Evaluation of Schlemm's canal with swept-source optical coherence tomography in primary angle-closure disease.

PURPOSE: To perform an in vivo evaluation of the changes in Schlemm's canal (SC) among patients with primary angle-closure disease (PACD) using swept-source optical coherence tomography (SS-OCT). METHODS: Patients diagnosed with PACD who had not undergone surgery were recruited. The SS-OCT quadrants scanned herein included the nasal and temporal sections at 3 and 9 o'clock, respectively. The diameter and cross-sectional area of the SC were measured. A linear mixed-effects model was performed to analyze the effects of parameters on the SC changes. The hypothesis of interest was related to the angle status (iridotrabecular contact, ITC/open angle, OPN), which was further explored with pairwise comparisons of the estimated marginal means (EMMs) of the SC diameter and SC area. In the ITC regions, the relationship between the trabecular-iris contact length (TICL) percentage and SC parameters was also studied by a mixed model. RESULTS: A total of 49 eyes of 35 patients were included for measurements and analysis. The percentage of observable SCs in the ITC regions was only 58.5% (24/41), whereas it was 86.0% (49/57) in the OPN regions (χ2 = 9.44, p = 0.002). ITC was significantly associated with a decreasing SC size. The EMMs for the diameter and cross-sectional area of SC at the ITC and OPN regions were 203.34 µm versus 261.41 µm (p = 0.006) and 3174.43 µm2 versus 5347.63 µm2 (p = 0.022), respectively. Sex, age, spherical equivalent refraction, intraocular pressure, axial length, extent of angle closure, history of acute attack and treatment with LPI were not significantly associated with SC parameters. In the ITC regions, a larger TICL percentage was significantly associated with a decrease in SC diameter and area (p = 0.003 and 0.019, respectively). CONCLUSIONS: The morphologies of SC could be affected by the angle status (ITC/OPN) in patients with PACD, and ITC was significantly associated with a decreasing SC size. These changes in SC as described by OCT scans might help to elucidate the progression mechanisms of PACD.

Evaluation of biometric indicators of anterior segment parameters after ICL implantation by swept-source optical coherence tomography.

BACKGROUND: To evaluate anterior segment structural alterations after implantable collamer lens (ICL) implantation in myopic patients using swept-source quantitative optical coherence tomography (SS-OCT). METHODS: This prospective study included 47 eyes in 24 patients with preoperative spherical equivalent ≥ -3.00 D. Patients underwent ICL implantation at Department of Ophthalmology, Peking University Third Hospital, from May 2021 to December 2022. SS-OCT was used to measure anterior chamber width (ACW), angle opening distance (AOD), angle recess area (ARA), trabecular-iris area (TISA), trabecular-iris angle (TIA), iridotrabecular contact (ITC) area, and ITC Index before ICL implantation surgery and at 1 month follow-up. The correlations among the ITC index, vault, and angle parameters were analysed. Receiver operating characteristic (ROC) analysis was used to explore the ability of the vault to identify eyes with suspected angle-closure. RESULTS: At one month following ICL implantation, the ITC area was 0.396 ± 0.37 mm2, and the ITC index is 8.143 ± 5.439%. All angle parameters, except ACW, showed a statistically significant reduction on SS-OCT (P < 0.05). Mean AOD500, AOD750, ARA500, ARA750, TISA500, TISA750, TIA500, and TIA750 values at one month postoperatively decreased by 60.0%, 60.4%, 58.1%, 59.2%, 57.3%, 58.7%, 48.8%, and 50.7%, respectively. The vault was positively correlated with the ITC index and percent change in anterior chamber angle parameters. A vault of > 0.659 mm was found to be optimal for angle-closure suspect with a sensitivity of 85.2% and a specificity of 53.9%. CONCLUSIONS: Anterior chamber angle parameters decreased one month after ICL implantation, and their percentage changes and ITC index correlated with the vault. When the vault is larger than 0.659 mm, it is necessary to be alert to possible closed angle suspicion.

Peripheral iris thickness and association with iridotrabecular contact after laser peripheral iridotomy in patients with primary angle-closure and primary angle-closure glaucoma.

PURPOSE: To investigate the relation between the quantitative iris parameters and iridotrabecular contact (ITC) in patients with primary angle-closure (PAC) and PAC glaucoma (PACG). MATERIALS AND METHODS: PAC and PACG with laser peripheral iridotomy were recruited prospectively. Anterior-segment optical coherence tomography (ASOCT) was performed under light and dark conditions, and scans were taken along the vertical and horizontal axes. Iris thickness at 500 µm (IT500) and 750 µm (IT750) from the scleral spur, maximal iris thickness (MIT), and cross sections of the iris area (I-Area) were measured by using software. ITC was defined by the ASOCT as the contact between the peripheral iris and angle wall anterior to the scleral spur. The ITC(+) and ITC(-) groups were defined as eyes that had ITC in two or more quadrants and in no or one quadrant, respectively. RESULTS: A total of 79 eyes of 60 patients (consisting of 48 PAC and 31 PACG) were recruited. The prevalence of superior, inferior, temporal, and nasal ITC was 44 eyes (55.7%), 48 eyes (60.8%), 18 eyes (22.8%), and 16 eyes (20.2%), respectively. These iris parameters of the inferior quadrant, which had the highest prevalence of all the quadrants, were used for the analysis. After adjusting for age, sex, pupil size, and central anterior chamber depth, mean values of IT500 and IT750 were significantly greater in the ITC(+) group than the ITC(-) group (P<0.05). Multivariate-adjusted odds ratios of parameters for the ITC(+) group compared with the ITC(-) group were: IT500, 1.9 (P=0.029); IT750, 2.0 (P=0.011), MIT, 1.4 (P=0.244), and I-Area, 0.97 (P=0.406), respectively, per 0.1-unit increase. CONCLUSION: Peripheral iris thickness is associated with ITC in patients with angle closure.

Iridotrabecular contact observed using anterior segment three-dimensional OCT in eyes with a shallow peripheral anterior chamber.

PURPOSE: To evaluate the prevalence and range of iridotrabecular contact (ITC) in eyes with a shallow peripheral anterior chamber (AC) by using anterior segment swept-source optical coherence tomography (AS-SS-OCT) and to compare the results with those obtained with ultrasound biomicroscopy (UBM) and gonioscopy. METHODS: Forty-three shallow peripheral AC eyes in 43 consecutive patients underwent gonioscopy. Cross-sectional images throughout the angle circumference (i.e., 360°) were obtained with AS-SS-OCT (SS-1000 noncontact, noninvasive three-dimensional imaging system) and those of the peripheral AC at the 3, 6, 9, and 12 o'clock positions were obtained with UBM (UD-1000). RESULTS: ITC evaluated with AS-SS-OCT included all gonioscopically identified peripheral anterior synechia (PAS) in the area. With AS-SS-OCT, at least one ITC was found in 40 (93.0%) and 42 (97.7%) of the 43 eyes under light and dark conditions, respectively, whereas with UBM, at least one ITC was found in 22 (51.1%) and 36 (83.7%) of the 43 eyes under light and dark conditions. The prevalence of ITC in eyes with AS-SS-OCT was significantly higher than that with UBM under light conditions, but not under dark conditions (P = 0.0001, 0.07, respectively, sign test). The PAS-positive eyes had a significantly greater ITC range than the PAS-negative eyes under light conditions (P = 0.006), but not under dark conditions (P = 0.08). CONCLUSIONS: AS-SS-OCT detected all PAS and the prevalence of ITC detected by AS-SS-OCT in narrow angle eyes was markedly higher than previously thought. A relationship between the ITC range under light conditions and future PAS formation was suggested.

[Screening method for angle closure and angle closure glaucoma using scanning laser polarimeter GDxVCC and photodynamic gonioscopy in a darkened room. One-year outcomes of systematic peripheral iridotomy]. / Méthode de dépistage du glaucome chronique par fermeture de l'angle basée sur l'utilisation systématique du GDxVCC et de la gonioscopie photodynamique. Résultats à un an d'une iridotomie systématique.

INTRODUCTION: Angle closure glaucoma, a recognized major world health issue disproportionately affecting women and Asians, is not often considered in our European populations, normotensive subjects, myopic patients, or subjects with a deep anterior chamber. Early diagnosis is worthwhile, as laser peripheral iridotomy (LPI) is an effective one-step treatment of the causal mechanism. PATIENTS AND METHODS: We have performed a retrospective study of patients who underwent an LPI, the indication for which was based on "photodynamic" gonioscopy in a darkened room showing iridotrabecular contact in darkness. Such photodynamic gonioscopy was motivated by the presence of even minute defects in the nerve fiber layer as seen on the GDxVCC or the presence of a Van Herick sign (narrow limbal anterior chamber depth). RESULTS: One hundred and three eyes of 103 patients underwent LPI and a minimum 1-year follow-up (mean follow-up almost 2 years). Mean age was 63.7±11.8 years, and women accounted for 63.1% of cases. The vast majority (78.6%) of patients had neither glaucoma nor ocular hypertension. There were 60.1% hyperopes and 39.9% myopes. Over half (57%) had a deep or a very deep anterior chamber. After LPI, there was immediate deepening of the limbal depth of the anterior chamber in 100% of cases. The aqueous humor that flowed forward was almost always viscous-looking. After 1 year, the IOP was 1.3mm Hg±2.4 lower (P<.001) (t test). All patients who had experienced morning headaches (44% of patients) were relieved of this symptom. GDxVCC after 1 year was clearly improved in 18% of cases, slightly improved in 20%, stable in 50%, slightly worse in 11% of cases, and clearly worse in 1%. Cases treated at an earlier stage had a better improvement in GDxVCC. DISCUSSION: Our study shows frequent chronic angle closure in our European population even with deep anterior chambers. Absence of a Van Herick sign does not rule out angle closure at night. A photodynamic gonioscopy with the Goldmann three-lens mirror (to avoid unintentional indentation with the small diameter lenses in these normotensive eyes) should be performed in a darkened room. LPI is an effective one-step treatment of the underlying cause, that is particularly beneficial if performed early.

Determination of iridotrabecular contact using the anterior segment optical coherence tomography in lights-on and lights-off conditions

Objective@#To determine the presence of iridotrabecular contact (ITC) and compare the changes in anterior chamber angle (ACA) measurements in room lights-on and lights-off conditions using the anterior segment optical coherence tomography (AS-OCT) in eyes diagnosed as primary angle closure suspects (PACS) by gonioscopy.@*Methods@#This is a retrospective review of 144 eyes of 79 patients (70 females, 9 males) with PACS. All eyes were imaged using the Visante® time-domain AS-OCT (Carl Zeiss Meditec, Dublin, CA). Each eye was imaged twice; the first scan was done with the room lights on followed by a second scan done after turning the room lights off for 2 minutes. The principal outcome measure was the presence of ITC in either lighting condition. Other angle metrics that were assessed included anterior chamber depth (ACD), angle opening distance (AOD), trabecular-iris space area (TISA), and scleral spur angle (SSA). Presence of ITC and differences in the angle metrics between the 2 lighting conditions were then analyzed using the t-tests and logistic regression.@*Results@# ITC was present in 36.8% (53) of the study eyes. Twenty percent (20%) of the study eyes (29) did not initially exhibit ITC in the lights-on phase but developed ITC when imaged with the lights off. Persistent ITC was seen in 16.6% (24 eyes) in both lighting conditions. ITC occurred in 52.2% of the eyes with ACD less than 2.18 mm. Logistic regression showed that there is a 91% decrease in the odds of having ITC in lights-off condition for every millimeter of ACD increase. Age was not associated with the occurrence of ITC in the lights-off condition. All other analyzed parameters decreased significantly in the lights-off condition (p<0.05) except for the ACD, nasal TISA-500, and temporal SSA.@*Conclusions@#The presence of ITC is a well-established characteristic of eyes with angle closure. In eyes with PACS, detection of ITC may be enhanced with AS-OCT imaging in lights-off condition.