Abstract
Purpose :
To determine whether the baseline classification (BC) of sectoral neuroretinal minimal rim width (MRW) and peripapillary retinal nerve fibre layer thickness (RNFLT) impacted the ability to determine further change due to a floor effect.
Methods :
Data were obtained from a prospective study of glaucoma patients imaged at 6-month intervals. The MRW and RNFLT values of one study eye per patient at each visit were derived from optical coherence tomography (Spectralis OCT2, Heidelberg Engineering) scans oriented and analysed in fovea to Bruch’s membrane opening angle coordinates. We determined sectoral MRW and RNFLT change as a function of BC (within normal limits [WNL], baseline [BL] and outside normal limits [ONL]) with least squares regression.
Results :
The study contained 119 patients with median age of 71.2 years age, visual field mean deviation of -4.31 dB, follow-up of 6.9 years with 14 follow-up visits. For MRW, sectoral BC of WNL, BL and ONL varied from 17%-47%, 16%-30% and 34%-67%, respectively. The corresponding BC for RNFLT were 16%-61%, 10-29% and 10%-73%. For all sectors, the rate of both MRW and RNFLT change was weakly related to the corresponding baseline values (Fig. 1). There was no difference in the rate of sectoral MRW change among BC groups, except for inferior nasal and no differences in the proportion of statistically significant slopes among the BC groups (Fig. 2). In slight contrast, rates of temporal, superior temporal and superior nasal RNFLT change were significantly different among the BC groups with WNL having the largest change and ONL the least. Furthermore, a greater number of slopes in the superior temporal and superior nasal quadrants were significant (Fig. 2).
Conclusions :
There was little evidence to suggest that further changes in MRW cannot be detected in sectors with a baseline ONL classification. There was a tendency for RNFLT to demonstrate a weak floor effect in some sectors.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.