Influence of anterior chamber depth and vault on anterior chamber angle morphology after phakic posterior chamber intraocular lens implantation.

PURPOSE: This study aims to investigate the influence of anterior chamber depth (ACD) and vault on the anterior chamber angle (ACA) morphology in myopic individuals implanted with posterior chamber phakic intraocular lenses. METHODS: This retrospective case series involved 231 eyes receiving a 13.2-mm implantable collamer lens (ICL). Preoperative anterior chamber anatomy was assessed using anterior segment optical coherence tomography (AS-OCT) and optical tomography, while postoperative evaluation employed AS-OCT. ACA morphology was characterized pre- and postoperatively through trabecular iris angle (TIA750), ACA distance opening (AOD750) and trabecular iris space area (TISA750). The influence of ACD and vault was examined by categorizing the sample into ACD (shallow, average and deep) and vault (low, optimal and high) groups. RESULTS: Preoperative ACA morphology varied based on ACD, with shallower ACDs exhibiting narrower TIA750, smaller AOD750 and TISA750. ICL implantation induced greater ACA narrowing more in the deep ACD group (TIA750 = 20.1 degrees; AOD750 = 0.82 mm and TISA750 = 0.44 mm2) compared to the shallow ACD group (TIA750 = 15.2 degrees; AOD750 = 0.44 mm and TISA750 = 0.21 mm2). Postoperatively, deeper ACDs showed larger ACAs. Increasing vault magnitude led to increased ACA narrowing, with the low vault group exhibiting smaller closure (TIA750 = 14.3 degrees; AOD750 = 0.56 mm and TISA750 = 0.29 mm2) compared to the high vault group (TIA750 = 20.8 degrees; AOD750 = 0.73 mm and TISA750 = 0.36 mm2). The magnitude of ACA narrowing associated with the vault had a consistent effect across different ACD groups. CONCLUSIONS: Posterior chamber intraocular lens implantation results in ACA narrowing, the extent of which is contingent upon preoperative anterior chamber and ACA morphology, with additional influence from vault magnitude.

Prediction model of the horizontal trabecular iris angle after phakic posterior chamber implantable intraocular lens surgery.

PURPOSE: To determine the predictors of the postoperative horizontal trabecular iris angle (TIA 750 ) after phakic posterior chamber implantable intraocular lens (IOL) surgery. SETTING: Ophthalmology Clinic Vista Sánchez Trancón, Badajoz, Spain. DESIGN: Retrospective case series. METHODS: 330 eyes implanted with spherical/toric implantable collamer lens (ICL) were included in this study. From 230 eyes implanted with 13.2 mm ICL, these were divided in modeling (n = 180) and evaluation group (n = 50). Two groups implanted with 12.6 mm and 13.7 mm (n = 50 each) were also used as evaluation. Anterior-segment optical coherence tomography was used preoperatively to perform anterior chamber biometry (angle-to-angle [ATA] distance, crystalline lens rise, anterior chamber depth [ACD], cornea sagittal depth, pupil diameter, nasal/temporal TIA 750 ); postoperatively for measuring the vault, pupil diameter and nasal/temporal TIA 750 . Corneal curvature and horizontal visible iris diameter were measured using optical tomography. Bivariate correlation analysis was used to determine associations between preoperative and postoperative horizontal TIA 750 with anterior chamber biometry, ICL-related parameters and age. Finally, a multivariate linear regression model was constructed for predicting the postoperative TIA 750 . RESULTS: Horizontal TIA 750 reduced from 42.9 ± 8.0 degrees preoperatively to 24.4 ± 5.6 degrees postoperatively. Postoperative TIA 750 was positively correlated with the preoperative TIA 750 , cornea sagittal depth and ACD, and negatively associated with the vault. The main predictors of the postoperative TIA 750 were the preoperative parameters, TIA 750 , ICLsize - ATA and pupil diameter (adjusted- R2 = 0.39). The limits of agreement between predicted and real TIA 750 were close to ±10 degrees. CONCLUSIONS: Implantation of a phakic posterior chamber implantable IOL leads to a reduction in TIA 750 and the main factors contributing for this are the preoperative TIA 750 aperture and the vault.

Determining vault size in implantable collamer lenses: preoperative anatomy and lens parameters.

PURPOSE: To determine patient preoperative anatomical features and the parameters of implantable collamer lenses (ICLs) relevant in explaining vault variability. SETTING: Ophthalmology Clinic Vista Sánchez Trancón, Badajoz, Spain. DESIGN: Retrospective case series. METHODS: This study comprised 360 eyes of 360 patients implanted with myopic or toric ICLs. Pentacam imaging was used for assessing white-to-white (WTW) diameter, central keratometry, and central corneal thickness. Anterior-segment optical coherence tomography was used to measure the horizontal anterior chamber angle distance (ATA), internal anterior chamber (ACQ), crystalline lens rise (CLR), anterior chamber angle (ACA), and vault. The sample was divided according to the implanted lens size (12.6 mm, 13.2 mm, and 13.7 mm). Vault predictors were identified from the variables above using multivariate regression analysis. RESULTS: The groups showed significant statistical differences for WTW, ATA, ACQ, ACA, and vault (P < .007 for all). In general, bigger lenses were implanted in eyes with larger transverse sizes (WTW and ATA) and deeper ACQ. Also, larger ICL diameters were associated with higher vaults. Multivariate regression analysis identified the lens size (13.2 mm as reference; 12.6 mm: ß [standardized coefficients] = -0.33; 13.7 mm: ß = 0.42), ATA (ß = -0.42), and CLR (ß = -0.25), ICL spherical equivalent (ß = -0.22) and patient age (ß = -0.12) as predictors of the vault size (adjusted-R = 0.34 P < .001). CONCLUSIONS: The multivariate model explained 34% of vault variability. The predictors indicated the presence of different mechanisms regulating the vault. These involved the difference between the transverse size of the eye and the ICL, the crystalline lens protrusion, and the ICL properties, such as power and size.