Abstract
Purpose:
To explore the association between change in visual function and in retinal nerve fiber layer thickness (RNFLT) in participants with early to moderate glaucoma and to test whether regional analyses produce stronger correlations between functional and structural change than global analyses.
Methods:
Data from 167 subjects with mild to moderate glaucoma or risk factors for glaucoma were collected at 6-month intervals. Spectral Domain Optical Coherence Tomography (SDOCT) peripapillary circle scans (Spectralis) and Standard Automated Perimetry (Humphrey Field Analyzer: SAP, SITA 24-2) were performed at each visit. All RNFL segmentations were manually refined in a masked fashion and follow-up scans for an eye were aligned to a common baseline. RNFLT data were divided into 45° sectors straddling the principle meridia. Rates of change were calculated per eye for mean deviation (MD), pointwise sensitivity at the 52 non-blindspot locations and RNFLT, both globally and for the RNFLT sectors. The worst eye per subject was selected, based on the rate of MD change (MDR), to increase the spread of rates of change available for analysis.
Results:
The mean number of OCT and SAP tests per eye were both 6.3±0.8 (range; 5 to 8) covering 2.9±0.36 yrs. At the most recent visit, mean MD, PSD and global RNFLT were -0.85±2.9dB, 2.53±2.5dB and 87.7±14.7μm respectively. The mean MDR was -0.34±0.46 dB/yr. The mean pointwise rates of change ranged from -0.65 to -0.03 dB/yr at the different visual field locations, with the nasal field deteriorating significantly faster than the temporal field (p=0.009). The mean rate of global RNFLT change was -1.15±1.52 μm/yr. Within OCT sectors the mean rate of RNFLT change ranged from -2.33 to -0.36 μm/yr and was more rapid in the temporal and superior sectors. The correlation (r) between MDR and global RNFLT change was 0.20 (p=0.008). However, MDR was more strongly correlated with rates of RNFLT change within temporal, superotemporal, inferior and inferotemporal sectors than it was with global RNFLT change. The strongest correlation between pointwise visual field change and sectoral RNFLT change was ≈ 0.5, more than double the correlation between MDR and global RNFLT change.
Conclusions:
Rates of functional and structural change in patients with glaucoma are significantly correlated when examined globally but even stronger correlations are observed in regional analyses.
Keywords: 642 perimetry •
610 nerve fiber layer