The Heidelberg Retina Tomograph vs clinical impression in the diagnosis of glaucoma

Detecting abnormality in optic nerve head images using a feature extraction analysis

Imaging and evaluation of the optic nerve head (ONH) plays an essential part in the detection and clinical management of glaucoma. The morphological characteristics of ONHs vary greatly from person to person and this variability means it is difficult to quantify them in a standardized way. We developed and evaluated a feature extraction approach using shift-invariant wavelet packet and kernel principal component analysis to quantify the shape features in ONH images acquired by scanning laser ophthalmoscopy (Heidelberg Retina Tomograph [HRT]). The methods were developed and tested on 1996 eyes from three different clinical centers. A shape abnormality score (SAS) was developed from extracted features using a Gaussian process to identify glaucomatous abnormality. SAS can be used as a diagnostic index to quantify the overall likelihood of ONH abnormality. Maps showing areas of likely abnormality within the ONH were also derived. Diagnostic performance of the technique, as estimated by ROC analysis, was significantly better than the classification tools currently used in the HRT software - the technique offers the additional advantage of working with all images and is fully automated.

Heidelberg Retina Tomograph (HRT3) in population-based epidemiology: normative values and criteria for glaucomatous optic neuropathy

PURPOSE

To establish normative values for Heidelberg Retina Tomograph (HRT3) variables and to develop HRT3-based criteria for glaucomatous optic neuropathy for epidemiological research in a white population.

METHODS

Consecutive participants in the Rotterdam Study were examined with HRT and simultaneous stereoscopic fundus photography (ImageNet) in addition to other ophthalmic examinations including intraocular pressure (IOP) measurements and perimetry. Normative values for all HRT3 variables were determined in participants who met all the following criteria: no glaucomatous visual field loss (GVFL), an IOP of 21mmHg or less, no IOP lowering treatment, and a negative family history of glaucoma. Sensitivity was determined in participants with glaucomatous visual field loss at a fixed high specificity of 97.5% - a value commonly used in population-based epidemiology.

RESULTS

A total of 2516 participants were included in this study of whom 66 had glaucomatous visual field loss in at least one eye and 1680 fulfilled the criteria for contributing to the normative values. The HRT3 linear cup-disc ratio (LCDR) variable, adjusted for disc area, showed the highest sensitivity, 35%, at the required specificity of 97.5%. The 97.5th percentile of the LCDR was 0.67 for small discs (up to 1.5 mm(2)), 0.71 [corrected] for medium-sized discs and 0.76 [corrected] for large discs (above 2.0 mm(2)).The HRT3 Glaucoma Probability Score and previously published linear discriminant functions showed a lower sensitivity than LCDR at this specificity.

CONCLUSIONS

At the high specificity of 97.5% as is commonly used in population-based epidemiology, the sensitivity of the HRT3 is low - albeit not lower than that of the vertical cup-disc ratio as assessed with simultaneous stereoscopic fundus photography and analyzed with the ImageNet software. The LCDR variable, stratified for disc area, seems to be the most suitable variable to develop criteria for glaucomatous optic neuropathy for epidemiological purposes.

Exploring the Heidelberg Retinal Tomograph 3 diagnostic accuracy across disc sizes and glaucoma stages: a multicenter study

PURPOSE

To investigate and compare the diagnostic accuracy of the Heidelberg Retinal Tomograph 3 (HRT3) diagnostic algorithms and establish whether they are affected by optic disc size and glaucoma severity.

DESIGN

Multicenter cross-sectional evaluation of diagnostic tests.

PARTICIPANTS

Two hundred forty-two eyes from 139 normal subjects and 103 glaucomatous patients classified by the presence of a repeatable visual field (VF) defect.

TESTING

Eyes were imaged by the HRT3. The diagnostic accuracies of Moorfields regression analysis (MRA) and the glaucoma probability score (GPS) was explored by sensitivity and specificity and area under the receiver operating characteristics curves (AUC). The analysis was performed globally and by optic disc size quartiles and by 3 VF severity groups.

MAIN OUTCOME MEASURES

Sensitivity, specificity, and AUC.

RESULTS

The GPS showed a sensitivity (80% vs. 77%) similar to and a specificity (57% vs. 67%) lower than that of MRA Result. It showed a higher specificity in small discs than MRA Result (77% vs. 68%) but a low to very low specificity in medium to very large discs (medium, 61%; large, 50%; very large, 26%). Moorfields regression analysis Global showed the highest sensitivity and specificity (68% and 78%) in very large discs. R. Burke linear discriminant function (RB-LDF) and cup shape measure (CSM) showed the best and least variable AUC across optic nerve head sizes and glaucoma stages. The sensitivity of both MRA and the GPS decreased at the earlier glaucoma stages. The MRA and GPS agreement was moderate throughout the entire population and in small discs and early stage, whereas it was weaker among the other disc size and glaucoma stage subgroups.

CONCLUSIONS

HRT3 diagnostic algorithms' accuracy is moderate. The GPS is less specific and more influenced by disc size than MRA. Cup shape measure and the RB-LDF offer the best and less variable performances across different disc sizes and glaucoma stages.

False negative results in glaucoma detection with Heidelberg Retina Tomograph II

Purpose

To evaluate the rate of false negative results with the Heidelberg Retina Tomograph (HRT II) in a glaucoma practice.

Design

Cross-sectional study.

Methods

We analyzed the HRTs taken between October 2002 and October 2003 in our glaucoma clinic, and selected the patients who had a good quality image (SD < 40 μ) with a normal Moorfield’s Regression Analysis (MRA). A masked independent observer classified those patients as normal, glaucoma suspect, or glaucomatous on the basis of optic disc stereo photos (ODP) and at least 2 consecutive reliable automated perimetries. The diagnosis of glaucoma was based on a glaucomatous optic disc with a congruent, reproducible visual field defect.

Results

Four hundred and fifty patients who had undergone an HRT examination were analyzed. One hundred and nine patients had an HRT classified as normal on the MRA, and a good quality image. Fifteen of those 109 patients (13.7%) were classified as glaucomatous on the basis of an abnormal ODP with corresponding visual field defect. Seven (6.4%) patients were classified as glaucoma suspect.

Conclusion

Fourteen percent of glaucoma patients with glaucoma remained undetected with the HRT II Moorfield’s regression analysis as a sole means to detect glaucoma.

Interocular differences in optic nerve head topography of the subjects with unilateral peripapillary myelinated nerve fibers

PURPOSE

To determine the interocular differences in optic nerve head topography of the subjects with unilateral peripapillary myelinated nerve fibers.

MATERIALS AND METHODS

A total of 21 healthy subjects with unilateral peripapillary myelinated nerve fibers were included into the study. Patients had no ocular disease except refractive disorders. Optic nerve head topographic analyses of both eyes of each subject were performed using a confocal scanning laser ophthalmoscope, HRT-II (Heidelberg Retina Tomography II, version 1.6). The disc area, topography standard deviation, and a total of 12 topographic parameters were calculated by the HRT-II.

RESULTS

The mean age of the subjects was 28.3+/-3.4 years. The mean refractive error of the eyes with and without myelinated nerve fibers were -3.56+/-1.73 D and -0.98+/-0.66 D, respectively (P<0.05). There were no significant interocular differences in the disc area of the eyes with and without peripapillary myelinated nerve fibers (P>0.05). Eyes with peripapillary myelinated nerve fibers were found to have significantly less "neuroretinal rim area" and "neuroretinal rim area-to-disc area ratio" than those eyes with no myelination (P<0.05 for both). All other parameters were found not to reveal any significant interocular differences (P>0.05 for all of them). Sectorial analysis of the parameters including neuroretinal rim area and neuroretinal rim area-to-disc area ratio did not reveal any significant differences between the groups (P>0.05).

CONCLUSIONS

Neuroretinal rim area and rim area-to-disc area ratio of the eyes with peripapillary myelinated nerve fibers were found to be significantly less than that of the fellow eyes with no myelination. This should be taken into consideration when monitoring glaucoma suspects with peripapillary myelinated nerve fibers.

Agreement and repeatability for standard automated perimetry and confocal scanning laser ophthalmoscopy in the diagnostic innovations in glaucoma study

PURPOSE

To assess agreement between structural and functional testing in classifying eyes as normal or abnormal and their repeatability on two consecutive visits by means of standard automated perimetry (SAP) and confocal scanning laser ophthalmoscopy.

DESIGN

Analysis of selected data obtained from a prospective longitudinal observational cohort study, the Diagnostic Innovations in Glaucoma Study.

METHODS

One hundred fifty-one participants with a SAP and a Heidelberg Retina Tomograph (HRT) test within a three-month window at two visits within 15 months were included. Eyes were classified by SAP and HRT at each visit. Agreement and repeatability were assessed by kappa statistics.

RESULTS

At visit 1, 33 (22%) of 151 eyes had only SAP defects, 11 (7%) eyes had only HRT defects, and 35 (23%) eyes had both SAP and HRT defects. Seventy-two eyes (48%) were classified as normal by both tests. Similar results were obtained for visit 2. The agreement between SAP and HRT in classifying eyes was 70% (kappa = 0.393) at visit one and 68% (kappa = 0.363) at visit 2. Repeatability of classification by SAP alone, HRT alone, and both SAP and HRT between visits 1 and 2 was 84% (kappa = 0.693), 89% (kappa = 0.752), and 90% (kappa = 0.723), respectively.

CONCLUSIONS

Agreement between SAP and HRT was only fair at both visits. Repeatability across visits was substantial for SAP alone, HRT alone, and for the combination of SAP and HRT. These results suggest that detection of particular features of glaucomatous damage depends on the technique used. Structural and functional tests appear complementary, and both should be used for early detection of glaucoma.

Systems for staging the amount of optic nerve damage in glaucoma: a critical review and new material

The evaluation of the appearance of the optic disk is central to the diagnosis and management of patients with glaucoma. Grouping patients into categories, monitoring change, and quantitating the rate of change all require some type of quantitative staging of the amount of damage. Though the scientific literature regarding the appearance of the optic disk in glaucoma is extensive, there is remarkably little about quantitative staging of the amount of damage. We have identified eight systems, including the cup/disk ratio system of Armaly. Most of the earlier systems suffer from a failure to take into account the importance of the size of the optic disk. Furthermore, only one system includes early amounts of damage. This review is a critical appraisal of the known methods for staging optic disk damage in glaucoma, including the recent Disk Damage Likelihood Scale, which appears to offer substantial advantages over the other systems.

Comparison of disc damage likelihood scale, cup to disc ratio, and Heidelberg retina tomograph in the diagnosis of glaucoma

AIM

To evaluate the relative diagnostic strength of cup to disc (C/D) ratio, clinical disc damage likelihood scale (DDLS), a new clinical method of documenting glaucomatous optic disc changes, and Heidelberg retina tomograph (HRT-II) in patients with glaucoma, glaucoma suspects, and normal controls.

METHOD

Consecutive observational case series. 110 eyes from 110 patients categorised as glaucoma, glaucoma suspect, or normal were examined clinically to grade the DDLS score. HRT-II examination was performed by an examiner masked to the clinical examination findings. Optic disc parameters and Moorfields regression analysis findings were recorded. Stereophotographs of the optic disc were examined independently by two glaucoma specialists in masked fashion to determine the C/D ratio. Zeiss SITA Standard 24-2 visual fields were obtained within 3 months of HRT-II and clinical examination. For each patient, the eye with the worse mean deviation of the visual field test was enrolled in the study, and each field was additionally graded by the four level Hodapp-Parrish-II-Anderson staging. Specificity and sensitivity were calculated by receiver operating characteristic (ROC) curves.

RESULTS

Mean patient age was 58 years (SD 13.3) with 45 glaucoma patients, 23 glaucoma suspects, and 42 normals. The mean deviation on Humphrey visual field assessment using SITA-Standard was -4.95 D (SD 5 D) Clinical examination using DDLS had the best predictive power with an area under the ROC curve value of 0.95 when glaucoma patients and suspects were separated from borderline or normals. This was followed by clinical examination of C/D ratio (0.84), and HRT-II Moorfields analysis (0.68). The order of diagnostic strength did not change when definite glaucoma was compared to borderline and normals.

CONCLUSIONS

The DDLS grading performs well compared to C/D ratio and HRT-II evaluation. Attention to disc diameter and to rim width may increase the value of clinical optic disc examination.

Evaluation of the influence of tilt of optic disc on the measurement of optic disc variables obtained by optical coherence tomography and confocal scanning laser ophthalmoscopy

PURPOSE

To evaluate the relationship between optic disc variables measured by confocal scanning laser ophthalmoscopy (CSLO) and optical coherence tomography (OCT).

METHODS

Fifty-one eyes in 27 non-glaucomatous patients were scanned using a CSLO-TopSStrade mark and an OCT-OCT 3000trade mark. The relationship between the following four optic disc variables-disc area (DA), cup area (CA), neuroretinal rim area (NRRA), and cup-disc area ratio (CDAR)-measured by CSLO and OCT were evaluated, and the relationship between these measurements and optic disc tilt was assessed. Horizontal (HD) and vertical diameters (VD) of the optic disc were measured from disc photographs, and by CSLO and OCT, and ratios (HD/VD) were then compared.

RESULTS

There was a good correlation in DA, CA, and CDAR except NRRA between OCT and CSLO measurements. In eyes with a tilt >/=4 degrees, DA and NRRA were measured larger, and CDAR and CA were measured smaller by OCT than by CSLO. However, in the eyes with a tilt of <4 degrees, no significant differences in measurement of disc variables were observed for the two measurement systems. HD/VD measured from disc photographs was well correlated with those determined by CSLO (r = 0.741, P < 0.0001), however, it correlated poorly with those measured by OCT in whole study eyes (r = 0.410, P = 0.008) and in eyes tilted by >/=4 degrees, respectively (P = 0.280).

CONCLUSIONS

Although CSLO and OCT measurements of the optic disc are highly correlated, discrepancy becomes prominent in eyes with a disc tilted >/=4 degrees. Therefore, analysis of the optic nerve head by OCT must be cautiously interpreted in eyes with a highly tilted disc.

Optical coherence tomography longitudinal evaluation of retinal nerve fiber layer thickness in glaucoma

OBJECTIVES

To longitudinally evaluate optical coherence tomography (OCT) peripapillary retinal nerve fiber layer thickness measurements and to compare these measurements across time with clinical status and automated perimetry.

METHODS

Retrospective evaluation of 64 eyes (37 patients) of glaucoma suspects or patients with glaucoma participating in a prospective longitudinal study. All participants underwent comprehensive clinical assessment, visual field (VF) testing, and OCT every 6 months. Field progression was defined as a reproducible decline of at least 2 dB in VF mean deviation from baseline. Progression of OCT was defined as reproducible mean retinal nerve fiber layer thinning of at least 20 mum.

RESULTS

Each patient had a median of 5 usable OCT scans at median follow-up of 4.7 years. The difference in the linear regression slopes of retinal nerve fiber layer thickness between glaucoma suspects and patients with glaucoma was nonsignificant for all variables; however, Kaplan-Meier survival curve analysis demonstrated a higher progression rate by OCT vs VF. Sixty-six percent of eyes were stable throughout follow-up, whereas 22% progressed by OCT alone, 9% by VF mean deviation alone, and 3% by VF and OCT.

CONCLUSIONS

A greater likelihood of glaucomatous progression was identified by OCT vs automated perimetry. This might reflect OCT hypersensitivity or true damage identified by OCT before detection by conventional methods.

Glaucomatous Optic Disc Hemorrhages on Confocal Scanning Laser Tomographic Images

PURPOSE

To evaluate the detectability of glaucomatous optic disc hemorrhages by confocal scanning laser tomography.

METHODS

The study included 73 eyes of 63 patients, who consecutively showed optic disc hemorrhages on 15 degrees color optic disc photographs taken at baseline or during follow-up examinations and for whom confocal scanning laser tomographic images were additionally available. Of the total number of 92 observed hemorrhages, 51 hemorrhages extended into the parapapillary region and 41 hemorrhages were restricted to the intrapapillary region. The scanning laser tomographic images were searched for the disc hemorrhages already seen on the conventional disc photographs.

RESULTS

Using the reflectivity images, 29 (32%) hemorrhages were detected on the scanning laser tomographs. None of the hemorrhages restricted to the intrapapillary region could be seen on the scanning laser tomographs. By evaluating each of the 32 single images of the scanning laser tomographic image series, 44 (48%) of the hemorrhages were identified on at least one single image. The detectability of disc hemorrhages on the scanning laser tomographs depended significantly on their extension into the parapapillary region or their intrapapillary location. Detectability of disc bleedings was statistically independent of the disc quadrant where the hemorrhage was located, width of the bleeding, size of the optic disc, neuroretinal rim, parapapillary atrophy, and type of glaucoma.

CONCLUSIONS

Confocal scanning laser tomography is not very suitable for detection or documentation of optic disc hemorrhages in patients with glaucoma.