Spectral domain-optical coherence tomography to detect localized retinal nerve fiber layer defects in glaucomatous eyes

A Case for The Use of Artificial Intelligence in Glaucoma Assessment

We hypothesize that artificial intelligence applied to relevant clinical testing in glaucoma has the potential to enhance the ability to detect glaucoma. This premise was discussed at the recent Collaborative Community for Ophthalmic Imaging meeting, "The Future of Artificial Intelligence-Enabled Ophthalmic Image Interpretation: Accelerating Innovation and Implementation Pathways," held virtually September 3-4, 2020. The Collaborative Community in Ophthalmic Imaging (CCOI) is an independent self-governing consortium of stakeholders with broad international representation from academic institutions, government agencies, and the private sector whose mission is to act as a forum for the purpose of helping speed innovation in healthcare technology. It was one of the first two such organizations officially designated by the FDA in September 2019 in response to their announcement of the collaborative community program as a strategic priority for 2018-2020. Further information on the CCOI can be found online at their website (https://www.cc-oi.org/about). Artificial intelligence for glaucoma diagnosis would have high utility globally, as access to care is limited in many parts of the world and half of all people with glaucoma are unaware of their illness. The application of artificial intelligence technology to glaucoma diagnosis has the potential to broadly increase access to care worldwide, in essence flattening the Earth by providing expert level evaluation to individuals even in the most remote regions of the planet.

Agreement and differences between macular values in children using two types of spectral optical coherence tomography

OBJECTIVES

To determine the degree of agreement and differences between macular parameters according to sex, age, laterality, ethnicity and type of optical coherence tomography (OCT) in paediatric patients.

MATERIALS AND METHODS

Prospective, transversal, and comparative study. OCT Spectralis and OCT Cirrus were used to obtain the macular values of both eyes in 100 patients between 5 and 15 years without ocular pathology. Due to the similarity between the values of both eyes, in the final sample we only considered the right eyes (OD) (n = 100).

RESULTS

The average central macular thickness (CMT) was 244.2 μm with Cirrus and 261.7 μm with Spectralis. The degree of agreement for the GMC was moderate (Intraclass Correlation Coefficient: 0.66) and from low to very low in the other quadrants. The GMC values of both systems were significantly higher in men than in women (P < .05). The macular retinal nerve fibre layer (mRNC), ganglion cell layer (GCC), the inner plexiform layer (IPLC), and the inner nuclear layer (INFL) had significantly higher values in men than in women (P < .01). There were no statistically significant differences in the GMC by age and laterality, however it was significantly higher in ethnic European children than in ethnic Latin American children; Cirrus (P = .042) and Spectralis (P = .033).

CONCLUSIONS

Macular parameters obtained by OCT Spectralis and OCT Cirrus should not be interchangeable in pediatric patients.

Agreement and differences between macular values in children using two types of spectral optical coherence tomography

OBJECTIVE

To determine the degree of agreement and differences between macular parameters according to sex, age, laterality, ethnicity and type of optical coherence tomography (OCT) in paediatric patients.

MATERIALS AND METHODS

Prospective, transversal, and comparative study. OCT Spectralis and OCT Cirrus were used to obtain the macular values of both eyes in 100 patients between 5 and 15years without ocular pathology. Due to the similarity between the values of both eyes, in the final sample we only considered the right eyes (OD) (n=100).

RESULTS

The average central macular thickness (CMT) was 244.2μm with Cirrus and 261.7μm with Spectralis. The degree of agreement for the GMC was moderate (intraclass correlation coefficient: 0.66) and from low to very low in the other quadrants. The GMC values of both systems were significantly higher in men than in women (P<.05). The macular retinal nerve fibre layer (mRNC), ganglion cell layer (GCC), the inner plexiform layer (IPLC), and the inner nuclear layer (INFL) had significantly higher values in men than in women (P<.01). There were no statistically significant differences in the GMC by age and laterality, however it was significantly higher in ethnic European children than in ethnic Latin American children; Cirrus (P=.042) and Spectralis (P=.033).

CONCLUSIONS

Macular parameters obtained by OCT Spectralis and OCT Cirrus should not be interchangeable in pediatric patients.

Assessment of a Segmentation-Free Deep Learning Algorithm for Diagnosing Glaucoma From Optical Coherence Tomography Scans

Importance

Conventional segmentation of the retinal nerve fiber layer (RNFL) is prone to errors that may affect the accuracy of spectral-domain optical coherence tomography (SD-OCT) scans in detecting glaucomatous damage.

Objective

To develop a segmentation-free deep learning (DL) algorithm for assessment of glaucomatous damage using the entire circle B-scan image from SD-OCT.

Design, Setting, and Participants

This cross-sectional study at a single institution used data from SD-OCT images of eyes with glaucoma (perimetric and preperimetric) and normal eyes. The data set was randomly split at the patient level into a training (50%), validation (20%), and test data set (30%). Data were collected from March 2008 to April 2019, and analysis began April 2018.

Exposures

A convolutional neural network was trained to discriminate glaucomatous from normal eyes using the SD-OCT circle B-scan without segmentation lines.

Main Outcomes and Measures

The ability to discriminate glaucoma from healthy eyes was evaluated by comparing the area under the receiver operating characteristic curve and sensitivity at 80% or 95% specificity for the DL algorithm's predicted probability of glaucoma vs conventional RNFL thickness parameters given by SD-OCT software. The performance was also assessed in preperimetric glaucoma, as well as by visual field severity using Hodapp-Parrish-Anderson criteria.

Results

A total of 20 806 SD-OCT images from 1154 eyes of 635 individuals (612 [53%] with glaucoma and 542 normal eyes [47%]) were included. The mean (SD) age at SD-OCT scan was 70.8 (10.4) years in individuals with glaucoma and 55.8 (14.1) years in controls. There were 187 women (53.3%) in the glaucoma group and 165 (59.8%) in the control group. Of 612 eyes with glaucoma, 432 (70.4%) had perimetric and 180 (29.6%) had preperimetric glaucoma. The DL algorithm had a significantly higher area under the receiver operating characteristic curve than global RNFL thickness (0.96 vs 0.87; difference = 0.08 [95% CI, 0.04-0.12]) and each RNFL thickness sector for discriminating between glaucoma and controls (all P < .001). At 95% specificity, the DL algorithm (81%; 95% CI, 64%-97%) was more sensitive than global RNFL thickness (67%; 95% CI, 58%-76%). The areas under the receiver operating characteristic curve were also significantly greater for the DL algorithm compared with RNFL thickness at each stage of disease, especially preperimetric and mild perimetric glaucoma.

Conclusions and Relevance

A segmentation-free DL algorithm performed better than conventional RNFL thickness parameters for diagnosing glaucomatous damage on OCT scans, especially in early disease. Future studies should investigate how such an approach contributes to diagnostic decisions when combined with other relevant clinical information, such as risk factors and perimetry results.

Optical coherence tomography modeling incorporating scattering, absorption, and multiple reflections

A direct scattering optical coherence tomography forward model was developed to simulate A-scans for both idealized and real light sources on an arbitrary given sample structure. Previous models neglected absorption, scattering, and multiple reflections at interfacial layers, and so two extended models were developed to investigate the impact of these processes. The first model uses the Beer-Lambert law to incorporate both absorption and scattering optical processes, and the second model uses a recursive form to model multiple reflections. These models were tested on a structure representative of a multilayered skin sample. The results show that the absorption and scattering processes have significant impact on the height of the peaks in the simulated A-scans. Conversely, the incorporation of multiple reflections has very little impact on the height of these peaks. Neither of the above processes has any impact on the locations of the A-scan peaks, which are associated with the sample interfaces between layers.

Two-year analysis of changes in the optic nerve and retina following anti-VEGF treatments in diabetic macular edema patients

Purpose: To evaluate long-term structural and functional changes that happen to the optic nerve and retina following ranibizumab (Lucentis) injections in diabetic macular edema (DME) patients. Methods: Patients with clinically significant DME requiring anti-VEGF injections underwent pre-injection baseline, 6, 12, and 24 month follow-up tests. The tests performed were optical coherence tomography (OCT), best-corrected visual acuity (BCVA), and visual field (VF). Wide-field fluorescein angiogram (IVFA) was performed to monitor the progression of diabetic ischemia. Results: A total of 30 patients requiring anti-VEGF injections and 21 control patients not requiring anti-VEGF injections were enrolled in the study. From baseline, the average macular thickness significantly decreased (p<0.0002) over the 24-month time period. Mean perfused ratio significantly increased (p<0.0005) at 6, 12, and 24 months. Cup volume and vertical cup-to-disk ratio significantly increased (p<0.0014) over the study period. This was verified by masked independent grading of patient optic nerve stereo-photographs by glaucoma specialists. BCVA significantly (p<0.0006) improved over the study period. VFs showed a non-significant trend of deteriorating peripheral vision at 12 and 24 months. Conclusion: Clinically, anti-VEGF therapy appears to affect the optic nerve by increasing cup volume and increasing vertical cup/disk ratio over time. The results provide a cautionary note to monitor both the retina and optic nerve status in patients undergoing frequent injections.

Effect of panretinal photocoagulation on the peripapillary retinal nerve fiber layer in diabetic retinopathy patients

OBJECTIVES

To determine the effect of panretinal photocoagulation (PRP) on the peripapillary retinal nerve fiber layer (RNFL) in nonglaucomatous patients with proliferative diabetic retinopathy (PDR).

METHODS

This is a prospective, single center, observational study. Thirty-eight eyes of 26 diabetic patients underwent PRP for proliferative diabetic retinopathy. Peripapillary RNFL thickness was measured using scanning laser polarimetry (SLP) with variable corneal compensation (GDx VCC; by Carl Zeiss Meditec, Dublin, CA) and spectral-domain optical coherence tomography (OCT) (Heidelberg Spectralis, Carlsbad, USA) at baseline and 12 months after PRP was performed.

RESULTS

Thirty-eight eyes of 26 patients (15 female) with a mean age of 53.7 years (range 26 to 74 years) were recruited. No significant difference was found among all RNFL thickness parameters tested by GDx VCC software (p=0.952, 0.464 and 0.541 for temporal-superior-nasal-inferior-temporal (TSNIT) average, superior average, inferior average, respectively). The nerve fiber indicator (NFI) had a nonsignificant increase (p=0.354). The OCT results showed that the average RNFL thickness (360° measurement) decreased nonsignificantly from 97.2 mm to 96.0 mm at 1 year post-PRP (p=0.469). There was no significant difference when separately analyzing all the peripapillary sectors (nasal superior, temporal superior, temporal, temporal inferior, nasal inferior and nasal thickness).

CONCLUSION

Our results suggest that PRP, as performed in our study, does not cause significant changes in peripapillary RNFL in diabetic PDR patients after one year of follow-up.

Optical coherence tomography in Optics Express [Invited]

Optical coherence tomography (OCT) is one of the most successful technologies in the history of biomedical optics. Optics Express played an important role in communicating groundbreaking technological achievements in the field of OCT, and, conversely, OCT papers are among the most frequently cited papers published in Optics Express. On the occasion of the 20th anniversary of the journal, this review analyzes the reasons for the success of OCT papers in Optics Express and discusses possible motivations for researchers to submit some of their best OCT papers to the journal.

Comparing ganglion cell-inner plexiform layer thickness with focal and global responses on multifocal electroretinogram in glaucoma

BACKGROUND

The aim of this study was to evaluate responses on multifocal electroretinogram (mfERG) with ganglion cell-inner plexiform layer (GCIPL) thickness on cirrus spectral-domain optical coherence tomography (SD-OCT) in glaucoma.

METHODS

All diagnosed glaucoma patients attending glaucoma services at our institute from November 2012 to April 2013 were screened for this observational hospital-based study. Controls included patients attending our outpatient services for general eye checkup. Structural parameters on SD-OCT including GCIPL and retinal nerve fiber layer (RNFL) thickness were compared with functional parameters on mfERG in early (mean deviation <-6 dB), moderate (-6 to - 12 dB), and controls.

RESULTS

A total of 54 cases and 33 controls fulfilling inclusion criteria were recruited for the study. The average and minimum GCIPL thickness did not vary significantly between early and control eyes while moderate glaucoma eyes had marginally lower GCIPL thickness than early glaucoma eyes. The GCIPL minimum thickness on univariate regression was found to be influenced by N2 amplitudes (β = -0.5, P = 0.012) and global N2P1amplitudes (β =0.6, P = 0.01) in moderate glaucoma. In early glaucoma, these were influenced only by RNFL parameters with no association with functional mfERG responses. Multivariate logistic regression identified global N2P1 amplitude to be significantly influencing GCIPL average and minimum thickness (P = 0.01 and 0.02, R² = 47.8% and 52.3%, respectively) in moderate glaucoma. Maximum area under the curve was found for GCIPL minimum (95% confidence interval [CI] 0.53-0.81) and N2P1 amplitude (95% CI 0.55-0.80).

CONCLUSIONS

The second order responses N2P1 and N2 amplitude on mfERG predict function that correlated with structural GCIPL thickness in moderate glaucoma. Early glaucoma may be best predicted by RNFL thickness rather than on mfERG responses.

Correlations Between Retinal Nerve Fiber Layer Thickness and Axial Length, Peripapillary Retinal Tilt, Optic Disc Size, and Retinal Artery Position in Healthy Eyes

PURPOSE

To determine the correlations between the retinal nerve fiber layer thickness (RNFLT) and the axial length, peripapillary retinal tilt (PRT), and optic disc size, and retinal artery position.

METHODS

A prospective, observational cross-sectional study of 119 healthy right eyes of 119 volunteers. All participants underwent comprehensive ophthalmologic examinations including peripapillary RNFLT imaging and measurements of the axial length. The RNFLT was determined by the TOPCON 3D OCT-1000, MARK II. The RNFLT in a 3.4 mm circular scan was divided into 12 clock-hour sectors and 4 quadrant sectors around the optic disc. The PRT was assessed using the RNFLT B-scan images. The angle between the supra-temporal and infra-temporal retinal arteries was determined in the color fundus photographs. The correlations between the sectorial RNFLTs and the axial length, PRT, optic disc size, and artery angles were determined by simple and multiple regression analyses.

RESULTS

Multiple regression analyses showed that the nasal and inferior quadrants and the whole RNFLT were significantly and negatively correlated with the axial length (standardized coefficient (SC)=-0.39 to -0.30, P<0.05). The PRT was significantly and positively associated with all of the quadrants and the whole RNFLT (SC=0.22 to 0.45, P<0.05). The retinal artery angle was significantly and negatively associated with the temporal RNFLT and positively associated with inferior RNFLT (SC=-0.49 to 0.31, P<0.05). The optic disc size was significantly and positively associated with the superior and nasal quadrants, and the whole RNFLT (SC=0.20 to 0.27, P<0.05).

CONCLUSIONS

The axial length, PRT, optic disc size, retinal artery angle can affect the peripapillary RNFLT. These variables should be considered when assessing the peripapillary RNFLT.

Structural and functional changes to the retina and optic nerve following panretinal photocoagulation over a 2-year time period

PurposeTo evaluate long-term structural and functional changes to the retina and optic nerve following panretinal photocoagulation (PRP) in diabetic retinopathy (DR) patients.MethodsParticipants were patients with DR requiring PRP and control patients with DR not requiring PRP. The Heidelberg retinal tomography (HRT) and optical coherence tomography (OCT) were performed to analyze the optic nerve and macula. Best-corrected visual acuity (BCVA) and visual field (VF) testing were done to measure central and peripheral vision. Wide-field fluorescein angiogram was performed to monitor the progression of diabetic ischemia. The primary outcome measure was to determine the degree of retinal and optic nerve changes before and after PRP.ResultsThere was a non-significant thickening of the macula and retinal nerve fiber layer at 6 months post laser that recovered by 24 months. Mean perfused ratio was significantly increased (P=0.02) at 12 and 24 months post laser. Independently grading patient stereophotographs, grader 1 indicated there was a non-significant increase in cup to disk ratio post laser, while grader 2 indicated a significant increase at 6 (P=0.04), 12 (P=0.02), and 24 months (P=0.005). There was a significant VF decrease (P≤0.02) at 12 and 24 months post laser with BCVA showing a non-significant trend of deteriorating results.ConclusionDespite an improvement in peripheral perfusion, there was a significant progressive decline of peripheral VF over the study period. Clinical grading of the optic nerve was more unreliable following PRP, despite the absence of significant morphological changes as detected by the OCT and HRT.

Detection of preperimetric glaucoma using Bruch membrane opening, neural canal and posterior pole asymmetry analysis of optical coherence tomography

We analysed retinal nerve fibre layer (RNFL) defects in eyes with normal circumpapillary RNFL (cpRNFL) thickness using posterior pole asymmetry analysis (PPAA) and investigated the parameters of Bruch membrane opening (BMO) and neural canals using enhanced depth imaging spectral domain optical coherence tomography (EDI-SDOCT). A total of 112 preperimetric glaucomatous eyes of 92 patients were examined to obtain cpRNFL thickness using SD-OCT. Posterior pole asymmetry analysis (PPAA) and central cross-sectional images of the optic nerve head (ONH) were obtained using EDI-SDOCT. Minimal and horizontal distances between the BMO and ONH surfaces (BMOM, BMOH) and the terminal of retinal pigment epithelium (RPE) and ONH surfaces (RPEM, RPEH) were measured. The distribution of the absolute black cells in PPAA was more concentrated in eyes with “U”-shaped neural canals (p < 0.0001). The area under the receiver operating characteristic curve of the ratio of RPEM to RPEH (RPE-R, 0.771 ± 0.08) was significantly larger than the ratio of BMOM to BMOH (BMO-R, 0.719 ± 0.009) for PPAA results. A U-shaped neural canal, lower ratio of RPEM to RPEH, and lower ratio of BMOM to BMOH were considered early indicators of RNFL defects in preperimetric glaucomatous eyes with normal cpRNFL.

Estimating Lead Time Gained by Optical Coherence Tomography in Detecting Glaucoma before Development of Visual Field Defects

PURPOSE

To estimate the diagnostic accuracy and lead time gained by retinal nerve fiber layer (RNFL) thickness measurements from optical coherence tomography (OCT) for detecting glaucoma before the development of visual field defects.

DESIGN

Observational cohort study.

PARTICIPANTS

The study group included 75 eyes of 75 patients suspected of having glaucoma. These eyes had normal standard automated perimetry (SAP) at baseline and demonstrated repeatable (3 consecutive) abnormal tests during a median follow-up of 6.3 years. A control group of 75 eyes of 75 healthy subjects matched by age and number of OCT tests during follow-up was included.

METHODS

The RNFL thickness measurements were obtained at the time of development of the earliest SAP defect (time 0) and also at times -1, -2, -3, and so forth, corresponding to 1 year, 2 years, 3 years, and so forth, before the development of field loss. The OCT measurements at corresponding intervals were analyzed for controls. Time-dependent receiver operating characteristic (ROC) curves were used to evaluate diagnostic accuracy of OCT.

MAIN OUTCOME MEASURES

Areas and sensitivities of ROC curve at fixed specificities at different times before development of field loss.

RESULTS

At the date of conversion to the earliest visual field defect (time 0), mean ± standard deviation average RNFL thickness was 75.0±9.8 μm in glaucomatous eyes and 90.6±8.0 μm for controls (P < 0.001). Significant differences were seen up to 8 years before development of visual field defects (86.3±8.2 μm vs. 91.4±7.6 μm, respectively; P = 0.021). The ROC curve areas decreased with increasing times before detection of field defects. At times 0, -4, and -8 years, ROC curve areas were 0.87, 0.77, and 0.65, respectively. At 95% specificity, up to 35% of eyes had abnormal average RNFL thickness 4 years before development of visual field loss and 19% of eyes had abnormal results 8 years before field loss.

CONCLUSIONS

Assessment of RNFL thickness with OCT was able to detect glaucomatous damage before the appearance of visual field defects on SAP. In many subjects, significantly large lead times were seen when applying OCT as an ancillary diagnostic tool.

Influence of disc-fovea angle and retinal blood vessels on interindividual variability of circumpapillary retinal nerve fibre layer

BACKGROUND

To assess whether intersubject variability of circumpapillary retinal nerve fibre layer (RNFL) thickness in healthy subjects acquired with spectral domain optical coherence tomography (SD-OCT) can be reduced by considering the disc-fovea angle (DFA), either alone or together with a compensation based on retinal blood vessel distribution (RVD).

METHODS

106 healthy volunteers underwent SD-OCT examination centred on the optic disc (OD) and on the macula. OD contours and foveal positions were automatically calculated. RVD at 3.4 mm diameter circle was manually assessed. We made two approaches to reduce interindividual variability in RNFL values using compensation processes; RVD compensation: RNFL thickness values were compensated according to RVD variation (RNFLRVD) and DFA compensation: we shifted the RNFL thickness measurements according to the DFA (RNFLDFA). Coefficient of variance (CoV) was calculated in 12 clock hour sectors for original RNFL (RNFLo), RNFLDFA, RNFLRVD and RNFL with both compensation methods (RNFLDFA-RVD).

RESULTS

Compared with the mean CoV of RNFLO, mean CoV of RNFLDFA, RNFLRVD and RNFLDFA-RVD was changed by -0.71% (p>0.05), -9.51% (p<0.001) and -7.55% (p=0.001), respectively. When compared with RNFLDFA, RNFL DFA-RVD significantly reduced the mean CoV by -6.69% (p=0.001), while compared with RNFLRVD, RNFL DFA-RVD did not significantly increase the mean CoV (+2.20%), (p>0.05).

CONCLUSIONS

Although reaching an improvement in some sectors, rotation of RNFL measurements according to the DFA on average does not reduce intersubject variability of RNFL. However, adjusting for RVD reduced the variance significantly. The results reinforce our work in assessing RVD as an important anatomical factor responsible for intersubject variability in RNFL measurements.

Circumpapillary course of retinal pigment epithelium can be fit to sine wave and amplitude of sine wave is significantly correlated with ovality ratio of optic disc

The purpose of this study was to develop a method of quantifying the degree of optic disc tilt in normal eyes. This was a prospective, observational cross sectional study of 126 right eyes of 126 healthy volunteers. The optic disc tilt was determined from the circular peripapillary optical coherence tomographic (OCT) scan images. The course of the retinal pigment epithelium (RPE) layer in the peripapillary cross sectional scan images was fit to a sine wave curve, and the amplitude of the sine curve was used to reflect the degree of the optic disc tilt in the optical axis. The repeatability of the amplitude determinations was calculated. The correlation between the amplitude and the ovality ratio of the optic disc was determined. The correlation between the amplitude and the body height was also calculated. The mean amplitudewas 36.6 ± 17.5 pixels, which was significantly and inversely correlated with the ovality ratio of the optic disc (R = -0.59, P<0.001). The intra-rater and inter-rater correlation coefficients of the amplitude were significant high (P<0.001, both). The amplitude was significantly and inversely correlated with the body height (R = -0.38, P<0.001), but not with the axial length. In conclusion, a sine wave function can be used to describe the course of the RPE in the circumpapillary OCT images. The results indicate that the amplitude of the sine wave can be used to represent the degree of optic disc tilt. Thus, the sine wave analyses can be used as a quantifiable and repeatable method to determine the optic disc tilt.

Relationship between supernormal sectors of retinal nerve fibre layer and axial length in normal eyes

PURPOSE

To determine the effect of the axial length on the supernormal and false-positive sectors of the peripapillary retinal nerve fibre layer (RNFL) in healthy eyes using the normative database embedded in a spectral domain optical coherence tomographic (SD-OCT) instrument.

METHODS

This was a prospective, observational cross -sectional study. The right eyes of 126 healthy young volunteers were studied. The RNFL thickness was measured by SD-OCT in twelve 30-degree sectors (clock hours) around the optic disc. The sectors whose RNFL thickness was <5% probability level were labelled as false-positive sectors. The sectors >95% probability level were labelled as supernormal sectors. The relationships between the axial length and rates of supernormal and false-positive sectors were investigated.

RESULTS

A longer axial length was significantly associated with an increase in the rates of supernormal thickness in sector 8 (odds ratio, [OR], 1.494; p = 0.010) and sector 10 (OR, 1.529; p = 0.008). The supernormal sectors were mainly located in the temporal region. A longer axial length was significantly associated with a higher rates of false positives in sector 5 (OR, 1.789; p = 0.017), sector 6 (OR, 2.305; p < 0.001) and sector 12 (OR, 2.277; p = 0.035).

CONCLUSIONS

The axial length was significantly related to the rates of supernormal and false-positive sectors even in healthy eyes. These findings indicate that the specificity and sensitivity of SD-OCT will be affected especially in eyes with longer axial lengths.

Frequency of abnormal retinal nerve fibre layer and ganglion cell layer SDOCT scans in healthy eyes and glaucoma suspects in a prospective longitudinal study

BACKGROUND/AIMS

To examine the frequency of abnormal retinal nerve fibre layer thickness (RNFLT) and ganglion cell complex (GCC) measurements among healthy and glaucoma suspect and preperimetric glaucoma (GSPPG) eyes in a prospective longitudinal study.

METHODS

Normal and GSPPG eyes with ≥ 18 months follow-up were included. Spectral-domain optical coherence tomography (SDOCT) was performed annually in normal and biannually in GSPPG eyes. One eye was randomly selected for inclusion. RNFLT and GCC parameters with p>5% were classified as 'within normal limits (WNL)' and p<1% were classified as 'outside normal limits (ONL)'. RESUlts: 23 normal and 74 GSPPG eyes were followed for a mean 43.4 ± 9.6 months. During serial follow-up, 100% and 91% of normal eyes had all RNFLT and GCC parameters classified as WNL, respectively. 27 (37%) and 17 (23%) of GSPPG eyes had an ONL classification in at least one RNFLT and GCC parameter, respectively. A high percentage (41%-56%) of RNFLT and GCC measurements classified as ONL were not replicated on subsequent scans. The rates of loss for all parameters were similar (p>0.05) between the groups.

CONCLUSIONS

Specificity in this sample of healthy eyes was very high for RNFLT and GCC parameters. Confirmation of suspected SDOCT abnormalities is recommended to differentiate reproducible loss from long-term variability.

A joint estimation detection of Glaucoma progression in 3D spectral domain optical coherence tomography optic nerve head images

Glaucoma is an ocular disease characterized by distinctive changes in the optic nerve head (ONH) and visual field. Glaucoma can strike without symptoms and causes blindness if it remains without treatment. Therefore, early disease detection is important so that treatment can be initiated and blindness prevented. In this context, important advances in technology for non-invasive imaging of the eye have been made providing quantitative tools to measure structural changes in ONH topography, an essential element for glaucoma detection and monitoring. 3D spectral domain optical coherence tomography (SD-OCT), an optical imaging technique, has been commonly used to discriminate glaucomatous from healthy subjects. In this paper, we present a new framework for detection of glaucoma progression using 3D SD-OCT images. In contrast to previous works that the retinal nerve fiber layer (RNFL) thickness measurement provided by commercially available spectral-domain optical coherence tomograph, we consider the whole 3D volume for change detection. To integrate a priori knowledge and in particular the spatial voxel dependency in the change detection map, we propose the use of the Markov Random Field to handle a such dependency. To accommodate the presence of false positive detection, the estimated change detection map is then used to classify a 3D SDOCT image into the "non-progressing" and "progressing" glaucoma classes, based on a fuzzy logic classifier. We compared the diagnostic performance of the proposed framework to existing methods of progression detection.

Reliability and validity of Cirrus and Spectralis optical coherence tomography for detecting retinal atrophy in Alzheimer's disease

BACKGROUND

To evaluate and compare the ability of two Fourier-domain optical coherence tomography (OCT) devices to detect retinal and retinal nerve fibre layer (RNFL) atrophy in patients with Alzheimer's disease (AD) compared with healthy subjects; to test the intra-session reliability of two OCT devices in AD patients and healthy subjects.

METHODS

AD patients (n=75) and age-matched healthy subjects (n=75) underwent three Macular Cube 200 × 200 protocols using the Cirrus and Spectralis OCT devices and three 360° circular scans centred on the optic disc using the Cirrus OCT device, the classic glaucoma application, and the new Nsite Axonal Analytics application of the Spectralis OCT instrument. Differences between healthy and AD eyes were compared, and measurements provided by each OCT protocol were compared. Reliability was measured using intraclass correlation coefficients and coefficients of variation. Correlations between OCT measurements and disease duration and severity were also analysed.

RESULTS

Retinal thinning was observed in AD eyes in all areas except the fovea using both OCT devices. RNFL atrophy was detected in AD eyes with all three protocols, but the Nsite Axonal application was the most sensitive. Measurements by the two OCT devices were correlated, but differed significantly. Reliability was good using all protocols, but better with the glaucoma application of Spectralis. Mean RNFL thickness provided by the Nsite Axonal application correlated with disease duration.

CONCLUSIONS

Fourier-domain OCT is a valid and reliable technique for detecting subclinical RNFL and retinal atrophy in AD, especially using the Nsite Axonal application. RNFL thickness decreased with disease duration.

Likelihood ratios for glaucoma diagnosis using spectral-domain optical coherence tomography

PURPOSE

To present a methodology for calculating likelihood ratios for glaucoma diagnosis for continuous retinal nerve fiber layer (RNFL) thickness measurements from spectral-domain optical coherence tomography (spectral-domain OCT).

DESIGN

Observational cohort study.

METHODS

A total of 262 eyes of 187 patients with glaucoma and 190 eyes of 100 control subjects were included in the study. Subjects were recruited from the Diagnostic Innovations Glaucoma Study. Eyes with preperimetric and perimetric glaucomatous damage were included in the glaucoma group. The control group was composed of healthy eyes with normal visual fields from subjects recruited from the general population. All eyes underwent RNFL imaging with Spectralis spectral-domain OCT. Likelihood ratios for glaucoma diagnosis were estimated for specific global RNFL thickness measurements using a methodology based on estimating the tangents to the receiver operating characteristic (ROC) curve.

RESULTS

Likelihood ratios could be determined for continuous values of average RNFL thickness. Average RNFL thickness values lower than 86 μm were associated with positive likelihood ratios (ie, likelihood ratios greater than 1), whereas RNFL thickness values higher than 86 μm were associated with negative likelihood ratios (ie, likelihood ratios smaller than 1). A modified Fagan nomogram was provided to assist calculation of posttest probability of disease from the calculated likelihood ratios and pretest probability of disease.

CONCLUSION

The methodology allowed calculation of likelihood ratios for specific RNFL thickness values. By avoiding arbitrary categorization of test results, it potentially allows for an improved integration of test results into diagnostic clinical decision making.

Imaging of the optic nerve and retinal nerve fiber layer: an essential part of glaucoma diagnosis and monitoring

Because glaucomatous damage is irreversible early detection of structural changes in the optic nerve head and retinal nerve fiber layer is imperative for timely diagnosis of glaucoma and monitoring of its progression. Significant improvements in ocular imaging have been made in recent years. Imaging techniques such as optical coherence tomography, scanning laser polarimetry and confocal scanning laser ophthalmoscopy rely on different properties of light to provide objective structural assessment of the optic nerve head, retinal nerve fiber layer and macula. In this review, we discuss the capabilities of these imaging modalities pertinent for diagnosis of glaucoma and detection of progressive glaucomatous damage and provide a review of the current knowledge on the clinical performance of these technologies.

Evaluation of zebrafish brain development using optical coherence tomography

The zebrafish is a well-established model system used to study and understand various human biological processes. The present study used OCT to investigate growth of the adult zebrafish brain. Twenty zebrafish were studied, using their standard lengths as indicators of their age. Zebrafish brain aging was evaluated by analyzing signal attenuation rates and texture features in regions of interest (ROIs). Optical scattering originates from light interaction with biological structures. During development, the zebrafish brain gains cells. Signal attenuation rate, therefore, increases with increasing zebrafish brain age. This study's analyses of texture features could not identify aging in zebrafish brain. These results, therefore, indicated that the OCT signal attenuation rate can indicate zebrafish brain aging, and its analysis provides a more effective means of observing zebrafish brain aging than texture features analysis. Using OCT system could further increase the technique's potential for recognition and monitoring of zebrafish brain development.

The comparison of manual vs automated disc margin delineation using spectral-domain optical coherence tomography

AIMS

To examine the impact of manual vs automated disc margin delineation on optic nerve head (ONH) and retinal nerve fiber layer (RNFL) parameters using spectral-domain optical coherence tomography (SDOCT).

METHODS

A prospective cohort study consisting of normal, glaucoma suspect (GS) and glaucoma patients who underwent ONH and RNFL measurements using SDOCT technology (RTVue; Optovue Inc.). The retinal pigment epithelium/Bruch's membrane (RPE/BM) complex end points were automatically determined first, and were manually redefined subsequently. Analysis of variance, coefficient of variation (COV), concordance correlation coefficient (CCC), and Bland-Altman plots were used for the analyses.

RESULTS

Ninety-nine eyes of 50 subjects (age 68±10 years) consisting of 36 glaucoma, 56 GS, and 7 normal eyes were included. The RNFL thickness measurements were similar (P>0.05) between the two methods of demarcation, except for the inferior-nasal sector (P=0.04). For the ONH measurements, the cup-to-disc (C/D) ratio and rim area showed significant differences between the two methods (P<0.001). COV/CCC values for the ONH parameters were as follows: cup area 17.6%/0.88; cup volume 7.4%/0.91; average C/D ratio 18.1%/0.78; rim area 25.3%/0.69; and rim volume 42.6%/0.71, respectively. CCC/COV values for the RNFL parameters were as follows: average 2.1%/0.98; inferior-temporal quadrant 8.1%/0.79; inferior-nasal quadrant INQ quadrant 12.6%/0.67; SNQ quadrant 7.8%/0.83; and STQ quadrant 7.8%/0.88, respectively.

CONCLUSION

An overall high agreement and moderate-substantial concordance was observed between the demarcation methods. Automated disc margin delineation of SDOCT can be used reliably in clinical practice.

Retinal nerve fiber layer measurements by scanning laser polarimetry with enhanced corneal compensation in healthy subjects

PURPOSE

To evaluate the (i) effects of biological (age and axial length) and instrument-related [typical scan score (TSS) and corneal birefringence] parameters on the retinal nerve fiber layer (RNFL) measurements and (ii) repeatability of RNFL measurements with the enhanced corneal compensation (ECC) protocol of scanning laser polarimetry (SLP) in healthy subjects.

METHODS

In a cross-sectional study, 140 eyes of 73 healthy subjects underwent RNFL imaging with the ECC protocol of SLP. Linear mixed modeling methods were used to evaluate the effects of age, axial length, TSS, and corneal birefringence on RNFL measurements. One randomly selected eye of 48 subjects from the cohort underwent 3 serial scans during the same session to determine the repeatability.

RESULTS

Age significantly influenced all RNFL measurements. RNFL measurements decreased by 1 µm for every decade increase in age. TSS affected the overall average RNFL measurement (β=-0.62, P=0.003), whereas residual anterior segment retardance affected the superior quadrant measurement (β=1.14, P=0.01). Axial length and corneal birefringence measurements did not influence RNFL measurements. Repeatability, as assessed by the coefficient of variation, ranged between 1.7% for the overall average RNFL measurement and 11.4% for th nerve fiber indicator.

CONCLUSIONS

Age significantly affected all RNFL measurements with the ECC protocol of SLP, whereas TSS and residual anterior segment retardance affected the overall average and the superior average RNFL measurements, respectively. Axial length and corneal birefringence measurements did not influence any RNFL measurements. RNFL measurements had good intrasession repeatability. These results are important while evaluating the change in structural measurements over time in glaucoma patients.

Glaucoma Diagnosis and Monitoring Using Advanced Imaging Technologies

Advanced ocular imaging technologies facilitate objective and reproducible quantification of change in glaucoma but at the same time, impose new challenges on scientists and clinicians for separating true structural change from imaging noise. This review examines time-domain and spectral-domain optical coherence tomography, confocal scanning laser ophthalmoscopy and scanning laser polarimetry technologies and discusses the diagnostic accuracy and the ability of each technique for evaluation of glaucomatous progression. A broad review of the current literature reveals that objective assessment of retinal nerve fiber layer, ganglion cell complex and optic nerve head topography may improve glaucoma monitoring when used as a complementary tool in conjunction with the clinical judgment of an expert.

Optical coherence tomography: future trends for imaging in glaucoma

Optical coherence tomography captures a major role in clinical assessment in eye care. Innovative hardware and software improvements in the technology would further enhance its usefulness. In this review, we present several promising initiatives currently in development or early phase of assessment that we expect to have a future impact on optical coherence tomography.

Agreement between spectral domain optical coherence tomography and retinal nerve fiber layer photography in chinese

PURPOSE

To compare spectral domain optical coherence tomography (OCT) and fundus photography to identify localized retinal nerve fiber layer defects (RNFLD) in Chinese patients with early-to-medium advanced glaucoma.

METHODS

Thirty-nine patients (48 eyes) with localized RNFLDs by fundus photography and 48 age-matched control individuals were included into the study. The individuals underwent spectral domain OCT of the retinal nerve layer. In OCT, a localized RNFLD was defined as a dipping of the retinal nerve fiber layer thickness curve into the red-colored band of the graph, measured at a peripapillary circle with a diameter of 3.46 mm.

RESULTS

In the 48 eyes of the study group, 63 localized RNFLDs were seen on the fundus photographs. On the OCTs, 58 of these 63 localized RNFLDs were detected, whereas 5 defects were not detected. Two localized RNFLDs seen on the OCTs were not found on the corresponding fundus photographs. The resulting sensitivity and specificity of OCT for detecting localized RNFLDs were 92% and 96%, respectively. The overall agreement rate between both methods was 94% (90/96), and the κ value was 0.90 (P<0.001). The results of both techniques correlated with each other for the determination of the location (Pearson correlation coefficient (r)=0.99; P<0.001) and the width of the localized RNFLDs (201 ± 123 degrees vs. 207 ± 115 degrees; r=0.93; P<0.001).

CONCLUSIONS

Spectral domain OCT as compared with examiner-performed assessment of conventional fundus photographs is capable of detecting and measuring localized retinal nerve fiber layer defects with a relatively high diagnostic precision.

Clinical use of OCT in assessing glaucoma progression

Detection of disease progression is an important and challenging component of glaucoma management. Optical coherence tomography (OCT) has proved to be valuable in the detection of glaucomatous damage. With its high resolution and proven measurement reproducibility, OCT has the potential to become an important tool for glaucoma progression detection. This manuscript presents the capabilities of the OCT technology pertinent for detection of progressive glaucomatous damage and provides a review of the current knowledge on the device's clinical performance.

Optical coherence tomography measurements of retinal nerve fiber layer thickness in chinese children and teenagers

PURPOSE

To establish a reference range of retinal nerve fiber layer (RNFL) thickness by optical coherence tomography (OCT) in Chinese children and teenagers, and to investigate its relationship with sex, age, eye side, and refractive error.

METHODS

A total of 398 eyes from 199 normal Chinese aged 5 to 18 years (a mean of 10.4 ± 2.7 y), who were undergoing physical examination in the Department of Ophthalmology, were recruited for this study. Their RNFL thicknesses were measured by OCT [OCT, Stratus OCT (OCT3); Carl Zeiss Meditec, Dublin, Calif], and 7 parameters associated with the RNFL thickness were analyzed by the RNFL thickness average analysis program. The influences of several factors (such as sex, age, eye side, and refractive error) on RNFL thickness were also analyzed.

RESULTS

We found that the global average RNFL thickness (±SD) was 112.36 ± 9.21 μm in the present cohort. The thickest RNFL was located at the superior (148.73 ± 17.06 μm) and inferior (142.08 ± 16.03 μm) quadrants of the retina, followed by the temporal (83.82 ± 13.53 μm) quadrant and the nasal (74.84 ± 15.03 μm) quadrant. There was no significant difference in the measurements between boys and girls, however, the eye side had significant influence on RNFL thickness (P<0.01). We also found that the average RNFL thickness was positively correlated with the age and refractive error (P<0.01).

CONCLUSIONS

This study has established a standard reference of RNFL thickness measurements in Chinese aged 5 to 18 years by OCT, which may help to identify the changes of RNFL thickness in children and teenagers in Chinese and other parts of East Asia countries.

Optical tecnology developments in biomedicine: history, current and future

Biomedical optics is a rapidly emerging field for medical imaging and diagnostics. This paper reviews several biomedical optical technologies that have been developed and translated for either clinical or pre-clinical applications. Specifically, we focus on the following technologies: 1) near-infrared spectroscopy and tomography, 2) optical coherence tomography, 3) fluorescence spectroscopy and imaging, and 4) optical molecular imaging. There representative biomedical applications are also discussed here.

Ganglion cell complex and retinal nerve fiber layer measured by fourier-domain optical coherence tomography for early detection of structural damage in patients with preperimetric glaucoma

AIMS

To evaluate the capability of Fourier-domain optical coherence tomography (FD-OCT) to detect structural damage in patients with preperimetric glaucoma.

METHODS

A total of 178 Caucasian subjects were enrolled in this cohort study: 116 preperimetric glaucoma patients and 52 healthy subjects. Using three-dimensional FD-OCT, the participants underwent imaging of the ganglion cell complex (GCC) and the optic nerve head. Sensitivity, specificity, likelihood ratios, and predictive values were calculated for all parameters at the first and fifth percentiles. Areas under the curves (AUCs) were generated for all parameters and were compared (Delong test). For both the GCC and the optic nerve head protocols, the OR logical disjunction (Boolean logic operator) was calculated.

RESULTS

The AUCs didn't significantly differ. Macular global loss volume had the largest AUC (0.81). Specificities were high at both the fifth and first percentiles (up to 97%), but sensitivities were low, especially at the first percentile (55%-27%).

CONCLUSION

Macular and papillary diagnostic accuracies did not differ significantly based on the 95% confidence interval. The computation of the Boolean OR operator has been found to boost diagnostic accuracy. Using the software-provided classification, sensitivity and diagnostic accuracy were low for both the retinal nerve fiber layer and the GCC scans. FD-OCT does not seem to be decisive for early detection of structural damage in patients with no functional impairment. This suggests that there is a need for analysis software to be further refined to enhance glaucoma diagnostic capability.

Correlation between scanning laser polarimetry with and without enhanced corneal compensation and high-definition optical coherence tomography in normal and glaucomatous eyes

PURPOSE

To assess the relationship between high-definition optical coherence tomography (HD-OCT) and scanning laser polarimetry (SLP) with variable (VCC) and enhanced (ECC) corneal compensation in measuring peripapillary retinal nerve fibre layer (RNFL) thickness in healthy eyes and those with early-to-moderate glaucomatous VF loss.

METHODS

Healthy volunteers and patients with glaucoma who met the eligibility criteria were enrolled in this prospective, cross-sectional, and observational study. Subjects underwent complete ophthalmologic examination, automated perimetry, SLP-ECC, SLP-VCC and HD-OCT. SLP parameters were recalculated in 90 degrees segments (quadrants) in the calculation circle to be compared. Pearson correlation coefficients and Lin's concordance correlation coefficients were calculated. The p-values < 0.05 were considered statistically significant.

RESULTS

Fifty-five normal volunteers (mean age 59.1 years) and 33 patients with glaucoma (mean age 63.8 years) were enrolled. In the glaucoma group, 18 patients (54.5%) had MD ≥ -6.0 dB (early glaucoma) and 15 patients (45.4%) had MD between -6.01 and -12.0 dB (moderate glaucoma). The best correlation between HD-OCT and SLP was found in the superior quadrant thickness, r = 0.74 (0.62-0.82) (p < 0.0001) with SLP-VCC and in the average thickness, r = 0.80 (0.71-0.86) (p < 0.0001) and the superior quadrant thickness r = 0.80 (0.71-0.87) (p < 0.0001) with SLP-ECC. Concordance correlation coefficients obtained for every parameter in our study between HD-OCT and SLP-VCC and between HD-OCT and SLP-ECC were poor.

CONCLUSIONS

Our results suggest that HD-OCT parameters of RNFL thickness are significantly higher than SLP-VCC and SLP-ECC parameters, and therefore those thickness values are not interchangeable. The HD-OCT and SLP methods are well correlated but concordance is poor. The difference plots show a lack of agreement that changes as a proportion of the mean.

Inter-device agreement of retinal nerve fiber layer thickness measurements using spectral domain cirrus HD OCT

PURPOSE

To assess the inter-device agreement of peripapillary retinal nerve fiber layer (RNFL) thickness measurements by 2 spectral domain Cirrus HD optical coherence tomography (OCT) devices in healthy Korean subjects.

METHODS

Eleven eyes of 11 healthy volunteers were enrolled in the present study. Each eye was scanned with the Optic Disc Cube 200 × 200 scan of 2 Cirrus HD OCT devices for peripapillary RNFL thickness calculation. The inter-device agreements of the 2 Cirrus HD OCTs for average, quadrant, and clock-hour RNFL thickness values were determined with Wilcoxon signed rank test, Friedman test, Cronbach's alpha (α), intraclass correlation coefficient (ICC), coefficient of variation (COV), and Bland-Altman plot.

RESULTS

The mean age of the participants was 25.82 ± 3.28 years and all had a 0.00 logarithm of the minimum angle of resolution of best-corrected visual acuity. The signal strengths of scans from the 2 Cirrus HD OCT were not significantly different (p = 0.317). The inter-device agreement of average RNFL thickness was excellent (α, 0.940; ICC, 0.945; COV, 2.45 ± 1.52%). However, the agreement of nasal quadrant RNFL thickness was not very good (α, 0.715; ICC, 0.716; COV, 5.72 ± 4.64%). Additionally, on the Bland-Atman plot, the extent of agreement of the 2 Cirrus HD OCTs for RNFL thickness was variable according to scanned sectors.

CONCLUSIONS

The inter-device agreement of 2 spectral domain Cirrus HD OCT devices for peripapillary RNFL thickness measurements was generally excellent but variable according to the scanned area. Thus, physicians should consider this fact before judging a change of RNFL thicknesses if they were measured by different OCT devices.

Outer retinal abnormalities associated with inner retinal pathology in nonglaucomatous and glaucomatous optic neuropathies

Inner and outer retinal morphology were quantified in vivo for 6 nonglaucomatous and 10 glaucomatous optic neuropathy patients. Custom, ultrahigh-resolution imaging modalities were used to evaluate segmented retinal layer thickness in 3D volumes (Fourier-domain optical coherence tomography), cone photoreceptor density (adaptive optics fundus camera), and the length of inner and outer segments of cone photoreceptors (adaptive optics-optical coherence tomography). Quantitative comparisons were made with age-matched controls, or by comparing affected and nonaffected retinal areas defined by changes in visual fields. The integrity of outer retinal layers on optical coherence tomography B-scans and density of cone photoreceptors were correlated with visual field sensitivity at corresponding retinal locations following reductions in inner retinal thickness. The photoreceptor outer segments were shorter and exhibited greater variability in retinal areas associated with visual field losses compared with normal or less affected areas of the same patient's visual field. These results demonstrate that nonglaucomatous and glaucomatous optic neuropathies are associated with outer retinal changes following long-term inner retinal pathology.

Comparison of retinal nerve fiber layer thickness in normal eyes using time-domain and spectral-domain optical coherence tomography

PURPOSE

To compare retinal nerve fiber layer (RNFL) thickness measurements between 3 different spectral-domain optical coherence tomography (SD-OCT) instruments (Spectralis; Heidelberg Engineering; Cirrus; Carl Zeiss Meditec; RTVue; Optovue, Inc) and one time-domain OCT (Stratus; Carl Zeiss Meditec).

DESIGN

Prospective, cross-sectional study.

METHODS

RNFL thickness was measured on both eyes of 40 normal subjects using Stratus, Spectralis, RTVue, and Cirrus OCT on the same day. Scans were repeated 2 to 8 weeks later in the same fashion. Agreement with Stratus was evaluated for each SD-OCT and intervisit reproducibility was assessed for all machines.

RESULTS

Mean RNFL thickness determined by each of the 3 SD-OCT instruments was highly correlated with Stratus (r = 0.87-0.91). The mean RNFL thickness (mean ± standard deviation) was 110.1 ± 12.8 μm for Stratus, 106.6 ± 12.8 μm for Spectralis, 98.7 ± 10.9 μm for Cirrus, and 112.8 ± 13.2 μm for RTVue. The average differences between each SD-OCT and Stratus for mean RNFL thickness were all statistically significant (P ≤ .001), as were most quadrant measurements. All 4 instruments demonstrated excellent intraclass correlation coefficient values for mean RNFL thickness (0.90-0.97). However, intervisit variability was lowest for RTVue as evidenced by reproducibility values, followed by Stratus, Cirrus, and Spectralis (6.59, 8.83, 8.89, and 11.72 μm, respectively).

CONCLUSIONS

RNFL measurements taken with Spectralis, RTVue, and Cirrus all have excellent correlation to Stratus, with good reproducibility in normal eyes. Despite high correlations, RNFL values are significantly different between instruments and should not be used interchangeably.

Imaging of the retinal nerve fibre layer with spectral domain optical coherence tomography for glaucoma diagnosis

Optical coherence tomography (OCT) techniques have been applied to develop a new generation of the technology, called spectral domain (SD) or Fourier domain (FD) OCT. The commercially available SD-OCT technology offers benefits over the conventional time domain (TD) OCT such as a scanning speed up to 200 times faster and higher axial resolution (3 to 6 μm). Overall, SD-OCT offers improved performance in terms of reproducibility. SD-OCT has a level of discriminating capability, between healthy and perimetric glaucoma eyes similar to that obtained with TD-OCT. Furthermore, the capabilities and features of SD-OCT are rapidly evolving, mainly due to three-dimensional imaging and image rendering. More sophisticated approaches for macular and optic disc assessment are expected to be employed in clinical practice. Analysis software should be further refined for interpretation of SD-OCT images in order to enhance the sensitivity and specificity of glaucoma diagnostics. Most importantly for SD-OCT is determination of its ability to diagnostic structural glaucomatous progression. Considering the recent launch time of the commercially available SD-OCT and slow progressing characteristic of glaucoma, we must wait for longitudinal SD-OCT data, with a long enough follow-up, to become available.

Diagnostic Capability of Scanning Laser Polarimetry with and without Enhanced Corneal Compensation and Optical Coherence Tomography

Purpose

TO compare the abilities of the current commercially available versions of scanning laser polarimetry (SLP) and optical coherence tomography (OCT), SLP-variable corneal compensation (VCC), SLP–enhanced corneal compensation (ECC), and high-definition (HD) OCT, in discriminating between healthy eyes and those with early-to-moderate glaucomatous visual field loss.

Methods

Healthy volunteers and patients with glaucoma who met the eligibility criteria were consecutively enrolled in this prospective, cross-sectional, observational study. Subjects underwent complete eye examination, automated perimetry, SLP-ECC, SLP-VCC, and HD-OCT Scanning laser polarimetry parameters were recalculated in 90-degree segments (quadrants) in the calculation circle to be compared. Areas under the receiver operating characteristic curve (AUROCs) were calculated for every parameter in order to compare the ability of each imaging modality to differentiate between normal and glaucomatous eyes.

Results

Fifty-five normal volunteers (mean age 59.1 years) and 33 patients with glaucoma (mean age 63.8 years) were enrolled. Average visual field mean deviation was −6.69 dB (95% confidence interval −8.07 to −5.31) in the glaucoma group. The largest AUROCs were associated with nerve fiber indicator (0.880 and 0.888) for the SLP-VCC and SLP-ECC, respectively, and with the average thickness in the HD-OCT (0.897).

Conclusions

The best performing indices for the SLP-VCC, SLP-ECC, and HD OCT gave similar AUROCs, showing moderate diagnostic accuracy in patients with early to moderate glaucoma. Further studies are needed to evaluate the ability of these technologies to discriminate between normal and glaucomatous eyes.

Tracking longitudinal retinal changes in experimental ocular hypertension using the cSLO and spectral domain-OCT

PURPOSE

Involvement of the outer retina is controversial in glaucoma. The aim of this study was to test, first, whether the outer retina is affected in experimental ocular hypertension (OHT) and, second, whether whole retinal thickness can be used as a surrogate marker of glaucomatous change.

METHODS

OHT was surgically induced in 20 Dark Agouti rats. Animals were imaged using a modified Spectralis OCT (Heidelberg Engineering, Heidelberg, Germany) at baseline and at 3 and 8 weeks after OHT induction. Measurements were recorded for whole and individual retinal layer thickness in four regions-temporal, superior, nasal, and inferior-around the optic nerve head.

RESULTS

Whole retinal thickness in normal eyes was 172.19 ± 5.17 μm, with no significant regional differences. OHT caused a significant reduction in whole retinal thickness and the outer nuclear layer (ONL) at 3 and 8 weeks (P < 0.05), along with the expected thinning of the retinal nerve fiber layer (RNFL). Whole retinal thickness correlated well with RNFL (P = 0.035) and ONL (P ≤ 0.001) changes. Sensitivity of RNFL and ONL to IOP exposure appeared greater at 3 than at 8 weeks. In addition, regional profiles were significantly altered in the ONL and RNFL after OHT induction.

CONCLUSIONS

Adaptation of the Spectralis OCT enables tracking of structural damage in experimental rat OHT. Here the authors show evidence of glaucomatous damage in the outer retinal layers of this model with significant regional changes and highlight whole retinal thickness in the rat as a useful surrogate marker of inner and outer retinal changes. The authors believe that the OCT data can provide useful information with regard to clinical management.

Detection of glaucoma progression with stratus OCT retinal nerve fiber layer, optic nerve head, and macular thickness measurements

PURPOSE

To evaluate and compare the ability of optical coherence tomography (OCT) retinal nerve fiber layer (RNFL), optic nerve head, and macular thickness parameters to detect progressive structural damage in glaucoma.

METHODS

This observational cohort study included 253 eyes of 253 patients. Images were obtained annually with the Stratus OCT (Carl Zeiss Meditec, Inc., Dublin, CA) along with optic disc stereophotographs and standard automated perimetry (SAP) visual fields. The median follow-up time was 4.01 years. Progression was determined by the Guided Progression Analysis software for SAP (Carl Zeiss Meditec, Inc.) and by masked assessment of optic disc stereophotographs performed by expert graders. Random coefficient models and receiver operating characteristic (ROC) curves were used to evaluate the relationship between change in Stratus OCT parameters over time and progression as determined by SAP and/or stereophotographs.

RESULTS

From the 253 eyes, 31 (13%) showed progression over time by stereophotographs and/or SAP. Mean rates of change in average RNFL thickness were significantly higher for progressors compared with nonprogressors (-0.72 mum/y vs. 0.14 mum/y; P = 0.004), with sensitivity of 77% for specificity of 80%. RNFL parameters performed significantly better than ONH and macular thickness measurements in discriminating progressors from nonprogressors. The parameters with the largest ROC curve areas for each scanning area were inferior RNFL thickness (0.84), cup area (0.66), and inferior inner macula thickness (0.64).

CONCLUSIONS

Stratus OCT RNFL parameters discriminated between eyes progressing by visual fields or optic disc photographs and eyes that remained stable by these methods and performed significantly better than ONH and macular thickness parameters in detecting change over time.