Abstract
Purpose :
To determine the contrast-to-noise ratios (CNRs) of structural and functional measurement techniques for assessing their sensitivity to detect glaucomatous progression in various stages of the disease.
Methods :
CNRs for the mean peripapillary retinal nerve fiber layer thickness (RNFLT) measured by SD-OCT, and the Mean Deviation (MD) and the Visual Field Index (VFI) determined by standard automated perimetry were calculated for the transitions between the various stages of glaucoma: normal to mild, mild to moderate, moderate to advanced and advanced to severe glaucoma. Prospective longitudinal data from healthy and glaucomatous eyes were used. Contrast was defined as the change of the mean value of the parameter between two stages. To determine the noise, linear regression of the data of each parameter from 5 subsequent visits per eye was performed. Noise, expressed as a standard deviation, was subsequently calculated from the residuals of the linear regressions (fig. 1).
Results :
205 eyes from 123 participants (46% men, 53% women, age 63 ±12 years) were included for analysis. Mean time between the first and the fifth visit was 57.5 (±4.8) months. The results are shown in figure 2. The RNFLT had a higher CNR in the transition from normal to mild glaucoma compared to the functional measures. The CNRs for the functional measures were higher in the transition from moderate to advanced and advanced to severe glaucoma compared to the RNFLT. The structural and functional parameters showed similar CNRs in the transition from mild to moderate glaucoma. The MD and VFI showed similar CNRs in all four transitions compared to each other.
Conclusions :
The CNR method showed that the RNFLT is more sensitive for detecting glaucoma progression at the onset of glaucoma compared to the functional measures, while the latter showed to be more sensitive for detecting progression in the later stages of glaucoma. In addition, it showed that the MD and VFI were similarly sensitive for the detection of progression across the disease spectrum. More importantly, it showed that the CNR method is a useful tool for assessing and comparing the sensitivity of a measurement to detect disease progression. This could optimize the detection of progression not only in glaucoma, but in other (eye) diseases as well.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.