Outer retinal layer thickness in patients with glaucoma with horizontal hemifield visual field defects

Normative Database of the Superior-Inferior Thickness Asymmetry for All Inner and Outer Macular Layers of Adults for the Posterior Pole Algorithm of the Spectralis SD-OCT

BACKGROUND

This study aims to establish a reference for the superior-inferior hemisphere asymmetry in thickness values for all macular layers for the posterior pole algorithm (PPA) available for the Spectralis SD-OCT device.

METHODS

We examined 300 eyes of 300 healthy Caucasian volunteers aged 18-84 years using the PPA, composed of a grid of 64 (8 × 8) cells, to analyze the thickness asymmetries of the following automatically segmented macular layers: retinal nerve fiber layer (RNFL); ganglion cell layer (GCL); inner plexiform layer (IPL); inner nuclear layer (INL); outer plexiform layer (OPL); outer nuclear layer (ONL); retinal pigment epithelium (RPE); inner retina; outer retina; complete retina. Mean ± standard deviation and the 2.5th and 97.5th percentiles of the thickness asymmetry values were obtained for all the corresponding cells.

RESULTS

All the macular layers had significant superior-inferior thickness asymmetries. GCL, IPL, INL, ONL and RPE showed significantly greater thicknesses in the superior than the inferior hemisphere, whereas RNFL and OPL were thicker in the inferior hemisphere. The largest differences between hemispheres were for RNFL and ONL.

CONCLUSIONS

This is the first normative database of macular thickness asymmetries for the PPA and should be considered to distinguish normal from pathological values when interpreting superior-inferior macular asymmetries.

High sampling resolution optical coherence tomography reveals potential concurrent reductions in ganglion cell-inner plexiform and inner nuclear layer thickness but not in outer retinal thickness in glaucoma

PURPOSE

To analyse optical coherence tomography (OCT)-derived inner nuclear layer (INL) and outer retinal complex (ORC) measurements relative to ganglion cell-inner plexiform layer (GCIPL) measurements in glaucoma.

METHODS

Glaucoma participants (n = 271) were categorised by 10-2 visual field defect type. Differences in GCIPL, INL and ORC thickness were calculated between glaucoma and matched healthy eyes (n = 548). Hierarchical cluster algorithms were applied to generate topographic patterns of retinal thickness change, with agreement between layers assessed using Cohen's kappa (κ). Differences in GCIPL, INL and ORC thickness within and outside GCIPL regions showing the greatest reductions and Spearman's correlations between layer pairs were compared with 10-2 mean deviation (MD) and pattern standard deviation (PSD) to determine trends with glaucoma severity.

RESULTS

Glaucoma participants with inferior and superior defects presented with concordant GCIPL and INL defects demonstrating mostly fair-to-moderate agreement (κ = 0.145-0.540), which was not observed in eyes with no or ring defects (κ = -0.067-0.230). Correlations (r) with MD and PSD were moderate and weak in GCIPL and INL thickness differences, respectively (GCIPL vs. MD r = 0.479, GCIPL vs. PSD r = -0.583, INL vs. MD r = 0.259, INL vs. PSD r = -0.187, p = <0.0001-0.002), and weak in GCIPL-INL correlations (MD r = 0.175, p = 0.004 and PSD r = 0.154, p = 0.01). No consistent patterns in ORC thickness or correlations were observed.

CONCLUSIONS

In glaucoma, concordant reductions in macular INL and GCIPL thickness can be observed, but reductions in ORC thickness appear unlikely. These findings suggest that trans-synaptic retrograde degeneration may occur in glaucoma and could indicate the usefulness of INL thickness in evaluating glaucomatous damage.

The thickness of the outer retina in the macula and circumpapillary area in patients with unilateral advanced glaucoma

PURPOSE

To compare outer macular and retinal thickness in the circumpapillary area in unilateral advanced glaucomatous eyes to the normal or mild glaucomatous fellow eyes.

METHODS

Seventy-eight eyes of 39 patients with unilateral advanced glaucoma (mean deviation (MD) worse than -12.00 dB based on visual field 24-2) were included in this cross-sectional study as the cases. The healthy or mild glaucomatous fellow eyes were enrolled as the control group. All eyes underwent optical coherence tomography of the macula and circumpapillary retina by Topcon DRI Triton (Topcon, Tokyo, Japan). Ganglion cell layer 2+ was considered as the inner retina. Total retinal thickness minus the thickness of the inner retina was considered as the outer retina. Comparison between groups was done by paired-sample sign test. The correlation between structural and functional parameters was evaluated by a partial correlation coefficient.

RESULTS

Seventeen (43.6%), 15 (38.5%), and 7 (17.9%) patients had pseudoexfoliation, primary angle-closure, and primary open-angle glaucoma, respectively. The mean age was 62.69 ± 12.00 years. Thirty-three (84.6%) patients were male. The outer retinal thickness in the circumpapillary area was higher in temporal, superior, and inferior quadrants (p < 0.05). The outer macula in different parafoveal and perifoveal quadrants was also thicker (p < 0.05). Average outer parafoveal thickness in the case group had a significant negative correlation with MD (r = -0.339; p = 0.035).

CONCLUSION

Advanced glaucomatous eyes had a thicker outer retina in the macula and circumpapillary area. There was a significant negative correlation between outer perifoveal thickness and MD.

Ganglion Cell Complex: The Optimal Measure for Detection of Structural Progression in the Macula

PURPOSE

To test the hypothesis that macular ganglion cell complex (GCC) thickness from optical coherence tomography (OCT) provides a stronger change signal regardless of glaucoma severity compared with other macular measures.

DESIGN

Prospective cohort study.

METHODS

Eyes were from 112 patients with moderate to severe glaucoma at baseline from a tertiary glaucoma center. In each 3° × 3° macular superpixel, a hierarchical Bayesian random intercept and slope model with random residual variance was fit to longitudinal full macular thickness (FMT), outer retina layers, GCC, ganglion cell-inner plexiform layer (GCIPL), and ganglion cell layer (GCL) measurements. We estimated population- and individual-level slopes and intercepts. Proportions of substantial worsening and improving superpixel slopes were compared between layers and in superpixels with mild to moderate vs severe damage (total deviation of corresponding visual field location ≥ -8 vs < -8 dB).

RESULTS

Mean (SD) follow-up time and baseline 10-2 visual field mean deviation were 3.6 (0.4) years and -8.9 (5.9) dB, respectively. FMT displayed the highest proportion of significant negative slopes (1932/3519 [54.9%]), followed by GCC (1286/3519 [36.5%]), outer retina layers (1254/3519 [35.6%]), (GCIPL) (1075/3518 [30.6%]), and (GCL) (698/3518 [19.8%]). Inner macular measures detected less worsening in the severe glaucoma group; yet GCC (223/985 [22.6%]) identified the highest proportion (GCIPL: 183/985 [18.6%]; GCL: 106/985 [10.8%]). Proportions of positive rates were small and comparable among all measures.

CONCLUSIONS

GCC is the optimal macular measure for detection of structural change in eyes with moderate to severe glaucoma. Although a higher proportion of worsening superpixels was observed for FMT, a large portion of FMT change could be attributed to changes in outer retina layers.

An inducible rodent glaucoma model that exhibits gradual sustained increase in intraocular pressure with distinct inner retina and optic nerve inflammation

Glaucoma is a chronic and progressive neurodegenerative disease of the optic nerve resulting in loss of retinal ganglion cells (RGCs) and vision. The most prominent glaucoma risk factor is increased intraocular pressure (IOP), and most models focus on reproducing this aspect to study disease mechanisms and targets. Yet, current models result in IOP profiles that often do not resemble clinical glaucoma. Here we introduce a new model that results in a gradual and sustained IOP increase over time. This approach modifies a circumlimbal suture method, taking care to make the sutures 'snug' instead of tight, without inducing an initial IOP spike. This approach did not immediately affect IOPs, but generated gradual ocular hypertension (gOHT) as the sutures tighten over time, in comparison to loosely sutured control eyes (CON), resulting in an average 12.6 mmHg increase in IOP at 17 weeks (p < 0.001). Corresponding characterization revealed relevant retinal and optic nerve pathology, such as thinning of the retinal nerve fiber layer, decreased optokinetic response, RGC loss, and optic nerve head remodeling. Yet, angles remained open, with no evidence of inflammation. Corresponding biochemical profiling indicated significant increases in TGF-β2 and 3, and IL-1 family cytokines in gOHT optic nerve tissues compared to CON, with accompanying microglial reactivity, consistent with active tissue injury and repair mechanisms. Remarkably, this signature was absent from optic nerves following acute ocular hypertension (aOHT) associated with intentionally tightened sutures, although the resulting RGC loss was similar in both methods. These results suggest that the pattern of IOP change has an important impact on underlying pathophysiology.

Age and intraocular pressure in murine experimental glaucoma

Age and intraocular pressure (IOP) are the two most important risk factors for the development and progression of open-angle glaucoma. While IOP is commonly considered in models of experimental glaucoma (EG), most studies use juvenile or adult animals and seldom older animals which are representative of the human disease. This paper provides a concise review of how retinal ganglion cell (RGC) loss, the hallmark of glaucoma, can be evaluated in EG with a special emphasis on serial in vivo imaging, a parallel approach used in clinical practice. It appraises the suitability of EG models for the purpose of in vivo imaging and argues for the use of models that provide a sustained elevation of IOP, without compromise of the ocular media. In a study with parallel cohorts of adult (3-month-old, equivalent to 20 human years) and old (2-year-old, equivalent to 70 human years) mice, we compare the effects of elevated IOP on serial ganglion cell complex thickness and individual RGC dendritic morphology changes obtained in vivo. We also evaluate how age modulates the impact of elevated IOP on RGC somal and axonal density in histological analysis as well the density of melanopsin RGCs. We discuss the challenges of using old animals and emphasize the potential of single RGC imaging for understanding the pathobiology of RGC loss and evaluating new therapeutic avenues.

Early localized alterations of the retinal inner plexiform layer in association with visual field worsening in glaucoma patients

Glaucoma is a chronic neurodegenerative disease of the optic nerve and a leading cause of irreversible blindness, worldwide. While the experimental research using animal models provides growing information about cellular and molecular processes, parallel analysis of the clinical presentation of glaucoma accelerates the translational progress towards improved understanding, treatment, and clinical testing of glaucoma. Optic nerve axon injury triggers early alterations of retinal ganglion cell (RGC) synapses with function deficits prior to manifest RGC loss in animal models of glaucoma. For testing the clinical relevance of experimental observations, this study analyzed the functional correlation of localized alterations in the inner plexiform layer (IPL), where RGCs establish synaptic connections with retinal bipolar and amacrine cells. Participants of the study included a retrospective cohort of 36 eyes with glaucoma and a control group of 18 non-glaucomatous subjects followed for two-years. The IPL was analyzed on consecutively collected macular SD-OCT scans, and functional correlations with corresponding 10–2 visual field scores were tested using generalized estimating equations (GEE) models. The GEE-estimated rate of decrease in IPL thickness (R = 0.36, P<0.001) and IPL density (R = 0.36, P<0.001), as opposed to unchanged or increased IPL thickness or density, was significantly associated with visual field worsening at corresponding analysis locations. Based on multivariate logistic regression analysis, this association was independent from the patients’ age, the baseline visual field scores, or the baseline thickness or alterations of retinal nerve fiber or RGC layers (P>0.05). These findings support early localized IPL alterations in correlation with progressing visual field defects in glaucomatous eyes. Considering the experimental data, glaucoma-related increase in IPL thickness/density might reflect dendritic remodeling, mitochondrial redistribution, and glial responses for synapse maintenance, but decreased IPL thickness/density might correspond to dendrite atrophy. The bridging of experimental data with clinical findings encourages further research along the translational path.

Comparison of Rates of Progression of Macular OCT Measures in Glaucoma

Purpose

The purpose of this study was to compare rates of change of various macular thickness measures and evaluate the influence of baseline damage on macular rates of change.

Methods

One hundred twelve eyes (112 patients) with ≥ 2 years of follow-up and ≥ 5 macular optical coherence tomography (OCT) images and 10-2 visual field (VF) tests were included. OCT measures of interests were full macular thickness (FMT), ganglion cell complex (GCC), ganglion cell/inner plexiform layer (GCIPL), ganglion cell layer (GCL), and outer retinal layer (ORL) thickness in 3° × 3° superpixels. Rates of change were estimated with linear regression and normalized by dividing rates by the average normative superpixel thickness. We compared rates of change and proportion of significantly worsening superpixels (detection rate) and improving superpixels (false discovery rate [FDR]) among macular measures as a function of baseline thickness and 10-2 VF status.

Results

Median (interquartile range [IQR]) baseline VF mean deviation, follow-up time, and number of VFs/OCTs were -7.6 dB (-11.8 to -3.8 dB), 4.5 years (4.0-5.0 years), and 9 (8-10), respectively. Normalized FMT and GCC rates of change were faster and detection rates were higher than GCIPL and GCL (P < 0.001), but FMT had lower FDR than GCC (P = 0.02); faster FMT rates were partially explained by ORL rates of change. GCC detection rates were less likely than GCIPL and GCL rates to decrease with diminishing baseline thickness or worse VF damage. In eyes with 10-2 VF worsening, GCC and GCL demonstrated the fastest rates of change.

Conclusions

GCC measurements are most likely to detect structural worsening along the spectrum of glaucoma severity. Although FMT rates of change are least influenced by baseline thickness, they partially reflect likely age-related ORL changes.

Translational Relevance

GCC thickness measurements seem to be the optimal macular outcome measure for detection of glaucoma deterioration.

Glaucomatous Maculopathy: Thickness Differences on Inner and Outer Macular Layers between Ocular Hypertension and Early Primary Open-Angle Glaucoma Using 8 × 8 Posterior Pole Algorithm of SD-OCT

The purpose of this study was to compare the thickness of all inner and outer macular layers between ocular hypertension (OHT) and early primary open-angle glaucoma (POAG) using spectral domain optical coherence tomography (SD-OCT) 8 × 8 posterior pole algorithm (8 × 8 PPA). Fifty-seven eyes of 57 OHT individuals and fifty-seven eyes of 57 early POAG patients were included. The thickness of macular retinal nerve fiber layer (mRNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform and nuclear layer, photoreceptor layer (PRL) and retinal pigment epithelium were obtained in 64 cells for each macular layer and mean thickness of superior and inferior hemispheres was also calculated. Thinning of superior and inferior hemisphere mean thickness in mRNFL, GCL and IPL and thickening of superior and inferior hemisphere mean thickness in PRL and inferior hemisphere in INL were found in early GPAA group. Otherwise, heatmaps representing cell-to-cell comparisons showed thinning patterns in inner retinal layers (except for INL) and thickening patterns in outer retinal layers in GPAA group. We found that 8 × 8 PPA not only allows the detection of significant thinning patterns in inner retinal layers, but also thickening patterns in outer retinal layers when comparing early POAG eyes to OHT eyes.

Longitudinal Macular Structure-Function Relationships in Glaucoma

PURPOSE

To investigate the relationship between longitudinal changes in macular thickness measurements from OCT and changes in central visual field (VF) in patients with glaucoma with central or advanced damage at baseline.

DESIGN

Longitudinal cohort study.

PARTICIPANTS

A total of 116 eyes with ≥3 years of follow-up and ≥5 macular OCT images and central 10° VF tests were selected.

METHODS

OCT superpixels and VF locations were matched correcting for retinal ganglion cell (RGC) displacement. Superpixel thickness and VF total deviation (TD) values, in both logarithmic and linear scales, were averaged within 3 eccentricities (3.4°, 5.6°, and 6.8°) and superior and inferior hemiretinas and hemifields. We estimated pointwise TD rates of change and rates of change at superpixels for full macular thickness (FMT), ganglion cell complex (GCC), ganglion cell inner plexiform layer (GCIPL), and ganglion cell layer (GCL). Correlation of structure-function (SF) rates of change was investigated with parametric tests. We compared the proportion of worsening and positive slopes for superpixels and VF test locations (negative vs. positive rates of change with P < 0.05) throughout the follow-up period. Permutation analyses were used to control specificity.

MAIN OUTCOME MEASURES

Magnitude of correlation between structural and functional rates of change and proportion of worsening and positive slopes as a function of follow-up time.

RESULTS

The median (interquartile range) follow-up and number of exams were 4.2 (3.7-4.6) years and 8 (7-9), respectively. The highest correlation of change rates was observed at 3.4° and 5.6° eccentricities (r = 0.24, 0.41, 0.40, and 0.40 for FMT, GCC, GCIPL, and GCL for 3.4° eccentricity and r = 0.28, 0.32, 0.31, and 0.32 for FMT, GCC, GCIPL, and GCL for 5.6° eccentricity, respectively). Although GCC measures demonstrated the highest overall longitudinal SF correlations, the differences were not statistically significant. Significant structural worsening was more frequently detected than functional deterioration at 3- and 5-year time points (P < 0.025). Permutation analyses also confirmed this finding.

CONCLUSIONS

Correlations between central structural and functional rates of change were weak to fair in this cohort. Structural changes were detected more frequently than functional changes. Measurements of both structure and function are required for optimal detection of central progression.

Differential Effects of Aging in the Macular Retinal Layers, Neuroretinal Rim, and Peripapillary Retinal Nerve Fiber Layer

PURPOSE

We determined the differential aging effects of the inner 6 layers of the macula in contrast to the minimum neuroretinal rim width (MRW) and peripapillary retinal nerve fiber layer (RNFL) thickness.

DESIGN

Cross-sectional, multicenter study.

PARTICIPANTS

An approximately equal number of white subjects with a normal ocular and visual field examination in each decade group from 20 to 90 years.

METHODS

OCT of the macula, optic nerve head, and peripapillary retina.

MAIN OUTCOME MEASURES

Sectoral measurements of the inner 6 layers of the macula; age-related decline of each of these layers; strength of the associations with age of the macular parameters, MRW, and peripapillary RNFL thickness; and association between ganglion cell layer (GCL) thickness and MRW and peripapillary RNFL thickness.

RESULTS

The study sample comprised 1 eye of 246 subjects with a median (range) age of 52.9 (19.8-87.3) years. Of the 6 layers, there was a statistically significant decline with age of only the GCL, inner plexiform layer, and inner nuclear layer thickness with rates of -0.11 μm/year, -0.07 μm/year, and -0.03 μm/year, respectively. These rates corresponded to 2.82%, 2.10%, and 0.78% loss per decade, respectively, and were generally uniform across sectors. The rate of loss of MRW and peripapillary RNFL thickness was -1.22 μm/year and -0.20 μm/year, corresponding to 3.75% and 2.03% loss per decade. However, the association of GCL thickness change with age (R² = 0.28) was approximately twice that of MRW and RNFL thickness (R² = 0.14 for each).

CONCLUSIONS

In concordance with histopathologic studies showing age-related loss of retinal ganglion cell axons, we showed a significant decline in GCL thickness, as well as MRW and peripapillary RNFL thickness. The stronger relationship between aging and GCL thickness compared with the rim or peripapillary RNFL may indicate that GCL thickness could be better suited to measure progression of structural glaucomatous loss.

Comparison of retinal ganglion cell-related layer asymmetry between early glaucoma eyes with superior and inferior hemiretina damage

Aim

To compare retinal ganglion cell (RGC)-related layer thickness asymmetry between early open-angle glaucoma (EG) eyes with superior and inferior hemiretina damage.

Methods

This was a retrospective study including 95 EG eyes (mean deviation >−2 dB, including 43 preperimetric glaucoma eyes) with photographically determined glaucomatous retinal nerve fibre layer defect and disc change confined to one hemiretina, and 93 age, sex and refraction matched normal subjects as controls. Ganglion cell complex, ganglion cell layer+inner plexiform layer and circumpapillary retinal nerve fibre layer thickness measured by spectral domain optical coherence imaging were compared between the affected and unaffected hemiretinae within each glaucoma eye as well as to those of the corresponding hemiretina of normal control eyes.

Results

Intraeye comparison revealed that there was no significant difference in all parameters between the affected and unaffected hemiretinae in eyes with superior hemiretina damage (p=0.110~0.343) while all parameters were thinner in the affected inferior hemiretina compared with the unaffected superior hemiretina in eyes with inferior hemiretina damage (p<0.001). The affected hemiretina of both groups were thinner compared with normal controls (p<0.001). All parameters of the unaffected hemiretina of eyes with superior hemiretina damage were thinner than normal controls (p<0.001), while eyes with inferior hemiretina damage showed no significant difference compared with those of their corresponding hemiretina of normal eyes (p=0.086~0.924).

Conclusion

The pattern of RGC damage in early stage glaucoma may differ depending on which horizontal hemiretina is affected first.