Iridocorneal Angle Structures Research Articles

Imaging fine structures of the human trabecular meshwork in vivo using a custom design goniolens and OCT gonioscopy.

The trabecular meshwork (TM), located within the iridocorneal angle, is a target for many glaucoma treatments aimed at controlling intraocular pressure. However, structural variations between individuals are poorly understood. We propose a newly designed gonioscopic lens optimized for high-resolution imaging to image fine structures of the human TM in vivo. The body of the new lens is index-matched to the human cornea and includes a choice of two gonioscopic mirrors (59° and 63°) and matching air-spaced doublets placed on the anterior surface of the goniolens. The new design allows a diffraction-limited image plane at the iridocorneal angle structures. The goniolens design was built and then placed on the subjectś eyes coupled to the cornea with goniogel and a 3D adjustable mount. Images were obtained using a commercially available OCT device (Heidelberg Spectralis). The optical resolution was measured in a model eye as 40.32 and 45.25 cy/mm respectively for each mirror angle. In humans, dense OCT scans with minimum spacing oriented tangential to the iris and ICA were performed on 7 healthy subjects (23-73 yrs). The TM was successfully imaged in all subjects. The custom goniolens improved the contrast of the uveoscleral meshwork structures and corneoscleral meshwork revealing limbus parallel striations, not visible with previous goniolens designs. Transverse OCT images were constructed along the segmentation line, providing an enface image of the TM structures including corneoscleral beams, previously only imaged in vivo using custom adaptive optics systems.

Assessment of the iridocorneal angle pigmentation and structures after the implantation of EVO+ Visian Implantable Collamer Lens.

To evaluate the effect of EVO+ Visian Implantable Collamer Lens (ICL) implantation on the iridocorneal angle pigmentation and structures. Myopic refractive surgery candidates who underwent posterior chamber EVO+ ICL implantation were evaluated preoperatively and 3 and 6months postoperatively. High-resolution images of the iridocorneal angle (nasal, superior, temporal and inferior quadrants) were acquired during gonioscopy. A masked observer, blinded to study visits and patients' information, evaluated the angle width, apparent iris root insertion, iris configuration, and trabecular meshwork pigmentation according to the Spaeth scale in two different occasions. The intra-rater reliability was estimated using the weighted Gwet's Agreement Coefficient (AC2). Differences between visits were analyzed using the Cochran Q test or the Friedman test. Twenty-one patients (13 females and 8 males) aging 31.3 ± 6.3years old were recruited. The intra-rater reliability of gonioscopy assessment was excellent for every parameter assessed (AC2 ≥ 0.97). No significant differences were found among the study visits for any quadrant in the angle width (p ≥ 0.74), apparent iris root insertion (p ≥ 0.22), iris configuration (p ≥ 0.21) and trabecular meshwork pigmentation (p ≥ 0.24). Mean pigmentation of trabecular meshwork for the four quadrants did not vary either among visits (p = 0.25). The EVO+ ICL implantation after uneventful procedures appears not to clinically affect the iridocorneal angle pigmentation and/or structures during a short-medium follow-up using gonioscopy assessment. The intra-rater reliability of glaucoma specialists assessing iridocorneal angle structures using gonioscopy images is very high.

447 Characterization of the human iridocorneal angle in vivo using a custom design goniolens with OCT gonioscopy

OBJECTIVES/GOALS: The trabecular meshwork (TM) and Schlemm’s canal (SC), located within the iridocorneal angle (ICA), form the main outflow pathway and a major target for glaucoma treatments. We characterized the human ICA in vivo with Optical Coherence Tomography (OCT) imaging using a customized goniolens and a commercial OCT device (Heidelberg Spectralis). METHODS/STUDY POPULATION: Imaging these structures is difficult due to the optical limitations of imaging through the cornea at high angles. Therefore, a clinical gonioscopy lens was modified with a 12mm plano-convex lens placed on its anterior surface to focus light on the ICA structures, and capture returning light. Each subjects’ eye was anesthetized with 1 drop of Proparacaine 0.5%. The goniolens was coupled to the eye with gonio-gel and it was held by a 3D adjustable mount. OCT volume scans were acquired on 10 healthy subjects. The linear polarization of the OCT was rotated with a half-waveplate to measure dependence of the ICA landmarks on polarization orientation. RESULTS/ANTICIPATED RESULTS: The TM was seen in 9 of 10 subjects. Polarization rotation modified the brightness of the band of extracanalicular limbal lamina (BELL) and corneoscleral bands due to the birefringent nature of the collagenous structures, increasing the contrast of SC. SC width was 99 ± 20µm varying in size over space, including a subject with SC narrowing in the inferior-temporal quadrant. DISCUSSION/SIGNIFICANCE: This clinically suitable gonioscopic OCT approach has successfully been used to image the human ICA in 3D in vivo, providing detailed characterization of the TM and SC as well as enhancing their contrast against their birefringent backgrounds by rotating the polarization of the imaging beam.

Iridocorneal angle assessment in children with spontaneously regressed retinopathy of prematurity.

To assess anterior segment anatomic parameters in school-aged children with spontaneously regressed retinopathy of prematurity (sr-ROP) and in children born preterm without ROP history (preT). sr-ROP and preT children were compared with healthy, born at term children (control group). Biometric characteristics were measured with the IOLMaster. Iridocorneal angle structure was evaluated using Visante AS-OCT, and angle opening distance, trabecular iris space area and scleral spur angle were calculated. Best-corrected visual acuity (BCVA) was measured with the ETDRS chart. We examined 22 eyes of 11 children with sr-ROP, 26 eyes of 13 preT children and 24 eyes of 12 healthy controls, with a median age of 8years. sr-ROP children exhibited worse mean BCVA and reduced AL compared to controls (p = 0.001 and p = 0.007, respectively). A narrower iridocorneal angle was found in sr-ROP compared to the preT and the control groups. Preterm children were found to have similar anterior chamber angle metrics compared to the full-term control group. In this study, school-aged children with a history of sr-ROP had narrower angles compared to preterm- and term-born children. AS-OCT demonstrated structural differences of the iridocorneal angle in sr-ROP, possibly reflecting a mild developmental arrest of the anterior segment.

A Prospective Analysis of iStent Inject Microstent Implantation: Surgical Outcomes, Endothelial Cell Density, and Device Position at 12 Months.

The surgical outcome of iStent inject devices is associated with device protrusion within the anterior chamber. Schlemm canal (SC) dilatation has a prognostic value. iStent inject devices do not move within the first year after implantation. The iStent inject is a device designed to be implanted ab-interno through the trabecular meshwork. The present study follows up on our preliminary report, using successive in vivo anterior segment optical coherence tomography (AS-OCT) imaging to analyze the associations between stent positioning, iridocorneal angle structures, and surgical outcomes. In total, 54 eyes of 42 patients (73.3±7.4 y) with cataract and mild-to-moderate open-angle glaucoma were examined in this prospective study. All patients underwent implantation of 2 iStent inject devices combined with phacoemulsification. Patients were followed up over a 12-month period. AS-OCT was performed after 3 and 12 months. Thirty unoperated fellow eyes served as control eyes. Intraocular pressure (IOP) decreased from 16.5±4.2 mm Hg at baseline to 15.1±3.7 mm Hg at 12 months (-8.7%; P=0.004), while medications decreased from 1.8±1.0 to 0.5±0.9 (-72.2%; P<0.001). Unmedicated IOP≤18 mm Hg was achieved in 58.8% of operated eyes. No sight-threatening complications were reported. On AS-OCT, 44.9% of devices were buried within the trabeculum. Device position was unchanged between scans. Regression analysis elicited significant predictors: SC dilatation effect [risk ratio (RR)=0.230; P=0.003], greatest SC diameter (RR=0.991; P=0.049), extrusion of the most anterior device (RR=0.993; P=0.012), gonioscopically visible devices (RR=0.406; P=0.040), baseline treatments (RR=2.214; P=0.001), and baseline IOP (RR=0.184; P=0.006). Endothelial cell density decreased by 14.6% at 12 months (P<0.001). This study demonstrates the IOP-lowering and medication-lowering potential of iStent inject surgery in primary open-angle and pseudoexfoliative glaucoma. It confirms that surgical outcomes are positively associated with device protrusion within the anterior chamber, and suggests SC dilatation effect as a favorable prognostic indicator. It shows that stents are stable in time, highlighting the importance of the initial implantation location.

Identification and Characterization of Imaging Technique Errors and Artifacts Using Anterior-Segment OCT for Irido-Corneal Angle Evaluations in Glaucoma

Anterior-segment OCT (AS-OCT) platforms provide noninvasive and quantifiable evaluations of anterior chamber angle (ACA) anatomy. Although these ACA measurements have been validated with high repeatability and reproducibility, there is a paucity of data previously published regarding the technique errors and artifacts (TEA) that may occur during imaging of the ACA. The purpose of this study was to report on the types and frequency of imaging TEA that are seen in ACA evaluation of a large cohort of patients with open-angle glaucoma. Retrospective, cross-sectional design. Images were obtained with AS-OCT from 5082 eyes of 2541 patients with glaucoma and were reviewed at the Doheny Image Reading Center (DIRC). Images had been captured using AS-OCT devices from 4 different manufacturers (Zeiss Cirrus [Oberkochen, Germany], Heidelberg Spectralis [Heidelberg, Germany], Optovue RTVue [Fremont, CA], or Zeiss Visante). All images were analyzed by 2 independent and certified DIRC image readers for angle opening distance under Schwalbe's line (SL-AOD), and then re-reviewed by a DIRC-certified principal investigator to adjudicate nonconsensus measurements. Images were defined to have TEA when image readers were unable to confidently measure the SL-AOD. Type and frequency of TEA in the AS-OCT image. Of 5082 eyes reviewed, 208 images (4.09%) were found to have TEA that restricted proper visualization of irido-corneal angle structures and measurements of SL-AOD. The most common TEA was that the image readers were unable to identify Schwalbe's line (74% of TEA images). Other common TEA included poor visualization of the anterior iris surface (15%), misaligned scan location (11%), irregular corneal irregularities (5%), and illumination-related pupillary abnormalities (4%). This large-scale study presents the types and frequency of TEA found in AS-OCT-derived angle images. More than 95% of the images reviewed were usable for the quantification of irido-corneal angle measurements. Knowing the common types of TEA may help in enhancing the training of both human image readers and in the design of automated algorithms to improve image acquisition and image interpretation parameters. This will become especially useful as AS-OCT becomes more widely used in clinical practice for anterior chamber assessment.

Retinoic Acid Maintains Function of Neural Crest-Derived Ocular and Craniofacial Structures in Adult Zebrafish.

PurposeRetinoic acid (RA) is required for embryonic formation of the anterior segment of the eye and craniofacial structures. The present study further investigated the role of RA in maintaining the function of these neural crest–derived structures in adult zebrafish.MethodsMorphology and histology were analyzed by using live imaging, methylacrylate sections, and TUNEL assay. Functional analysis of vision and aqueous humor outflow were assayed with real-time imaging.ResultsBoth decreased and increased RA signaling altered craniofacial and ocular structures in adult zebrafish. Exogenous treatment with all-trans RA for 5 days resulted in a prognathic jaw, while inhibition of endogenous RA synthesis through treatment with 4-diethylaminobenzaldehyde (DEAB) decreased head height. In adult eyes, RA activity was localized to the retinal pigment epithelium, photoreceptors, outer plexiform layer, inner plexiform layer, iris stroma, and ventral canalicular network. Exogenous RA increased apoptosis in the iris stroma and canalicular network in the ventral iridocorneal angle, resulting in the loss of these structures and decreased aqueous outflow. DEAB, which decreased RA activity throughout the eye, induced widespread apoptosis, resulting in corneal edema, cataracts, retinal atrophy, and loss of iridocorneal angle structures. DEAB-treated fish were blind with no optokinetic response and no aqueous outflow from the anterior chamber.ConclusionsTight control of RA levels is required for normal structure and function of the adult anterior segment. These studies demonstrated that RA plays an important role in maintaining ocular and craniofacial structures in adult zebrafish.

Evaluation of the iridocorneal angle with accommodation using optical coherence tomography

The changes in the iridocorneal angle structure during accommodation are assessed by means of anterior segment optical coherence tomography. Thirteen right eyes were included in the study. The device used for the measurement was the Visante®omni system. The stimuli were set up at different vergences (0.0 D, -1.5 D, and -3.0 D). The angle opening distance 500 and 750, the trabecular iris space area 500 and 750, and the scleral spur angle parameters were assessed at the nasal and temporal regions. The results in the iridotrabecular angle comparing the three accommodative states of the eye did not yield any statistically significant difference at nasal or temporal angle sections. In light of our results and in the conditions of our study, the structures of the iridocorneal angle are not significantly changed with accommodation.

Identification of iridocorneal angle structures assessed by Fourier domain optical coherence tomography

ObjectiveTo study the structures of the iridocorneal angle using anterior segment optical coherence tomography (OCT) defining their tomographic characteristics and quantifying their identification frequency. Material and methodsA cross-sectional study was performed on 267 right eyes of 267 consecutive healthy patients. Fourier domain OCT RTVue (Optovue Inc, CA, EE. UU.) was used to examine the iridocorneal angle in the nasal and temporal sectors. The structures evaluated were: sclerocorneal limbus, sclerocorneal transition, Schwalbe's line, trabecular meshwork, Schlemm's canal, scleral spur, and angular recess. Within and between agreements to identify structures were calculated using Cohen's kappa coefficient. ResultsThe mean age was 41.3±14.3 years (range 20–80), with 57% being women. The sclerocorneal limbus, sclerocorneal transition, and Schwalbe's line were identified by 98.7, 97 and 93.4% of the images, respectively, with the trabecular meshwork and Schlemm's canal being identified in 91% of cases. The scleral spur could be identified in 85.4%, and the angular recess in 74.5%. There was no difference in the identification between the temporal and nasal sectors. Within and between agreement was k=0.92 and k=0.88, respectively, in the identification of the structures of the total images studied. ConclusionsFourier domain OCT is a reliable technique for the identification of the structures of the iridocorneal angle, among which can be highlighted are, the trabecular meshwork, Schlemm's canal, scleral spur, and Schwalbe's line.

Complete 360° circumferential gonioscopic optical coherence tomography imaging of the iridocorneal angle.

Clinically, gonioscopy is used to provide en face views of the ocular angle. The angle has been imaged with optical coherence tomography (OCT) through the corneoscleral limbus but is currently unable to image the angle from within the ocular anterior chamber. We developed a novel gonioscopic OCT system that images the angle circumferentially from inside the eye through a custom, radially symmetric, gonioscopic contact lens. We present, to our knowledge, the first 360° circumferential volumes (two normal subjects, two subjects with pathology) of peripheral iris and iridocorneal angle structures obtained via an internal approach not typically available in the clinic.

Morphological analysis of age-related iridocorneal angle changes in normal and glaucomatous cases using anterior segment optical coherence tomography

PurposeTo analyze age-related morphological changes of the iridocorneal angle in normal subjects and glaucomatous cases, using anterior segment optical coherence tomography (AS-OCT).MethodsThis study involved 58 eyes of 58 open-angle glaucoma cases and 72 eyes of 72 age-matched normal-open-angle control subjects. Iridocorneal angle structures in nasal and temporal regions and anterior chamber depth (ACD) were measured using AS-OCT. Axial length and refractive error were measured by use of an ocular biometer and auto refractor keratometer. Angle opening distance (AOD), angle recess area (ARA), and trabecular-iris space area (TISA), measured at 500 μm (TISA500) and 750 μm (TISA750) distant from the scleral spur, were calculated, in the nasal and temporal regions. A new index, the peripheral angle frame index (PAFI), which represents the peripheral angle structure, was proposed, and was defined as (TISA750-TISA500)/TISA500.ResultsRefractive power in the glaucoma cases was less than in control cases (P<0.0001). Axial length (P<0.0001) and ACD (P=0.0004) were longer and deeper, respectively, in the glaucoma cases, compared with the control cases. In both control and glaucoma groups, ACD, AOD, ARA, and TISA decreased linearly in an age-dependent manner, while PAFI stayed at relatively constant values throughout the age distribution. AOD in the glaucoma group was longer than in the control group, in both the temporal and nasal regions; ARA and TISA were larger in the glaucoma than in the control group. However, no significant differences in nasal or temporal PAFI were found between the glaucoma and control groups.ConclusionThe findings of this study show that AS-OCT is useful for the quantitative evaluation of age-related changes in peripheral angle structure in glaucoma and control cases.

Magnetic resonance imaging findings in Axenfeld&amp;ndash;Rieger syndrome

Axenfeld–Rieger syndrome (ARS) is a genetic disorder representing a disease spectrum resulting from neural crest cell maldevelopment. Glaucoma is a common complication from the incomplete formation of the iridocorneal angle structures. Neural crest cells also form structures of the forebrain and pituitary gland, dental papillae, aortic arch walls, genitalia, and long bones; therefore, patients with ARS manifest a wide range of systemic findings. To our knowledge, detailed magnetic resonance imaging findings have not been previously reported. We report a case of a 19-month-old Indian male diagnosed with ARS with emphasis on magnetic resonance imaging findings of the globes, brain, teeth, and skull base.

Changes in Iridocorneal Angle Structure and Trabecular Pigmentation With STAAR Implantable Collamer Lens During 2 Years

To evaluate the changes in iridocorneal angle structure and trabecular pigmentation after implantation with the STAAR Implantable Collamer Lens (ICL), as potential risk factors of secondary glaucoma. An ICL was implanted in 48 eyes of 29 patients with high myopia. Angle opening distance (distance between trabecular meshwork and iris) measured at 500 microm from the scleral spur and trabecular-iris angle were assessed preoperatively and at 1, 6, 12, and 24 months postoperatively by ultrasound biomicroscopy, and trabecular pigmentation was evaluated preoperatively and at 1, 12, and 24 months postoperatively by standardized gonioscopic photography. Mean follow-up was 33.2 +/- 7.3 months. One-month postoperative trabecular-iris angle and angle opening distance values were significantly smaller than preoperative values by 41.5% and 31.8%, respectively (P < .001), but no significant progressive changes were observed thereafter. The mean trabecular pigmentation of four quadrants did not change significantly during the first month after ICL implantation (P = .317), but significantly decreased at 1 and 2 years postoperatively compared with the preoperative value (P = .039 and .047, respectively). Intraocular pressure (IOP) remained stable in all eyes throughout follow-up except in one eye, which showed elevated IOP and significantly increased trabecular pigmentation requiring antiglaucoma medications. No ongoing narrowing of iridocorneal angle was noted after approximately 40% narrowing at 1 month postoperatively. There was no general increase in trabecular pigmentation or IOP over a mean follow-up of 33.2 months. Considering significant initial angle crowding and one eye with increased trabecular pigmentation and IOP, careful monitoring of iridocorneal angle and IOP is required during the early postoperative period, especially for 1 month.