Abstract
Purpose :
Axial length (AL) is a key anatomical factor that influence the mapping from visual field to the peripapillary retinal ganglion cell axon, whereas the exact extent of the impact remains unclear. This study explored the effect of AL on the relationship between the changes in OCT-based parameters, such as Bruch's membrane opening-minimum rim width (BMO-MRW), and retinal nerve fiber layer (RNFL) thickness, and the visual field (VF) defect values in primary open angle glaucoma (POAG) and seek the threshold value where rapid VF progression occurs.
Methods :
This cross-sectional study included 108 POAG eyes with different AL (21.91mm to 32.26mm), MD (-27.97dB to -0.18dB), BCVA (LogMAR 0.00 to 1.70). All participants underwent Heidelberg spectral-domain OCT and Humphrey visual field analyzer examination. Global and sectoral BMO-MRW and RNFL thickness was correlated with the corresponding VF deviation according to the Garway-Heath map. Using the Best Subset Selection, the effect of AL on the structure–function relationship was compared between global and all sectors. The threshold values of BMO-MRW and RNFL thickness where rapid VF progression occurs were determined by the use of Cubic Splines.
Results :
After converting all the decibel values into linear scale, we established linear models that relates the loss in BMO-MRW and RNFL thickness to the loss in VF sensitivity for global and each sector. When AL was added as a covariable, only the temporal BMO-MRW model (p=0.001) and temporal RNFL thickness model (p=0.009) fitted notably better according to the Bayesian Information Criterion. Based on the best fitted models, the inflection point of BMO-MRW and RNFL thickness for rapid VF progression was 199.48μm and 76.78μm in global, 128.57μm and 39.78μm in temporal, 111.61μm and 92.45μm in temporal-superior, 228.33μm and 84.85μm in temporal-inferior, 234.94μm and 57.71μm in nasal, 233.96μm and 95.12μm in nasal-superior, 200.15μm and 65.61μm in nasal-inferior.
Conclusions :
Our findings indicated that AL could influence the structure-function relationship of POAG eyes in the temporal sector. Correcting OCT measurements with AL results in a better match between structural damage and functional impairment. Further personalized diagnostic criteria based on large samples need to be explored, especially in glaucoma with high myopia.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.