Topographic Change Analysis Research Articles

Analysis of Large-scale Topographic Changes of Akaehama Beach in Miyazaki Prefecture Based on Bathymetric Survey Data

Analysis of Large-scale Topographic Changes of Akaehama Beach in Miyazaki Prefecture Based on Bathymetric Survey Data

Clinical Evaluation of the Proper Orthogonal Decomposition Framework for Detecting Glaucomatous Changes in Human Subjects

To evaluate the new proper orthogonal decomposition (POD) framework for detecting glaucomatous progression from HRT topographies of human subjects and compare it with HRT topographic change analysis (TCA). Of 267 eyes of 187 participants with > or =4 retinal tomographic examinations in the University of California, San Diego Diagnostic Innovations in Glaucoma Study (DIGS), 21 eyes were of longitudinally normal subjects and 36 eyes progressed by stereophotographs or visual field-guided progression analysis (progressors). All others were considered nonprogressing (nonprogressors; n = 210 eyes). POD parameters of Euclidean distance (L(2) norm), image Euclidean distance, and correlation were computed, and their area under receiver operating characteristic curves (AUC) in differentiating progressors from nonprogressors and normal subjects were compared to the TCA parameters of the number of superpixels with significant decrease in retinal height (red pixels), size of the largest cluster of red pixels (CSIZE), and CSIZE% of disc size, all within the optic disc margin. AUCs of the best performing POD L(2) norm and TCA red pixel parameters in differentiating progressors from normal subjects were both 0.86 and in differentiating progressors from nonprogressors were 0.68 and 0.64, respectively; the AUC differences were not statistically significant. The POD framework, which can detect and confirm glaucomatous changes in a single follow-up visit, provides a performance similar to that of TCA in differentiating progressors from normal subjects and nonprogressors.

Glaukomdiagnostik und Verlaufskontrolle mit dem Heidelberg Retina Tomograph

The Heidelberg Retina Tomograph (HRT) is a glaucoma diagnosis system that provides fast, noninvasive topographic information about the optic nerve head, the neuroretinal rim, and the thickness of the nerve fiber layer. With these capabilities, it is one of the leading laser systems for detecting glaucoma. Statistical methods such as the Moorfields regression analysis and the glaucoma probability score, as well as discriminant functions implemented in the instrument, support the clinician in discriminating between glaucoma and healthy eyes. The primary method for assessing glaucomatous change using the HRT is topographic change analysis, a technique that compares the variability within a baseline examination to that between baseline and follow-up examinations. The stereometric trend analysis reports changes in normalized topographic parameters over time. Furthermore, the flicker comparison enables the detection of small topographic changes over time. The use of HRT does not replace clinical examination but facilitates the assessment and management of glaucoma according to the observer's experience.

Incidence and Rates of Visual Field Progression after Longitudinally Measured Optic Disc Change in Glaucoma

To determine whether glaucoma patients with progressive optic disc change have subsequent visual field progression earlier and at a faster rate compared with those without disc change. Prospective, longitudinal, cohort study. Eighty-one patients with open-angle glaucoma. Patients underwent confocal scanning laser tomography and standard automated perimetry every 6 months. The complete follow-up was divided into initial and subsequent periods. Two initial periods-first 3 years (Protocol A) and first half of the total follow-up (Protocol B)-were used, with the respective remainder being the subsequent follow-up. Disc change during the initial follow-up was determined with liberal, moderate, or conservative criteria of the Topographic Change Analysis. Subsequent field progression was determined with significant pattern deviation change in >or=3 locations (criterion used in the Early Manifest Glaucoma Trial). As a control analysis, field change during the initial follow-up was determined with significant pattern deviation change in >or=1, >or=2, or >or=3 locations. Survival time to subsequent field progression, rates of mean deviation (MD) change, and positive and negative likelihood ratios. The median (interquartile range) total follow-up was 11.0 (8.0-12.0) years with 22 (18-24) examinations. More patients had disc changes during the initial follow-up compared with field changes. The mean time to field progression was consistently shorter (protocol A, 0.8-1.7 years; protocol B, 0.3-0.7 years) in patients with prior disc change. In the control analysis, patients with prior field change had statistically earlier subsequent field progression (protocol A, 2.9-3.0 years; protocol B, 0.7-0.9). Similarly, patients with either prior disc or field change always had worse mean rates of subsequent MD change, although the distributions overlapped widely. Patients with subsequent field progression were up to 3 times more likely to have prior disc change compared with those without, and up to 5 times more likely to have prior field change compared with those without. Longitudinally measured optic disc change is predictive of subsequent visual field progression and may be an efficacious end point for functional outcomes in clinical studies and trials in glaucoma.

A framework for detecting glaucomatous progression in the optic nerve head of an eye using proper orthogonal decomposition.

Glaucoma is the second leading cause of blindness worldwide. Often, the optic nerve head (ONH) glaucomatous damage and ONH changes occur prior to visual field loss and are observable in vivo. Thus, digital image analysis is a promising choice for detecting the onset and/or progression of glaucoma. In this paper, we present a new framework for detecting glaucomatous changes in the ONH of an eye using the method of proper orthogonal decomposition (POD). A baseline topograph subspace was constructed for each eye to describe the structure of the ONH of the eye at a reference/baseline condition using POD. Any glaucomatous changes in the ONH of the eye present during a follow-up exam were estimated by comparing the follow-up ONH topography with its baseline topograph subspace representation. Image correspondence measures of L1-norm and L2 -norm, correlation, and image Euclidean distance (IMED) were used to quantify the ONH changes. An ONH topographic library built from the Louisiana State University Experimental Glaucoma study was used to evaluate the performance of the proposed method. The area under the receiver operating characteristic curves (AUCs) was used to compare the diagnostic performance of the POD-induced parameters with the parameters of the topographic change analysis (TCA) method. The IMED and L2-norm parameters in the POD framework provided the highest AUC of 0.94 at 10 degrees field of imaging and 0.91 at 15 degrees field of imaging compared to the TCA parameters with an AUC of 0.86 and 0.88, respectively. The proposed POD framework captures the instrument measurement variability and inherent structure variability and shows promise for improving our ability to detect glaucomatous change over time in glaucoma management.

Eyelid Pressure: Inferences From Corneal Topographic Changes

It is known that eyelid pressure can influence the corneal surface. However, the distribution of eyelid pressure and the eyelid contact area and the biomechanics of the changes are unknown. Although these factors are difficult to directly measure, analysis of eyelid-induced corneal topographic changes and eyelid morphometry enables some inferences to be drawn. Eighteen subjects, aged between 19 and 29 years, with normal ocular health were recruited. Corneal topographic changes were measured after 4 conditions consisting of 2 downward gaze angles (20 and 40 degrees) and 2 types of visual tasks (reading and steady fixation). Digital photography recorded the width of Marx line, the assumed region of primary eyelid contact with the cornea. Significantly larger corneal changes were found after the 40-degree downward gaze conditions compared with 20-degree conditions because of the upper eyelid contact (P < 0.001). For the 40-degree downward gaze tasks, the lower eyelid changes were greater than those because of the upper eyelid (P < 0.01). The upper eyelid Marx line width was associated with the amplitude of corneal change (R = 0.32, P < 0.05). Analysis of the corneal topographic changes gives insight into the pressure applied by the upper and lower eyelids in different situations. These include greater upper eyelid pressure with increasing downward gaze and greater lower eyelid pressure compared with the upper eyelid in 40-degree downward gaze. There was some evidence that supports Marx line as the primary site of contact between the eyelid margins and the cornea.

Optic Disc Progression in Glaucoma: Comparison of Confocal Scanning Laser Tomography to Optic Disc Photographs in a Prospective Study

To compare confocal scanning laser tomography (CSLT) to optic disc photography for detecting progressive glaucomatous disc changes. Four expert observers first examined a training set of 40 pairs of monoscopic disc photographs to help set a criterion for change. They then classified 44 pairs of monoscopic photographs of patients followed prospectively as having either definitely no change, probably no change, probably change, or definitely change (score, 0, 1, 2, or 3, respectively). Observers were unaware that 10 pairs were photographs of fellow eyes obtained the same day to measure specificity. These patients were imaged with the Heidelberg Retina Tomograph every 6 months. Topographic change analysis (TCA) software with three criteria (yielding specificity of 81%, 94%, or 97%) was used. Comparisons between the TCA results and those of observers were made for a range of liberal to conservative criteria and for individual and combined observer scores. The median follow-up was 9.0 years with 18 CSLT images. Observer specificity varied from 50% to 90% (using score 0) and 60% to 100% (using score 0 or 1). Interobserver kappa ranged from 0.22 to 0.38 from the most liberal to conservative criterion and was generally higher than corresponding TCA-observer agreement. For most criteria, observers had either a high hit rate with low specificity or high specificity with a low hit rate compared with the TCA. Similar results were obtained when observer scores were combined to derive a broader range of criteria. The results indicate that the TCA performs at least as well as either the individual or best combination of observer classifications of disc photographs.

Clinicians Agreement in Establishing Glaucomatous Progression Using the Heidelberg Retina Tomograph

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. Observational cohort study. 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). 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. 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. 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). 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. Proprietary or commercial disclosures may be found after the references.

Performance of confocal scanning laser tomograph Topographic Change Analysis (TCA) for assessing glaucomatous progression.

To determine the sensitivity and specificity of confocal scanning laser ophthalmoscope's Topographic Change Analysis (TCA; Heidelberg Retina Tomograph [HRT]; Heidelberg Engineering, Heidelberg, Germany) parameters for discriminating between progressing glaucomatous and stable healthy eyes. The 0.90, 0.95, and 0.99 specificity cutoffs for various (n=70) TCA parameters were developed by using 1000 permuted topographic series derived from HRT images of 18 healthy eyes from Moorfields Eye Hospital, imaged at least four times. The cutoffs were then applied to topographic series from 36 eyes with known glaucomatous progression (by optic disc stereophotograph assessment and/or standard automated perimetry guided progression analysis, [GPA]) and 21 healthy eyes from the University of California, San Diego (UCSD) Diagnostic Innovations in Glaucoma Study (DIGS), all imaged at least four times, to determine TCA sensitivity and specificity. Cutoffs also were applied to 210 DIGS patients' eyes imaged at least four times with no evidence of progression (nonprogressed) by stereophotography or GPA. The TCA parameter providing the best sensitivity/specificity tradeoff using the 0.90, 0.95, and 0.99 cutoffs was the largest clustered superpixel area within the optic disc margin (CAREA(disc) mm(2)). Sensitivities/specificities for classifying progressing (by stereophotography and/or GPA) and healthy eyes were 0.778/0.809, 0.639/0.857, and 0.611/1.00, respectively. In nonprogressing eyes, specificities were 0.464, 0.570, and 0.647 (i.e., lower than in the healthy eyes). In addition, TCA parameter measurements of nonprogressing eyes were similar to those of progressing eyes. TCA parameters can discriminate between progressing and longitudinally observed healthy eyes. Low specificity in apparently nonprogressing patients' eyes suggests early progression detection using TCA.

Large-scale moraine deformation at the Athabasca Glacier, Jasper National Park, Alberta, Canada

In this paper the development of a large-scale gravitational deformation involving the eastern lateral moraine of the Athabasca Glacier in Jasper National Park, Alberta, Canada, is described. Interpretation and analysis of sequential aerial photographs indicates that a 540-m-wide segment of the eastern lateral moraine began to deform in the early 1950s; however, significant movement only began in the late 1960s. Since then, the moraine has undergone progressive gravitational deformation leading to a network of fractures, bulging, and the development of a large gap in the moraine crest. Geographic information system analysis of topographic changes between 1967 and 2006 indicates that the displaced volume of the moraine is approximately 9.0×10 5 m 3 . In the last 39 years, the moraine crest has displaced 55 m (1.4 m yr -1 ) down towards the glacier. The development of slope instability is linked to a combination of debuttressing from recent glacier recession, deformation of the moraine, as well as the movement of a large, mobile, debris-mantled slope impinging the upslope margin of the lateral moraine. This case study illustrates the importance of glacial conditioning and local geomorphological factors in creating conditions for large-scale moraine instability in recently deglacierized alpine basins.

Comparison of glaucoma progression evaluated with Heidelberg retina tomograph II versus optic nerve head stereophotographs

Background: To compare disease progression in glaucoma evaluated by means of the Heidelberg retina tomograph (HRT II) or by expert clinical assessment of colour stereophotographs of the optic nerve head (ONH).Methods: One eye each of 54 subjects with glaucoma was reviewed using the HRT II and ONH stereophotographs. The ONH stereophotographs were assessed twice each for glaucomatous progression by 2 expert observers (Drs. Buys and Trope). They were considered to be in agreement if their results were the same in 3 of 4 assessments. Progression on the HRT II was defined by using the topographic change analysis (TCA). The clinical assessments were the reference standard used to determine sensitivity and specificity of the HRT II TCA.Results: The expert observers were in agreement in 50 subjects (92%). Concordance between the HRT II and ONH stereophotographs assessments was obtained in 35 patients (65%); 16 patients (30%) showed progression on HRT II only, while 3 patients (6%) showed progression on stereophotographs only. When these results were used to perform a post hoc analysis, HRT II sensitivity increased from 70% to 78% and specificity increased from 63.6% to 70%. The positive predictive value of the HRT II rose from 30.4% to 47.8%, while the negative predictive value remained at 90.3%.Interpretation: Our results demonstrate only fair agreement between HRT II and clinical judgment of ONH stereophotographs for progression in glaucomatous eyes. At present, HRT II progression alone should not indicate a treatment change. HRT II change must be evaluated in conjunction with other clinical features of deterioration before altering therapy.

Effect of Moderate Intraocular Pressure Changes on Topographic Measurements With Confocal Scanning Laser Tomography in Patients With Glaucoma

To evaluate optic disc topography changes after intraocular pressure (IOP) modulation in patients with glaucoma. Twenty-three patients with glaucoma were studied. Three mean optic disc topography images were obtained with the Heidelberg Retina Tomograph II at baseline and weeks 1, 2, 4, and 8 (visits 1, 2, 3, 4, and 5, respectively). Topical medications were discontinued in the study eye after visit 1 and resumed after visit 4 but maintained in the contralateral control eye. Central corneal thickness was measured at the last visit. Topographic changes were determined by stereometric parameters (rim area and mean cup depth) and at discrete topographic locations using the Topographic Change Analysis program (from the Heidelberg Retina Tomograph II). In the study eyes, IOP increased significantly (5.4 mm Hg at visit 4; P<.001) after withdrawal of topical medications but returned to baseline levels after resuming medications; no statistically significant topographic changes, however, were observed. Moreover, no relationship between change in IOP and stereometric parameters was observed. Central corneal thickness was not associated with changes in optic disc topography induced by IOP modulation. In patients with glaucoma, significant but relatively moderate IOP increases and decreases on the order of 5 mm Hg did not appear to have an effect on optic disc topography.

A New Statistical Approach for Quantifying Change in Series of Retinal and Optic Nerve Head Topography Images

To describe and evaluate new statistical techniques for detecting topographic changes in series of retinal and optic nerve head images acquired by scanning laser tomography (Heidelberg Retinal Tomograph [HRT]; Heidelberg Engineering, Heidelberg, Germany). Proven quantitative techniques, collectively referred to as statistic image mapping (SIM), are widely used in neuroimaging. These techniques are applied to HRT images. A pixel-by-pixel analysis of topographic height over time yields a statistic image that is generated by using permutation testing, derives significance limits for change wholly from the patient's own data, and removes the need for reference data sets. These novel techniques were compared to the Topographic Change Analysis (TCA super-pixel analysis) available in the current HRT software, by means of an extensive series of computer experiments. The SIM and TCA techniques were further tested and compared to linear regression of rim area (RA) against time, in real longitudinal HRT series of eyes of 20 normal subjects and 30 ocular hypertensive (OHT) patients that were known to have converted to glaucoma, on the basis of visual field criteria. Computer simulation indicated that SIM has better diagnostic precision at detecting change. In the real longitudinal series, SIM flagged false-positive structural progression in two (10%) of normal subjects, whereas TCA identified three (15%), and linear regression of RA against time identified two (10%). SIM identified 22 (73%) of the OHT converters as having structural progression, whereas the TCA and linear regression of RA against time each identified 16 (53%) over the course of the follow-up. SIM has better diagnostic precision in detecting change in series of HRT images when compared to current quantitative techniques. The clinical utility of these techniques will be established on further longitudinal data sets.

Effects of Ar-plasma treatment in alkali-decomposition of poly(ethylene terephthalate)

The ablation effects of Ar-plasma treatment and alkali-decomposition behavior in NaOH solution of polyethylene terephthalate (PET) film were investigated. The modifications were evaluated by analysis of atomic force microscopy topographical changes, and by the measurement of decomposition yield in conjunction with heats of formation and electron densities of acyl carbon calculated by Parameterization Method 3 method. It has shown that the alkali-decomposition is hampered by plasma treatment and its decomposition yield is closely related with plasma treatment conditions such as exposure time to plasma. Plasma-treated PET films exhibited lower decomposition yield, compared to that of virgin PET. Increasing plasma exposure time contributes positively to decrease the decomposition yield. It has also shown that the topography of PET surface was affected by the base-promoted hydrolysis as well as Ar-plasma treatments. These behaviors are attributed to the decreased nucleophilicity of acyl carbon damaged by the ablation of Ar-plasma.

Batch-by-batch analysis of topographic changes induced by sutured and sutureless clear corneal incisions

Purpose: To evaluate the effect of a suture on surgically induced corneal topographic changes in 5.0 mm clear corneal incisions.Setting: University Eye Hospital, Vienna, Austria.Methods: Thirty-seven eyes that had cataract surgery were included in the prospective study. A 5.0 mm long and 0.3 mm deep precut was followed by preparation of a corneal tunnel. After phacoemulsification and intraocular lens implantation, the self-sealing wound was left unsutured in 19 eyes; one radial 11-0 nylon suture was applied in 18 eyes. Using a TMS-1 videokeratoscope, corneal topography was measured preoperatively and at 1 week and 1 and 3 months postoperatively. The topographic data were evaluated by statistical batch-by-batch analysis. Each topographic image was cut into 178 fields in eight concentric rings. The refractive values of these fields were stored in a database. Differences between the four readings of each patient were calculated and the mean differences of the 178 fields in each group were transformed into color-coded maps. The significance of topographical changes and group comparisons of induced changes were computed by Wilcoxon tests.Results: Both groups exhibited significant temporal flattening and vertical steepening. The unsutured eyes also displayed significant nasal flattening. Sutureless 5.0 mm clear corneal incisions induced significantly more vertical steepening and nasal flattening than sutured incisions.Conclusion: Application of one radial 11-0 nylon suture in 5.0 mm temporal clear corneal incisions significantly reduced shape changes in the nasal corneal region.

Computerized Statistical Analysis of Corneal Topography for the Evaluation of Changes in Corneal Shape After Surgery

We examined 20 patients for the effect of a 3-mm sutureless temporal clear corneal incision cataract operation on corneal topography, as recorded with the computer-assisted video-keratoscope TMS-1 (Computed Anatomy, Inc., New York, New York). Each topographic image was cut into 178 fields in eight concentric rings. The refractive values of these fields were stored in a database. The mean differences between the preoperative and one-month postoperative findings were calculated and transformed into color-coded maps as output for the statistical analysis. The patients operated on showed a mean flattening of 0.4 to 1.0 diopter in the temporal region. This was statistically significant by paired Wilcoxon signed-rank tests. There was no significant vertical steepening or nasal flattening, except in two isolated fields. For control purposes, we twice examined 20 age-matched volunteers who were not operated on. The paired Wilcoxon tests of this group did not show significant changes. When compared with Cravy's vector analysis, induced topographic change analysis is better at evaluating surgically induced corneal shape changes.

Computerized videokeratographic analysis of corneal topographic changes induced by sutured and unsutured 4 mm scleral pocket incisions

We used computerized videokeratography to analyze corneal topographical changes in 39 eyes of 39 patients who had phacoemulsification and posterior chamber lens implantation through 4 mm incisions. In one group of patients, the incisions were closed with a single vertical mattress suture; in the other group, no sutures were used. Computerized videokeratography was performed preoperatively and at one and five to six weeks postoperatively; corneal curvatures were assessed at radial distances of 0.75, 1.5, 2.5, and 3.5 mm along the 0-, 90-,180-, and 270-degree semimeridians. At one week postoperatively, there was slightly more steepening along the 90- and 270-degree semimeridians (up to 0.9 diopters [D]) and slightly more flattening along the 0- and 180-degree semimeridians (up to 0.6 D) in the sutured group. At six weeks postoperatively, all mean semimeridional changes were less than 0.5 D. Computerized videokeratography demonstrated that sutured and unsutured 4 mm incisions induced clinically small corneal topographic changes and detected local variations in corneal curvature that may be due to sutures, cautery, and other operative factors.

Topographical corneal oedema.

Corneal thickness changes were monitored across the cornea in 10 subjects during 7 days continuous wear of 3 types of hydrogel contact lenses of different back vertex powers. Analysis of topographical corneal thickness changes indicates that the periphery of the cornea swells significantly less than the central cornea. The effect is more dramatic with higher levels of central corneal oedema, and with lenses of higher minus power, in spite of their thicker lens periphery. An anoxic stimulus was also found to produce greater central than peripheral corneal swelling, indicating that tear exchange under the periphery of the contact lens is not a significant factor in limiting peripheral corneal swelling. It was concluded that the topographical swelling profile is not contact lens-related, but reflects a reduced swelling capability of the peripheral cornea, due to physical restraint in the limbal region.

Alcohol, habituation and the patterning of aggressive responses in a cichlid fish

Territorial cichlids were presented for 30 min with a conspecific male intruder (contained in a clear glass tube). Eight hr prior, 2 groups were administered alcohol (0.15 or 0.30 percent in the aquaria water). A third group served as a control. Three responses were recorded to allow analysis of topographic changes in behavior as well as changes in absolute levels. During the habituation phase, the normal group showed a sequence of long displays, followed by shorter ones as the frequency of attacks increased. The occurrence of threat which gradually gives way to attack is characteristic of the agonistic behavior of this species. In contrast to the controls, the 0.15 percent group was hyperaggressive, while the 0.30 percent group was hypoaggressive. Furthermore, the patterning of responses were abnormal. The 0.15 percent group gave abbreviated threats and more attacks (interpreted as a tendency to attack without warning); whereas, the 0.30 percent group gave many long threat displays, but few attacks. A stimulus specificity test provided strong evidence that the waning found during the initial phase was habituation.