Título

INFLUENCE OF DISC AREA AND PERIPAPILLARY RETINAL NERVE FIBER LAYER THICKNESS (RNFL) ON MINIMUM RIM WIDTH (MRW) MEASUREMENTS OBTAINED BY SPECTRAL DOMAIN OPTIC COHERENCE TOMOGRAPHER (SD-OCT)

Objetivo

To investigate the correlation between MRW and RNFL thickness measured by SD-OCT. Additionally, the influence of disc area and RNFL thickness on MRW measurements was evaluated.

Método

This cross-sectional study included 201 eyes from 111 patients (44 healthy, 62 glaucomatous and 95 suspects). All participants underwent SD-OCT imaging using the Glaucoma Premium Module Edition software package, available in the Spectralis SD-OCT. MRW and RNFL measurements were automatically calculated by the instrument for each eye. Disc area was considered the Bruch's membrane opening (BMO), estimated by the SD-OCT. Regression analysis was used to evaluate the correlation between MRW, RNFL and disc area. A multivariate regression model was built including MRW measurements as dependent variable and peripapillary RNFL thickness and disc area as independent variables. To account for the presence of multiple tests for each subject (both eyes), a bootstrap resampling at the individual level was used for estimating standard errors and statistical significance.

Resultado

There was a statistically significant correlation between MRW and RNFL thickness measurements for global (R=0.68, P<0.001) and all sectors. The strongest correlations were for the inferior temporal sector (R=0.74, P<0.001), superior temporal (R=0.65, P<0.001), nasal inferior (R=0,65, P<0.001) and nasal superior sectors (R=0.65, P<0.001). Weaker correlations were found for the nasal (R=0.46, P<0.001) and temporal (R=0.38, P<0.001) sectors. After adjusting for RNFL thickness, disc area significantly influenced MRW measurements for the nasal, inferior nasal and superior nasal sectors. Incorporating disc area into the model, showed that for each 1mm² increase in disc area, there was a 24μ decrease in global MRW measurements (P<0.001).

Conclusão

MRW and RNFL measurements showed moderate to strong correlation in all but the temporal and nasal sectors. Further, disc area had a significant influence on global MRW and should be considered when interpreting OCT findings in clinical practice.