Laser scanning tomography of the optic nerve head in ocular hypertension and glaucoma

Glaucoma classification in 3 x 3 mm en face macular scans using deep learning in a different plexus

Glaucoma is among the leading causes of irreversible blindness worldwide. If diagnosed and treated early enough, the disease progression can be stopped or slowed down. Therefore, it would be very valuable to detect early stages of glaucoma, which are mostly asymptomatic, by broad screening. This study examines different computational features that can be automatically deduced from images and their performance on the classification task of differentiating glaucoma patients and healthy controls. Data used for this study are 3 x 3 mm en face optical coherence tomography angiography (OCTA) images of different retinal projections (of the whole retina, the superficial vascular plexus (SVP), the intermediate capillary plexus (ICP) and the deep capillary plexus (DCP)) centered around the fovea. Our results show quantitatively that the automatically extracted features from convolutional neural networks (CNNs) perform similarly well or better than handcrafted ones when used to distinguish glaucoma patients from healthy controls. On the whole retina projection and the SVP projection, CNNs outperform the handcrafted features presented in the literature. Area under receiver operating characteristics (AUROC) on the SVP projection is 0.967, which is comparable to the best reported values in the literature. This is achieved despite using the small 3 × 3 mm field of view, which has been reported as disadvantageous for handcrafted vessel density features in previous works. A detailed analysis of our CNN method, using attention maps, suggests that this performance increase can be partially explained by the CNN automatically relying more on areas of higher relevance for feature extraction.

Glaucoma Increases Retinal Surface Contour Variability as Measured by Optical Coherence Tomography

Purpose

We investigated the feasibility of glaucoma detection by measuring retinal surface contour variability (RSCV) using optical coherence tomography (OCT).

Methods

The peripapillary region in one eye of each participant was scanned over an 8 × 8 mm area with a swept source OCT prototype. The retinal surface contour was sampled at approximately 1.5- to 3.5-mm radius circles centered on the optic nerve head. The RSCV is defined as the average log value within a middle spatial frequency band of the Fourier transform to the elevation profile of the inner retinal surface. The spatial frequency band was optimized to distinguish glaucoma from normal. Nerve fiber layer thickness (NFLT) was sampled around a 1.7-mm radius circle. Glaucoma severity was assessed by automated static perimetry.

Results

We enrolled 17 glaucomatous eyes and 17 healthy eyes. A great majority of the glaucoma group were in the early stage (visual field mean deviation average −2.48 ± 3.73 dB). Significant differences were found for RSCV between glaucoma and control eyes (P < 0.003) at all radii. The area under the receiver operating characteristic curve (AROC = 0.90) of RSCV was best at the 3.5-mm radius. This was not significantly better than NFLT (AROC = 0.84). With the 99% specificity, the glaucoma detection sensitivity was 53% for RSCV and 29% for NFLT (P = 0.13).

Conclusions

Retinal surface contour variability was significantly increased in glaucoma patients. The diagnostic accuracy of RSCV was equal to NFLT in early glaucoma. Since the RSCV detects small-scale focal damage and the average NFLT measures global damage, they provide different diagnostic information that may be synergistic.

Predictive Value of HRT Stereometric Parameters and Blue-on-Yellow Perimetry Global Indices in Glaucoma-suspected Subjects

OBJECTIVE

To determine subtle changes of Heidelberg retina tomography (HRT) stereometric parameters and blue-on-yellow (B/Y) perimetry global indices for the early diagnosis of glaucoma in suspected subjects.

PATIENTS AND METHODS

Cross-sectional data on 174 eyes of 87 subjects from a larger cohort, attending the Glaucoma Department of the "G. Gennimatas" General Hospital of Athens from January 2004 to February 2014, were used in the study. Subjects were assigned to 3 groups: (a) "normals" not requiring treatment throughout the study (group 1), (b) suspects who developed glaucoma and required treatment during the study (group 2), and (c) patients with incipient glaucoma (group 3). Specific HRT and B/Y perimetry variables were compared among the 3 groups.

RESULTS

Significant differences were established for the following HRT parameters: "reference height" differed significantly between groups 1 and 2 and groups 1 and 3; "cup shape measure" differed significantly between groups 1 and 2 and groups 2 and 3. B/Y perimetry global index "mean deviation" significantly distinguished group 2 from groups 1 and 3.

CONCLUSIONS

The results of the present study suggest the predictive value of the HRT stereometric parameters "reference height" and "cup shape measure" and of the B/Y perimetry global index "mean deviation" in glaucoma-suspected subjects; further corroboration through longitudinal studies is warranted.

Agreement among graders on Heidelberg retina tomograph (HRT) topographic change analysis (TCA) glaucoma progression interpretation

PURPOSE

To evaluate agreement among experts of Heidelberg retina tomography's (HRT) topographic change analysis (TCA) printout interpretations of glaucoma progression and explore methods for improving agreement.

METHODS

109 eyes of glaucoma, glaucoma suspect and healthy subjects with ≥5 visits and 2 good quality HRT scans acquired at each visit were enrolled. TCA printouts were graded as progression or non-progression. Each grader was presented with 2 sets of tests: a randomly selected single test from each visit and both tests from each visit. Furthermore, the TCA printouts were classified with grader's individual criteria and with predefined criteria (reproducible changes within the optic nerve head, disregarding changes along blood vessels or at steep rim locations and signs of image distortion). Agreement among graders was modelled using common latent factor measurement error structural equation models for ordinal data.

RESULTS

Assessment of two scans per visit without using the predefined criteria reduced overall agreement, as indicated by a reduction in the slope, reflecting the correlation with the common factor, for all graders with no effect on reducing the range of the intercepts between the graders. Using the predefined criteria improved grader agreement, as indicated by the narrower range of intercepts among the graders compared with assessment using individual grader's criteria.

CONCLUSIONS

A simple set of predefined common criteria improves agreement between graders in assessing TCA progression. The inclusion of additional scans from each visit does not improve the agreement. We, therefore, recommend setting standardised criteria for TCA progression evaluation.

Decreased Retinal Nerve Fiber Layer Thickness in Patients with Congenital Isolated Growth Hormone Deficiency

Purpose

To evaluate the optic disc topography parameters of children with congenital isolated growth hormone deficiency (GHD) using the Heidelberg retina tomograph (HRT) in a controlled study.

Methods

This prospective study included 32 eyes of 32 patients with congenital isolated GHD and 36 eyes of 36 healthy subjects. The topographic optic disc parameters (mean cup volume, rim volume, cup area, disc area, rim area, mean cup-to-disc ratio and cup depth, retinal nerve fiber layer thickness [RNFL]) were imaged in all subjects with HRT-III (software 3.01 a-M). Pearson correlation analysis was used to investigate the correlation between right and left eyes regarding the optic disc parameters. Differences between the 2 groups were evaluated by independent t test, Mann-Whitney U test, and chi-square test.

Results

The mean RNFL thickness in children with congenital isolated GHD was found to be statistically significantly thinner than in healthy subjects (p<0.05). However, no statistically significant differences were found between the mean cup volume, rim volume, cup area, disc area, rim area, mean cup-to-disc ratio and cup depth, and mean sectorial RNFL thickness (p>0.05).

Conclusions

The results suggest that congenital GHD may lead to thinner RNFL thickness when compared with healthy subjects. This indicates that GH has an important role in the development of the neural retina.

Phase-sensitive optical coherence tomography characterization of pulse-induced trabecular meshwork displacement in ex vivo nonhuman primate eyes

Glaucoma is a blinding disease for which intraocular pressure (IOP) is the only treatable risk factor. The mean IOP is regulated through the aqueous outflow system, which contains the trabecular meshwork (TM). Considerable evidence indicates that trabecular tissue movement regulates the aqueous outflow and becomes abnormal during glaucoma; however, such motion has thus far escaped detection. The purpose of this study is to describe anovel use of a phase-sensitive optical coherence tomography (PhS-OCT) method to assess pulse-dependent TM movement. For this study, we used enucleated monkey eyes, each mounted in an anterior segment holder. A perfusion system was used to control the mean IOP as well as to provide IOP sinusoidal transients (amplitude 3 mmHg, frequency 1 pulse/second) in all experiments. Measurements were carried out at seven graded mean IOPs (5, 8, 10, 20, 30, 40, and 50 mm Hg). We demonstrate that PhS-OCT is sensitive enough to image/visualize TM movement synchronous with the pulse-induced IOP transients, providing quantitative measurements of dynamic parameters such as velocity, displacement, and strain rate that are important for assessing the biomechanical compliance of the TM. We find that the largest TM displacement is in the area closest to Schlemm's canal (SC) endothelium. While maintaining constant ocular pulse amplitude, an increase of mean IOP results in a decrease of TM displacement and mean size of the SC. These results demonstrate that the PhS-OCT is a useful imaging technique capable of assessing functional properties necessary to maintain IOP in a healthy range, offering a new diagnostic alternative for glaucoma.

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.

Comparison of optic disc topography in non-glaucomatous eyes of children with juvenile diabetes mellitus and normal children

PURPOSE

To compare the optic disc topography parameters of children with juvenile diabetes mellitus and normal children using the Heidelberg Retinal Tomograph (HRT III) (Heidelberg Engineering, Heidelberg, Germany).

METHODS

The topographic optic disc parameters (cup volume, cup area, rim volume, rim area, disc area, mean cup-to-disc ratio, and mean cup depth) of 28 non-glaucomatous eyes of 28 children with type 1 diabetes mellitus and 28 eyes of 28 age-matched healthy children were compared using the nonparametric Mann-Whitney U test.

RESULTS

No statistically significant differences were found between cup volume (P = .782), cup area (P = .878), rim volume (P = .853), disc area (P = .452), mean cup-to-disc ratio (P = .852), and mean cup depth (P = .711) of eyes of cases with diabetes mellitus and normal subjects.

CONCLUSION

This result suggests that non-glaucomatous eyes of children with type 1 diabetes mellitus and healthy subjects have similar topographic optic disc characteristics.

Determinants of agreement between the confocal scanning laser tomograph and standardized assessment of glaucomatous progression

PURPOSE

To estimate the agreement of confocal scanning laser tomograph (CSLT), topographic change analysis (TCA) with assessment of stereophotographs, and standard automated perimetry (SAP) for detecting glaucomatous progression and to identify factors associated with agreement between methods.

DESIGN

Observational cohort study.

PARTICIPANTS

We included 246 eyes of 167 glaucoma patients, glaucoma suspects, and ocular hypertensives.

METHODS

We included CSLT series (n ≥ 4 tests; mean follow-up, 4 years), stereophotographs, and SAP results in the analysis. The number of progressors by guided progression analysis (GPA, "likely progression"), progressors by masked stereophotographs assessment and progressors by TCA as determined for 3 parameters related to the number of progressed superpixels within the disc margin was determined. Agreement between progression by each TCA parameter, stereophotographs and GPA was assessed using the Kappa test. Analysis of variance with post hoc analysis was applied to identify baseline factors including image quality (standard deviation of the mean topography), disc size and disease severity (pattern standard deviation [PSD] and cup area) associated with agreement/nonagreement between methods.

MAIN OUTCOME MEASURES

Agreement in assessing glaucomatous progression between the methods including factors associated with agreement/nonagreement between methods.

RESULTS

Agreement between progression by TCA and progression by stereophotographs and/or GPA was generally poor regardless of the TCA parameter and specificity cutoffs applied. For the parameters with the strongest agreement, cluster size in disc (CSIZE(disc)) and cluster area in disc (CAREA(disc)), kappa values were 0.16 (63.9%, agreement on 134 nonprogressing eyes and 23 progressing eyes) and 0.15 (64.1%, agreement on 135 nonprogressing eyes and 22 progressing eyes) at 99% cutoff. Most of the factors evaluated were not significantly associated with agreement/nonagreement between methods (all P > 0.07). However, SAP PSD was greater in the progressors by stereophotography only group compared with the progressors by TCA only group (5.8 ± 4.7 and 2.6 ± 2.2, respectively [P = 0.003] for CSIZE(disc) at 95% specificity and 5.4 ± 4.6 and 2.5 ± 2.3, respectively [P = 0.002] for CAREA(disc) at 99% specificity).

CONCLUSIONS

Agreement for detection of longitudinal changes between TCA, stereophotography, and SAP GPA is poor. Progressors by stereophotography only tended to have more advanced disease at baseline than progressors by TCA only.

Comparison of spectral domain optical coherence tomography and color photographic imaging of the optic nerve head in management of glaucoma

BACKGROUND AND OBJECTIVE

Spectral domain optical coherence tomography (SD-OCT) allows three-dimensional imaging of the optic disc. The objective of this study was to compare optic disc and cup margins between fundus photographs and SD-OCT.

PATIENTS AND METHODS

Eighteen eyes with glaucoma were examined by a custom-built SD-OCT OCT fundus images were used to register fundus photographs and SD-OCT volume.

RESULTS

Disc margins on fundus photographs corresponded to termination of the highly reflective straight line that represented the retinal pigment epithelium (RPE) or the highly reflective curved line that connected to the RPE on the OCT B-scan images at 99.3% of the positions along the disc edges. Cup margins on fundus photographs corresponded at 73.6% of the positions to the interior border of the hyporeflective regions on the OCT fundus images.

CONCLUSIONS

Excellent to fair correspondence in the determination of disc and cup margins between fundus photographs and SD-OCT images was shown.

Optic disc morphology--rethinking shape

Morphometrics, a branch of morphology, represents the study of size and shape components of biological form and their variation in the population. Assessment of optic disc morphology is essential in the diagnosis and management of many ophthalmic disorders. Much work has been performed to characterize size-related parameters of the optic disc; however, limited information is available on shape variation in the general population. In contrast to optic disc or cup sizes, which are conceptually meaningful variables with a defined unit of measurement, there are few metric constructs by which to quantify, visualize and interpret variation in optic disc or cup shape. This has significance in ophthalmic diseases with a genetic basis as recent evidence has suggested that optic disc shape may be heritable. Conventional optic disc shape measures of 'ovality' and 'form-factor' reduce a complex structure to a single number and eliminate information of potential diagnostic relevance from further analyses. The recent advent of 'geometric morphometrics', a branch of statistics that incorporates tools from geometry, biometrics and computer graphics in the quantitative analysis of biological forms, has enabled spatial relationships in shape data to be retained during analysis. The analytical methods employed in geometric morphometrics can be separated into two distinct groups: landmark-based (e.g. Procrustes analysis, thin-plate splines) and boundary outline techniques (e.g. Fourier analysis). In this review, we summarize current approaches to the study of optic disc morphology, discuss the underlying theory of geometric morphometrics within the context of analytical techniques and then explore the contemporary relevance of the subject matter to several biological fields. Finally we illustrate the potential application of geometric morphometrics to the specific problem of optic disc shape and glaucoma assessment.

Clinicians agreement in establishing glaucomatous progression using the Heidelberg retina tomograph

PURPOSE

To assess the degree of concordance among clinicians reviewing 3 Heidelberg retina tomograph (HRT) printouts used to detect progression, the Moorfields regression analysis (MRA), the topographic change analysis (TCA), and trend analysis (TA), and to compare with progression identified by stereophotographs.

DESIGN

Observational cohort study.

PARTICIPANTS

We longitudinally followed 237 eyes of 168 patients (50 glaucomatous eyes, 187 glaucoma suspects) from the Diagnostic Innovation in Glaucoma Study (mean follow-up, 46.8+/-14.2 months), with a minimum of 4 HRT images (range, 4-8).

METHODS

Three experienced observers judged the presence of progression using the HRT follow-up printouts available for each HRT method of analysis (MRA, TCA, TA). The overall assessment was based on majority rule, with >or=2 graders agreeing on the classification.

MAIN OUTCOME MEASURES

Observers agreement in assessing HRT progression and agreement for progression or no progression between the HRT methods of analysis and the reference standard represented by masked stereophotograph assessment. The kappa test was used to assess the interobserver agreement.

RESULTS

In general, agreement among clinicians for subjective assessment of progression based on HRT printouts was moderate to good; agreement (kappa) ranged from 0.52 to 0.71 for MRA, 0.61 to 0.63 for TCA, and 0.45 to 0.74 for TA. Of the 237 eyes, 16 (6.8%) were found to progress during follow-up based on masked stereophotograph assessment. Agreement for progression/no progression between the HRT methods and stereophotography was similar among MRA (84.8%, agreement on 5 progressing eyes and 196 nonprogressing eyes; kappa = 0.14), TCA, (82.3%, agreement on 8 progressing eyes and 187 nonprogressing eyes; kappa = 0.2), and TA (84%, agreement on 2 progressing eyes and 197 nonprogressing eyes; kappa = 0.01).

CONCLUSIONS

Clinicians' agreement in identifying suspected glaucomatous progression using different HRT methods of analysis was moderate to good and was similar among all methods, including MRA, which is not designed to detect progression. Agreement between progression identified by HRT and masked stereophotograph assessment was poor. These results suggest that assessment of the HRT and stereophotography may be identifying different aspects of structural change.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosures may be found after the references.

Rarebit perimetry and optic disk topography in pediatric glaucoma

PURPOSE

To determine the relationship between visual field and optic nerve topography findings in a cohort of children with pediatric glaucoma and an age-matched and sex-matched control

SUBJECTS AND METHODS

Fifteen children, aged 6 to 15 years, with pediatric glaucoma in at least one eye and 15 age-matched and sex-matched healthy children were examined with best-corrected visual acuity and perimetry. When possible, scanning laser topography of the optic disk (ie, Heidelberg retinal tomography) was performed.

RESULTS

Of 27 eyes in 15 children with pediatric glaucoma examined with Goldmann perimetry, 15 eyes (55%) had a normal visual field. Of 24 eyes examined with Rarebit perimetry, 8 eyes (33%) showed normal results and 16 eyes (67%) showed an abnormally low hit rate (ie, the fraction of seen targets vs presented targets). Nine of the 15 eyes showing normal Goldmann visual fields had a subnormal Rarebit hit rate. All children in the control group had normal Rarebit visual fields. Heidelberg retinal tomography could be performed in all healthy children and in 22 eyes of 13 children with pediatric glaucoma. The concordance between the Heidelberg retinal tomography classification (ie, normal or glaucoma) and the Rarebit results was high (Cohen's kappa = 0.79). A statistically significant correlation (r = 0.66, P = .006) between Rarebit hit rate and Heidelberg retinal tomography glaucoma index was found in the glaucoma group.

CONCLUSIONS

Rarebit perimetry detected glaucomatous damage in various types of pediatric glaucoma, and can be assumed to be of value in both diagnosis and follow-up. In 13 children with glaucoma, Heidelberg retinal tomography could be performed. The results conformed well to Rarebit findings.

Topographic optic disc analysis by Heidelberg retinal tomography in ocular Behcet's disease

AIM

To compare the topographic characteristics of the optic discs in patients with severe and mild ocular Behçet's disease by using Heidelberg retinal tomographaphy (HRT).

METHODS

This prospective study included 47 eyes of 47 patients with ocular BD who were being followed-up at the Uveitis Clinic of the Ankara Ulucanlar Eye Research Hospital, Ankara, Turkey. The patients were divided into two groups. Group 1 consisted of 21 eyes with mild uveitis, and group 2 consisted of 26 eyes with severe uveitis. All patients underwent topographic optic disc analysis by HRT II, and the quantitative optic disc parameters of both groups were compared by non-parametric Mann-Whitney U test.

RESULTS

The mean cup volume, rim volume, cup area, disc area and cup depth in group 1 were found to be statistically significantly greater than those in group 2 (p<0.0001, p = 0.03, p = 0.021, p = 0.01 and p = 0.017, respectively), while the difference between the mean cup-to-disc ratios in group 1 and group 2 were found to be statistically insignificant (p = 0.148).

CONCLUSION

A relationship was found between the severity of ocular BD and optic disc topography determined by HRT. In eyes with smaller optic discs, uveitis was observed to have a more severe course with more frequent relapses than those with larger discs.

Glaucoma detection with the Heidelberg retina tomograph 3

PURPOSE

To compare the ability of the Heidelberg retina tomograph version 3 (HRT 3) and HRT version 2 (HRT 2) to discriminate between healthy and glaucomatous eyes.

DESIGN

Retrospective cross-sectional study.

PARTICIPANTS

Seventy-one eyes of 71 healthy volunteers and 50 eyes of 50 glaucoma patients were studied. The average visual field mean deviation of the glaucoma group was -6.03+/-5.78 dB.

INTERVENTION

All participants had comprehensive ocular examinations, perimetry, and HRT scanning within 6 months. HRT 2 data were analyzed using HRT 3 software without modifying the disc margin.

MAIN OUTCOME MEASURES

Discrimination capabilities between healthy and glaucomatous eyes were determined by areas under the receiver operating characteristics (AROCs) curves. Comparisons between corresponding AROCs obtained by HRT 2 and HRT 3 analyses were performed using the nonparametric DeLong method. Agreement between classifications as defined by the different analysis methods was quantified by kappa analysis.

RESULTS

The individual stereometric parameters with the best discrimination were linear cup/disc ratio (AROC = 0.897; 95% confidence interval [CI], 0.836-0.958) for standard HRT 3 analysis and horizontal retinal nerve fiber layer curvature (0.905) for HRT 3 glaucoma probability score (GPS) analysis. Areas under the receiver operating characteristics for discrimination between glaucomatous and healthy eyes of the overall classification by HRT 2 Moorfields regression analysis (MRA), HRT 3 MRA, and GPS were 0.927 (95% CI, 0.877-0.977), 0.934 (0.888-0.980), and 0.880 (0.812-0.948), respectively. The difference between the 3 AROCs was not significant (P = 0.44). The agreement between HRT 2 and HRT 3 overall MRA classification was good (kappa = 0.70; CI, 0.59-0.80) with HRT 3 tending to report more abnormalities than HRT 2 analysis. The agreement between overall HRT 3 MRA and overall GPS was kappa = 0.58 (CI, 0.45-0.70).

CONCLUSIONS

The glaucoma discriminating ability of the new HRT 3 software is similar to that of the previous generation HRT 2. The GPS analysis showed promising results in differentiating between healthy and glaucomatous eyes without the need for subjective operator input.

Posterior pole retinal thickness in ocular hypertension and glaucoma: early changes detected by hemispheric asymmetries

PURPOSE

To evaluate retinal thickness at the posterior pole of the fundus in ocular hypertension (OHT) and open-angle glaucoma (OAG), and to correlate morphometric findings with visual sensitivity as determined by automated perimetry.

METHODS

One randomly selected eye from 41 patients with clinical diagnosis of OHT (n = 25) or early to moderate OAG (n = 16) and 16 age-matched normal controls was examined. Retinal thickness was measured by Retinal Thickness Analyzer (RTA), acquiring 5 pre-defined scans covering the central 20 degrees of the fundus. RTA average thickness and thickness profile data, including hemispheric asymmetries calculated as relative (superior/inferior and nasal/temporal) or absolute (vertical and horizontal, ie, independent of which hemisphere was thinner) parameters, were calculated. For each eye, white-on-white Humphrey 30-2 visual field results were analyzed, in addition to standard global indices, by quantifying perimetric sensitivities for regions of the posterior pole corresponding to those sampled by the RTA.

RESULTS

On average, central retinal thickness was reduced (P < 0.05) in OAG compared with OHT or normal control eyes. Vertical hemispheric absolute thickness asymmetry was increased (P < or = 0.01) in OAG eyes compared with the other groups. Horizontal hemispheric absolute thickness asymmetry was increased (P < 0.01) in both OHT and OAG eyes, compared with control eyes. At least one of the RTA parameters was altered in 13 of 25 OHT (52%) and 12 of 16 OAG eyes (75%), most frequently involving thickness asymmetries. In OAG, but not OHT eyes, superior/inferior asymmetry was positively (r = 0.69, P < 0.01) correlated with the corresponding asymmetry in perimetric sensitivity.

CONCLUSIONS

The RTA can reveal increased hemispheric thickness asymmetries in both OHT and OAG eyes. In OAG eyes thickness asymmetries are associated with corresponding perimetric asymmetries. The findings in OHT eyes suggest that localized anatomic and functional damage to inner retina may not develop in parallel early in the disease process.

Frequency Doubling Technology and Scanning Laser Tomography in Eyes With Generalized Enlargement of Optic Disc Cupping

PURPOSE

To characterize functional and structural changes in eyes with generalized enlargement of optic disc cupping (vertical cup/disc ratio > or = 0.8), normal intraocular pressure, normal standard achromatic automated perimetry (SAP) results, and no other ophthalmoscopic findings suggesting glaucoma (large C/D eyes) using frequency doubling technology (FDT) and the Heidelberg Retina Tomograph (HRT).

METHODS

This comparative observational case series included 30 large C/D eyes (30 subjects), 17 eyes (17 patients) with early-stage normal tension glaucoma with generalized enlargement of optic disc cupping (NTG eyes), and 25 eyes from 25 normal subjects (normal eyes). Results with Humphrey 30-2, FDT N-30 threshold programs, and HRT were compared among these groups. Large C/D eyes were subdivided into FDT-normal and -abnormal eyes according to the predetermined criteria and HRT parameters were compared among them.

RESULTS

No significant difference was seen in HRT parameters between the large C/D and NTG eyes. In the large C/D eyes, FDT mean deviation was lower than in the normal eyes and higher than in the NTG eyes, whereas FDT pattern standard deviation was smaller than in the NTG eyes (P = 0.02-0.03). Among HRT parameters, only cup shape measure (CSM) showed significant negative correlation with FDT mean deviation in the large C/D eyes. Between FDT-normal and -abnormal subgroups, only CSM showed significant difference (P < 0.01).

CONCLUSION

Frequency doubling technology showed abnormalities in large C/D eyes. Only CSM showed significant correlation with FDT result and difference between those with normal and abnormal FDT results. In management of large C/D eyes, FDT and CSM will be useful to detect functional and structural change.

Estimating the clinical usefulness of optic disc biometry for detecting glaucomatous change over time

PURPOSE

First, to determine the absolute measurement precision of scanning laser ophthalmoscopy (SLO) parameters, by expressing them as 95% limits of agreement (LA(95%)). Second, to propose a method for mathematically estimating the clinical ability of a parameter to monitor disease progression, expressed as the Discriminating Capacity Index (DCI).

METHODS

We measured the optic disc of 14 healthy volunteers and 14 glaucoma patients. LA(95%)-values were calculated from the average standard deviation of three measurements on the same day for repeatability, and three measurements on separate days within a 6-week period for reproducibility. We then calculated the DCI by dividing the measurement range by its LA(95%) in healthy subjects and glaucoma patients separately. Thus, the DCI takes into account both the dynamic range of disease progression and the extent of measurement variance, providing an index of the possible clinical usefulness of a parameter. As the DCI is dimensionless it allows comparison across various parameters and across technologies.

RESULTS

In the glaucoma group, the SLO parameters with the highest DCIs were 'volume below' (DCI, 9.38) and 'mean contour depth' (DCI, 8.02). In the healthy group, 'Neuroretinal rim area' had the highest index (DCI, 2.15).

CONCLUSION

SLO optic disc biometry is uniformly reproducible and may prove a clinically useful method for glaucoma follow-up, due to the high DCI found for several parameters. The capacity to detect conversion from health to glaucoma is less pronounced, possibly due to a larger biological variability found in healthy volunteers.

Imaging in glaucoma

Structural assessment using the imaging technologies discussed herein provides reproducible quantitative measurements of posterior segment ocular structures. These measurements have been found to provide useful data for glaucoma detection in various regions of the posterior segment. Further studies are needed to evaluate the utility of these technologies for pre-perimetric glaucoma detection and for monitoring glaucoma progression over an extended period.

Determination of optic cup depth by confocal scanning laser tomography

PURPOSE

To assess whether confocal scanning laser tomography of the optic disc and clinical ophthalmoscopy using stereoscopic optic disc photographs, agree in the evaluation of the deepest part of the optic cup.

PATIENTS AND METHODS

The study included 33 eyes of patients with focal normal-pressure glaucoma. Using 15 degrees color stereoscopic optic disc photographs and dividing the optic disc into an upper and a lower half, two trained observers independently established the location of the deepest part of the cup. By selection, the two observers had made congruent judgements for all eyes in the study. All patients also underwent confocal scanning laser tomography of the optic disc using the Heidelberg Retina Tomograph (HRT). The location of the deepest "mean cup depth" was noted.

RESULTS

The deepest optic cup region based on stereoscopic evaluation of photographs and on scanning laser tomography did not correlate significantly with each other (p=0.18; chi-square test, linear-by-linear association). According to the scanning laser tomography data, the maximal optic cup depths were not correlated with the corresponding locations of maximal visual field defect (p=0.80). Using the stereo photographic data, the locations of maximal optic cup depth and maximal visual field defect were correlated (p=0.006).

CONCLUSIONS

In some glaucomatous eyes, confocal scanning laser tomographic assessment of the location of the deepest optic cup region does not agree with clinical judgement and, in contrast to clinical examination, does not correlate with the location of the maximal visual field defect.

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

PURPOSE

To compare the sensitivity and the specificity of the Heidelberg Retina Tomograph (HRT) classification of "Glaucoma" or "Normal" with that derived from clinical impression (CI) based on several parameters.

DESIGN

Consecutive observational case series.

METHODS

In a retrospective chart review of 200 left eyes of 200 consecutive patients referred to the Glaucoma Service Diagnostic Laboratory of the Wills Eye Hospital, we compared the HRT-based classification of "Glaucoma" or "Normal" with a CI classification of "Definite glaucoma," "Probably glaucoma," "Probably no glaucoma," and "No glaucoma."

RESULTS

The HRT-based diagnosis of "Glaucoma" or "Normal" had an 86% sensitivity and 68% specificity when compared with a clinical impression (CI) of "Definite glaucoma," used as a strict gold standard definition of glaucoma; an 83% sensitivity and 57% specificity when the CI "Definite glaucoma" and "Probably glaucoma" were combined as a more liberal definition of glaucoma; a 76% sensitivity and 69% specificity when the CI "Definite glaucoma," "Probably glaucoma," and "Probably no glaucoma" were combined as the most liberal definition of glaucoma. The HRT diagnosis had an 86% sensitivity and 51% specificity when compared with the groups "Probably glaucoma," "Probably no glaucoma," and "No glaucoma" combined and considered as no glaucoma.

CONCLUSIONS

In this study, HRT-based classification of "Glaucoma" or "Normal" was moderately sensitive, but not very specific when compared with the clinical impression as the gold standard. Clinicians should not rely on the HRT diagnosis alone, but should use it to supplement the impression based on an eye examination and other ancillary tests.

Optic disc cup slope and visual field indices in normal, ocular hypertensive and early glaucomatous eyes

AIM

To evaluate the correlation between internal slope analysis of the optic nerve head and visual field changes in normal eyes and those with ocular hypertension (OHT) and early glaucoma (POAG).

METHODS

One eye of each of 22 normal subjects, 21 patients with ocular hypertension, and 50 patients with glaucoma were examined using the TopSS scanning laser ophthalmoscope. A series of topographic parameters measuring the internal features of the optic discs of these patients were obtained. These findings were compared with the Humphrey visual field analysis of these patients.

RESULTS

Global topographic average slope and cup to disc ratio could discriminate between groups of normal and OHT patients (p = 0.02). All global and sector analysis parameters could discriminate normal subjects from POAG patients. The average slope parameter provided the best separation with a receiver operating characteristic curve area of 0.88. Visual field mean deviation (MD) was most closely correlated with global average slope (r = -0.60, p<10(-7)) and cup to disc ratio (r = -0.40, p<0.001). Visual field MD was also well correlated (r = -0.50, p<0.0001) with slope parameters for sectors S8, S2, and S1.

CONCLUSION

Average slope, a parameter independent of reference planes and magnification effects, is capable of discriminating groups of OHT and POAG patients from a group of normal subjects. This topographic parameter is also well correlated with the visual field MD. Sector slope analysis suggests early glaucomatous damage may occur in the inferotemporal region of the optic disc.

Frequency doubling technology and confocal scanning ophthalmoscopic optic disc analysis in open-angle glaucoma with hemifield defects

PURPOSE

To evaluate the potential of frequency doubling technology for detecting early glaucomatous damage.

PATIENTS AND METHODS

Forty-nine eyes of 49 patients with open-angle glaucoma with visual field defects only in one hemifield according to the Humphrey Field Analyzer 30-2 program were included. Forty-five healthy patients were also included as control subjects. In each patient, frequency doubling technology with the threshold N-30 program and optic disc analysis using the Heidelberg Retina Tomograph was performed. Frequency doubling technology test results and the Humphrey Field Analyzer test results were compared. Optic disc parameters corresponding to the hemifield designated intact by the Humphrey Field Analyzer were compared between the eyes in which the hemifield was normal by frequency doubling technology and those in which the hemifield was abnormal.

RESULTS

Forty-one percent of the 49 hemifields designated intact by the Humphrey Field Analyzer were abnormal based on frequency doubling technology, whereas 98% of the 49 hemifields designated defective by the Humphrey Field Analyzer were abnormal and 12% of the 90 hemifields designated intact by the Humphrey Field Analyzer were abnormal in healthy patients. The percentage of the hemifields designated abnormal by frequency doubling technology was significantly higher than that in healthy patients (P < 0.001). The rim volume was significantly smaller in eyes with abnormal results based on frequency doubling technology than in eyes with normal results (P < 0.05, paired t test, with Bonferroni correction for multiple comparison).

CONCLUSION

Frequency doubling technology can detect glaucomatous damage earlier than conventional static perimetry can.

Scanning laser ophthalmoscopy of the optic nerve head in exfoliation glaucoma and ocular hypertension with exfoliation syndrome

AIMS

To study the relation between optic nerve head topography (Heidelberg retina tomograph, HRT) and disc area, visual field index mean defect (MD), and intraocular pressure (IOP), and to see whether change in HRT parameters is associated with change in MD in a prospective follow up.

METHODS

80 consecutive patients (69 patients with exfoliation glaucoma and 11 with ocular hypertension combined with exfoliation syndrome) were examined before IOP reducing intervention and prospectively followed every 6 months for 2 years.

RESULTS

At the entry point, multiple regression analysis showed significant linear association between MD and all HRT parameters, when controlling for disc area. Disc area showed significant association with cup area, cup/disc area ratio, rim area, cup volume, and mean RNFL thickness. Six months after intervention IOP had decreased significantly. Reversible changes in cup area, cup/disc area ratio, rim area, cup volume, rim volume, mean cup depth, and maximum cup depth were associated with decrease in IOP. During the follow up period from 6 month to 2 years, IOP did not change significantly, and MD was used as a measure of progression of glaucoma. During this period, only cup shape measure among HRT parameters showed significant association with subsequent change in MD.

CONCLUSION

Disc area should be taken into account when using HRT to compare patients. Any effect of change in IOP should be also taken into account when using HRT in follow up. Cup shape measure is a promising indicator of progression of glaucomatous damage.

Slope analysis of the optic disc in eyes with ocular hypertension and early normal tension glaucoma by confocal scanning laser ophthalmoscope

AIMS

To determine whether quantitative differences in sector based slope can differentiate between eyes with ocular hypertension with and without glaucomatous disc changes and eyes with normal tension glaucoma with glaucomatous disc changes.

METHODS

Seventy six eyes with ocular hypertension or early glaucomatous disc changes were consecutively categorised into three groups: 22 eyes with ocular hypertension and no glaucomatous disc changes (OHND); 35 with ocular hypertension and glaucomatous disc changes (OHD); and 19 with normal ocular tension and glaucomatous disc changes (NTD). Twenty eyes served as controls. The average total slope angle and sector based slope angle of the cup, total contour area, effective area, neuroretinal rim area, half depth area, cup to disc ratio, contour variation, mean contour depth, average depth, volume below, half depth volume, and contour tilt were evaluated with a confocal scanning laser ophthalmoscope.

RESULTS

The earliest changes in eyes with OHND or OHD started in the slope at the nasal inferior sector (p<0.05), followed by the superior and temporal superior sectors (p<0.05). The mean slopes in eyes with NTD and OHD were steeper than in controls (p<0.05). Statistically significant differences were found between controls and disease groups in the half depth area, mean contour depth, and half depth volume. The cup to disc ratios in eyes with OHD and NTD were greater than in eyes with OHND; the volume below was greater in eyes with NTD than in eyes with OHND and OHD.

CONCLUSIONS

The steep slope in the nasal inferior section is the first indicator of glaucomatous nerve defects in many eyes. The half depth parameters, half depth area, and half depth volume may be useful for distinguishing ocular hypertension with and without glaucomatous disc changes.

Use of sequential Heidelberg retina tomograph images to identify changes at the optic disc in ocular hypertensive patients at risk of developing glaucoma

AIM

To determine if global and segmental changes in optic disc parameters of sequential Heidelberg retina tomograph (HRT) images develop in individual ocular hypertensive (OHT) patients without white on white visual field defects.

METHODS

Patients and normal controls were recruited from a prospective ocular hypertension treatment trial. The subject groups consisted of 21 OHT patients who had converted to early glaucoma on the basis of visual field criteria (24-2 program on the Humphrey perimeter), 164 OHT subjects with normal visual fields, and 21 normal controls. Sequential HRT images 16-21 months apart were obtained for each subject and segmental optic disc parameters were measured to determine if any change had occurred. From the analysis of sequential HRT images of the 21 normal eyes we established normal limits of interimage variation. Individual discs in each group showing changes above the 95% limit of normal variability were then sought.

RESULTS

Several segmental and global optic disc parameters were found to show significant change in the converter group before confirmed visual field change, confirming our previously published results. Individual optic disc analysis using the 95% limit of normal variability data demonstrated glaucomatous change in 13 out of 21 converter eyes. 47 of the 164 OHT eyes with normal visual fields showed change in global and segmental parameters in a "glaucomatous" direction above the level expected for normal variability. The parameters which changed most frequently in the OHT eyes were: global cup volume (6.7% of discs), inferonasal cup volume (11%), inferotemporal cup volume (8.5%), and superotemporal cup area (7.3%).

CONCLUSIONS

We have identified change in a subset of ocular hypertensive patients which could predate the development of glaucomatous visual field loss. The HRT could be of value in the sequential follow up of those suspected of having glaucoma by identifying eyes at risk of developing glaucoma. However, further refinement of the technique is required to eliminate some of the inherent variability of the analysis method described, and to increase the ability to detect at risk individuals.

Longitudinal changes in optic disc topography of adult patients after trabeculectomy

OBJECTIVE

To study longitudinal changes in optic disc topography after trabeculectomy in adult patients.

DESIGN

Prospective case series.

PARTICIPANTS

Twenty-five eyes of 25 patients undergoing trabeculectomy were enrolled.

INTERVENTION

Images of the optic disc were obtained preoperatively and approximately 2 weeks, 4 months, and 8 months after surgery by use of a confocal scanning laser ophthalmoscope (Heidelberg Retina Tomograph).

MAIN OUTCOME MEASURES

The topographic optic disc parameters (cup volume, cup area, rim volume, rim area, cup-disc area ratio, mean cup depth, maximum depth, cup shape, and height variation contour) were measured automatically for each image with the Heidelberg Retina Tomograph Software (version 1.11).

RESULTS

Approximately 2 weeks after surgery, the mean preoperative intraocular pressure (IOP) of 19.3 mmHg (SD, 6.4 mmHg) decreased to 6.0 mmHg (SD, 3.6 mmHg), cup volume and mean cup depth decreased, height variation contour increased, and the cup shape parameter became more negative. Approximately 4 months after surgery, mean IOP was 9.7 mmHg (SD, 4.2 mmHg), and the only statistically significant change from preoperative values of optic disc parameters was in the cup shape measure. Approximately 8 months after surgery, there was no statistically significant change in any of the optic disc parameters compared with preoperative values, although IOP was 10.4 mmHg (SD, 5.9 mmHg).

CONCLUSIONS

Changes in the optic disc that may be present 2 weeks after a trabeculectomy do not appear to persist 4 and 8 months later in eyes with advanced glaucomatous optic nerve damage, except for cup shape, which was different from preoperative values at 4 months but not at 8 months.

Detection of optic disc change with the Heidelberg retina tomograph before confirmed visual field change in ocular hypertensives converting to early glaucoma

AIM

To determine whether analysis of sequential optic disc images obtained with the Heidelberg retina tomograph (HRT) is able to demonstrate optic disc change before the development of reproducible field defects in a group of ocular hypertensive (OHT) patients converting to early glaucoma.

METHODS

Two groups were analysed: (1) 13 eyes of 13 OHT patients who subsequently developed reproducible field defects (converters); and (2) 13 eyes of 11 normal control subjects. Two sequential optic disc images were obtained using the HRT (median separation between images was 12 months for the converters and 13 months for the normals). The second image in the converter group was obtained before confirmed visual field loss. The optic disc variables were analysed both globally and segmentally using HRT software version 1.11. The Wilcoxon signed rank test was used to determine if there were any significant differences between the variables of the two image sets.

RESULTS

Significant optic disc change was demonstrated in the group of converters: (1) global variables: the cup area increased by 9.7%, the C/D area ratio increased by 10.5%, and the rim area decreased by 6.9%; (2) segmental variables: the superonasal cup area increased by 11.0%, the superonasal C/D area ratio increased 11.7%, and the inferonasal cup volume increased by 28.4%. The temporal rim volume decreased by 15.6%, the inferotemporal rim volume decreased by 23.6%, and the rim area in the superonasal and superotemporal segments decreased by 6.6% and 6.9% respectively.

CONCLUSION

Analysis of sequential optic disc images on the HRT allowed the detection of glaucomatous change before confirmed visual field change in a group of OHT patients converting to early glaucoma.

Preperimetric glaucoma diagnosis by confocal scanning laser tomography of the optic disc

AIM

To evaluate the ability of confocal scanning laser tomography of the optic nerve head to detect glaucomatous optic nerve damage in ocular hypertensive eyes without visual field defects.

METHODS

The study included 50 normal subjects, 61 glaucoma patients with glaucomatous changes in the optic disc and visual field, and 102 "preperimetric" patients with increased intraocular pressure, normal visual fields, and glaucomatous appearance of the optic disc as evaluated on colour stereo optic disc photographs. For all individuals, confocal scanning laser tomographs of the optic nerve head were taken using the Heidelberg retina tomograph (HRT; software 2.01).

RESULTS

Almost all investigated HRT variables varied significantly (p < 0.05) between the normal eyes and preperimetric glaucoma eyes with pronounced overlap between the two study groups. Corresponding to the overlap, sensitivity and specificity values were relatively low when HRT variables were taken to differentiate between normal and preperimetric glaucoma eyes. At a given specificity of 95% highest sensitivities were found for the variables "rim area in the superior disc sector" (24.8%), "nerve fibre layer thickness in the inferior disc sector" (26.5%), and "rim volume in the superior disc sector" (25.5%). A multivariate approach increased sensitivity to 42.2% at a given specificity of 95%. For the glaucoma group highest sensitivity values were reached by rim volume in the superior disc sector (73.8%) and rim area (72.1%); the multivariate approach reached 83.6%.

CONCLUSIONS

Owing to pronounced overlapping between the groups, confocal scanning laser tomography of the optic nerve head has relatively low diagnostic power to differentiate between normal eyes and preperimetric glaucoma eyes. One of the reasons may be the biological interindividual variability of quantitative optic disc variables.

Pattern electroretinogram and optic nerve topography in ocular hypertension

It is known that changes in pattern electroretinogram (PERG) and optic disk morphology may both precede the onset of visual field damage in glaucomatous disease. However, the relationship between PERG and optic disk morphometry in ocular hypertension (OHT) has not yet been evaluated in detail. This study of PERG amplitude in a group of OHT patients indicates its significant correlation with various optic disk morphometric parameters, in particular, those of optic disk sectors considered at risk for early glaucomatous damage. Analysis of individual data points to the possibility that, while functional abnormalities may often precede optic disk morphologic changes, in a much lower number of cases it seems to be the other way around.

Identification of early glaucoma cases with the scanning laser ophthalmoscope

PURPOSE

This study aimed to define the confocal laser scanning ophthalmoscope (Heidelberg Retina Tomograph [HRT]) parameters that best separate patients with early glaucoma from normal subjects.

STUDY DESIGN

A cross-sectional study.

PARTICIPANTS

A total of 80 normal subjects and 51 patients with early glaucoma participated (average visual field mean deviation = -3.6 dB).

INTERVENTION

Imaging of the optic nerve head with the HRT and analysis using software version 1.11 were performed.

MAIN OUTCOME MEASURES

The relation between neuroretinal rim area and optic disc area, and cup-disc area ratio and optic disc area, was defined by linear regression of data derived from the normal subjects. The normal ranges for these two parameters were defined by the 99% prediction intervals of the linear regression between the parameter and optic disc area, for the whole disc, and for each of the predefined segments. Normal subjects and patients were labeled as abnormal if the parameter for either the whole disc or any of the predefined segments was outside the normal range. The sensitivity and specificity values of the method were calculated.

RESULTS

The highest specificity (96.3%) and sensitivity (84.3%) values to separate normal subjects and those patients with early glaucoma were obtained using the 99% prediction interval from the linear regression between the optic disc area and the log of the neuroretinal rim area. Similar specificity (97.5%) and lower sensitivity (74.5%) values were obtained with the 99% prediction interval derived from regression between the disc area and cup-disc area ratios. Poor separation between groups was obtained with the other parameters.

CONCLUSIONS

The HRT, using the technique of linear regression to account for the relationship between optic disc size and rim area or cup-disc area ratio, provides good separation between control subjects and patients with early glaucoma in this population.