Ultrasound biomicroscopic study of ciliary body thickness in eyes with narrow angles

Thinning of maximum ciliary body thickness: a potential early indicator for pseudophakic malignant glaucoma in primary angle closure glaucoma

OBJECTIVE

Pseudophakic malignant glaucoma (PMG) is an uncommon but severe postoperative complication that poses a significant threat to vision. Early detection of PMG in patients with primary angle closure glaucoma (PACG) is imperative for effective intervention. This study sought to determine whether specific morphometric indicators could predict the onset of PMG.

METHODS

A retrospective cross-sectional analysis was performed on data collected from June 2016 to May 2023. The study population comprised PACG patients who developed PMG after phacoemulsification, with a control group of eyes that did not. Ultrasound biomicroscopy (UBM) was employed to measure the central anterior chamber depth (ACD), trabecular-ciliary process angle (TCA), and ciliary body thickness at multiple points (CBTmax, CBT0, CBT1000), as well as the anterior placement of the ciliary body (APCB). These measurements were taken at three distinct phases: pre-onset, onset, and 6 months following PMG resolution.

RESULTS

The study encompassed 60 eyes from 60 patients, with baseline characteristics showing no significant differences between the groups. Following lens extraction, a notable increase in CBTmax, CBT0, and TCA was observed in matched eyes, but not detected in those that developed PMG. At pre-onset of PMG, a significant reduction in CBTmax was identified exclusively in eyes that later exhibited PMG (0.87 ± 0.09 mm vs. 0.95 ± 0.09 mm, P = 0.001), when compared to the matched eyes. The resolution of PMG through zonulo-hyaloido-vitrectomy was associated with an increase in ACD, CBTmax, CBT0, and TCA. Notably, the pre-onset CBTmax was the sole parameter to exhibit significant prognostic value for PMG development (0.74 [95% CI, 0.61-0.87], P = 0.001), nearly matching the predictive accuracy during PMG attack (0.86 [95% CI, 0.76-0.96], P < 0.001).

CONCLUSION

A reduction in ciliary body thickness, particularly CBTmax, appears to be a pre-existing condition in eyes that develop PMG from PACG. This parameter holds promise as a sensitive early predictor, potentially improving the timeliness of PMG diagnosis and treatment.

Risk factors of angle opening after lens extraction in patients with shallow peripheral anterior chamber

PURPOSE

To predict the degree of angle opening after lens extraction (LE) in patients with shallow peripheral anterior chamber.

METHODS

We collected the ultrasound biomicroscopy (UBM) parameters before and one month after LE retrospectively. The binary logistic regression and artificial neural network (ANN) models of angle opening after LE were established using preoperative UBM parameters, and the predictive factors were screened. The performances of models were evaluated using the area under the receiver operator characteristic curve (AUROC).

RESULTS

Patients from the Zhongnan Hospital of Wuhan University were randomized into a training set (n = 91) or a test set (n = 39) for internal validation. External validation employed the entire Zhongnan Hospital cohort as the training set (n = 130) and Dawu County People's Hospital cohort as the test set (n = 30). Both internal and external validation using both models showed that iris curvature (IC), iris-ciliary process angle (ICPA), trabecular-iris angle (TIA), and gender were significantly predictive of the degree of angle opening after LE (p < 0.05). Both models achieved an AUROC of 0.993 (0.997-1.0) in the internal validation training set, and an AUROC of 0.929 (0.774-1.0) in the internal validation test set. In the external validation training set, both models achieved an AUROC of 0.995 (0.984-1.0), while in the external validation test, both models had an AUROC of 0.938 (0.800-1.0).

CONCLUSION

In patients with shallow peripheral anterior chamber, a smaller preoperative TIA, ICPA and IC predicts unsatisfactory angle opening after LE. Female can also be a risk factor for the narrow angle after LE.

Assessment of the ciliary muscle and scleral anterior thickness in high myopia by optical coherence tomography

PURPOSE

To assess ciliary muscle (CM) and anterior scleral thickness (AST) dimensions in vivo in high myopia using swept-source optical coherence tomography (SS-OCT) and to compare with emmetropic and hyperopic subjects.

METHODS

Cross-sectional study that included 34 high myopic patients (≥ -6 diopters [D]), 90 emmetropes (-1 to +1 D) and 38 hyperopic patients (≥ +3.5 D). CM thickness (CMT) and AST were measured in the temporal and nasal quadrants at 1, 2, and 3 mm from the scleral spur using SS-OCT. In addition, the length of the CM (CML) was evaluated.

RESULTS

The dimensions of the CML and the CMT at any of their measurement points were greater in high myopes and emmetropes than in hyperopes, both in the nasal and temporal quadrants (P < .001). However, there were no differences between high myopes and emmetropes for any of the parameters (P ≥ .076) except for the CMT at 3 mm in the temporal quadrant (P < .001). There were no differences in the AST between high myopes, emmetropes and hyperopes, in any of the measurement points or quadrants studied (P > .05).

CONCLUSIONS

The SS-OCT allows to measure the CM in vivo, not observing differences in its dimensions between high myopes and emmetropes, but they were smaller in hyperopes. In the measurement of the anterior sclera, no differences were observed between the three groups analyzed according to refraction.

Characteristics of ciliary muscle profile in high myopes measured by swept-source anterior segment optical coherence tomography

OBJECTIVE

To characterize and compare the ciliary muscle thickness (CMT) between low and high myopes using swept-source anterior segment optical coherence tomography (AS-OCT).

METHODS

Forty visually healthy young Chinese adults aged 18-25 years were divided into two groups based on refractive errors: low myopia (n = 20, spherical-equivalent refractive error (SER) between -0.50 D to -3.00 D) and high myopia (n = 20, SER ≤ -6.00 D). Cycloplegic refractions were performed before axial length (AL) and CMT were measured using a partial coherence laser interferometer and an AS-OCT respectively. CMT was measured perpendicularly to the sclera-ciliary muscle interface at 1 mm (CMT_1), 2 mm (CMT_2), and 3 mm (CMT_3) posterior to the scleral spur, and at the location with maximal thickness (CMT_MAX).

RESULTS

High myopes demonstrated thicker CMT at 2 mm (CMT_2, p = 0.035) and 3 mm (CMT_3, p = 0.003) posterior to the scleral spur, but thinner maximal CMT (CMT_MAX, p = 0.005) than low myopes. The apical CMT_1 and CMT_MAX were also thinner in high myopes than in low myopes (both p< 0.001). CMT_MAX, apical CMT_1, and apical CMT_MAX correlated directly with SER and inversely with AL; in contrast, CMT_2 and CMT_3 showed inverse correlations with SER but direct correlations with AL.

CONCLUSION

Our findings revealed significant differences in CMT between low and high myopes, with high myopes showing thicker CMT at 2 mm and 3 mm posterior to the scleral spur, but thinner maximal CMT. These results provide new evidence of the potential structural differences in ciliary muscles during myopia development and progression.

A case of bilateral diffuse uveal melanocytic proliferation with secondary angle closure caused by ciliary body thickening

Purpose

To describe a case of bilateral diffuse uveal melanocytic proliferation (BDUMP) with secondary angle closure caused by ciliary body thickening accompanied by intraocular pressure (IOP) elevation after mydriasis.

Observations

A 55-year-old woman with a history of ovarian cancer had blurred vision in both eyes. Fundus examination revealed multiple patchy lesions in both eyes and a nevus-like elevated lesion in the right eye. Anterior segment optical coherence tomography (AS-OCT) and ultrasound biomicroscopy (UBM) demonstrated angle closure resulting from ciliary body thickening. After mydriasis, the IOP was elevated in both eyes. Instillation of a miotic drug successfully reversed the IOP to normal levels.

Conclusions and Importance

BDUMP caused secondary angle closure in both eyes, presumably due to thickening of the entire ciliary body. AS-OCT and UBM were advantageous for analyzing the morphology of the anterior eye segment in BDUMP. Clinicians should be aware of the possibility of angle closure during the management of patients with BDUMP.

Anterior Ocular Biometrics as Measured by Ultrasound Biomicroscopy

Background: High frequency ultrasonography (ultrasound biomicroscopy; UBM) is an ophthalmic diagnostic tool that can be used to measure the depth of the anterior segment (ASD), the anterior chamber angle (ACA), as well as thicknesses of the iris and the ciliary body (CB). Methods: The anterior segment dimensions and thicknesses were measured by Sonomed 35-MHz. Results: Measurements for 95 eyes from 52 adults were analyzed. The mean and median ASD and ACA were 2.91, 2.92 ± 0.41 mm and 34.1, 34.3 ± 12.1 degrees, respectively. The angle superiorly was wider than inferiorly (p = 0.04). At the root of the iris, the mid of the iris, and the juxtapupillary edge of the iris, the iris thicknesses (median, mean) were 0.40, 0.41 ± 0.1, 0.50, 0.51 ± 0.1, and 0.70, 0.71 ± 0.1 mm, respectively. The thicknesses of CB and CB together with the ciliary processes (median, mean), were 0.70, 0.71 ± 0.15 mm and 1.36, 1.41 ± 0.15 mm, respectively. The upper quadrant of both the iris and the CB was significantly thicker than the lower quadrant (p = 0.04). Conclusions: Our biometric measurements for the anterior segment can be used as normative data for anterior segment depth and angle and iris and ciliary body thickness in normal eyes.

Imaging of the Ciliary Body: A Major Review

PURPOSE

We conducted a systematic search of literature to understand the various methods of imaging of the ciliary body.

METHODS

PubMed, Science Direct, Cochrane Library and Google Scholar were searched comprehensively and systematically to find studies related to the various modalities of ciliary body imaging.

RESULTS

The various ciliary body parameters that have been described are Ciliary body thickness, Ciliary body length, ciliary muscle thickness, ciliary process length, ciliary muscle length, ciliary muscle anterior length, trabecular ciliary process distance and Iris ciliary process distance. The various angles which have been measured, which mostly have a significance in Primary angle closure glaucoma (PACG) are Iris ciliary angle, Trabecular ciliary angle, scleral ciliary process angle. Various authors have defined them in various ways with subtle differences. Plateau iris and PACG mechanisms, not forgetting malignant glaucoma are better understood with imaging of the ciliary body using the ultrasound biomicroscopy (UBM). The anterior segment optical coherence tomography (ASOCT) imaging of the ciliary body has been described albeit with its own disadvantages. A few other fields dependant on the importance of ciliary body imaging are intravitreal injections, pars plana vitrectomy, measurements for implantable collamer lens (ICL) and of utmost importance, the differentiating features of ciliary body masses.

CONCLUSION

The UBM is still preferred over the ASOCT for imaging of the ciliary body. A lot of lacunae of knowledge still exists and consensus has to be reached on defining all the parameters universally. Future studies will be able to shed more light on the role of the ciliary body in the many ocular disorders mentioned in this review.

Ultrasound Biomicroscopy Measurements of the Normal Thickness for the Ciliary Body and the Iris in a Middle East Population

Purpose

Ciliary body (CB) and iris thicknesses may change with certain eye diseases as well as between different populations. Here, we report Ultrasound Biomicroscopy Measurements (UBM) of the normal thickness for the CB and the iris from a homogenous population in the Middle East.

Patients and Methods

Sonomed 35-MHz (SONOMED, INC. New York, USA) images were obtained at 4 radial meridians, and the thickness was measured at 3 locations along the radial length of the iris and at the thickest part of the CB. Parameters included mean thickness, median thickness, range, and standard deviation.

Results

Of 46 adult patients, 83 normal eyes were included in this analysis. The overall mean, median iris thicknesses at the iris root, midway along the radial length of the iris, and at the juxtapupillary margin in mm were 0.42, 0.41 ± 0.08, 0.52, 0.51± 0.08, and 0.72, 0.71± 0.1, respectively. The overall mean, median thicknesses of the CB and CB + ciliary processes in mm were 0.72, 0.71 ± 0.1, and 1.42, 1.37 ± 0.2 respectively. Gender, age, side, and height had no impact on iris and/or CB thickness (p>0.05). However, the iris thickness was significantly thicker in the superior quadrant than inferiorly, and in the nasal quadrant than the temporal quadrant (p=0.04), and the CB thickness and the CB + ciliary processes thickness were significantly thicker in the superior quadrant than inferiorly (P = 0.04 and 0.02 consecutively).

Conclusion

We measured in this study the normal thickness of the CB and the iris in normal eyes from homogenous population in the Middle East using ultrasound biomicroscopy. Our findings are essential for the ophthalmic community worldwide and in the Middle East region and can be used as a normative thickness data for the iris and CB in healthy eyes.

Ocular Biometry of Primary Angle-Closure Disease in Younger Patients

Background: The purpose of this study was to analyze the ocular biometric parameters of primary angle-closure disease (PACD) in younger patients and compare them with those of elderly patients. Methods: This clinic-based, cross-sectional study included 154 eyes of 154 patients with PACD, consisting of 77 eyes of patients aged 40 years or younger and 77 eyes of patients older than 40. The PACD case definition was compatible with the ISGEO definition. Anterior segment parameters were measured by ultrasound biomicroscopy, axial length (AL) and lens thickness (LT) were measured by A-scan ultrasonography measurements, and the thickness of the retina and choroid were measured by optical coherence tomography. The differences in ocular biometric parameters between different age groups were compared by independent sample t-tests or Mann-Whitney U tests, and the correlation between the parameters and age was analyzed. Results: Compared to older PACD patients, the lens vault(LV),LV/LT and subfoveal choroidal thickness (SFCT) of younger patients were larger, while the peripheral and mean iris thickness (IT), trabecular-ciliary angle (TCA), ciliary body thickness (CBT), AL and LT were smaller (all P < 0.01). There was no significant difference in anterior chamber depth, anterior chamber width, pupil diameter, angle opening distance at 500 μm from the scleral spur, anterior chamber angle and iris convexity between the two groups (all P > 0.05). AL, LT, IT, TCA and CBT were positively associated with age (all P < 0.001), while LV and SFCT were negatively associated with age (P = 0.027 and P < 0.001, respectively). Conclusions: Compared with elderly patients, younger PACD patients had more anteriorly positioned lenses, thinner and more anteriorly rotated ciliary bodies, thicker choroids, and shorter axial length. These characteristics might be important anatomical bases for the earlier onset of PACD and the higher risk of malignant glaucoma after filtering surgery.

Diagnostic imaging of the ciliary body: Technologies, outcomes, and future perspectives

The ciliary body (CB) is part of the uvea and is a complex, highly specialized structure with multiple functions and significant relationships with nearby structures. Its functions include the aqueous humor (AH) production in the ciliary processes, the regulation of the AH output through the uveoscleral pathway, and accommodation, which depends on the ciliary muscle. Also, the CB is an important determinant of angle width as it forms part of the ciliary sulcus. Until recently, knowledge of the CB was based on histological studies. However, this structure can currently be assessed in vivo using imaging techniques such as ultrasound biomicroscopy (UBM) and optical coherence tomography (OCT). Both techniques have shown good reproducibility of their measurements allowing for quantification of CB dimensions and their localization. In effect, studies have shown a larger CB in myopia and its diminishing size with age. Swept-source OCT devices offer fast, non-invasive high-resolution imaging allowing the identification of multiple structures. UBM requires contact and is uncomfortable for the patient. However, this technique offers deeper imaging and therefore remains the gold standard for assessing the posterior chamber, ciliary processes, or zonula. The clinical utility of CB imaging includes its assessment in different types of glaucoma such as angle-closure, malignant or plateau iris. Diagnostic CB imaging is also invaluable for the assessment of ciliochoroidal detachment when suspected, the position after the implantation of a pre-crystalline or sulcus-sutured lenses, diagnosis or monitoring of cysts or tumors, sclerotomies after retinal surgery, intermediate uveitis, or accommodation.

Ultrasound biomicroscopy in glaucoma assessment

Ultrasound biomicroscopy (UBM) is an important tool in the diagnosis, evaluation and follow up of glaucoma patients. Even if we are dealing with a primary angle closure glaucoma (PACG) or a primary open angle glaucoma (POAG) patient, the mechanism of angle closure can be revealed by performing an UBM. The device can help differentiate between the two types of glaucoma even in patients with opaque corneas when gonioscopy cannot be performed. Knowing the type of glaucoma is vital, especially regarding an individualized treatment, since each patient is unique and needs to be treated accordingly, in order to prevent glaucomatous optic neuropathy and visual field loss. Abbreviations: AC = anterior chamber, ICE = iridocorneal endothelial syndrome, IOP = intraocular pressure, NTG = normal tension glaucoma, PACG = primary angle closure glaucoma, PC = posterior chamber, PEX = pseudoexfoliation syndrome, POAG = primary open angle glaucoma, UBM = ultrasound biomicroscopy.

Assessment of angle closure spectrum disease as a continuum of change using gonioscopy and anterior segment optical coherence tomography

PURPOSE

Studies examining the anterior chamber angle and angle closure disease often compare quantitative angle information obtained using anterior segment optical coherence tomography (ASOCT) with one of several ordinal scales derived using gonioscopy. We test the assumption that the ordinal gonioscopic angle grades have equal step sizes and can be analysed using metric statistics.

METHODS

The medical records of 214 consecutive patients who were referred for assessment of the anterior chamber angle were prospectively examined using gonioscopy and ASOCT (Spectralis Optical Coherence Tomography, OCT, www.heidelbergengineering.com). Anterior chamber angle parameters (angle opening distance, AOD, and trabecular-iris space area, TISA at 500 and 750 microns) were extracted from ASOCT images using a semi-automated segmentation algorithm written on MATLAB (www.mathworks.com). We first matched the quantitative values for each gonioscopic grade (0-4, from no structures visible to ciliary body visible) and described the frequency distributions to determine separability. We then applied a grade-agnostic clustering algorithm to determine the concordance between algorithm-clustered groups (using solely quantitative data) and those obtained using gonioscopy.

RESULTS

The frequency distributions of the quantitative ASOCT parameters for each angle grade were mostly non-parametric and displayed unique distribution characteristics, with a floor effect seen for grade 0 and the lack of a ceiling effect seen for grades 3 and 4. Although we found significant differences in quantitative values across the five angle grades using the frequency distributions, some pairwise comparisons were indistinguishable (such as grades 0 and 1, and grades 3 and 4) due to the overlaps in distributions. On average, differences in quantitative values were consistent between gonioscopic grade steps, but there remained substantial variability that confounds prediction of change between ordinal steps. The clustering algorithm showed approximately 10% of cases with the same group assignment as that of the gonioscopic grade, improving slightly to 30% when the top 5% of quantitative data were excluded from analysis.

CONCLUSIONS

Our results do not necessarily support the assumption that the ordinal scales used in gonioscopy can be interpreted using an interval scale. We highlight the need for better methods of describing the course and risk of angle closure spectrum disease to identify disease progression and conversion, where gonioscopy remains the gold standard.

Ciliary muscle dimensions by swept-source optical coherence tomography and correlation study in a large population

PURPOSE

To examine ciliary muscle (CM) dimensions in vivo by swept-source optical coherence tomography (SS-OCT) in a large healthy population. To assess the reproducibility of CM measurements and correlations with different parameters.

METHODS

In this cross-sectional study, the following CM measurements were made in 495 eyes of 495 subjects in the temporal and nasal quadrants: length (CML), area (CMA) and thickness at distances of 1000 μm (CMT1), 2000 μm (CMT2) and 3000 μm (CMT3) from the scleral spur using the SS-OCT DRI-Triton^® (Topcon, Tokyo, Japan). These dimensions were then assessed for correlations with the factors age, gender, refractive error, anterior chamber angle (ACA) and intraocular pressure (IOP). The reproducibility of CM measurements was determined in 85 of the participants.

RESULTS

Mean age was 41.4 ± 17.5 years (range 5-83). The following means were recorded as follows: CML = 4.57 ± 0.73 mm (range 2.16-6.97), CMA = 1.35 ± 0.31 mm² (2.04-5.45), CMT1 = 558 ± 98 μm (299-891), CMT2 = 366 ± 100 μm (89-629) and CMT3 = 210 ± 75 μm (36-655). Negative correlation was detected between CML/CMA and age (R = -0.516/R = -0.404; p < 0.001) and refractive error (R = -0.519/R = -0.538; p < 0.001). No gender differences were observed (p ≥ 0.150). Both CML and CMA were correlated with ACA (R = 0.498 and 0.546; p < 0.001) and slightly with IOP (R = -0.175; p < 0.001). The reproducibility of the CM measurements was excellent (intraclass correlation coefficient ≥0.878).

CONCLUSIONS

Swept-source optical coherence tomography is a valid tool for in vivo CM measurements. Our data indicate a larger CM in myopes and its diminishing size with age.

Narrowing of the Anterior Chamber Angle during Valsalva Maneuver: A Possible Mechanism for Angle Closure

Purpose

To evaluate changes at the anterior chamber angle during Valsalva maneuver in eyes suspected to have a primary adult glaucoma.

Methods

Seventy-six consecutive patients underwent recording of applanation tonometry, measurement of the anterior chamber angle recess, angle opening distance, angle recess area, scleral spur-iris root distance, iris thickness, iridociliary angle, ciliary body thickness, anterior chamber depth, and pupil size on ultrasound biomicroscopy before and during the Valsalva maneuver. The Valsalva maneuver was standardized to a pressure of 40 mmHg for 15 seconds, using a manometer.

Results

The mean baseline intraocular pressure changed from 19.5±4.1 mmHg to 29.5±4.8 mmHg during Valsalva (p<0.0001). The anterior chamber angle recess narrowed from 17.9±9.5 to 7.8±9.2 degrees (p=0.0001). The angle recess area diminished from 0.15±0.14 mm2 to 0.14±0.12 mm2 (p=0.03) and the scleral spur to iris distance decreased from 0.19±0.2 mm to 0.16±0.18 mm (p=0.0001). The iridociliary angle narrowed from 72.6±33.5 degrees to 62.5±32.8 degrees (p=0.04). There was a significant increase in the thickness of the ciliary body, from 0.99±0.19 mm to 1.12±0.16 mm (p=0.001) and in iris thickness from 0.47±0.07 mm to 0.55±0.09 mm (p=0.0001). There was no significant change in the angle opening distance, anterior chamber depth, or pupillary diameter. A significant narrowing of the angle to less than 5 degrees was seen in 37 eyes, with iridocorneal apposition present in 28 eyes. After multivariate regression analysis it was found that the baseline ciliary body thickness and angle recess were significant predictors of narrowing of the angle (R2=96.1%).

Conclusions

Significant elevation of the intraocular pressure, narrowing of the anterior chamber angle recess, thickening of the ciliary body, and increase in the iris thickness is seen during the Valsalva maneuver. The Valsalva maneuver may lead to angle closure in eyes anatomically predisposed to primary angle closure glaucoma.

Effect of Lateral Decubitus Body Posture on Anterior Chamber Angle in Healthy Subjects: An Anterior Segment Optical Coherence Tomography Study

PURPOSE

To investigate the effect of the lateral decubitus (LD) position on the anterior chamber (AC) angle in healthy subjects.

MATERIALS AND METHODS

Twenty-three healthy young subjects were included in this prospective observational study. We measured AC angle parameters in the sitting and the left LD positions using anterior segment optical coherence tomography (Visante OCT): trabecular-iris angle (TIA), angle opening distance (AOD500), trabecular-iris space area (TISA500), anterior chamber width, lens vault, and anterior chamber depth. The Wilcoxon signed-rank test was used to compare the parameters between different body positions. Interobserver reproducibility of AC angle measurements was assessed by intraclass correlation coefficients.

RESULTS

Postural alterations from sitting to the left LD position significantly reduced the AC angle on the temporal side in right eyes (TIA: 39.53±2.38 to 38.31±3.47 degrees; AOD500: 0.72±0.13 to 0.65±0.08; TISA500: 0.25±0.06 to 0.22±0.04; all P<0.05), whereas no significant changes were noted on the nasal side. Contrastingly, a significant decrease in the AC angle on the nasal side was noted for left eyes (TIA: 39.49±2.24 to 38.17±2.76 degrees; AOD500: 0.68±0.09 to 0.64±0.10; TISA500: 0.23±0.04 to 0.21±0.03; all P<0.05). Anterior chamber width and anterior chamber depth were unaffected by postural alterations, but lens vault significantly was reduced following a shift to the left LD position.

CONCLUSIONS

The AC angle parameters on the nondependent side of the eye in the LD position were significantly reduced compared with those in the sitting position. Therefore, postural shift from sitting to the LD position may induce alterations in the AC angle.

Comparison of Ciliary Body Anatomy between American Caucasians and Ethnic Chinese Using Ultrasound Biomicroscopy

PURPOSE

To compare the ciliary body morphology between the Caucasians and Chinese, and to determine the associated anterior segment parameters.

METHODS

The study groups were comprised of four age- and gender-matched cohorts: American Caucasians, American Chinese, southern and northern mainland Chinese. Ultrasound biomicroscopy (UBM) was performed to assess the following measurements of the ciliary body: trabecular-ciliary process distance (TCPD), trabecular-ciliary process angle (TCA) and ciliary body thickness at 1 mm posterior to the scleral spur (CBT1). A-scan ultrasonography was used to measure lens thickness (LT) and relative lens position (RLP), defined as (ACD + LT/2)/AL.

RESULTS

There were 109, 111, 115 and 117 subjects enrolled in the American Caucasian, American Chinese, and southern and northern mainland Chinese groups, respectively. Collectively, the Chinese had smaller TCPD (0.834 ± 0.234 versus 0.940 ± 0.236 mm, p < 0.001) and TCA (75.1 ± 17.9 versus 85.0 ± 21.5, p < 0.001) than Caucasians. No difference was found between the three Chinese subgroups, therefore they were combined as one for the following analyses. After multiple linear regression analysis, adjusting for age, gender, spherical equivalent (SE) and axial length (AL), TCPD and TCA were positively associated with CBT1 and RLP, but negatively correlated with LT in the whole sample. The ethnic Chinese had significantly smaller CBT1 (SRC = -0.177, p < 0.001) and RLP (SRC = -0.254, p < 0.001) than that of Caucasians.

CONCLUSIONS

Compared with the Caucasians, the Chinese had a thinner ciliary body and a more anteriorly positioned lens, which may contribute to more anteriorly positioned ciliary processes in this population. These findings might help to explain the higher prevalence of angle closure in the Chinese.

Effects of Valsalva Maneuver on Ocular Biometric Parameters: Optical Low-Coherence Reflectometry Biometer Study

PURPOSE

To evaluate the effects of the Valsalva Maneuver (VM) on ocular biometry and intraocular pressure (IOP).

METHODS

This prospective observational study included 55 eyes of 55 healthy volunteers. Axial length (AL), central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), corneal curvature (K-steep, K-flat and K-mean), corneal diameter (WtW), and pupil diameter (PD) were measured with a LenStar LS 900® biometer at rest and during VM. The IOP was also measured at rest and during VM measurements were compared.

RESULTS

The VM did not have any significant influence on AL, WtW, K-flat, and K-mean (p > 0.05), but it decreased K-steep significantly (p < 0.001). Moreover, CCT and ACD decreased significantly during VM (p < 0.001), but VM increased IOP, PD (p < 0.001), and LT significantly (p = 0.002).

CONCLUSIONS

The VM might reversibly change in IOP and ocular biometry, so it should be considered during anterior segment examinations.

High prevalence of narrow angles among Chinese-American glaucoma and glaucoma suspect patients

PURPOSE

To evaluate the prevalence of gonioscopically narrow angles in a Chinese-American population with glaucoma or glaucoma suspicion.

PATIENTS AND METHODS

Charts from all Chinese-American patients seen in a comprehensive ophthalmology clinic in the Chinatown district of San Francisco in 2002 were reviewed. One eye from each patient with glaucoma or glaucoma suspicion that met inclusion criteria was included (n=108). Data were collected for sex, age, race (self-declared), refraction (spherical equivalent), intraocular pressure, gonioscopy, and vertical cup-to-disk ratio.

RESULTS

Sixty percent (n=65) of Chinese-American eyes with glaucoma or glaucoma suspicion had gonioscopically narrow angles (Shaffer grade < or = 2 in 3 or more quadrants). Those with narrow angles were significantly older (P=0.004) than their open angle counterparts, but the 2 groups did not differ in terms of sex, refraction, intraocular pressure, or cup-to-disk ratio (all, P > or = 0.071). In a multivariate model including age, sex, and refraction as predictors of angle grade (open or narrow), only age was a significant predictor of angle grade (P=0.004).

CONCLUSIONS

A large proportion of Chinese-Americans in our study population with glaucoma or glaucoma suspicion had gonioscopically narrow angles. In multivariate analysis, patients with narrow angles were older than those with open angles but did not differ from them in terms of sex or refraction. Continued evaluation of angle closure glaucoma risk among Chinese-Americans is needed.

Longitudinal study of anterior segment inflammation by ultrasound biomicroscopy in patients with acute anterior uveitis

PURPOSE

This study aimed to investigate dynamic changes in the anterior segment in patients with acute anterior uveitis (AAU) using ultrasound biomicroscopy (UBM).

METHODS

Acute anterior uveitis was diagnosed in 18 patients according to history and ocular examinations. Ultrasound biomicroscopy was performed and the results at three time-points (within 2 weeks of the uveitis attack, and at 2-4 weeks and 6 weeks after it) were analysed. The relationships between clinical manifestations and UBM findings were also evaluated.

RESULTS

All investigated AAU patients showed severe ciliary injection, numerous dust keratic precipitates (KPs), aqueous flare and inflammatory cells, and were treated predominantly with corticosteroid and cycloplegic eyedrops. Ultrasound biomicroscopy showed a large number of cells in the anterior and posterior chamber, marked oedema and exudates in and around the iris and ciliary body within 2 weeks of AAU onset. These abnormalities were dramatically improved at 2-4 weeks and almost resolved at 6 weeks and thereafter.

CONCLUSIONS

Ultrasound biomicroscopy reveals severe inflammatory changes in and around the ciliary body in patients with AAU. These signs rapidly resolve upon treatment.

Does an iridotomy provide protection against narrowing of the anterior chamber angle during Valsalva maneuvre in eyes with primary angle closure

PURPOSE

To evaluate changes at the anterior chamber angle during Valsalva manoeuver, in eyes having primary angle closure (PAC) and a patent laser peripheral iridotomy.

METHODS

Twenty-three eyes of 23 consecutive patients underwent a recording of applanation tonometry, measurement of the anterior chamber angle recess, angle opening distance, iris thickness, anterior chamber depth, and pupil size on ultrasound biomicroscopy before and during the Valsalva maneuver. The Valsalva manoeuver was standardized to a pressure of 40 mmHg for 15 s, using a manometer.

RESULTS

The mean baseline intraocular pressure changed from 18.86+3.79 to 26.73+4.73 mmHg during Valsalva, (P<0.0001). The anterior chamber angle recess narrowed from 16.62+6.24 to 6.5+4.02 degrees (P<0.0001). There was a significant increase in the thickness of the ciliary body from 0.92+0.25 to 1.17+0.31 mm (P=0.0006) and in the iris thickness from 0.47+0.17 to 0.57+0.11 mm (P=0.007). A significant increase in pupillary diameter (P=0.008) and a decrease in the angle opening distance (P<0.0001) also occurred during Valsalva, whereas there was no significant change in the anterior chamber depth (P=0.056). The angle recess during Valsalva had a positive correlation with the baseline anterior chamber angle (r=0.41, P=0.05) and a negative correlation with the ciliary body thickness (r=-0.52, P=0.046).

CONCLUSIONS

The induction of Valsalva maneuver in day-to-day activities can lead to significant anterior segment angle shallowing and can lead to progression from the PAC stage to primary angle closure glaucoma in such predisposed eyes. The presence of a patent laser iridotomy may not prevent irido trabecular apposition during the Valsalva maneuver.

Relation between axial length of the eye and hypotensive effect of latanoprost in primary open angle glaucoma

AIMS

To study the effect of axial length on the hypotensive effect of latanoprost in primary open angle glaucoma (POAG) in a prospective, observational study.

METHODS

The authors measured axial length and baseline intraocular pressure (IOP) of 109 eyes with POAG, and then repeated the IOP measurements at 1, 3, and 6 months after starting treatment with latanoprost.

RESULTS

The mean IOP level was significantly lower in eyes with a shorter axial length compared with the eyes with a longer axial length both at 3 and 6 months of treatment (p = 0.03 and p = 0.04, respectively, ANOVA).

CONCLUSION

The hypotensive effect resulting from treatment with latanoprost could be related to ocular axial length.