Ultrasonographic evaluation of optic disc swelling: comparison with CSLO in idiopathic intracranial hypertension

PURPOSE: To determine the accuracy and reproducibility of ultrasonographic (US) readings of optic disc elevations in patients with papilledema compared with confocal scanning laser ophthalmoscope (CSLO) measurements. METHODS: One randomly selected eye of 22 patients with idiopathic intracranial hypertension (IIH) and a variable degree of optic disc swelling underwent five and three repeated measurements of disc height using high-resolution ultrasonography (Biovision unit; Quantel Medical, Clermont-Ferrand, France) and CSLO (Heidelberg Retina Tomograph [HRT]; Heidelberg Engineering, Heidelberg, Germany), respectively. The same procedure was assessed in 14 subjects with variable degrees of physiologic optic disc cupping. US and HRT measurements from each group were individually compared with each other to estimate the accuracy of US readings in both disc conditions in comparison with HRT data. RESULTS: Ultrasonographic readings were positively correlated with HRT measurements in both swollen (r = 0.62, P: = 0.002) and excavated disc (r = 0.84, P: < 0.0002). The 95% limits of agreement between the instruments were 0.24 +/- 0.59 mm (mean +/- 2 SD) and 0. 05 +/- 0.3 mm for swelling and cupping measurements, respectively. The coefficient of variation was 7.63% and 1.8% for swelling and 7. 93% and 5.91% for cupping, with US and HRT, respectively. CONCLUSIONS: The results indicate that US and CSLO readings are correlated i: both disc swelling and cupping conditions, but to a different extent because of a significant discrepancy in papilledema. US assessment can be considered highly reproducible. Combined US and HRT optic disc analysis may be recommended in papilledema evaluation as long as a better correlation can be demonstrated in further studies.     

Multimodal imaging of dry age‐related macular degeneration

Purpose: The purpose of this study was to understand clinical significance of near‐infrared reflectance (NIR), blue fundus autofluorescence (FAF) and near‐infrared autofluorescence (NIA) in dry age‐related macular degeneration (AMD), by correlation with fluorescein angiography (FA) and cross‐sectional spectral domain optical coherence tomography (SD OCT). Methods: We evaluated 110 eyes (62 patients, mean age: 64 ± 8 years) diagnosed with dry AMD between January 2010 and December 2010, which underwent NIR (λ = 830 nm), FAF and FA (excitation λ = 488 nm; emission λ > 500 nm), NIA (excitation λ = 787 nm; emission λ > 800 nm), and simultaneous SD OCT scanning using a combined confocal scanning laser ophthalmoscope/SD OCT device (Spectralis HRA + OCT; Heidelberg Engineering, Heidelberg, Germany). Results: Drusen showed variable increased/decreased NIR, FAF, NIA and FA, which corresponded to variable increased/decreased thickness of the retinal pigment epithelium (RPE) and possible presence of subretinal deposits on SD OCT. Geographic atrophy (GA) was present in 43/110 eyes (39.0%) and showed increased NIR and fluorescence (FA), absent FAF and NIA, and loss of RPE on SD OCT. The hyperautofluorescence of the GA margin was never larger in FAF than that in NIA, while in 16.2% of cases, it was larger in NIA than that in FAF and corresponded to mild choroidal hyperreflectivity on SD OCT. Conclusions: Simultaneous recording of SD OCT scans provided ultrastructural data for the evaluation of NIR, FAF, NIA and FA in dry AMD. Near‐infrared autofluorescence might detect earlier than FAF areas of RPE cell loss at the GA margin.     

Retinal Nerve Fiber Layer Thickness Reproducibility Using Seven Different OCT Instruments

Purpose. The clinical utility of new optical coherence tomography (OCT) instruments strongly depends on measurements reproducibility. The aim of this study was to assess retinal nerve fiber layer (RNFL) thickness reproducibility using six different spectral-domain OCTs (SD-OCTs) and one time-domain OCT. Methods. RNFL thickness (average and four quadrant) from six SD-OCTs (Spectral OCT/SLO OPKO/OTI, 3D-OCT 2000 Topcon, RS-3000 NIDEK, Cirrus HD-OCT Zeiss, RTVue-100 Optovue, and Spectralis Heidelberg) and one time-domain OCT (Stratus OCT Zeiss) was measured twice in 38 right eyes of 38 randomly chosen healthy volunteers by two masked operators. Inter- and intraoperator reproducibility was evaluated by the intraclass correlation coefficient (ICC), coefficient of variation (CV), and Bland-Altman test analysis. Instrument-to-instrument reproducibility was determined by ANOVA for repeated measures. We also tested how the devices disagree in terms of systemic bias and random error using a structural equation model. Results. Mean RNFL average thickness ranged from 90.08 μm to 106.51 μm. Cirrus and Heidelberg showed the thinnest RNFL values in all measurements, Topcon the highest. ICC, CV, and Bland-Altman plots showed variable inter- and intraoperator agreement depending on the instrument. Heidelberg demonstrated the best interoperator (ICC, 0.92; CV, 1.56%) and intraoperator (ICC, 0.94 and 0.95; CV, 1.28% and 1.26%, respectively, for operator A and operator B) agreement for average RNFL thickness. Conclusions. Heidelberg demonstrated the higher agreement in inter- and intraoperator reproducibility, Optovue the worst. In light of our error analysis results, we found that a scale bias among instruments could interfere with a thorough RNFL monitoring, suggesting that best monitoring is obtained with the same operator and the same device.     

Comparison of optic nerve head assessment with a digital stereoscopic camera (discam), scanning laser ophthalmoscopy,and stereophotography

PURPOSE: To compare computer-assisted planimetry using the Discam system (Marcher Enterprises Ltd., Hereford, UK), confocal scanning laser ophthalmoscopy (CSLO), and stereoscopic disc photography with respect to optic nerve head (ONH) measurements and glaucoma status. DESIGN: Comparative, observational case series and interobserver variability study. METHODS: Three hundred eighty-six eyes of 233 consecutive subjects were imaged with the Discam, and a subset underwent ONH evaluation with CSLO (n = 297), stereoscopic photography (n = 233), or both. Subjects were classified into normal, glaucoma suspect, and glaucoma groups based on clinical findings of slit-lamp disc examination and visual field testing. Agreement of cup-to-disc ratio measurements among the three technologies was assessed by the intraclass correlation coefficient (ICC) and areas under the receiver operator characteristic (AROC) curves. MAIN OUTCOME MEASURES: Cup-to-disc ratio as measured by Discam, CSLO, and stereography. RESULTS: Intraclass correlation coefficients calculated using the two-way random effects model for comparing Discam, CSLO, and stereography among cup-to-disc area ratio, vertical cup-to-disc ratio, and horizontal cup-to-disc ratio were 0.46 to 0.53. The ICC was higher for eyes with larger optic discs (0.51) than those with smaller ones (0.32). The ICC calculated using the fixed effects model for the Discam and CSLO comparison was 0.72. Areas under the receiver operator characteristic curves were 0.67 to 0.80 among the three technologies comparing normal with glaucomatous eyes. In general, there was no statistically significant difference between techniques with respect to sensitivity and specificity of glaucoma detection. CONCLUSIONS: There is good agreement between ONH measurements obtained by Discam, CSLO, and stereography; however, the results are not interchangeable. Similar AROC curve values among all three techniques imply that the Discam, CSLO, and stereography perform equally for the determination of glaucoma status.     

Comparison of optic nerve head topography in healthy adults using a Heidelberg retina tomograph and retinal thickness analyzer

PURPOSE: To compare optic nerve head topographies measured using a Heidelberg retina tomograph I (HRT) and a retinal thickness analyzer (RTA) and thereby to determine clinical agreement between the two devices. Also, to investigate the reproducibility of optic nerve head measurements using the HRT and RTA. METHODS: The study included 50 normal left eyes of 50 white adults. Ophthalmologic examination, keratometry, fundus photography, and examination with HRT and RTA were performed. To determine reproducibility, 10 volunteers had repeated examinations after a week. Mean (SD), median, and 5th and 95th percentiles were calculated for the HRT and RTA measurements and differences in measurements between HRT and RTA were tested for statistical significance. Clinical agreement was assessed with limits of agreement and reproducibility by a repeatability coefficient and intraclass correlation coefficient (ICC). RESULTS: Statistically significant differences (P < 0.05) between measurements by HRT and RTA were observed for all topographic parameters, except for rim area (P = 0.051) and height variation contour (P = 0.054). The limits of agreement between HRT and RTA were wide. The repeatability coefficient for HRT was good (< or =0.10) for all parameters, except for retinal nerve fibre layer (RNFL) cross-sectional area (0.28). The repeatability coefficient for RTA was >0.10 for cup area (0.15), rim area (0.19), maximum cup depth (0.13), height variation contour (0.11), and RNFL cross-sectional area (0.14). The ICC was good (> or =90%) for all parameters, except for mean RNFL thickness (89%) for HRT, and height variation contour (84%) for RTA. CONCLUSION: The observed differences within the limits of agreement were clinically important. Therefore, the two devices cannot be used interchangeably in clinical practice.     

Retinal vessel diameter can reliably be determined in minipigs using Retinal Vessel Analyser with a microscope‐mounted fundus camera

Purpose: Retinal Vessel Analyser (RVA) is a validated instrument to measure retinal vessel diameter in humans. The purpose of this study was to assess the reproducibility (inter‐observer reliability) and the repeatability (test–retest reliability) of RVA with a microscope‐mounted fundus camera to determine retinal vessel diameter in minipigs. Methods: Ocular fundus image from five anaesthetized minipigs was recorded in a digital videotape for approximately 5 min, under stable systemic arterial pressure and gas conditions. To evaluate the reproducibility, each one of two investigators used RVA to measure the diameter of the superior temporal retinal artery on five separate 30‐second video sequences from each minipig, which were the same video sequences for both investigators. To evaluate the repeatability, one investigator performed five measurements on a single, randomly selected, 30‐second video sequence from each minipig. The reproducibility was determined using the intra‐class correlation coefficient (ICC), and the repeatability was assessed using the coefficient of variation (COV). Bland–Altman plots were also used to assess agreement between the two investigators. Results: Retinal arteriolar diameter measurements with RVA in minipigs were highly reproducible. Differences between the two investigators were lower than 0.7%. The ICC was 1.00, indicating perfect reproducibility, and the mean COV was 0.18%, reflecting excellent repeatability of the measurements with RVA. Conclusion: Retinal vessel diameter can reliably be determined not only in humans, but also in minipigs, using the commercially available RVA apparatus and a microscope‐mounted fundus camera.     

Clinical evaluation of simultaneous confocal scanning laser ophthalmoscopy imaging combined with high‐resolution,spectral‐domain optical coherence tomography

Acta Ophthalmol. 2010: 88: 842–849

Abstract.

Purpose: To evaluate the clinical relevance of a new diagnostic modality, simultaneous confocal scanning laser ophthalmoscopy (cSLO) and high‐speed, high‐resolution, spectral‐domain optical coherence tomography (OCT), for the visualization of macular pathologies. Methods: OCT images and simultaneous recording of fluorescein angiography, indocyanine green (ICG) angiography, infrared, and blue reflectance (‘red‐free’) or fundus autofluorecence (FAF) images were obtained with a novel imaging device (Spectralis HRA + OCT; Heidelberg Engineering, Heidelberg, Germany). An optically pumped solid‐state laser generated the excitation wavelength (488 nm) required for blue reflectance, FAF and fluorescein angiography images. For ICG angiography and infrared imaging, diode laser sources at 790 and 815 nm were used. For OCT, 40 000 A‐scans per second were acquired with 7 μm axial and 14 μm lateral optical resolution. The B‐scans covering a transversal range of 30° had a scan width up to 1.536 A‐scans with a digital lateral resolution of 5 μm/pixel, a scan depth of 1.8 mm with 3.5 μm/pixel digital axial resolution and a scan rate of up to 48 B‐scans/second. In addition, volume scans could be obtained at 15, 20 and 30° fields of view. An integrated eye tracking allowed for live averaging of cSLO images as well as OCT B‐scans. Results: Early, neovascular and atrophic age‐related macular degeneration, macular telangiectasia, retinal arterial, branch vein occlusion and other pathologies were imaged, and cSLO and OCT frames correlated. Fluorescein and ICG angiographic phenomena recorded in cSLO images could be analysed accurately in corresponding OCT cross‐sections. Abnormal FAF signals were correlated to alterations at the outer retinal/retinal pigment epithelial cell layer in high‐resolution OCT scans. Three‐dimensional OCT enabled comprehensive retinal coverage. The imaging software tracked eye movements accurately. Averaging of live B‐scans enhanced image quality considerably. Conclusion: The combined cSLO/OCT system allowed for simultaneous recordings of topographic and tomographic images with accurate correlation between the confocal angiograms, FAF images as well as other imaging modes with the OCT scans. The instrument thus provides simultaneous multi‐modal imaging of retinal pathologies and disease.     

Accuracy of GDx VCC, HRT I, and clinical assessment of stereoscopic optic nerve head photographs for diagnosing glaucoma

AIMS: To determine and compare the accuracy and reproducibility of GDx variable cornea compensation (VCC) scanning laser polarimetry (SLP) with VCC, Heidelberg retina tomograph (HRT) I confocal scanning laser ophthalmoscopy (CSLO), and clinical assessment of stereoscopic optic nerve head (ONH) photographs for diagnosing glaucoma. METHODS: One eye each of 40 healthy subjects, 48 glaucoma patients, and six patients with ocular hypertension were measured with SLP-VCC and CSLO. Simultaneous stereoscopic ONH photographs were also obtained. Sixteen photographs of healthy and glaucomatous eyes were duplicated for assessing intraobserver agreement. Four glaucoma specialists, four general ophthalmologists, four residents in ophthalmology, and four optometrists classified the ONH photographs as normal or glaucomatous. For SLP-VCC, the nerve fiber indicator (NFI) was evaluated. For CSLO, the Moorfields regression analysis (MRA) and the Bathija linear discriminant function (LDF) were used. Sensitivity, specificity, percentage of correctly classified eyes, and intra- and interobserver agreement, expressed as kappa (kappa) were calculated. RESULTS: SLP-VCC had the highest diagnostic accuracy, with a sensitivity, specificity, and overall correct classification of 91.7%, 95.0% and 93.2%, respectively. CSLO, expressed as Bathija LDF and MRA, had a diagnostic accuracy comparable to glaucoma specialists and general ophthalmologists with an overall accuracy of 89.8%, 86.4%, 86.7% and 85.2%, respectively. Residents classified the fewest eyes correctly. Intraobserver agreement for classifying the ONH photographs ranged between 0.48 (within residents) and 0.78 (within glaucoma specialists). The interobserver agreement ranged between 0.45 (between residents) and 0.74 (between glaucoma specialists). The agreement between observers and CSLO MRA (kappa, 0.68) was statistically significantly higher (p<0.001; paired t-test) than between observers and SLP-VCC NFI (kappa, 0.60) and CSLO Bathija LDF (kappa, 0.62). CONCLUSION: Automated analysis of measurements with GDx VCC and HRT had a similar diagnostic accuracy for glaucoma as classification of stereoscopic ONH photographs by glaucoma specialists, thus bringing all eye-care professionals to this desirable level. The intra- and interobserver agreement for ONH analysis was only moderate to good. We think these imaging techniques may assist clinicians in diagnosing glaucoma.     

Validity of a new comprehensive pterygia grading scale for use in clinical research and clinical trial

Purpose

To determine the reliability and agreement of a new comprehensive pterygium grading scale for use in clinical research and clinical trials.

Methods

Thirty eyes with pterygia were enrolled in this study. Primary gaze position and lateral gaze position images were taken of each eye with a modified single-lens reflex camera system. Our grading scale includes five parameters: two hyperemia parameters of pterygia on two different gaze position images and three size parameters, quantifying length, width, and area of the cornea encroachment of pterygium, using ImageJ software. All images were graded on the five parameters by two masked, certified reading center graders. Two graders independently graded all the images to determine inter-grader reliability. One grader regraded the images after 3 days to determine intra-grader reliability. Intraclass correlation coefficient (ICC) and inter-rater agreement statistic (κ) calculations were performed.

Results

The intra-grader reliability for hyperemia grading was high on both primary and lateral gazing positions (κ value is 0.93 and 0.96). The inter-grader reliability for hyperemia grading was also good (κ value is 0.85 and 0.87). The mean value of width, length, and area of the cornea encroachment of pterygium was 4.31 ± 2.04 mm, 2.08 ± 1.43 mm, and 7.84 ± 7.62 mm², respectively. The intra-grader agreement on width, length, and area were excellent, with ICCs of 0.98 (95% CI 0.96–0.99), 0.99 (95% CI 0.98–1.0), and 0.97 (95% CI 0.94–0.99), respectively. The inter-grader agreement on width, length, and area were also excellent, with ICCs of 0.96 (95% CI 0.90–0.98), 0.99 (95% CI 0.98–0.99), and 0.99 (95% CI 0.97–0.99), respectively.

Conclusions

There was excellent intra- and inter-observer reproducibility with the new comprehensive grading scale. This scale could lead to the development of standardized grading assessments and quantification of pterygia that would be valid in clinical research and clinical trials.

     

Assessment of optic disc cupping with digital fundus photographs

PURPOSE: To determine the agreement between the assessment of retinal digital images by using an overlay transparency sheet and the Heidelberg retinal tomograph (HRT) in determining cup-disk ratios greater than 0.6. DESIGN: Diagnostic test comparison. METHODS: Computerized topographic and monoscopic digital images of the optic disk of 628 people aged 70 to 79 years were assessed. A grader (M.C.) defined the disk margin on HRT images, and the operation software computed the area cup-disk ratio. The same grader also determined whether the vertical cup-disk ratio on retinal images was greater than 0.6 by superimposing a transparency overlay sheet over the images. Findings of a second grader (J.G.F.) were used to establish reliability measures. RESULTS: The intragrader reliability for the overlay method and HRT was almost perfect (intraclass correlation coefficient [ICC] = 0.96 and 0.99, respectively), whereas the intergrader reliability was good (ICC = 0.77 and 0.92, respectively). A perfect agreement was found on 28 (85%) of 33 eyes between the overlay and HRT methods in determining cup-disk ratios greater than 0.6. CONCLUSIONS: The overlay transparency method appears to be a reliable and promising alternative in determining cup-disk ratios greater than 0.6 in a community screening setting.     

Comparison of 2 multiple-measurement infrared pupillometers to determine scotopic pupil diameter

PURPOSE: To compare a monocular and a binocular multiple-measurement digital infrared pupillometers for measuring scotopic pupil diameter. SETTING: Department of Ophthalmology, Loma Linda University, Loma Linda, California, USA. METHODS: Scotopic pupil size was measured after 1 minute of dark adaptation in 42 eyes of 21 volunteers. Measurements were taken twice each with 2 multiple-measurement digital infrared pupillometers, the monocular pupillometer (Neuroptics, Inc.), and the binocular pupillometer (P2000D, Procyon, Ltd.) Intraclass correlation coefficients (ICC) and limits of agreement (LOA) were used to measure repeatability and agreement of measures with each instrument and between instruments. The Wilcoxon signed rank test was used to compare variability of measurements within each instrument. RESULTS: The mean scotopic pupil size was 4.79 mm +/- 0.95 (SD) with the Procyon and 4.86 +/- 0.93 mm with the Neuroptics. Repeatability and agreement tests for the Procyon measures showed the following: ICC, 0.954; 95% confidence interval (CI), 0.916-0.975; LOA, -0.60 to 0.56; range, 1.16. The Wilcoxon signed rank test of variability gave a Z score of -2.53 (P = .01, 2 tailed). The repeated measures testing with the Neuroptics pupillometer showed the following: ICC, 0.985; 95% CI, 0.972-0.992; LOA, -0.39 to 0.26; range, 0.64; Z score, -1.15 (P = .25, 2-tailed). Repeatability and agreement tests for measures between instruments showed the following: ICC, 0.954; 95% CI, 0.916-0.975; LOA, -0.60 to 0.50; range 1.11. CONCLUSIONS: There was a high repeatability and agreement in scotopic pupil diameter for repeated measures within each device and measurements between the devices. Differences in variability in scotopic pupil diameter evaluated by the Wilcoxon signed rank test were significant only with the Procyon pupillometer.     

Correlation and Reproducibility of Retinal Vascular Geometric Measurements for Stereoscopic Retinal Images of the Same Eyes

Purpose: To assess the correlation and reproducibility of retinal vascular geometric measurements obtained from two stereo-paired fundus images.

Methods: Thirty stereoscopic pairs of color optic disc-centered photographs from the Blue Mountains Eye Study were analyzed. Side-by-side grading was performed by a single grader, using semi-automated computer software to quantify the following retinal geometric parameters: (1) retinal arteriolar/venular caliber (CRAE/CRVE); (2) arteriole-to-venule ratio (AVR); (3) branching angle; and (4) tortuosity. We used Pearson correlation (r), intra-class correlation coefficient (ICC), and Bland-Altman plots to assess within-pair correlation and reproducibility for each parameter measured.

Results: Inter- and intra-grader r and ICC were high (all r > 0.90 and ICC > 0.90), except for branching angle (ICCs between 0.69–0.83). There was no significant difference between within-pair means of all retinal vascular geometric parameters, before and after excluding poor quality images. CRAE, CRVE, AVR, and arteriolar and venular tortuosity showed very high within-pair correlation and agreement (all r > 0.80 and all ICC > 0.90 respectively). Arteriolar and venular branching angles demonstrated moderate within-pair correlation (r = 0.65 and r = 0.62, respectively) and within-pair agreement (ICC = 0.76 and ICC = 0.77, respectively).

Conclusions: Use of computer-assisted software to measure retinal vascular geometric parameters from paired fundus images was highly repeatable and is robust to differences in photographic angles of paired stereo images. Such measurements can be applied to evaluate temporal changes in longitudinal studies.     

Fundus autofluorescence related to retinal morphological and functional changes in idiopathic macular holes

Purpose: To investigate fundus autofluorescence (FAF) characteristics in relation to morphological and functional features of idiopathic macular hole (IMH). Methods: Twenty eyes of 20 consecutive patients with stage 3 or 4 macular holes were included. Fundus autofluorescence images were obtained using the Heidelberg retina angiograph 2, retinal structure was evaluated with 3‐dimensional (3‐D) imaging of Fourier‐domain optical coherence tomography (FD‐OCT), and retinal function was assessed with microperimetry‐1 (MP‐1). Results: Markedly increased FAF in the foveal centre corresponding to the macular hole, confirmed with FD‐OCT, was demonstrated in all eyes. A surrounding hypoautofluorescent ring corresponded to the subretinal fluid cuff. The area of relatively reduced FAF around the ring corresponded precisely to retinal oedema. In 15 eyes (75%), a stellate appearance with dark radiating striae was seen in the relatively reduced FAF and was correlated with intraretinal cystic changes in the outer plexiform layer, observed by FD‐OCT. Mean preoperative visual acuity was significantly poorer in eyes without a stellate appearance than in those with a stellate appearance (p = 0.023). The MP‐1 study confirmed impaired retinal function in the macular hole bed and in the area of the fluid cuff and retinal oedema. Conclusions: Fundus autofluorescence imaging reflects anatomic changes and represents the dysfunctional retinal area in IMH. The technique provides 2‐D images with 3‐D information on the retinal morphology of this disease.     

Comparison of optic nerve head parameters using Heidelberg Retina Tomograph 3 and spectral-domain optical coherence tomography

Background: To assess the agreement between the Heidelberg Retina Tomograph and Cirrus spectral‐domain optical coherence tomography (Cirrus HD‐OCT [Carl Zeiss Meditec, Dublin, CA, USA]) when measuring optic disc parameters. Design: Prospective, cross‐sectional study. Participants: A total of 96 glaucoma patients and 21 normal subjects were analysed. Methods: Optic nerve head measurements, including disc area, rim area, cup‐to‐disc ratio and cup volume were obtained using both the Cirrus HD‐OCT and Heidelberg Retina Tomograph 3 (Heidelberg Engineering GmbH, Heidelberg, Germany). Main Outcome Measurements: Bland–Altman plots were used to evaluate the agreement between each of the optic disc parameters. Results: Although Cirrus HD‐OCT values were smaller than Heidelberg Retina Tomograph 3 values for the disc and rim areas, overall the Cirrus HD‐OCT and Heidelberg Retina Tomograph 3 measurements were highly correlated (r = 0.657 to 0.821). As compared with Heidelberg Retina Tomograph 3, disc and rim areas tended to be minimized by Cirrus HD‐OCT, especially when there were large disc and rim areas, although there was no relationship between the discrepancy and the level of measurement of the cup‐to‐disc ratio. The optical coherence tomography overestimated the Heidelberg Retina Tomograph‐determined cup volume, especially when there were large cup volumes. Conclusions: Bland–Altman analyses revealed that with the exception of the cup‐to‐disc ratio, there was poor agreement between the Cirrus HD‐OCT and Heidelberg Retina Tomograph 3 morphometric measurements. In addition, with the exception of the cup‐to‐disc ratio, the optic nerve head measurements could not be directly compared between the Cirrus HD‐OCT and Heidelberg Retina Tomograph 3.     

The optic nerve head assessed with HRT in 5–16‐year‐old normal children: normal values,repeatability and interocular difference

Purpose: To investigate the normal values, repeatability and interocular difference of the optic nerve head, using Heidelberg retina tomography (HRT), in 5–16‐year‐old full‐term children with normal birth weights. Methods: Fifty‐six children with normal visual acuity and refraction were examined with HRT‐II/III. Three examinations were performed on each eye. One eye was randomized for analyses of normal values and repeatability, and 54 eyes could be evaluated. The coefficient of variance and the intraclass correlation (ICC) were calculated, and the ISNT rule was noted. The correlation between right and left eyes and the limits of difference were determined in 50 pair of eyes. Results: The mean values of disc and rim areas were 2.16 (SD 0.47) and 1.75 (SD 0.39) mm² respectively. The coefficients of variance varied between optic nerve parameters from 1.8% to 21%, and the ICCs were >0.88. All parameters except retinal nerve fibre layer thickness correlated with the disc area. The ISNT rule was fulfilled in 56% of the eyes. The interocular difference was large but not statistically significant. Conclusion: We conclude that HRT can be used in children between 5 and 16 years of age, and normal values presented in the study can be used for comparison of children with optic nerve diseases. Because the assessment of rim area varied the least, it may be the parameter to use for follow‐up. The normal large interocular difference should be taken into account when comparing eyes in the individual child.     

Heritability of optic disc and cup measured by the Heidelberg Retinal Tomography in Chinese: the Guangzhou twin eye study

PURPOSE: To assess the heritability of disc area (DA), cup area (CA), and cup-disc area ratio (CDAR) as intermediate phenotypes for glaucoma in Chinese subjects in a classic twin study. METHODS: Twins (n = 1160) aged 7 to 15 years were identified in the Guangzhou Twin Registry. Optic disc parameters were measured with a Heidelberg Retina Tomograph (HRT; Heidelberg Engineering GmbH, Heidelberg, Germany) by the same examiner and grader. Zygosity was confirmed by genotyping with 16 polymorphic markers in all same-sex twin pairs. The DA, CA, and CDAR of the right eyes were chosen as the traits of interest in the analysis. Heritability was assessed by structural variance component genetic modeling, with Mx quantitative genetic modeling software, after adjustment for age and gender. RESULTS: Of those recruited, 1114 twins were identified in the analysis, including 355 monozygotic (MZ) and 202 dizygotic (DZ) twin pairs. The intraclass correlation coefficients were 0.79 for DA, 0.83 for CA, and 0.80 for CDAR in MZ pairs and 0.30, 0.37, and 0.35, respectively, in DZ pairs. The age- and sex-adjusted variance component model identified additive genetic and unshared environmental effects (AE model) being best fit for DA, CA, and CDAR. This best-fitting model yielded 77.3% additive genetic (95%CI: 73.0%-80.8%) and 22.7% unshared environment (95% CI: 19.2%-27.0%) for DA, 82.7% (95% CI:79.4%-85.5%) and 17.3% (95% CI: 14.5%-20.6%) for CA, 78.6% (95% CI: 74.5%-82.0%) and 21.4% (95% CI: 18.0%-25.4%) for CDAR. CONCLUSIONS: The variance of optic nerve head parameters (DA, CA, and CDAR) appears to be attributable to additive genetic and unshared environmental effects. Approximately 80% of these phenotypic variances are genetically determined.     

Characteristics and reproducibility of anterior chamber angle assessment by anterior‐segment optical coherence tomography

Purpose: To evaluate the basic characteristics and reproducibility of anterior chamber angle (ACA) measurements determined by anterior‐segment optical coherence tomography (AS‐OCT) in open‐angle and primary angle closure suspect (PACS) patients. Methods: Thirty‐nine open‐angle and 18 PACS patients were imaged for ACA by AS‐OCT. Subjects underwent imaging of the nasal, temporal and inferior ACA under conditions of constant light, and darkness. For analysis, we used three ACA parameters handled by the Visante OCT software: angle opening distance at 500 μm (AOD₅₀₀), trabecular‐iris space area at 500 μm (TISA₅₀₀) and angle recess area at 500 μm (ARA₅₀₀). For determination of inter‐session reproducibility, a single well‐trained operator (D.Y.K.) scanned all patients at two different visits. For determination of inter‐operator variability, a second operator (S.B.P.) acquired another set of images independently. Three sets of images were acquired at least 24 hour apart. Results: All parameters were significantly different when measured both in light and darkness, and in the nasal and temporal quadrants. There were no significant differences between the left and right eyes in the three ACA parameters in all quadrants. The temporal angle was wider than the nasal and inferior angles. All parameters of the nasal, temporal angles had excellent inter‐session and inter‐operator reproducibility [intra‐class correlation coefficient (ICC) 0.796–0.981], but these values were slightly lower for inferior angle measurements (ICC 0.662–0.892) in both open‐angle and PACS groups. Conclusion: AS‐OCT provides quantitative and reproducible assessment of ACA. Reproducibility was lower in the inferior angle compared with the nasal and temporal angles, perhaps because of variable placement of the scleral spur.     

Clinical measurement and categorization of optic disc in glaucoma patients

Background:

Assessment of optic disc size is an important component of optic nerve head examination. Agreement between different methods of disc size measurements is not very good.

Purpose:

To assess the agreement between the disc size assessed by Heidelberg retina tomograph (HRT) and stereobiomicroscopy with a 90 diopter (D) lens. To report the clinical (measured by biomicroscopy) disc diameters of small, average and large optic discs categorized by HRT disc areas.

Setting and Design:

Observational study of subjects examined in the glaucoma clinic of a tertiary eye institute.

Materials and Methods:

Seventy-five eyes of 75 glaucoma subjects were studied. Disc diameter was measured using stereobiomicroscopy and HRT. The agreement between the two sets of measurements was assessed by intraclass correlation coefficient (ICC). Discs were classified into small (<1.6 mm²), average (1.6-2.6 mm²) and large (>2.6 mm²) depending on cutoffs provided by the manufacturers of HRT. The means (95% CI) of the corresponding vertical disc diameter in these groups were assessed.

Statistical Analysis:

ICC, Bland and Altman plots.

Results:

ICC for measurements of clinical and HRT horizontal disc diameter was 0.518 and for vertical disc diameter measurement was 0.487. The mean difference between the clinical and HRT measurements as analyzed by the Bland and Altman plot was 0.17 (95% CI, 0.13- 0.47) for horizontal and 0.22 (95% CI, 0.11- 0.54) for vertical disc diameter. Of the 75 eyes, 3 eyes had small discs, 54 average and 18 large discs. The mean clinical vertical disc diameter for small discs was 1.55 mm (95% CI, 1.2-1.7), for average discs was 1.91 mm (95% CI, 1.87-1.96) and for large discs was 2.15 mm (95% CI, 2.03–2.27).

Conclusion:

The agreement between clinical and HRT disc diameter measurements is moderate. Disc diameter measurement on stereobiomicroscopy can be used to categorize discs into small, average and large discs.     

Comparison of the influence of cataract and pupil size on retinal nerve fibre layer thickness measurements with time-domain and spectral-domain optical coherence tomography

Background: To investigate and compare the effect of cataract and pupil size on retinal nerve fibre layer (RNFL) thickness measurements using spectral‐domain optical coherence tomography (Cirrus OCT) and time‐domain OCT (Stratus OCT). Design: Prospective, hospital‐based study. Participants: Twenty‐five eyes from 25 normal subjects undergoing cataract surgery. Methods: Three retinal nerve fibre layer (RNFL) thickness measurements were taken before and after dilation, preoperatively and postoperatively, using Cirrus 200 × 200 Optic Disc Scan and Stratus Fast RNFL Scan. Main Outcome Measures: Linear regression, intraclass correlation coefficient (ICC) and coefficient of variation analysis. Results: Cataract removal caused significant increase in RNFL measurements in both modalities (Cirrus P < 0.02; Stratus P < 0.001). There was no significant difference in the increase in measurements between the two machines. Pupil dilation had variable and non‐statistically significant effect in both (P > 0.05). ICC showed excellent reproducibility with Cirrus OCT after mydriasis, preoperatively (ICC = 0.78–0.90) and postoperatively (ICC = 0.90–0.97), but poor reproducibility before mydriasis (P < 0.75). Stratus OCT achieved excellent reproducibility after cataract removal both before (ICC = 0.86–0.96) and after mydriasis (ICC = 0.92–0.95), but poor reproducibility before cataract surgery (P < 0.75). Conclusions: Cataracts, not pupil size, cause significant underestimation of RNFL measurements in both Cirrus and Stratus OCT. The extent of influence exerted does not appear different between the two instruments. Reproducibility of each machine appears to be affected differently. Mydriasis is required to achieve excellent reproducibility with Cirrus OCT, and media clarity is required with Stratus OCT.     

Reproducibility of retinal nerve fiber layer measurements across the glaucoma spectrum using optical coherence tomography

Purpose:

The purpose was to determine intra-session and inter-session reproducibility of retinal nerve fiber layer (RNFL) thickness measurements with the spectral-domain Cirrus optical coherence tomography (OCT)^® (SD-OCT) in normal and glaucomatous eyes, including a subset of advanced glaucoma.

Materials and Methods:

RNFL measurements of 40 eyes of 40 normal subjects and 40 eyes of 40 glaucomatous patients including 14 with advanced glaucoma were obtained on the Cirrus OCT^® (Carl Zeiss Meditec, Dublin, CA, USA) five times on 1-day (intra-session) and on five separate days (inter-session). Intraclass correlation coefficient (ICC), coefficient of variation (COV), and test-retest variability (TRT) values were calculated for mean and quadrant RNFL in each group separately. Reproducibility values were correlated with age and stage of glaucoma.

Results:

For intra-session reproducibility, the ICC, COV, and TRT values for mean RNFL thickness in normal eyes were 0.993, 1.96%, and 4.02 µm, respectively, 0.996, 2.39%, and 3.84 µm in glaucomatous eyes, and 0.996, 2.41%, and 3.70 µm in advanced glaucoma. The corresponding inter-session values in normal eyes were 0.992, 2.16%, and 4.09 µm, 0.995, 2.62%, and 3.98 µm in glaucoma and 0.990, 2.70%, and 4.16 µm in advanced glaucoma. The mean RNFL thickness measurements were the most reproducible while the temporal quadrant had the lowest reproducibility values in all groups. There was no correlation between reproducibility and age or mean deviation on visual fields.

Conclusions:

Peripapillary RNFL thickness measurements using Cirrus OCT^® demonstrated excellent reproducibility in normal and glaucomatous eyes, including eyes with advanced glaucoma. Mean RNFL thickness measurements appear to be the most reproducible and probably represent the best parameter to use for longitudinal follow-up.