Aims To compare the changes in the macular retinal nerve fibre layer (mRNFL), macular ganglion cell layer and inner plexiform layer (mGCIPL), and circumpapillary retinal nerve fibre layer (cpRNFL) in various stages of normal tension glaucoma (NTG) using spectral domain optical coherence tomography.
Methods Eyes with NTG (n=218) were assigned into three groups based on initial mean deviation (MD) as follows: mild (MD>−6 dB), moderate (−6 dB≥MD≥−12 dB) and severe (−12 dB>MD>−20 dB). Annual rates of change in mRNFL, mGCIPL and cpRNFL thickness were calculated by linear regression analysis.
Results Age, gender, spherical equivalent, and average intraocular pressure during follow-up were not significantly different among the three groups. There were significant differences in the mRNFL, mGCIPL and cpRNFL among the three groups at baseline (p<0.0001 in all sectors except for the mRNFL in the superonasal sector). The average thinning rates of the mRNFL, mGCIPL and cpRNFL were −0.38±0.32 µm/year, −0.62±0.46 µm/year and −0.86±0.83 µm/year, respectively. No significant difference in the rates of change in the mRNFL and mGCIPL were found among the groups in any sector. However, there was a significant difference in the rate of change in the cpRNFL among the groups (in all sectors: p<0.0001).
Conclusions Changes in the mRNFL and mGCIPL can reflect the progression of NTG even in its advanced stage. However, careful interpretation of changes in the cpRNFL in the advanced stage of glaucoma is warranted due to a potential floor effect.
- optical coherence tomography
- normal tension glaucoma
- macular retinal nerve fiber layer
- macular ganglion cell layer and inner plexiform layer
- circumpapillary retinal nerve fiber layer
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Contributors Concept and design: AS. Data collection: HI and MI. Data analysis: HI and AS. Manuscript writing: HI, AS and TY. Interpretation of data: AS and TY.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval All procedures were approved by the Institutional Review Board of Gifu University Graduate School of Medicine.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon request.