Biometric indicators of anterior segment parameters before and after laser peripheral iridotomy by swept-source optical coherent tomography

Changes in IOL power after laser peripheral iridotomy based on multivariate analysis

BACKGROUND

This study aimed to investigate the effect of laser peripheral iridotomy (LPI) on intraocular lens (IOL) power in patients with primary angle closure disease (PACD), and to construct mathematical models to assess changes in IOL power.

METHODS

This study included 58 eyes of PACD patients. IOL Master700 was used to analyze and compare the changes of IOL power and ocular related parameters in each formula before and after LPI. The number of cases with IOL power changes greater than 0.5 diopters (D) in each group were counted and significant differences were analyzed using Fisher's exact test. Pearson's linear correlation analysis was used to ascertain the relationship between IOL power changes and ocular parameter changes to establish mathematical models.

RESULTS

No significant difference was found in calculated IOL power changes before and after LPI in each group. There was significant difference in the number of cases with IOL change values greater than 0.5D between the primary angle closure glaucoma (PACG) and the other two groups for each formula. IOL power changes were mainly associated with △K and △AL. Mathematical models of IOL power changes after LPI were constructed based on linear regression analysis.(PAC group: △IOLHaigis=0.026-2.950×△AL-1.414×△K, △IOLHoffer Q=-3.578×△AL-1.412×△K, △IOLSRK/T=-3.152×△AL-1.114×△K, △IOLHolladay 1=-3.405×△AL-1.291×△K, △IOLHolladay 2=-3.467×△AL-1.483×△K, △IOLBUII=-3.185×△AL-1.301×△K; PACG group:△IOLHaigis=-1.632×△K, △IOLHoffer Q=-3.770×△AL-1.434×△K, △IOLSRK/T=-3.427×△AL-1.102×△K, △IOLHolladay 1=-3.625×△AL-1.278×△K, △IOLHolladay 2=-4.764×△AL-1.272×△K, △IOLBUII=-4.935×△AL-1.304×△K).

CONCLUSIONS

LPI will cause changes in some ocular parameters in patients with PACD, with great effects on IOL power calculations was observed in patients with PACG. Mathematical models based on multivariate analysis hold promise for predicting IOL power changes subsequent to LPI.

Analysis of Indicators for Assessing the Risk of Progression from PACS to APAC and the Degree of Intraocular Pressure Elevation in APAC Using AS-OCT

Objective

The aim of this study is to quantify anterior chamber parameters to provide potential risk indicators for evaluating the progression of primary angle-closure suspect (PACS) eyes to acute primary angle closure (APAC) and the degree of intraocular pressure elevation in patients with APAC utilizing anterior segment optical coherence tomography (AS-OCT).

Methods

Tomey CASIA2 AS-OCT was used to quantitatively measure various anterior chamber parameters, including anterior chamber depth (ACD), anterior chamber volume (ACV), lens thickness (LT), lens vault (LV), iris-trabecular contact index (ITC), iris thickness (IT), iris volume (IV), iris curvature (IC), iris area (IA), and iris thickness (IT), in APAC eyes (30 eyes) and contralateral PACS eyes (30 eyes) of 30 patients. The differences in these parameters between the two groups and their relationship with intraocular pressure were analyzed.

Results

Compared to the PACS group, the APAC group exhibited significantly smaller IA and IC, and significantly larger pupil diameter (PD) and ITC (P < 0.05). There were no statistically significant differences in ACV, ACD, ACW, ACA, LV, IV, and IT750/2000 between the two groups. In APAC eyes, multivariable linear regression analysis showed a significant negative correlation between intraocular pressure and IV (β = -1.85; 95% confidence interval: -2.77 to -0.93; P=0.001), while no correlation was found in PACS eyes. In all 60 eyes, LT showed a negative correlation with ACV, ACD, ACA, and nasal IT750, and a positive correlation with LV and nasal IC.

Conclusion

AS-OCT has multiple advantages in evaluating various anterior chamber parameters in patients with glaucoma. IA may serve as a predictive indicator of the progression of eyes from PAC or APAC. A significant negative correlation was found between intraocular pressure and IV during APAC attacks. LT can be considered a predictive factor for the occurrence of primary angle-closure disease.

Clinical applications of anterior segment swept-source optical coherence tomography: A systematic review

Optical coherence tomography (OCT) is a non-invasive method that provides the opportunity to examine tissues by taking cross-sectional images. OCT is increasingly being used to evaluate anterior segment (AS) pathologies. Swept-source (SS) OCT allows greater penetration and achieves better visualization of the internal configuration of AS tissues due to the longer wavelength employed and high scan speeds. We reviewed the utilization of AS SS-OCT in various conditions including glaucoma, ocular surface pathologies, iris tumors, refractive surgery, cataract surgery, and scleral diseases. A systematic literature search was carried out on PubMed, Scopus, and Web of Science databases between January 1, 2008, and September 1, 2022 using the following keywords: AS SS-OCT; dry eye and SS-OCT; ocular surface and SS-OCT; cornea and SS-OCT; dystrophy and SS-OCT; glaucoma and SS-OCT; ocular surface tumors and SS-OCT; conjunctival tumors and SS-OCT; refractive surgery and SS-OCT; cataract and SS-OCT; biometry and SS-OCT; sclera and SS-OCT; iris and SS-OCT; ciliary body and SS-OCT; artificial intelligence and SS-OCT. A total of 221 studies were included in this review. Review of the existing literature shows that SS-OCT offers several advantages in the diagnosis of AS diseases. Exclusive features of SS-OCT including rapid scanning, deeper tissue penetration, and better image quality help improve our understanding of various AS pathologies.

Large Amplitude Iris Fluttering Detected by Consecutive Anterior Segment Optical Coherence Tomography Images in Eyes with Intrascleral Fixation of an Intraocular Lens

Saccadic eye movements induce movements of the aqueous and vitreous humor and iris fluttering. To evaluate iris fluttering during eye movements, anterior segment optical coherence tomography (AS-OCT) was used in 29 eyes with pars plana vitrectomy (PPV) and intrascleral fixation of an intraocular lens (ISF group) and 15 eyes with PPV and an IOL implantation into lens capsular bag (control group). The height of the iris from the iris plane (the line between the anterior chamber angles) was compared every 0.2 s after the eye had moved from a temporal to the primary position (time 0). The height of the nasal iris in the ISF group decreased to −0.68 ± 0.43 mm at 0 s (p < 0.001) and returned to −0.06 ± 0.23 mm at 0.2 s. The height of the temporal iris increased to 0.45 ± 0.31 mm at 0 s (p < 0.001) and returned to −0.06 ± 0.18 mm at 0.2 s. The height of the nasal iris at 0 s in the ISF group was significantly lower, and that of the temporal iris was significantly higher than the control (−0.05 ± 0.09 mm, 0.03 ± 0.06 mm, p < 0.001, respectively). Iris fluttering can act as a check valve for aqueous and vitreous humor movements and can be quantified by consecutive AS-OCT images. Large amplitude iris fluttering in eyes with intrascleral fixation is important because it can lead to a reverse pupillary block.