Domain Optical Coherence Tomography Images Research Articles

Frequency and Causes of Segmentation Errors in Spectral Domain Optical Coherence Tomography Imaging in Glaucoma

Frequency and Causes of Segmentation Errors in Spectral Domain Optical Coherence Tomography Imaging in Glaucoma

Recovery Course of Macular Structure after Macular Hole Surgery: Using a Spectral Domain Optical Coherence Tomography Image

Recovery Course of Macular Structure after Macular Hole Surgery: Using a Spectral Domain Optical Coherence Tomography Image

Use of Mechanical Turk as a MapReduce Framework for Macular OCT Segmentation

Purpose. To evaluate the feasibility of using Mechanical Turk as a massively parallel platform to perform manual segmentations of macular spectral domain optical coherence tomography (SD-OCT) images using a MapReduce framework. Methods. A macular SD-OCT volume of 61 slice images was map-distributed to Amazon Mechanical Turk. Each Human Intelligence Task was set to $0.01 and required the user to draw five lines to outline the sublayers of the retinal OCT image after being shown example images. Each image was submitted twice for segmentation, and interrater reliability was calculated. The interface was created using custom HTML5 and JavaScript code, and data analysis was performed using R. An automated pipeline was developed to handle the map and reduce steps of the framework. Results. More than 93,500 data points were collected using this framework for the 61 images submitted. Pearson's correlation of interrater reliability was 0.995 (p < 0.0001) and coefficient of determination was 0.991. The cost of segmenting the macular volume was $1.21. A total of 22 individual Mechanical Turk users provided segmentations, each completing an average of 5.5 HITs. Each HIT was completed in an average of 4.43 minutes. Conclusions. Amazon Mechanical Turk provides a cost-effective, scalable, high-availability infrastructure for manual segmentation of OCT images.

PREVALENCE OF RETICULAR PSEUDODRUSEN IN AGE-RELATED MACULAR DEGENERATION USING MULTIMODAL IMAGING.

To determine the rate of reticular pseudodrusen (RPD) in age-related macular degeneration using multimodal imaging, including color fundus photography, the blue channel image of fundus photography, infrared reflectance, fundus autofluorescence, multicolor imaging, and spectral domain optical coherence tomography, as well as to compare the sensitivities and specificities of these modalities for detecting RPD. This prospective study included 243 eyes from 125 consecutive patients with age-related macular degeneration. They underwent fundus examination including color fundus photography, blue channel, infrared reflectance, fundus autofluorescence, multicolor imaging, and spectral domain optical coherence tomography in both eyes. To be considered as having RPD, eyes had to have reticular patterns on spectral domain optical coherence tomography in a large studied cube of 30° × 25° or on infrared reflectance with at least one other examination. The mean age of the 125 patients was 81.1 years (± 8.1). Eighty-six patients (68.8%) were diagnosed with RPD. Spectral domain optical coherence tomography, infrared reflectance, and multicolor imaging had the highest sensitivity (99.3, 84.6, and 87.1%, respectively) and specificity (100%). The color fundus photography, blue channel, and fundus autofluorescence had lower sensitivity to detect RPD. Reticular pseudodrusen is frequently associated with soft drusen in patients with age-related macular degeneration. As RPD may be rarely located only in the perifoveal area, spectral domain optical coherence tomography with a larger cube (30 × 25°) than that usually used (20 × 20°) had the highest sensitivity and specificity to detect RPD and is recommended to optimize the rate of detection.

Effect of intravitreal anti-VEGF on choroidal thickness in patients with diabetic macular edema using spectral domain OCT.

To evaluate choroidal thickness (CT) using spectral domain optical coherence tomography (SD-OCT) imaging at baseline and 6 months after intravitreal anti-vascular endothelial growth factor (anti-VEGF) treatment in patients with diabetic macular edema (DME). A retrospective chart review was performed to identify patients with DME who underwent intravitreal injection of anti-VEGF (bevacizumab or ranibizumab) in a pro re nata (PRN) regimen. Subfoveal choroidal thickness was compared between values obtained at baseline and at 6-month follow-up visits. Thirty-nine eyes (15 females, 24 males) from 39 patients were enrolled (mean age, 62.43 ± 8.7 years; range, 44-79 years). Twenty-three and 16 eyes were treated with ranibizumab and bevacizumab respectively. The mean number of anti-VEGF injections was 2.28 ± 1.27 (range, 1-5). Mean nasal, subfoveal, and temporal choroidal thickness (CT) measurements at baseline were 234.10 ± 8.63 µm, 246.89 ± 8.94 µm, and 238.12 ± 8.20 µm, respectively, and those at 6 months post-treatment were 210.46 ± 8.00 µm, 215.66 ± 8.29 µm, and 212.43 ± 8.14 µm, respectively. Significant differences in CT were observed between baseline and the 6-month follow-up at all measured points (p=0.0327). Over a 6-month period, the use of intravitreal anti-VEGF was associated with significant thinning of the choroid in patients with DME. The clinical significance of a thinner choroid in DME is currently unknown; however, it may contribute to long-term adverse effects on choroidal and retinal function, representing an area requiring future investigation.

Novice Reviewers Retain High Sensitivity and Specificity of Posterior Segment Disease Identification with iWellnessExam™.

Introduction. Four novices to Spectral Domain Optical Coherence Tomography (SD-OCT) image review were provided a brief lecture on the interpretation of iVue iWellnessExam™ findings (available on iVue® SD-OCT, Optovue, Inc., Fremont, CA). For a cohort of 126 (Confirmed) Normal, 101 (Confirmed) Disease subjects, iWellnessExam™ OD, OS, and OU reports were provided. Each novice independently reviewed and sorted the subjects into one of four categories: normal, retinal disease, optic nerve (ON) disease, and retinal + ON disease. Their accuracy is compared between the novices and with an expert reviewer. Results. Posterior segment disease was properly detected by novices with sensitivities of 90.6%, any disease; 84.3%, retinal disease; 88.0%, ON disease; expert sensitivity: 96.0%, 95.5%, and 90.0%, respectively; specificity: 84.3%, novices; 99.2%, expert. Novice accuracy correlates best with clinical exposure and amount of time spent reviewing each image set. The novices' negative predictive value was 92.0% (i.e., very few false negatives). Conclusions. Novices can be trained to screen for posterior segment disease efficiently and effectively using iWellnessExam™ data, with high sensitivity, while maintaining high specificity. Novice reviewer accuracy covaries with both clinical exposure and time spent per image set. These findings support exploration of training nonophthalmic technicians in a primary medical care setting.

Enface Thickness Mapping and Reflectance Imaging of Retinal Layers in Diabetic Retinopathy

PurposeTo present a method for image segmentation and generation of enface thickness maps and reflectance images of retinal layers in healthy and diabetic retinopathy (DR) subjects.MethodsHigh density spectral domain optical coherence tomography (SDOCT) images were acquired in 10 healthy and 4 DR subjects. Customized image analysis software identified 5 retinal cell layer interfaces and generated thickness maps and reflectance images of the total retina (TR), inner retina (IR), outer retina (OR), and the inner segment ellipsoid (ISe) band. Thickness maps in DR subjects were compared to those of healthy subjects by generating deviation maps which displayed retinal locations with thickness below, within, and above the normal 95% confidence interval.ResultsIn healthy subjects, TR and IR thickness maps displayed the foveal depression and increased thickness in the parafoveal region. OR and ISe thickness maps showed increased thickness at the fovea, consistent with normal retinal anatomy. In DR subjects, thickening and thinning in localized regions were demonstrated on TR, IR, OR, and ISe thickness maps, corresponding to retinal edema and atrophy, respectively. TR and OR reflectance images showed reduced reflectivity in regions of increased thickness. Hard exudates appeared as hyper-reflective spots in IR reflectance images and casted shadows on the deeper OR and ISe reflectance images. The ISe reflectance image clearly showed the presence of focal laser scars.ConclusionsEnface thickness mapping and reflectance imaging of retinal layers is a potentially useful method for quantifying the spatial and axial extent of pathologies due to DR.

Characterizing the lacrimal punctal region using anterior segment optical coherence tomography.

Abnormalities of lacrimal punctum size and morphology probably contribute to excess tearing, with significant effects on quality-of-life for affected individuals. Our current understanding of normal punctal morphology originates from ex vivo studies, which are unlikely to capture the true nature of the living punctum. This study used enhanced depth anterior segment optical coherence tomography (OCT) to give improved characterization and understanding of lacrimal punctal structure. Qualitative and quantitative assessments were performed on spectral domain OCT images collected prospectively from 40 lower puncta of 20 healthy volunteers. The average external lower lid punctal diameter was 0.646 mm (SD 150 μm) on OCT imaging, measured at the largest diameter, which was in parallel to the mucocutaneous junction. Fifty-five per cent of puncta appeared closed, whilst the eyelids were open. Fluid menisci were visible within 73% of puncta. A postpunctal 'ampulla' was visible within three systems, one of which was imaged through the conjunctival surface. Ampullary dilatation occurred laterally, rather than at the medial wall. Optical coherence tomography provides quick and non-invasive assessment of the lacrimal punctum and its neighbouring tissue layers. This assessment of punctal size and morphology has the potential for further investigation of punctal physiology, for aiding diagnosis, and for monitoring the results of treatment. The average external diameter of the punctal opening measured in this study is greater than that recorded in anatomical textbooks.

WIDE-FIELD SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY.

To describe wide-field spectral domain optical coherence tomography morphologic relationships of the vitreous, retina, and choroid in healthy and pathologic eyes. Standardized horizontal, vertical, and two oblique (supertemporal to inferonasal and supranasal to inferotemporal) spectral domain optical coherence tomography sections were collected for each patient. For extramacular imaging, images were obtained from 8 locations: (1) nasal to the optic disk, (2) extreme nasal periphery, (3) superior to the superotemporal vascular arcade, (4) extreme superior periphery, (5) inferior to the inferotemporal vascular arcade, (6) extreme inferior periphery, (7) temporal to the macula, and (8) extreme temporal periphery. Wide-angle montage images of optical coherence tomography from equator-to-equator were composed with a montaging software. Wide-field spectral domain optical coherence tomography scans were obtained in 10 healthy subjects, in 7 patients with central serous chorioretinopathy, in 5 patients with wet age-related macular degenerations, in 5 patients with dry age-related macular degenerations, in 4 patients with retinitis pigmentosa, and in 1 patient with acute exudative polymorphous vitelliform maculopathy. The novel approach of montaging spectral domain optical coherence tomography images to examine relationships between the choroid, retina, and associated structures adjacent to and outside of the macula may have a number of relevant applications in the study of vitreoretinal interface, paramacular and macular pathologic features.

Recognition of fabric weave patterns using optical coherence tomography

Traditional methods involve extracting individual warp or weft yarns from the fabric in order to identify the weave repeat manually. This process can become tedious due to its manual nature. Therefore, automatic methods capable of identifying woven fabric repeat are utilized. These methods in general require complex algorithms and calculations. Optical coherence tomography (OCT) is a nondestructive and noncontact technique that allows high-resolution imaging. This paper describes the application of spectral domain optical coherence tomography imaging technique for identifying woven fabric repeat. We present the OCT scans of fabrics from which the weave matrixes were identified. We conclude that optical coherence tomography can be used to automatically recognize fabric weave patterns.

Imaging of the internal nasal valve using long‐range Fourier domain optical coherence tomography

To evaluate for the first time the feasibility and methodology of long-range Fourier domain optical coherence tomography (LR-OCT) imaging of the internal nasal valve (INV) area in healthy individuals. Prospective individual cohort study. For 16 individuals, OCT was performed in each nare. The angle and the cross-sectional area of the INV were measured. OCT images were compared to corresponding digital pictures recorded with a flexible endoscope. INV angle measured by OCT was found to be 18.3° ± 3.1° (mean ± standard deviation). The cross-sectional area was 0.65 ± 0.23 cm(2) . The INV angle measured by endoscopy was 18.8° ± 6.9°. There was no statistically significant difference between endoscopy and OCT concerning the mean INV angle (P = .778), but there was a significant difference in test precision (coefficient of variance 50% vs. 15%; P < .001). LR-OCT proved to be a fast and easily performed method. OCT could accurately quantify the INV area. The values of the angle and the cross-sectional area of the INV were reproducible and correlated well with the data seen with other methods. Changes in size could be reliably delineated. Endoscopy showed similar values but was significantly less precise. 2b. Laryngoscope, 126:E97-E102, 2016.

Structural dissociation of optic disc margin components with optic disc tilting: a spectral domain optical coherence tomography study.

To investigate the dissociation of the Bruch's membrane opening (BMO) from the scleral canal opening (SO) of the optic disc. In this prospective, cross-sectional, observational study, 101 eyes from 101 patients or suspected subjects of primary open angle glaucoma were included. Enhanced depth imaging spectral domain optical coherence tomography images along the long axis of the optic disc were used to visualize better the deep structures around the optic disc on both the temporal and nasal sides. The distances between the BMO and SO were measured at the temporal and nasal sides of the optic disc, and their correlations with age, axial length, intraocular pressure, disc size, disc ovality index, disc torsion degree, and visual field mean deviation were investigated. The temporal and nasal distances of BMO from SO correlated significantly with each other (R = 0.632, P < 0.0001). By multiple linear regression analysis, significant correlations were found for disc ovality index (temporal: β = -0.691, P < 0.0001; nasal: β = -0.420, P < 0.0001) and axial length (temporal: β = 0.224, P = 0.002; nasal: β = 0.310, P = 0.001). The other factors did not show any significant correlation. Locations of the SO at not only the temporal, but also the nasal side of the optic disc are nasally shifted from the BMO with optic disc tilting and axial length elongation in glaucomatous eyes, and are significantly correlated to each other. The nasal shift of the deep structures of the optic disc should be considered especially when assessing myopic eyes with optic disc tilt.

Retinal involvement in amyotrophic lateral sclerosis: a study with optical coherence tomography and diffusion tensor imaging.

Although motor neuron degeneration is the predominant feature in ALS, recent data point to a more widespread pathology also comprising non-motor symptoms. Retinal thinning has been reported in a variety of neurodegenerative conditions. Yet, studies of retinal involvement in ALS are sparse and results are heterogeneous. We studied retinal alterations in ALS using a systematic approach combining Optical Coherence Tomography (OCT), Diffusion Tensor Imaging (DTI) and clinical phenotyping. We hypothesized that selective changes of specific retinal layers may be a reflection of overall neurodegeneration as measured by DTI. Spectral domain OCT images were analyzed to calculate the average thickness of retinal layers in 71 ALS patients and 20 controls. In 30 patients, the region of interest (ROI) based fractional anisotrophy (FA) was measured in the corticospinal tract (CST), as this region is preferentially affected by motor neuron degeneration. Clinical data were collected for correlation analysis. Patients showed a significant thinning of the inner nuclear layer (INL; p=0.04) and the retinal nerve fibre layer (RNFL; p=0.004) compared to controls. We saw significant correlations between retinal thickness and FA values of the CST in patients (p=0.005). No significant correlation between clinical parameters and retinal involvement was observed. Our study provides evidence for a retinal involvement in ALS. Interestingly, ALS patients show a reduction in FA of the CST, which is correlated to retinal thinning. We conclude that retinal involvement is in fact associated to overall neurodegeneration and may be regarded as a potential technical biomarker in ALS.

Interpretation of Flood-Illuminated Adaptive Optics Images in Subjects with Retinitis Pigmentosa.

The purpose of this study was to correlate features on flood-illuminated adaptive optics (AO) images with color fundus, fundus autofluorescence (FAF) and spectral domain optical coherence tomography (SD-OCT) images in patients with retinitis pigmentosa (RP). We imaged 39 subjects diagnosed with RP using the rtx1™ flood-illuminated AO camera from Imagine Eyes (Orsay, France). We observed a correlation between hyper-autofluoresence changes on FAF, disruption of the interdigitation zone (IZ) on SD-OCT and loss of reflective cone profiles on AO. Four main patterns of cone-reflectivity were seen on AO: presumed healthy cone mosaics, hypo-reflective blurred cone-like structures, higher frequency disorganized hyper-reflective spots, and lower frequency hypo-reflective spots. These regions were correlated to progressive phases of cone photoreceptor degeneration observed using SD-OCT and FAF. These results help provide interpretation of en face images obtained by flood-illuminated AO in subjects with RP. However, significant ambiguity remains as to what truly constitutes a cone, especially in areas of degeneration. With further refinements in technology, flood illuminated AO imaging has the potential to provide rapid, standardized, longitudinal and lower cost imaging in patients with retinal degeneration.

THE INFLUENCE OF VITREOMACULAR ADHESION ON OUTCOMES AFTER AFLIBERCEPT THERAPY FOR NEOVASCULAR AGE-RELATED MACULAR DEGENERATION.

To evaluate the influence of vitreomacular attachment on outcomes after intravitreal aflibercept for neovascular age-related macular degeneration. In a prospective case series, eyes with neovascular age-related macular degeneration were treated with intravitreal aflibercept, given as 3 consecutive monthly injections, followed by further injection every 2 months. Spectral domain optical coherence tomography images were reviewed at each visit to determine the attachment of the posterior hyaloid. Best-corrected visual acuity and retinal thickness were also recorded. Outcomes at Months 2 and 6 were compared between the eyes with persistent vitreomacular attachment (Stage 1) and those with posterior vitreous detachment (Stages 2 or 3 PVD) at baseline. At baseline, 30 eyes had Stage 1 PVD and 63 eyes had either Stage 2 or 3 PVD. Although there was a trend for both greater visual acuity gains and reductions in retinal thickness for the eyes with Stages 2 or 3 PVD, this failed to reach significance. Baseline visual acuity and age were negatively associated with visual acuity change, and baseline retinal thickness alone was associated with retinal thickness change. Visual acuity, retinal thickness, and age at the baseline examination, but not PVD status, are associated with functional and anatomical outcomes after intravitreal aflibercept for neovascular age-related macular degeneration.

Analysis of Segmentation Algorithms in Colour Fundus and OCT Images for Glaucoma Detection

Objectives: Glaucoma is an eye disease which affects the optic nerve head and results in visual impairment. In this paper, we analyze the various segmentation algorithms for glaucoma detection using colour fundus images and spectral domain Optical Coherence Tomography (OCT) images of same subjects. Methods/Statistical analysis: In fundus images, the disc and the cup regions are segmented separately using four different segmentation algorithms namely Otsu method, Region growing, Hill climbing and Fuzzy c-means clustering algorithms. In OCT images, the cup and the disc diameter are measured by segmenting the retinal nerve fibre and retinal pigment epithelium layers. Findings: From both the analysis, the cup to disc ratio (CDR) is calculated and compared with the clinical values. The experimental results show that the performance error in the OCT image analysis is less when compared to the fundus image analysis. Conclusion: Thus, it has been concluded that glaucoma detection can be done more effectively using OCT image analysis.Keywords: CDR, Colour Fundus Image, Fuzzy C-Means Algorithm, OCT Image

Quantitative Analysis of Mouse Retinal Layers Using Automated Segmentation of Spectral Domain Optical Coherence Tomography Images.

Quantification of retinal layers using automated segmentation of optical coherence tomography (OCT) images allows for longitudinal studies of retinal and neurological disorders in mice. The purpose of this study was to compare the performance of automated retinal layer segmentation algorithms with data from manual segmentation in mice using the Spectralis OCT. Spectral domain OCT images from 55 mice from three different mouse strains were analyzed in total. The OCT scans from 22 C57Bl/6, 22 BALBc, and 11 C3A.Cg-Pde6b+Prph2Rd2 /J mice were automatically segmented using three commercially available automated retinal segmentation algorithms and compared to manual segmentation. Fully automated segmentation performed well in mice and showed coefficients of variation (CV) of below 5% for the total retinal volume. However, all three automated segmentation algorithms yielded much thicker total retinal thickness values compared to manual segmentation data (P < 0.0001) due to segmentation errors in the basement membrane. Whereas the automated retinal segmentation algorithms performed well for the inner layers, the retinal pigmentation epithelium (RPE) was delineated within the sclera, leading to consistently thicker measurements of the photoreceptor layer and the total retina. The introduction of spectral domain OCT allows for accurate imaging of the mouse retina. Exact quantification of retinal layer thicknesses in mice is important to study layers of interest under various pathological conditions.

INTRAOPERATIVE SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY IMAGING AFTER INTERNAL LIMITING MEMBRANE PEELING IN IDIOPATHIC EPIRETINAL MEMBRANE WITH CONNECTING STRANDS.

To report the intraoperative optical coherence tomography findings in idiopathic epiretinal membrane (ERM) with connecting strands and to describe the postoperative outcomes. A retrospective, case series study within a prospective observational intraoperative optical coherence tomography imaging study was performed. Epiretinal membranes with connecting strands were characterized on preoperative spectral domain optical coherence tomography images and assessed against corresponding intraoperative (after internal limiting membrane [ILM] peeling) and postoperative spectral domain optical coherence tomography images. Eleven locations of the connecting strands in 7 eyes were studied. The connecting strands had visible connections from the inner retinal surface to the ERM in all locations, and the reflectivity was moderate in 8 locations and high in 3 locations. After ERM and ILM peeling, disconnected strands were identified in all of the intraoperative optical coherence tomography images. The reflectivity of the remaining intraoperative strands was higher than that of the preoperative lesions and appeared as "finger-like" and branching projections. The remaining disconnected lesions were contiguous with the inner retinal layers. Postoperatively, the intraoperative lesions disappeared completely in all locations, and recurrent formation of ERM was not identified in any eyes. In ERM eyes with connecting strands, intraoperative spectral domain optical coherence tomography imaging showed moderately to highly reflective sub-ILM finger-like lesions that persist immediately after membrane and ILM peeling. Postoperatively, the hyperreflective lesions disappeared spontaneously without localized nerve fiber layer loss. The sub-ILM connecting strands may represent glial retinal attachments.

Characterizing the Impact of Off-Axis Scan Acquisition on the Reproducibility of Total Retinal Thickness Measurements in SDOCT Volumes.

Off-axis acquisition of spectral domain optical coherence tomography (SDOCT) images has been shown to increase total retinal thickness (TRT) measurements. We analyzed the reproducibility of TRT measurements obtained using either the retinal pigment epithelium (RPE) or Bruch's membrane as reference surfaces in off-axis scans intentionally acquired through multiple pupil positions. Five volumetric SDOCT scans of the macula were obtained from one eye of 25 normal subjects. One scan was acquired through a central pupil position, while subsequent scans were acquired through four peripheral pupil positions. The internal limiting membrane, the RPE, and Bruch's membrane were segmented using automated approaches. These volumes were registered to each other and the TRT was evaluated in 9 Early Treatment of Diabetic Retinopathy Study (ETDRS) regions. The reproducibility of the TRT obtained using the RPE was computed using the mean difference, coefficient of variation (CV), and the intraclass correlation coefficient (ICC), and compared to those obtained using Bruch's membrane as the reference surface. A secondary set of 1545 SDOCT scans was also analyzed in order to gauge the incidence of off-axis scans in a typical acquisition environment. The photoreceptor tips were dimmer in off-axis images, which affected the RPE segmentation. The overall mean TRT difference and CV obtained using the RPE were 7.04 ± 4.31 μm and 1.46%, respectively, whereas Bruch's membrane was 1.16 ± 1.00 μm and 0.32%, respectively. The ICCs at the subfoveal TRT were 0.982 and 0.999, respectively. Forty-one percent of the scans in the secondary set showed large tilts (> 6%). RPE segmentation is confounded by its proximity to the interdigitation zone, a structure strongly affected by the optical Stiles-Crawford effect. Bruch's membrane, however, is unaffected leading to a more robust segmentation that is less dependent upon pupil position. The way in which OCT images are acquired can independently affect the accuracy of automated retinal thickness measurements. Assessment of scan angle in a clinical dataset demonstrates that off-axis scans are common, which emphasizes the need for caution when relying on automated thickness parameters when this component of scan acquisition is not controlled for.

In Vivo Changes in Lamina Cribrosa Microarchitecture and Optic Nerve Head Structure in Early Experimental Glaucoma

The lamina cribrosa likely plays an important role in retinal ganglion cell axon injury in glaucoma. We sought to (1) better understand optic nerve head (ONH) structure and anterior lamina cribrosa surface (ALCS) microarchitecture between fellow eyes of living, normal non-human primates and (2) characterize the time-course of in vivo structural changes in the ONH, ALCS microarchitecture, and retinal nerve fiber layer thickness (RNFLT) in non-human primate eyes with early experimental glaucoma (EG). Spectral domain optical coherence tomography (SDOCT) images of the ONH were acquired cross-sectionally in six bilaterally normal rhesus monkeys, and before and approximately every two weeks after inducing unilateral EG in seven rhesus monkeys. ONH parameters and RNFLT were quantified from segmented SDOCT images. Mean ALCS pore area, elongation and nearest neighbor distance (NND) were quantified globally, in sectors and regionally from adaptive optics scanning laser ophthalmoscope images. In bilaterally normal monkeys, ONH parameters were similar between fellow eyes with few inter-eye differences in ALCS pore parameters. In EG monkeys, an increase in mean ALCS Depth (ALCSD) was the first structural change measured in 6 of 7 EG eyes. A decrease in mean minimum rim width (MRW) simultaneously accompanied this early change in 4 of 6 EG eyes and was the first structural change in the 7th EG eye. Mean ALCS pore parameters were among the first or second changes measured in 4 EG eyes. Mean ALCS pore area and NND increased in superotemporal and temporal sectors and in central and peripheral regions at the first time-point of change in ALCS pore geometry. RNFLT and/or mean ALCS radius of curvature were typically the last parameters to initially change. Survival analyses found mean ALCSD was the only parameter to significantly show an initial change prior to the first measured loss in RNFLT across EG eyes.