Analysis Of Iris And Ciliary Body Morphology On The Central Vault Of Posterior Chamber Phakic Intraocular Lens

Purpose:To investigate the impact of iris and ciliary body morphology on the central vault at different times after posterior chamber phakic intraocular lens(ICL)implantation;Methods:1.The first part of the study was based on the retrospective analysis of 123 patients(123eyes)who underwent posterior chamber phakic ICL(V4c)implantation in the Department of Ophthalmology,Affiliated Hospital of Qingdao University between June 2018 and June2020.The anterior segment structure was observed with the ultrasound biomicroscopy(UBM)before surgery,and all morphological parameters of iris and ciliary body were measured manually using Image J software.The parameters include iris thickness(IT500、ITC)、iris span(IS)、iris convexity(IC)、ciliary body thickness(CBT1、CBT2)、ciliary body area(CBA1、CBA1-2、CBA2)、ciliary sulcus width(SW)、iris-ciliary body contacted distance(ICCD)、iris-ciliary processes angle(ICA)、iris-lens contacted distance(ILCD)and iris-lens angle(ILA);And the ICCD was divided into three groups on average: Q1: 0≤ICCD<0.36mm;Q2: 0.36mm≤ICCD<0.72mm;Q3: ICCD>0.72 mm.The lens thickness(LT)was measured with IOLMaster;The central vaults were measured using Optical Coherence Tomography(AS-OCT)at 1 week、3 months and 1 year after surgery.Pearson correlation analysis,Spearman correlation analysis,multiple linear regression and repeated measures ANOVA was applied for statistical analysis.2.Forty-one myopic patients(80 eyes)who underwent V4 c ICL implantation from December 2020 to July 2021 in the Department of Ophthalmology,Affiliated Hospital of Qingdao University were chosen for the second part of our study.The changes of UCVA,SE,ECD,intraocular pressure and vault were observed and recorded before ICL implantation,1week and 1 month after ICL implantation.HD-OCT,Pentacam anterior segment analysis and UBM examination were performed to observe the changes of the central vaults,anterior chamber,pupil diameter and lens haptics positions before and after mydriasis at 1 month after surgery.The changes of parameters were compared by repeated measures ANOVA,Bonferroni test or paired t-test;Pearson correlation analysis and Spearman correlation analysis were used to observe the correlation between vault variation and various parameters.Results:1.The mean value of the vault at 1 week,3 months and 1 year after surgery were(723.29±265.41)μm,(641.65±255.01)μm and(613.28±280.34)μm,respectively(F=50.143,P<0.001).The vault continued to decline within 1 year after ICL implantation,and vault declined more rapidly in the first 3 months after surgery.2.ICL size,ILCD were positive related with the vault at 1 week postoperatively;LT,IS,IC were negative related with the vault at 1 week postoperatively(adjusted R~2=0.404,P<0.001);ICL size,ILCD were positive related with the vault at 3 months postoperatively,IS and IC were negative related with the vault at 3 months postoperatively(adjusted R~2=0.342,P<0.001);ICL size was positive related with vault at 1 year postoperatively,and IS,IC were negative related with vault at 1 year postoperatively(adjusted R~2=0.661,P<0.001).The vault values were higher in group Q3 compared to group Q1,and the vault value was higher in group Q2 compared to Q1 at 1 year postoperatively.3.UCVA and SE were improved significantly after ICL surgery(P<0.001).The effective index of ICL were 1.15 ± 0.20 at 1 week and 1 month after ICL implantation.ACD,ACV and ACA decreased significantly after ICL implantation(P <0.001).Intraocular pressure(IOP)increased at 1 week postoperatively,but decreased to preoperative level at 1 month(P<0.001).ECD remained stable before and after surgery.4.Before and after mydriasis,the mean values of vault measured by UBM and Pentacam were not statistically significant(P>0.05).18 eyes(23.38%)showed no significant change in vault after mydriasis;27 eyes(35.06%)showed a significant decreased in vault after mydriasis,and 32 eyes(41.56%)showed an increased in vault after mydriasis.The ACD,ACV and ACA were significantly increased after mydriasis(P<0.001).5.Before mydriasis,5.15% of the lens haptics were placed in the ciliary sulcus,54.41%of the lens haptics were placed on the ciliary body,and 40.44% of the lens haptics were placed on the ciliary process.After mydriasis,5.15% of the lens haptics were placed in the ciliary sulcus,40.44% of the lens haptics were placed on the ciliary body,and 54.41% of the lens haptics were placed on the ciliary process.During the process of mydriasis,62.50% of the lens haptics remained stable,26.47% of the lens haptics moved down,and 11.03% of the lens haptics moved up.6.The amount of vault(post-mydriatic vault minus pre-mydriatic vault)was negatively correlated with pre-mydriatic vault,and positively correlated with anterior chamber volume,anterior chamber angle.Conclusion:The vault continued to decline within 1 year after ICL implantation,and vault declined more rapidly in the first 3 months after surgery.In early postoperative period,eyes with larger ICL size,shorter iris span,longer contact distance between iris and ciliary body,and longer contact distance between iris and lens were associated with a higher rate of excessive vault.Meanwhile,Eyes with thicker lens and larger iris reverse convexity were more likely to obtain insufficient vault.Within one year after surgery,ICL size,IS,IC and ICCD continued to affect the vault.Patients with higher vault had a greater decrease in vault after mydriasis,and patients with lower vault had a higher increase in vault after mydriasis.Most of the lens haptics of ICL are placed on the ciliary body and ciliary process,and only a few lens haptics are completely implanted in the ciliary sulcus.Most of the lens haptics in mydriasis were stable,and some of them moved down and moved up.