Impact of myopia on the association of long-term intraocular pressure fluctuation with the rate of progression in normal-tension glaucoma

Background/Aims To investigate whether the association of long-term intraocular pressure (IOP) fluctuation with the rate of progression of normal-tension glaucoma (NTG) differs between myopia and non-myopia. Methods The medical records of 65 myopic NTG (axial length (AL) > 24.0 mm) and 64 non-myopic NTG eyes (AL < 24.0 mm), who had been treated with topical medications for more than 5 years, were reviewed. Multiple linear regression models were fitted to analyse the relationships of the slope of mean deviation (MD) or visual field index (VFI) with the clinical factors, including the interactions with myopia. Results The average follow-up period was 8.3 years. Twenty-two (22) non-myopic eyes (34.4%) and 27 myopic eyes (41.5%) showed NTG progression (p=0.511). The interaction of myopia with IOP fluctuation was a significant factor regarding both MD and VFI slope (p=0.002, 0.024, respectively); stratified analyses suggested that the risk effect of IOP fluctuation was significant only in myopic NTG in terms of both MD (β= −1.27, p=0.003) and VFI slope (β=−2.32, p=0.011). Conclusion Long-term IOP fluctuation was significantly related to faster visual field progression in myopic NTG eyes, compared with non-myopic NTG eyes.