Ryo Asaoka

Patients have two eyes!: binocular versus better eye visual field indices.

PURPOSEnTo test the hypothesis that better eye measures overestimate binocular visual field (VF) defect severity in glaucoma.nnnMETHODSnHumphrey VFs (24-2 SITA standard) from 67 consecutive patients with glaucoma were retrospectively examined (mean age, 65 years; range, 31-88 years). The better mean deviation (MD) from the two eyes was recorded (better eye MD). Binocular integrated visual field (IVF) was constructed for each patient by merging corresponding sensitivity values from monocular VF. An IVF MD was calculated from the average of total deviation values in the IVF. The differences between better eye MD and IVF MD were assessed.nnnRESULTSnThe average IVF MD was significantly better than the average better eye MD (mean difference, 1.3 dB; 95% confidence interval [CI], 1.0-1.7 dB; P < 0.001). Twenty-four percent of patients had an IVF MD that was at least 2 dB healthier than the MD in the better eye (95% CI, 14%-34%). The size of the differences between better eye and IVF MD was significantly associated with the severity of VF defect (P < 0.001; R² = 0.44).nnnCONCLUSIONSnMonocular measures, such as better eye MD, can give the impression that a patients VF loss is more degraded than it might be under binocular viewing. This effect is more pronounced in patients with advanced VF defects. The IVF offers a rapid assessment of a patients binocular VF severity without extra testing.

The Heidelberg retina tomograph Glaucoma Probability Score: reproducibility and measurement of progression.

PURPOSEnTo evaluate the reproducibility of the Heidelberg retina tomograph (HRT) Glaucoma Probability Score (GPS) and assess its potential for monitoring progression.nnnDESIGNnEvaluation of diagnostic tests in a randomized, controlled clinical trial.nnnPARTICIPANTSnFor reproducibility, we included 43 ocular hypertensive (OHT) and 31 glaucoma subjects. For progression, we included 198 OHT and 21 control subjects.nnnMETHODSnTo study reproducibility, global GPS values were generated for HRT images acquired in a test-retest study. Images were acquired at 2 visits within 6 weeks of each other, by 2 different observers. To study progression, GPS values were generated for HRT images acquired prospectively (1993-2001). Linear regression of GPS against time was performed, with progression defined as a significant negative slope (P<0.05). Criterion specificity was estimated from the number of improving subjects (significant positive slope) and the number of progressing controls. Visual field (VF) progression in the same subjects was assessed using 3-omitting pointwise linear regression of sensitivity over time.nnnMAIN OUTCOME MEASURESnReproducibility of GPS was assessed using Bland-Altman analysis (mean difference, 95% limits of agreement). Progression was assessed by the number of OHT subjects identified as progressing, and by agreement with VF progression.nnnRESULTSnReproducibility of GPS was better at its extremes (-0.01+/-0.20 for GPS 0-0.30, and 0.02+/-0.09 for GPS 0.78-1.00) than in its mid range (0.07+/-0.54 for GPS 0.30-0.78). Estimated criterion specificity ranged from 95.2% (95% confidence interval, 76.1%-99.9%) to 96.8% (93.2%-98.5%). Twenty-five OHT subjects (12.6%) progressed by GPS, with 11 of the 25 (5.6%) also progressing by VF; 26 subjects (13.1%) progressed by VF alone.nnnCONCLUSIONSnChanges in HRT GPS values between 0.30 and 0.78 should be interpreted with caution because the index has poorer reproducibility in this range. The global GPS progression algorithm performs at least as well as previously described rim area-based HRT progression strategies.nnnFINANCIAL DISCLOSURE(S)nProprietary or commercial disclosure may be found after the references.

A novel distribution of visual field test points to improve the correlation between structure-function measurements.

PURPOSEnTo create a new visual field (VF) test grid centered at the optic disc (disc-centered field [DCF]) and to infer the combination of VF test points (structure-function field [SFF]), taken from the DCF and the conventional fovea-centered 24-2 grid (24-2) of standard automated perimetry, which yields the strongest sectorial correlation between structure-function measurements of retinal nerve fiber layer (RNFL) thickness and VF sensitivity.nnnMETHODSnIn 50 eyes with ocular hypertension or open angle glaucoma, the DCF and 24-2 VF were measured with a humphrey field analyzer II (Full Threshold strategy) and RNFL thickness was measured with Stratus optical coherence tomography. test points from the DCF and 24-2 VF Were combined and divided into 12 sectors according to the spatial distribution of the RNFL. A novel VF for structure-function studies was established using the following criteria: each sector must contain at least one or two test points (depending on the sectors location), and the combination of test points which yields the strongest structure-function correlation is selected.nnnRESULTSnThe SFF consisted of 40 test points. The structure-function correlation for the SFF was compared with the standard 24-2 VF; a multiple-comparison test for dependent groups was carried out using a percentile bootstrap method, which indicated that the sector correlation coefficients in the SFF were significantly higher than those in the 24-2 VF.nnnCONCLUSIONSnThe SFF, with fewer test locations, has a stronger structure-function correlation than the 24-2 VF. This improved correlation may help clinicians to better interpret functional measurements in relation to structural measurements.

Five-year forecasts of the Visual Field Index (VFI) with binocular and monocular visual fields

BackgroundIn clinical care, visual field (VF) damage is assessed using monocular VF testing, yet patients perceive the world binocularly. This study was conducted to compare 5-year forecasts for the Visual Field Index (VFI) generated from series of binocular and monocular VFs.MethodsSeries of ten consecutive VFs (Humphrey 24–2 Full-threshold) spanning on average 3.7 (SD: ±0.8) years from 60 eyes of 30 glaucomatous patients were retrospectively examined. The VFs of both eyes were merged to produce the integrated VF and its VFI score (Binocular VFI) was estimated. Forecasts of binocular and monocular VFIs were calculated for each patient by projecting the fitted linear regression 5xa0years ahead from the last VF following the method on the Humphrey Guided Progression Analysis (GPA) print-out. The precisions of the forecasts were calculated as the width of the 95xa0% prediction limit (PL).ResultsThe mean 5xa0year forecast for binocular VFIs was 92xa0% (SD: 11xa0%), which was significantly higher than forecasts from right and left eyes (79xa0% [SD: 19xa0%] and 82xa0% [SD: 16xa0%] respectively; Pu2009<u20090.05). The width of the 95xa0% PL for 5-year predictions with monocular VFIs (mean right eye: 29xa0% [SD: 19xa0%] and mean left eye: 27xa0% [SD: 16xa0%]) were significantly larger than that of the binocular VFI (mean: 12xa0% [SD: 7xa0%]; Pu2009<u20090.05).ConclusionsFive year forecasted VFI values using binocular measures return significantly better values, and can be made with greater confidence than those based on monocular measures. In turn, forecasts of a patient’s binocular VFI might be more relevant to estimating the patient’s future functional VF.

Visualizing the hill of vision in 3D using the free programming language ‘R’

Dear Editor, In recent years, technological innovations have enabled us to visualize complex 3D information on 2D video displays. Such developments have made a sizeable impact in ophthalmological imaging devices, including in optical coherence tomography and Heidelberg retina tomography (Heidelberg Engineering GmbH, Heidelberg, Germany). However, representations of the hill of vision (HOV) have remained planar, such as the grayscale images displayed by the Humphrey Visual Field Analyzer II (HFA II; Carl Zeiss Meditec, Inc, Dublin, CA, USA) shown in Fig. 1. To overcome this shortcoming, we have written a program in R [1] to display an interactive 3D graphical view of the HOV. R is an open-source, free software environment for statistical computing and graphics. For clinicians, a 3D representation of the HOV offers a clear snapshot of a patient’s visual field (VF) with more detail than possible in a grayscale image. In particular, in glaucoma patients, the edge and shape of a scotoma is immediately apparent in 3D. The rendered 3D image can also be colour-coded to represent the depth of defect according to the significance of the total deviation (td) or pattern deviation (pd) value. Furthermore, the 3D image could be shown to the patient as a means to better illustrate their VF, and progression, since the 3D image is more intuitive than a grayscale image. VFs were measured using the HFA II, 24–2 test pattern, a stimulus size of Goldmann III, and the SITA standard strategy. Subsequently an R program was written to display the HOVs of these data, although the program can also readily accept data from different VF machines. The R code to produce a 3D HOV can be downloaded at http://www. staff.city.ac.uk/d.crabb/visual%20fields.html. A screenshot of a glaucomatous patient’s (patient ‘a’) 3D HOV (generated from the R code) is shown next to that of a normal subject for comparison in Fig. 1. In the R software, the 3D HOV is interactive and can be rotated and examined more closely using the computer mouse. In Fig. S1 (online supplemental material), a series of ten VFs from a glaucomatous patient (patient ‘b’) who developed glaucomatous progression are shown, while in Fig. S2 (online supplemental material) the associated pattern deviation values are plotted (http://www.staff.city.ac.uk/d.crabb/ visual%20fields.html). Furthermore, animations of the 3D HOV over several VF tests (i.e., over time) can be created using software such as ImageMagick [2] to visualize changes (progression) in the HOV. In conclusion, we have developed a simple program to easily obtain a 3D interactive HOV, which gives a clear Electronic supplementary material The online version of this article (doi:10.1007/s00417-011-1861-z) contains supplementary material, which is available to authorized users. R. Asaoka : R. A. Russell :D. F. Garway-Heath NIHR Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK