Ultrasound biomicroscopic and conventional ultrasonographic study of ocular dimensions in primary angle-closure glaucoma

OBJECTIVE

To determine the biometric findings of ocular structures in primary angle-closure glaucoma (PACG).

DESIGN

An observational case series with comparisons among three groups (patients with acute/intermittent PACG [A/I-PACG], patients with chronic PACG [C-PACG], and normal subjects [N]).

PARTICIPANTS

A total of 54 white patients with PACG (13 male, 41 female) were studied: 10 with acute, 22 with intermittent, and 22 with chronic types of PACG. Forty-two normal white subjects (11 male, 31 female) were studied as control subjects. Only one eye was considered in each patient or subject.

TESTING

Ultrasound biomicroscopy (UBM) and standardized A-scan ultrasonography (immersion technique) were performed in each patient during the same session or within 1 to 3 days.

MAIN OUTCOME MEASURES

The following A-scan parameters were measured: anterior chamber depth (ACD), lens thickness (LT), axial length (AL), lens/axial length factor (LAF), and relative lens position (RLP). Ten UBM parameters were measured, the most important of which were anterior chamber angle, trabecular-ciliary process distance (TCPD), angle opening distance at 500 microm from the scleral spur (AOD 500), and scleral-ciliary process angle (SCPA).

RESULTS

Compared to normal subjects, the patients with PACG presented a shorter AL (A/I-PACG = 22.31 +/- 0.83 mm, C-PACG = 22.27 +/- 0.94 mm, N = 23.38 +/- 1.23 mm), a shallower ACD (A/I-PACG = 2.41 +/- 0.25 mm, C-PACG = 2.77 +/- 0.31 mm, N = 3.33 +/- 0.31 mm), a thicker lens (A/I-PACG = 5.10 +/- 0.33 mm, C-PACG = 4.92 +/- 0.27 mm, N = 4.60 +/- 0.53 mm), and a more anteriorly located lens (RLP values, A/I-PACG = 2.22 +/- 0.12, C-PACG = 2.34 +/- 0.16, N = 2.41 +/- 0.15). The LAF values in A/I-PACG, C-PACG, and N were 2.28 +/- 012, 2.20 +/- 0.11, and 1.97 +/- 0.12, respectively. Anterior chamber angle (A/I-PACG = 11.72 +/- 8.84, C-PACG = 19.87 +/- 9.83, N = 31.29 +/- 9.18 degrees) and SCPA (A/I-PACG = 28.71 +/- 4.02, C-PACG = 30.87 +/- 6.04, N = 53.13 +/- 9.58 degrees) were narrower, TCPD (A/I-PACG = 0.61 +/- 0.12 mm, C-PACG = 0.71 +/- 0.14 mm, N = 1.08 +/- 0.22 mm) and AOD 500 shorter (A/I-PACG = 0.13 +/- 0.09 mm, C-PACG = 0.21 +/- 0.10 mm, N = 0.36 +/- 0.11 mm) in patients with PACG. All the biometric differences proved statistically significant using the one-way analysis-of-variance test.

CONCLUSIONS

In patients with PACG, the anterior segment is more crowded because of the presence of a thicker, more anteriorly located lens. The UBM confirms this crowding of the anterior segment, showing the forward rotation of the ciliary processes. A gradual progressive shift in anatomic characteristics is discernible on passing from normal to chronic PACG and then to acute/intermittent PACG eyes.

The mechanism of increasing outflow facility by rho-kinase inhibition with Y-27632 in bovine eyes

Rho-kinase inhibitor Y-27632 (Y-27) affects actomyosin cytoskeletal networks and has been shown to significantly increase outflow facility (C) in enucleated porcine and rabbit eyes, as well as in vivo monkey eyes without obvious toxicity. The mechanisms underlying these responses remain largely unknown. In this study, we investigate how Y-27 affects aqueous humor C, the hydrodynamic patterns of outflow, and the morphology of the inner wall (IW) and juxtacanalicular connective tissue (JCT). 12 bovine eyes were perfused at 15 mmHg with Dulbecco's PBS containing 5.5 mM glucose (DPBS) to establish stable baseline C. The anterior chamber was exchanged and perfused with DPBS containing 50 microM Y-27 in 7 eyes, while 5 eyes received DPBS alone. Eyes were then perfused with DPBS containing fluorescent microspheres (0.5 microm; 0.002% v/v) at a fixed volume to deliver equivalent amounts of tracer to label the hydrodynamic filtration patterns. All eyes were perfusion-fixed with Karnovsky's fixative. Radial and frontal sections were prepared in all quadrants and confocal images were taken along the IW of the aqueous plexus (AP). The total length (TL) and filtration length (FL) of the IW were measured in > or =16 images/eye, and the average percent effective filtration length (PEFL=FL/TL) was calculated. Sections with AP were processed and examined by light and electron microscopy. The TL of the IW and length exhibiting JCT/IW separation (SL) were measured in > or =16 micrographs/eye, and the average percent separation length (PSL=SL/TL) was also calculated. After Y-27 treatment, C increased from 1.54+/-0.34 (+/-SEM) to 2.36+/-0.54 microL/min per mmHg (58.2+/-18.9%) while control eyes changed from 1.67+/-0.41 to 1.71+/-0.39 microl/min per mmHg (6.0+/-9.3%) and the percent changes between the Y-27-treated and control eyes were significant (p=0.03). Control eyes showed segmental distribution of tracer in the trabecular meshwork tending to cluster near collector channel ostia, whereas Y-27-treated eyes showed a more uniform pattern and extensive labeling along the IW. In Y-27-treated eyes, PEFL was 3-fold larger (57.6+/-3.7%) compared to control eyes (18.2+/-4.5%; p<0.001). Light microscopic examination revealed that, with Y-27, the IW and JCT were significantly distended compared to control eyes, with discernible separation between the IW and JCT. PSL was 2.8-fold larger in Y-27-treated eyes (59.3+/-3.6%) than in controls (20.8+/-2.0%; p<0.001). A significant positive correlation was found between PEFL and PSL (p=0.003) suggesting that as connectivity between the JCT and IW decreases the available area for aqueous humor drainage increases along the AP. Our study also demonstrates a significant positive correlation between C and the PSL (p=0.01), a finding identical to what we reported to occur during the "washout" effect in bovine eyes. Our data suggests the structural correlate to the increase in C and PEFL after Y-27-treatment is physical separation between the JCT and IW. The increase in C after Y-27-treatment may share a similar mechanism comparable with the washout effect that occurs in bovine eyes. Overall, these findings support our hypothesis that JCT/IW connectivity influences local outflow hydrodynamics that regulate C, and suggest that strategies targeting JCT/IW connectivity are promising anti-glaucoma therapies to reduce IOP.

Ultrasonographic biomicroscopy, Scheimpflug photography, and novel provocative tests in contralateral eyes of Chinese patients initially seen with acute angle closure

OBJECTIVES

To compare ocular biometry of the contralateral eyes of individuals seen with acute angle closure (AAC) with eyes of population-based control subjects, and to assess novel provocative tests to study the mechanism of AAC.

DESIGN

Prospective case-control study.

PARTICIPANTS

Chinese persons seen as incident cases of AAC and Chinese population-based controls.

METHODS

Slitlamp assessment, ultrasonographic biomicroscopy, Scheimpflug photography, and provocative testing were performed.

MAIN OUTCOME MEASURES

Ocular biometric parameters including anterior chamber depth, limbal anterior chamber depth, axial length, lens thickness, and radius of corneal curvature were obtained. Ultrasonographic biomicroscopy parameters that include the angle-opening distance at 500 micro m and the angle-recess area were noted. Scheimpflug photography produced a single measure of angle width.

RESULTS

Contralateral eyes of cases of AAC had shorter axial lengths, shallower anterior chamber depths, thicker lenses, and steeper radii of corneal curvature (P<.01). After adjusting for age and sex, cases had a mean adjusted axial length that was 1.2 mm shorter, an optical anterior chamber depth that was 0.63 mm shallower (24% shallower than controls), and lenses that were, on average, 0.35 mm thicker (P<.01). Furthermore, using multiple logistic regression to adjust for age and sex, patients with primary angle-closure glaucoma were 19 times as likely to have a shallower limbal anterior chamber depth (25%; 95% confidence interval, 8.3-45.2). Adjusting for age and sex, the mean angle-opening distance at 500 microm was 0.14 U less for cases, with a mean of 0.26 U in controls, making the angle-opening distance at 500 microm, on average, 54% less among cases. Scheimpflug photographs revealed an adjusted angle width of 21.6 degrees for controls and 15.1 degrees for cases (P<.05). Dynamic testing showed that the angle of control eyes tended to shallow less when going from light to dark and tended to open more when given 1 drop of pilocarpine hydrochloride.

CONCLUSIONS

Contralateral eyes of individuals having an AAC attack tend to be shorter and have more crowded anterior segments than those of healthy controls. These static measures of ocular biometry indicate why some individuals are predisposed to AAC. Dynamic measures of the response to luminance changes and pilocarpine therapy indicate that differential reactions to these stimuli are also associated with an AAC attack.

Ultrasound activates the TM ELAM-1/IL-1/NF-kappaB response: a potential mechanism for intraocular pressure reduction after phacoemulsification

PURPOSE

Elevated intraocular pressure (IOP), the major causal risk factor for glaucoma, often decreases after cataract removal by phacoemulsification ultrasound. In this study, the hypothesis that ultrasound energy propagated through a fluid medium induces a stress response with the potential to lower IOP was investigated.

METHODS

Normal and glaucomatous trabecular meshwork (TM) cell culture lines were initiated from tissue isolated from human cadaveric eyes or trabeculectomy specimens. Cultured cells were treated for 60 seconds with a phacoemulsification ultrasound probe set to a power of 70%. Activation of the TM cell-specific stress response was assayed by enzyme-linked immunosorbent assay (ELISA) and immunolocalization.

RESULTS

Normal TM cell cultures did not release detectable levels of the stress response protein, IL-1alpha, into their culture medium. In contrast, IL-1alpha was easily detected after treatment with ultrasound energy. Consistent with earlier findings, glaucomatous TM cells produced IL-1alpha constitutively, and the level of expression was increased after treatment with phacoemulsification ultrasound. As was previously demonstrated, the stress-regulated transcription factor NF-kappaB was present in the cytoplasm of normal cells, but in the nucleus of glaucomatous cells. After treatment with ultrasound energy, NF-kappaB translocated to the nucleus in the normal cells. Endothelial leukocyte-adhesion molecule (ELAM)-1 was not detected in normal TM cells, but was constitutively present on glaucomatous TM cells, consistent with findings in previous work. ELAM-1 expression was induced in normal cells by ultrasound treatment.

CONCLUSIONS

A potentially IOP-lowering stress response is induced in TM cells by ultrasound. The findings suggest that this response may be induced clinically during cataract removal by phacoemulsification, and may be one mechanism responsible for the reduction in IOP that often follows this procedure.

Imaging the aqueous humor outflow pathway in human eyes by three-dimensional micro-computed tomography (3D micro-CT)

The site of outflow resistance leading to elevated intraocular pressure in primary open-angle glaucoma is believed to be located in the region of Schlemm's canal inner wall endothelium, its basement membrane and the adjacent juxtacanalicular tissue. Evidence also suggests collector channels and intrascleral vessels may have a role in intraocular pressure in both normal and glaucoma eyes. Traditional imaging modalities limit the ability to view both proximal and distal portions of the trabecular outflow pathway as a single unit. In this study, we examined the effectiveness of three-dimensional micro-computed tomography (3D micro-CT) as a potential method to view the trabecular outflow pathway. Two normal human eyes were used: one immersion fixed in 4% paraformaldehyde and one with anterior chamber perfusion at 10 mmHg followed by perfusion fixation in 4% paraformaldehyde/2% glutaraldehyde. Both eyes were postfixed in 1% osmium tetroxide and scanned with 3D micro-CT at 2 μm or 5 μm voxel resolution. In the immersion fixed eye, 24 collector channels were identified with an average orifice size of 27.5 ± 5 μm. In comparison, the perfusion fixed eye had 29 collector channels with a mean orifice size of 40.5 ± 13 μm. Collector channels were not evenly dispersed around the circumference of the eye. There was no significant difference in the length of Schlemm's canal in the immersed versus the perfused eye (33.2 versus 35.1 mm). Structures, locations and size measurements identified by 3D micro-CT were confirmed by correlative light microscopy. These findings confirm 3D micro-CT can be used effectively for the non-invasive examination of the trabecular meshwork, Schlemm's canal, collector channels and intrascleral vasculature that comprise the distal outflow pathway. This imaging modality will be useful for non-invasive study of the role of the trabecular outflow pathway as a whole unit.

Noncontact Goniometry With Optical Coherence Tomography

OBJECTIVE

To assess the value of noncontact goniometry with optical coherence tomography (OCT) compared with current clinical parameters in the evaluation of the anterior chamber angle (ACA).

DESIGN

Prospective observational study of 138 eyes of 109 patients.

METHODS

The ACA parameters and angle-opening distance (AOD) were measured with slitlamp-adapted OCT goniometry. The iris and scleral thickness and the iris convexity were assessed with OCT. Both ACA and AOD were compared with the clinical parameters of gonioscopy grade, limbal anterior chamber depth (ACD), ultrasonographic central ACD, and lens-axial length (LAL) ratio.

RESULTS

Noncontact goniometry with OCT revealed mean +/- SD values of 28 degrees +/- 16 degrees for the ACA and 381 +/- 234 mum for the AOD. The mean +/- SD iris thickness was 369 +/- 84 mum, and the scleral thickness at the scleral spur was 943 +/- 148 mum. There was a significant correlation (P<.001) with the clinical parameters of gonioscopic grading, limbal ACD, ultrasonographic central ACD, and LAL ratio. The sensitivity and specificity of OCT goniometry to detect an occludable angle were 86% and 95% for ACA and 85% and 90% for AOD, respectively.

CONCLUSIONS

Noncontact goniometry with OCT was helpful in evaluating the anterior chamber structures and as a screening modality. Goniometry with OCT could improve the noninvasive clinical assessment and treatment of patients with glaucoma.

Uveal effusion in primary angle-closure glaucoma

PURPOSE

To determine the prevalence of uveal effusion in acute and chronic primary angle-closure glaucoma (PACG) or primary angle closure (PAC) and to compare it with the prevalence in eyes with open-angle glaucoma (OAG) or ocular hypertension.

DESIGN

Prospective consecutive case series.

PARTICIPANTS

Five hundred one eyes of 351 consecutive patients with PAC and 156 eyes of 116 randomly selected primary OAG or ocular hypertension patients. The PAC group included 40 eyes of 35 patients with acute PACG and 30 unaffected fellow eyes, 39 eyes and 35 fellow eyes with a history of acute PACG, and 357 eyes with chronic PAC.

METHODS

Ultrasound biomicroscopic examination was performed to diagnose uveal effusion and to measure anterior chamber depth (ACD).

MAIN OUTCOME MEASURES

Presence of uveal effusion and ACD.

RESULTS

Uveal effusion was demonstrated in 23 eyes (58%) with acute PACG and 7 fellow eys (23%) (chi2 = 8.17, P = 0.0043). Among eyes with chronic PAC, uveal effusion was present in 69 [corrected](14%[corrected]), a higher prevalence than was found in open-angle patients (2 eyes [1.3%]) (chi2 = 19.3, P<0.001). In the chronic PAC group, the ACD of phakic eyes with uveal effusion (1.92+/-0.42 mm) was significantly shallower than that of phakic eyes without effusion (2.06+/-0.32 mm) (P = 0.019).

CONCLUSIONS

Uveal effusion diagnosed by ultrasound biomicroscopy is a special feature in PAC, and is prevalent in acute PACG. Uveal effusion in phakic eyes with PAC is associated with shallowing of ACD.

Aqueous outflow regulation: Optical coherence tomography implicates pressure-dependent tissue motion

Glaucoma is a leading cause of blindness worldwide and results from damage to the optic nerve. Currently, intraocular pressure is the only treatable risk factor. Changes in aqueous outflow regulate pressure; regulation becomes abnormal in glaucoma. From inside the eye aqueous flows out through the trabecular meshwork into a venous sinus called Schlemm's canal, next into collector channels and finally returns to the episcleral vessels of the venous system. The location of aqueous outflow regulation is unknown. Ex vivo and in vivo studies implicate both pressure-dependent trabecular tissue motion and tissues distal to Schlemm's canal in regulation of aqueous outflow. Technologies have not previously been available to study these issues. New ex vivo imaging in human eyes identifies hinged flaps or leaflets at collector channel entrances using a high-resolution spectral domain optical coherence tomography (SD-OCT) platform. The hinged flaps open and close in synchrony with pressure-dependent trabecular meshwork motion. The SD-OCT platform images from the trabecular meshwork surface while experimentally changing transtrabecular pressure gradients. New in vivo imaging in human eyes uses a motion sensitive technology, phase-sensitive OCT to quantitate real-time pulse-dependent trabecular tissue motion as well as absence of such motion when aqueous access to the outflow system is blocked. The recent studies suggest that aqueous outflow regulation results from synchronous pressure-dependent motion involving a network of interconnected tissues including those distal to Schlemm's canal. The new imaging technologies may shed light on glaucoma mechanisms and provide guidance in the management of medical, laser and surgical decisions in glaucoma.

Prevalence of appositional angle closure determined by ultrasonic biomicroscopy in eyes with shallow anterior chambers

PURPOSE

To determine the prevalence of appositional angle closure in eyes with a shallow peripheral anterior chamber but no peripheral anterior synechia (PAS) in Japanese patients.

DESIGN

Cross-sectional study.

PARTICIPANTS

Eighty eyes of 80 consecutive patients with a shallow peripheral anterior chamber, determined using the method of van Herick, and no PAS.

METHODS

The anterior chamber angle was classified according to Shaffer's grading with noncompression gonioscopy superiorly, inferiorly, temporally, and nasally. The absence of PAS was confirmed by compression gonioscopy if necessary. The presence of appositional angle closure and the trabecular-iris angle (T-I angle) was determined with ultrasound biomicroscopy in each quadrant under light and dark conditions. Factors related to appositional angle closure were studied using logistic analysis, and the covariates included gender, age, refraction, gonioscopic grading, and the quadrant of the angle measured.

MAIN OUTCOME MEASURES

Gonioscopic grading of the angle width, the T-I angle, and the prevalence of appositional closure.

RESULTS

The gonioscopic grading (P<0.001 in light and dark) and the T-I angle (P<0.001 in light and dark) varied significantly among the 4 quadrants. Narrower angle gradings were observed more frequently superiorly. The T-I angle was narrower superiorly (in light) and inferiorly (in dark) (P<0.001 and P = 0.040, respectively). The T-I angle was significantly narrower in dark than in light (P<0.001). The sites with the narrower gonioscopic gradings tended to have a smaller T-I angle (P<0.001 and P = 0.006 in light and dark, respectively). Appositional angle closure was found in at least 1 quadrant in 46 (57.5%) of 80 eyes in light and in 68 eyes (85%) in dark. Logistic analysis showed that gonioscopic grading and the quadrant were significantly related to the presence of appositional angle closure in light and dark (P<0.003 for both comparisons).

CONCLUSIONS

Appositional angle closure was frequently observed in eyes with a shallow peripheral anterior chamber, especially under dark conditions in Japanese patients. The angle width, evaluated with conventional gonioscopic grading, and the quadrant of the angle were significantly related to the presence of appositional angle closure.

Prevalence and mechanism of appositional angle closure in acute primary angle closure after iridotomy

PURPOSE

A prospective observational case series to assess the prevalence of appositional angle closure in darkness among iridotomized Chinese eyes after acute primary angle closure (APAC) with the use of both clinical methods and ultrasound biomicroscopy.

METHODS

Sixteen Chinese patients who had history of APAC and subsequent successful treatment with laser peripheral iridotomy were examined. Fourteen additional control subjects were studied. Gonioscopy and ultrasound biomicroscopic examination were performed in the dark. Gonioscopic appearance of the angle was assessed, and quantitative measurements of the angle from the ultrasound biomicroscopic images were taken.

RESULTS

Of the APAC eyes 55.6% had appositionally closed angle clinically and in 38.9% only Schwalbe's line was visible on gonioscopy. Ultrasound biomicroscopy confirmed structurally different anterior segments between eyes with APAC and the control eyes. In particular, the trabecular-ciliary-process distances were markedly different between the two groups.

CONCLUSION

This study documented a high prevalence of appositional closure in iridotomized eyes after APAC in Chinese patients. The anteriorly positioned ciliary body, as documented in these cases by ultrasound biomicroscopy, is the likely mechanism of the angle crowding in this patient population.

Effects of pulse width on erbium:YAG laser photothermal trabecular ablation (LTA)

An erbium (Er):YAG laser can remove trabecular meshwork (TM) by photothermal ablation with minimal contiguous thermal damage. A variable pulse width Er:YAG laser was used to investigate the effect of varying pulse width on ablation of human TM. Trabecular photothermal ablation was performed on tissue obtained from eye bank eyes at pulse widths of 50, 150, and 250 microseconds, with energy held constant at 4 mJ. At this energy, a single laser pulse was sufficient for full-thickness ablation of TM. Laser energy was delivered through a 200-microns diameter optical fiber held in apposition to the tissue sample, which was immersed in physiologic saline. High-speed photography of the resultant steam bubbles also was performed. Light microscopy and scanning electron microscopy of TM ablated at 50 microseconds revealed the greatest variability in size (0-140 microns) of the full-thickness ablated areas and demonstrated blast effects, tissue shredding and < or = 10 microns thermal damage. At 150 microseconds, the full-thickness ablated areas were more consistent size (115-120 microns), showed no blast effects and 10 to 20 microns thermal damage. At 250 microseconds, the largest ablations were found (180-220 microns) and showed no blast damage; however, a significant amount of thermal damage (< or = 50 microns) was evident. The steam bubbles produced by the laser energy were largest at 50 microseconds and did not begin to collapse until well over twice the original pulse interval. At 150 and 250 microseconds, the steam bubbles were successively smaller and dissipated at the end of the laser pulse.(ABSTRACT TRUNCATED AT 250 WORDS)

Kramers-Kronig analysis of attenuation and dispersion in trabecular bone

A restricted-bandwidth form of the Kramers-Kronig dispersion relations is applied to in vitro measurements of ultrasonic attenuation and dispersion properties of trabecular bone specimens from bovine tibia. The Kramers-Kronig analysis utilizes only experimentally measured properties and avoids extrapolation of ultrasonic properties beyond the known bandwidth. Compensation for the portions of the Kramers-Kronig integrals over the unknown bandwidth is partially achieved by the method of subtractions, where a subtraction frequency acts as an adjustable parameter. Good agreement is found between experimentally measured and Kramers-Kronig reconstructed dispersions. The restricted-bandwidth approach improves upon other forms of the Kramers-Kronig relations and may provide further insight into how ultrasound interacts with trabecular bone.

Evaluation of the anterior chamber angle in Asian Indian eyes by ultrasound biomicroscopy and gonioscopy

PURPOSE

To compare the ultrasound biomicroscopic measurement of the anterior chamber angle in Asian Indian eyes, with the angle width estimated by gonioscopy.

MATERIALS AND METHODS

PARTICIPANTS

Patients with open and closed angles attending a glaucoma clinic were recruited for the study.

OBSERVATION PROCEDURES

Temporal quadrants of the angles of patients were categorized by gonioscopy as Grade 0 to Grade 4, using Shaffer's classification. These angles were quantified by ultrasound biomicroscopy (UBM) using the following biometric characteristics: Angle opening distance at 250 micro (AOD 250) and 500 micro (AOD 500) from the scleral spur and trabecular meshwork-ciliary process distance (TCPD). The angles were further segregated as "narrow angles" (Schaffer's Grade 2 or less) and "open angles" (Schaffer's Grade 3 and 4).

MAIN OUTCOME MEASURES

The UBM measurements were computed in each case and analyzed in relation to the gonioscopic angle evaluation.

RESULTS

One hundred and sixty three eyes of 163 patients were analyzed. One hundred and six eyes had "narrow angles" and 57 eyes had "open angles" on gonioscopy. There was a significant difference among the mean UBM measurements of each angle grade estimated by gonioscopy (P < 0.001). The Pearson correlation coefficient between all UBM parameters and gonioscopy grades was significant at the 0.01 level. The mean AOD 250, AOD 500 and TCPD in narrow angles were 58+/-49 micro, 102+/-84 micro and 653+/-124 respectively, while it was 176+/-47 micro, 291+/-62 micro and 883+/-94 micro in eyes with open angles (P < 0.001) respectively.

CONCLUSIONS

The angle width estimated by gonioscopy correlated significantly with the angle dimensions measured by UBM. Gonioscopy, though a subjective test, is a reliable method for estimation of the angle width.

Anterior Chamber Angle Assessment Using Gonioscopy and Ultrasound Biomicroscopy

PURPOSE

Comparison of anterior chamber angle measurements using ultrasound biomicroscopy (UBM) and gonioscopy.

METHODS

Five hundred subjects were evaluated for grading of angle width by the Shaffer method. UBM was done in the same group to document angle width, angle opening distance (AOD 500), and anterior chamber depth. Biometric parameters were documented in all subjects. UBM and gonioscopic findings were compared.

RESULTS

A study was conducted in 282 men and 218 women with a mean age of 57.32 +/- 12.48 years. Gonioscopic grading was used to segregate occludable (slit-like, grades 1 and 2) from nonoccludable (grades 3 and 4) angles. Subjective assessment by gonioscopy resulted in an overestimation of angle width within the occludable group when compared with values obtained by UBM. This did not affect the segregation of occludable versus nonoccludable angles by gonioscopy. Biometric parameters in eyes with occludable angles were significantly lower in comparison with eyes with nonoccludable angles, except for lens thickness. AOD 500 correlated well with angle width.

CONCLUSIONS

We concluded that clinical segregation into occludable and nonoccludable angles by an experienced observer using gonioscopy is fairly accurate. However, UBM is required for objective quantification of angles, and AOD 500 can be a reliable and standard parameter to grade angle width.

Ultrasound biomicroscopy of the eye in cystinosis

OBJECTIVE

To describe the ocular ultrasound biomicroscopy (UBM) findings in patients with cystinosis.

METHODS

Six patients with infantile nephropathic cystinosis, aged 16 to 25 years, and 6 controls (matched for age and spherical refractive error) were examined clinically and with UBM. Scleral reflectivity, corneal and iris thickness, central anterior chamber depth, angle width, trabecular meshwork to ciliary process distance, and ciliary sulcus width were measured.

RESULTS

No patient had glaucoma or posterior synechiae, but all had crystals in the trabecular meshwork apparent with gonioscopy. Using UBM, the cornea and iris appeared similar in both groups, but the scleral reflectivity was increased in patients (P =.003). The angle was narrower in patients (mean +/- SD, 20 degrees +/- 7 degrees ) than controls (31 degrees +/- 5 degrees, P<. 001). The anterior chamber was shallower in patients (2556 +/- 197 microm) than controls (2968 +/- 284 microm, P<.001). The ciliary sulcus was closed or narrow in all patients (83 +/- 112 microm) compared with controls (339 +/- 135 microm, P<.001), with a reduction in the trabecular meshwork to ciliary process distance.

CONCLUSIONS

This report of ocular UBM findings in cystinosis demonstrated narrowing of the angle and a ciliary body configuration similar to that reported for plateau iris syndrome. Gonioscopy demonstrated crystals in the trabecular meshwork. These findings may explain the predisposition of these patients to glaucoma.

Novel approach for anterior chamber angle analysis: anterior chamber angle detection with edge measurement and identification algorithm (ACADEMIA)

OBJECTIVE

To describe a novel approach to measuring anterior chamber angle dimensions and configurations.

METHODS

Sixty-nine images were selected randomly from the ultrasound biomicroscopic image database to develop the algorithm. Thirty images were selected for further analyses. The value of each pixel of the 8-bit grayscale ultrasound biomicroscopic images was quantized into 0 (black) or 1 (white), and the edge points outlining the angle were detected and fitted with straight lines. The dimensions and profiles of anterior chamber angles were then measured.

RESULTS

The algorithm failed to identify the edge points correctly in 8 (11.6%) of 69 images because of strong background noise. Three basic types of angle configuration were identified based on the derived angle profiles: constant, increasing, and decreasing, which corresponded to flat, bowed forward, and bowed backward iris contours, respectively. The angle measurements demonstrated high correlation with trabecular-iris angle and angle opening distance 500 (calculated as the distance from the corneal endothelium to the anterior iris surface perpendicular to a line drawn at 500 mum from the scleral spur). The strongest association was found between the averaged angle derived from the angle profile and the angle opening distance 500 (r = 0.91).

CONCLUSION

The proposed algorithm has high correlations with angle opening distance and trabecular-iris angle with the added advantages of being fully automated, reproducible, and able to capture the characteristic angle configurations. However, good-quality ultrasound biomicroscopic images with high signal-to-noise ratio are required to identify the edge points correctly.

Assessment of Circumferential Angle Closure with Swept-Source Optical Coherence Tomography: a Community Based Study

PURPOSE

To evaluate the diagnostic performance of swept-source optical coherence tomography (SS-OCT, CASIA SS-1000; Tomey Corporation, Nagoya, Japan) for angle closure detection, in comparison with gonioscopy, in a community setting.

DESIGN

Reliability analysis.

METHODS

A total of 2027 phakic subjects aged ≥50 years, with no previous history of glaucoma, laser (including peripheral iridotomy), intraocular surgery, or ocular trauma, were consecutively recruited from a community polyclinic in Singapore. Gonioscopy was performed by a single trained ophthalmologist. SS-OCT angle scans, which obtain radial scans for the entire circumference of the angle, were analyzed by a single examiner, masked to the subject's clinical details. On SS-OCT images, angle closure was defined as contact between the iris and any part of the angle wall anterior to the scleral spur. Different cutoff values of the degree of circumferential angle closure (≥35%, ≥50%, and ≥75%) were taken for analysis to assess SS-OCT performance in detecting angle closure.

RESULTS

A total of 1857 subjects (91.6%) were included in the final analysis after excluding poor-quality SS-OCT scans. Almost 90% of the subjects were Chinese, with a mean age of 61.8 ± 6.7 years, and more than half were women (63.5%). The overall AUC of SS-OCT manual grading against gonioscopy was 0.84 (95% confidence interval, 0.81-0.88). The prevalence of angle closure on SS-OCT was 26.1% for the ≥35% definition, with an area under the curve of 0.80 (0.77-0.84), sensitivity of 82.5% (75.3%-88.4%), and specificity of 78.5% (76.5%-80.4%). The first-order agreement coefficient statistics for the 2-quadrant gonioscopic definition of angle-closure with corresponding ≥35%, ≥50%, and ≥75% angle closure definitions for SS-OCT were good at 0.89 (0.83-0.93), 0.88 (0.842-0.93), and 0.88 (0.831-0.99), respectively.

CONCLUSIONS

In this large community-based study, SS-OCT exhibited moderate performance for angle closure detection compared to gonioscopy as the reference standard.

Narrow Angles and Angle Closure

OBJECTIVE

To quantitatively investigate the ultrasound biomicroscopic features of eyes with asymmetric narrowing of the iridocorneal angles.

METHODS

Asymmetric angles were defined as those differing by 2 or more Shaffer grades between the superior and inferior angles. We performed ultrasound biomicroscopy on 18 eyes in 18 patients. Measurements of the following were made: the angle recess area, the triangular area bordered by the anterior iris surface, the corneal endothelium, and a line drawn from 750 microm anterior to the scleral spur; the y-intercept, the estimated angle opening distance at the level of the scleral spur; acceleration, which describes how rapidly the angle widens from the iris root; trabecular-ciliary process distance, the distance between the trabecular meshwork and the ciliary body at 500 microm anterior to the scleral spur; and angle recess-iris insertion distance, the distance between the apex of the angle recess and the iris insertion on the ciliary body face.

RESULTS

In the superior angle, 11 eyes developed appositional closure, 10 with B-type (apposition beginning at the iris root) and 1 with S-type (apposition beginning at the line of Schwalbe). Four eyes also had apposition inferiorly (1 B-type and 3 S-types). The y-intercept, angle recess areas, trabecular-ciliary process distance, and angle recess-iris insertion distance were significantly smaller in the superior quadrant. S-type angles predominated in the inferior angle, and B-type angles did in the superior angle, indicating a more posterior insertion of the iris in the wider inferior angles.

CONCLUSIONS

Asymmetry in eyes with narrow angles occurs because of differences in iris insertion position on the ciliary body face and from asymmetry of the ciliary body position.

Tear in the trabecular meshwork caused by an airsoft gun

PURPOSE

To report a case of a tear in the trabecular meshwork caused by an airsoft gun, a toy that propels a plastic bullet.

METHODS

Case report.

RESULTS

A 7-year-old Japanese boy sustained an ocular injury to the right eye from an airsoft gun. Ophthalmic examination 1 hour after the injury showed a best-corrected visual acuity in the injured eye of hand motion, corneal abrasion and edema, hyphema, and commotio retinae. Gonioscopy 6 days after the injury revealed a tear in the trabecular meshwork as well as an angle recession. Ultrasound biomicroscopy (UBM) strongly suggested that the tear extended into Schlemm's canal. Corneal abrasion and edema, hyphema, and commotio retinae resolved over 10 days, and best-corrected visual acuity improved to 20/15. Two months after the injury, the trabecular meshwork had not healed.

CONCLUSION

Airsoft guns can cause a full-thickness tear in the trabecular meshwork, which may contribute to development of late-onset glaucoma. UBM is useful to evaluate the tomographic features of the disrupted trabecular meshwork. The potential force of airsoft guns to cause substantial ocular injuries should be recognized. Wearing ocular protection should be mandatory while playing with airsoft guns.

Ultrasound biomicroscopic measurement of development of anterior chamber angle

AIM

To establish normative values for the anterior segment in normal infants and children in relation to age.

METHODS

Anterior segments were measured in 46 normal infants and children (21 males and 25 females, aged from 1 to 60 months (mean 17.09 (SD 16.99) months)), by use of ultrasound biomicroscopy.

RESULTS

Anterior chamber depth, trabecular-iris angle, angle opening (trabecular-iris) distances at 250 and 500 microm from the scleral spur, and the thickness of the thickest part of the iris were 1724-3473 microm (2505 (SD 480) microm), 15.35-44.79 degrees (28.74 (7.46) degrees ), 116-367 microm (247.4 (65.9) microm), 166-509 microm (349.5 (87.1) microm), and 249-579 microm (434.6 (74.6) microm), respectively. All factors in this study showed a significant correlation with logarithm of age (r = 0.937, p = 0. 0001; r = 0.867, p = 0.0001; r = 0.929, p = 0.0001; r = 0.917, p = 0. 0001; r = 0.748, p = 0.0001), and significantly correlated with each other.

CONCLUSIONS

Ultrasound biomicroscopy is a powerful tool for obtaining precise images and measurement of the development of the anterior segment in infants and children. Normative values were established for anterior segment dimensions in relation to age. Anterior chamber depth, trabecular-iris angle, angle opening distances at 250 and 500 microm from the scleral spur, and iris thickness showed linear increases in relation to logarithm of age.

Peripheral anterior synechiae and ultrasound biomicroscopic parameters in angle-closure glaucoma suspects

PURPOSE

To investigate the correlation between peripheral anterior synechia (PAS) and the quantitative anterior chamber angle parameters measured by ultrasound microscopy (UBM) in angle-closure glaucoma suspect (ACGS) eyes.

METHODS

Eyes were defined ACGS as having occludable angles and intraocular pressure less than 21 mm Hg without glaucomatous optic nerve head. The gonioscopic criteria for ACGS were the trabecular meshwork invisible in 3 or more quadrants of the entire angle and the angular width less than 20 degrees by Shaffer classification. Twenty-seven eyes of 20 patients underwent anterior chamber angle and ciliary body imaging with UBM. Angle opening distance (AOD(500)), angle recess area (ARA), trabecular-ciliary process distance (TCPD) and trabecular-iris angle (TIA) were measured from the UBM images at each quadrant.

RESULTS

The AOD(500), ARA, and TIA were not significantly different between the eyes with PAS (9 eyes) and without PAS (18 eyes) at each quadrant. However, the TCPD was significantly shorter in the superior quadrant when compared with the eyes without PAS (mean: 405.3+/-70.9 microm vs 536.4+/-140.5 microm) (p<0.05).

CONCLUSIONS

The results suggest that the shorter distance from trabecular meshwork to ciliary body or the anterior placement of ciliary process may play a role in the development of PAS in ACGS eyes.

Ultrasound biomicroscopic analysis of the effect of pilocarpine on the anterior chamber angle

BACKGROUND

This study was carried out to determine the effects of pilocarpine on the anterior chamber angle in healthy volunteers.

METHODS

We measured changes in anterior chamber depth (ACD), trabecular-iris angle (TIA), angle opening distance at 250 and 500 microns from the scleral spur (AOD250 and AOD500), and iris thickness using ultrasound biomicroscopy in 48 eyes of 48 normal volunteers (ages 18-57 years, mean 34.8 years) before and 1 h after instillation of 2% pilocarpine.

RESULTS

Pilocarpine altered the TIA by -18.6 degrees to +10.5 degrees (mean -4.16 degrees), and change in the TIA increased significantly and linearly in relation with decrease in the pretreatment TIA (r = 0.929). Pilocarpine altered AOD250 change by -136 to +94 microns (mean -38 microns) and AOD500 by -151 to +157 microns (mean -42 microns); changes in the AOD250 and AOD500 were significantly correlated to the pretreatment AOD250 and AOD500 values, respectively (r = 0.923 and r = 0.896, respectively). The pilocarpine-induced change in the ACD showed a linear relationship to the pretreatment ACD (r = 0.887). The changes in the TIA, AOD250 and AOD500 showed greater increases in association with lower pretreatment ACD (r = 0.848, r = 0.891, r = 0.842) and smaller change in the ACD (r = 0.834, r = 0.839, r = 0.812).

CONCLUSIONS

The response of the anterior chamber angle to pilocarpine, narrowing or widening, depended on its pretreatment state. The ability to predict the pilocarpine-induced change in the angle before the instillation of pilocarpine would be helpful in treating patients with glaucoma.