Risk factor analysis of zonular instability in cataract patients with shallow anterior chambers

Objective  To investigate the occurrence and risk factors of zonular instability in cataract patients with shallow anterior chamber (SAC).

Methods  A case-control study was conducted. A total of 253 eyes of 253 consecutive patients with SAC and age-related cataract who underwent phacoemulsification with intraocular lens implantation were included at Nanning Aier Eye Hospital from January 2021 to January 2023. Based on the presence of intraoperative signs such as anterior capsule wrinkling or capsular bag movement during continuous curvilinear capsulorhexis, patients were divided into a zonular instability group (39 cases, 39 eyes) and a normal zonule group (214 cases, 214 eyes). The proportion of zonular instability, anterior chamber depth (ACD), lens vault (LV) and lens thickness (LT) were recorded. Multivariate logistic regression analysis was used to screen independent risk factors associated with zonular instability and construct a risk prediction model. This study adhered to the Declaration of Helsinki. The study protocol was approved by the Ethics Committee of Nanning Aier Eye Hospital (No. IRB005). Written informed consent was obtained from each subject.

Results  The proportion of intraoperative lens zonular instability was 15.41%(39/253). The ACD, LV, and LT were 2.33 (2.19, 2.42)mm, (0.63±0.23)mm, and 4.73 (4.50, 5.03)mm in the normal group, and 2.13 (1.92, 2.22)mm, (0.92±0.26)mm, and 5.15 (4.72, 5.42)mm in the zonular instability group, respectively. The ACD was greater, and LV and LT were smaller in the normal zonule group than in the zonular instability group, with statistically significant differences ( Z=-5.680, t=7.030, Z=-4.090, all P<0.001). Multivariate binary logistic regression showed that ACD was a protective factor against zonular instability ( OR=0.05, 95% CI: 0-0.47, P=0.008), while LV was an independent risk factor ( OR=45.76, 95% CI: 6.83-306.44, P<0.001), and the regression equation was Y=-0.07-2.98×ACD+ 3.82×LV ( R ²=0.195, χ ²=54.900, P<0.001). A risk prediction model for zonular instability was constructed: probability P for zonular instability=1/(1+ e ^-Y), and e was the natural logarithm base. ROC curve analysis identified that LV had the greatest diagnostic value for zonular instability, with a cutoff value of 0.81 mm.

Conclusions  LV is an independent factor for zonular instability in patients with SAC and cataract. Preoperative LV>0.81 mm may indicate a higher likelihood of zonular instability.