Comparison between laser scanning tomography and computerised image analysis of the optic disc (original) (raw)
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Agreement among 3 optical imaging methods for the assessment of optic disc topography
2005
To assess the agreement of disc topography measurements between the Heidelberg Retina Tomograph (HRT II), Retinal Thickness Analyzer (RTA), and Optical Coherence Tomograph (StratusOCT). Design: Observational cross-sectional study. Participants: Forty-two randomly chosen eyes of 42 subjects. Methods: Each subject underwent HRT II, RTA, and StratusOCT examination. Two experienced examiners drew the contour lines for the HRT II and RTA. Bland and Altman plots were used to evaluate agreement for each topographic parameter among the instruments. The Spearman coefficient of rank correlation was evaluated for each topographic parameter.
British Journal of Ophthalmology, 1999
Aims-The development of imaging and measurement techniques has brought the prospect of greater objectivity in the measurement of optic disc features, and therefore better agreement between observers. The purpose of this study was to quantify and compare the variation between observers using two measurement devices. Methods-Optic disc photographs and images from the Heidelberg retina tomograph (HRT) of 30 eyes of 30 subjects were presented to six observers for analysis, and to one observer on five separate occasions. Agreement between observers was studied by comparing the analysis of each observer with the median result of the other five, and expressed as the mean difference and standard deviation of diVerences between the observer and the median. Inter-and intraobserver variation was calculated as a coeYcient of variation (mean SD/mean × 100). Results-For planimetry, agreement between observers was dependent on observer experience, for the HRT it was independent. Agreement between observers (SD of diVerences as a percentage of the median) for optic disc area was 4.0% to 7.2% (planimetry) and 3.3% to 6.0% (HRT), for neuroretinal rim area it was 10.8% to 21.0% (planimetry) and 5.2% to 9.6% (HRT). The mean interobserver coeYcient of variation for optic disc area was 8.1% (planimetry) and 4.4% (HRT), for neuroretinal rim area it was 16.3% (planimetry) and 8.1% (HRT), and (HRT only) for rim volume was 16.3%, and reference height 9.1%. HRT variability was greater for the software version 1.11 reference plane than for version 1.10. The intraobserver coeYcient of variation for optic disc area was 1.5% (planimetry) and 2.4% (HRT), for neuroretinal rim area it was 4.0% (planimetry) and 4.5% (HRT). Conclusions-Variation between observers is greatly reduced by the HRT when compared with planimetry. However, levels of variation, which may be clinically significant, remain for variables that depend on the subjective drawing of the disc margin.
British Journal of Ophthalmology, 2002
Aims: To assess the intraobserver agreement, interobserver agreement, and the agreement between a digital stereo optic disc camera (Discam) and Heidelberg retina tomograph (HRT) in measuring area cup-disc ratio (ACDR) and radial cup-disc ratio (RCDR) by two observers. Methods: The optic discs of 78 eyes of 39 people (17 cases of primary open angle glaucoma, eight normal tension glaucoma, two ocular hypertension, and 12 normal subjects) were imaged with Discam and HRT. Two observers independently drew the disc margins on the HRT mean topography images and the disc and cup margins on the Discam images. ACDR and the RCDR at various angles were measured with the two systems. Intraobserver agreement, interobserver agreement, and the agreement between the two systems were assessed by 95% tolerance limit of changes (TC) and intraclass correlation coefficient (ICC). Results: Eight eyes were excluded due to poor image quality (six Discam and two HRT). 70 eyes were analysed. The intraobserver ACDR agreement was almost perfect in both systems (ICCs = 0.97 and 0.92, and TCs = 11.0% and 15.1% in HRT and Discam respectively). The interobserver ACDR agreement was almost perfect in HRT (ICC = 0.97) and substantial in Discam (ICC = 0.79), (TCs = 10.5% and 24.5% respectively). The ACDR agreement between the two systems was substantial in observer A (ICC = 0.67) and moderate in observer B (ICC = 0.53), (TCs = 24.8% and 46.7% respectively). The HRT measured the ACDR significantly larger than the Discam (p <0.001), and the differences were significantly larger in the glaucomatous group (p <0.001). RCDR agreement between the two systems was fair to substantial in observer A (ICC = 0.36 to 0.74) and slight to moderate in observer B (ICC = 0.12 to 0.45). Both observers achieved the best RCDR agreement between the two systems at the inferior optic disc position. Conclusion: There is almost perfect intraobserver agreement in each system. The interobserver agreement was better with the HRT than the Discam. There was substantial variation in ACDR and RCDR agreement between the two systems measured by the two observers. The variation in ACDR and RCDR measurements between the two systems may be too large for interchangeable use in a clinical setting.
Variability in digital analysis of optic disc topography
Graefe's Archive for Clinical and Experimental Ophthalmology, 1988
We determined the magnitude of variability in optic disc topographical parameters on digital analysis of the optic disc using the IS 2000. The variability introduced by the system, the observer, the observer and patient, and by clinically different types of discs was assessed in the measurement of the vertical cup-to-disc ratio, horizontal cup-to-disc ratio, cup area-to-disc area, cup volume, neuroretinal rim area, and neuroretinal rim area-to-disc area. The system itself accounted for no variability. The variability introduced by one observer for the parameters ranged from 1% to 7%, and by one observer and patient from 1% to 28%. The variation among five observers ranged from l% to 55%. Direct image acquisition (using video cameras) gave results that were no different from those obtained by digitizing the slides. Contrast-enhancement techniques did not decrease observer variability. A change in the flash intensity level at which optic disc images were acquired from 94.5 to 15.0 Watt-seconds introduced a variability of 3% to 21%. These results are less variable than those obtained on clinical observation and comparable to those of the Rodenstock image analyzer in evaluating these aspects of optic disc topography.
Clinical measurement and categorization of optic disc in glaucoma patients
Indian Journal of Ophthalmology, 2009
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 mm 2), average (1.6-2.6 mm 2) and large (>2.6 mm 2) 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.
Optic disc measurement: a comparison of indirect ophthalmoscopic methods
British Journal of Ophthalmology, 1995
Aims-Two methods of indirect ophthalmoscopic estimation of optic disc size, the 78 dioptre lens and optic disc biometer were evaluated. Methods-Twenty nine eyes of 29 patients were measured by both methods and compared with optic disc size calculated using the three planimetric corrections described by Bengtsson and Krakau. Results-The closest agreement with the clinical measurements was found using correction 3. There was a significant difference between both the 78 D lens (p<0-0001) and the biometer (p=0-0027) and the planimetric results. There was also a significant difference between the two clinical methods (p<00001). Both methods showed acceptable intraobserver variation (CoV 2-45% and 3-13% respectively). Conclusion-Overall, both methods give larger measurements than planimetry; the 78 D lens by 041 mm and the biometer by 0 15 mm. Neither method gives a satisfactory estimation of optic disc size when compared with planimetry.
Arquivos brasileiros de oftalmologia
To compare the linear measurements of the optic disk cup obtained using RTVue optical coherence tomography (OCT) with those obtained using digital retinography. This is a cross-sectional study performed with digital retinography and RTVue OCT images from patients with glaucoma or patients suspected of glaucoma. In color retinography, the greatest horizontal and vertical diameters of the optic disk starting from the inner edge of the Elschnig ring were obtained using a pachymeter with a grade of 0.01 mm. In OCT, the delineation of the optic nerve was obtained automatically from the horizontal and vertical cup results. One hundred eyes from 100 subjects with a mean age of 60.1 ± 15.7 years were included. Of these, 79 were the right eye and 21 the left eye, with 61 men and 39 women. The mean horizontal cup obtained with OCT was 0.91 ± 0.10, while that obtained with retinography was 0.79 ± 0.11 (p<0.01). There was poor agreement between the evaluated methods in the measurements of op...
A comparative study of two methods of optic disc evaluation in patients of glaucoma
Oman Journal of Ophthalmology, 2013
Introduction: Glaucoma is a progressive disorder and requires serial evaluation in order to monitor disease progression and optimize therapy. Objective: The objective of this study was to determine the correlation between each of cup/disc (C/D) ratio and the disc damage likelihood scale (DDLS) with retinal nerve fiber layer (RNFL) and global indices in Humphrey field analyzer II (HFA II). Design: Cross-sectional study. Materials and Methods: A total of 50 patients diagnosed with primary open angle glaucoma were examined to grade DDLS score and C/D ratio. The average (avg) RNFL was obtained using the Fast RNFL protocol on optical coherence tomography (OCT) (4.0.2 Carl Zeiss). HFA II Swedish Interactive Threshold Algorithm Standard 24-2 visual fields were obtained within 1 month of clinical examination. The correlation of C/D ratio with avg RNFL thickness, Mean deviation and Pattern standard deviation was calculated by Pearson correlation coefficient (r). Similar coefficients were obtained for DDLS. Results: The P value for the difference in the r between C/D ratio with RNFL (−0.628) and DDLS with RNFL (−0.8369) was significant (P < 0.01) when correlation of C/D, DDLS with RNFL was considered. Conclusion: The DDLS shows stronger correlation with structural changes in OCT than C/D ratio. The disc diameter and rim width increases the value of clinical optic disc examination.
Measurement variability in digital analysis of optic discs
Documenta Ophthalmologica, 1994
The optic disc of nine patients with typical glaucomatous disc damage and ten normal controls has been studied by means of the Optic Disc Analysis program of the Topcon Image-net System. Vertical, horizontal and average cup/disc ratio (VCJD, HC/D, AC, q)), disc, cup, rim area (DA, CA,, RA), cup volume (CV) have been evaluated and the coefficient of variation (COV) of multiple measurements was calculated. For intra-observer intra-image variability assessment, sterovideographs of each disc were taken once and analyzed t0 times (COV range: 1.39-12.08%). Intra-observer interimage variability was evaluated on eight stereovideographs of each disc taken at one minute intervals (COV range: 1.63-%%).