Changes in Iridotrabecular Contact and Intraocular Pressure after Phacoemulsification in Primary Angle-Closure Disease Spectrum

Article information

Korean J Ophthalmol. 2024;38(5):342-353
Publication date (electronic) : 2024 August 16
doi : https://doi.org/10.3341/kjo.2024.0014
Department of Ophthalmology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
Corresponding Author: Kyung Rim Sung, MD, PhD. Department of Ophthalmology, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul 05505, Korea. Tel: 82-2-3010-3680, Fax: 82-2-470-6440, Email: sungeye@gmail.com
Received 2024 February 1; Revised 2024 July 24; Accepted 2024 August 2.

Abstract

Purpose

To compare changes in the swept-source (SS) anterior-segment optical coherence tomography (AS-OCT) parameters and intraocular pressure (IOP) control after lens extraction in various spectra of primary angle-closure disease (PACD).

Methods

A total 92 eyes from 92 patients with PACD who underwent lens extraction were included in the study. All patients underwent IOP measurement preoperatively and at 1 day, 1 week, and 1, 3, and 6 months postoperatively. SS AS-OCT was performed in all subjects preoperatively and 1 month postoperatively. All participants were divided into two groups depending on the presence of glaucomatous optic disc or visual field damage (group A, PAC suspect or PAC; group B, PAC glaucoma). The changes in IOP and anterior chamber angle parameters of SS AS-OCT of each group were compared. Regression analysis was performed to find factors associated with the degree of IOP reduction after lens extraction.

Results

Preoperatively, there was no significant difference in IOP between the two groups (16.3 ± 2.5 mmHg vs. 16.9 ± 3.2 mmHg, p = 0.297), but the number of glaucoma medications used was greater in group B (0.6 ± 1.0 vs. 2.0 ± 0.9, p < 0.001). Postoperatively, IOP was not significantly different, but the number of medications used was greater in group B (0.2 ± 0.7 vs. 0.9 ± 0.8, p < 0.001). Anterior chamber angle parameters including angle opening distance and trabecular-iris angle had a greater increase in group B after lens extraction. However, the residual iridotrabecular contact (ITC) index was significantly greater in group B (5.6 ± 7.0 vs 10.7 ± 12.1, p = 0.014). A greater change in the ITC index was related to a greater degree of IOP reduction (β coefficient, 0.429; p < 0.001).

Conclusions

Eyes with PAC glaucoma had a greater residual ITC index after lens extraction compared with eyes of other PACD spectrum and required a greater number of glaucoma medications to maintain a similar level of IOP.

Glaucoma is a major cause of irreversible blindness worldwide [1,2]. Primary angle-closure glaucoma (PACG) is associated with greater visual morbidity and higher rates of blindness compared with primary open-angle glaucoma, particularly in Asian populations [3,4]. Current definitions of PAC disease (PACD) are based on the presence of iridotrabecular contact (ITC) by gonioscopic examination [5]. PACG, characterized by a glaucomatous optic disc or visual field (VF) impairment along with the presence of ITC, is the most advanced stage of PACD. Furthermore, PACD spectrum includes PAC suspects (PACS) and PAC, which has no glaucomatous structural and/or functional damage [5].

Swept-source (SS) anterior-segment optical coherence tomography (AS-OCT) can evaluate the anterior chamber angle (ACA) configuration and provide quantitative and repeatable parameters including ITC by obtaining cross-sectional imaging of the anterior segment using a noncontact method [6,7].

Although numerous treatment options exist, such as intraocular pressure (IOP)-lowering medications, laser peripheral iridotomy, and argon laser peripheral iridoplasty, lens extraction is regarded as the most definitive treatment modality for resolving angle closure [8,9]. Because PACD is a spectrum of diseases, the characteristics of PACD in terms of angle status or IOP control before and after lens extraction may vary depending on the specific disease of the patient [9,10]. PACG has a tendency to deteriorate rapidly and frequently has a worse response to medical treatment compared with primary open-angle glaucoma; thus, close monitoring of IOP and aggressive management are required [10]. Therefore, we compared the changes in the SS AS-OCT parameters and IOP control after lens extraction in PACD spectrum between eyes with the presence of optic disc/VF damage (i.e., PACG) and those without damage (i.e., PACS + PAC).

Materials and Methods

Ethics statement

This study was approved by the Institutional Review Board of Asan Medical Center (No. 2022-1200), with a waiver of informed consent due to the retrospective nature of the study. The study adhered to the tenets of the Declaration of Helsinki.

Patients

This retrospective, clinical cohort study enrolled consecutive patients who underwent lens extraction by a single surgeon with uneventful phacoemulsification and intraocular lens implantation, from August 2021 to June 2022, among those who were diagnosed with PACD at the glaucoma clinic of the Asan Medical Center (Seoul, Korea). All subjects underwent a complete ophthalmic examination including slit-lamp examination, gonioscopy, fundoscopy, best-corrected visual acuity (BCVA) measurement, Goldmann applanation tonometry, retinal nerve fiber layer photography (Auto Fundus Camera AFC-330, Nidek), stereoscopic optic disc photography (Canon), VF test (Humphrey field analyzer; Swedish Interactive Threshold Algorithm 24-2, Carl Zeiss Meditec), spectral-domain OCT (Cirrus HD-OCT, Carl Zeiss Meditec), axial length measurement (IOLMaster 700, Carl Zeiss Meditec), and SS AS-OCT (CASIA 2, Tomey). Only patients who had completed at least 6 months of follow-up examinations after surgery were included in the analysis. If both eyes were applicable, one eye was chosen randomly and included in the analysis.

Participants were classified according to the following criteria. PACS was classified as eyes with a narrow angle, peripheral angle closure of at least 180° on static gonioscopic examination with normal IOP and absence of optic disc damage or peripheral anterior synechiae (PAS) [11]. Eyes with PAC exhibited occludable angles and gonioscopic evidence of trabecular obstruction by the peripheral iris such as elevated IOP or PAS without glaucomatous VF or optic disc changes [11]. Eyes diagnosed with PACG had anterior chamber features of PAC and were accompanied by glaucomatous optic disc changes (disc excavation, neuroretinal rim thinning, and/or optic disc hemorrhage attributable to glaucoma) and/or VF changes suggestive of glaucoma [11]. All patients were divided into two groups: PACS and PAC patients in group A and PACG patients in group B.

Patients who had a history of laser peripheral iridotomy or argon laser peripheral iridoplasty, topical or systemic medications that could affect the pupillary reflex, or ACA prior to lens extraction were excluded from the study. Those who had lens extraction combined with a glaucoma drainage device or filtering surgery were also excluded from the study. Eyes with secondary causes of angle closure, including uveitic and neovascular glaucoma, were also excluded [5,12].

IOP measurements were taken 2 weeks to 1 month before surgery and at 1 day, 1 week, and 1, 3, and 6 months after the lens extraction. As a representative postoperative IOP value, the IOP measured at 1 month after surgery was analyzed. The degree of IOP reduction after surgery was defined as the percentage difference between preoperative and 1-month postoperative IOP. Postoperative IOP fluctuations were determined as the difference between the highest and lowest IOP values measured during 6 months after surgery.

SS AS-OCT

SS AS-OCT images from all subjects were obtained before and at 1 month after lens extraction. An independent, qualified, single inspector (WKS) assessed all AS-OCT images. Scanned images with good central fixation, great scleral spur resolution, and absence of motion artifacts were chosen for data processing. If the location of the scleral spur was unclear due to PAS or other causes, consultation was conducted with another co-inspector, and only cases where the two inspectors agreed on the location of the scleral spur were included in the analysis. Poor-quality images including cases where the locations of the scleral spur were different between two inspectors, were excluded from the analysis. The examiner evaluated all images blinded to the patients’ clinical information and the results of other examinations.

Four meridional scans cross-sectioned at 0°–180°, 45°– 225°, 90°–270°, and 135°–315° were conducted around the ACA circumference for each eye, and for each scan the parameters specified in the manufacturer’s software were measured [6,7]. These parameters included the mean anterior chamber area, anterior chamber depth (ACD), lens vault, anterior chamber volume, and angle opening distance (AOD) and trabecular-iris space area (TISA) at 500 and 750 μm from the scleral spur. Fig. 1A–1D shows each parameter schematically. The anterior chamber width was measured as the distance between both scleral spurs on either side at each meridional scan. The ITC index and area were defined as the percentage of the circumference and the total area where there was contact between the iris and the inner surface of the cornea in the anterior part of the scleral spur. The ITC index and area were computed using 360° circumferential scans with semiautomated software. To assess the change in the ITC index before and after surgery, the ratio of the decreased ITC index value after surgery to the preoperative ITC index was represented as a percentage. Except for the ITC index and area, representative values of all other preoperative and postoperative ACA parameters were determined by averaging four meridional AS-OCT scans.

Fig. 1

Representative images of swept-source anterior-segment optical coherence tomography (AS-OCT) parameters. (A,B) Angle opening distance 500 (AOD500) refers to the length of a line drawn perpendicular to the iris surface from the corneal endothelial surface 500 μm anterior to the scleral spur (SS). Angle recess area 500 (ARA500) is defined as the triangular area consisting of the line indicating AOD500, the anterior surface of the iris, and the corneal endothelium. Trabecular-iris space area 500 (TISA500) represents the trapezoidal area formed by the two perpendicular lines drawn from SS and the point 500 μm ahead of the SS to the anterior iris surface, the iris surface, and the corneal endothelium. Trabecular-iris angle 500 (TIA500) refers to an angle formed by the apex of the iris recess and lines extending through the corneal endothelium 500 μm anterior to the SS and the perpendicularly opposite point on the iris surface. (C,D) Iridotrabecular contact (ITC) means that there is contact between the iris and the corneal endothelium in front of the SS. Through swept-source AS-OCT, the ITC index can be obtained as a percentage of the area where the ITC is located in the total circumference. S = superior; N = nasal; I = inferior; T = temporal.

Statistical analysis

Statistical analyses were performed using IBM SPSS ver. 23.0 (IBM Corp). Baseline demographics, ocular characteristics, and preoperative and postoperative SS AS-OCT parameters were compared between subgroups in the different spectrum of PACD using either t-test or Mann-Whitney U-test depending on the normality of distribution. Correlations between SS AS-OCT parameters and perioperative IOP reduction (%) were evaluated by univariate and multivariate linear regression analyses. Parameters that showed p < 0.05 in univariate analysis were categorized into preoperative, postoperative, and amount of change values, and multivariate regression analysis was performed for each category.

Results

Baseline demographics and ocular characteristics

Among 101 eyes from 101 patients that met the initial inclusion criteria, nine (8.9%) were excluded from the analysis due to poor SS AS-OCT image quality. Finally, 92 eyes were included in the analysis, of which 50 eyes were in group A (PACS + PAC) and 42 eyes were in group B (PACG).

Table 1 shows the baseline characteristics of the two groups. Group A had significantly longer axial length and fewer numbers of preoperative glaucoma medications than group B. In both groups, the number of glaucoma medications (0.56 ± 1.01 vs. 2.00 ± 0.91, p < 0.001) was reduced to less than half after lens extraction, but group B required more glaucoma medications (0.18 ± 0.66 vs. 0.88 ± 0.80, p < 0.001) and had a lower BCVA than group A. Preoperative and postoperative IOP measurements are shown in Table 2 and Fig. 2. There were no significant differences in IOP measurements at each visit between the two groups, including IOP fluctuation and percentage IOP reduction after lens extraction.

Demographics and clinical characteristics of the two groups in the primary angle-closure disease spectrum (n = 92)

Preoperative and postoperative IOP parameters of two groups in the primary angle-closure disease spectrum (n = 92)

Fig. 2

Preoperative and postoperative intraocular pressure changes of the two groups in the primary angle-closure disease spectrum. Group A, primary angle-closure suspect or primary angle closure. Group B, primary angle-closure glaucoma.

Comparison of SS AS-OCT parameters between two groups

Comparison of the SS AS-OCT parameters and differences in parameters between two groups before and after lens extraction are shown in Table 3. Before lens extraction, the SS AS-OCT parameters were comparable between the two groups, with the exception of anterior chamber width. AOD and trabecular-iris angle at 750 μm were significantly greater in group B at the postoperative assessment, whereas other parameters did not differ significantly. Group B demonstrated a greater change in AOD at 500 and 750 μm and TISA at 750 μm after lens extraction than group A. Table 4 shows changes in ITC-related parameters after lens extraction. The ITC index and area were decreased significantly in both groups after surgery. There was no significant difference between the two groups in preoperative ITC index, area, or location. However, the residual ITC index and area were greater and the degree of postoperative ITC reduction (%) was lower in group B. In terms of location, the ITC index did not differ between the two groups in all four quadrants preoperatively; however, the ITC index was significantly greater in group B in the inferonasal quadrant at the postoperative assessment.

Comparison of swept-source anterior-segment optical coherance tomography parameters between two groups in the primary angle-closure disease spectrum at preoperative, postoperative 1 month, and perioperative differences (n = 92)

Comparison of ITC parameters between two groups in the primary angle-closure disease spectrum at preoperative and postoperative 1 month examinations (n = 92)

Relationship between postoperative IOP reduction and SS AS-OCT parameters

Table 5 shows the results of regression analysis to identify the factors influencing IOP reduction after surgery in PACD. In terms of postoperative IOP change (%) as a dependent variable, multivariate linear regression analysis was performed with statistically significant factors in the univariate analysis. The results showed that the parameters related to the degree of IOP reduction were preoperative IOP, and the amount of ITC index change after surgery, greater preoperative IOP, and ITC index change were associated with a greater degree of IOP reduction overall. A similar trend was seen when analyzed separately into groups A and B. Tables 6 and 7 show the results of the regression analysis of factors affecting the degree of IOP reduction after surgery in groups A and B, respectively. In groups A and B, a smaller postoperative ITC index and larger ITC index change were associated with a greater degree of IOP reduction after surgery.

Univariate and multivariate linear regression analysis of postoperative intraocular pressure decrease using swept-source anterior-segment optical coherence tomography parameters

Univariate and multivariate linear regression analysis of postoperative intraocular pressure decrease using swept-source anterior-segment optical coherence tomography parameters in group A

Univariate and multivariate linear regression analysis of postoperative intraocular pressure decrease using swept-source anterior-segment optical coherence tomography parameters in group B

Discussion

Previous studies have reported that lens extraction in PACD is effective at controlling IOP and subsequently improving the prognosis [1315]. However, other studies have shown that PACG had a worse prognosis than PAC and PACS, even after lens extraction, and preoperative retinal nerve fiber layer thinning and postoperative IOP fluctuation were associated with functional glaucomatous progression after surgery [8,10]. The present study was conducted to analyze and compare the changes in SS AS-OCT and IOP-related parameters before and after lens extraction depending on the presence of glaucomatous function or structural damage within the PACD spectrum and to identify which factors affected the IOP control in each group.

Baseline demographics showed no significant difference in sex, age, and central corneal thickness between the two groups. However, group B had a shorter axial length compared to group A, which was different from a previous study [16]. However, short axial length is a risk factor for angle closure, which may affect the progression of PACS/ PAC to PACG [17]. Before and after lens extraction, group B used a greater number of glaucoma medications. This could be interpreted as being caused by the presence of glaucomatous optic nerve damage in this group. However, in both groups, there was a significant reduction in the number of glaucoma medications after surgery, confirming that lens extraction is an important treatment strategy for resolving angle closure and lowering IOP. Furthermore, there was no significant difference in the IOP before and after surgery between the two groups. This lack of a significant difference may be attributed to the different number of glaucoma medications used in the two groups, with the PACG group using more medications. Consequently, a direct comparison of the IOP between the two groups may be challenging due to this difference in medication usage.

In contrast to the IOP, which can be influenced by glaucoma medications, a quantitative analysis of SS AS-OCT showed meaningful differences between the two groups. Before surgery, angle parameters were not significantly different between the two groups. However, after surgery, AOD and trabecular-iris angle at 750 μm were larger in group B. When comparing the changes after surgery, the differences between the two groups were more pronounced. Although no study has directly compared angle changes before and after cataract surgery between PACD subgroups, a study measuring perioperative ACD changes in PACD suggested that while statistical significance may not be strong, the PACG group tended to have larger ACD changes before and after surgery. Even within the PACG group, those in advanced stages tended to have a wider ACD after cataract surgery [18]. A possible explanation could be that as PACD progress over time, zonules may loosen, causing the intraocular lens to be positioned further posteriorly after surgery, which might lead to a deeper ACD and wider angle in advanced PACD after surgery. To verify this hypothesis, future studies should investigate the position of the intraocular lens.

In this study, we conducted a detailed analysis of the perioperative angle parameters across different PACD spectrum subgroups. After surgery, the anterior angle of PACG eyes became significantly wider, but the residual ITC index and area remained higher, and the ITC reduction percentage was relatively small, compared with group A. In the regression analysis, which identified factors inf luencing the degree of IOP reduction after surgery for each of the two groups, the smaller the residual ITC index after surgery and the larger the change in ITC index after surgery, the lower the IOP after surgery, rather than the other ACA parameters in both groups.

Therefore, in PACD patients, the degree of ITC and residual trabecular function are very important in determining postoperative IOP control. A previous large-scale study revealed that the ITC and IOP had a positive correlation in the range of ITC index over 63% or ITC area exceeding 8.8 mm2 [19]. It was found that the average postoperative ITC index in PACG was 10.68% ± 12.10%. Although this value alone may not lead to significant IOP elevation, considering that the cause of residual ITC is likely synechial closure, it can be assumed that the higher postoperative ITC index in group B ref lects compromised trabecular function compared with group A.

This compromised trabecular function in the PACG group may explain why IOP control remains more challenging after surgery in the PACG group, which has more rapid glaucoma progression than PACS/ PAC af ter phacoemulsification [9]. Therefore, lens extraction of PACS/PAC eyes before the progression to PACG, before synechial closure occurs, is crucial for resolving angle closure and preventing future glaucoma progression.

This study had several limitations. First, due to its retrospective study design, it is challenging to have a uniform indication for lens extraction and criteria for patient inclusion and IOP control. Second, the PAC group only contained 14 individuals, which might be too small to subdivide further according to the definition of the PACD spectrum. Due to the small sample size, we conducted the study by dividing individuals into two groups based on the presence of glaucomatous optic neuropathy or functional damage. Third, the differences in the number of glaucoma medications between the groups made it difficult to directly assess the effect of lens extraction on the IOP in each group. Additionally, we were unable to obtain results matched for the mechanisms of angle closure because of the complicated study design. This should be performed in a future study. Finally, since anterior segment and chamber angle structures are closely located, such parameters driven by AS-OCT are correlated and subsequently our multivariate analysis can be affected by multicoliearity. This should be considered when interpreting the result. Due to these limitations, larger-scale, prospective studies with more standardized criteria for patient inclusion and management to draw more definitive conclusions about the relationship between lens extraction, angle closure, and IOP control in the context of PACD are needed.

In conclusion, the PACS/PAC group did not show a difference in postoperative IOP compared with the PACG group, but there was a clear difference in the number of glaucoma medications used, with more being used in the PACG group. The residual ITC index was higher in the PACG group, which was suspected to be related to synechial closure and compromised trabecular function. Therefore, performing lens extraction at an appropriate time before progressing to chronic angle closure and synechial change, or glaucomatous optic neuropathy, appears to be crucial for long-term prognosis in PACD spectrum.

Acknowledgements

None.

Notes

Conflicts of Interest

None.

Funding

None.

References

1. Flaxman SR, Bourne RR, Resnikoff S, et al. Global causes of blindness and distance vision impairment 1990–2020 a systematic review and meta-analysis. Lancet Glob Health 2017;5:e1221–34.
2. Resnikoff S, Pascolini D, Etya’ale D, et al. Global data on visual impairment in the year 2002. Bull World Health Organ 2004;82:844–51.
3. Cho HK, Kee C. Population-based glaucoma prevalence studies in Asians. Surv Ophthalmol 2014;59:434–47.
4. Rosman M, Aung T, Ang LP, et al. Chronic angle-closure with glaucomatous damage: long-term clinical course in a North American population and comparison with an Asian population. Ophthalmology 2002;109:2227–31.
5. Foster PJ, Buhrmann R, Quigley HA, Johnson GJ. The definition and classification of glaucoma in prevalence surveys. Br J Ophthalmol 2002;86:238–42.
6. Baskaran M, Ho SW, Tun TA, et al. Assessment of circumferential angle-closure by the iris-trabecular contact index with swept-source optical coherence tomography. Ophthalmology 2013;120:2226–31.
7. Ho SW, Baskaran M, Zheng C, et al. Swept source optical coherence tomography measurement of the iris-trabecular contact (ITC) index: a new parameter for angle closure. Graefes Arch Clin Exp Ophthalmol 2013;251:1205–11.
8. Song MK, Sung KR, Shin JW, et al. Glaucomatous progression after lens extraction in primary angle closure disease spectrum. J Glaucoma 2020;29:711–7.
9. Song WK, Sung KR, Kim KE. Assessment of iridotrabecular contact and its association with intraocular pressure after phacoemulsification in primary angle closure. Am J Ophthalmol 2023;249:1–11.
10. Song MK, Shin JW, Sung KR. Factors associated with deterioration of primary angle closure after lens extraction. J Clin Med 2022;11:2557.
11. Moghimi S, Torkashvand A, Mohammadi M, et al. Classification of primary angle closure spectrum with hierarchical cluster analysis. PLoS One 2018;13:e0199157.
12. Prum BE Jr, Herndon LW Jr, Moroi SE, et al. Primary Angle Closure Preferred Practice Pattern(®) Guidelines. Ophthalmology 2016;123:P1–40.
13. Wong SH, Radell JE, Dangda S, et al. The effect of phacoemulsification on intraocular pressure in eyes with preexisting glaucoma drainage implants. Ophthalmol Glaucoma 2021;4:350–7.
14. Ong AY, Ng SM, Vedula SS, Friedman DS. Lens extraction for chronic angle-closure glaucoma. Cochrane Database Syst Rev 2021;3:CD005555.
15. Deng BL, Jiang C, Ma B, et al. Surgical treatment for primary angle closure-glaucoma: a meta analysis. Int J Ophthalmol 2011;4:223–7.
16. George R, Paul PG, Baskaran M, et al. Ocular biometry in occludable angles and angle closure glaucoma: a population based survey. Br J Ophthalmol 2003;87:399–402.
17. Sihota R, Gupta V, Agarwal HC, et al. Comparison of symptomatic and asymptomatic, chronic, primary angle-closure glaucoma, open-angle glaucoma, and controls. J Glaucoma 2000;9:208–13.
18. He Y, Zhang R, Zhang C, et al. Clinical outcome of phacoemulsification combined with intraocular lens implantation for primary angle closure/glaucoma (PAC/ PACG) with cataract. Am J Transl Res 2021;13:13498–507.
19. Porporato N, Chong R, Xu BY, et al. Angle closure extent, anterior segment dimensions and intraocular pressure. Br J Ophthalmol 2023;107:927–34.

Article information Continued

Fig. 1

Representative images of swept-source anterior-segment optical coherence tomography (AS-OCT) parameters. (A,B) Angle opening distance 500 (AOD500) refers to the length of a line drawn perpendicular to the iris surface from the corneal endothelial surface 500 μm anterior to the scleral spur (SS). Angle recess area 500 (ARA500) is defined as the triangular area consisting of the line indicating AOD500, the anterior surface of the iris, and the corneal endothelium. Trabecular-iris space area 500 (TISA500) represents the trapezoidal area formed by the two perpendicular lines drawn from SS and the point 500 μm ahead of the SS to the anterior iris surface, the iris surface, and the corneal endothelium. Trabecular-iris angle 500 (TIA500) refers to an angle formed by the apex of the iris recess and lines extending through the corneal endothelium 500 μm anterior to the SS and the perpendicularly opposite point on the iris surface. (C,D) Iridotrabecular contact (ITC) means that there is contact between the iris and the corneal endothelium in front of the SS. Through swept-source AS-OCT, the ITC index can be obtained as a percentage of the area where the ITC is located in the total circumference. S = superior; N = nasal; I = inferior; T = temporal.

Fig. 2

Preoperative and postoperative intraocular pressure changes of the two groups in the primary angle-closure disease spectrum. Group A, primary angle-closure suspect or primary angle closure. Group B, primary angle-closure glaucoma.

Table 1

Demographics and clinical characteristics of the two groups in the primary angle-closure disease spectrum (n = 92)

Characteristic Group A (n = 50) Group B (n = 42) p-value
Age (yr) 68.14 ± 9.76 68.52 ± 6.08 0.825*
Sex 0.756
 Male 17 (34.0) 13 (31.0)
 Female 33 (66.0) 29 (69.0)
Central corneal thickness (μm) 542.74 ± 33.06 534.31 ± 32.90 0.468
Axial length (mm) 23.15 ± 1.18 22.66 ± 0.93 0.028§
Preoperative measure
 BCVA (logMAR) 0.15 ± 0.16 0.23 ± 0.24 0.103*
 Spherical equivalent (D) 0.28 ± 2.57 0.28 ± 2.04 0.995*
 No. of glaucoma medications 0.56 ± 1.01 2.00 ± 0.91 <0.001*§
Postoperative measure
 BCVA (logMAR) 0.04 ± 0.08 0.08 ± 0.10 0.026*§
 Spherical equivalent (D) −0.32 ± 0.49 −0.46 ± 0.82 0.748
 No. of glaucoma medications 0.18 ± 0.66 0.88 ± 0.80 <0.001*§

Values are presented as mean ± standard deviation or number (%). Group A, primary angle-closure suspect or primary angle closure. Group B, primary angle-closure glaucoma.

BCVA = best-corrected visual acuity; logMAR = logarithm of the minimum angle of resolution; D = diopters.

Statistical analyses were performed using the

*

t-test;

Pearson chi-square test; or

Mann-Whitney U-test, depending on the normality of the distribution;

§

Statistically significant (p < 0.05).

Table 2

Preoperative and postoperative IOP parameters of two groups in the primary angle-closure disease spectrum (n = 92)

Parameter Group A (n = 50) Group B (n = 42) p-value
Preoperative IOP (mmHg) 16.28 ± 2.48 16.91 ± 3.22 0.517
Postoperative IOP (mmHg)
 1 day 15.86 ± 3.43 14.86 ± 3.54 0.147
 1 wk 14.06 ± 2.41 13.88 ± 2.91 0.720
 1 mon 12.76 ± 2.00 12.49 ± 2.24 0.417
 3 mon 12.59 ± 1.98 12.76 ± 2.20 0.732
 6 mon 12.69 ± 1.89 12.64 ± 1.92 0.828
Difference in perioperative IOP 3.52 ± 2.40 4.40 ± 2.63 0.193
IOP reduction (%) 20.73 ± 12.88 25.02 ± 11.70 0.172
IOP fluctuation (mmHg) 3.84 ± 2.59 4.37 ± 2.45 0.285

Values are presented as mean ± standard deviation. Group A, primary angle-closure suspect or primary angle closure. Group B, primary angle-closure glaucoma. Mann-Whitney U-test was used for analysis of all parameters because the normality of distribution for the t-test was not met.

IOP = intraocular pressure.

Table 3

Comparison of swept-source anterior-segment optical coherance tomography parameters between two groups in the primary angle-closure disease spectrum at preoperative, postoperative 1 month, and perioperative differences (n = 92)

Parameter Group A (n = 50) Group B (n = 42) p-value
Preoperative measure
 AOD (mm)
  At 500 μm 0.129 ± 0.079 0.114 ± 0.083 0.257*
  At 750 μm 0.176 ± 0.106 0.166 ± 0.105 0.570
 ARA (mm2)
  At 500 μm 0.057 ± 0.032 0.048 ± 0.031 0.161
  At 750 μm 0.096 ± 0.053 0.084 ± 0.054 0.180
 TISA (mm2)
  At 500 μm 0.053 ± 0.030 0.045 ± 0.031 0.170
  At 750 μm 0.092 ± 0.051 0.081 ± 0.053 0.201
 TIA (°)
  At 500 μm 12.61 ± 7.51 11.69 ± 8.75 0.288
  At 750 μm 12.03 ± 6.71 11.64 ± 7.59 0.461
 ACD (mm) 1.922 ± 0.300 1.808 ± 0.325 0.079
 LV (mm) 0.851 ± 0.328 0.872 ± 0.327 0.796
 ACW (mm) 11.28 ± 0.48 10.92 ± 0.61 0.004
 AA (mm2) 13.26 ± 2.64 12.23 ± 2.56 0.201
Postoperative 1 mon measure
 AOD (mm)
  At 500 μm 0.364 ± 0.113 0.413 ± 0.157 0.089*
  At 750 μm 0.528 ± 0.142 0.607 ± 0.192 0.025*
 ARA (mm2)
 At 500 μm 0.143 ± 0.051 0.153 ± 0.076 0.432*
 At 750 μm 0.255 ± 0.078 0.283 ± 0.117 0.187*
 TISA (mm2)
  At 500 μm 0.131 ± 0.043 0.142 ± 0.062 0.336*
  At 750 μm 0.243 ± 0.070 0.270 ± 0.104 0.138*
 TIA (°)
  At 500 μm 33.35 ± 9.41 36.89 ± 10.42 0.114
  At 750 μm 33.35 ± 8.19 37.53 ± 9.07 0.024
 ACD (mm) 3.176 ± 0.353 3.167 ± 0.422 0.969
 LV (mm) −0.334 ± 0.286 −0.402 ± 0.381 0.308
 ACW (mm) 11.28 ± 0.53 11.02 ± 0.59 0.031
 AA (mm2) 22.44 ± 3.08 22.11 ± 2.89 0.602*
Perioperative difference
 AOD (mm)
  At 500 μm 0.235 ± 0.112 0.298 ± 0.183 0.046*
  At 750 μm 0.352 ± 0.153 0.441 ± 0.220 0.024*
 ARA (mm2)
  At 500 μm 0.086 ± 0.048 0.106 ± 0.086 0.176*
  At 750 μm 0.159 ± 0.076 0.199 ± 0.134 0.081*
 TISA (mm2)
  At 500 μm 0.079 ± 0.039 0.097 ± 0.071 0.125*
  At 750 μm 0.151 ± 0.067 0.189 ± 0.121 0.058*
 TIA (°)
  At 500 μm 20.74 ± 10.47 25.21 ± 13.06 0.113
  At 750 μm 21.32 ± 9.58 25.90 ± 11.22 0.047
 ACD (mm) 1.254 ± 0.423 1.359 ± 0.476 0.184
 LV (mm) −1.185 ± 0.458 −1.274 ± 0.524 0.314
 ACW (mm) 0.005 ± 0.441 0.101 ± 0.567 0.962
 AA (mm2) 9.186 ± 2.972 9.882 ± 3.321 0.240

Values are presented as mean ± standard deviation. Group A, primary angle-closure suspect or primary angle closure. Group B, primary angle-closure glaucoma.

AOD = angle opening distance; ARA = angle recess area; TISA = trabecular-iris space area; TIA = trabecular-iris angle; ACD = anterior chamber depth; LV = lens vault; ACW = anterior chamber width; AA = anterior chamber area.

Statistical analyses were performed using the

*

t-test or

Mann-Whitney U-test; depending on the normality of the distribution;

Statistically significant (p < 0.05).

Table 4

Comparison of ITC parameters between two groups in the primary angle-closure disease spectrum at preoperative and postoperative 1 month examinations (n = 92)

Parameter Group A (n = 50) Group B (n = 42) p-value
Preoperative measure
 ITC index (%) 39.90 ± 21.65 46.54 ± 23.07 0.217*
 ITC area (mm2) 4.489 ± 4.243 5.451 ± 4.880 0.384*
 Quadrant with ITC (%)
  Superotemporal 66.00 ± 47.85 76.19 ± 43.11 0.290
  Superonasal 76.00 ± 43.14 80.95 ± 39.74 0.568*
  Inferotemporal 58.00 ± 49.86 76.19 ± 43.11 0.067
  Inferonasal 78.00 ± 41.85 83.33 ± 37.72 0.523*
Postoperative 1 mon measure
 ITC index (%) 5.64 ± 6.97 10.68 ± 12.10 0.014
 ITC area (mm2) 0.398 ± 0.715 0.745 ± 0.931 0.046
 Quadrant with ITC
  Superotemporal 20.00 ± 40.41 23.81 ± 43.11 0.661*
  Superonasal 16.00 ± 37.03 26.19 ± 44.50 0.234
  Inferotemporal 10.00 ± 30.31 19.05 ± 39.74 0.219
  Inferonasal 6.00 ± 23.99 33.33 ± 47.71 0.001
Change of ITC parameters
 ITC index (%) 34.26 ± 19.53 35.87 ± 24.42 0.727
 ITC area (mm2) 4.786 ± 4.647 5.857 ± 5.994 0.348*
ITC reduction (%) 83.72 ± 19.76 73.90 ± 27.79 0.050

Values are presented as mean ± standard deviation. Group A, primary angle-closure suspect or primary angle closure. Group B, primary angle-closure glaucoma.

ITC = iridotrabecular contact.

Statistical analyses were performed using the

*

Mann-Whitney U-test or

t-test; depending on the normality of the distribution;

Statistically significant (p < 0.05).

Table 5

Univariate and multivariate linear regression analysis of postoperative intraocular pressure decrease using swept-source anterior-segment optical coherence tomography parameters

Parameter Univariate analysis Multivariate analysis


β SE p-value β SE p-value
Preoperative measure
 Intraocular pressure (mmHg) 0.473 0.407 <0.001 0.284 0.478 0.008*
 AOD at 500 μm (mm) −0.374 15.110 <0.001 - - -
 ARA at 500 μm (mm2) −0.429 37.524 <0.001 - - -
 TISA at 500 μm (mm2) −0.408 39.570 <0.001 - - -
 TIA at 500 μm (°) −0.358 0.152 <0.001 - - -
 ITC index (%) 0.523 0.050 <0.001 - - -
 ITC area (mm2) 0.469 0.217 <0.001 - - -
 Anterior chamber volume (mm3) −0.287 0.073 0.012 - - -
 Anterior chamber depth (mm) −0.257 4.031 0.013 - - -
 Anterior chamber area (mm2) −0.262 0.481 0.012 - - -
Postoperative measure (spherical equivalent) 0.232 1.931 0.026 - - -
Perioperative difference
 AOD at 500 μm (mm) 0.232 8.474 0.026 - - -
 ARA at 500 μm (mm2) 0.286 18.455 0.006 - - -
 TISA at 500 μm (mm2) 0.283 22.333 0.006 - - -
 TIA at 500 μm (°) 0.234 0.108 0.025 - - -
 ITC index (%) 0.548 0.050 <0.001 0.429 0.065 <0.001*
 ITC area (mm2) 0.474 0.218 <0.001 - - -
 Anterior chamber depth (mm) 0.220 2.858 0.035 - - -
 Anterior chamber area (mm2) 0.211 0.410 0.044 - - -

Parameters with p < 0.05 in univariate linear regression were divided into preoperative, postoperative, and perioperative difference parameters, and multivariate linear regression analysis was performed for each category.

SE = standard error; AOD = angle opening distance; ARA = angle recess area; TISA = trabecular-iris space area; TIA = trabecular-iris angle; ITC = iridotrabecular contact.

*

Statistically significant (p < 0.05).

Table 6

Univariate and multivariate linear regression analysis of postoperative intraocular pressure decrease using swept-source anterior-segment optical coherence tomography parameters in group A

Parameter Univariate analysis Multivariate analysis


β SE p-value β SE p-value
Preoperative measure - - -
 BCVA (logMAR) −0.324 16.184 0.036
 Iris volume (mm3) 0.626 0.697 <0.001
 Anterior chamber width (mm) 0.340 6.669 0.025
Postoperative measure
 BCVA (logMAR) −0.380 31.992 0.012 - - -
 ITC index (%) −0.727 0.251 <0.001 −0.604* 0.277* <0.001*
 ITC area (mm2) −0.594 3.273 <0.001 - - -
 Anterior chamber volume (mm3) 0.440 0.172 0.012 - - -
 Iris volume (mm3) 0.509 0.805 0.003 - - -
 Anterior chamber depth (mm) 0.510 7.819 <0.001 - - -
 Lens vault (mm) −0.462 9.738 0.002 - - -
 Anterior chamber width (mm) 0.357 8.796 0.019 - - -
 Anterior chamber area (mm2) 0.437 1.142 0.003 - - -
Perioperative difference
 ARA at 500 μm (mm2) 0.304 71.644 0.048 - - -
 TISA at 500 μm (mm2) 0.322 82.976 0.035 - - -
 ITC index (%) 0.534 0.154 <0.001 0.456* 0.163* 0.001*
 Anterior chamber depth (mm) 0.480 6.657 0.001 - - -
 Lens vault (mm) −0.479 6.551 0.001 - - -
 Anterior chamber area (mm2) 0.381 1.002 0.012 - - -

Group A, primary angle-closure suspect or primary angle closure. Parameters with p < 0.05 in univariate linear regression were divided into preoperative, postoperative, and perioperative difference parameters, and multivariate linear regression analysis was performed for each category.

SE = standard error; BCVA = best-corrected visual acuity; logMAR = logarithm of the minimum angle of resolution; ITC = iridotrabecular contact; ARA = angle recess area; TISA = trabecular-iris space area.

*

Statistically significant (p < 0.05).

Table 7

Univariate and multivariate linear regression analysis of postoperative intraocular pressure decrease using swept-source anterior-segment optical coherence tomography parameters in group B

Parameter Univariate analysis Multivariate analysis


β SE p-value β SE p-value
Preoperative measure - - -
 AOD at 500 μm (mm) −0.357 42.183 0.011
 TIA at 500 μm (°) −0.341 0.405 0.015
Postoperative measure
 AOD at 500 μm (mm) 0.369 19.511 0.008 - - -
 ARA at 500 μm (mm2) 0.421 40.543 0.002 - - -
 TISA at 500 μm (mm2) 0.406 49.393 0.003 - - -
 TIA at 500 μm (°) 0.308 0.283 0.029 - - -
 ITC index (%) −0.808 0.225 <0.001 −0.714* 0.185* <0.001*
 ITC area (mm2) −0.760 3.493 <0.001 - - -
 Lens vault (mm) −0.339 10.163 0.016 - - -
 Anterior chamber depth (mm) 0.220 2.858 0.035 - - -
Perioperative difference
 AOD at 500 μm (mm) 0.485 16.643 <0.001 - - -
 ARA at 500 μm (mm2) 0.491 36.366 <0.001 - - -
 TISA at 500 μm (mm2) 0.497 44.025 <0.001 - - -
 TIA at 500 μm (°) 0.458 0.222 0.001 - - -
 ITC index (%) 0.553 0.124 <0.001 0.374* 0.072* <0.001*
 ITC area (mm2) 0.332 0.690 0.018 - - -
 Lens vault (mm) −0.345 6.926 0.014 - - -
 Anterior chamber width (mm) −0.311 5.375 0.028 - - -

Group B, primary angle-closure glaucoma. Parameters with p < 0.05 in univariate linear regression were divided into preoperative, postoperative, and perioperative difference parameters, and multivariate linear regression analysis was performed for each category.

SE = standard error; AOD = angle opening distance; TIA = trabecular-iris angle; ARA = angle recess area; TISA = trabecular-iris space area; ITC = iridotrabecular contact.

*

Statistically significant (p < 0.05).