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1.  Glaucoma Discrimination of Segmented Cirrus Spectral Domain Optical Coherence Tomography (SD-OCT) Macular Scans 
The British journal of ophthalmology  2012;96(11):1420-1425.
Aims
To evaluate the glaucoma discriminating ability of macular retinal layers as measured by spectral-domain optical coherence tomography (SD-OCT).
Methods
Healthy, glaucoma suspect and glaucomatous subjects had a comprehensive ocular examination, visual field testing and SD-OCT imaging (Cirrus HD-OCT; Carl Zeiss Meditec, Dublin, CA) in the macular and optic nerve head regions. OCT macular scans were segmented into macular nerve fiber layer (mNFL), ganglion cell layer with inner plexiform layer (GCIP), ganglion cell complex (GCC) (composed of mNFL and GCIP), outer retinal complex (ORC) and total retina (TR). Glaucoma discriminating ability was assessed using the area under the receiver operator characteristic curve (AUC) for all macular parameters and mean circumpapillary (cp) RNFL. Glaucoma suspects and glaucoma subjects were grouped together for the calculation of AUCs.
Results
Analysis was performed on 51 healthy, 49 glaucoma suspect and 63 glaucomatous eyes. The median visual field MD was −2.21dB (interquartile range (IQR): −6.92 to −0.35) for the glaucoma group, −0.32dB (IQR: −1.22 to 0.73) for the suspect group and −0.18dB (IQR: −0.92 to 0.71) for the healthy group. Highest age adjusted AUCs for discriminating between healthy and glaucomatous eyes were found for average GCC and GCIP (AUC=0.901 and 0.900, respectively), and their sectoral measurements: infero-temporal (0.922 and 0.913), inferior (0.904 and 0.912) and supero-temporal (0.910 and 0.897). These values were similar to the discriminating ability of the mean cpRNFL (AUC=0.913). Comparison of these AUCs did not yield any statistically significant difference (all p>0.05). Similar discrimination performance but with slight reduction in AUCs was achieved for comparison between healthy and the combination of glaucoma and glaucoma suspect eyes.
Conclusions
SD-OCT GCIP and GCC measurements showed similar glaucoma diagnostic ability and was comparable with that of cpRNFL.
doi:10.1136/bjophthalmol-2011-301021
PMCID: PMC3721629  PMID: 22914498
2.  Variation in optical coherence tomography signal quality as an indicator of retinal nerve fibre layer segmentation error 
Purpose
Commercial optical coherence tomography (OCT) systems use global signal quality indices to quantify scan quality. Signal quality can vary throughout a scan, contributing to local retinal nerve fibre layer segmentation errors (SegE). The purpose of this study was to develop an automated method, using local scan quality, to predict SegE.
Methods
Good-quality (global signal strength (SS)≥6; manufacturer specification) peripapillary circular OCT scans (fast retinal nerve fibre layer scan protocol; Stratus OCT; Carl Zeiss Meditec, Dublin, California, USA) were obtained from 6 healthy, 19 glaucoma-suspect and 43 glaucoma subjects. Scans were grouped based on SegE. Quality index (QI) values were computed for each A-scan using software of our own design. Logistic mixed-effects regression modelling was applied to evaluate SS, global mean and SD of QI, and the probability of SegE.
Results
The difference between local mean QI in SegE regions and No-SegE regions was −5.06 (95% CI −6.38 to 3.734) (p<0.001). Using global mean QI, QI SD and their interaction term resulted in the model of best fit (Akaike information criterion=191.8) for predicting SegE. Global mean QI≥20 or SS≥8 shows little chance for SegE. Once mean QI<20 or SS<8, the probability of SegE increases as QI SD increases.
Conclusions
When combined with a signal quality parameter, the variation of signal quality between A-scans provides significant information about the quality of an OCT scan and can be used as a predictor of segmentation error.
doi:10.1136/bjophthalmol-2011-300044
PMCID: PMC3375178  PMID: 21900227
3.  Retinal nerve fibre layer and visual function loss in glaucoma: the tipping point 
Aims
To determine the retinal nerve fibre layer (RNFL) thickness at which visual field (VF) damage becomes detectable and associated with structural loss.
Methods
In a prospective cross-sectional study, 72 healthy and 40 glaucoma subjects (one eye per subject) recruited from an academic institution had VF examinations and spectral domain optical coherence tomography (SD-OCT) optic disc cube scans (Humphrey field analyser and Cirrus HD-OCT, respectively). Comparison of global mean and sectoral RNFL thicknesses with VF threshold values showed a plateau of threshold values at high RNFL thicknesses and a sharp decrease at lower RNFL thicknesses. A ‘broken stick’ statistical model was fitted to global and sectoral data to estimate the RNFL thickness ‘tipping point’ where the VF threshold values become associated with the structural measurements. The slope for the association between structure and function was computed for data above and below the tipping point.
Results
The mean RNFL thickness threshold for VF loss was 75.3 μm (95% CI: 68.9 to 81.8), reflecting a 17.3% RNFL thickness loss from age-matched normative value. Above the tipping point, the slope for RNFL thickness and threshold value was 0.03 dB/μm (CI: −0.02 to 0.08) and below the tipping point, it was 0.28 dB/μm (CI: 0.18 to 0.38); the difference between the slopes was statistically significant (p<0.001). A similar pattern was observed for quadrant and clock-hour analysis.
Conclusions
Substantial structural loss (~17%) appears to be necessary for functional loss to be detectable using the current testing methods.
doi:10.1136/bjo.2010.196907
PMCID: PMC3193885  PMID: 21478200
4.  Glaucoma detection with matrix and standard achromatic perimetry 
Background
Matrix perimetry is a new iteration of frequency‐doubling technology (FDT) which uses a smaller target size in the standard achromatic perimetry presentation pattern.
Aim
To compare the performance of matrix and Swedish interactive thresholding algorithm (SITA) perimetry in detecting glaucoma diagnosed by structural assessment.
Design
Prospective cross‐sectional study.
Methods
76 eyes from 15 healthy subjects and 61 consecutive glaucoma suspects and patients with glaucoma were included. All patients underwent optic nerve head (ONH) photography, SITA and matrix perimetries, and optical coherence tomography (OCT) within a 6‐month period. Glaucoma diagnosis was established by either glaucomatous optic neuropathy or OCT by assessing retinal nerve fibre layer (RNFL) thickness. Mean deviation (MD), pattern standard deviation (PSD), glaucoma hemifield test and cluster of abnormal testing locations were recorded from matrix and SITA perimetries.
Results
Similar correlations were observed with matrix and SITA perimetry MD and PSD with either cup‐to‐disc ratio or OCT mean RNFL. The area under the receiver operating characteristic (AROC) curves of MD and PSD for discriminating between healthy and glaucomatous eyes ranged from 0.69 to 0.81 for matrix perimetry and from 0.75 to 0.77 for SITA perimetry. There were no significant differences among any corresponding matrix and SITA perimetry AROCs.
Conclusions
Matrix and SITA perimetries had similar capabilities for distinguishing between healthy and glaucomatous eyes regardless of whether the diagnosis was established by ONH or OCT–RNFL assessment.
doi:10.1136/bjo.2006.110437
PMCID: PMC1955642  PMID: 17215267
5.  Glaucoma Detection with Matrix and Standard Achromatic Perimetry 
Purpose
Matrix perimetry is a new iteration of frequency doubling technology (FDT) using a smaller target size in the standard achromatic perimetry presentation pattern. This study compared Matrix and Swedish interactive thresholding algorithm (SITA) perimetry performance in detecting glaucoma diagnosed by structural assessment.
Design
Prospective cross-sectional study.
Methods
Seventy-six eyes of 76 consecutive healthy subjects, glaucoma suspects and glaucoma patients were included. All patients underwent optic nerve head (ONH) photography, SITA and Matrix perimetry and optical coherence tomography (OCT; Stratus OCT) within a six month interval. Glaucoma diagnosis was established by either glaucomatous optic neuropathy or OCT retinal nerve fiber layer (RNFL) thickness. Mean deviation (MD), pattern standard deviation (PSD), glaucoma hemifield test (GHT) and cluster of abnormal testing locations were recorded from Matrix and SITA.
Results
Similar correlations were observed with Matrix and SITA MD and PSD with either cup-to-disc ratio or OCT mean RNFL. The area under the receiver operating characteristic (AROC) curves of MD and PSD for discriminating between healthy and glaucomatous eyes ranged from 0.69 to 0.81 for Matrix and from 0.75 to 0.77 for SITA. There were no statistically significant differences among any corresponding Matrix and SITA AROCs.
Conclusions
Matrix and SITA perimetry had similar capabilities for distinguishing between healthy and glaucomatous eyes regardless of whether the diagnosis was established by ONH or OCT RNFL assessment.
doi:10.1136/bjo.2006.110437
PMCID: PMC1955642  PMID: 17215267
Visual field; glaucoma

Results 1-5 (5)