Comparing Optic Nerve Head Rim Width, Rim Area, and Peripapillary Retinal Nerve Fiber Layer Thickness to Axon Count in Experimental Glaucoma.
Fortune Brad, Hardin Christy, Reynaud Juan, Cull Grant, Yang Hongli, Wang Lin, Burgoyne Claude F
AI Summary
This study found peripapillary RNFLT correlates best with actual axon loss in experimental glaucoma, suggesting it's a more reliable SDOCT measure than optic nerve head rim parameters for monitoring disease.
Abstract
Purpose
We compare spectral-domain optical coherence tomography (SDOCT) measurements of minimum rim width (MRW), minimum rim area (MRA), and peripapillary retinal nerve fiber layer thickness (RNFLT) to complete orbital optic nerve axon counts in nonhuman primates (NHP) with unilateral experimental glaucoma (EG).
Methods
Biweekly SDOCT measurements of MRW, MRA, and RNFLT were acquired under manometric IOP control (10 mm Hg) in 51 NHP during baseline (mean ± SD, 5.0 ± 1.6 sessions) and after laser photocoagulation was applied to the trabecular meshwork of one eye to induce chronic IOP elevation. At the study endpoint (predefined for each NHP), 100% axon counts were obtained from each optic nerve.
Results
For SDOCT parameters at baseline, the correlation between the two eyes of each animal was strongest for RNFLT (R = 0.97) and MRW (R = 0.97), but lower for MRA (R = 0.85). At the final time point, average values in EG eyes relative to control eyes were: -22% for RNFLT, -38% for MRW, -36% for MRA, and -36% for optic nerve axons. The correlation with axon counts was strongest for RNFLT (R = 0.81), compared to MRW (R = 0.72, P = 0.001) or MRA (R = 0.70, P = 0.001). Diagnostic sensitivity was 75% for RNFLT, 90% for MRW, and 88% for MRA; all had 100% specificity.
Conclusions
Peripapillary RNFLT was correlated more closely with total orbital optic nerve axon count than were the ONH parameters MRW or MRA. This is likely because glaucomatous deformation (beyond axon loss alone) has a greater influence on the ONH parameters MRW and MRA than on RNFLT.
MeSH Terms
Shields Classification
Key Concepts6
In 51 nonhuman primates (NHP) with unilateral experimental glaucoma (EG), at the final time point, average values in EG eyes relative to control eyes were: -22% for peripapillary retinal nerve fiber layer thickness (RNFLT), -38% for minimum rim width (MRW), -36% for minimum rim area (MRA), and -36% for optic nerve axons.
In 51 nonhuman primates (NHP) with unilateral experimental glaucoma (EG), the correlation with optic nerve axon counts was strongest for peripapillary retinal nerve fiber layer thickness (RNFLT) (R = 0.81), compared to minimum rim width (MRW) (R = 0.72, P = 0.001) or minimum rim area (MRA) (R = 0.70, P = 0.001).
In 51 nonhuman primates (NHP) with unilateral experimental glaucoma (EG), diagnostic sensitivity was 75% for peripapillary retinal nerve fiber layer thickness (RNFLT), 90% for minimum rim width (MRW), and 88% for minimum rim area (MRA); all had 100% specificity.
In 51 nonhuman primates (NHP) with unilateral experimental glaucoma (EG), peripapillary retinal nerve fiber layer thickness (RNFLT) was correlated more closely with total orbital optic nerve axon count than were the optic nerve head (ONH) parameters minimum rim width (MRW) or minimum rim area (MRA).
In 51 nonhuman primates (NHP) with unilateral experimental glaucoma (EG), glaucomatous deformation (beyond axon loss alone) likely has a greater influence on the optic nerve head (ONH) parameters minimum rim width (MRW) and minimum rim area (MRA) than on peripapillary retinal nerve fiber layer thickness (RNFLT).
In a study of 51 nonhuman primates (NHP) with unilateral experimental glaucoma (EG), the correlation between the two eyes at baseline was strongest for peripapillary retinal nerve fiber layer thickness (RNFLT) (R = 0.97) and minimum rim width (MRW) (R = 0.97), but lower for minimum rim area (MRA) (R = 0.85).
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