Objective

To measure the parapapillary atrophy (PPA) area in en face images obtained with swept-source optical coherence tomography (SS-OCT), and to evaluate its relationship to glaucoma, myopia, and age in non-highly myopic subjects.

Design

Retrospective, cross-sectional study.

Participants

Fifty eyes of 30 subjects with open-angle glaucoma (G group) and forty-three eyes of 26 healthy control subjects (C group). Eyes with high myopia (spherical equivalent refractive error ≤ -8 diopters or axial length ≥ 26.5 mm) were excluded.

Methods

Mean age ± standard deviation was 59.9 ± 12.4 years. The beta zone and the gamma zone PPA areas were measured in en face images reconstructed from three-dimensional SS-OCT images. Relationship between the PPA areas and patient characteristics such as glaucoma, axial length, and age was statistically evaluated using multivariate mixed-effects models.

Main outcome measures

Areas of the beta zone and the gamma zone PPA measured on en face OCT images.

Results

Average ± standard deviation area of the beta and the gamma zone was 0.64 ± 0.79 and 0.16 ± 0.30 mm2, respectively. In multivariate models, the gamma zone significantly correlated with axial length (P = 0.001) but not with glaucoma (P = 0.944). In contrast, the beta zone significantly correlated with age (P = 0.0249) and glaucoma (P = 0.014).

Conclusions

En face images reconstructed from 3D SS-OCT data facilitated measurements of the beta and the gamma PPA zones even in eyes with optic disc distortion. The OCT-defined beta zone is associated with glaucoma and age, whereas the gamma zone correlated with myopia but not with glaucoma. This study confirmed the clinical usefulness of OCT-based classification of the PPA zones in distinguishing glaucomatous damage of the optic nerve from myopic damage in non-highly myopic eyes.

Purpose

Trend analysis of visual field (VF) global indices may underestimate the rate of progression in severe glaucoma because of the influence of test points without detectable sensitivity. To test this hypothesis, we compared the rates of change of VF global indices with and without exclusion of undetectable points at various disease stages.

Materials and methods

Six hundred and forty-eight eyes of 366 glaucoma patients with 8 or more reliable 30-2 standard automated perimetry over more than 2 years were enrolled. We calculated targeted mean total deviation (TMTD) by averaging total deviation except points which were consistently undetectable in 3 baseline tests. Eyes were classified as early (≥-6 dB), moderate (-6 dB to -12 dB), advanced (-12 dB to -20 dB), and severe (<-20 dB) based on baseline mean deviation (MD). The rates of change of MD and TMTD in each stage were statistically compared.

Results

Mean age±SD at baseline was 56.9±11.9 years. The MD slope (-0.34 dB/y) in severe glaucoma was significantly slower than TMTD slope (-0.42 dB/y, P=0.028) and was slower than MD slopes in the other stages. Difference between MD slopes and TMTD slopes was most prominent in eyes with MD values less than -25 dB (P=0.002).

Conclusions

Undetectable locations in eyes with severe glaucoma may underestimate the rates of VF progression. Trend analysis of TMTD rather than global indices offers a practical and simple approach for alleviating underestimation of VF progression in severe glaucoma.