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Assessment of Anterior Chamber Angle Using Visante OCT, Slit-Lamp OCT, and Pentacam
Abstract
To assess and compare the anterior chamber angle (ACA) by different anterior segment imaging techniques.
Forty healthy eyes of 40 normal subjects were recruited and 3 consecutive measurements of ACA were determined prospectively utilizing Visante optical coherence tomography (OCT), slit-lamp OCT (SL-OCT), and Pentacam. Statistical significance of interdevice differences between measurements was evaluated by Wilcoxon signed rank test and Bland-Altman analysis. The repeatability of 3 consecutive measurements was analyzed by repeated measured analysis of variance.
Mean nasal and temporal ACA were detected as 31.2+/-8.7 and 32.1+/-8.5 degrees by Visante OCT; 41.6+/-5.9 and 41.8+/-5.2 degrees by Pentacam; and 42.9+/-10.0 and 43.3+/-10.1 degrees by SL-OCT. All devices displayed a high intrasession repeatability (Scheffe multiple comparison, p>0.05). ACA detected by Visante OCT were found significantly different from ACA calculated by Pentacam and SL-OCT (p<0.05). On the other hand, ACA data obtained by Pentacam and SL-OCT were found to be statistically similar (p>0.05).
Although noncontact ACA measurements using all modalities were easy to handle and demonstrated good repeatability in healthy participants, the tested devices were not regarded as comparable. Hence, the clinician should take the different modalities into consideration during ACA assessment using various devices.
... Dinç ve arkadaşları İKA değerlendirilmesi için Pentacam, Slit-lamp OKT ve Visante OKT'yi kullanmışlar, her cihaz kendi içerisinde yüksek tekrarlanabilirliğe sahip olmasına rağmen, Visante OKT sonuçlarını diğer cihazlara göre daha düşük saptamışlardır (15). Bizim çalışmamızda ÖKGA hem nazal hem temporal kadranlarda Spectralis'te daha dar bulunmuştur. ...
To evaluate the compatibility and consistency of iridocorneal angle (ICA) measurements detected with Pentacam (Oculus, Inc., Germany), RTVue (Optovue Inc., Freemont, USA) and Spectralis (Heidelberg GmbH, Germany) devices. Twenty-two eyes of 22 healthy participants were evaluated retrospectively. In Pentacam, measurements were taken automatically in each eye at 3 and 9 o'clock (nasal and temporal), and trabecular-iris angle values were recorded. In RTVue and Spectralis anterior segment optical coherence tomographies, the parameters of anterior chamber recess angle (ACA), scleral spur angle (SSA) and angle opening distance from 500 μm distance (AOD500) were recorded. All measurements were taken under similar lighting conditions. Cases under the age of 18 years, history of previous ocular surgery orophthalmic laser, refractive errors that may alter ICA measurements, fixation abilities, insufficient anterior segment image quality or cases with intraocular pressure above 21 mmHg during examinations were excluded from the study. All devices were found to be consistent with each other in terms of ACA-SSA in both nasal and temporal quadrants (for temporal-nasal quadrants respectively ICC; 0.871, 0.837; 0.872, 0.839). According to the Bland-Altman analysis, when Pentacam is taken as the reference device, as the ACA value widens, both RTVue and Spectralis measurements show higher agreement. While ACA degrees were statistically similar in both the nasal and temporal quadrants for Pentacam and RTVue, it was found narrower in Spectralis (for nasal quadrant p=0.003, for temporal quadrant p=0.007). Although there was a good consistency between the AOD500 values between RTVue and Spectralis, (for temporal quadrant ICC: 0.825, for nasal quadrant ICC: 0.882) it was determined that Spectralis showed higher results than RTVue (p˂0.001). Although Pentacam, RTVue and Spectralis measurements are found to be consistent with each other for the evaluation of ICA, considering the differences between the devices of both ACA-SSA and AAU500 values, it may be considered that the relevant devices may not be used inter changeably in patient follow-ups.
... [21][22][23]73 With Pentacam, the device is unable to view the angle recess and scleral spur and hence, cannot directly measure the anterior chamber angle, providing only approximations. [74][75][76] Moreover, both previous studies reported angle parameters only in 1 postoperative visit and did not provide any data on the time course of changes in the angle parameters. In the current study, we demonstrated angle widening following surgery in both surgical groups with a more tremendous statistically significant increase in the "Phaco" group. ...
Prcis:
We used anterior segment optical coherence tomography to investigate anterior chamber angle in primary angle-closure glaucoma (PACG) eyes following phacoemulsification and phacotrabeculectomy. Angle widening was significantly greater after phacoemulsification up to 6 months after the surgery.
Purpose:
To compare anterior chamber angle following 2 common surgeries for PACG.
Methods:
One hundred ten glaucoma patients were evaluated in this single center, prospective, randomized clinical trial. Those with concomitant PACG and senile cataract and without a history of ocular surgery, trauma, or chronic miotic use were recruited. Monocular patients were also excluded. Finally, 52 eligible subjects were randomly assigned to phacoemulsification ("Phaco" group, 25 eyes) or phacotrabeculectomy ("Combined" group, 27 eyes) surgeries. A swept-source, anterior segment optical coherence tomography device (CASIA SS-1000 OCT) was used to image the anterior segment. Mask graders used the images to measure the following parameters before and 1 week, 1 month, and 6 months after surgery: angle opening distance at 500 µm, trabecular iris surface area at 500 µm, and trabecular iris angle at 500 µm.
Results:
There was no significant difference between study groups regarding best-corrected visual acuity, intraocular pressure (IOP), and the number of glaucoma medications in preoperative or postoperative visits (P>0.076). Also, the measured angle parameters were not statistically significantly different between the 2 groups before surgery (P>0.123). After surgery, all measured parameters were significantly increased in both groups (P<0.0001). At the 6-month follow-up, nasal angle opening distance at 500 µm was 0.383±0.027 vs. 0.349±0.017, trabecular iris surface area at 500 µm was 0.141±0.007 vs. 0.125±0.005, and trabecular iris angle at 500 µm was 40.1±12.9 vs. 34.6±3.1 in Phaco and Combined groups, respectively (P<0.0001 for all).
Conclusions:
Anterior chamber angle widening by anterior segment optical coherence tomography was observed in PACG patients following surgery and was significantly greater after phacoemulsification compared with combined phacotrabeculectomy at all time points. Similar IOP and medication burden were noted for up to 6 months as secondary outcomes. The contribution of angle changes to the IOP-lowering effect of phacoemulsification in PACG eyes needs further study.
... Pentacam anterior segment parameters: anterior chamber depth (ACD), anterior chamber volume (ACV), and anterior chamber angle (ACA) (Tables 3 and 4). Agreement found between iridocorneal angle measurements of AS-OCT and Pentacam (degrees) is only moderate and low, as other authors previously reported [21,37]. Values obtained with these two different methods are not interchangeable: Bland-Altman figures show that the Pentacam tends to overestimate the measurements of narrow angles and underestimate that of open angles in comparison with OCT measurements as others found [21]. ...
Purpose
To evaluate diagnostic capacity for occludable anterior chamber angle detection with anterior segment optical coherence tomography (AS-OCT) and Pentacam.
Methods
Observational cross-sectional study with AS-OCT and Pentacam. AS-OCT measures: angle opening distance from Schwalbe line (SL) perpendicular (AOD-SL-Perp) and vertical to iris (AOD-SL-Vert), and iridotrabecular angle (ITA). Pentacam measures: anterior chamber depth (ACD), anterior chamber volume (ACV), and anterior chamber angle (ACA). We analysed Spearman’s correlation with gonioscopic classification. Area under receiver operating characteristic curves (AUCs) for occludable angle detection were compared. Agreement between iridocorneal values of methods was evaluated.
Results
Seventy-four left eyes of 74 patients. Correlation between temporal AS-OCT and gonioscopy: 0.83 (p < 0.0001) AOD-SL-Perp temporal, 0.82 (p < 0.0001) AOD-SL-Vert temporal, and 0.69 (p < 0.0001) ITA temporal. Correlation between AS-OCT nasal and gonioscopy: 0.74 (p < 0.0001) AOD-SL-Perp nasal, 0.74 (p < 0.0001) AOD-SL-Vert nasal, and 0.70 (p < 0.0001) ITA nasal. Correlation of Pentacam with temporal gonioscopy: 0.57 (p < 0.0001) ACD, 0.56 (p < 0.0001) ACV, and 0.63 (p < 0.0001) ACA. Correlation of Pentacam with nasal gonioscopy: 0.47 (IC 0.27–0.73, p < 0.0001) ACD, 0.49 (p < 0.0001) ACV, and 0.56 (CI 0.38–0.7, p < 0.0001) ACA. AS-OCT AUCs: AOD-SL-Perp temporal 0.89 (CI 0.80–0.95), AOD-SL-Vert 0.87 (CI 0.77–0.94), ITA temporal 0.88 (CI 0.78–0.94), AOD-SL-Perp nasal 0.83 (CI 0.72–0.91), AOD-SL-Vert nasal 0.87 (CI 0.77–0.94), and ITA nasal 0.91 (IC 0.81–0.96). Pentacam AUCs: ACD 0.76 (CI 0.64–0.85), ACV 0.75 (CI 0.63–0.84), and ACA 0.84 (CI 0.74–0.92). No statistical differences between different AUCs. Intraclass correlation coefficient (ICC) of ACA (Pentacam) with ITA temporal (AS-OCT) 0.59 and with nasal ITA nasal (AS-OCT) 0.65.
Conclusion
Both systems show high capacity for non-contact occludable angle detection. But agreement between methods is moderate or low.
... Ophthalmic Res 2021;64:732-739 DOI: 10.1159/000510924 for the early diagnosis and treatment of PACG. Many techniques, including slit-lamp microscopy [3], gonioscopy [4], anterior segment optical coherence tomography (AS-OCT) [5], and ultrasound biomicroscopy (UBM) [6], have been used for assessing ACA. UBM is particularly important because its resolution and penetration are good. ...
Introduction:
Evaluating the anterior chamber angle (ACA) is important for the early diagnosis and treatment of primary angle-closure glaucoma. The assessment of ultrasound biomicroscopy (UBM) images usually requires well-trained ophthalmologists and screening for patients with narrow ACA is usually time- and labor-intensive. Therefore, the automatic assessment of UBM could be cost-effective and valuable in daily practice.
Objective:
To develop an automatic method for localizing and classifying ACA based on UBM images.
Methods:
UBM images were collected and a coarse-to-fine method was used to localize the apex of the angle recess. By analyzing the grayscale features around the angle recess, closed angles were identified, and the rest were then classified as open or narrow angles, based on the degree of ACA. Using manual classification as the reference standard, the overall accuracy, sensitivity, specificity, and balanced accuracy of the automatic classification method were evaluated.
Results:
A total of 540 UBM images from 290 participants were analyzed. Using these UBM images and the proposed method, the ACA was classified as open, narrow, or closed. During processing, the method localized the angle recess with 95% accuracy. The overall accuracy of the ACA classification was 77.8%, and the specificity and sensitivity of our method were 85.8% and 81.7% for angle closure; 88.9% and 75.6% for open angles; 91.9% and 76.1% for narrow angles, respectively.
Conclusions:
Our method of automatic angle localization and classification based on UBM images is feasible and reliable. The automatic classification of ACA provides a basis and reference for future studies.
... reproducibility and efficiency as a screening method for a large population [6][7][8]11] . The Galilei dual Scheimpflug analyzer is a noninvasive optical system that incorporates two principles: Placido rings and a dual Scheimpflug camera, for the study of the anterior segment of the eye [13,[18][19] . This technology allows a three-dimensional and 360 degrees evaluation of the anterior segment and captures different data of a large range of structures, such as corneal thickness, anterior and posterior corneal curvature, anterior and posterior corneal topography, corneal volume, ACD, and horizontal and vertical distance from limbus to limbus [20] . ...
Aim:
To evaluate dual Scheimpflug analyzer (Galilei) as a screening method for the diagnostic of gonioscopically narrow anterior chamber angles (ACA).
Methods:
In 40 eyes of 40 patients with different ACA range, the ACA, anterior chamber volume (ACV) and anterior chamber depth (ACD) were analyzed using the dual Scheimpflug analyzer (Galilei G6 system). Correspondence between these parameters and Shaffer's classification based on gonioscopy were studied. Receiving operator characteristic (ROC) curves and partition analysis were used to determine the efficacy of the Galilei system in screening for narrow angles. Agreement (Kappa statistics), sensitivity, and specificity for each eye, according to Galilei measures, were also assessed.
Results:
Shaffer's grade (from 0 to 4) were significantly associated with each of the measurements (P<0.001). In screening eyes with narrow angles with the Galilei, the area under the ROC curve was largest (0.90) when ACD was used as the reference, and partition analysis demonstrated that those eyes were most adequately partitioned with an ACD of 2.86 mm with 100% sensitivity and 80% specificity.
Conclusion:
The Galilei is a secure, repeatable and noncontact screening method for narrow angles. However it does not provide sufficient information about the ACA anatomy to be considered a substitute for gonioscopy.
... Visante OCT captures and analyzes the cross-sectional images of cornea, anterior chamber, iris and the central portion of the lens using a non-invasive technique based on low coherence interferometry. This tool is particularly useful to visualize narrow angles and to provide accurate measurements of anterior chamber depth [17]. ...
Background
The study aimed to evaluate iris thickness changes in patients with Primary Open Angle Glaucoma (POAG) or Ocular Hypertension (OHT) under treatment with Prostaglandin Analogues (PG).
Objectives
Primary outcome measures were iris thickness at the region of Dilator Muscle Region (DMR) and Sphincter Muscle Region (SMR). DMR/SMR ratio was also evaluated. The secondary outcome was the correlation between PG treatment length and iris parameters.
Methods
The charts of patients with POAG or OHT who underwent Visante OCT were retrospectively selected. The patients were divided in a group using PG for at least 6 months and a group using hypotensive drops not including PG or alpha-adrenergic agonists. A third group included healthy subjects.
Result
98 subjects were selected. Patients with POAG or OHT using PG eyedrops showed a significant iris thickness reduction at DMR compared to healthy subjects and to patients using hypotensive eyedrops not containing PG. Significantly higher SMR thickness values were found in PG group compared to both control groups. DMR/SMR ratio significantly reduced in PG group. No correlation was found between PG treatment length and iris parameters.
Conclusion
The present data indicate that PG treatment induced DMR thickness reduction and an increase in SMR thickness. These changes were not related to the duration of PG exposure.
... To objectively assess the angle both in adults and children, imaging techniques such as devices based on Scheimpflug technology or ultrasound biomicroscopy have been employed. 4,5 However, ultrasound biomicroscopy is still a contact technique and its resolution and that of Scheimpflug-based devices has been superseded by that offered by optical coherence tomography (OCT). 1 The more recently introduced technique anterior segment OCT is an objective and accurate method to measure the anterior chamber, or iridocorneal, angle. 6,7 OCT itself has evolved from time-domain to Fourier-domain or spectral-domain systems and now offers enhanced resolution, being a quick and well-tolerated procedure. ...
Purpose:
To obtain anterior chamber angle and trabecular meshwork (TM) measurements by Fourier-domain optical coherence tomography (FD-OCT) in a population of healthy white children.
Materials and methods:
This was a cross-sectional study examining 409 right eyes of 409 children. Trabecular-iris angle (TIA) and TM length and area were measured by FD-OCT (RTVue 100) in the nasal and temporal quadrants to analyze correlations between angle or TM measurements and age, sex, and refractive error.
Results:
Mean participant age was 10.5±3.4 years (range, 3 to 18 y); 51% were boys. Mean spherical error was 0.56±2.4 D (range, -9 to +7.5 D). TIA could be measured in 99%, whereas TM measurements could only be made in 83%. Mean TIA was 43.1±10.0 degrees (range, 16 to 76 degrees). No differences were observed in angle width according to sex (P=0.299; t test). TIA was correlated with age (R=0.204; P<0.001) and with spherical error (R=-0.457; P<0.001). Mean TM length was 530±106 μm (range, 299 to 891 μm) and mean TM area was 0.065±0.021 mm (range, 0.030 to 0.180 mm). No correlation was observed between TM metrics and age, sex or refractive error (R<0.08; P≥0.172).
Conclusions:
FD-OCT proved useful for the noninvasive measurement of TIA and TM metrics in children. Spherical error was the main determinant of TIA.
Amaç: Pentacam, RTVue ve Spectralis cihazları ile saptanan iridokorneal açı (İKA) ölçümlerinin tutarlılık ve uyumluluğunun değerlendirmesi amaçlanmıştır. Gereç ve Yöntem: 22 sağlıklı katılımcının 22 gözü retrospektif olarak değerlendirilmiştir. Pentacam cihazında ölçümler her gözde saat 3 ve 9 kadranlarda (nazal ve temporal) otomatik olarak alınmış olup, trabeküler-iris açı değerleri kaydedilmiştir. RTVue ve Spectralis ön segment optik koherens tomografilerinde (ÖS-OKT) ise, ön kamara girintisi açısı (ÖKGA), skleral mahmuz açısı (SMA) ve 500 µm uzaklıktan açı açılış uzaklığı (AAU500) parametreleri kaydedilmiştir. Tüm ölçümler benzer aydınlatma koşulları altında gerçekleştirilmiştir. 18 yaş altı olgular, geçirilmiş oküler cerrahi veya lazer öyküsü, İKA ölçümleri üzerinde farklılık yaratabilecek refraktif kusurlar, fiksasyon bozukluğu ya da yetersiz ön segment görüntü kalitesi, muayene esnasında GİB’ı 21mmHg üzerinde olan olgular çalışma dışında bırakılmıştır. Sonuç: Tüm cihazlar, hem nazal hem temporal kadranlarda ÖKGA-SMA yönünden birbirleriyle uyumlu bulunmuştur. Bland-Altman analizine göre Pentacam referans cihaz olarak alındığında, ÖKGA değeri yükseldikçe hem RTVue hem de Spectralis ölçümleri daha yüksek uyumluluk göstermektedir. ÖKGA, Pentacam ve RTVue için hem nazal hem temporal kadranlarda istatistiksel benzer sonuçlar verirken, Spectralis’te daha dar sonuçlar vermiştir. RTVue ve Spectralis arasında AAU500 değerleri arasında iyi tutarlılık görülse de, Spectralis’in RTVue’ya göre daha yüksek sonuçlar gösterdiği belirlenmiştir. Tartışma: IKA değerlendirilmesi için Pentacam, RTVue ve Spectralis ölçümlerinin birbirleriyle uyumlu olduğu saptansa da, gerek ÖKGA-SMA, gerekse AAU500 değerlerinin cihazlar arası farklılığı göz önüne alındığında, hasta takibinde ilgili cihazların birbirleri yerine kullanılmasının uygun olmayabileceği düşünülebilir.
Objectif: Proposer une méthode non invasive simple pour le dépistage des patients à risque de fermeture de l’angle en utilisant l’imagerie du segment antérieur à l’aide de la TCO. Méthodes: Des examens radiologiques des angles irido-cornéens en nasal et en temporal ont été réalisés au moyen de la TCO chez des patients référés pour suspicion de glaucome. Après l’identification de la ligne de Schwalbe, une droite fut tracée jusqu’au point de l’iris le plus rapproché (S-I) à l’aide de l’outil de compas intégré de l’appareil. Une gonioscopie a été effectuée et la méthode de Shaffer a été utilisée pour grader l’ouverture de l’angle afin d’évaluer la corrélation entre les deux méthodes. Résultats: Trente-quatre images étaient disponibles pour analyse. Les coefficients de corrélation de Spearman entre les mesures S-I et les grades de Shaffer se sont établis à 0,81 et 0,77 pour les quadrants nasal et temporal respectivement. Les calculs intra-observateur des coefficients de corrélation intraclasse avaient une excellente reproductibilité (0,98 et 0,99 pour les angles en nasal et en temporal) et on a observé une excellente corrélation inter-observateur (0,94 et 0,93). La valeur diagnostique S-I pour les angles à risque de fermeture a été provisoirement établie à 330 mm. Conclusion: La mesure S-I corrèle fortement avec les résultats de la gonioscopie et pourrait être une solution de rechange appropriée pour évaluer le risque de fermeture de l’angle.
Purpose: To propose a simple non-invasive method for screening patients at risk for angle closure using anterior segment OCT. Methods: Scans of nasal and temporal iridocorneal angles in glaucoma suspect patients were performed using OCT. Upon identifying Schwalbe’s line, the integrated caliper tool was used to draw a line to the nearest point of the iris to produce a measure ‘S-I’. Gonioscopy was performed and angles graded according to Shaffer’s classification to assess the correlation between both methods. Results: Thirty-four images were available for analysis. Spearman correlation coefficients between S-I anf gonioscopy grades were 0.81 for nasal and 0.77 for temporal quadrants respectively. Intraobserver ICC calculations demonstrated excellent reproducibility (0.98 and 0.99 for nasal and temporal angles) and excellent interobserver correlation (0.94 and 0.93). The diagnostic cutoff value of S-I for occludable angles was established at 330mm. Conclusion: S-I measurement strongly correlates with gonioscopy and may be a suitable alternative for evaluating risk for angle closure.
To demonstrate a new diagnostic technique, optical coherence tomography, for high-resolution cross-sectional imaging of structures in the anterior segment of the human eye in vivo. Optical coherence tomography is a new, noninvasive, noncontact optical imaging modality that has spatial resolution superior to that of conventional clinical ultrasonography (< 20 microns) and high sensitivity (dynamic range, > 90 dB).
Survey of intraocular structure and dimension measurements.
Laboratory.
Convenience sample.
Correlation with range of accepted normal intraocular structure profiles and dimensions.
Direct in vivo measurements with micrometer-scale resolution were performed of corneal thickness and surface profile (including visualization of the corneal epithelium), anterior chamber depth and angle, and iris thickness and surface profile. Dense nuclear cataracts were successfully imaged through their full thickness in a cold cataract model in calf eyes in vitro.
Optical coherence tomography has potential as a diagnostic tool for applications in noncontact biometry, anterior chamber angle assessment, identification and monitoring of intraocular masses and tumors, and elucidation of abnormalities of the cornea, iris, and crystalline lens.
Background
Recent advances in high-speed scanning technology have enabled a new generation of optical coherence tomographic (OCT) systems to perform imaging at video rate. Here, a handheld OCT probe capable of imaging the anterior segment of the eye at high frame rates is demonstrated for the first time.Objective
To demonstrate real-time OCT imaging of anterior segment structures.Design
Survey of anterior segment structures in normal human subjects.Setting
Laboratory.Main Outcome Measures
Achieving real-time imaging of the anterior segment, satisfactory image quality, and convenience of a handheld probe.Results
Optical coherence tomographic imaging of the anterior segment of the eyes of human subjects was performed using 1310-nm wavelength light with an image rate of 8 frames per second. Imaging trials demonstrated clear resolution of corneal epithelium and stroma, sclerocorneal junction, sclera, iris pigment epithelium and stroma, and anterior lens capsule. The anterior chamber angle was clearly visualized. Limited imaging of the ciliary body was performed. Real-time imaging of pupillary constriction in response to light stimulus was also performed.Conclusion
High-speed OCT at 1310-nm wavelength is a potentially useful technique for noninvasive assessment of anterior segment structures.Clinical Relevance
Our results suggest that real-time OCT has potential applications in glaucoma evaluation and refractive surgery.
Objective:
To demonstrate a new diagnostic technique, optical coherence tomography, for highresolution cross-sectional imaging of structures in the anterior segment of the human eye in vivo. Optical coherence tomography is a new, noninvasive, noncontact optical imaging modality that has spatial resolution superior to that of conventional clinical ultrasonography (<20 μm) and high sensitivity (dynamic range, >90 dB).
Design:
Survey of intraocular structure and dimension measurements.
Setting:
Laboratory.
Patients:
Convenience sample.
Main Outcome Measures:
Correlation with range of accepted normal intraocular structure profiles and dimensions.
Results:
Direct in vivo measurements with micrometer-scale resolution were performed of corneal thickness and surface profile (including visualization of the corneal epithelium), anterior chamber depth and angle, and iris thickness and surface profile. Dense nuclear cataracts were successfully imaged through their full thickness in a cold cataract model in calf eyes in vitro.
Conclusions:
Optical coherence tomography has potential as a diagnostic tool for applications in noncontact biometry, anterior chamber angle assessment, identification and monitoring of intraocular masses and tumors, and elucidation of abnormalities of the cornea, iris, and crystalline lens.
Primary angle closure is a condition characterized by obstruction to aqueous humor outflow by the peripheral iris, and results in changes in the iridocorneal angle that are visible through gonioscopic examination. Gonioscopy in these eyes, however, can be difficult. This chapter discusses techniques that might help in the examination. These include beginning the examination with the inferior angle, methods to help in looking over the iris, cycloplegia, locating the corneal wedge, indentation, van Herick estimation, examining the other eye, and topical glycerin. Finally, there is a discussion about the pathology associated with the closed angle, with emphasis on the appearance of iris bombé, plateau iris, and the distinction between iris processes and peripheral anterior synechiae.
A bstract
Scheimpflug photography and densitometric image analysis are very precise techniques for light scattering measurement and biometry in the anterior segment of the eye. They provide reproducible data on the characteristics of the anterior eye segment in clinical and experimental studies and the set of data obtained allows discrimination of light scattering changes because of ageing, disease or toxic effects. The techniques can also be used to determine no‐effect levels or maximally tolerable dosages of physical and chemical noxious factors. Several Scheimpflug cameras have been marketed, but the only cameras commercially available today are the Nidek EAS 1000 and the Oculus Pentacam. This review outlines the development of the technique and its introduction into ophthalmology. Furthermore, the application of the technique in clinical and experimental ophthalmology as well as in ocular toxicology are presented and discussed.
To evaluate intraobserver and interobserver reproducibility of measurement of images obtained during ultrasound biomicroscopy.
Four anterior segment images of four normal patients were obtained by a single examiner. The measurements of three independent observers were compared to assess interobserver reproducibility in quantifying the images. Thirteen different anterior segment parameters were measured by each observer on each image. Intraobserver and interobserver reproducibility of measurement were assessed by calculating the coefficient of variation for each individual observer and by using the F test to detect a difference among observers.
Intraobserver reproducibility was high. Interobserver reproducibility for the measured parameters varied considerably and was affected by subjective interpretation of visualized anatomic landmarks.
The optimal parameters for quantitative ultrasound biomicroscopy require refinement. Measurements of alterable parameters are best measured presently by a single observer. Ultrasound biomicroscopy has the potential to elucidate anatomic relationships underlying much anterior segment disease, but caution in interpreting quantitative differences is warranted.
To evaluate intraobserver and interobserver reproducibility of measurements in images obtained by the 50 MHz Humphrey Ultrasound Biomicroscope.
The first stored image of central cornea, central anterior chamber, and angle structures obtained at 50 examinations were measured twice by three observers. Nine different parameters were measured in angle images and two in images of central cornea and anterior chamber. Intraobserver reproducibility was assessed by calculating the coefficient of variation and interobserver reproducibility by a two-ways ANOVA.
Intraobserver reproducibility was high for all measurements of central cornea thickness and anterior chamber depth with a coefficient of variation (%) < or = 3.8%. In angle images the intraobserver reproducibility of measurements was often lower (coefficient of variation (%) 1.3-52.6%). The lower reproducibility was most noticeable in measurements involving the less defined structures. Interobserver reproducibility was poor.
Comparison of measurements are best done of well defined structures and by only one observer.
Recent advances in high-speed scanning technology have enabled a new generation of optical coherence tomographic (OCT) systems to perform imaging at video rate. Here, a handheld OCT probe capable of imaging the anterior segment of the eye at high frame rates is demonstrated for the first time.
To demonstrate real-time OCT imaging of anterior segment structures.
Survey of anterior segment structures in normal human subjects.
Laboratory.
Achieving real-time imaging of the anterior segment, satisfactory image quality, and convenience of a handheld probe.
Optical coherence tomographic imaging of the anterior segment of the eyes of human subjects was performed using 1310-nm wavelength light with an image rate of 8 frames per second. Imaging trials demonstrated clear resolution of corneal epithelium and stroma, sclerocorneal junction, sclera, iris pigment epithelium and stroma, and anterior lens capsule. The anterior chamber angle was clearly visualized. Limited imaging of the ciliary body was performed. Real-time imaging of pupillary constriction in response to light stimulus was also performed.
High-speed OCT at 1310-nm wavelength is a potentially useful technique for noninvasive assessment of anterior segment structures.
Our results suggest that real-time OCT has potential applications in glaucoma evaluation and refractive surgery.
To investigate the mean values and standard deviations according to age, reliability, and correlation between different parameters of anterior chamber measurements using the Pentacam rotating Scheimpflug camera.
Heidelberg IOL and Refractive Surgery Research Group, Department of Ophthalmology, University of Heidelberg, Heidelberg, Germany.
This prospective clinical study comprised 76 healthy volunteers (mean age 46.6 years +/- 16.8 [SD]). Three consecutive measurements were made of only 1 eye and anterior chamber depth (ACD), mean and minimum anterior chamber angle (ACA), and anterior chamber volume (ACV) were evaluated.
Mean ACD was 2.93 +/- 0.36 mm, mean ACA was 34.81 +/- 5.05 degrees, minimum ACA was 29.99 +/- 5.53 degrees, and mean ACV was 160.3 +/- 36.81 mm3. Increasing age was associated with reduced ACD and ACV; however, mean and minimum ACAs were lowest in patients aged 40 to 59 years. Excellent correlation was found between ACD and ACV (R = 0.92). Anterior chamber depth and mean ACA correlated only moderately (R = 0.65). The correlation coefficient between ACD and minimum ACA was smaller (R = 0.58). There was no correlation between ACV and ACA (R = 0.37). Minor standard deviations were noted (ACD 0.02 +/- 0.02 mm, mean ACA 1.12 +/- 0.94 degrees, minimum ACA 2.04 +/- 2.67 degrees, and ACV 2.48 +/- 1.65 mm3).
Using the Pentacam, it was possible to examine different parameters of the anterior chamber within a short period and with good reliability. The evaluation of the ACA in different positions can help to classify the potential risk for angle-closure glaucoma.
To assess intraobserver and interobserver variability of anterior segment optical coherence tomography (AS-OCT) as an objective diagnostic tool to quantify the anterior chamber angle and opening width.
University Eye Clinic, Lübeck, Germany.
The anterior chamber angle and opening width were assessed in 18 eyes of 9 healthy volunteers by 2 observers. Intraobserver reproducibility was evaluated by calculating an intraclass correlation coefficient (ICC) in a mixed model. Each observer had a separate model using information from 5 scans. Interobserver variability was determined by Bland-Altman analysis. The ICC was calculated in a mixed model using a residual maximum likelihood method. The results of 3 and 5 repeated scans were evaluated to indicate the change to 1 measurement application.
The mean anterior chamber angle measurement was 35.9 degrees +/- 5.7 (SD) for observer A and 36.2 +/- 5.7 degrees for observer B. The ICC was 0.94 and 0.91, respectively. The mean opening width was 315 +/- 62 microm for observer A and 317 +/- 60 microm for observer B. The ICC was 0.97 and 0.93, respectively. Interobserver comparisons showed a mean difference between anterior chamber angle measurements of -0.27 +/- 1.6 degrees, a limit of agreement (LOA) interval from -3.52 to 2.98 degrees, and an ICC estimate of 0.96. The mean difference in opening width measurements was 2.40 +/- 12.40 microm, the LOA from -27.20 to 22.40 microm, and the estimated ICC 0.96. Using 1 instead of the mean of 5 measurements, the LOA range increased by 3.46 degrees for the anterior chamber angle and 30.0 microm for the opening width.
Anterior chamber angle and opening width measurements by OCT showed low intraobserver and interobserver variability, indicating OCT is a valuable technique for quantitative assessment that provides reproducible measurements and objective documentation by different examiners.