Biomedical subjects

Jackson Woo

Publications and source records attributed to Jackson Woo.

5 recordsLinked to original sources

PubMed2005

Comparison of macular and peripapillary measurements for the detection of glaucoma: an optical coherence tomography study.

OBJECTIVE: To evaluate macular nerve fiber layer (NFL) thickness in glaucomatous damage by optical coherence tomography (OCT) and to compare its discriminating power for glaucoma and glaucoma suspects with that of total macular thickness and peripapillary NFL thickness. DESIGN: Cross-sectional, case-control, comparative study. PARTICIPANTS: A total of 133 eyes from 133 subjects including 46 normal eyes, 48 glaucoma-suspect eyes, and 39 glaucoma eyes were enrolled. METHODS: Macular NFL thickness, total macular thickness, and peripapillary NFL thickness were measured by Stratus OCT in each diagnostic group. MAIN OUTCOME MEASURES: The patterns and measurements of macular NFL, total macular, and peripapillary NFL thickness in total mean, 4 quadrants, and 12 clock hours. The discriminating power of each parameter for detection of glaucoma suspects and glaucoma was evaluated by areas under the receiver operating characteristic curve (AROC). Correspondence with visual field function was studied by linear regression analysis. RESULTS: The macular NFL profile exhibited a double-hump pattern with peaks over superonasal and inferonasal sectors. A significant difference in macular NFL thickness between normal and glaucoma-suspect groups was found at the 6-o'clock position, whereas a difference was found in all except the temporal clock hours between normal and glaucoma subjects. No significant difference in AROCs for detection of glaucoma suspects or glaucoma was found when macular NFL thickness and total macular thickness measurements were compared. However, mean macular NFL thickness demonstrated a stronger correlation with visual function than mean macular thickness (r = 0.39/R2 = 0.15 vs. r = 0.23/R2 = 0.05, P =0.042). Among all the findings, inferior peripapillary NFL thickness had the best performance in discriminating glaucoma (AROC, 0.91) and glaucoma suspects (AROC, 0.67). It also had the strongest correlation with visual function (r = 0.60/R2 = 0.36, P<0.001). CONCLUSIONS: Macular NFL thickness was significantly reduced in glaucoma. It had a similar discriminating power for glaucoma detection but a stronger correlation with visual function than total macular thickness. Peripapillary NFL thickness, however, outperformed both total macular and macular NFL thickness in terms of glaucoma detection and visual function correlation. Peripapillary NFL thickness, as a total measurement of both macular and peripheral NFL, is still the best surrogate marker in glaucoma assessment.

Case-Control Studies↗

PubMed2005

Visualization of anterior chamber angle dynamics using optical coherence tomography.

PURPOSE: To describe the technology of optical coherence tomography (OCT) in imaging the anterior chamber angles and its impact on understanding the pathophysiology of angle-closure glaucoma (ACG). DESIGN: Observational case series. PARTICIPANTS: Three subjects with, respectively, impending angle-closure attack, plateau iris syndrome, and phacomorphic glaucoma were recruited. METHODS: The anterior chamber angle in each patient was imaged with a commercially available OCT unit. The angle configurations were assessed and compared before and after laser peripheral iridotomy (LPI) and argon laser peripheral iridoplasty (ALPI). MAIN OUTCOME MEASURES: Visualization of the changes in the anterior chamber angle configurations and normalization of the intraocular pressure (IOP). RESULTS: A patient with impending angle-closure attack precipitated by a topical mydriatic agent was treated with LPI. Optical coherence tomography imaging of the anterior chamber angles was performed before and after the laser procedure. Conversion of anterior iris bowing and angle crowding to iris straightening and angle opening after LPI was demonstrated. Intraocular pressure became normalized with the change in angle configuration. The second patient presented with symptoms of intermittent angle-closure attacks and was initially diagnosed with primary ACG. Despite successful LPI, the angles remained occludable, and the IOP continued to be elevated. Optical coherence tomography was used to review the anterior chamber angle configuration and demonstrated a typical pattern compatible with the diagnosis of plateau iris syndrome. Subsequent ALPI converted the plateau configuration to open angle, with normalization of IOP and disappearance of symptoms. The third patient presented with an acute angle-closure attack and was diagnosed with phacomorphic glaucoma. Argon laser peripheral iridoplasty was performed successfully to open the angle, as evident by the OCT images, and the IOP was brought under control, together with relief of symptoms. CONCLUSIONS: The commercially available OCT unit can be practically employed for anterior chamber angle imaging. The different patterns of angle configurations are correlated with the underlying pathophysiology in different forms of ACG.

Aged↗

PubMed2005

Analysis of retinal nerve fiber layer and optic nerve head in glaucoma with different reference plane offsets, using optical coherence tomography.

PURPOSE: To evaluate the performance of retinal nerve fiber layer (RNFL) thickness and optic nerve head (ONH) parameters analyzed with different offsets of reference plane in detecting early glaucomatous changes and in correlation with visual function using optical coherence tomography (OCT). METHODS: This was a cross-sectional study consisting of 41 normal subjects and 30 with early and 40 with advanced glaucoma. RNFL thickness and ONH parameters were measured with reference planes positioned at 95, 150, and 205 microm above the level of retinal pigment epithelium (RPE). Discriminating power for early glaucoma detection and correlation with visual field MD for each parameter at different levels of reference plane were compared by using the analyses of area under the receiver operating characteristic curves (AUCs) and linear regression, respectively. RESULTS: All ONH measurements were significantly different between normal and glaucoma groups, irrespective of the level of reference plane. In normal eyes, changing the reference plane position resulted in significant differences in ONH measurements. Among all the parameters examined, integrated rim volume and RNFL thickness measured at 150 microm above the RPE showed the largest AUC (0.966) for early glaucoma detection, and the strongest correlation with visual function (r = 0.793), respectively. CONCLUSIONS: OCT analysis of the ONH and RNFL is useful for early glaucoma detection. Among the three reference planes examined in this study, measurements analyzed at 150 microm above the RPE demonstrated the best performance for glaucoma detection and correlation with visual function. Compared with ONH measurements, RNFL thickness may be a better indicator, reflecting retinal ganglion cell function and monitoring disease progression.

Cross-Sectional Studies↗

PubMed2005

Comparative study of retinal nerve fiber layer measurement by StratusOCT and GDx VCC, I: correlation analysis in glaucoma.

PURPOSE: To evaluate the average and regional correlations of retinal nerve fiber layer (RNFL) thickness measured by StratusOCT (optical coherence tomography; Carl Zeiss Meditec, Inc., Dublin, CA) and GDx VCC (Laser Diagnostic Technologies, Inc., San Diego, CA). METHODS: Eighty-nine subjects-27 normal, 21 with suspected glaucoma, and 41 with glaucoma-were included in this cross-sectional study. The total average and the mean 12-clock-hour RNFL thickness were measured with the StratusOCT and GDx VCC. The discriminating powers of the two techniques for detection of suspected glaucoma and glaucoma were compared by the area under the receiver operating characteristic curves (AUC). Correspondence between StratusOCT and GDx VCC RNFL measurements in each clock hour was examined with linear regression analysis. RESULTS: The average RNFL thickness in the normal group was measured at 101.38 +/- 7.73 and 55.26 +/- 4.32 mum by StratusOCT and GDx VCC, respectively. Both nerve fiber analyzers demonstrated a double-hump pattern in the RNFL profiles with maximum RNFL thickness located at the inferotemporal and superotemporal clock hours by the StratusOCT and the superior and inferior clock hours by the GDx VCC. Significant differences were found in the total average and the individual clock-hour RNFL thickness between StratusOCT and GDx VCC RNFL measurements in both the normal and the suspected glaucoma/glaucoma groups. The GDx VCC superior RNFL measurement demonstrated the largest AUC (0.909) for detection of suspected glaucoma and glaucoma, whereas the largest AUC (0.901) in StratusOCT was found over the inferotemporal clock hour. The total average RNFL thickness measured with StratusOCT and GDx VCC correlated highly with each other (r = 0.852). When the respective clock-hour RNFL measurements were compared, the correlation coefficient varied with the position around the optic nerve head, with the highest correlation found over the superior and inferior clock hours (11, 12, 1, 6, and 7 o'clock; all with r > 0.700) and the lowest located at the temporal clock hour (9 o'clock; r = 0.277). CONCLUSIONS: Despite the substantial differences in the values of RNFL thickness, significant correlations were observed between StratusOCT and GDx VCC RNFL measurements. The variations of the correlation coefficient around the optic nerve head suggested that GDx VCC RNFL measurement does not have a fixed relationship with that of StratusOCT and the use of site-specific RNFL birefringences may improve the estimation of RNFL thickness by the GDx VCC. Nevertheless, the GDx VCC was found to be as effective as the StratusOCT in detecting the loss of RNFL in glaucoma.

Birefringence↗

PubMed2005

Comparative study of retinal nerve fiber layer measurement by StratusOCT and GDx VCC, II: structure/function regression analysis in glaucoma.

PURPOSE: To evaluate the structure/function relationship between visual field sensitivity and retinal nerve fiber layer (RNFL) thickness measured by StratusOCT (Carl Zeiss Meditec, Inc., Dublin, CA) and GDx VCC (Laser Diagnostic Technologies, Inc., San Diego, CA). METHODS: Eighty-nine subjects (27 who had healthy eyes, 21 who were glaucoma suspect, 41 who had glaucoma) were enrolled in this cross-sectional study. RNFL thickness was measured using the StratusOCT and the GDx VCC, and visual field (VF) was examined using the Humphrey VF analyzer. The relationship between RNFL thickness and VF sensitivity-expressed in terms of mean deviation (MD) in decibel (dB) scale, unlogged 1/lambert (L), and Advanced Glaucoma Intervention Study (AGIS) and Collaborative Initial Glaucoma Treatment Study (CIGTS) VF scores-were evaluated with linear and nonlinear regression models. Coefficient of determination (R(2)) was calculated, and regression models were compared using the Akaike information criterion and the F test. RESULTS: In plotting MD against RNFL thickness, curvilinear regression models demonstrated the best fit, whereas linear regression attained the best associations when VF sensitivity was expressed in 1/L. However, when healthy subjects were excluded from the analyses, the second-order polynomial was better than linear regression in describing the relation between 1/L and GDx VCC-measured RNFL thickness. Regression profiles between AGIS/CIGTS VF scores and RNFL thickness were best described in the linear and the first-order inverse models for GDx VCC and StratusOCT RNFL measurements, respectively. In general, StratusOCT RNFL measurements achieved higher associations with visual function in all the respective regression analyses than did GDx VCC. CONCLUSIONS: Description of structure/function relationships in glaucoma depends on the choice of perimetry scale, the type of RNFL measuring device, and the characteristics of the studied groups. The higher association with visual function in StratusOCT RNFL measurements compared with that in GDx VCC suggested optical coherence tomography might be a better approach for evaluating structure/function relationships. Curvilinear regression profiles found between StratusOCT RNFL thickness and MD/VF scores provide an explanation for those longitudinal observations, showing that VFs with higher AGIS/CIGTS VF scores or worse MD at baseline are at higher risk for deterioration. Regression analysis of the structure/function profile could provide important information in the assessment of the trend and pattern of glaucoma progression.

Disease Progression↗