Anterior Chamber Angle and Anterior Chamber Volume in a 40- to 64-Year-Old Population

Distribution and Determinants of Anterior Chamber Angle and Anterior Chamber Volume in Young Chinese Adults

PURPOSE

Current study aimed to understand the distribution and determinants of anterior chamber angle (ACA) and anterior chamber volume (ACV) in Chinese young adults, which can help fill current data gaps and aid in early detection and intervention for high-risk population of primary angle closure glaucoma.

METHODS

This cross-sectional study utilized data from 2014 participants who completed questionnaire and eye examination in September 2021. ACV and ACA were measured using a Pentacam tomographer. Spherical equivalent (SE) was evaluated by autorefractor without cycloplegia. Central corneal thickness (CCT) and biomechanically corrected intraocular pressure (bIOP) were evaluated using Corvis-ST. Axial length (AL), corneal radius (CR), anterior chamber depth (ACD), and white to white were assessed using the IOL Master.

RESULTS

A total of 1635 students were included in the analysis. The mean ACV and AVA were 194.74 ± 32.30 μL and 38.81 ± 4.84°, respectively. Males have a larger ACV and wider ACA than females. ACV was positively correlated with ACA (r = 0.24, p < 0.001), and the correlation was stronger for non-myopic students than for myopic students. Multivariable linear regression model showed that AL (β = 2.41), CR (β = -4.12), CCT (β = -0.11), ACD (β = 97.93), and bIOP (β = 0.40) were associated with ACV, and CCT (β = -0.01), CR (β = 0.38), and ACD (β = 7.41) were associated with ACA (all p < 0.05). Random forest model indicated that ACD was the most critical predictor of both ACV and ACA.

CONCLUSIONS

This study reported the distribution and determinants of ACA and ACV. Deeper ACD was associated with larger ACV and wider ACA.

Correlations of Corneal Endothelial Morphology and Corneal Thickness With Anterior Segment Parameters in Healthy Individuals

PURPOSE

The purpose of this study was to investigate the associations between central corneal endothelial cell density (ECD), endothelial morphology, and corneal thickness (central corneal thickness) with the anterior chamber depth, corneal volume (CV), white-to-white (WTW) distance, mean anterior chamber angle (CAmean), and gender in healthy individuals.

METHODS

This observational study included 136 healthy volunteers. The ECD, coefficient of variation of cell area, and hexagonal cell appearance ratio (%Hex) were measured by means of specular microscopy. The central corneal thickness, anterior chamber depth, CV, WTW distance, and the angle width of 12 points were taken by the Pentacam HR Scheimpflug anterior segment imaging. The arithmetical mean of the 12 points was considered as the CAmean. We used mixed effect linear regression model for the statistical analysis of the data.

RESULTS

ECD was positively correlated with CV ( P = 0.028), while after adjusting for age, it was negatively correlated with age ( P < 0.001). Coefficient of variation of cell area was positively correlated with CAmean ( P = 0.036), while after adjusting for age, it was positively correlated with age ( P < 0.001) and CAmean ( P = 0.005). Hex was negatively correlated with WTW ( P = 0.023) and CAmean ( P = 0.025), and after adjusting for age, this correlation remained the same ( P = 0.029 when correlated with WTW and P = 0.035 with CAmean).

CONCLUSIONS

There were significant changes in the morphology of the corneal endothelial cells in eyes with wider anterior chamber angle. Greater pleomorphism and polymegethism of the corneal endothelium was observed in healthy patients with wider CAmean. Deepening of the anterior chamber as myopia progresses could render the corneal endothelium more fragile and susceptible to mechanical stress, which is an area worthy of further study.

Associations between corneal curvature and other anterior segment biometrics in young myopic adults

To investigate the associations between corneal curvature (CC) and other anterior segment biometrics in young myopic adults. In this retrospective multi-center study, 7893 young myopic adults were included. CC and other anterior segment biometrics were measured by Scheimpflug imaging (Pentacam). CC was defined as SimK at central 3 mm area, and other anterior segment biometrics included white-to-white corneal diameter (WTW), central corneal thickness (CCT), corneal volume (CV) at 3 mm, 5 mm, and 7 mm area, anterior corneal astigmatism (ACA), posterior corneal astigmatism (PCA), anterior corneal eccentricity (ACE) and asphericity (ACAP), posterior corneal eccentricity (PCE) and asphericity (PCAP), anterior chamber depth (ACD), and anterior chamber volume (ACV). Univariate regression analyses were used to assess the associations between CC and other anterior segment biometrics, and multivariate regression analyses were further performed to adjusted for age, gender and spherical equivalent. CC was higher in patients of female gender and higher myopia (all P < 0.05). Eyes in higher CC quartiles had lower WTW, thinner CCT, lower CV at 3 mm and 5 mm, lower ACD, and lower ACV (all P < 0.001), but had larger ACA, larger PCA, less PCE and less PCAP (all P < 0.001), compared to eyes in lower CC quartiles. The trends of CV at 7 mm, ACE and ACAP were inconsistent in different CC quartiles. After adjusting for age, gender and spherical equivalent with multivariate linear regression, CC was positively correlated to CV at 7 mm (βs = 0.069), ACA (βs = 0.194), PCA (βs = 0.187), ACE (βs = 0.072), PCAP (βs = 0.087), and ACD (βs = 0.027) (all P < 0.05), but was negatively correlated to WTW (βs = - 0.432), CCT (βs = - 0.087), CV-3 mm (βs = - 0.066), ACAP (βs = - 0.043), PCE (βs = - 0.062), and ACV (βs = - 0.188) (all P < 0.05). CC was associated with most of the other anterior segment biometrics in young myopic adults. These associations are important for better understanding of the interactions between different anterior segment structures in young myopic patients, and are also useful for the exploration of the pathogenesis of myopia.

Correlations of Corneal Curvature with Corneal Spherical Aberration and Anterior Chamber Parameters in Eyes with Shallow Anterior Chambers

INTRODUCTION

This study aimed to investigate the distribution of corneal spherical aberration (CSA) and the relationship between corneal curvature with CSA and anterior chamber parameters in age-related cataract patients with normal axial lengths and shallow anterior chambers.

METHODS

Preoperative data of age-related cataract patients were collected in this retrospective comparative study. According to the average corneal curvature, the eyes were divided into groups of K_m < 42 diopters (D), 42 D ≤ K_m < 45 D, and K_m ≥ 45 D. The axial length (AL) and corneal curvature were obtained using IOLMaster. CSA, anterior chamber depth (ACD), anterior chamber volume (ACV), anterior chamber angle (ACA), and corneal diameter (CD) were acquired according to Pentacam. The above parameters were compared among the three groups. Correlation analysis was applied to these parameters.

RESULTS

The average CSA value of 753 eyes was 0.41 ± 0.27 μm, with no significant difference among the three groups. Overall, CSA was significantly correlated with corneal curvature and ACD. The comparison of ACD among the three groups showed significant differences between the K_m ≥ 45 D group, K_m < 42 D group, and 42 D ≤ K_m < 45 D group. Corneal curvature was positively correlated with ACD, and further analysis confirmed that the relationship was significant only in the K_m ≥ 45 D group. There were statistically significant differences in CD between the three groups. A significant correlation was found in corneal curvature and CD in all eyes, which was also found in the 42 D ≤ K_m < 45 D group and the K_m ≥ 45 D group. Concerning ACV and ACA, no correlation with corneal curvature was found. In addition, the mean ACV and ACA of the three groups did not show any significant difference.

CONCLUSIONS

CSA was higher in this population and had individual variance. Compared with ACD, ACV and ACA were more stable in different corneal curvatures and more objective in representing the anterior chamber space.

Anterior chamber parameters in cataract surgery candidates from middle China

To determine the distribution of the anterior chamber parameters and associated factors in cataractous adults from middle China. In this cross-sectional study, axial length, anterior chamber depth (ACD) and lens thickness (LT) were measured with IOLMaster 700. The Pentacam HR was designed to measure the anterior chamber volume (ACV) and anterior chamber angle (ACA). Patients' data were collected and analyzed between 2020 and 2022. A total of 157 eyes of 157 Chinese adults (mean age: 64.43 ± 12.16 years) with a cataract were enrolled in this study. The mean values measured were as follows: axial length, 24.10 ± 2.44mm; ACD, 2.99 ± 0.52 mm; LT, 4.51 ± 0.48 mm; ACV, 113.98 ± 45.12 mm3; ACA, 32.33 ± 7.66 degrees. The ACD and ACV were statistically significantly greater in men than in women and had a decrease trend as age and LT increased. In the simulated linear equation of age with ACD and LT the absolute slope coefficients of equations were the same; however, the directions were opposite. The mean ACV was <100 mm3 when the patients were over 60 years. In the multivariate regression analysis of ACD, ACV and ACA there was a reasonable prediction with adjusted R2 = 0.878, 0.847 and 0.564, respectively. This study may provide normative data for cataract patients. The profile of anterior chamber can help improve the knowledge of the risk of angle closure in cataract candidates.

Long-acting ocular drug delivery technologies with clinical precedent

INTRODUCTION

Ocular long-acting injectables and implants (LAIIs) deliver drug at a controlled release rate over weeks to years. A reduced dose frequency eases the treatment burden on patients, minimizes the potential for treatment-related adverse effects, and improves treatment adherence and persistence.

AREAS COVERED

This review provides a comprehensive landscape of ocular LAII drug delivery technologies with clinical precedent, including eight commercial products and 27 clinical programs. Analysis of this landscape, and the specific technologies with the greatest precedent, provides instructive lessons for researchers interested in this space and insights into the direction of the field.

EXPERT OPINION

Further technological advancement is required to create biodegradable LAIIs with extended release durations and LAIIs that are compatible with a broader array of therapeutic modalities. In the future, ocular LAII innovations can be applied to diseases with limited treatment options, prophylactic treatment at earlier stages of disease, and cost-effective treatment of ocular diseases in global health settings.

Anterior chamber depth measurement using Pentacam and Biograph in children

CLINICAL RELEVANCE

Accurate measurement of the anterior chamber depth is very important. There is no report regarding the agreement between rotating Scheimpflug imaging (Pentacam HR) and biograph (Lenstar LS 900) in children. This study therefore explores the agreement between Pentacam and Biograph in measuring anterior chamber depth in children.

BACKGROUND

This study aims to determine the agreement between Pentacam and Biograph in measuring anterior chamber depth in children.

METHODS

The participants were students living in urban and rural areas of Shahroud, Iran, selected through cluster sampling. The students were transported to the examination site to undergo imaging and optometric tests. Pentacam imaging was then conducted, and biograph was used to measure biometric components. In this report, the anterior chamber depth was calculated from the corneal endothelium.

RESULTS

Of 6624 students selected randomly, 5620 participated in the study. After applying the exclusion criteria, 4882 eyes were included in the final analysis. The mean anterior chamber depth measured by the Pentacam (3.09 ± 0.26 mm) was higher than that of biograph (3.04 ± 0.24 mm) (p < 0.001). The 95% limit of agreement (LOA) between the two devices was -0.19 to 0.09 mm. The variation of the difference between the two devices decreased, LOA became narrower, and the correlation coefficient of the devices increased with ageing. The highest intraclass correlation coefficient was seen among myopic (0.974) participants. The 95% LOA was -0.20 to 0.12 mm in hyperopic, -0.17 to 0.07 mm in myopic and -0.19 to 0.09 mm in emmetropic participants.

CONCLUSION

The Pentacam and Biograph can be used interchangeably for measuring the anterior chamber depth in children.

Anterior chamber dimensions, angles and pupil diameter in patients with Down syndrome: A comparative population-based study

Purpose

To study the anterior chamber (AC) dimensions, angles and pupil diameter (PD) in patients with Down syndrome compared to normal controls.

Methods

Prospective study is comparing the AC parameters in patients with Down syndrome aged 10-30 years and age-matched controls. Extracted indices included average anterior chamber depth on the 2-mm ring (ACD-2 mm), 4-mm ring (ACD-4 mm), at the corneal apex from the endothelium (endo-ACD), at the corneal apex from the epithelium (epi-ACD), anterior chamber volume (ACV), mean anterior chamber angle (ACA), and PD measured by Pentacam.

Results

Data from 202 patients with Down syndrome (age 17.2 ± 4.8 years) were compared with 190 normal controls (age 17.2 ± 4.5 years). In Down and normal groups, mean ± SD were 2.51 ± 0.31 and 2.83 ± 0.34 mm for ACD-2 mm, 1.65 ± 0.30 and 1.93 ± 0.31 mm for ACD-4 mm, and 3.03 ± 0.29 and 3.24 ± 0.26 mm for endo-ACD, 3.54 ± 0.29 and 3.80 ± 0.26 mm for epi-ACD, mean 169.31 ± 30.38 and 200.17 ± 33.20 mm³ for ACV, 40.69 ± 4.50 and 39.97 ± 4.12° for ACA, and 2.79 ± 0.62 and 3.59 ± 0.80 mm for PD, respectively (all P < 0.001). None of the studied indices significantly correlated with age, except for ACA (P = 0.011). All parameters, except for PD, were significantly higher in males compared to females (all P < 0.001). Temporal ACA was significantly wider in male subjects (44.61 ± 6.52 vs. 42.24 ± 6.52°; P < 0.001).

Conclusion

The AC in patients with Down syndrome is smaller than normal individuals. AC in females with Down syndrome is smaller than males, and the narrower ACA is attributable to the difference in the temporal angle and not the ACA in other meridians.

Correlation Between Anterior Chamber Volume and Corneal Biomechanical Properties in Human Eyes

Purpose: To investigate the correlation between anterior chamber volume (ACV) and corneal biomechanical properties in healthy and primary angle closure (PAC) eyes.

Methods: A total of 79 eyes from 55 participants were enrolled in this study, including 24 eyes from 17 PAC patients and 55 eyes from 38 normal subjects. Anterior chamber volume was detected via swept-source anterior segment optical coherence tomography (OCT), and the cornea biomechanical data were obtained via corneal visualization Scheimpflug technology (Corvis ST). A student's t-test, Chi-square test, Pearson's correlation coefficients, and linear regression were used in the statistical analysis.

Results: Anterior chamber volume was significantly associated with a lower deformation altitude (DA) (p = 0.033), higher stiffness parameter (SP-A1) (p = 0.005), younger age (p = 0.001), and higher biomechanical intraocular pressure (bIOP) (p = 0.001). PAC patients were suspected to have a much shallower anterior chamber than healthy participants. In the PAC group, the mean ACV (p < 0.01), SP-A1 (p < 0.01), and bIOP values (p = 0.01) were significantly reduced as compared to the normal group, and DA values (p = 0.02) and age (p = 0.01) were increased as compared to the normal group.

Conclusions: Bigger ACV was associated with lower DA values and age, as well as higher SP-A1 and bIOP values. Reduced corneal stiffness was more commonly found in the PAC suspects as compared to their normal counterparts, indicating a protective physiological mechanism for people with shallower anterior chambers that protects against potential elevations of IOP.

Distribution of Anterior Chamber Parameters in Normal Chinese Children and the Associated Factors

PURPOSE

To describe the distribution of anterior chamber depth (ACD), anterior chamber volume (ACV), and anterior chamber angle (ACA) and establish the associated factors in the pediatric population in Shanghai, China.

MATERIALS AND METHODS

In this cross-sectional study, children aged 6 to 18 years from 9 primary and middle schools in Shanghai were enrolled. The Pentacam Scheimpflug camera was used to measure anterior eye chamber parameters. The distribution of ACD, ACV, ACA, and their associations with age, sex, body mass index, cycloplegic refractive error, axial length, intraocular pressure, and other parameters were analyzed.

RESULTS

A total of 1321 children were included, with a mean age of 9.65±2.95 years. The mean ACA, ACD, and ACV values were 37.95±7.96 degrees, 3.22±0.23 mm and 194.89±28.95 mm, respectively, and were higher in boys than in girls. ACV and ACD had similar growth trend curves with age, whereas ACA was stable. Overall, 5% of the tested children had ACA values ≤24.91 degrees. Greater ACV, deeper ACD, shorter pupil diameter, shorter axial length, and thinner apex corneal thickness were the independent factors associated with wider ACA (R=13.0%, P<0.001).

CONCLUSIONS

As one of diagnostic indicators of angle closure, ACA was stable with age. The results of this study should improve the current understanding of the distribution of anterior chamber parameters and the main factors affecting their variation.

Anterior Chamber Angle, Volume, and Depth in a Normative Cohort-A Retrospective Cross-Sectional Study

Purpose: The purpose of the study was to determine the distribution of the anterior chamber angle (ACA) within a population-based study sample in Germany and to find correlations between age, sphere, and biometric parameters of the anterior chamber. Patients and Methods: A total of 500 eyes, approximately 100 eyes per decade starting with patient age of 20 years, of 463 patients with an average age of 45.2 ± 14.1 (±values subsequent represent standard deviation) years without any known history of ocular diseases, surgery, or optic nerve head excavation or hypoplasia were included. ACAs, volume, and depth were correlated to age and sphere. Scheimpflug images (Pentacam, Oculus) with automatically measured ACAs were compared to manually measured angles (Bland Altman analysis) in this healthy population. Results: The mean manually measured ACA was 26.5° ± 3.9°; the highest average angle was found in the temporal position with 28.1° ± 4.9°, while the lowest average angle was found in nasal superior position with 25.7° ± 4.7°. Statistical analysis showed an average difference of +11.4° nasal and +12.1° temporal between the automatic measurements and the manually measured angles (P < 0.01). The analysis also revealed an independent inverted correlation between age (correlation coefficient between -0.28 and -0.38) and sphere (correlation coefficient between -0.44 and -0.51) of the participants and the anterior chamber volume, angle, and anterior chamber depth (P < 0.01 for all correlations). Conclusion: The ACA width manually measured is considerably less compared to automated imaging and formerly reported values. There is a significant difference in the ACA dependent on the position of measurement (superior, nasal, inferior, and temporal) with the average angle being inversely correlated to age and sphere. Abbreviations: AC: anterior chamber ACA: anterior chamber angle ACV: anterior chamber volume ACD: anterior chamber depth AAC: acute angle closure OAG: open-angle glaucoma OCT: optical coherence tomography ACG: angle-closure glaucoma MIGS: microinvasive glaucoma surgery PACS: primary angle-closure suspects.

Anterior chamber indices in a population-based study using the Pentacam

PURPOSE

To determine the distribution of anterior chamber depth (ACD), anterior chamber volume (ACV), and anterior chamber angle (ACA) values in a rural population over 5 years of age using the Pentacam.

METHODS

In this cross-sectional study, samples were selected from over 1-year-old inhabitants of two villages in Iran using a multistage cluster sampling approach. All participants underwent the measurement of uncorrected and corrected visual acuity and auto-refraction, retinoscopy, subjective refraction, and slit lamp examination. Finally, corneal imaging was done for all subjects over 5 years of age using the Pentacam.

RESULTS

Of 3851 selected individuals, 3314 participated in the study, of whom 2681 met the inclusion criteria. The mean age of the sample was 36.03 ± 18.5 years (range 6-90 years). The mean ACD, ACA, and ACV values were 3.37 mm (95% CI: 3.37-3.39), 34.82° (95% CI: 34.45-35.2), and 159.17 µL (95% CI: 156-161.36), respectively. The results of multiple linear regression models showed that ACD, ACA, and ACV values reduced with age, and ACD and ACV values were significantly higher in males. ACA and ACV values correlated inversely with central corneal thickness, while the ACA value correlated directly with keratometry and inversely with the ACV value.

CONCLUSION

This study is one of the few studies in the world showing changes in ACD values in different age groups using the Pentacam. According to the results, aging was associated with a decline in the mean ACD, ACA, and ACV values. These parameters were the largest in patients with emmetropia and smallest in hyperopic subjects.

Steeper Iris Conicity Is Related to a Shallower Anterior Chamber: The Gutenberg Health Study

PURPOSE

To report the distribution of iris conicity (steepness of the iris cone), investigate associated factors, and test whether pseudophakia allows the iris to sink back.

METHODS

A population-based cross-sectional study was carried out. Ophthalmological examination including objective refraction, biometry, noncontact tonometry, and Scheimpflug imaging (Pentacam®, Oculus) was performed including automated measurement of iris conicity. 3708 phakic subjects, 144 subjects with bilateral and 39 subjects with unilateral pseudophakia were included. Multivariable analyses were carried out to determine independently associated systemic and ocular factors for iris conicity in phakic eyes.

RESULTS

Mean iris conicity was 8.28° ± 3.29° (right eyes). Statistical analysis revealed associations between steeper iris conicity and shallower anterior chamber depth, thicker human lens and higher corneal power in multivariable analysis, while older age was related to a flatter iris conicity. Refraction, axial length, central corneal thickness, pupil diameter, and intraocular pressure were not associated with iris conicity. Pseudophakia resulted in a 5.82° flatter iris conicity than in the fellow phakic eyes.

CONCLUSIONS

Associations indicate a correlation between iris conicity with risk factors for angle-closure, namely, shallower anterior chamber depth and thicker human lens. In pseudophakic eyes, iris conicity is significantly lower, indicating that cataract surgery flattens the iris.

Measurement of and Factors Associated with the Anterior Chamber Volume in Healthy Chinese Adults

Purpose. To measure the anterior chamber volume (ACV) and determine factors associated with the ACV in healthy Chinese adults. Methods. In this cross-sectional study, we used swept-source optical coherence tomography (SS-OCT) to measure ACV and other anterior segment parameters. Factors associated with ACV were also determined. Results. A total of 313 healthy Chinese adults were enrolled. The anterior segment parameters, including ACV, could be measured by SS-OCT with excellent repeatability and reproducibility. There was a significant difference between the horizontal and vertical anterior chamber widths (ACW) (P < 0.05), with a mean difference of 390 μm. The ACV (mean 153.83 ± 32.42 mm³) was correlated with most of the anterior segment parameters, especially anterior chamber depth (ACD), which accounted for about 85% of the variation of ACV. Most of the anterior segment parameters were significantly correlated with age, and the relative changes in ACV and ACD were greatest in subjects aged 41–50 years. Conclusion. ACV was correlated with most of the anterior segment parameters measured in this study, particularly ACD. The relatively large difference between horizontal and vertical ACW suggests that the ACV could and should be measured using multiple OCT scans.