Thin Irises Research Articles

Characterization of the anterior segment in Trisomy 21-associated cataract using ultrasound biomicroscopy

BackgroundobjectivesTo compare the structural anatomy of the anterior segment in pediatric Trisomy 21 (T21) subjects with and without cataracts to age-matched controls. DesignProspective case-control study. Participants40 subjects (57 eyes) age 0–25 years old (9.1 ± 10.6 years). MethodsThis prospective case-control study evaluated anterior segment measurements from ultrasound biomicroscopy (UBM) imaging on 342 images. ResultsAmong persons with T21 cataract, the iris was significantly thinner than T21 individuals without cataract (0.28 vs 0.32 mm, p = 0.0181). T21/cataract subjects also had significantly thinner lenses than subjects without cataract, regardless of whether they have T21 or are controls (3.1 mm vs 3.5 mm, p = 0.0074).Thinner lens (<3.5 mm) was insignificantly associated with increased odds of cataract (OR = 9.5 [0.872,104], p = 0.065). Thinner iris (<0.32 mm) was associated with increased odds of cataract (OR = 8.4 [1.188, 59.273], p = 0.033). ConclusionsThese findings support the hypothesis that subtle quantitative anatomic variants are present in the anterior eye of individuals with T21. Specific anatomic variants are unique to the presence of cataract among subjects with T21.

The correlation of anterior segment structures in primary congenital glaucoma by ultrasound biomicroscopy with disease severity and surgical outcomes

PurposeTo evaluate the anterior segment structures using ultrasound biomicroscopy (UBM) in primary congenital glaucoma (PCG) and explore their correlation with disease severity and surgical outcomes.MethodsClinical information of PCG patients who underwent UBM prior to their first glaucoma surgeries from September 2014 to March 2021 were reviewed. The study included 214 UBM images of 154 PCG eyes and 60 fellow unaffected eyes. Anterior segment characteristics were analyzed. UBM parameters, including the iris thickness (IT) at variant distances from the pupil edge and iris root, anterior chamber depth (ACD), and pupil diameter (PD), were compared between two groups and their relationship with clinical factors and surgical outcomes were analyzed in PCG eyes.ResultsPCG eyes had unclear scleral spur, thin iris, wide anterior chamber angle, deep anterior chamber, rarefied ciliary body, elongated ciliary processes, and abnormal anterior iris insertion. ITs were thinner, ACD was deeper, and PD was larger in PCG eyes than fellow unaffected eyes (all P < 0.001). In PCG eyes, thinner ITs correlated with bilateral involvement and earlier age at presentation, and larger PD correlated with earlier age at presentation (P = 0.030) and higher intraocular pressure (P < 0.001). Thinner IT2 (P = 0.046) and larger PD (P = 0.049) were identified as risk factors for surgical failure.ConclusionUBM is a powerful technique to exam anterior segment structures in PCG. The anatomical features are associated with disease severity and surgical outcomes, providing essential clinical insights.

Laser Iridotomy for Pupillary Block in Children with Endogenous Uveitis

Objective. Development of a differential approach to laser iridotomy in children with endogenous uveitis considering iris characteristics and the reaction of children’s eyes to different laser types.Patients and methods. Thirty-six laser iridotomies were conducted in 36 children aged 8–16 years with pupillary block. Nidek YAG laser was used in YAG (1064 nm) and SLT (532 nm) modes.Results. The frequency of hemorrhagic complications during surgery decreased to 19.4 % since 2009. The frequency of exudative reactions and proliferative syndrome with closure of laser coloboms in 1-6 months after surgery decreased to 33.3 % (25.7 % and 40.9 % respectively).Conclusion. We recommended the patented differential approach for effective nontraumatic laser iridotomy in children with endogenous uveitis. In a thin iris single-stage YAG laser perforation should be performed in maximum bombe and multiple perforation in cases of multi-chamber bombe. In a dense thick iris or in cases of former iridotomy closure two-stage approach should be performed. First, circular coagulation should be done in the form of a ring or spot at the site of the planned coloboma. Second, YAG-laser perforation should be done in 10–14 days. The iris vessels topography, reflexogenic zones, and the peculiarities of the iris reactions to the lasers in children with endogenous uveitis should be considered when choosing a place for a coloboma. The use of thermal coagulating lasers should be limited, especially on thin irises. Active anti-inflammatory therapy and eye monitoring are necessary after laser surgery. The differential approach is safe, effective, and can be recommended for implementation in the practice of pediatric ophthalmology.

Implantation of ArtificialIris, a CustomFlex® iris prosthesis, in a trauma patient with an Artisan lens

Purpose: To evaluate probable complications of ArtificialIris implantation with iris-fixated intraocular lens.&#x0D; Method: Development of photophobia, glare, and psychological strain during face-to-face communication in a 23-year-old man with a widespread traumatic iris defect terminate to make a decision for performing implantation an ArtificialIris (HumanOptics, Erlangen, Germany) under the remnant iris without removing the patient’s existing Artisan lens.&#x0D; Results: Without any intraoperative or postoperative complications, the patient’s visual acuity increased by one line, the endothelial cell loss was comparable with the cell loss associated with standard cataract surgery, and the anterior chamber depth and anterior chamber anatomy did not change. At the final follow-up examination, the mean intraocular pressure (IOP) did not differ from baseline, and we achieved high level of patient satisfaction and subjective vision improvement. We discuss the particular importance of considering the patient’s expectations, the appropriate measurements, ways to perfect color evaluation, and the types of ArtificialIris products.&#x0D; Conclusion: The implantation of the ArtificialIris in patients with aphakic iris-supported lenses (i.e., preexisting Artisan lenses) is a feasible approach and a useful option for patients with thin irises and iris hypoplasia who are at risk of subluxation or the dislocation of the PCIOL as well as those with sclerally fixed PCIOLs.

Associated factors of acute primary angle closure glaucoma in a sub-group of Chinese people: comparison between attack eyes and normal controls

Acute primary angle closure glaucoma (APACG) is an ophthalmic emergency that may lead to irreversible blindness. Although efforts were made to control intraocular pressure, disease progression still existed. Anterior segment optical coherence tomography (AS OCT) may provide a new insight into mechanism of APACG. In order to seek out associated factors by AS OCT, We compared anterior segment parameters between 74 APACG and 48 normal eyes. Analysis of variance, principle component analysis and logistic regression were used. APACG group had more women (75.7% vs 47.9%, p = 0.002), smaller anterior chamber (anterior chamber depth, ACD; anterior chamber area, ACA; all p = 0.001), narrower angle (AOD500, AOD750, angle opening distance at 500um and 750um; TISA500, TISA750, trabecular-iris space area at 500um and 750um; ARA500, ARA750, angle recess area at 500um and 750um; all p < 0.001), thinner iris (iris thickness at 750um, IT750; maximum of iris thickness, ITMAX; all p < 0.001), larger iris area (IA, p < 0.001) and lens vault (LV, p = 0.005). Principle component extracted were AOD500, AOD750, TISA500, TISA750, ARA500, ARA750, IA, PD (pupillary diameter), ACD, ACA and IT750. After adjusting for confounding factors, AOD750 (b = 12.40 ± 2.56, p < 0.001), IT750 (b = 10.50 ± 3.45, p = 0.002) and IA (b = −1.56 ± 0.77, p = 0.044) were significantly associated with occurrence of APACG.

Factors influencing the pupillary light reflex in healthy individuals.

To determine the ocular anatomical factors influencing the pupillary light reactions to different wavelengths of light, measured with chromatic pupillometry. Community-based, cross-sectional study including subjects with normal ocular health (ages 50-79years). Direct pupillary responses to continuously increasing irradiances (6.8 to 13.8 log photons cm(-2) s(-1)) of red (631nm) and blue (469nm) light were measured, using a dedicated infrared pupillometer. All subjects underwent swept source optical coherence tomography (SS-OCT, CASIA SS-1000, Tomey Corporation, Nagoya, Japan) and noncontact partial coherence laser interferometry (Lenstar LS900, Haag-Streit AG, Switzerland). Univariate and multivariable regression analyses were performed to determine the anatomical features influencing pupillographic parameters. Among the 177 included subjects, 167 (94.4%) were Chinese and 116 (65.5%) female. The average baseline pupil diameter in darkness (β = -0.080, p < 0.001) and the amplitude of the relative pupillary constriction (β = -0.233, p = 0.006) to blue light decreased with age. The amplitude of pupillary constriction was significantly larger in patients with a thinner iris, in response to stimulation with blue (β = -0.321, p < 0.001) and red light (β = -0.336, p < 0.001). Other ocular parameters (i.e., lens vault, anterior chamber depth width, iris volume, iris curvature, and lens thickness) were not significantly associated with pupillometric outcomes. The amplitude of the pupillary light constriction to chromatic photic stimuli is reduced with increasing age and iris thickness in subjects with normal ocular health, a finding which needs to be integrated into future pupillometric studies.

Anterior segment changes after pharmacologic mydriasis using Pentacam and optical coherence tomography in angle closure suspects.

To compare the dynamic changes of anterior segment parameters especially iris morphology induced by pharmacologic mydriasis between angle closure suspects and normal controls. The study group comprised 19 eyes of 19 angle closure suspects and 19 eyes of 19 age- and sex-matched normal open-angle eyes. Pentacam and optical coherence tomography measurements before and 30min after instillation of compound tropicamide eye drop were performed and compared. Biometric evaluations of iris tomography and anterior chamber angle were estimated by a customized image-processing software. Baseline axial length, iris cross sectional area and volume did not differ significantly between angle closure suspects and normal controls. Angle closure suspects had smaller pupil size, narrower anterior segment dimension and axial length, thinner iris with greater curve in comparison with normal controls. Pharmacologic mydriasis led to significant increments in iris thickness at 750 µm, anterior chamber depth and volume, whereas significant decrements in iris curve, cross sectional area and volume in both groups. Angle opening distance at 500 µm was increased significantly in normal controls (from 0.465±0.115 mm to 0.539±0.167 mm, P=0.009), but not in angle closure suspects (from 0.125±0.100 mm to 0.145±0.131 mm, P=0.326). Iris volume change per millimeter of pupil dilation (ΔIV/ΔPD) decreased significantly less in angle closure suspects than normal controls (-2.47±1.33 mm(2) vs -3.63±1.58 mm(2), P=0.019). Linear regression analysis showed that the change of angle opening distance at 500 µm was associated most with the change of central anterior chamber depth (β=0.841, P=0.002) and ΔIV/ΔPD (β=0.028, P=0.002), followed by gender (β=0.062, P=0.032). Smaller iris volume decrement per millimeter of pupil dilation is related significantly with the less anterior angle opening in angle closure suspects after pharmacologic mydriasis. Dynamic iris change may be as a prospective indicator of iris compressibility and angle closure glaucoma.

Baseline Anterior Segment Parameters Associated with the Long-term Outcome of Laser Peripheral Iridotomy

Purpose: To investigate the baseline anterior segment (AS) parameters determined by AS optical coherence tomography (AS OCT) in the prediction of long-term outcome of laser peripheral iridotomy (LPI) in primary angle closure suspect (PACS) eyesMethods: Participants were imaged at pre-LPI and at 2 weeks and 3 years post-LPI using AS OCT. Based on these images, anterior chamber depth (ACD), iris curvature (IC), anterior chamber width (ACW), iris thickness at 750 µm from the scleral spur (IT750), lens vault (LV), and iris area (IA) were estimated using the Image J software (version 1.46). Proportional change (%) in angle opening distance at 750 µm from the scleral spur (AOD750) was used as an outcome measure for LPI. Univariate and multivariate regression analyses were performed to evaluate baseline AS parameters associated with changes in AOD750.Results: A total of 39 PACS eyes were included. At 2 weeks post-LPI, thinner IT750 (p = 0.006) and less AOD750 (p < 0.001) at baseline were related to a greater AOD750 change. When assessed at 3 years post-LPI, thinner IT750 (p = 0.039) and less AOD750 (p = 0.003) at baseline were associated with a greater AOD750 change.Conclusions: Thin peripheral iris and less AOD750 at baseline were associated with greater changes in longitudinal assessment after LPI. PACS eyes with thick peripheral iris at baseline showed less AOD750 change at both early and late follow up after LPI; therefore, such eyes should be followed with caution despite successful LPI.

Anterior Segment Optical Coherence Tomography Analysis of Clinically Unilateral Pseudoexfoliation Syndrome: Evidence of Bilateral Involvement and Morphologic Factors Related to Asymmetry

To compare the morphology of the anterior chamber angle (ACA) and iris in eyes with pseudoexfoliation (PEX) syndrome to that of their clinically unaffected fellow eyes and normal control eyes. Forty-two patients with unilateral PEX syndrome and 42 normal subjects were studied. Eyes were separated into those with PEX, their clinically unaffected fellow eyes, and normal eyes. The dark-light changes of the ACA and iris were documented by anterior segment optical coherence tomography (AS-OCT) video recordings. The nasal ACA parameters including the angle opening distance at 500 μm (AOD500), the trabecular-iris space at 500 μm (TISA500), and the trabecular-iris angle at 500 μm (TIA500); anterior chamber depth (ACD); iris-lens contact distance (ILCD), and iris configuration were analyzed with the built-in software and a customized program. The ACA parameters were not significantly different among all three groups in the dark. The PEX eyes had significantly smaller ACA parameters than their fellow eyes and normal control eyes in the light. PEX eyes also had significantly shallower ACD, longer ILCD, and greater iris convexity (both in dark and light), and thinner iris (in dark) than their fellow eyes. The fellow eyes had significantly lower ACD both in the dark and light, and smaller angle opening distance at 500 μm and ILCD in the light than normal controls. There were no significant differences in the iris area among the three groups. Differences in the anterior segmental morphology are present between PEX and fellow eyes. These disparities may be related to the asymmetry in patients with the unilateral PEX syndrome.

Ultrasound Biomicroscopic Configurations of the Anterior Ocular Segment in a Population-Based Study: The Kumejima Study

To characterize quantitatively the configuration of the anterior ocular segment with ultrasound biomicroscopy (UBM) in a population-based setting. Cross-sectional study. Ten percent of 4632 residents aged > or =40 years of Kumejima, an island off southwest Japan, were randomly selected. We performed UBM under light and dark conditions in the 4 quadrants of the right eyes. The anatomic landmarks on the anterior ocular segment UBM images were identified by 1 examiner to quantify the peripheral anterior chamber depth (ACD), location of the ciliary body, and iris thickness. Angle-opening distance at 250 and 500 microm from the scleral spur (AOD250, AOD500), trabecular-iris angle (TIA), trabecular-ciliary process distance (TCPD), thickness of the iris (ID), trabecular-anterior iris surface angle (TAIA), trabecular-posterior iris surface angle (TPIA), trabecular-ciliary angle (TCA), and thickness of iris measured at 1000, 2000, and 3000 microm (IT1000, IT2000 and IT3000). The AOD500 averaged 0.267+/-0.138 (mean +/- standard deviation) and 0.202+/-0.116 mm under light and dark conditions, respectively; TIA 22.2+/-10.0 and 17.0+/-8.9 degrees; TCPD 0.755+/-0.165 and 0.748+/-0.152 mm; and ID 0.412+/-0.053 and 0.457+/-0.062 mm. The peripheral ACD was deepest temporally, then nasally, then inferiorly, and then superiorly (P<0.05, post hoc test). The position of the ciliary body was deepest nasally, then temporally, then inferiorly, and then superiorly (P<0.05). Iris thickness did not differ significantly among the quadrants. Older subjects had a shallower peripheral ACD, more anteriorly located ciliary body, and thinner iris (analysis of covariance, P<0.015). The peripheral ACD was deeper and the ciliary body was located more deeply in men than women (P<0.05), although no intergender differences in iris thickness were seen (P>0.1). Hyperopia, short axial length, and shallow central ACD were significantly correlated with shallower peripheral ACD, anteriorly located ciliary body, and thinner iris (P<0.05). Elevated intraocular pressure was associated with a shallow peripheral ACD (P< or =0.043). There are significant associations of the peripheral ACD, location of the ciliary body, and iris thickness with age, gender, refractive error, axial length, and intraocular pressure.

Analysis of Propagation Characteristics of Circular Corrugated Waveguides Using Coupled Integral Equation Technique

The circular corrugated waveguides are useful as slow-wave circuits in traveling-wave tube amplifiers, linear accelerators, and backward-wave oscillators. The study of propagation characteristic of TM waves in circular corrugated waveguides is important for applications such as those above and is the focus of this paper. The propagation characteristics are computed using the coupled integral equation technique (CIET). Both infinitesimally thin irises and thick irises are analyzed. The results for the infinitesimally thin irises are compared with those published in the open literature, where the mode matching technique was used. The results for the thick irises computed using CIET are validated using the three-dimensional electromagnetic (EM) simulators based on finite element method (FEM) and finite integration technique (FIT).

Ultrasound Biomicroscopy in the Subtypes of Primary Angle Closure Glaucoma

To evaluate the anterior segment parameters in the subtypes of primary angle closure glaucoma (PACG) using ultrasound biomicroscopy. Five groups, each comprising 30 consecutive patients, diagnosed to have subacute PACG, acute PACG, chronic PACG, primary open angle glaucoma (POAG), and healthy controls were included in the present study. All patients underwent slit-lamp biomicroscopy, direct ophthalmoscopy, 90D fundus examination, gonioscopy, applanation tonometry, visual field testing, A-scan biometry, and ultrasound biomicroscopy (UBM). The anterior segment parameters recorded included: trabecular-iris angle, angle opening distance, trabecular ciliary process distance, and the iris thickness among other parameters. On ultrasound biomicroscopy the trabecular iris angle of control and POAG groups was more than all the subtypes of PACG (P < 0.001). The trabecular iris angle of subacute PACG (P < 0.001) and chronic PACG (P = 0.003) was more than acute PACG. Angle opening distance of controls and POAG group was significantly more than acute PACG and chronic PACG (P < 0.001). The trabecular ciliary process distance of POAG group and controls was more than subacute PACG, acute PACG, and chronic PACG. The trabecular ciliary process distance of subacute PACG (P < 0.001) and chronic PACG (P < 0.001) was more than acute PACG. Eyes with acute PACG had the least iris thickness at the three different positions tested. There was a positive correlation between the anterior chamber angle (trabecular iris angle) and the following parameters: trabecular ciliary process distance, angle opening distance, anterior chamber depth, and the axial length (r = 0.57). Eyes with primary angle closure glaucoma have a thinner iris with a shorter trabecular iris angle, angle opening distance, and trabecular ciliary process distance. The eyes with acute primary angle closure glaucoma have the narrowest angle recess.

Investigation of boundary algorithms for multiresolution analysis

An investigation on the multiresolution time-domain (MRTD) method utilizing different wavelet levels in one mesh is presented. Contrary to adaptive thresholding techniques, only a rigid addition of higher order wavelets in certain critical cells is considered. Their effect is discussed analytically and verified by simulations of plain and dielectrically filled cavities with Daubechies' and Battle-Lemarie orthogonal, as well as Cohen-Daubechies-Feauveau (CDF) biorthogonal wavelets, showing their insufficiency unless used as a full set of expansion. It is pointed out that improvements cannot be expected from these fixed mesh refinements. Furthermore, an advanced treatment concerning thin metallization layers in CDF algorithms is presented, leading to a reduction in cell number by a factor of three per space dimension compared to conventional finite difference time domain (FDTD), but limited to very special structures with infinitely thin irises. All MRTD results are compared to those of conventional FDTD approaches.

Field-singularity correction in 2-D time-domain Haar-wavelet modeling of waveguide components

A time-domain Haar-wavelet-based modeling technique has been applied to two-dimensional waveguide problems including discontinuities. The field singularity at discontinuities such as edges and corners of conductors is corrected by quasi-static field approximation. Combination of quasi-static correction and wavelet modeling significantly improves the computational efficiency compared to conventional time-domain analysis techniques. The proposed technique was applied to waveguides perturbed by thin and thick irises and also iris-coupled waveguide filters. The computational efficiency of the technique is demonstrated by examining the convergence of the results obtained with different discretizations.

Efficient FDTD modeling of irises/slots in microwave structures and its application to the design of combline filters

A new methodology is proposed for the computationally efficient, numerically stable, and accurate finite difference time-domain (FDTD) simulation of microwave structures with electrically thin irises and slots. The proposed method is based on the hybridization of Yee's standard FDTD scheme with Pade approximations of the electromagnetic properties of the irises/slots. Through the use of rigorous modal expansions for the description of the fields in the waveguide sections formed by the irises and slots, highly accurate rational function approximations of their transmission and reflection properties are obtained. These transfer functions are then incorporated directly in the FDTD algorithm through their corresponding z-transform expressions. Combined with the matrix valued multivariate Pade approximation, the proposed method provides a suitable design tool for combline filters and manifold multiplexes for satellite and wireless communication systems. Results are presented to demonstrate the validity and accuracy of the proposed methodology.

Accurate calculation of coupling coefficients of irises/slots in combline filters

A methodology is presented for computationally efficient and accurate prediction of the coupling coefficients of electrically thin irises and slots in combline filters. The proposed methodology utilises a rational function approximation with adaptive polynomial order identification to fit the frequency-domain response of the structure. Thus, the calculation of the coupling coefficients reduces to a polynomial root-searching problem. The key attributes of the proposed algorithm are its efficiency, its high frequency resolution, and its avoidance of spurious roots due to improper choice of polynomial orders. Examples are presented to demonstrate the validity and accuracy of the proposed approach.

Expansion of a frequency tuning band in a gyrotron with coupled cavities

An electron frequency tuning band of a conventional high-Q cavity gyrotron approximately coincides with the unloaded cavity bandpass which usually does not exceed 0.1%. To expand the frequency tuning band we introduce a gyrotron with an RF circuit that consists of two coupled circular cavities separated by a thin iris. A nonlinear self-consistent gyrotron theory predicts a saturated efficiency of 18% and a tuning band of 1.1%. An experimental study of an X-band tube operating in the TE011 mode was carried out to test the gyrotron with the coupled cavities concept. Measurements of gyrotron performance showed a 0.96% tuning band—a tenfold increase over that of an ordinary gyrotron. Simulation results are in a good agreement with the experimental data.

A unified approach to the analysis of a category of H-plane discontinuities

Based on the mode matching method, the generalized scattering parameters including the fundamental and higher order modes (multi-modes) are obtained for the discontinuity interface of a category of waveguide H-plane discontinuities. Then by using a general port-connection order-decrease method raised by the author, the whole discontinuity including the two interfaces and the intermediate part of finite length or zero length (as is the case for very thin inductive windows or irises) can be combined into one network, and the generalized scattering parameters of this network can be obtained from which the scattering parameters of the fundamental mode can be extracted. If needed, the equivalent circuit parameters can be calculated directly from the scattering parameters. Examples are given to show the validity and versatility of this new method for dielectric filled waveguide, inductive iris and/or window, E-plane metal and/or finline insert, and even the offset E-plane finline insert, etc.. Multiple inserts, windows and irises can also be analysed.

Analytical solution and frequency extraction of iris problems in waveguide by separation of variables

The field nearby a thin iris discontinuity can be found in an exact manner by solving the wave equation in an appropriate coordinate system. To this end, it is necessary to select a coordinate system that fits the iris boundary. As an example, capacitive and inductive irises in rectangular waveguides have been solved by considering the Helmholtz equation in the elliptic-cylinder coordinate system. The presence of the waveguide environment is then enforced either by using the aperture field solution in a variational expression of the equivalent shunt susceptance or by taking images. The advantage of the new solution is that a single term solution, apart from being very accurate and numerically efficient, also contains the correct frequency dependence; thus providing results over the entire band. Moreover, wide-band equivalent circuits with frequency independent elements of the Foster's canonical form descend directly from the field analysis.

A parametric study on the normalized susceptance of cascaded multiple and symmetrical irises using a modified break-point technique

A parametric study on the normalized susceptance of cascaded multiple and symmetrical irises is presented in this article. Numerical experiments have been conducted based on a modification to the Masterman's break-point technique for an infinitely thin inductive iris. Results for potential applications, such as in shielding structure design, have been obtained for cascaded single, two, and four symmetrical inductive iris structures. © 1996 John Wiley & Sons, Inc.