using a trend-based analysis, the rate may be the sum of age-related change and the change derived from glaucoma progression
The data reported in the study may provide a guide by which clinicians may delineate the RNFL thickness decline attributable to glaucoma progression. Meanwhile, it is of interest to note that the result from the cross-sectional analysis and longitudinal analyses disagree in this study. The disagreement suggests that the argument that knowledge of age-related change should come from longitudinal data and not extrapolation from cross-sectional data.