Purchase this article with an account.
Sara T. Ali, Scott D. Smith, Angela G. Pugliese, David Sola-Del Valle; Effect Of Baseline Value On Repeatability Of Nerve Fiber Layer And Optic Nerve Measurements By Spectral-Domain Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2011;52(14):189.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To investigate the association between baseline value on the repeatability of optic disc and retinal nerve fiber layer thickness (RNFLT) measurements by spectral-domain optical coherence tomography (SD-OCT).
Eighty-four glaucoma patients, suspects and ocular hypertensives (168 eyes) and 10 healthy volunteers (20 eyes) with high quality scans (signal strength ≥7) were included in the study. Each subject underwent optic disc and RNFLT measurements using SD-OCT (Cirrus OCT, Carl Zeiss Meditec). In a single session, 3 scans were obtained of each eye. Clock hour thickness measurements for left eyes were transposed to match the pattern of the right eye for appropriate comparison. Variability was estimated by computing the standard deviation (SD) and coefficient of variation (CV) of the mean RNFLT measurements along the pseudo-scan circle, as well as mean RNFLT in each quadrant and individual clock hour. In addition, SD and CV of optic disc parameters including rim area, disc area, cup volume, and mean and vertical cup/disc ratio (CDR) were computed. Subjects were categorized into lower, middle and upper tertiles of the mean value of the 3 scans for each measurement parameter. Comparisons of SD and CV were made across tertiles to assess the effect of baseline value on the degree of variability.
Repeatability of mean RNFLT was high (CV=2.9%). No association was seen between variability of this parameter and baseline RNFLT. Values of CV ranged from 3.0% to 9.4% in the 4 quadrants, and from 3.1% to 16.0% in the 12 clock hours. The SD of superior quadrant and clock hour 12 RNFLT was greater in eyes with the lowest baseline value (both p<0.05). Thinner baseline values also resulted in higher CV for several RNFLT parameters in the thickest zones, including superior and inferior quadrants, and clock hours 1, 2, 6, 7 and 12 (all p<0.05). Lower baseline values of optic disc parameters resulted in a larger CV for rim area in the lowest compared to the highest tertile (8.2% vs. 5.0%, p=0.03). Variability in measurement of vertical CDR was greater in eyes with smaller baseline values, with CV of 8.7% compared to 1.6% in those with the highest values (p=0.0001).
Repeatability of RNFLT and optic disc parameter measurements with SD-OCT is high. Lower baseline values in the superior and inferior quadrants and clock hours result in higher CV and greater relative variability, making the identification of progression in these areas more difficult with advanced glaucoma. Repeatability of CDR measurement appears to be better with higher baseline values.
This PDF is available to Subscribers Only