Analysis of morphologic changes of lamina cribrosa in primary open angle glaucoma using enhanced depth imaging optical coherence tomography

Abstract

To analyze the morphologic changes of the lamina cribrosa (LC) in primary open angle glaucoma (POAG) patients using enhanced depth imaging optical coherence tomography (EDI-OCT). This was a case-control study. Serial horizontal and vertical B-scans of the optic nerve head were obtained from one eye of 52 POAG patients and 50 age- and sex-matched healthy subjects by EDI-OCT. The number and location of focal LC defects as well as their relationship with retinal nerve fiber layer(RNFL) defects were investigated in glaucomatous eyes and compared with healthy controls. The LC thickness was measured at the center of mid-superior, central, and mid-inferior horizontal B-scans. The intra- and interobserver reproducibility were evaluated by intraclass correlation coefficient (ICC). A repeated measure ANOVA was used to analyze regional differences of the LC thickness. Independent t-test was conducted to compare LC thickness between POAG and healthy controls. A Pearson correlation was calculated for variation in LC thickness relative to global mean RNFL thickness. Spearman rank correlation was calculated to test the strength of the relationship between LC thickness and visual field mean deviation (MD). Twenty-six focal LC defects were found in 20 eyes (38.5%) with glaucoma versus none in the healthy controls. There were 13 (50.0%) focal LC defects in the inferotemporal sector, 6 (23.1%) defects in the inferior sector, 4 (15.4%) in the superotemporal sector, and 3 (11.5%) in the superior sector. Twenty-five of 26 focal LC defects (96.2%) corresponded to the RNFL defects. The intra- and interobserver ICCs of LC thickness measurement ranged from 0.90 to 0.95 and 0.84 to 0.90, respectively. The thicknesses of the superior midperipheral, central, and inferior midperipheral LC in POAG eyes were 180.7±26.3, 196.7±24.0, and 184.1±23.5 μm, respectively. In healthy controls, the laminar thicknesses were 203.2±21.0, 225.2±22.7, and 202.6±16.5 μm, respectively. In both groups, the midperipheral LC was significantly thinner than the central LC (P<0.01). The mean LC thickness was (187.2±19.4) μm in POAG eyes. It was significantly thinner than that in healthy controls (210.3±17.4 μm) (t=5.06, P<0.01). The superior midperipheral, central, and inferior midperipheral regions of the LC were also significantly thinner in POAG than in controls (t=3.52 to 4.96, P<0.01). In POAG patients, mean LC thickness was found to significantly correlate with both global mean RNFL thickness (r=0.45, P<0.01) and visual field MD (rs=-0.58, P<0.01). The LC thickness was thinner in POAG than in healthy eyes, and correlated with the severity of POAG. Focal LC defects occurred frequently in POAG eyes, and might be associated with RNFL defect. EDI-OCT is a useful tool for the evaluation of LC deformation in glaucoma.(Chin J Ophthalmol, 2016, 52: 422-428).