Impact of Glaucoma Severity on Rates of Neuroretinal Rim, Retinal Nerve Fiber Layer, and Macular Ganglion Cell Layer Thickness Change

Comparison of Retinal Nerve Fiber Layer and Ganglion Cell Complex Rates of Change in Patients With Moderate to Advanced Glaucoma

PURPOSE

To compare ganglion cell complex (GCC) and retinal nerve fiber layer (RNFL) rates of change (RoC) in eyes with central or moderate to advanced glaucoma.

DESIGN

Prospective cohort study.

PARTICIPANTS

A total of 918 matched macular and RNFL OCT scan pairs from 109 eyes (109 patients) enrolled in the Advanced Glaucoma Progression Study with ≥2 years of follow-up and ≥4 OCT scans.

METHODS

We exported GCC and RNFL thickness measurements in 49 central macular superpixels and 12 RNFL clock-hour sectors, respectively. We applied our latest Bayesian hierarchical longitudinal model to estimate population and subject-specific baseline thickness (intercepts) and rates of change (RoC) in macular superpixels and RNFL sectors. Global RNFL and GCC RoC were analyzed in a single bivariate longitudinal model to properly compare them accounting for the correlation between their RoC.

MAIN OUTCOME MEASURES

Proportion of significant negative (deteriorating) and positive (improving) RoC expressed in μm/year. Standardized RoC were calculated by dividing RoC by the corresponding population SD. Analyses were repeated in eyes with visual field mean deviation (MD) ≤-6 and > -6 dB.

RESULTS

Average (SD) 24-2 visual field MD and follow-up length were -8.6 (6.3) dB and 4.2 (0.5) years, respectively. Global RNFL RoC (-0.70 µm/year) were faster than GCC (-0.44 µm/year) (P < .001); corresponding normalized RoC were not significantly different (P = .052). In bivariate analysis, patients with a significant negative global RNFL RoC (n = 63, 57%) or GCC (n = 56, 51%) frequently did so for both outcomes (n = 49, 45%). The average proportion of significantly decreasing RNFL sectors within an eye was 30.7% in eyes with MD > -6 dB compared to 20.5% in those with MD ≤ -6 dB (P = .014); the proportions for GCC superpixels were 21.1% versus 18.7%, respectively (P = .63).

CONCLUSIONS

Both GCC and RNFL measures can detect structural progression in glaucoma patients with central damage or moderate to advanced glaucoma. The clinical utility of RNFL imaging decreases with worsening severity of glaucoma.

Progressive Changes in the Neuroretinal Rim and Retinal Nerve Fiber Layer in Glaucoma: Impact of Baseline Values and Floor Effects

PURPOSE

To determine whether more severe baseline damage impedes measurement of minimum rim width (MRW) and peripapillary retinal nerve fiber layer thickness (RNFLT) change in glaucoma patients because of a floor effect.

DESIGN

Prospective, longitudinal cohort study in a hospital-based setting.

PARTICIPANTS

The study included patients with open-angle glaucoma and healthy control subjects. Participants had at least 5 years of follow-up with OCT every 6 months.

METHODS

Baseline global and sectorial MRW and RNFLT values were classified as within normal limits, borderline, or outside normal limits based on reference normative values. Regression analysis was used to determine the magnitude and significance of MRW and RNFLT change. Additionally, the follow-up period for each participant was divided into 2 equal halves (first and second periods) to determine whether there was attenuation of MRW and RNFLT change with follow-up time.

MAIN OUTCOME MEASURES

Rates of global and sectoral MRW and RNFLT changes (slopes).

RESULTS

A total of 97 patients with glaucoma (median age, 70.3 years) and 42 healthy subjects (median age, 64.8 years) were followed for a median of 6.9 years and 7.0 years, respectively. The median mean deviation of the visual field in glaucoma patients was -4.30 decibels (dB) (interquartile range, -7.81 to -2.06 dB; range, -20.68 to 1.37 dB). Statistically significant changes in global and sectoral MRW and RNFLT were detected across all baseline classifications; however, there was a tendency for less change with increasing baseline damage. In glaucoma patients, RNFLT slopes, but not MRW slopes, were significantly more positive (less change) in the second period compared with the first. There were also no differences in MRW or RNFLT slopes in the first and second periods in healthy subjects.

CONCLUSIONS

Significant MRW and RNFLT changes were detected at all levels of baseline damage. However, an attenuation in the rate of RNFLT change compared with MRW indicates an earlier floor effect in RNFLT measurements globally and in equivalent sectors. Because the axonal component of these measurements should be equivalent, our results suggest important differences in tissue remodeling at the level of the optic nerve head and peripapillary retina.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Rates of choroidal loss and ganglion cell-inner plexiform layer thinning in type 2 diabetes mellitus and healthy individuals: a 2-year prospective study

AIMS

To investigate longitudinal choroid and ganglion cell-inner plexiform layer (GCIPL) changes in type 2 diabetes mellitus (T2DM) patients and healthy populations across 2 years.

METHODS

This prospective cohort study included T2DM patients and healthy controls. T2DM patients were divided into mild non-proliferative diabetic retinopathy (NPDR) or non-DR (NDR) groups. Macular choroidal and GCIPL thickness was measured using swept-source optical coherence tomography at baseline and follow-up after 2 years. A linear-mixed effect model compared rates of change in choroidal and GCIPL thicknesses between the three groups.

RESULTS

895 T2DM patients (770 in the NDR group and 125 in the NPDR group) and 847 healthy controls were included. Following 2 years, choroidal thinning occurred at a rate of -7.7±9.2 µm/year, -8.1±8.7 µm/year and -5.2±8.1 µm/year in NDR, NPDR and control groups, respectively (p<0.001). GCIPL loss occurred quickest in NPDR patients (-0.97±0.97 µm/year), followed by NDR (-0.91±0.89 µm/year) and the control group (-0.04±0.55 µm/year) (p<0.001). Following multivariate adjustment, choroidal thinning was -2.04 µm/year (95% CI: -4.05 to -0.03; p=0.047) and -1.95 µm/year (95% CI: -3.14 to -0.75; p=0.001) faster in NPDR and NDR groups than in the control group, respectively, and GCIPL thinning was -1.02 µm/year (95% CI: -1.19 to -0.84; p<0.001) and -0.88 µm/year (95% CI: -0.98 to -0.78; p<0.001) faster in the NPDR and NDR groups than in the control group, respectively.

CONCLUSION

Progressive choroidal and GCIPL thinning occurs in healthy individuals and T2DM patients; however, T2DM undergoes accelerated choroidal and GCIPL loss in NPDR patients.

Validation of the RCOphth and UKEGS glaucoma risk stratification tool 'GLAUC-STRAT-fast'

BACKGROUND/AIMS

The aim of this study was to validate the Glaucoma Risk Stratification Tool (GLAUC-STRAT-fast) currently recommended by the Royal College of Ophthalmologists for the risk stratification of patients with glaucoma in the UK National Health Service Hospital Eye Service.

METHODS

GLAUC-STRAT fast was applied to the LiGHT trial participants by risk-stratifying the worse eye of each patient at baseline and after 3 years of treatment. Metrics of disease severity or treatment intensity used for the validation were: increased number of monitoring visits or treatment escalations; needing a trabeculectomy; a reduction of >2 dB in visual field mean deviation (VF MD) during the monitoring period; identification of rapid VF loss on total (TD) and/or pattern deviation (PD). The proportion of eyes within each baseline stratum for each of the above markers was compared against the other strata, using a χ2 test for proportions.

RESULTS

There was an association between the baseline stratification and the number of treatment escalations needed to maintain the eye-specific target intraocular pressure (p=0.001), the number of visits needed throughout the 3-year follow-up period (p=0.001), the need for trabeculectomy (p<0.001) and absolute loss of MD over the course of the monitoring period (p<0.001). The rate of VF progression was not associated with baseline risk stratification for TD or PD progression (p≥0.007, with Bonferroni correction).

CONCLUSION

The GLAUC-STRAT fast tool is a useful tool for risk stratifying eyes with ocular hypertension or open angle glaucoma. Further research is needed to confirm and validate its applicability to more advanced glaucomas and generalisability to clinical use.

TRIAL REGISTRATION NUMBER

The LiGHT trial is registered at controlled-trials.com (ISRCTN32038223).