Baseline Anterior Segment Parameters Associated with the Long-term Outcome of Laser Peripheral Iridotomy

Biometric Risk Factors for Angle Closure Progression After Laser Peripheral Iridotomy

Importance

Laser peripheral iridotomy (LPI) is the most common primary treatment for primary angle closure disease (PACD). However, there are sparse data guiding the longitudinal care of PAC suspect (PACS) eyes after LPI.

Objective

To elucidate the anatomic effects of LPI that are associated with a protective outcome against progression from PACS to PAC and acute angle closure (AAC) and to identify biometric factors that predict progression after LPI.

Design, Setting, and Participants

This was a retrospective analysis of data from the Zhongshan Angle Closure Prevention (ZAP) trial, a study of mainland Chinese people aged 50 to 70 years with bilateral PACS who received LPI in 1 randomly selected eye. Gonioscopy and anterior-segment optical coherence tomography (AS-OCT) imaging were performed 2 weeks after LPI. Progression was defined as the development of PAC or an acute angle closure (AAC) attack. Cohort A included a random mix of treated and untreated eyes, and cohort B included only eyes treated with LPI. Univariable and multivariable Cox regression models were developed to assess biometric risk factors for progression in cohorts A and B. Data were analyzed from January 4 to December 22, 2022.

Main Outcome and Measure

Six-year progression to PAC or AAC.

Results

Cohort A included 878 eyes from 878 participants (mean [SD] age, 58.9 [5.0] years; 726 female [82.7%]) of whom 44 experienced progressive disease. In a multivariable analysis, treatment (hazard ratio [HR], 0.67; 95% CI, 0.34-1.33; P = .25) was no longer associated with progression after adjusting for age and trabecular iris space area at 500 μm (TISA at 500 μm) at the 2-week visit. Cohort B included 869 treated eyes from 869 participants (mean [SD] age, 58.9 [5.0] years; 717 female [82.5%]) of whom 19 experienced progressive disease. In multivariable analysis, TISA at 500 μm (HR, 1.33 per 0.01 mm2 smaller; 95% CI, 1.12-1.56; P = .001) and cumulative gonioscopy score (HR, 1.25 per grade smaller; 95% CI, 1.03-1.52; P = .02) at the 2-week visit were associated with progression. Persistent angle narrowing on AS-OCT (TISA at 500 μm ≤0.05 mm2; HR, 9.41; 95% CI, 3.39-26.08; P <.001) or gonioscopy (cumulative score ≤6; HR, 2.80; 95% CI, 1.13-6.93; P =.04) conferred higher risk of progression.

Conclusions and Relevance

Study results suggest that persistent angle narrowing detected by AS-OCT or cumulative gonioscopy score was predictive of disease progression in PACS eyes after LPI. These findings suggest that AS-OCT and gonioscopy may be performed to identify patients at high risk of developing angle closure who may benefit from closer monitoring despite patent LPI.

Glaucoma Progression After Lens Extraction in Primary Angle-closure Glaucoma According to Angle-closure Mechanism

PRCIS

Long-term prognosis of primary angle-closure was assessed after lens extraction (LE) according to different mechanisms of angle closure (AC). Patients with pupillary block (PB) had a higher probability of glaucomatous progression than patients with plateau iris configuration (PIC).

PURPOSE

The aim was to investigate and compare the clinical characteristics and long-term prognosis of primary angle-closure disease (PACD) after LE according to different mechanisms of AC.

METHODS

In this retrospective observational cohort study, 118 eyes with PACD that underwent LE (mean follow-up; 6.0±3.5 y after surgery) were included. PACD eyes were categorized into three subgroups according to their dominant AC mechanisms, determined by anterior segment optic coherent tomography obtained before LE; PB, PIC, and exaggerated lens vault (ELV). Postoperative glaucomatous progression was determined according to functional (visual field) or structural (optic disc photographs or optic coherent tomography measured retinal nerve fiber layer thickness) criteria. Univariate and multivariate logistic regression analysis was performed to determine the risk factors associated with glaucomatous progression.

RESULTS

Fifty-two, 51, and 15 eyes with PB, PIC, and ELV, respectively, were included. All eyes showed significant intraocular pressure reduction, with a greater reduction in the ELV group than in the PB group after LE (27.0% vs. 12.5%, P=0.018). Lower baseline retinal nerve fiber layer thickness [odds ratio (OR): 0.966, P=0.004] and thinner central corneal thickness (OR: 0.985, P=0.021), and the PB group (OR: 2.891, P=0.022, reference to PIC group) were significantly associated with glaucomatous progression after LE.

CONCLUSIONS

In eyes with PACD, glaucoma progression was observed following LE despite reduced intraocular pressure. The probability of progression was highest in eyes with pupil block as a mechanism of AC. Close monitoring of glaucoma in these patients is suggested.

Circumferential Assessment of Changes in Anterior Segment Characteristics and Baseline Predictors of Angle Widening After Laser Iridotomy in Caucasian Eyes

PRCIS

Laser peripheral iridotomy (LPI) widened the iridocorneal angle and flattened the iris circumferentially in Caucasian eyes and baseline refractive error, lens vault, and iris volume play a significant role in the angle widening.

PURPOSE

The purpose of this study was to investigate circumferential angle widening and iris changes after LPI using swept-source optical coherence tomography (SS-OCT) in Caucasian eyes with the use of novel anterior segment parameters.

MATERIALS AND METHODS

A total of 130 eyes (68 primary angle-closure suspect, 34 primary angle closure, and 28 primary angle-closure glaucoma eyes) of 66 subjects underwent 360-degree SS-OCT (SS-1000 CASIA) angle imaging and gonioscopy in the dark before and 7, 30, 90 days after LPI. For each eye, 16 frames (11.25 degree apart) were selected for analysis from 128 cross-sectional images, and novel 2-dimensional and 3-dimensional anterior segment parameters namely angle opening distance area (AODA) and the trabecular-iris space volume (TISV) 750 µm from the scleral spur, as well as iris parameters such as iris thickness (IT750 and IT2000), iris curvature, and iris curvature area were measured for each image.

RESULTS

AODA and TISV were significantly increased and the iris curvature and iris curvature area were significantly decreased at days 7, 30, and 90 after LPI when compared with their baseline (all P<0.001) but there was no significant change in the IT750 and IT2000 (all P>0.05). The multivariable linear regression model showed a significant association of ΔAODA with refractive error (β=-0.23, P=0.013), lens vault (β=2.8, P=0.007), and iris volume (β=-0.11, P=0.027) after adjusting for age and sex.

CONCLUSIONS

LPI widened the iridocorneal angle and flattened the iris circumferentially in Caucasian eyes in this study. Baseline refractive error, lens vault, and iris volume play a significant role in the circumferential angle widening by LPI.

Iridocorneal contact as a potential cause of corneal decompensation following laser peripheral iridotomy

PURPOSE

This study aimed to investigate the relationship between corneal decompensation following laser peripheral iridotomy (LPI) and iridocorneal endothelial contact.

STUDY DESIGN

Retrospective observational case series.

METHODS

Specular microscopy images of LPI recipients with narrow angles were taken at the central cornea and the 8 midperipheral corneal regions at approximately 3 mm from the center. Eleven eyes of 11 patients had a minimum of  ≤ 1600 cells/mm² among 8 midperipheral corneal endothelial cell densities (ECDs). Radial scans of the angles in the 8 directions were taken with ultrasound biomicroscopy (UBM) in the supine and face-down positions. The minimum and maximum angle opening distance at 750 μm from the scleral spur of the 8 directions were defined as the narrowest and widest angles, respectively. The ECD of the narrowest angle direction was compared with the ECD of the widest angle direction.

RESULTS

When UBM was performed with the subject in the supine position, the iris and cornea at the narrowest angle were in contact in only 4 of 11 eyes, while in the face-down position, the iris and the cornea at the narrowest angle were in contact in 10 of the 11 eyes. In the face-down UBM, the midperipheral ECD of the narrowest angle direction was significantly smaller than the midperipheral ECD of the widest angle direction (P = 0.006).

CONCLUSION

The ECD of the narrow angle direction can decrease after LPI. This suggests that corneal endothelial cell damage following LPI may be due to mechanical damage from iridocorneal endothelial contact.

Association of anterior segment parameters and 5-year incident narrow angles: findings from an older Chinese population

PURPOSE

To assess the association of anterior segment optical coherence tomography (AS-OCT) parameters and 5-year incident narrow angle in China.

METHODS

This was a prospective cohort study of people aged 50 and older residing in Liwan District, Guangzhou, China. Random clustering sampling was used to identify adults aged 50 years and older in Liwan District, Guangzhou. In 2008 and 2013, this study was repeated and added AS-OCT imaging under dark and light conditions. Customised software (ZAAP) was used to analyse horizontal AS-OCT scans. Angle opening distance (AOD), trabecular iris space area (TISA), anterior chamber volume (ACV) and maximal iris thickness (ITM) were measured. Multiple logistic regression analysis models were used to investigate the associations of the final angle status with baseline AS-OCT parameters. ORs and 95% CIs were calculated.

RESULTS

Of the 220 subjects with eligible AS-OCT images and gonioscopic results in 2008, the response rate was 77.3%. A total of 27 (15.9%) subjects developed narrow angles and 143 (84.1%) had open angles on gonioscopy in 2013. Subjects developed narrow angles had greater spherical equivalent and shallower anterior chamber depth, smaller angle parameters, thicker IT750 and ITM, smaller anterior chamber parameters, greater lens vault, and smaller dynamic parameters (ΔITM, ΔACA, ΔACV) at baseline. After adjusting confounders, the predictors of incident narrow angles included smaller AOD750, TISA750, ΔACA and greater ITM, ΔIarea.

CONCLUSIONS

Incident narrow angles were associated with smaller anterior ocular dimensions, thicker iris and smaller light-to-dark changes at baseline. These findings can help in early diagnosis in this population.

Outcome Following Laser Peripheral Iridotomy and Predictors of Future Lens Extraction

PURPOSE

To examine the outcome of laser peripheral iridotomy (LPI) for primary angle closure and determine predictors of future lens extraction (LE).

METHODS

A retrospective chart review of 218 eyes from 128 consecutive patients undergoing LPI between 2010 and 2012 at a university hospital. Baseline factors including age, peak intraocular pressure (IOP) before LPI, diagnosis (primary angle closure suspect, primary angle closure, primary angle closure glaucoma), and acute or non-acute presentation were recorded. Patients were followed for 3.7±1.6 years. Kaplan-Meier curves were constructed to examine survival times to LE and Cox proportional hazard regression was used to identify factors associated with LE.

RESULTS

In total, 91 of 218 eyes (41.7%) initially treated with LPI had LE during follow-up. For eyes with non-acute presentation, 12%, 25%, and 32% had LE at 1, 2, and 3 years, respectively. For eyes with acute presentation, 27%, 42%, and 50% had LE at 1, 2, and 3 years. In univariable analysis, older age, higher IOP, worse visual field, and primary angle closure glaucoma diagnosis were associated with LE, with older age and higher IOP remaining significant in multivariable analysis. There was a 1.09-fold increased odds of LE for each year older at baseline and each 1 mm Hg higher IOP was associated with a 1.08-fold increased odds of LE.

CONCLUSIONS

A large proportion of patients with angle closure treated with LPI went on to require LE. Patients with features associated with higher odds of LE might be considered for LE as a primary procedure.

Update on the usefulness of optical coherence tomography in assessing the iridocorneal angle

The iridocorneal angle, due to its implications in the physiopathology of aqueous humour drainage, is a fundamental structure of the anterior chamber. Anterior segment optical coherence tomography is a rapid and non-invasive technique that obtains images in vivo. The high resolution allows it to analyse the normal anatomy of the angle, any alterations, and the changes that occur after different therapeutic interventions. Anterior segment optical coherence tomography technology has evolved to provide images that allow the identification and quantification of the angular structures in healthy subjects and in glaucoma patients, and especially the trabecular meshwork and the Schlemm's canal. It also enables the angle width to be quantified, with some objective parameters that have been standardised in recent years, such as the trabecular-iris angle, the angle opening distance, and the trabecular-iris area. This technique has multiple uses in the study of the different mechanisms of angle closure, the evaluation of changes after a laser peripheral iridotomy or iridoplasty after cataract surgery, as well as after the implantation of phakic lenses.

Longitudinal Change in Peripheral Anterior Chamber Depth of Eyes with Angle Closure after Laser Iridotomy

Purpose

To investigate longitudinal changes in peripheral anterior chamber depth (pACD) of eyes with angle closure after laser iridotomy (LI) and factors related to prognosis.

Design

Retrospective cohort study.

Methods

Eyes with primary angle closure (PAC), acute PAC, or chronic angle closure glaucoma (CACG) that underwent LI (LI group) and eyes that underwent phacoemulsification and intraocular lens insertion (PEA + IOL group) were employed. Longitudinal changes in pACD were evaluated with a scanning peripheral anterior chamber depth analyzer (SPAC) in addition to routine ophthalmic examination.

Results

Forty-eight eyes of LI groups (69.8 ± 8.5 years) and 21 eyes of PEA + IOL group (65.6 ± 12.7 years) were enrolled. Mean follow-up times of LI group and PEA + IOL group were 43.4 ± 12.7 months and 36.5 ± 2.5 months, respectively. LI significantly increased pACD as indicated by the SPAC grade change from 3.8 ± 1.1 to 4.6 ± 1.2 (p < 0.001). However, SPAC grade was gradually reduced and reached the pre-LI level by the third year of follow up. PEA + IOL also significantly increased SPAC grade from 6.7 ± 1.6 to 8.7 ± 2.0 (p < 0.001), but no time-related change was observed. Twenty-three cases of LI group presented with deterioration of glaucoma control. The type of angle closure, plateau iris configuration, peripheral anterior synechia, and glaucomatous visual field defects were significantly associated with prognosis of glaucoma after LI.

Conclusions

Peripheral ACD is temporarily deepened by LI, but returns to the pre-LI level in approximately three years. The type of angle closure and some factors may be related to glaucoma prognosis after LI.

Predicting the Therapeutic Efficacy of Laser Peripheral Iridotomy for Individuals With Asymptomatic Narrow Angle: The Triple Hump Sign

PURPOSE

To evaluate the clinical efficacy of a novel screening sign [ie, the triple hump (TH) sign] for prediction of laser peripheral iridotomy (LPI)'s intraocular pressure (IOP)-lowering effectiveness in subjects with asymptomatic narrow angles.

METHODS

This cross-sectional study was conducted from 2010 to 2015 in a hospital setting. Eighty-four eyes of 84 primary angle-closure suspect (PACS) patients were imaged before LPI using anterior segment optical coherence tomography. The "positive-TH sign" was defined, on anterior segment optical coherence tomography-generated cross-sectional scans, as the characteristic configuration formed by the angulations between the crystalline lens's central anterior surface and both sides of the iris pigment epithelium. After LPI, the extent of IOP reduction was compared between the positive- and negative-TH groups.

RESULTS

The positive-TH eyes did not significantly differ from the negative-TH ones in pre-LPI IOP (P=0.200). In the positive-TH group, IOP decreased significantly after LPI (by 6.42%±17.96%, from 14.07±3.11 to 12.88±2.65 mm Hg, P=0.002). In the negative-TH group, IOP did not change significantly after LPI (by 4.66%±25.97%, from 13.23±2.42 to 13.52±3.01 mm Hg, P=0.624).

CONCLUSION

PACS eyes indicating the positive-TH sign showed, at post-LPI 1 month, a greater IOP decrease. On this basis, the TH sign may be a useful screening tool for predicting the effect of LPI and determining the treatment plan in PACS patients.

Long-term Changes in Anterior Segment Characteristics of Eyes With Different Primary Angle-Closure Mechanisms

PURPOSE

To assess long-term changes in the anterior segment (AS) of eyes with different angle-closure mechanisms.

DESIGN

Retrospective cohort study.

METHODS

In total, 133 eyes (from 75 participants) with angle closure were enrolled. All eyes received laser iridotomy (LI) during the follow-up period. Serial anterior segment optical coherence tomography (AS-OCT) imaging was performed during a mean follow-up of 4 years. Participants were categorized into 4 groups according to angle-closure mechanisms, based on baseline AS-OCT images: pupillary block (PB), plateau iris configuration (PIC), thick peripheral iris roll (TPIR), and exaggerated lens vault (ELV). Linear mixed-effect models were applied to evaluate the longitudinal changes in AS-OCT parameters (anterior chamber depth [ACD], lens vault [LV], and angle opening distance [AOD]).

RESULTS

Forty-six eyes (35%) were classified as PB, 30 (23%) as PIC, 34 (26%) as TPIR, and 23 (17%) as ELV. The follow-up period was 41-54 months. At baseline, ACD was shallowest in ELV, followed by PB, TPIR, and PIC, in order. The PIC group showed significantly wider AOD than the other groups at baseline. ACD decreased and LV increased over time in all groups, especially in the PIC group. After LI, the angle widened in the PB and TPIR groups, but not in the PIC and ELV groups.

CONCLUSIONS

AS parameters changed differently in the 4 groups. The effects of LI on AOD also differed among groups. Identification of the angle-closure mechanism may help predict progressive changes in AS parameters in eyes with angle closure.

Anterior Segment Imaging for Angle Closure

PURPOSE

To summarize the role of anterior segment imaging (AS-imaging) in angle closure diagnosis and management, and the possible advantages over the current standard of gonioscopy.

DESIGN

Literature review and perspective.

METHODS

Review of the pertinent publications with interpretation and perspective in relation to the use of AS-imaging in angle closure assessment focusing on anterior segment optical coherence tomography and ultrasound biomicroscopy.

RESULTS

Several limitations have been encountered with the reference standard of gonioscopy for angle assessment. AS-imaging has been shown to have performance in angle closure detection compared to gonioscopy. Also, imaging has greater reproducibility and serves as better documentation for long-term follow-up than conventional gonioscopy. The qualitative and quantitative information obtained from AS-imaging enables better understanding of the underlying mechanisms of angle closure and provides useful parameters for risk assessment and possible prediction of the response to laser and surgical intervention. The latest technologies-including 3-dimensional imaging-have allowed for the assessment of the angle that simulates the gonioscopic view. These advantages suggest that AS-imaging has a potential to be a reference standard for the diagnosis and monitoring of angle closure disease in the future.

CONCLUSIONS

Although gonioscopy remains the primary method of angle assessment, AS-imaging has an increasing role in angle closure screening and management. The test should be integrated into clinical practice as an adjunctive tool for angle assessment. It is arguable that AS-imaging should be considered first-line screening for patients at risk for angle closure.

Anterior segment imaging in glaucoma: An updated review

Anterior segment imaging allows for an objective method of visualizing the anterior segment angle. Two of the most commonly used devices for anterior segment imaging include the anterior segment optical coherence tomography (AS-OCT) and the ultrasound biomicroscopy (UBM). AS-OCT technology has several types, including time-domain, swept-source, and spectral-domain-based configurations. We performed a literature search on PubMed for articles containing the text “anterior segment OCT,” “ultrasound biomicroscopy,” and “anterior segment imaging” since 2004, with some pertinent references before 2004 included for completeness. This review compares the advantages and disadvantages of AS-OCT and UBM, and summarizes the most recent literature regarding the importance of these devices in glaucoma diagnosis and management. These devices not only aid in visualization of the angle, but also have important postsurgical applications in bleb and tube imaging.

Anterior segment configuration as a predictive factor for refractive outcome after cataract surgery in patients with glaucoma

Background

To compare refractive outcomes after cataract surgery between patients with closed-angle and open-angle glaucoma and evaluate the influence of preoperative factors on refractive outcomes in patients with glaucoma.

Methods

Patients diagnosed with glaucoma and who underwent uncomplicated cataract surgery were enrolled in this retrospective observational study. We collected data including age, history of prior laser peripheral iridotomy and trabeculectomy, type of glaucoma, manifest refraction, intraocular pressure, axial length, and various anterior segment parameters using anterior-segment optical coherence tomography. Factors associated with unsatisfactory refractive outcome at postoperative 6 month were evaluated.

Results

A total of 143 eyes (143 subjects) were included. Of these, 49 and 94 had closed-angle and open-angle glaucoma, respectively. At postoperative-6 month evaluation, the mean absolute error (MAE) predicted by the SRK-II and SRK-T formulae was 0.67 ± 0.61 and 0.81 ± 0.66 diopters (D), respectively. The overall predictability of achieving within ± 1.0 D of target was 76.92 % and 72.73 %, respectively. At a cutoff value of 1.0 D for MAE, there was no statistical significant difference in refractive outcome between the closed-angle and open-angle glaucoma groups. Logistic regression modeling showed that large lens vault (LV) was a significant predictor of unsatisfactory refractive outcome after cataract surgery in patients with glaucoma.

Conclusions

When considering cataract surgery in patients with glaucoma, surgeons should recognize that the refractive outcomes may be unsatisfactory in eyes with large LV.

Clinical and Anterior Segment Anatomical Features in Primary Angle Closure Subgroups Based on Configurations of Iris Root Insertion

Purpose

To compare the clinical and anterior segment anatomical features in primary angle closure sub-groups based on configurations of iris root insertion.

Methods

Primary angle closure patients were imaged using anterior segment optical coherence tomography. Anterior chamber depth, iris curvature, iris thickness (IT) at the scleral spur and 500, 750, and 1,500 µm from the scleral spur (IT₀, IT₅₀₀, IT₇₅₀, and IT₁₅₀₀), lens vault, iris area, angle opening distance (AOD₅₀₀), angle recess area (ARA₇₅₀), and trabecular iris space area (TISA₇₅₀) were measured. Iris root insertion was categorized into a non-basal insertion group (NBG) and basal insertion group (BG).

Results

In total, 43 eyes of 39 participants belonged to the NBG and 89 eyes of 53 participants to the BG. The mean age of participants was greater in the NBG than the BG (62.7 ± 5.7 vs. 59.8 ± 7.3 years, p = 0.043), and the baseline intraocular pressure was higher in the BG than the NBG (16.4 ± 4.4 vs. 14.9 ± 3.3 mmHg, p = 0.037). The BG showed a greater IT₀ (0.265 ± 0.04 vs. 0.214 ± 0.03 mm, p < 0.001) and iris area (1.59 ± 0.24 vs. 1.52 ± 0.27 mm², p = 0.045), lower ARA₇₅₀ (0.112 ± 0.08 vs. 0.154 ± 0.08 mm², p = 0.017) and AOD₅₀₀ (0.165 ± 0.07 vs. 0.202 ± 0.08 mm, p = 0.014) compared to the NBG.

Conclusions

The BG had a narrower anterior chamber angle, thicker peripheral iris, and higher pretreatment intraocular pressure.

Effects of Laser Peripheral Iridotomy in Subgroups of Primary Angle Closure Based on Iris Insertion

Purpose. To investigate the effect of laser peripheral iridotomy (LPI) in subgroups of primary angle closure based on iris insertion configuration. Methods. Anterior segment optical coherence tomography (AS-OCT) images were obtained before and two weeks after LPI. Qualitative classification of angle closure eyes according to iris insertion (basal insertion group (BG) and nonbasal insertion group (NBG)) was performed. Anterior chamber depth (ACD), lens vault (LV), iris curvature, iris area, iris thickness (IT₇₅₀), and angle opening distance (AOD₇₅₀) 750 microns from scleral spur were calculated. Uni- and multivariate regression analysis was carried out to evaluate factors associated with AOD₇₅₀ before and after LPI. Results. Ninety-two eyes of 92 subjects were categorized as NBG (39 eyes) or BG (53 eyes). The mean change after LPI was not significantly different between two groups in all parameters. In both groups, AOD₇₅₀ was affected by ACD (p < 0.001, p = 0.044) before LPI. AOD₇₅₀ was affected by LV (p = 0.012) in NBG, but by ACD (p < 0.001) and IT₇₅₀ (p = 0.039) in BG after LPI. Conclusions. The outcomes of LPI are not significantly different between angle closure subgroups with different iris insertions. However, factors affecting AOD₇₅₀ show differences between two subgroups after LPI.