Observation on the structural characteristics of optic discs in high myopia combined with primary open-angle glaucoma / 中华眼底病杂志

ABSTRACT

Objective:To observe and analyze the structural characteristics of the optic discs in high myopia (HM) combined with primary open-angle glaucoma (POAG) and the optic disc parameters with diagnostic efficacy.Methods:A cross-sectional study. From August 2020 to March 2021, a total of 114 eyes of 68 patients with POAG, HM and healthy volunteers who were diagnosed by Department of Ophthalmology, The First Affiliated Hospital of Kunming Medical University were included in the study. Among them, 21 POAG patients (39 eyes) were divided into H+P group (9 patients, 18 eyes) and non-H+P group (12 patients, 21 eyes) according to whether or not HM was combined; 26 HM patients (37 eyes) were selected as HM group; 21 healthy volunteers (38 eyes) were selected as normal control group. The subjects included 31 males (51 eyes) and 37 females (63 eyes), whose average age was 36.93±12.60 years old. Diopter, central corneal thickness (CCT) and axial length (AL) were measured. There was no significant difference in age ( F=8.333), sex composition ratio ( χ2=0.863), and CCT ( F=1.425) among the four groups ( P>0.05); while, there were significant differences in AL ( F=69.956), diopter ( F=37.711), visual field index (VFI) ( F=43.254) and mean defect (MD) ( F=49.793) among the four groups ( P<0.01). Enhanced depth imaging using optical coherence tomography was used to obtain the tilt parameters, the disc rim parameters, the lamina cribrosa parameters and the retinal nerve fiber layer (RNFL) thickness. The tilt parameters included optic disc horizontal diameter, optic disc vertical diameter, optic disc ellipse index (horizontal diameter/vertical diameter); the disc rim parameters included Bruch’s membrane opening-minimal rim width (BMO), optic cup area, optic disc area, disc rim area, cup-disc area ratio; the lamina cribrosa parameters included anterior laminar insertion depth (ALID), prelaminar neural tissue (PLNT), and lamina cribrosa thickness. The pairwise comparison between groups were performed by ANOVA test. Pearson correlation analysis was used to analyze the correlation between disc tilt parameters, disc rim parameters, lamina cribrosa parameters and visual field parameters, as well as between disc rim parameters and RNFL thickness. According to receiver operating characteristic (ROC) curve and area under the curve (AUC), the predictive value of those above related factors for HM combined with POAG was evaluated. Results:Tilt parameters: compared with the optic disc horizontal diameter of non-H+P group, those of normal control group, HM group and H+P group were significantly decreased ( P<0.05), the ellipse indices of HM group and H+P group were significantly lower than those of normal control group and non-H+P group ( P<0.05). The results of correlation analysis showed that the optic disc horizontal and vertical diameters were negatively correlated with MD ( r=-0.302,-0.235; P=0.002, 0.017), and negatively correlated with VFI ( r=-0.291,-0.246; P=0.003, 0.013). Disc rim parameters: the disc cup area and cup-disc area ratio of non-H+P group and H+P group were significantly larger than those of normal control group and HM group ( P<0.05). The disc rim area and the average BMO of HM group, non-H+P group and H+P group were significantly smaller than those of normal control group ( P<0.05). The results of correlation analysis showed that the cup-disc area ratio ( r=-0.584), the average BMO ( r=0.650) had the highest correlation with the average RNFL thickness ( P<0.001). The superior, inferior, nasal and temporal BMO were all positively correlated with the corresponding quadrant RNFL thicknesses ( r=0.431, 0.656, 0.362, 0.375; P<0.05); the optic disc rim area, the average BMO were positively correlated with MD ( r=0.449, 0.618) and VFI ( r=0.449, 0.605) ( P<0.05), among which the correlation of the average BMO was the highest; the optic cup area and cup-disc area ratio were negatively correlated with MD ( r=-0.346,-0.559) and VFI ( r=-0.312,-0.548) ( P<0.001), among which the correlation of the cup-disc area ratio was the highest. Lamina cribrosa parameters: ALID of non-H+P group and H+P group were significantly deeper than those of normal control group and HM group ( P<0.05). LC of non-H+P group and H+P group were significantly thinner than those of normal control group and HM group ( P<0.05). The results of correlation analysis showed that ALID was negatively correlated with MD and VFI ( r=-0.402, P<0.001), VFI ( r=-0.405, P=0.001); LC was positively correlated with MD and VFI ( r=0.403, P<0.001), VFI ( r=-0.401, P=0.015). Comparison of diagnostic efficiency between various optic disc parameters: the results of ROC analysis showed that the cup-disc area ratio had the highest diagnostic performance (AUC=0.847, P=0.007), the maximum Youden index was 0.563, the sensitivity and specificity were 0.833 and 0.730, respectively, and the best critical value was 0.340. Conclusions:Optic disc tilt is more pronounced in HM combined with POAG; BMO in each quadrant could objectively reflect the disc rim defect of HM combined with POAG; the thinning and the backward shift of the lamina cribrosa were consistent with the aggravation of the visual field defect. Among them, the cup-disc area ratio had better diagnostic performance.