Remodeling of the connective tissue microarchitecture of the lamina cribrosa in early experimental glaucoma.
OBJECTIVE
To characterize the trabeculated connective tissue microarchitecture of the lamina cribrosa (LC) in terms of total connective tissue volume (CTV), connective tissue volume fraction (CTVF), predominant beam orientation, and material anisotropy in monkeys with early experimental glaucoma (EG).


METHODS
The optic nerve heads from three monkeys with unilateral EG and four bilaterally normal monkeys were three dimensionally reconstructed from tissues perfusion fixed at an intraocular pressure of 10 mm Hg. A three-dimensional segmentation algorithm was used to extract a binary, voxel-based representation of the porous LC connective tissue microstructure that was regionalized into 45 subvolumes, and the following quantities were calculated: total CTV within the LC, mean and regional CTVF, regional predominant beam orientation, and mean and regional material anisotropy.


RESULTS
Regional variation within the laminar microstructure was considerable within the normal eyes of all monkeys. The laminar connective tissue was generally most dense in the central and superior regions for the paired normal eyes, and laminar beams were radially oriented at the periphery for all eyes considered. CTV increased substantially in EG eyes compared with contralateral normal eyes (82%, 44%, 45% increases; P<0.05), but average CTVF changed little (-7%, 1%, and -2% in the EG eyes). There were more laminar beams through the thickness of the LC in the EG eyes than in the normal controls (46%, 18%, 17% increases).


CONCLUSIONS
The substantial increase in laminar CTV with little change in CTVF suggests that significant alterations in connective and nonconnective tissue components in the laminar region occur in the early stages of glaucomatous damage.
Roberts
Michael D
MD
Ocular Biomechanics Laboratory, Devers Eye Institute, Legacy Health System, Portland, Oregon 97232, USA.
Grau
Vicente
V
Grimm
Jonathan
J
Reynaud
Juan
J
Bellezza
Anthony J
AJ
Burgoyne
Claude F
CF
Downs
J Crawford
JC
D000818:Animals; D003238:Connective Tissue / Q000473:pathology*; D004195:Disease Models, Animal; D005260:Female; D005901:Glaucoma / Q000473:pathology*; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D007429:Intraocular Pressure; D017075:Laser Coagulation; D008252:Macaca fascicularis; D008253:Macaca mulatta; D008297:Male; D009898:Optic Disk / Q000473:pathology*; D009901:Optic Nerve Diseases / Q000473:pathology*; D012590:Sclera / Q000473:pathology*; D014129:Trabecular Meshwork / Q000601:surgery