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Experimental Glaucoma Causes Optic Nerve Head Neural Rim Tissue Compression: A Potentially Important Mechanism of Axon Injury

View Article: PubMed Central - PubMed

ABSTRACT

Purpose: We tested the hypothesis that experimental glaucoma (EG) results in greater thinning of the optic nerve head (ONH) neural rim tissue than the peripapillary retinal nerve fiber layer (RNFL) tissue.

Methods: Longitudinal spectral-domain optical coherence tomography (SDOCT) imaging of the ONH and peripapillary RNFL was performed every other week under manometric IOP control (10 mm Hg) in 51 nonhuman primates (NHP) during baseline and after induction of unilateral EG. The ONH parameter minimum rim area (MRA) was derived from 80 radial B-scans centered on the ONH; RNFL cross-sectional area (RNFLA) from a peripapillary circular B-scan with 12° diameter.

Results: In control eyes, MRA was 1.00 ± 0.19 mm2 at baseline and 1.00 ± 0.19 mm2 at the final session (P = 0.77), while RNFLA was 0.95 ± 0.09 and 0.95 ± 0.10 mm2, respectively (P = 0.96). In EG eyes, MRA decreased from 1.00 ± 0.19 mm2 at baseline to 0.63 ± 0.21 mm2 at the final session (P < 0.0001), while RNFLA decreased from 0.95 ± 0.09 to 0.74 ± 0.19 mm2, respectively (P < 0.0001). Thus, MRA decreased by 36.4 ± 20.6% in EG eyes, significantly more than the decrease in RNFLA (21.7 ± 19.4%, P < 0.0001). Other significant changes in EG eyes included increased Bruch's membrane opening (BMO) nonplanarity (P < 0.05), decreased BMO aspect ratio (P < 0.0001), and decreased MRA angle (P < 0.001). Bruch's membrane opening area did not change from baseline in either control or EG eyes (P = 0.27, P = 0.15, respectively).

Conclusions: Optic nerve head neural rim tissue thinning exceeded peripapillary RNFL thinning in NHP EG. These results support the hypothesis that axon bundles are compressed transversely within the ONH rim along with glaucomatous deformation of connective tissues.

No MeSH data available.


Related in: MedlinePlus

Longitudinal change in MRA (left) versus RNFLA (right) expressed relative to baseline values. Box plots represent the distribution (median, interquartile range and extremes, N = 51) of changes in parameter values at the final imaging session expressed as a percentage of the baseline average value for each eye. Control eyes (CTL) shown in gray and eyes with EG are shown in red for MRA and in gold for RNFLA. The group average (± SD) and median values of change are listed for the EG eyes.
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i1552-5783-57-10-4403-f04: Longitudinal change in MRA (left) versus RNFLA (right) expressed relative to baseline values. Box plots represent the distribution (median, interquartile range and extremes, N = 51) of changes in parameter values at the final imaging session expressed as a percentage of the baseline average value for each eye. Control eyes (CTL) shown in gray and eyes with EG are shown in red for MRA and in gold for RNFLA. The group average (± SD) and median values of change are listed for the EG eyes.

Mentions: In Figure 4 the magnitude of longitudinal MRA change is compared to the magnitude of RNFLA change. Minimum rim area decreased by 36.4 ± 20.6% in EG eyes, which was significantly more than the RNFLA decrease (21.7 ± 19.4%, P < 0.0001, paired t-test). Although these distributions of change passed a formal normality test in both cases (P = 0.36 for MRA, P = 0.06 for RNFLA, D'Agostino and Pearson omnibus test), the latter was borderline for RNFLA, so the data also were compared nonparametrically, which also found that the MRA change (median decrease of 31%) was significantly greater than the RNFLA change (median decrease of 17%, P < 0.0001, Wilcoxon matched-pairs signed rank test). Notwithstanding that there was a significant difference between the magnitude of MRA loss versus RNFLA loss, longitudinal change for these two parameters was strongly correlated (Pearson R = 0.84; 95% confidence interval, 0.74–0.91; P < 0.0001).


Experimental Glaucoma Causes Optic Nerve Head Neural Rim Tissue Compression: A Potentially Important Mechanism of Axon Injury
Longitudinal change in MRA (left) versus RNFLA (right) expressed relative to baseline values. Box plots represent the distribution (median, interquartile range and extremes, N = 51) of changes in parameter values at the final imaging session expressed as a percentage of the baseline average value for each eye. Control eyes (CTL) shown in gray and eyes with EG are shown in red for MRA and in gold for RNFLA. The group average (± SD) and median values of change are listed for the EG eyes.
© Copyright Policy - cc-by-nc-nd
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC5016000&req=5

i1552-5783-57-10-4403-f04: Longitudinal change in MRA (left) versus RNFLA (right) expressed relative to baseline values. Box plots represent the distribution (median, interquartile range and extremes, N = 51) of changes in parameter values at the final imaging session expressed as a percentage of the baseline average value for each eye. Control eyes (CTL) shown in gray and eyes with EG are shown in red for MRA and in gold for RNFLA. The group average (± SD) and median values of change are listed for the EG eyes.
Mentions: In Figure 4 the magnitude of longitudinal MRA change is compared to the magnitude of RNFLA change. Minimum rim area decreased by 36.4 ± 20.6% in EG eyes, which was significantly more than the RNFLA decrease (21.7 ± 19.4%, P < 0.0001, paired t-test). Although these distributions of change passed a formal normality test in both cases (P = 0.36 for MRA, P = 0.06 for RNFLA, D'Agostino and Pearson omnibus test), the latter was borderline for RNFLA, so the data also were compared nonparametrically, which also found that the MRA change (median decrease of 31%) was significantly greater than the RNFLA change (median decrease of 17%, P < 0.0001, Wilcoxon matched-pairs signed rank test). Notwithstanding that there was a significant difference between the magnitude of MRA loss versus RNFLA loss, longitudinal change for these two parameters was strongly correlated (Pearson R = 0.84; 95% confidence interval, 0.74–0.91; P < 0.0001).

View Article: PubMed Central - PubMed

ABSTRACT

Purpose: We tested the hypothesis that experimental glaucoma (EG) results in greater thinning of the optic nerve head (ONH) neural rim tissue than the peripapillary retinal nerve fiber layer (RNFL) tissue.

Methods: Longitudinal spectral-domain optical coherence tomography (SDOCT) imaging of the ONH and peripapillary RNFL was performed every other week under manometric IOP control (10 mm Hg) in 51 nonhuman primates (NHP) during baseline and after induction of unilateral EG. The ONH parameter minimum rim area (MRA) was derived from 80 radial B-scans centered on the ONH; RNFL cross-sectional area (RNFLA) from a peripapillary circular B-scan with 12&deg; diameter.

Results: In control eyes, MRA was 1.00 &plusmn; 0.19 mm2 at baseline and 1.00 &plusmn; 0.19 mm2 at the final session (P = 0.77), while RNFLA was 0.95 &plusmn; 0.09 and 0.95 &plusmn; 0.10 mm2, respectively (P = 0.96). In EG eyes, MRA decreased from 1.00 &plusmn; 0.19 mm2 at baseline to 0.63 &plusmn; 0.21 mm2 at the final session (P &lt; 0.0001), while RNFLA decreased from 0.95 &plusmn; 0.09 to 0.74 &plusmn; 0.19 mm2, respectively (P &lt; 0.0001). Thus, MRA decreased by 36.4 &plusmn; 20.6% in EG eyes, significantly more than the decrease in RNFLA (21.7 &plusmn; 19.4%, P &lt; 0.0001). Other significant changes in EG eyes included increased Bruch's membrane opening (BMO) nonplanarity (P &lt; 0.05), decreased BMO aspect ratio (P &lt; 0.0001), and decreased MRA angle (P &lt; 0.001). Bruch's membrane opening area did not change from baseline in either control or EG eyes (P = 0.27, P = 0.15, respectively).

Conclusions: Optic nerve head neural rim tissue thinning exceeded peripapillary RNFL thinning in NHP EG. These results support the hypothesis that axon bundles are compressed transversely within the ONH rim along with glaucomatous deformation of connective tissues.

No MeSH data available.


Related in: MedlinePlus