Improving the repeatability of Heidelberg retina tomograph and Heidelberg retina tomograph II rim area measurements

Variance components in confocal scanning laser tomography measurements of neuro-retinal rim area and the effect of repeated measurements on the power to detect loss over time

PURPOSE

To estimate the variation in measurements of neuro-retinal rim area (NRA) determined by confocal scanning laser tomography and consequences for clinical follow-up.

METHODS

Altogether, 24 healthy subjects were randomized on -320 μm, Moorfields and Standard NRA plane strategies. Additionally, NRA was measured in 32 glaucoma subjects. Variance components for subjects, visits and measurements were estimated with analysis of variance. Sample sizes required to detect a 6.0 × 10^-2  mm² NRA change were estimated assuming a significance level of 0.05 and a power of 0.8. Consequences for independent group, and paired comparison design, respectively, were analysed. Further, precision in estimates within subjects over time was investigated.

RESULTS

The variation of NRA among subjects was considerably larger than the variation among visits and measurements. For glaucoma subjects, the variation among visits and measurements were of the same order but larger than in healthy subjects. It was found that independent group comparisons require inconveniently large sample sizes. Within-subject paired comparisons over time require sample sizes of below 15 subjects. The estimated variations for glaucoma subjects imply that 54 months of follow-up is required for detection of change from baseline.

CONCLUSIONS

The variance for subjects is substantial in relation to those for visits and measurements. Cross-sectional independent group comparisons of levels of NRA are unsuitable, due to considerable subject variation. Levels of NRA differences within subjects between visits can be estimated with acceptable precision. Neuro-retinal rim area (NRA) measurement can be used for long-term follow-up of glaucoma progression.

Measuring the Repeatability of Simulated Physiology in Simulators

BACKGROUND

In simulation, it may be important in some instances that the physiologic responses to given interventions are substantially repeatable. However, there is no agreed approach to evaluating the repeatability of simulators. We therefore aimed to develop such an approach.

METHODS

In repeated simulations, we evaluated the physiologic responses to 7 simple clinical interventions generated by a METI (Medical Education Technologies Incorporated, Sarasota, FL) HPS (Human Patient Simulator) simulator in connected and disconnected states and the screen-based Anesoft Anesthesia Simulator. For a selection of variables, we calculated 3 objective measures of similarity (root mean squared error, median performance error, and median absolute performance error). We also calculated divergence over time and compared 3 preprocessing techniques to reduce the effect of clinically irrelevant phase and frequency differences (simple phase shift, complex phase shift, and dynamic time warping).

RESULTS

We collected data from more than 85 hours of simulation time from 255 simulations. The Anesoft physiologic responses were reproduced exactly in each simulation for all variables and interventions. Minor divergence was present between the time series generated with the METI HPS in the connected state but not in the disconnected state. The METI HPS showed some variation between simulations in the raw data. This was most usefully quantified using median absolute performance error as an indicator and was substantially reduced by preprocessing, particularly with dynamic time warping.

CONCLUSIONS

The repeatability of the physiologic response of model-controlled simulators to simple standardized interventions can be evaluated by considering divergence over time and the median absolute performance error of individual or pooled variables, but data should be preprocessed to eliminate irrelevant phase and frequency offsets in some variables. Dynamic time warping is an effective method for this purpose.

In vivo imaging methods to assess glaucomatous optic neuropathy

The goal of this review is to summarize the most common imaging methods currently applied for in vivo assessment of ocular structure in animal models of experimental glaucoma with an emphasis on translational relevance to clinical studies of the human disease. The most common techniques in current use include optical coherence tomography and scanning laser ophthalmoscopy. In reviewing the application of these and other imaging modalities to study glaucomatous optic neuropathy, this article is organized into three major sections: 1) imaging the optic nerve head, 2) imaging the retinal nerve fiber layer and 3) imaging retinal ganglion cell soma and dendrites. The article concludes with a brief section on possible future directions.

[Structural diagnostics of course observation for glaucoma]

BACKGROUND

Imaging of the structural progression of glaucoma enables measurement of the neuroretinal rim of the optic disc, retinal nerve fibre layer and thickness of the ganglion layer.

METHODS

High resolution disc photography, laser scanning tomography, scanning laser polarimetry and optical coherence tomography (OCT) are the current methods of choice to document and measure progression of this chronic degenerative disease.

RESULTS

Loss of the neuroretinal rim is only a few mm(2) or mm(3) per year and has to be differentiated from age-related loss which shows less change over the years. The most pronounced loss is temporal both superior and inferior. Thinning of the retinal nerve fibre layer follows the same pattern with significant annual changes of only 6-7 µm. Modern OCT devices deliver measurements of the macula ganglion cell complex which can be even more sensitive than the thickness of the retinal nerve fibre layer. Qualitative criteria for structural progression are papillary hemorrhage, rarification of papillary vessels and specific changes of the retinal pigment epithelium.

CONCLUSIONS

Structural loss due to glaucoma can be imaged and measured with different methods in different tissues. The evaluation of significant changes is still the responsibility of the ophthalmologist by taking all findings into account.

Status and perspectives of neuroprotective therapies in glaucoma: the European Glaucoma Society White Paper

Glaucoma, a chronic progressive neuropathy and the most frequent cause of irreversible blindness worldwide, is commonly treated by medication or surgery aimed at lowering intraocular pressure. In view of the limited therapeutic options, the European Glaucoma Society (EGS) sponsored two Think Tank Meetings with the goal of assessing the current status and the overall perspectives for neuroprotective treatment strategies in glaucoma. The results of the meetings are summarized in this EGS White Paper.

Variability of Heidelberg Retina Tomograph parameters during exercise

PURPOSE

The purpose of this study was to determine whether exercise affects the stereometric parameters representing optic nerve head (ONH) topography.

METHODS

ONH topography, intraocular pressure (IOP) and blood pressure of 30 healthy volunteers were monitored before, during and after dynamic exercise raising systolic blood pressure by a minimum of 30 mmHg. Change in the stereometric ONH parameters was calculated.

RESULTS

IOP decreased and blood pressure increased during exercise, resulting in an increase in mean ocular perfusion pressure. Exercise was associated with an increase in variance in 17 of the 18 stereometric ONH parameters. The increase in variance was statistically significant in eight parameters, including rim area, cup/disc area ratio and cup shape measure. There was no statistically significant change in image quality. The absolute change from baseline in rim area, cup area, cup/disc area ratio, rim/disc area ratio and rim volume showed a statistically significant (p < 0.05) correlation with change in mean ocular perfusion pressure.

CONCLUSIONS

Exercise increases variability in stereometric ONH parameters. To avoid increased variance in the stereometric parameters, ONH imaging should be performed after allowing sufficient time to rest.

Test-retest variability in structural parameters measured with glaucoma imaging devices

In addition to classical stereo-disc photography, various glaucoma imaging devices were developed in the last two decades to quantitatively measure and record glaucoma-related structural parameters of the eye. In determining whether or not the glaucomatous damage progressed from baseline and in estimating the number of test results' optimal frequency needed to confirm disease progression, information relating to the test-retest variability of measurement results provided by each imaging device is indispensable. Such information enables the clinician to apply these devices in practice. The test-retest variability of a system is usually estimated using the Bland-Altman analysis and by calculating the coefficient of variation (CV), intraclass correlation coefficient (ICC), and minimum detectable changes (MDC). The reported CV, ICC, and MDC values for glaucoma-related structural parameter measurement results of stereo-disc photographs, confocal scanning laser ophthalmoscopes, scanning laser polarimeters, time-domain optical coherence tomography (OCT), spectral-domain OCT (SD-OCT), anterior-segment OCT, and ultrasound biomicroscope are systematically reviewed in this manuscript, which will enable the clinician to interpret measurement results provided by each glaucoma imaging devices and thus be useful in practice. Although SD-OCT systems may be currently prevailing because of the volume of information provided and the relatively better test-retest variability, these systems need improvement in their test-retest variability measurement capabilities.

Structural and functional abnormalities of retinal ganglion cells measured in vivo at the onset of optic nerve head surface change in experimental glaucoma

PURPOSE

To compare peripapillary retinal nerve fiber layer thickness (RNFLT), RNFL retardance, and retinal function at the onset of optic nerve head (ONH) surface topography change in experimental glaucoma (EG).

METHODS

Thirty-three rhesus macaques had three or more weekly baseline measurements in both eyes of ONH surface topography, peripapillary RNFLT, RNFL retardance, and multifocal electroretinography (mfERG). Laser photocoagulation was then applied to the trabecular meshwork of one eye to induce chronic elevation of IOP and weekly recordings continued alternating between ONH surface topography and RNFLT during one week and RNFL retardance and mfERG the next week. Data were pooled for the group at the onset of ONH surface topography change in each EG eye, which was defined as the first date when either the mean position of the disc (MPD) fell below the 95% confidence limit of each eye's individual baseline range and/or when the topographic change analysis (TCA) map was subjectively judged as having demonstrated change, whichever came first. Analysis of variance with post hoc tests corrected for multiple comparisons were used to assess parameter changes.

RESULTS

At onset of ONH surface topography change, there was no significant difference for RNFLT versus baseline or fellow control eyes. RNFL retardance and mfERG were significantly reduced in the recordings just prior (median of 9 days) to ONH onset (P < 0.01) and had progressed significantly (P < 0.001) an average of 17 days later (median of 7 days after ONH onset). RNFLT did not exhibit significant thinning until 15 days after onset of ONH surface topography change (P < 0.001).

CONCLUSIONS

These results support the hypothesis that during the course of glaucomatous neurodegeneration, axonal cytoskeletal and retinal ganglion cell functional abnormalities exist before thinning of peripapillary RNFL axon bundles begins.

Factors affecting the sensitivity and specificity of the Heidelberg Retina Tomograph parameters to glaucomatous progression in disc photographs

PURPOSE

To evaluate the factors affecting the sensitivity and specificity of the stereometric optic nerve head (ONH) parameters of the Heidelberg Retina Tomograph (HRT) to glaucomatous progression in stereoscopic ONH photographs.

METHODS

The factors affecting the sensitivity and specificity of the vertical cup : disc ratio, the cup : disc area ratio, the cup volume, the rim area and a linear discriminant function to progression were analysed. These parameters were the best indicators of progression in a retrospective study of 476 eyes. The reference standard for progression was the masked evaluation of stereoscopic ONH photographs.

RESULTS

The factors having the most significant effect on the sensitivity and specificity of the stereometric ONH parameters were the reference height difference and the mean topography standard deviation (TSD), indicating image quality. Also, the change in the TSD and age showed consistent, but variably significant, influence on all parameters tested. The sensitivity and specificity improved when there was little change in the reference height, the image quality was good and stable, and the patients were younger. The sensitivity and specificity of the vertical cup : disc ratio was improved by a large disc area and high baseline cup : disc area ratio. The rim area showed a better sensitivity and specificity for progression with a small disc area and low baseline cup : disc area ratio.

CONCLUSION

The factors affecting the sensitivity and specificity of the stereometric ONH parameters to glaucomatous progression in disc photographs are essentially the same as those affecting the measurement variability of the HRT.

Optical coherence tomography of the swollen optic nerve head: deformation of the peripapillary retinal pigment epithelium layer in papilledema

PURPOSE. To examine the biomechanical deformation of load bearing structures of the optic nerve head (ONH) resulting from raised intracranial pressure, using high definition optical coherence tomography (HD-OCT). The authors postulate that elevated intracranial pressure induces forces in the retrolaminar subarachnoid space that can deform ONH structures, particularly the peripapillary Bruch's membrane (BM) and RPE layers. METHODS. The authors compared HD-OCT optic nerve and peripapillary retinal nerve fiber layer (RNFL) findings in eyes with papilledema caused by raised intracranial pressure to findings in eyes with optic disc swelling caused by optic neuritis and nonarteritic anterior ischemic optic neuropathy (NAION), conditions without intracranial hypertension. The authors measured average thickness of the RNFL and the angle of the RPE/BM at the temporal and nasal borders of the neural canal opening. The angle was measured as positive with inward (toward the vitreous) angulation and as negative with outward angulation. RESULTS. Of 30 eyes with papilledema, 20 eyes (67%) had positive RPE/BM rim angles. One of eight optic neuritis (12%) eyes and 1 of 12 NAION (8%) eyes had positive angulation. In five eyes with papilledema, RNFL thickening increased, three of which developed positive RPE/BM angles. On follow-up, 22 papilledema eyes had a reduction of RNFL swelling, and 17 of these eyes had less positive RPE/BM angulation. CONCLUSIONS. In papilledema, the RPE/BM is commonly deflected inward, in contrast to eyes with NAION or optic neuritis. The RPE/BM angulation is presumed to be caused by elevated pressure in the subarachnoid space, does not correlate with the amount of RNFL swelling, and resolves as papilledema subsides.

Determinants of image quality of Heidelberg Retina Tomography II and its association with optic disc parameters in a population-based setting

PURPOSE

To assess the determinants of image quality of Heidelberg Retina Tomography II (HRT II) and its association with optic disc parameters in a population-based setting.

DESIGN

Population-based, cross-sectional study involving 3280 (78.7% response) Asian Malays aged 40 to 80 years.

METHODS

Three thousand fifty-six participants completed the HRT II test. Image quality was assessed using the mean pixel height standard deviation generated by the HRT II, with lower mean pixel height standard deviation indicating higher quality. Participants underwent an interviewer-administered questionnaire and a standardized ophthalmic examination, including visual acuity, applanation tonometry, gonioscopy, refraction, automated perimetry, and lens and fundus photography.

RESULTS

The mean (standard deviation) and median of mean pixel height standard deviation in the study population were 34 (34) and 23 μm respectively. In multivariate regression models, older age and the presence of visual impairment, blindness, high myopia, and cataract were significantly associated with greater mean pixel height standard deviation (P<.05 for all). People with a higher mean pixel height standard deviation were more likely to have smaller rim area and greater cup depth.

CONCLUSION

People who are older or have high myopia, visual impairment, blindness, or cataract are more likely to have poor HRT II image quality. Poorer image quality is in turn associated with smaller optic rim area and greater cup depth. These data provide useful information when the HRT instrument is used for diagnosing glaucoma in the general population.

Agreement between the Heidelberg Retina Tomograph (HRT) stereometric parameters estimated using HRT-I and HRT-II

PURPOSE

To assess agreement between Heidelberg Retina Tomograph (HRT)-I and HRT-II stereometric parameters and to determine whether parabolic error correction (PEC) to the topographies improves agreement.

METHODS

University of California San Diego Diagnostic Innovations in Glaucoma Study participants with two HRT-II examinations (n = 380) or one HRT-I and one HRT-II examinations (n = 344) acquired on the same day were included. From the group of 380 eyes, 200 eyes were randomly selected to estimate the repeatability coefficients of HRT-II rim area and volume, cup area and volume, and mean retinal nerve fiber layer (RNFL) thickness parameters (HRT-II control group), and the remaining 180 eyes were used to assess agreement between two HRT-II examinations (HRT-II study group). Agreement between stereometric parameters of HRT-I and HRT-II examinations (HRT-I vs. HRT-II study group) were assessed with (1) no PEC, (2) HRT PEC, and (3) a modified PEC. Bland-Altman plots were used to assess agreement using estimates of bias and clinical limits of agreement (CLA) based on repeatability coefficients.

RESULTS

In the HRT-II study group, agreement between stereometric parameters was good, with no statistically significant biases. For all parameters, differences were within the CLA in 94% of participants. In the HRT-I vs. HRT-II study group, there was a small statistically significant bias between the stereometric parameters, but all differences were within CLA for ≥95% of participants. In both study groups, PEC did not improve agreement.

CONCLUSIONS

Agreement between HRT-I and HRT-II stereometric parameters was good, and PEC did not improve agreement. These results suggest that HRT-I and HRT-II examinations can be used interchangeably to detect changes in stereometric parameters over time.

Glaucomatous progression in series of stereoscopic photographs and Heidelberg retina tomograph images

OBJECTIVE

To compare optic disc changes using automated analysis of Heidelberg retina tomograph (HRT) images with assessments, by glaucoma specialists, of change in stereoscopic photographs.

METHODS

Baseline and follow-up stereophotographs and corresponding HRT I series of 91 eyes from 56 patients were selected. The selection criteria were sufficiently long, good-quality HRT series (7 visits in > or =70 months of follow-up) and follow-up photographs contemporaneous with the final HRT image. Topographic change analysis (TCA), statistic image mapping (SIM), and linear regression of rim area (RALR) across time were applied to HRT series. Glaucomatous change determined from stereophotographs by expert observers was used as the reference standard.

RESULTS

Expert observers identified 33 eyes (36%) as exhibiting glaucomatous change. Altering HRT progression criteria such that 36% of eyes progressed according to each method resulted in concordance between HRT methods and stereophotograph assessment of 54% for TCA, 65% for SIM, and 67% for RALR (Cohen kappa = 0.05, 0.23, and 0.30, respectively). Receiver operating characteristic curves of the HRT analyses revealed poor precision of HRT analyses to predict stereophotograph-assessed change: areas under the curve were 0.61 for TCA, 0.62 for SIM, and 0.66 for RALR.

CONCLUSIONS

Statistical methods for detecting structural changes in HRT images exhibit only moderate agreement with each other and have poor agreement with expert-assessed change in optic disc stereophotographs.

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

PURPOSE

To evaluate the reproducibility of the Heidelberg retina tomograph (HRT) Glaucoma Probability Score (GPS) and assess its potential for monitoring progression.

DESIGN

Evaluation of diagnostic tests in a randomized, controlled clinical trial.

PARTICIPANTS

For reproducibility, we included 43 ocular hypertensive (OHT) and 31 glaucoma subjects. For progression, we included 198 OHT and 21 control subjects.

METHODS

To 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.

MAIN OUTCOME MEASURES

Reproducibility 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.

RESULTS

Reproducibility 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.

CONCLUSIONS

Changes 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.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Detection of optic nerve head neural canal opening within histomorphometric and spectral domain optical coherence tomography data sets

PURPOSE

To assess the ability to detect the neural canal opening (NCO) and its characteristics within three-dimensional (3-D) histomorphometric and 3-D spectral domain optical coherence tomography (SD-OCT) reconstructions of the optic nerve head from nonhuman primate (NHP) eyes.

METHODS

NCO was delineated within 40 radial, sagittal sections of 3-D histomorphometric reconstructions of 44 normal eyes of 38 NHPs, each perfusion fixed at IOP 10 mm Hg, and 3-D SD-OCT (Spectralis; Heidelberg Engineering, Heidelberg, Germany) volumes acquired in vivo from a separate group of 33 normal eyes of 24 NHPs. Within all reconstructions, a least-squares ellipse was fitted to the 80 NCO points. For each eye, the dimensions and plane error (a gauge of planarity) of the fitted ellipse were calculated.

RESULTS

The NCO was successfully delineated within every section of each histomorphometric and SD-OCT reconstruction. Median plane error was similar within histomorphometric and SD-OCT volumes (8 microm, range 4-19, histomorphometry, and 10 microm, range 4-26, SD-OCT) and was small relative to the size of the ellipse. Median histomorphometric ellipse dimensions were 1453 mum (major axis, range 1218-1737) and 1066 microm (minor axis, range 808-1263). Median SD-OCT ellipse dimensions were 1512 microm (major axis, range 1191-1865) and 1060 microm (minor axis, range 772-1248).

CONCLUSIONS

The NCO is biologically continuous and relatively planar within all 3-D histomorphometric and SD-OCT reconstructions. These characteristics support its further evaluation as a reference plane for cross-sectional and longitudinal measurement of optic nerve head structures using 3-D SD-OCT.

Morpho-functional follow-up of the optic nerve in treated ocular hypertension: disc morphometry and steady-state pattern electroretinogram

PURPOSE

To examine longitudinally optic disc structure and inner retinal function in treated ocular hypertension (OHT).

MATERIALS AND METHODS

A morphometric (Heidelberg Retina Tomograph, HRT) and functional (steady-state pattern electroretinogram, PERG) evaluation of 27 OHT patients treated with topical beta-blockers and/or prostaglandin analogues and prospectively followed over a 24 +/- 6 month period.

RESULTS

Compared with baseline, mean final PERG amplitude tended to increase (p < 0.01), while HRT was stable. Individual PERG amplitude increase was large (>or= 100%) in some patients (5/27), and unexplained by clinical parameters at baseline.

CONCLUSIONS

In treated OHT, functional responses may improve while disc structure remains stable. The findings suggest that OHT-associated inner retinal dysfunction is at least in part reversible with therapeutic intraocular pressure control.

New developments in Heidelberg retina tomograph for glaucoma

PURPOSE OF REVIEW

Provides an update on research on Heidelberg retina tomograph (HRT) imaging of the optic nerve head in glaucoma. Particular reference is made to work assessing recently introduced software developments.

RECENT FINDINGS

Three main areas of investigation are covered: new developments in the third major revision of the HRT operational software (HRT-3), HRT's ability to correctly classify glaucomatous optic neuropathy, and HRT's role in monitoring disease progression. The software now incorporates a larger normative database of white patients as well as new ethnic-specific databases. The main classification tools in the new software are the Moorfields regression analysis and Glaucoma Probability Score. The performance of these classification systems is influenced by the new normative databases. A number of HRT rim area progression strategies has been proposed. These appear to complement visual field progression analyses, identifying a largely different subset of progressing patients. HRT measurement variability has recently been better characterized, and promising methods of improving measurement repeatability have been described.

SUMMARY

The HRT is a promising tool for monitoring patients with, or at risk of, glaucoma, although the relationship between progressive structural and visual field change has yet to be fully elucidated. Each refinement to the instrument software requires evaluation to establish whether it constitutes an improvement in our ability to manage patients.

Evaluating the effect of the new alignment algorithm for longitudinal series of Heidelberg retina tomography images

PURPOSE

To evaluate the impact of a new image-alignment algorithm on the repeatability of longitudinal measurements obtained from Heidelberg retina tomograph (HRT) images.

METHODS

HRTI and HRTII image series from 124 patients with glaucoma or ocular hypertension were made available from previously reported studies and were reprocessed with the old and new image-alignment algorithms. Improvements afforded by the new alignment algorithm were examined by considering statistically significant improvement in repeatability of specific stereometric parameters (SP), namely rim area (RA), rim volume (RV), cup volume (CV) and cup shape measure (CSM). A further comparison was made by examining reduction in the variability of pixel-by-pixel height measures within image series.

RESULTS

In some HRT image series, the new algorithm automatically corrected obvious misalignment events that occurred with the previous algorithm. However, average improvement in repeatability of the SP in HRTI image series was not statistically significant (P = 0.13) and there was no statistically significant reduction in pixel-by-pixel height measurement variability (P =0.73). In HRTII image series, there was evidence of improvement, on average, in the repeatability of some parameters (RA, P = 0.01; RV, P = 0.02; CSM, P = 0.05), but not in CV (P = 0.22). There was a large reduction in pixel-by-pixel variability in HRTII image series (P < 0.001).

CONCLUSION

There was no evidence to show that the new algorithm improved repeatability, on average, in HRTI images. However, the application of the new algorithm to HRTII image series marginally improved repeatability in stereometric measures and yielded a significant reduction in pixel-by-pixel variability.

Monitoring glaucomatous progression using a novel Heidelberg Retina Tomograph event analysis

PURPOSE

To describe an event analysis (EA) for monitoring Heidelberg Retina Tomograph (HRT) progression and to establish specificity, detection rate, and agreement with visual field progression by application to longitudinal data.

DESIGN

Retrospective analysis of data from a randomized controlled trial.

PARTICIPANTS

One hundred ninety-eight ocular hypertensive and 21 control subjects.

METHODS

Change criteria were derived from rim area (RA) repeatability coefficients for different levels of image quality. Event analysis 1 (EA1) through EA4 were applied to longitudinal series of HRT images acquired from the ocular hypertensive and the control cohorts: EA1 (change confirmed in 2 of 3 consecutive tests in 1 or more sector), EA2 (2 of 3 in 2 or more sectors), EA3 (3 of 3 in 1 or more sector), EA4 (3 of 3 in 2 or more sectors). Specificity (1 minus false positive results) was estimated by the proportions of progressing controls and significantly improving subjects. Progression rates were compared with Advanced Glaucoma Intervention Study (AGIS) visual field (VF) criteria, an HRT trend analysis, and a VF trend analysis, with specificity matched at 95%.

MAIN OUTCOME MEASURES

Estimated specificity, progression rate, and agreement between progression techniques.

RESULTS

Specificity estimates were 76.2% to 88.1% (EA1), 94.1% to 95.2% (EA2), 92.2% to 95.2% (EA3), and 99.1% to 100% (EA4). Of ocular hypertensive (OHT) subjects, 45.4%, 28.3%, 26.3%, and 16.2% were identified as progressing by each strategy, respectively. With specificity at 95%, 12.1% of OHT subjects progressed by both EA2 and AGIS criteria, with a median time to progression of 3.2 and 3.6 years, respectively. By EA2 alone, 16.2% progressed, and 9.6% progressed by AGIS criteria alone. The RA trend analysis identified 12% of OHT subjects as progressing.

CONCLUSIONS

The HRT EA represents a simple technique, taking into account image quality. In this cohort, it had a higher detection rate of progression, at 95% specificity, than RA trend analysis and the VF progression criteria.