Clinical Analysis Of Anterior Segment Structure In First Degree Relatives Of Primary Angle Closure Glaucoma

Objective:To quantitatively detect and analyze the anterior segment structure of the first degree relatives of primary angle closure glaucoma（PACG）and normal people by ultrasound biomicroscopy（UBM）.Method:Retrospective study.From September 2020 to October 2022,48 eyes of 48first-degree relatives of PACG aged 40-60 years who visited the Affiliated Eye Hospital of Nanchang University were selected as the observation group,and 40 eyes of 40 healthy subjects of the same age group were collected as the control group.All subjects were divided into younger age group（40-49 years old）and older age group（50-60 years old）according to age,and anterior chamber depth（ACD）was grouped.All subjects underwent examinations such as best corrected visual acuity,slit lamp,non-contact intraocular pressure,fundus examination,ocular A-ultrasound and ultrasound biomicroscopy（UBM）.The UBM images were measured and analyzed using camera measure measurement software.The main measurement parameters include ACD,anterior chamber width（ACW）,anterior chamber area（ACA）,lens vault（LV）,relative position of lens vault（RPLV）,anterior segment depth（ASD）,angle opening distance(AOD₅₀₀),trabecular iris area(TISA₅₀₀),trabecular iris angle（TIA）,iris thickness(IT₅₀₀),iris curve（IC）,iris ciliary process distance（ICPD）,scleral ciliary process angle（SCPA）.SPSS26.0 statistical software was used for statistical analysis of the data.The differences in anterior segment structure and ACD distribution between PACG first-degree relatives and the control group were compared,and the influencing factors related to TISA₅₀₀in PACG first-degree relatives and their weights were analyzed.Independent sample t test and chi-square test were used for comparison between groups.Pearson correlation analysis was used for correlation analysis.P<0.05 was considered statistically significant.Result:1.ACD distribution:in the observation group,mild shallow anterior chamber was 33.33%,moderate shallow anterior chamber was 27.08%,severe shallow anterior chamber was 4.17%,and total shallow anterior chamber was 64.58%.In the control group,mild shallow anterior chamber was 25.00%,moderate shallow anterior chamber was 2.50%,no severe shallow anterior chamber,and total shallow anterior chamber was 27.50%.There was a statistically significant difference in the distribution of ACD between the observation group and the control group（P<0.05）,and the proportion of moderate to severe shallow anterior chamber in the observation group was 12.5 times that of the control group.2.Comparison of anterior segment parameters between groups:the average values of ACD,ACA,AOD₅₀₀,TISA₅₀₀and TIA in the observation group were smaller than those in the control group,and the average values of LV and IC were larger than those in the control group;the average values of ACD,ACA,AOD₅₀₀,TISA₅₀₀and TIA in the elderly observation group were smaller than those in the elderly control group,and the average values of LV and IC were larger than those in the elderly control group.The average values of ACD,AOD₅₀₀,TISA₅₀₀and TIA in the young observation group were smaller than those in the young control group,and the average values of LV and IC were larger than those in the young control group,the differences were statistically significant（P<0.05）.Comparison within the observation group:the average values of ACD,ACA,AOD₅₀₀,TISA₅₀₀and TIA in the elderly observation group were smaller than those in the young observation group,and the average values of LV and IC were larger than those in the young observation group,the differences were statistically significant（P<0.05）.3.The results of correlation analysis showed that TISA₅₀₀was positively correlated with ACD and ACA,and negatively correlated with LV,RPLV and IC.TISA₅₀₀was mainly affected by LV.RPLV was more correlated than LV.IC was positively correlated with LV and PRLV,and negatively correlated with ACD and ACA.Conclusion:1.The risk of angle closure in PACG first-degree relatives within the normal axial range was 12.5 times that of normal people.2.The anterior segment structure of PACG first-degree relatives is narrower than that of normal people,showing the anatomical characteristics of shallow anterior chamber,narrow angle,iris bulge and anterior lens position,especially in first-degree relatives over 50 years old.3.The change of trabecular iris area of PACG first-degree relatives is related to anterior chamber depth,anterior chamber area,lens arch height,relative position of lens arch height,iris curvature and other factors,among which lens anterior displacement may be the main influencing factor leading to angle stenosis.