Carol Yim Lui Cheung

Singapore Eye Research Institute, Tumasik, Singapore

Are you Carol Yim Lui Cheung?

Claim your profile

Publications (25)74.14 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: To investigate the agreement of vertical cup-to-disc ratio (VCDR) measured from Heidelberg Retina Tomograph 3 (HRT-3), high-definition optical coherence tomography (HD-OCT), and clinical grading. A total of 933 consecutive subjects underwent optic nerve head imaging with HRT-3 and HD-OCT during a single visit. The vertical dimensions of the disc and cup were measured by slit-lamp examination using an eyepiece graticule. Bland-Altman plots evaluated the agreement in the VCDR obtained by the 2 instruments and clinical grading. We found a significant trend for the difference in VCDR measured clinically and with HRT and HD-OCT (P<0.001 for both). The mean VCDR differed significantly between clinical measurement and that evaluated by HRT and HD-OCT, respectively (0.40±0.12 vs. 0.37±0.21 and 0.40±0.12 vs. 0.50±0.14, P<0.001 for both), with significantly poor correlation (r=0.35 and 0.34, P<0.001 for both). In general, there is poor correlation and a lack of agreement of VCDR measured using HRT-3, HD-OCT, and clinical grading. HD-OCT has somewhat better agreement with clinical measurements of VCDR. Compared with clinical grading, HD-OCT tended to overestimate VCDR, whereas HRT-3 tended to underestimate it.
    No preview · Article · Mar 2015 · Journal of glaucoma
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Alzheimer's Disease (AD) is the most common subtype of dementia. As the prevalence of dementia is projected to increase, the burden of the disease on society is expected to become increasingly significant. The link between eye pathology and neurodegenerative diseases has been established in multiple studies. In particular, optic nerve parameters associated with neuronal loss in AD include retinal ganglion cells (RGC). Retinal ganglion cells are similar to neurons in the cerebral cortex, and have been correlated to neurodegeneration in AD. Ocular imaging techniques such as optical coherence tomography (OCT) have provided a rapid and non-invasive method for quantifying optic nerve parameters in vivo. Spectral domain (SD)-OCT has shown good potential in the study of the optic nerve in AD as it enables more comprehensive assessment of RGCs. Earlier generation OCT techniques only assess the retinal nerve fibre layer, which consists of RGC axons. Spectral domain-OCT offers ultra-high scan speed and image resolution, enabling improved sampling of retinal layers. Retinal layers such as the ganglion cell-inner plexiform layer (GC-IPL), which contain the dendrites and nuclei of RGCs, can be assessed with SDOCT. This article presents a review of literature associating eye pathology with AD, and explores the potential of SD-OCT in future AD studies. Spectral domain-OCT has the potential to draw more links between optic nerve pathology and neurodegeneration.
    Preview · Article · Mar 2014
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objective: To study the prevalence of and associated factors for cognitive impairment and dementia in community dwelling Chinese from Singapore. Methods: This study includes Chinese subjects from the Epidemiology of Dementia in Singapore (EDIS) study, aged ≥60 years, who underwent comprehensive examinations, including cognitive screening with the locally validated Abbreviated Mental Test and Progressive Forgetfulness Questionnaire. Screen positive participants subsequently underwent extensive neuropsychological testing and cerebral MRI. Cognitive impairment no dementia (CIND) and dementia were diagnosed according to internationally accepted criteria. The prevalence of cognitive impairment and dementia were computed per 5 year age categories and gender. To examine the relationship between baseline associated factors and cognitive impairment, we used logistic regression models to compute odd ratios with 95% CI. Results: 1538 Chinese subjects, aged ≥60 years, underwent cognitive screening: 171 (15.2%) were diagnosed with any cognitive impairment, of whom 84 were CIND mild, 80 CIND moderate and seven had dementia. The overall age adjusted prevalence of CIND mild was 7.2%; CIND moderate/dementia was 7.9%. The prevalence increased with age, from 5.9% in those aged 60-64 years to 31.3% in those aged 75-79 years and 44.1% in those aged ≥80 years. Multivariate analysis revealed age, diabetes and hyperlipidaemia to be independently associated with cognitive impairment. Conclusions: In present study, the overall prevalence of cognitive impairment and dementia in Chinese was 15.2%, which is in the same range as the prevalence reported in Caucasian and other Asian populations.
    No preview · Article · Feb 2013 · Journal of neurology, neurosurgery, and psychiatry
  • Xinting Gao · Damon Wing Kee Wong · T.T. Ng · Carol Yim Lui Cheung · C.Y. Cheng · Tien Yin Wong
    [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, we propose an automatic approach to grade cortical and Posterior Sub-Capsular (PSC) cataracts using retroillumination images. Low-level vision features are used to characterize the photometric appearances and geometric structures of cortical and PSC cataracts in retroillumination images. The prediction result gives an opacity score that serves as an estimation of cataract severity. The system is tested on 434 pairs of lens images with ground truth labels from professional graders. Five-fold cross-validation with random partition of the data shows that the mean correlation between the proposed method and the grader’s result is 0.7392 with variance 0.0003, which is promising. The proposed prediction approach can also be used as a preliminary estimation to improve existing detection systems. Most existing detection systems apply one method to all types of lens images. Such single method may fail for one to some types of lens images as cataracts with different severity not only have different levels of opacity, but also have different photometric appearances and geometric structures. We demonstrate an improved cortical cataracts detection system that employs different strategies to address the challenges in cataract detection for lenses with different levels of estimated opacity. The strategies simultaneously overcome the over-detection issue for clear lenses and the under-detection issue for lenses with high opacity. The results show an improvement of accuracy in cortical cataract detection from 51% to 62%. The corresponding Kappa agreement score is improved from 0.25 to 0.40.
    No preview · Article · Jan 2013

  • No preview · Article · Jan 2013 · Cerebrovascular Diseases
  • Carol Yim Lui Cheung · Tien Yin Wong

    No preview · Article · Dec 2012
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Identifying the boundary of the optic cup excavation is of critical importance in the assessment of glaucomatous risk. Currently, most approaches are focused on the use of pallor. We present an automatic method to determine the cup excavation boundary based on vessel kinking in non-stereo retinal fundus images. The method tracks vessels using a self-initialized evolving model which adapts during propagation. A piecewise analysis of the vessel trajectory is conducted to determine vessel kinking locations, from which the optic cup is obtained. Our proposed method is validated on a large database of 618 images. The results suggest that our proposed method is able to obtain a more accurate cup excavation detection than other tested methods.
    Full-text · Conference Paper · Nov 2012
  • [Show abstract] [Hide abstract]
    ABSTRACT: Introduction: We compared the agreement of diabetic retinopathy (DR) assessment between trained non-physician graders (NPGs) and family physicians (FPs) in a primary healthcare setting. Methods: This was a cross-sectional study conducted retrospectively over a period of one month. The participants were diabetic patients from two primary healthcare clinics (polyclinics) in Singapore. Single-field digital retinal images were obtained using a non-mydriatic 45-degree fundus camera. Retinal images were graded for the presence or absence of DR by FPs at the polyclinics and by NPGs at a central ocular grading centre. The FPs' and NPGs' assessments of DR were compared with readings by a single retinal specialist (reference standard). Results: A total of 367 diabetic patients (706 eyes) were included in the study. The mean age of the patients was 63 years, and the majority were Chinese (83.8%). For DR assessment, the agreement between NPGs and the retinal specialist was substantial (ĸ = 0.66), while the agreement between FPs and the retinal specialist was only fair (ĸ = 0.40). NPGs' assessment showed higher sensitivity (70% vs. 45%) and comparable specificity (94% vs. 92%) as compared to FPs' assessment. The area under the receiver operating characteristic curve of NPGs' assessment of DR was greater than that of the FPs' (0.82 vs. 0.69, p < 0.001). Conclusion: This study has demonstrated that trained NPGs are able to provide good detection of DR and maculopathy from fundus photographs. Our findings suggest that DR screening by trained NPGs may provide a costeffective alternative to FPs.
    No preview · Article · Nov 2012 · Singapore medical journal
  • [Show abstract] [Hide abstract]
    ABSTRACT: Background: Retinal vasculature can reflect microvascular damage from hypertension, and may be a marker of target end-organ damage. We studied the relationship of a range of retinal vascular structural parameters with stroke and its major subtypes. Methods: We conducted a case-control study of acute stroke cases recruited from a tertiary hospital in Singapore. Clinical assessment included neuroimaging and retinal photography, classifying strokes by TOAST criteria. Non-stroke healthy controls selected from the Singapore Epidemiology of Eye Disease program were matched by age, gender and race. Retinal vascular parameters (retinal vascular caliber, tortuosity, fractal dimension and branching angle) were assessed using a semi-automated computer-based program. Logistic regression models were constructed adjusting for age, gender, and race; and additionally for smoking, hypertension, diabetes and hypercholesterolemia status. Results: A total of 563 ischemic stroke cases and 576 controls were included in this analysis. Major subtypes of ischemic strokes included 264 lacunar, 186 large artery and 55 cardioembolic strokes. Narrower arteriolar caliber (multivariable-adjusted odds ratio (OR) per standard deviation (SD) decrease: 2.18; 95%CI: 1.83-2.61), decreased arteriolar fractal dimension (OR per SD decrease: 2.35; 95%CI: 1.95-2.82) and venular fractal dimension (OR per SD decrease: 1.73; 95%CI: 1.48-2.05), and increased arteriolar tortuosity (OR per SD increase: 1.57; 95%CI: 1.25-1.97) and venular tortuosity (OR per SD increase: 1.53; 95%CI: 1.29-1.80) were associated with stroke. Similar associations were found for lacunar, large artery and cardioembolic strokes. Conclusions: Stroke cases were more likely to have altered retinal microvasculature, reflecting microvascular changes that may be independent of hypertension and other traditional risk factors.
    No preview · Article · Sep 2012 · Journal of Hypertension
  • [Show abstract] [Hide abstract]
    ABSTRACT: To evaluate the performance of progression detection and the rate of change of retinal nerve fiber layer (RNFL), neuroretinal rim, and visual field measurements in glaucoma. Prospective study. One hundred eight eyes of 70 glaucoma patients. Patients were followed up every 4 months for at least 2.9 years (median, 3.2 years) for measurement of RNFL thickness with the Stratus optical coherence tomograph (OCT) (Carl Zeiss Meditec, Dublin, CA), neuroretinal rim area with the Heidelberg Retinal Tomograph (HRT 3; Heidelberg Engineering, GmbH, Dossenheim, Germany), and visual field with the Humphrey Field Analyzer II (Carl Zeiss Meditec). Linear regression analyses were performed between visual field index (VFI), RNFL, and neuroretinal rim measurements and age, with progression defined when a significant negative trend was detected. The agreement among structural and functional measurements was evaluated with κ statistics. The mean rate of change was estimated with linear mixed modeling. The agreement on progression detection and the rate of change of RNFL, neuroretinal rim, and VFI measurements. A total of 1105 OCT, 1062 HRT, and 1099 visual field measurements were analyzed. The agreement of progression detection among the 3 investigations was poor (κ≤0.09). Ten eyes (9.3%; 9 patients) showed progression by average RNFL thickness, 16 (14.8%; 14 patients) by global neuroretinal rim area, and 35 (32.4%; 31 patients) by VFI. Only 1 eye (0.9%) had progression detected by all 3 methods. There were large variations in the rate of change of VFI, average RNFL thickness, and global neuroretinal rim area, with a range between -0.63% and -4.97% per year, -2.32% and -10.12% per year, and -0.61% and -8.48% per year, respectively. The respective mean rate estimates were -1.15% per year (95% confidence interval [CI], -1.56% to -0.73%), -0.70% per year (95% CI, -1.19% to -0.21%), and -1.06% per year (95% CI, -1.56% to -0.55%). The agreement of progression detection among RNFL, neuroretinal rim, and visual field measurements was poor, and the rate of RNFL, neuroretinal rim, and visual field progression varied considerably within and between subjects. Given this variability, interpretation of RNFL, neuroretinal rim, and VFI progression always should be evaluated on an individual basis. Proprietary or commercial disclosure may be found after the references.
    No preview · Article · Apr 2011 · Ophthalmology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Under the framework of computer-aided diagnosis, optical coherence tomography (OCT) has become an established ocular imaging technique that can be used in glaucoma diagnosis by measuring the retinal nerve fiber layer thickness. This letter presents an automated retinal layer segmentation technique for OCT images. In the proposed technique, an OCT image is first cut into multiple vessel and nonvessel sections by the retinal blood vessels that are detected through an iterative polynomial smoothing procedure. The nonvessel sections are then filtered by a bilateral filter and a median filter that suppress the local image noise but keep the global image variation across the retinal layer boundary. Finally, the layer boundaries of the filtered nonvessel sections are detected, which are further classified to different retinal layers to determine the complete retinal layer boundaries. Experiments over OCT for four subjects show that the proposed technique segments an OCT image into five layers accurately.
    Full-text · Article · Nov 2010 · IEEE Transactions on Biomedical Engineering
  • [Show abstract] [Hide abstract]
    ABSTRACT: To evaluate and compare the diagnostic agreement and performance for glaucoma detection between a confocal scanning laser ophthalmoscope and a spectral-domain optical coherence tomograph (OCT). Prospective, cross-sectional study. One hundred fifty-five subjects (79 glaucoma and 76 normal subjects). One eye from each individual was selected randomly for optic disc and retinal nerve fiber layer (RNFL) imaging by the Heidelberg Retinal Tomograph (HRT; Heidelberg Engineering, GmbH, Dossenheim, Germany) and the Spectralis OCT (Heidelberg Engineering), respectively. Glaucoma was defined based on the presence of visual field defects with the Humphrey visual field analyzer (Carl Zeiss Meditec, Dublin, CA). The agreement of the categorical classification ("within normal limits," "borderline," and "outside normal limits") at the temporal, superotemporal, superonasal, nasal, inferonasal and inferotemporal sectors of the optic disc were evaluated (kappa statistics). The diagnostic sensitivity and specificity between optic disc and RNFL assessment were compared (McNemar's statistics). Area under the receiver operating characteristic curve (AUC) of OCT RNFL and HRT optic disc parameters were computed after adjustment of age, axial length, and optic disc area. Agreement of categorical classification, AUC of optic disc, and RNFL parameters. The agreement of categorical classification between HRT and Spectralis OCT were fair to moderate (kappa ranged between 0.30 and 0.53) except for global (kappa = 0.63) and inferotemporal (kappa = 0.68) measurements. Defining glaucoma as having "outside normal limits" in the global and/or in >or=1 of the sectoral measurements, the respective sensitivities of Spectralis OCT and HRT were 91.1% and 79.8% (P = 0.012) at a similar level of specificity (97.4% and 94.7%). The AUC of OCT global RNFL thickness (0.978) was greater than those of HRT global rim area (0.905), vertical cup-disc ratio (0.857), rim-disc area ratio (0.897), and multivariate discriminant analysis (0.880-0.925; all with P<or=0.028) after covariates adjustment. The diagnostic classification provided in the HRT and Spectralis OCT analysis report may not agree. At a comparable level of specificity, Spectralis OCT RNFL measurement attained a higher sensitivity than HRT optic disc measurement.
    No preview · Article · Dec 2009 · Ophthalmology
  • [Show abstract] [Hide abstract]
    ABSTRACT: To develop a grading system to evaluate the scleral spur visibility and to investigate the association between this and the angle width. Sixty healthy normal subjects (33 with open angles and 27 with narrow angles on dark room gonioscopy) underwent anterior segment imaging with the Visante OCT (Carl Zeiss Meditec, Dublin, CA). The anterior chamber angles at 12-o' clock hour positions were imaged and analyzed. The scleral spur at each clock hour position was independently graded by 2 observers. A scleral spur visibility score (SSVS) of 2 denotes clear visibility of the scleral spur. SSVS of 0 and 1 represent undetectable and moderately by visibile scleral spur, respectively. The interobserver agreement of the SSVS was evaluated with kappa statistics. The associations between age, sex, axial length, refraction, angle width [mean anterior chamber angle detection with edge measurement and identification algorithm (ACADEMIA) angle], and the mean SSVS were examined with univariate and multivariate analyses. The mean gonioscopy grades were 3.6 and 0.8 for the open and narrow angle groups, respectively. The interobserver agreement in grading the scleral spur visibility was 0.71. The inferior angle (6:00) had the worst visibility of the scleral spur (SSVS=1.05+/-0.49) whereas the scleral spur of the nasal angle (3:00) showed the best visibility (SSVS=1.66+/-0.46). There were significant differences between SSVS at 6:00 and the other clock hours except for 5:00 and 7:00. The mean SSVS correlated positively with gonioscopy grade, anterior chamber depth, and ACADEMIA angle, and negatively with age. The only significant factor associated with scleral spur visibility was the ACADEMIA angle (P=0.013) after adjustment for other covariates. The visibility of the scleral spur is an important determinant of the dimension of anterior chamber angle.
    No preview · Article · Jul 2009 · Journal of glaucoma
  • [Show abstract] [Hide abstract]
    ABSTRACT: To evaluate and compare the longitudinal variability of optical coherence tomography (OCT) and confocal scanning laser ophthalmoscopy (CSLO) optic disc measurements. A total of 25 normal and 50 glaucomatous eyes from 75 subjects were included in the analysis. The optic disc was measured by OCT and CSLO. Three separate measurements collected over an average period of 8.5+/-0.9 months were used to evaluate reproducibility. Univariate and multivariate regression analyses were performed to evaluate the associations between age, refraction, diagnosis (glaucoma or normal), visual field mean deviation, optic disc area, signal strength variance (OCT), optic disc area variance (OCT), image quality SD (CSLO), reference height variance (CSLO), and rim area variability. The intraclass correlation coefficient of optic disc measurements (except for optic disc area) ranged between 0.86 and 0.95 for OCT and between 0.89 and 0.96 for CSLO. The intraclass correlation coefficient for rim area measurement was significantly higher in CSLO (0.95) than that of OCT (0.86, P<0.001). After adjustment for other predictors, optic disc area variance and reference height variance were the most important factors responsible for rim area variability in OCT and CSLO, respectively. Although both OCT and CSLO have relatively low variability for optic disc measurements, CSLO demonstrates higher measurement reproducibility for rim area compared with OCT. Variations of disc area in OCT and reference height in CSLO constituted a significant proportion of the rim area variability during longitudinal assessment.
    No preview · Article · Feb 2009 · Journal of glaucoma
  • Carol Yim Lui Cheung · Christopher Kai-shun Leung

    No preview · Article · Jan 2009
  • [Show abstract] [Hide abstract]
    ABSTRACT: To evaluate the reliability of lens density measurement with anterior segment optical coherence tomography (OCT) and its association with the Lens Opacity Classification System Version III (LOCS III) grading. Fifty-five eyes from 55 age-related cataract patients were included. One eye from each subject was selected at random for lens evaluation. After dilation, lens photographs were taken with a slit lamp and graded against the LOCS III standardised condition. Anterior segment OCT imaging was performed on the same eyes with a high-resolution scan. The association between the anterior segment OCT nucleus density measurement and LOCS III nuclear opalescence (NO) and nuclear colour (NC) scores was evaluated with the Spearman correlation coefficient. Anterior segment OCT measurement precision, coefficient of variation (CVw), and intraclass correlation coefficient (ICC) were calculated. The mean NO and NC scores were 3.39 (SD 1.10) and 3.37 (SD 1.27), respectively. Significant correlations were found between anterior segment OCT nuclear density measurements and the LOCS III NO and NC scores (r = 0.77 and 0.60, respectively, both with p<0.001). The precision, CVw and ICC of anterior segment OCT measurement were 2.05 units, 4.55% and 0.98, respectively. Anterior segment OCT nucleus density measurement is reliable and correlates with the LOCS III NO and NC scores.
    No preview · Article · Oct 2008 · The British journal of ophthalmology
  • Source
    C Y L Cheung · C K F Yiu · R N Weinreb · D Lin · H Li · A Y Yung · C P Pang · D S C Lam · C K S Leung
    [Show abstract] [Hide abstract]
    ABSTRACT: To study the effect of optical coherence tomography (OCT) scan circle displacement on retinal nerve fibre layer (RNFL) measurement errors using cubic spline models. Forty-nine normal subjects were included in the analysis. In one randomly selected eye in each subject, RNFL thickness around the optic disc was measured by taking 16 circular scans of different sizes (scan radius ranged from 1 to 2.5 mm). The RNFL profile in each eye was constructed with a mathematical model using a smoothing spline approximation. Scan circle (diameter 3.4 mm) RNFL measurements (total average, superior, nasal, inferior, and temporal RNFL thicknesses) obtained from eight directions (superior, superonasal, nasal, inferonasal, inferior, inferotemporal, temporal, and superotemporal) displaced at different distances (0.1, 0.2, 0.3, 0.4, 0.5, 0.6, and 0.7 mm) from the disc centre were then computed by a computer program and compared to the 'reference standard' where the scan circle is centred at the optic disc. RNFL measurement error was calculated as the absolute of (RNFL thickness(displaced) - RNFL thickness(reference standard)). The respective mean average, superior, nasal, inferior, and temporal RNFL measurement errors were 2.3+/-2.0, 4.9+/-4.5, 4.1+/-3.8, 6.2+/-7.6, and 3.8+/-3.5 microm upon 0.1 mm scan circle displacement, and 12.1+/-11.4, 27.8+/-18.4, 21.7+/-18.6, 34.8+/-22.9, and 15.2+/-10.7 microm upon 0.7 mm scan circle displacement. Significant differences of average and quadrant RNFL thicknesses were evident between centred and displaced scan circle measurements (all with P<0.001). RNFL measurement error increased in a monotonic fashion with increasing distance away from the disc and the change was direction-dependent. RNFL measurement error varies with the direction and distance of scan displacement. The superior and the inferior RNFL measurements are most vulnerable to scan displacement errors, whereas the average RNFL thickness is the least susceptible. Obtaining a well-centred scan is essential for reliable RNFL measurement in OCT.
    Preview · Article · Sep 2008 · Eye (London, England)
  • [Show abstract] [Hide abstract]
    ABSTRACT: To evaluate the repeatability and reproducibility of central corneal thickness (CCT) measurements obtained by 2 anterior segment optical coherence tomography (OCT) imaging systems and to examine their agreements with ultrasound pachymetry. Observational cross-sectional study. Fifty eyes from 50 healthy normal subjects were recruited. In one randomly selected eye in each subject, CCT was measured by slit-lamp OCT (SLOCT), Visante OCT, and ultrasound pachymetry. For anterior segment OCT measurements, both automatic and manual CCTs were obtained. Twenty-five of the 50 subjects were invited for 2 more visits within a week to evaluate repeatability and reproducibility of CCT measurement. Central corneal thickness measurement obtained by the 3 methods and their agreements. Intrasession and intersession within-subject standard deviation (S(w)), precision (1.96xS(w)), coefficient of variation (CV(w)) (100xS(w)/overall mean), and intraclass correlation coefficient (ICC) were calculated to evaluate repeatability and reproducibility. Good repeatability and reproducibility were found for both automatic and manual CCT measurements obtained by SLOCT and Visante OCT. For intrasession repeatability, CV(w) and ICC values ranged between 0.9% and 1.2% and 0.96 and 0.98, respectively. For intersession reproducibility, the respective CV(w) and ICC values ranged between 1.2% and 1.4% and 0.94 and 0.96. Although no significant difference was found between automatic/manual SLOCT measurements and ultrasound pachymetry, automatic Visante OCT CCT (535.7+/-30.2 microm) was significantly less than CCT with ultrasound pachymetry (550.3+/-31.14 microm) (P<0.001). In contrast, manual Visante OCT measurement (558.8+/-32.8 microm) was slightly higher than ultrasound pachymetry (P<0.001). Nevertheless, SLOCT and Visante OCT measurement of CCT had 95% limits of agreement comparable to that of ultrasound pachymetry. The best agreement was observed in the manual SLOCT measurement (95% limits of agreement between -15.5 and 11.7 microm). Both SLOCT and Visante OCT automatic and manual CCT measurements were reliable and showed comparable agreement with ultrasound pachymetry. Although the 2 anterior segment OCT imaging systems have similar design and working principles, clinicians should be aware of the differences in CCT measurement between the 2 anterior segment OCTs.
    No preview · Article · Jun 2008 · Ophthalmology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To compare anterior chamber angle measurements obtained from two anterior segment optical coherence tomography (OCT) instruments and to evaluate their agreements and interobserver reproducibility. Forty-nine eyes from 49 healthy normal subjects were studied. The anterior chamber angle was imaged with the Visante anterior segment OCT (Carl Zeiss Meditec, Dublin, CA) and the slit lamp OCT (SLOCT, Heidelberg Engineering, GmbH, Dossenheim, Germany) on one randomly selected eye in each subject and measured by two independent observers. The angle-opening distance (AOD 500), the trabecular-iris angle (TIA 500), and the trabecular-iris space area (TISA 500) at the nasal and temporal angles were measured. The agreements between SLOCT and Visante OCT measurements and the interobserver reproducibility were evaluated. The mean nasal/temporal anterior chamber angles measured by Visante OCT and SLOCT were 527 +/- 249/572 +/- 275 microm (AOD), 0.180 +/- 0.091/0.193 +/- 0.102 mm(2) (TISA), and 38.1 +/- 12.3/39.6 +/- 13.2 degrees (TIA); and 534 +/- 234/628 +/- 254 microm (AOD), 0.191 +/- 0.089/0.217 +/- 0.093 mm(2)(TISA), and 37.8 +/- 10.1/40.6 +/- 10.7 degrees (TIA), respectively. No significant difference was found between Visante OCT and SLOCT measurements except the temporal TISA (P = 0.034). The interobserver coefficient of variation ranged between 4.4% and 7.8% for Visante OCT and 4.9% and 7.0% for SLOCT. The spans of 95% limits of agreement of the nasal/temporal angle measurements between Visante OCT and SLOCT were 437/531 mm(2), 0.174/0.186 mm(2), and 25.3/28.0 degrees for AOD, TISA, and TIA, respectively. Although Visante OCT and SLOCT demonstrate high interobserver reproducibility for anterior chamber angle measurements, their agreement was poor.
    Preview · Article · May 2008 · Investigative ophthalmology & visual science
  • [Show abstract] [Hide abstract]
    ABSTRACT: To examine the relationship between signal strength and retinal nerve fiber layer (RNFL) thickness measured by optical coherence tomography (OCT). Observational cross-sectional study. Forty normal subjects were recruited. Retinal nerve fiber layer (RNFL) thickness was measured by Stratus OCT (Carl Zeiss Meditec, Dublin, CA). In each eye, the focusing knob was adjusted to obtain 6 images with different signal strengths ranging from 5 to 10. The relationships between signal strength and RNFL thickness were examined using the Spearman correlation coefficient. The differences of RNFL thicknesses were compared with repeated-measures analysis of variance. Retinal nerve fiber layer thicknesses measured at different signal strengths. Significant differences were observed between measurements obtained at signal strength of 10 and those obtained with signal strength of less than 10 at the superior, nasal, and temporal clock hours. RNFL thickness generally increased with the signal strength, with significant correlations found with the total average, superior, and nasal clock hours RNFL thicknesses. Optical coherence tomography RNFL measurements vary significantly with signal strength. Obtaining the maximal possible signal strength is recommended for RNFL thickness measurement.
    No preview · Article · Mar 2008 · Ophthalmology