Iris Configuration Research Articles

Dynamic Analysis of Iris Configuration with Anterior Segment Optical Coherence Tomography

To evaluate dynamic changes in iris configuration and their association with anterior chamber angle width by using anterior segment optical coherence tomography (ASOCT). Forty-six normal subjects with open angles and 40 with narrow angles (Shaffer grade < or =2 in three or more quadrants during dark room gonioscopy) were analyzed. The dynamic ASOCT dark-light changes of iris bowing were captured with real-time video recording and nasal iris bowing, nasal anterior chamber angle, and pupil diameter were measured in serial image frames selected from the video capture. The associations between iris bowing, iris thickness, anterior chamber depth (ACD), age, anterior chamber angle, and pupillary diameter measurements were evaluated with univariate and multivariate regression analyses. The relationship between iris bowing and pupil diameter was largely linear, with three dynamic patterns observed: (1) convex-to-convex (iris remains convex in dark and light); (2) concave-to-convex (iris changes from concave to convex from light to dark); and (3) concave-to-concave (iris remains concave in dark and light). All the subjects with narrow angles had convex-to-convex anatomy, although 43% of the subjects with open angles also demonstrated this pattern. These individuals were older and had shorter axial length (both with P < 0.001). Older age (r = -0.352, P = 0.001), smaller ACD (r = 0.382, P < 0.001), and smaller difference in angle opening distance in light and dark (r = 0.472, P < 0.001) were associated with smaller differences in iris bowing in the light and dark. ACD and iris bowing were independently associated with anterior chamber angle width. Independent of ACD, iris bowing is an important biometric parameter that determines angle width. Investigation of iris dynamics may offer a new perspective in understanding the risk and mechanism of primary angle closure.

Comparaison de la tomographie par cohérence optique et de la biomicroscopie ultrasonore dans la détection de l’iris plateau

To compare optical coherence tomography (OCT) and ultrasound biomicroscopy (UBM) for detection of plateau iris configuration and confirmation of plateau iris syndrome. Three subjects with plateau iris configuration were recruited. All patients underwent gonioscopy, UBM, and OCT. The anterior chamber angle in each patient was imaged with a commercially available OCT unit. The angle configurations were assessed and compared with the UBM images. Both OCT and UBM showed excellent performance in identifying eyes with plateau iris. The UBM confirmed the plateau iris diagnosis by showing the iris root indentation caused by the ciliary body. The OCT, which is a rapid, non-contact exam, and non-operator-dependent, can only show indirect signs, because it cannot detect structures behind the iris. Nevertheless, the indirect signs with OCT were accurate enough to make the diagnosis. The OCT also shows the angle closure risk in a sitting patient, and is therefore more physiologic than the UBM exam, for which the patient is supine. OCT can directly show a patent laser iridotomy and confirm its efficacy. The OCT can detect indirect signs of plateau iris syndrome after iridotomy. The OCT unit can be practically employed to confirm a clinical suspicion of plateau iris configuration and syndrome.

The Lens and Angle Closure

Angle closure is a disorder of ocular anatomy characterized by closure of the drainage angle by appositional or synechial approximation of the iris against the trabecular meshwork, blocking its access to aqueous humor. This results in an elevation of the intraocular pressure (IOP), due to the consequent impairment of aqueous outflow from the eye, followed by the development of glaucomatous optic neuropathy.The obstruction may result from an anatomical predisposition of the eye including pupillary block and/or angle crowding (from plateau iris configuration or anterior lens position) or may be due to pathophysiologic processes in any part of the eye.The role of the lens in the etiopathogenesis of PACG has received considerable attention in current literature.This article is a comprehensive review of current knowledge and its implications in current practice.

A $Ku$-Band High-$Q$ Tunable Filter With Stable Tuning Response

A Ku-band tunable filter with a very stable notch level and in-band RF performance is presented in this paper. A new coupling iris configuration for stable RF performance over the tuning range is realized. The filter employs two dual-mode TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">113</sub> tunable cavity resonators with a set of flexible bellows. A tuning range of more than 500 MHz at 12 GHz while maintaining a high Q is demonstrated using the introduced resonator. Design techniques, including an RF-mechanical tradeoff analysis, are detailed and addressed.

Iridoplastia con láser argón como tratamiento del iris plateau secundario a múltiples quistes del cuerpo ciliar: seguimiento a largo plazo con biomicroscopía ultrasónica

We present a 37 year-old man with secondary angle closure by neuroepithelial ciliary body cysts. An argon laser peripherical iridoplasty was performed and ultrasound biomicroscopy (UBM) was employed to follow-up. Initially, the patient had a favorable response to treatment, but six months later the cysts and the secondary closed angle reappeared. Argon laser peripheral iridoplasty has been proposed as treatment of plateau-like iris configuration resulting from neuroepithelial ciliary body cysts. However, the cysts and, the secondary closed angle could recur in a long-term (Arch Soc Esp Oftalmol 2009; 84: 569-572).

Ultrasound Biomicroscopy in Narrow Peripheral Anterior Chamber Eyes With or Without Peripheral Anterior Synechiae

To compare the configurations of the anterior ocular segment including the anterior chamber (AC) angle and ciliary body between eyes with a narrow AC angle (ACA) with and without peripheral anterior synechiae (PAS). One hundred and one eyes of 101 consecutive patients with a temporal peripheral AC depth one-quarter of the corneal thickness or less were included. Gonioscopy and ultrasound biomicroscopy were performed under light and dark conditions. The existence of PAS was further confirmed with compression gonioscopy with indentation. Eyes with findings suggestive of plateau iris configuration or those with glaucomatous optic neuropathy were carefully excluded. The biometric parameters including the ACA, the angle opening distance at 500 mum, the trabecular-ciliary process distance, the iris-zonule distance, and the scleral-ciliary process angle were determined. PAS were found in 43 (43%) of the 101 eyes. There were no differences in age, refractive error, or intraocular pressure between PAS-positive and PAS-negative eyes (P>0.1). ACA, iris-zonule distance, scleral-ciliary process angle under light and/or dark conditions were significantly smaller in the PAS-positive eyes than in the PAS-negative eyes (P<0.05). Shallow peripheral AC depth and relatively anteriorly located ciliary body was significantly associated with the presence of PAS in eyes with a narrow ACA.

Potential of the Pentacam in Screening for Primary Angle Closure and Primary Angle Closure Suspect

To compare the Pentacam to ultrasound biomicroscopy (UBM) or gonioscopy in detecting eyes with primary angle closure (PAC), including PAC suspect and PAC glaucoma. In 72 eyes of 39 Japanese with various anterior chamber angle (ACA) widths, the ACA, anterior chamber depth (ACD), and anterior chamber volume (ACV) were measured using the Pentacam, and the ACA was measured by UBM (ACAUBM). Correlations among these parameters and Shaffer's grade based on gonioscopy in the corresponding quadrant were studied. The efficacy of the Pentacam in screening for PAC and PAC suspect was then analyzed by using receiving operator characteristic (ROC) curves and partition analysis. Shaffer's classification (grade 0 to 4) significantly correlated with each of the measurements using both screening devices (P<0.001), and most strongly correlated with ACAUBM. ACAUBM was also significantly correlated with each Pentacam parameter in all subjected eyes with angle widths of grades 0 to 4 (P<0.001), but not grade 2 or less (P>0.05). In screening eyes with PAC and PAC suspect with the Pentacam, the area under the ROC curve was largest (0.943) when ACV was used as the reference, and partition analysis showed that those eyes were most effectively partitioned with an ACD of 2.58 mm using the Pentacam, resulting in 100% sensitivity and 87.1% specificity. The Pentacam has potential for safe, noncontact screening of eyes with PAC and PAC suspect, except for those with plateau iris configurations, based on measurements of the ACV and ACD, but not the ACA.

Anterior segment optical coherence tomography findings of reverse pupillary block after scleral-fixated sutured posterior chamber intraocular lens implantation

To evaluate findings of reverse pupillary block after scleral-fixated sutured posterior chamber intraocular lens (PC IOL) implantation using anterior segment optical coherence tomography (AS-OCT) and report a possible association with postoperative complications. Department of Ophthalmology, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan. Anterior segment OCT was used to evaluate eyes with reverse pupillary block (ie, deep anterior chamber, concave iris configuration, contact between pupil and IOL) after IOL explantation or cataract extraction combined with vitrectomy and scleral-fixated sutured PC IOL implantation. The PC IOL was implanted using an ab externo method in all cases. After 2 scleral flaps were created 180 degrees apart, a straight needle attached to a 10-0 polypropylene suture for IOL fixation was passed through the bed of half-thickness scleral flaps 2.0 mm posterior to the limbus in a direction parallel to the iris. Four eyes (3 patients) were evaluated. Anterior segment OCT showed a concave iris configuration with an increase in anterior chamber depth and anterior chamber angle in all cases. Two eyes had intermittent pupil capture. Laser iridotomy prevented recurrence of reverse pupillary block and pupil capture. Widening of the gap between the inner and outer flaps of the scleral tunnel during reverse pupillary block was seen on AS-OCT in 2 eyes; the widening was associated with wound leakage in 1 eye. Anterior segment OCT showed that reverse pupillary block can occur in eyes with scleral-fixated sutured PC IOLs and cause postoperative pupil capture and scleral tunnel insufficiency.

Syndrome d’iris plateau-like secondaire à une polykystose iridociliaire

The clinical diagnosis of plateau iris most often remains a suspected diagnosis in absence of complementary imaging tests. We report the case of a plateau-like iris configuration resulting from numerous iridociliary cysts and the diagnostic value of ultrasound biomicroscopy (UBM). A 35-year-old Caucasian woman with a family history of PAOG presented asymptomatic high intraocular pressure (IOP) (26mmHg RE, 17mmHg LE). She had a normal deep anterior chamber, a narrow iridocorneal angle with sectoral abnormal insertion of the iris and a normal fundus. Laser peripheral iridotomy was performed. One year later, the patient presented again with elevated IOP in the right eye (25mmHg); hypotensive monotherapy was prescribed. Later she reported eye pain in the evening. Gonioscopy found an iridocorneal contact covering more than 200 degrees in the right eye, with less extensive coverage in the left eye. The hypothesis of plateau iris-like syndrome was suggested because of the failure of the iridotomy and UBM was performed. This confirmed the diagnosis of plateau iris configuration secondary to numerous ciliary body cysts. UBM provides great diagnostic assistance, superior to anterior segment OCT in the diagnosis of plateau iris syndrome, particularly in imaging the ciliary body. The numerous iridociliary cysts can imitate iris plateau syndrome, which explains aggravation over time, depending on their formation. UBM is a highly valuable tool for the diagnosis and the follow-up of this pathology.

Comparative biometric study between plateau iris configuration and primary open angle glaucoma with narrow angle

To investigate biometrically the differences between plateau iris configuration (PIC) eyes and primary open angle glaucoma with narrow angle eyes. A comparative study involving a case series with 20 eyes of 11 plateau iris configuration patients and 45 eyes of 27 primary open angle glaucoma with narrow angle eyes patients was done. The following measurements were taken: corneal curvature, central corneal thickness, anterior chamber depth, lens thickness (LT), axial length (AL), lens thickness and axial length ratio, lens position (LP) and relative lens position (RLP). The plateau iris configuration eyes presented a higher corneal cuvature value than primary open angle glaucoma with narrow angle eyes eyes but not with clinical and statistical difference (P=0.090). The plateau iris configuration eyes demonstrated a higher central corneal thickness, with statistical significance, when compared to primary open angle glaucoma with narrow angle eyes (P=0.010). Statistical significant difference between plateau iris configuration and primary open angle glaucoma with narrow angle eyes was found in axial length (21.69 +/- 0.98 vs. 22.42 +/- 0.89; P=0.003). No significant difference was found when anterior chamber depth (2.62 +/- 0.23 vs. 2.71 +/- 0.31; P=0.078), LT (4.67 +/- 0.36 vs. 4.69 +/- 0.45; P=0.975), LT/AL (2.16 +/- 0.17 vs. 2.10 +/- 0.21; P=0.569), LP (4.95 +/- 0.25 vs. 5.06 +/- 0.34; P=0.164) and RLP (0.23 +/- 0.01 vs. 0.22 +/- 0.14; P=0.348) were evaluated. The eyes with plateau iris configuration presented statistical significantly shorter axial length and higher central corneal thickness than primary open angle glaucoma with narrow angle eyes.

Double Hump Sign in Indentation Gonioscopy is Correlated With Presence of Plateau Iris Configuration Regardless of Patent Iridotomy

A plateau iris is one of the clinical forms of angle closure glaucoma. In patients with a patent iridotomy, the double hump sign detected during indentation gonioscopy has been reported to indicate the existence of a plateau iris configuration. The purpose of this study was to determine whether the double hump sign is correlated with the presence of the plateau iris syndrome regardless of the patency of the iridotomy. Five women and 3 men without a patent iridotomy presented with narrow angles on gonioscopy and a double hump sign on indentation gonioscopy. Ultrasound biomicroscopy (UBM) imaging was performed to determine the etiology of the narrow angle and double hump sign, and to determine the appropriate treatment to prevent the progression of visual field damage. Ten patients with narrow angles and without a double hump sign were also examined by UBM to serve as a control group. All 8 patients who showed double hump sign had a short iris root, which was inserted anterior to the ciliary face, a typical anatomic appearance of a plateau iris. On the other hand, only 1 eye of 10 eyes in control group appeared to have a plateau iris. A double hump sign observed on indentation gonioscopy is strongly correlated with the presence of a plateau iris, and therefore a useful indicator of a plateau iris configuration regardless of the patency of a laser iridotomy. Thus, a plateau iris configuration can be detected without using a UBM in many cases.

Plateau iris

The term plateau iris was first coined in 1958 to describe the iris configuration of a patient. Two years later the concept of plateau iris was published. In 1977, the plateau iris configuration was classically defined as presurgical changes of an eye with a relative normal central anterior chamber depth, flat iris by conventional biomicroscopy, but displaying an extremely narrow or closed angle on gonioscopic examination. On the other hand, the plateau iris syndrome was defined as an acute glaucoma crisis in one eye with a relative normal central anterior chamber depth and patent iridotomy on direct examination, presenting angle closure confirmed by gonioscopic examination after mydriasis. In 1992, the anatomic aspects of plateau iris were studied using ultrasound biomicroscopy. Finally, plateau iris has been considered an anatomic variant of iris structure in which the iris periphery angulates sharply forward from its insertion point and then again angulates sharply and centrally backward, along with an anterior positioning of the ciliary processes seen on ultrasound biomicroscopy. The clinical treatment of plateau iris syndrome is carried out with topical use of pilocarpine. However, the definitive treatment should be fulfilled by performing an argon laser peripheral iridoplasty.

Visualization of Changes of the Iris Configuration After Peripheral Laser Iridotomy in Primary Melanin Dispersion Syndrome Using Optical Coherence Tomography

Pigment or melanin dispersion syndrome is characterized by radial iris transillumination defects, retrocorneal Krukenberg spindle, and dense trabecular pigmentation. Reverse pupillary block has been presumed as one possible pathogenetic mechanism for backward bowing of the iris leading to iris-zonular rubbing and distribution of melanin granules in the anterior chamber. Laser iridotomy is recommended as a treatment to prevent further melanin dispersion and development of pigmentary glaucoma. The effect of Nd:YAG laser iridotomy as a prophylactic and potentially causal treatment in melanin dispersion syndrome can be easily visualized by optical coherence tomography as a fast and noncontact procedure.

Possible Association Between Long Anterior Lens Zonules and Plateau Iris Configuration

To report plateau iris configuration (PIC) in subjects who have the long anterior zonule (LAZ) clinical trait. Two elderly African American males who exhibited LAZ and had partial appositional angle closure persisting after laser iridotomy were imaged with high-resolution ultrasonography to examine for PIC. A third elderly LAZ subject who had narrow angles without closure was also imaged for PIC. Each subject was tested for a serine 163 arginine mutation (S163R) C1q tumor necrosis factor-related protein 5 gene (C1QTNF5/CTRP5) mutation, which may be associated with the LAZ phenotype. All 3 LAZ subjects also had PIC, an unlikely association due to chance alone. None carried the S163R CTRP5 mutation. LAZ and PIC may have association and require study because LAZ might be a useful indicator for an increased likelihood of PIC and risk of angle closure. Mutation other than CTRP5 S163R should also be considered for the LAZ trait, which could be an important phenotypic marker in genetic studies.

Clinical signs and characteristics of pigmentary glaucoma in Chinese

To report the clinical findings in 21 Chinese patients with pigmentary glaucoma (PG). Medical charts of 21 patients diagnosed with PG between 1993 and 2006 at the Beijing Tongren Eye Center were reviewed. From our database, 14 men and seven women were identified as having PG. The mean age of the subjects at the time of the diagnosis was 35.3+/-6.8 years. All but one patient had myopia >-0.5 diopters (D) with a mean spherical equivalent refractive error of -5.38+/-2.56 D. The average intraocular pressure at the initial diagnosis was 34.5+/-10.3 mmHg. All 17 patients with visibility chart documentation of the appearance of the peripheral lens and zonule showed lenticular and/or zonular pigmentation. The irides of all 15 subjects for whom detailed descriptions of the iris configuration were reported were bowed posteriorly. None of the subjects had iris transillumination defects (TIDs) except for trace areas of transillumination in both eyes of one patient. In these Chinese patients with PG, homogeneous increased trabecular pigmentation, dusting of the peripheral lens or zonule with pigment granules, and posterior bowing of the iris were common. Typical spoke-like radial TIDs were not observed.

Optische Kohärenztomographie des vorderen Augenabschnittes bei Glaukom

In recent years, the rapid development of diagnostic optic devices has generated optical coherence tomography (OCT) as a new, non-invasive diagnostic method. With technical progress of the infrared spectrum at 1,310 nm, OCT of the anterior segment also became feasible. With anterior segment OCT different examinations which so far were ruled out by ultrasound in contact manner could be executed in a non-contact technique: pachymetry, goniometry, illustration of iris and lens configuration as well as postoperative results after different glaucoma surgeries such as trabeculectomy, deep sclerectomy and glaucoma drainage devices. Additionally, anterior segment OCT provides an imaging device for experimental approaches in glaucoma. Today two commercially available units are available: SL OCT (Heidelberg Engineering, Heidelberg, Germany) und Visante(R) OCT (Zeiss Meditec, Jena, Germany). For all applications OCT delivered a high inter- and intraobserver reproducibility, is equal to ultrasound in accuracy and involves a higher patient comfort. Within the different applications, a direct comparison with ultrasound technique reveals minor differences depending on the device type. Therefore, it is advised to indicate the device type with all measurements. OCT enables precise, two-dimensional, non-contact imaging of the anterior segment in high resolution. For glaucomatous diseases, anterior segment OCT enlarges and enriches the armamentarium of glaucoma diagnostics and postoperative care of current modern glaucoma surgery.

Morphological changes of the anterior segment after laser peripheral iridotomy in primary angle closure

To study changes in anterior segment morphology after laser peripheral iridotomy (LPI) in primary angle closure (PAC) using anterior segment optical coherence tomography (AS-OCT). LPI was performed on 15 consecutive primary angle closure patients (15 eyes). AS-OCT was used to record the morphology of the anterior segment before and after LPI. The central anterior chamber (AC) depth, the diameter of the pupil, the lens thickness, and the AC volume were measured. The peripheral AC depth and the configuration of iris were also observed qualitatively. The intraocular pressure (IOP) was measured by Goldmann applanation tonometer. The mean central AC depth was 1.939+/-0.228 and 1.970+/-0.235 mm before and after LPI, respectively, increasing by 1.6%, P=0.001. In all eyes but two, the central AC depth increased. The AC volume changed significantly after LPI (73.86+/-14.58 vs 84.14+/-17.45 microl, P<0.001) and it increased in all eyes. The iris flattened and the peripheral AC deepened after LPI in all 15 eyes. The mean IOP was 17.8+/-3.3 and 15.9+/-3.1 mmHg before and after LPI, respectively, P=0.042. The changes of pupil diameter and lens thickness were not statistically significant. LPI leads not only to the increase of peripheral anterior chamber depth and anterior chamber volume but also to an increase of central anterior chamber depth in eyes with primary angle closure.

A Case of Iridoschisis Associated with Plateau Iris Configuration

A Case of Iridoschisis Associated with Plateau Iris Configuration

Visualisation of reverse pupillary block using AC‐OCT in primary pigment dispersion syndrome

Abstract Purpose: To describe morphologic characteristics associated with secondary IOP elevation due to pigment release after pupil dilation in primary melanin dispersion syndrome. Methods: The history of a 49 year old male patient with primary pigment dispersion syndrome and secondary ocular hypertension is described. Besides detailed ophthalmologic examination including slit lamp biomicroscopy, gonioscopy as well as IOP and Laser‐Flare measurement (KOWA FC‐1000; Kowa, Tokyo, Japan) before and after pupil dilation, anterior segment optical coherence tomography was performed before and after Nd:YAG laser iridotomy and in medical miosis. Results: After pupil dilatation IOP increased up to 46 mmHg at the right eye but no IOP elevation was recognised at the left eye. Measurement by Laser‐Flare Cell Meter revealed no cells in undilated state but 13.4 cells/ 0.075 μl at the right and 4.0 cells/ 0.075 μl at the left eye after mydriasis. Nd:YAG laser iridotomy was recommended for the right eye to the patient recently. Iris configuration detected by OCT demonstrates a concave shape before iridotomy more pronounced temporal than nasal which resolves after application of pilocarpin as well as after performance of Nd:YAG laser iridotomy. Conclusions: The effect of Nd:YAG laser iridotomy as a prophylactic but potentially causal treatment in pigmentary glaucoma can be easily visualized by OCT as a fast and non‐contact procedure.

Optical coherence tomography in anterior segment imaging

To evaluate the ability of optical coherence tomography (OCT), designed primarily to image the posterior segment, to visualize the anterior chamber angle (ACA) in patients with different angle configurations. In a prospective observational study, the anterior segments of 26 eyes of 26 patients were imaged using the Zeiss Stratus OCT, model 3000. Imaging of the anterior segment was achieved by adjusting the focusing control on the Stratus OCT. A total of 16 patients had abnormal angle configurations including narrow or closed angles and plateau irides, and 10 had normal angle configurations as determined by prior full ophthalmic examination, including slit-lamp biomicroscopy and gonioscopy. In all cases, OCT provided high-resolution information regarding iris configuration. The ACA itself was clearly visualized in patients with narrow or closed angles, but not in patients with open angles. Stratus OCT offers a non-contact, convenient and rapid method of assessing the configuration of the anterior chamber. Despite its limitations, it may be of help during the routine clinical assessment and treatment of patients with glaucoma, particularly when gonioscopy is not possible or difficult to interpret.