Focal Laminar Defects are Spatially Correlated with Glaucomatous Optic Nerve Structural and Functional Damage

Abstract

 

Purpose:

 

To investigate the spatial relationships of focal lamina cribrosa (LC) defects with glaucomatous structural (neuroretinal rim [NRR], retinal nerve fiber layer [RNFL], disc hemorrhage [DH]) and functional damage.

 

Methods:

 

Serial horizontal and vertical enhanced depth imaging optical coherence tomography (EDI OCT) optic disc scans (interval between scans ~30 μm) were prospectively obtained for glaucomatous eyes. Focal LC defects were defined as localized LC disinsertions or full-thickness LC defects that violated the smooth curvilinear contour of the normal anterior laminar surface. The maximum width of each focal LC defect was required to be ≥100 µm. For eyes with focal LC defects, the anterior laminar surface and the LC defects were outlined using 3-dimensional reconstruction software (Fig. A-C). The locations of largest focal LC defect, greatest NRR loss, greatest FDOCT RNFL defect, deepest 24-2 visual field (VF) scotoma (based on pattern deviation map values), and ever-detected DH were determined using Garway-Heath mapping (Fig. D).

 

Results:

 

50 eyes (44 subjects) were included (mean age, 67±16 yr). In 49 eyes, the largest focal LC defects were detected in the temporal half of the LC (sectors 1 [10 eyes], 2 [31 eyes], 5 [1 eyes] and 6 [7 eyes]). The largest LC defects occurred in the same sector as the greatest NRR and RNFL defects in 47 eyes (all P<0.001, Cramer’s correlation coefficient V=0.955). The largest LC defects spatially corresponded to the densest scotoma in 44 eyes (P<0.001, V=0.807) (Fig. E and F). In 5/6 eyes with spatial discrepancy between focal LC defects and NRR, RNFL or VF defects, the largest focal LC defects occurred adjacent to the sectors of the greatest NRR, RNFL and VF defects. DH was detected in 9 eyes and occurred at the margin of the largest (or second largest) focal LC defect in 8 eyes (P<0.001, V=0.913).

 

Conclusions:

 

Focal LC defects showed an excellent spatial correlation with glaucomatous structural changes (NRR loss, RNFL defect and DH) and functional damage. The precise relationship between focal LC damage and the development of DH warrants further investigation.  

 

Keywords: lamina cribrosa • optic disc • visual fields