Limits...
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.


Longitudinal change in minimum rim area (MRA, left) versus RNFL area (RNFLA, right). Box plots represent the distribution (median, interquartile range, and extremes, N = 51) of raw parameter values in control eyes (CTL) and eyes with EG at baseline (BL, hatched) and at the final imaging session (MRA for EG eyes in solid red, RNFLA for EG eyes in solid gold to match Fig. 1 color scheme).
© Copyright Policy - cc-by-nc-nd
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5016000&req=5

i1552-5783-57-10-4403-f03: Longitudinal change in minimum rim area (MRA, left) versus RNFL area (RNFLA, right). Box plots represent the distribution (median, interquartile range, and extremes, N = 51) of raw parameter values in control eyes (CTL) and eyes with EG at baseline (BL, hatched) and at the final imaging session (MRA for EG eyes in solid red, RNFLA for EG eyes in solid gold to match Fig. 1 color scheme).

Mentions: Figure 3 shows the distribution of raw parameter values found at baseline (hatched boxes) and at the final imaging session for the entire group of N = 51 NHPs. As predicted by the hypothesis, the total cross-sectional area of ONH rim tissue was very close to the total cross-sectional area of peripapillary RNFL tissue (∼1.0 mm2), though the population variance was larger for MRA than for RNFLA. Figure 3 also shows that MRA and RNFLA parameter values are repeatable from baseline to the final session in control eyes. 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, paired t-test). Minimum rim area decreased in EG eyes from 1.00 ± 0.19 mm2 at baseline to 0.63 ± 0.21 mm2 at the final session (P < 0.0001). Retinal nerve fiber layer area in control eyes was 0.95 ± 0.09 mm2 at baseline and 0.95 ± 0.10 mm2 at the final session (P = 0.96). Retinal nerve fiber layer area decreased in EG eyes from 0.95 ± 0.09 mm2 at baseline to 0.74 ± 0.19 mm2 at the final session (P < 0.0001).


Experimental Glaucoma Causes Optic Nerve Head Neural Rim Tissue Compression: A Potentially Important Mechanism of Axon Injury
Longitudinal change in minimum rim area (MRA, left) versus RNFL area (RNFLA, right). Box plots represent the distribution (median, interquartile range, and extremes, N = 51) of raw parameter values in control eyes (CTL) and eyes with EG at baseline (BL, hatched) and at the final imaging session (MRA for EG eyes in solid red, RNFLA for EG eyes in solid gold to match Fig. 1 color scheme).
© Copyright Policy - cc-by-nc-nd
Related In: Results  -  Collection

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

i1552-5783-57-10-4403-f03: Longitudinal change in minimum rim area (MRA, left) versus RNFL area (RNFLA, right). Box plots represent the distribution (median, interquartile range, and extremes, N = 51) of raw parameter values in control eyes (CTL) and eyes with EG at baseline (BL, hatched) and at the final imaging session (MRA for EG eyes in solid red, RNFLA for EG eyes in solid gold to match Fig. 1 color scheme).
Mentions: Figure 3 shows the distribution of raw parameter values found at baseline (hatched boxes) and at the final imaging session for the entire group of N = 51 NHPs. As predicted by the hypothesis, the total cross-sectional area of ONH rim tissue was very close to the total cross-sectional area of peripapillary RNFL tissue (∼1.0 mm2), though the population variance was larger for MRA than for RNFLA. Figure 3 also shows that MRA and RNFLA parameter values are repeatable from baseline to the final session in control eyes. 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, paired t-test). Minimum rim area decreased in EG eyes from 1.00 ± 0.19 mm2 at baseline to 0.63 ± 0.21 mm2 at the final session (P < 0.0001). Retinal nerve fiber layer area in control eyes was 0.95 ± 0.09 mm2 at baseline and 0.95 ± 0.10 mm2 at the final session (P = 0.96). Retinal nerve fiber layer area decreased in EG eyes from 0.95 ± 0.09 mm2 at baseline to 0.74 ± 0.19 mm2 at the final session (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.