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A. T. Lu, P. Nguyen, D. Huang, Advanced Imaging for Glaucoma Study Group; Glaucoma Progression Criteria for Nerve Fiber Layer Measurements by Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4638. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To establish criteria for detection of glaucoma progression by serial measurement of retina nerve fiber layer thickness (RNFLT) by optical coherence tomography (OCT).
We performed an analysis on 52 normal (N), 171 glaucoma suspect or pre-perimetric glaucomatous (GSPPG) and 105 perimetric glaucoma (PG) participants in the Advanced Imaging for Glaucoma Study who had completed at least one followup visit. The overall average RNFLT measured by the Stratus OCT system was primary outcome measure. RNFLT was measured twice at each visit. Followup visits are performed annually in the N group and semiannually in the other groups. The criterion for significant interval change in RNFLT was based on a linear mixed model analysis of N data, accounting for age and between visit, within visit, intereye and intersubject variance components.
Signal strength had a significant effect on RNFLT measurements. The effect was neutralized by a linear regression-based adjustment. Age-related RNFLT thinning was fit by a log linear model. The one-percentile level cutoff for glaucoma progression based on RNFLT loss between followup and baseline tests is given by the formula (in%), is (0.28 * interval) + 9.91, where interval is the number of years between the followup and baseline tests. The formula translates to a cutoff threshold of -10.1% for a followup interval of 1 year and -12.7% for 10 years. Progression that was confirmed by 3 consecutive measurements had a reversion rate of 12.5% in GSPPG+PG groups. Eight eyes in the GSPPG and PG group had confirmed OCT progression, over an average followup length of 12.5 months. These eye did not have more interval visual field (VF) progression than nonprogressed eyes, but had higher intraocular pressure (IOP) rise relative to the baseline (P=0.006).
We have developed criteria for the detection of glaucoma progression based on serial OCT measurements of RNFLT that compensated for the effects of signal strength variation and normal aging. Short-term followup analysis shows that IOP had a effect on RNFLT that might be explained by mechanical strain rather than glaucoma progression. Long-term followup will be needed to establish the relationship between interval changes in RNFLT with VF.
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