Anatomic Predictors for Anterior Chamber Angle Opening After Laser Peripheral Iridotomy in Narrow Angle Eyes

Long-term effects of mild cataract extraction versus laser peripheral iridotomy on anterior chamber morphology in primary angle-closure suspect eyes

AIM

To compare lens extraction (LE) and laser peripheral iridotomy (LPI) on anterior segment morphology in primary angle-closure suspect (PACS) eyes.

METHODS

This prospective clinical trial included 144 patients with PACS who underwent either LPI or LE. Ultrasound biomicroscopy (UBM) and gonioscopy were performed before and 1 month and 2 years after operation. Main outcomes included UBM parameters and the percentage of residual angle closure.

RESULTS

At both 1 month and 2 years of follow-up, LE showed a better effect of relieving anterior chamber crowding and widening the drainage angle, as obtaining a larger anterior chamber depth (ACD), angle opening distance, trabecular iris angle (TIA), trabecular iris space area, trabecular ciliary process distance (TCPD) and a smaller iris curvature (I-Curv) and lens vault (LV) (p<0.001). In the LPI group, angle width increased (angle opening distance at 500 µm from the scleral spur, TIA and trabecular iris space area at 500 µm from the scleral spur) and I-Curv decreased (p<0.001) at 1 month postoperatively, with no significant changes in ACD, LV or TCPD. However, at 2 years after LPI, the angle narrowed with the increase in LV over time, and the proportion of residual angle closure also increased from 21.7% to 30.4% (p<0.001). In contrast, after LE, the widened angle width, flattened iris, deepened ACD, decreased LV and increased TCPD all showed good sustainability in the comparison between 1-month and 2-year follow-up. No residual angle closure was observed either at 1 month or 2 years after LE.

CONCLUSIONS

LE was prior to LPI in widening the drainage angle. After LPI, there was a narrowing of the angle and an increase in the proportion of residual angle closure over time. LE could achieve a wider angle with no residual angle closure, and the anterior segment parameters were sustainable.

TRIAL REGISTRATION NUMBER

ChiCTR1800016511.

[Predictors of the success of laser peripheral iridotomy and lensectomy in the early stages of primary angle closure disease]

The article reviews literature data on the search for predictors of the success of laser peripheral iridotomy (LPI) and lensectomy in the early stages of primary angle closure disease (PACD) and presents a trend analysis of the studies conducted on individuals identified as primary angle closure suspects (PACs) and those with primary angle closure (PAC). The concept of the review was determined by the ambiguous choice of treatment for patients at the stage of PAC onset. Determining the success predictors of LPI or lensectomy plays a key role in optimizing the treatment of PACD. The results of literature analysis are contradictory, which indicates the need for further research taking into account modern methods of visualization of the eye structures such as optical coherence tomography (OCT), Swept Source OCT (SS-OCT), and the use of uniform criteria for evaluating the effectiveness of treatment.

Classifications of Qualitative Characteristics on Angle Configurations via Ultrasound Biomicroscopy in Acute Primary Angle Closure

Purpose

To study the classifications of qualitative characteristics on the angle configurations in the acute primary angle closure (APAC) and fellow eyes by ultrasound biomicroscopy (UBM).

Methods

A total of 131 patients (262 eyes) were researched retrospectively. The qualitative parameters from UBM images were classified into iris form (IF), ciliary body configuration (CBC), basal iris thickness (BIT), iris convexity (IC), iris insert (II), iris angulation (IA), ciliary body size (CBS) and ciliary body position (CBP). Comparative analyses between the APAC (case group) and fellow (control group) eyes were performed.

Results

There were significant differences in IF, CBC, IC, II, CBS, CBP between the case group and control group in all quadrants (P<0.001). The IA of the case group and control group presented significant difference in all quadrants (P=0.001). However, there was not a significant difference in BIT between the case group and control group in all quadrants (P=0.495). The case group had fewer parallelogram-like and mushroom-like and more cone-like and hook-like CBCs than the control group (P<0.001).

Conclusion

Multiple ciliary body configurations can influence the stability of the lens and the anatomic configuration of the anterior chamber angle indirectly. New qualitative classification system of UBM may be more intuitionistic and refined to reflect the angle configurations to help clinical practice.

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

Background

Primary angle closure glaucoma (PACG) is the most common type of glaucoma in China. Laser peripheral iridotomy (LPI) is the primary choice to treat PAC: We aim to evaluate the changes of biometric parameters of anterior segment and to find possible biometric predictors of the effect of laser peripheral iridotomy (LPI) in primary angle closure (PAC) eyes using swept-source optical coherent tomography (OCT).

Methods

LPI was performed in 52 PAC eyes of 28 participants. The change of intraocular pressure and anterior segment parameters, including angle opening distance (AOD500), AOD500 area, trabecular iris space area (TISA500), TISA500 volume, trabecular iris angle (TIA500), iridotrabecular contact (ITC) index, ITC area, anterior chamber volume (ACV), anterior chamber depth (ACD), lens vault (LV) and lens thickness (LT) before and 1 week after LPI were measured by Tomey CASIA2 anterior segment OCT. We also estimate and analyze potential associated factors possibly affecting the change of anterior chamber parameters.

Results

No post-laser complications were found. The ACD, LV and LT did not change significantly 1 week after LPI. AOD500, AOD500 area, TISA500, TISA500 volume, TIA500, ACV increased significantly after LPI. There was significant decrease in ITC index and ITC area. LT was positively correlated to the change of ITC index (β = 0.239, *p = 0.045).

Conclusions

The anterior segment architecture significantly changed after LPI in PAC spectrum eyes. Crystalline lens measurements remained unchanged before and after LPI. AS-OCT can be used to follow anterior chamber parameter changes in PAC spectrum eyes. LT may play a role in the therapeutic effect of LPI.

Predictive Equation for Angle Opening Distance at 750 μm After Laser Peripheral Iridotomy in Primary Angle Closure Suspects

Aim: The aim of this study was to investigate the changes in anterior segment parameters as assessed by ultrasound biomicroscopy (UBM) after laser peripheral iridotomy (LPI) and to propose a prediction equation for the width of the angle after LPI. Design: This was a prospective study. Participants: The participants included 100 subjects with primary angle closure suspect (PACS). Methods: Anterior segment UBM parameters were measured, whereas AOD750 was chosen to indicate the width of the angle associated with gonioscopic angle closure, as found in a prior study. Main Outcome Measures: Angle parameters, iris parameters, anterior chamber parameters and ciliary body parameters. Results: All angle parameters increased after LPI, including the mean angle opening distance at 750 μm (AOD750), mean angle opening distance at 500 μm from the scleral spur (AOD500), mean angle opening distance at 750 μm from the scleral spur (AOD750), and mean angle recess area at 750 μm from the scleral spur (ARA750). Among iris parameters and ciliary body parameters, the iris thickness at 2,000 μm (IT2000), iris curvature (IC), and trabecular-ciliary process distance (ICPD) were reduced after LPI. The final equation consisted of four parameters: anterior chamber depth (ACD), iris thickness at 750 μm from the scleral spur (IT750), AOD750, and lens vault (LV). This equation explained 42.7% of the variability in the angle opening indicator AOD750 after LPI, whereas in the plateau iris configuration subgroup, the accuracy of the prediction equation reached the highest a maximum of 68.6%. Conclusions: There was an increase in angle opening and iris flattening after LPI. An equation involving four angle parameters was constructed, this equation which could explained 42.7% of the variability in the angle opening indicator AOD750 after LPI whereas in the plateau iris configuration subgroup, the accuracy of the prediction equation reached a maximum of 68.6%.

Associations of lens thickness and axial length with outcomes of laser peripheral iridotomy

AIM

To investigate the association of axial length (AL), lens thickness (LT), and lens vault (LV) with postoperative anterior chamber angle metrics after laser peripheral iridotomy (LPI).

METHODS

Prospective observational study of 69 patients (97 eyes) were diagnosed as primary angle-closure suspect (PACS), primary angle closure (PAC) or primary angle-closure glaucoma (PACG). AL, LT, anterior central chamber depth (ACD), angle opening distance (AOD), trabecular iris angle (TIA), and angle recess area (ARA) were measured before and 1wk after LPI. The association between AL, LT, LV with ACD, AOD, TIA, ARA were analyzed by comparing the differences between preoperative and postoperative measurements for anterior segment biometric parameters.

RESULTS

ACD, AOD, TIA, and ARA were significantly increased after LPI (all P<0.05). Greater LT was significantly associated with greater postoperative increases in ACD, AOD, TIA, and ARA (all P<0.05). AL was not significantly associated with changes of anterior segment biometric parameters. Greater LV was significantly associated with greater postoperative increases in ACD, AOD, and TIA (all P<0.05), but was not significantly associated with changes of ARA.

CONCLUSION

Greater baseline LT and LV measurements are associated with greater increases in anterior segment biometric parameters after laser peripheral iridotomy. AL are not associated with the change of anterior segment biometric parameters.

Anatomic Changes and Predictors of Angle Widening after Laser Peripheral Iridotomy: The Zhongshan Angle Closure Prevention Trial

PURPOSE

To assess anatomic changes after laser peripheral iridotomy (LPI) and predictors of angle widening based on anterior segment (AS) OCT and angle opening based on gonioscopy.

DESIGN

Prospective observational study.

PARTICIPANTS

Primary angle-closure suspects (PACSs) 50 to 70 years of age.

METHODS

Participants of the Zhongshan Angle Closure Prevention (ZAP) Trial underwent gonioscopy and AS-OCT imaging at baseline and 2 weeks after LPI. Primary angle-closure suspect was defined as the inability to visualize pigmented trabecular meshwork in 2 or more quadrants on static gonioscopy. Laser peripheral iridotomy was performed on 1 eye per patient in superior (between 11 and 1 o'clock) or temporal or nasal locations (at or below 10:30 or 1:30 o'clock). Biometric parameters in horizontal and vertical AS-OCT scans were measured and averaged. Linear and logistic regression modeling were performed to determine predictors of angle widening, defined as change in mean angle opening distance measured at 750 μm from the scleral spur (AOD₇₅₀); poor angle widening, defined as the lowest quintile of change in mean AOD₇₅₀; and poor angle opening, defined as residual PACS after LPI based on gonioscopy.

MAIN OUTCOME MEASURES

Anatomic changes and predictors of angle widening and opening after LPI.

RESULTS

Four hundred fifty-four patients were included in the analysis. Two hundred nineteen underwent superior LPI and 235 underwent temporal or nasal LPI. Significant changes were found among most biometric parameters (P < 0.006) after LPI, including greater AOD₇₅₀ (P < 0.001). One hundred twenty eyes (26.4%) showed residual PACS after LPI. In multivariate regression analysis, superior LPI location (P = 0.004), smaller AOD₇₅₀ (P < 0.001), and greater iris curvature (P < 0.001), were predictive of greater angle widening. Temporal or nasal LPI locations (odds ratio [OR], 2.60, P < 0.001) was predictive of poor angle widening. Smaller mean gonioscopy grade (OR, 0.34, 1-grade increment) was predictive of poor angle opening.

CONCLUSIONS

Superior LPI location results in significantly greater angle widening compared with temporal or nasal locations in a Chinese population with PACS. This supports consideration of superior LPI locations to optimize anatomic changes after LPI.

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.

Effects of lens extraction versus laser peripheral iridotomy on anterior segment morphology in primary angle closure suspect

PURPOSE

To compare the anatomical effects on anterior segment by lens extraction (LE, phacoemulsification with posterior chamber intraocular lens implantation) and laser peripheral iridotomy (LPI) in primary angle closure suspect (PACS) eyes.

METHODS

This prospective comparative cohort trial included a total of 122 consecutive patients identified as PACS aged 52 to 80 years. LE or LPI was performed based on each patient's choice. The anterior segment optical coherence tomography (ASOCT) and gonioscopy were conducted at baseline and 4 weeks post-operation. Outcome measures include percentage of residual angle closure, mean angle width (modified Shaffer grade), angle opening distance (AOD), trabecular iris angle (TIA), trabecular iris space area (TISA), anterior chamber depth (ACD), iris curvature (I-Curve), lens vault (LV), intraocular pressure (IOP), and best-corrected visual acuity (BCVA).

RESULTS

All anterior angle parameters (AOD, TIA, and TISA) were significantly greater after LE than LPI (P < 0.001 for all). ACD (P < 0.001) increased, LV (P < 0.001) decreased, IOP (P < 0.001) decreased, and BCVA (P < 0.001) increased after LE. However, no significant changes were found in ACD (P = 0.782), LV (P = 0.616), IOP (P = 0.112), and BCVA (P = 0.131) after LPI. In both groups, I-Curve decreased after the operation, but the iris was flatter after LE than LPI (P < 0.001). Gonioscopically, the LE group achieved a larger post-operative angle width (modified Shaffer grade) than LPI (P < 0.001) and all anterior chamber angles were open (defined as posterior pigmented trabecular meshwork (PTM) visible with static gonioscopy) after operation. Nevertheless, after LPI, 12 eyes (20.0%) still had two or more quadrants and 32 eyes (53.3%) still had at least one quadrant in which the posterior PTM could not be observed.

CONCLUSIONS

Compared with LPI, LE resulted in a wider anterior chamber angle, a deeper anterior chamber, and a lower IOP in PACS eyes. Moreover, no residual angle closure was observed after LE, which could morphologically prevent the progress of angle closure.

TRIAL REGISTRATION

ChiCTR1800016511.

Predicting the outcome of laser peripheral iridotomy for primary angle closure suspect eyes using anterior segment optical coherence tomography

PURPOSE

Develop an algorithm to predict the success of laser peripheral iridotomy (LPI) in primary angle closure suspect (PACS), using pretreatment anterior segment optical coherence tomography (ASOCT) scans.

METHODS

A total of 69 eyes with PACS underwent LPI and time-domain ASOCT scans (temporal and nasal cuts) were performed before and after LPI. After LPI, success is defined as one or more angles changed from closed to open. All the pretreatment ASOCT scans were analysed using the Anterior Segment Analysis Program to derive anterior chamber angle (ACA) measurements. The measurements for each angle were ordered along with angle-independent measurements totalling to 42 measurements which serve as features for the prediction algorithm. Two masked glaucoma fellowship-trained ophthalmologists graded the pre-LPI ASOCT scans to determine whether LPI was likely to successful.

RESULTS

There were 42 (60.9%) eyes that fulfilled the criteria for success after LPI. Iris concavity, angle recess area (750 μm) and iris concavity ratio showed the highest predictive score and were selected using correlation-based subset selection method. These features were classified into two ('successful' and 'unsuccessful') categories using a Bayes classifier. The algorithm predicted the success of LPI with 79.28% cross validation accuracy, which was superior to the predictive accuracy of the ophthalmologists (kappa 0.497 and 0.636 respectively).

CONCLUSION

Using pretreatment ASOCT scans, our algorithm was superior to ophthalmologists in predicting the success of LPI for PACS eyes. This novel algorithm could aid decision making in offering LPI as a prophylaxis for PACS.

Anterior Segment Dimensions Following Laser Iridotomy in Acute Primary Angle Closure and Fellow Eyes

PURPOSE

To compare the change in anterior segment morphology after laser peripheral iridotomy (LPI) in acute primary angle closure (APAC) and their fellow eyes.

DESIGN

Prospective, fellow eye-matched case series.

METHODS

In this study 42 individuals with unilateral episode of APAC were enrolled and the anterior segment optical coherence tomography (ASOCT) images were obtained in both eyes at baseline and at 6 weeks after LPI. A linear mixed-effects model was used to compare changes in anterior chamber and angle variables with consideration of laterality as the random effect and pupil diameter as the fixed effect.

RESULTS

APAC eyes had smaller angle parameters (P = .013 for all), less central anterior chamber depth (cACD) (P < .001), and lower anterior chamber area (ACA) (P < .001), as well as greater lens vault (LV) (P = .007), compared with fellow eyes. LPI resulted in angle widening with a significant increase in opening distance (P < .01 for all) in both APAC and fellow eyes. cACD (P = .003) and ACA (P < .001) increased and LV (P = .002) decreased in APAC eyes. However, there was no significant change in cACD (P = .190) and LV (P = .430) in fellow eyes. In both APAC eyes and fellow eyes, iris curvature decreased after LPI (P < .001). The changes in angle parameters, ACA, and iris curvature were not significantly different between the 2 groups.

CONCLUSION

In APAC eyes and their fellow eyes, LPI resulted in significant anterior chamber angle widening and increased anterior chamber area. In APAC eyes, the iris flattened, cACD deepened, and the lens shifted posteriorly after resolution of the attack. However, in fellow eyes, the increase in ACA was mainly owing to decreased iris curvature.

Anterior segment morphology after laser iridotomy in primary angle closure suspects

PURPOSE

To evaluate and compare the changes in anterior segment parameters in primary angle closure suspects before and after laser peripheral iridotomy and intrasession repeatability of measurements before laser iridotomy as assessed by Scheimpflug-Placido disc topographer.

METHODS

Before laser iridotomy, 56 eyes of 56 primary angle closure suspect patients underwent anterior segment analysis with the Sirius Scheimpflug-Placido disc topographer system using glaucoma analysis mode, which was repeated a week after iridotomy. Anterior segment parameters such as central anterior chamber depth, central corneal thickness, anterior chamber volume and iridocorneal angle were analysed before and after laser iridotomy and compared with paired t-test. Three consecutive scans were obtained to assess the intrasession repeatability of measurements before iridotomy by a single examiner and intraclass correlation co-efficient was calculated. Multivariate regression analysis was performed to evaluate the predictors associated with iridocorneal angle narrowing.

RESULTS

Intraclass correlation co-efficient values ranged from 0.982 for anterior chamber volume to 0.998 for the iridocorneal angle. After laser iridotomy, mean central anterior chamber depth increased from 2.14 ± 0.29 mm to 2.21 ± 0.28 mm (p = 0.04), mean anterior chamber volume increased from 96.2 ± 16.98 mm³ to 98.14 ± 15.87 mm³ (p < 0.0001) and mean iridocorneal angle widened from 33.38 ± 3.96° to 34.82 ± 4.27° (p = 0.01), compared with pre-iridotomy status. There was no change in central corneal thickness, intraocular pressure or pupil diameter. Multivariate regression analysis model showed that at one week after iridotomy, iridocorneal angle opening was positively correlated with age (β = 0.773, p = 0.005) and anterior chamber volume (β = 1.308, p < 0.0001).

CONCLUSIONS

Laser peripheral iridotomy induces significant changes in the 3-D anterior segment morphology in primary angle closure suspect patients. The Scheimpflug-Placido disc topographer provides reproducible measurements of the iridocorneal angle and other parameters measured and hence, may become clinically useful for non-invasive detection of potentially occludable angles. Predictors of iridocorneal angle widening after iridotomy were older age and anterior chamber volume.

Associated factors of acute primary angle closure glaucoma in a sub-group of Chinese people: comparison between attack eyes and normal controls

Acute primary angle closure glaucoma (APACG) is an ophthalmic emergency that may lead to irreversible blindness. Although efforts were made to control intraocular pressure, disease progression still existed. Anterior segment optical coherence tomography (AS OCT) may provide a new insight into mechanism of APACG. In order to seek out associated factors by AS OCT, We compared anterior segment parameters between 74 APACG and 48 normal eyes. Analysis of variance, principle component analysis and logistic regression were used. APACG group had more women (75.7% vs 47.9%, p = 0.002), smaller anterior chamber (anterior chamber depth, ACD; anterior chamber area, ACA; all p = 0.001), narrower angle (AOD500, AOD750, angle opening distance at 500um and 750um; TISA500, TISA750, trabecular-iris space area at 500um and 750um; ARA500, ARA750, angle recess area at 500um and 750um; all p < 0.001), thinner iris (iris thickness at 750um, IT750; maximum of iris thickness, ITMAX; all p < 0.001), larger iris area (IA, p < 0.001) and lens vault (LV, p = 0.005). Principle component extracted were AOD500, AOD750, TISA500, TISA750, ARA500, ARA750, IA, PD (pupillary diameter), ACD, ACA and IT750. After adjusting for confounding factors, AOD750 (b = 12.40 ± 2.56, p < 0.001), IT750 (b = 10.50 ± 3.45, p = 0.002) and IA (b = −1.56 ± 0.77, p = 0.044) were significantly associated with occurrence of APACG.

Changes in Anterior Segment Morphology and Predictors of Angle Widening after Laser Iridotomy in South Indian Eyes

PURPOSE

To compare anterior segment optical coherence tomography (ASOCT) angle morphology before and after laser peripheral iridotomy (LPI) in a cohort of South Indian subjects with primary angle-closure suspect (PACS) or primary angle-closure/primary angle-closure glaucoma (PAC/PACG) and to examine baseline parameters associated with angle widening.

DESIGN

Prospective observational study.

PARTICIPANTS

A total of 244 subjects aged ≥30 years with PACS or PAC/PACG in at least 1 eye.

METHODS

The ASOCT images and angle gonioscopic grades were analyzed for all subjects at baseline and 2 weeks after LPI. Multivariable linear and logistic regression models were used to determine predictors of angle widening (change in mean angle opening distance [AOD750]) and angle opening (all 4 quadrants with trabecular meshwork [TM] visible on gonioscopy after LPI).

MAIN OUTCOME MEASURES

Change in ASOCT parameters with LPI and baseline predictors of angle widening.

RESULTS

Laser peripheral iridotomy resulted in angle widening on ASOCT with significant increases in AOD750, angle recess area, and trabecular iris surface area (P < 0.05 for all). Gonioscopically, 44.7% of all subjects had open angles in all 4 quadrants after LPI, with a greater percentage of angles open in the PACS group compared with the PAC/PACG group (52.4% vs. 36.4%; P = 0.01). In multivariable regression analyses, greater postoperative angle widening as defined by change in AOD750 was associated with shorter baseline AOD750 and axial length, and greater baseline anterior chamber depth, iris curvature, and lens vault (P ≤ 0.002 for all). Gonioscopic angle opening after LPI was more common with wider baseline angle width (modified Shaffer grade) and lower cup-to-disc ratio (P < 0.001 for both).

CONCLUSIONS

In a South Indian population with PACS or PAC/PACG, LPI results in significant anterior chamber angle widening seen on both ASOCT and gonioscopy, although some degree of persistent iridotrabecular contact was present in approximately half of PACS eyes and approximately two thirds of PAC/PACG eyes on gonioscopy. The greatest widening by ASOCT was observed in eyes with features most consistent with greater baseline pupillary block.

Determination and Validation of Thresholds of Anterior Chamber Parameters by Dedicated Anterior Segment Optical Coherence Tomography

PURPOSE

To determine and validate thresholds of anterior chamber angle (ACA) parameters in discriminating open- vs narrow-angle eyes using images from dedicated anterior segment optical coherence tomography (DASOCT).

DESIGN

Reliability analysis.

METHODS

Eyes imaged by DASOCT and examined with gonioscopy were reviewed. By gonioscopy, eyes were classified as narrow if posterior trabecular meshwork was not visible and open if the angle was open to scleral spur and beyond. Imaging was performed in the dark with the CASIA SS-1000 (Tomey, Nagoya, Japan). ACA parameters angle opening distance (AOD), trabecular-iris space area (TISA), trabecular-iris circumference volume (TICV), length of iridotrabecular contact (ITC), and extent and area of ITC were calculated. AOD, TISA, and TICV were measured at both 500 μm and 750 μm from the scleral spur landmark. Study eyes were randomly divided into training and testing sets. Thresholds were calculated from the training set. Sensitivity, specificity, and agreement were then calculated against the clinical classification using the testing set.

RESULTS

One hundred and eighty-nine eyes (111 open, 78 narrow, including 8 borderline angles) were included. Using the threshold determined in the training set on the testing set, 9 of 24 ACA parameters had no misclassification of narrow-angle eyes as open (sensitivity = 1.0). Of 9 parameters, the specificity was >0.79. The highest kappa values (kappa = 0.91) was AOD750 inferiorly at 0.31 mm threshold, followed by both TICV500 at 1.92 μL and TICV750 at 4.00 μL with kappa = 0.86.

CONCLUSION

The parameters with the best discriminative ability for detecting narrow angles were AOD750 inferiorly, TICV500, and TICV750.

Changes in Anterior Segment Morphology After Laser Peripheral Iridotomy in Acute Primary Angle Closure

PURPOSE

To evaluate the anterior segment biometric changes measured by anterior segment optical coherence tomography (AS-OCT) in acute primary angle closure (APAC) after laser peripheral iridotomy (LPI).

DESIGN

Prospective interventional study.

METHODS

In this clinic-based study, 52 eyes of 52 patients with resolved APAC attack who underwent LPI were enrolled. Subjects underwent complete ophthalmic examination and AS-OCT imaging before and 6 weeks after LPI. Anterior chamber depth (ACD), anterior chamber area (ACA), iris thickness (IT), iris area, iris curvature, lens vault (LV), anterior vault, angle opening distance (AOD500, AOD750), and trabecular iris space area (TISA500, TISA750) were measured in qualified images and compared before and after LPI. A linear mixed-model analysis was performed for potential predictors of change in AOD750. Main outcome measure was change in AOD750 after LPI.

RESULTS

The mean age of participants was 60.7 ± 9.2 years. Mean angle width (Shaffer grade) changed from 0.25 ± 0.34 at baseline to 1.22 ± 0.86 after LPI (P < .001). However, 25 nasal angles (48.0%) and 28 temporal angles (53%) had iridotrabecular contact after LPI. All angle parameters (AOD500, AOD750, TISA500, TISA750; P ≤ .03), ACD (P = .001), and ACA (P < .001) increased significantly after LPI. Iris curvature and LV were reduced (P = .01 for both) after LPI, but there was no significant change in IT and iris area. After multivariate analysis, pre-LPI AOD750 was the only factor associated with change in AOD750 (β = -0.992, P = .02). Exaggerated LV, defined as LV greater than one-third of the anterior vault (sum of LV and ACD), was present in 61.5% of the cases (32 eyes). The extent of change in angle parameters was not significantly different between groups with and without exaggerated LV after LPI.

CONCLUSION

This study confirms that LPI results in a significant increase in the angle width, ACD, and ACA as well as flattening of the iris in APAC eyes. The extent of angle deepening is inversely related to baseline angle width. The lens shifts posteriorly after resolution of attack, especially in those with greater lens vault.

Anterior segment morphology after acute primary angle closure treatment: a randomised study comparing iridoplasty and medical therapy

PURPOSE

To compare the effect of argon laser peripheral iridoplasty (ALPI) and conventional medical therapy in the immediate treatment of acute primary angle closure (APAC) using anterior segment optical coherence tomography (ASOCT).

METHODS

In this single tertiary centre, prospective comparative study, we randomised 30 consecutive patients with unilateral APAC into two groups: ALPI and medical treatment (n=15 each). Immediately before and 1 h after either intervention, ASOCT imaging was performed. Custom software was used to measure pupil diameter, anterior chamber depth, iris curvature (I-Curv), iris area (I-Area), and the angle opening distance (AOD750), trabecular iris space area (TISA750) and the iris thickness at 750 µm from the scleral spur. The main outcome measure was the change in anterior segment biometrical parameters.

RESULTS

The mean age of the patients was 62.8±7.7 years; 13 (43.3%) were male. APAC eyes treated with ALPI had a larger increase in AOD750 (p=0.002) and TISA750 (p=0.006); a smaller increase in I-Area (p=0.004) and a decrease in I-Curv (p=0.001) after treatment compared with those eyes which received medical therapy. An optimal model consisting of age, gender, pretreatment and post-treatment pupil diameter, treatment modality and pretreatment I-Curv explained 53.2% of the variance in AOD750 change after treatment, with the treatment modality accounting for 35.0% and I-Curv accounting for 12.4% of the variability.

CONCLUSIONS

We observed a greater increase in angle width after ALPI compared with after medical treatment in eyes with APAC. Treatment modality and pretreatment I-Curv were the most significant predictors of angle width change after treatment.

Subsequent Receipt of Interventions for Glaucoma Among a Nationwide Sample of Patients Who Underwent Laser Peripheral Iridotomy

PURPOSE

To evaluate use of medical, laser, or incisional surgical interventions for glaucoma after laser peripheral iridotomy (LPI).

DESIGN

Retrospective longitudinal cohort study.

METHODS

All enrollees aged ≥21 years in a US managed-care network who underwent bilateral LPIs in 2001-2011 were identified. The mean numbers of pre- and post-LPI glaucoma medication classes prescribed and the proportion of enrollees requiring cataract or glaucoma surgery within 2 years after the LPIs were determined. Multivariable logistic regression assessed factors associated with enrollees' prescription of ≥1 glaucoma medication class after bilateral LPIs.

RESULTS

Of the 1660 patients undergoing bilateral LPIs, 1280 (77.1%) had no pre- or post-LPI prescriptions for any glaucoma medication class. Of the remaining patients, 251 (66.1%) required more glaucoma medication classes after than before the procedures, whereas 44 (11.6%) used fewer after the procedures; 85 (22.4%) were prescribed the same number before and after the LPIs. A total of 167 patients (10.1%) underwent cataract surgery and 79 (4.8%) received glaucoma surgery over the 2-year follow-up. Black patients had a 130% increased odds for glaucoma medication-class prescriptions after bilateral LPIs, compared with white patients (P = .02). The odds of post-LPI glaucoma medication use increased by 21% for every additional 5 years of age (P < .0001).

CONCLUSION

Most patients undergoing bilateral LPIs received no pre- or post-LPI glaucoma medication-class prescriptions and had no cataract or additional glaucoma surgery within 2 years after LPIs. Clinicians should alert black or older patients and those already taking glaucoma medications before the procedure of their higher odds of requiring medications afterward.

Guidelines for treatment of chronic primary angle-closure glaucoma

OBJECTIVE

To present a clinical practice guideline update on the medical, laser, and surgical treatment of primary angle closure glaucoma (PACG) in adults.

METHODS

Following the formulation of key questions using the PICO scheme (Patient/Problem, Intervention, Comparison, Outcome), a systematic review was performed on the literature published to date, including international clinical practice guidelines. The AMSTAR and Risk of Bias tools were used for evaluating the quality of the information. The level of evidence and grade of recommendation was established following the Scottish Intercollegiate Guidelines Network (SIGN) system.

RESULTS

Following the above methodology, recommendations of medical, laser and surgical treatment in adult PACG and levels of evidence are presented.

CONCLUSIONS

Although the level of scientific evidence for many of the questions raised is not very high, a review is presented on updated treatment recommendations for adult PACG. Among the limitations for the implementation of these recommendations is that most studies have been conducted in Asian populations, and that the effectiveness is measured almost exclusively in terms of reducing intraocular pressure, and does not include visual function, quality of life or cost-effectiveness parameters.

Association between baseline iris thickness and prophylactic laser peripheral iridotomy outcomes in primary angle-closure suspects

OBJECTIVE

To evaluate the association between baseline measurements of iris thickness at 3 positions and change in anterior segment biometric parameters after prophylactic laser peripheral iridotomy (LPI).

DESIGN

Prospective clinical cohort study.

PARTICIPANTS

Fifty-two eyes of 52 nonglaucomatous subjects with anatomically narrow angles.

METHODS

Anterior segment optical coherence tomography (ASOCT) images captured before and after LPI were analyzed using customized software, the Zhongshan Angle Assessment Program (ZAAP) (Zhongshan Ophthalmic Centre, Guangzhou, China). Differences in preoperative and postoperative measurements for anterior segment biometric parameters were compared by paired Student t tests. Multivariate linear regression models, adjusted for age, sex, ethnicity, and preoperative pupil diameter, were used to examine the association between the baseline measurements of iris thickness at 3 positions and the change in anterior segment biometric parameters after LPI.

MAIN OUTCOME MEASURES

Baseline iris thickness measured at 750 μm from the scleral spur (IT750), iris thickness measured at 2000 μm from the scleral spur (IT2000), and maximal iris thickness (ITM). Changes in iris curvature (ICURV) and trabecular-iris space area at 500 μm from the scleral spur (TISA500) and 750 μm from the scleral spur (TISA750) after LPI.

RESULTS

The ICURV significantly decreased, whereas TISA500 and TISA750 significantly increased after LPI (all P < 0.0001). Lower baseline IT750 was significantly associated with greater postoperative increases in TISA500 and TISA750 (both P < 0.05). Lower baseline IT2000 and ITM were significantly associated with greater postoperative decrease in ICURV (both P < 0.05).

CONCLUSIONS

Our results showed that lower baseline measurements of iris thickness are associated with greater decrease in ICURV and increases in TISA500 and TISA750 after LPI. This suggests that eyes with thinner irides undergoing LPI were more likely to exhibit greater magnitude of change in terms of flattening of the iris convexity (i.e., ICURV) and widening of the anterior chamber angle (i.e., TISA500 and TISA750).

Role of lens vault in subtypes of angle closure in Iranian subjects

PURPOSE

The purpose of this study is to quantify anterior chamber (AC) parameters and to determine the proportion of eyes with exaggerated lens vault (LV) in different subtypes of angle closure disease using anterior segment optical coherence tomography (AS-OCT).

PATIENTS AND METHODS

In this prospective study, 115 eyes of 115 Iranian patients with angle closure disease were included and categorized into three groups: (1) fellow eyes of acute angle closure (AAC; 40 eyes); (2) primary angle closure glaucoma (PACG; 39 eyes); and (3) primary angle closure suspect (PACS; 36 eyes). Complete ophthalmic examination including gonioscopy, A-scan biometry, and AS-OCT were performed. Angle parameters, LV, and iris thickness (IT) were measured using AS-OCT. An exaggerated LV was defined as LV more than one-third the distance between the corneal endothelium and a line drawn to connect the nasal and temporal scleral spurs.

RESULTS

Fellow eyes of AAC had the shallower AC (P=0.01), greater iris curvature (I-curve; P=0.01), and higher LV (P=0.02) as compared with PACS and PACG eyes. There was no statistically significant difference in the mean IT at 750 μm from scleral spur among the three groups (P=0.45). Exaggerated LV was found in 67.5, 35.9, and 40% of fellow eyes of AAC, PACG, and PACS, respectively, (P=0.008) with an odds ratio of 1.92 (P=0.005) for fellow vs PACG and 1.68 (P=0.01) for fellow vs PACS.

CONCLUSIONS

Exaggerated LV is highly prevalent in fellow eyes of AAC. These eyes have shallower AC depth, greater I-curve, and higher LV when compared with PACG and PACS.

Comparison of anterior segment morphology following prophylactic laser peripheral iridotomy in Caucasian and Chinese eyes

BACKGROUND

To compare anterior segment biometric parameters between Caucasians and Chinese before and after laser peripheral iridotomy.

DESIGN

Prospective clinical cohort study.

PARTICIPANTS

Caucasian and Chinese primary angle-closure suspects.

METHODS

Anterior segment optical coherence tomography images captured before and after laser peripheral iridotomy were analysed to measure anterior segment biometric parameters. Paired Student's t-tests were used for within-ethnic group comparisons. Univariate and linear mixed-effect regression models were used for between-ethnic group comparisons.

MAIN OUTCOME MEASURES

Angle opening distance, angle recess area, iris thickness, iris curvature, anterior chamber area, anterior chamber volume and anterior chamber width.

RESULTS

Caucasians had significantly greater preoperative angle recess area, anterior chamber width, and iris curvature and lower preoperative iris thickness compared to Chinese (P < 0.05). Significant postoperative increases in angle opening distance, angle recess area, anterior chamber area, anterior chamber volume, and anterior chamber width along with significant postoperative decrease in iris curvature were observed within both ethnic groups (P < 0.05). However, the amount of laser peripheral iridotomy-induced changes in angle opening distance, angle recess area, anterior chamber area, anterior chamber volume, anterior chamber width, and iris curvature did not differ between the two ethnic groups (P < 0.05).

CONCLUSION

Both Caucasian and Chinese demonstrated opening of anterior chamber angle width, expansion of anterior chamber dimensions, and flattening of iris convexity after laser peripheral iridotomy. Although certain aspects of anterior segment anatomy differed between Caucasians and Chinese preoperatively, they did not translate into significant ethnic differences in the amount of laser peripheral iridotomy-induced changes in the anterior segment biometric parameters.

Association between baseline angle width and induced angle opening following prophylactic laser peripheral iridotomy

PURPOSE

To evaluate the association between baseline angle width and laser peripheral iridotomy (LPI)-induced opening of the anterior chamber angle.

METHODS

Anterior segment optical coherence tomography images captured before and after LPI were analyzed to determine the angle opening distance at 250 μm (AOD250), 500 μm (AOD500), and 750 μm (AOD750) from the scleral spur; trabecular-iris space area at 500 μm (TISA500) and 750 μm (TISA750) from the scleral spur; angle recess area at 750 μm (ARA750) from the scleral spur; and trabecular-iris angle (TIA). Differences in preoperative and postoperative measurements for the anterior chamber angle width parameters were compared by paired Student's t-tests. Univariate and linear mixed-effects regression models were used to examine the association between baseline and LPI-induced opening of anterior chamber angle width parameters.

RESULTS

Eighty-four eyes of 52 primary angle closure suspects were included in the analysis. AOD250, AOD500, AOD750, TISA500, TISA750, ARA750, and TIA significantly increased following LPI by paired Student's t-tests (all P < 0.0001). Lower baseline measurements were significantly associated with greater postoperative opening in all anterior chamber angle width parameters in both univariate and linear mixed-effects regression analyses (all P < 0.05).

CONCLUSIONS

Our results showed significant opening of the anterior chamber angle width after LPI and demonstrated an inverse association between baseline and LPI-induced opening of the anterior chamber angle width, such that eyes with a more crowded anterior chamber angle undergoing LPI had a greater magnitude of increase in anterior chamber angle width after the procedure.