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Glaucoma: HELP
Articles by Nicholas G. Strouthidis
Based on 29 articles published since 2010
(Why 29 articles?)
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Between 2010 and 2020, N. Strouthidis wrote the following 29 articles about Glaucoma.
 
+ Citations + Abstracts
Pages: 1 · 2
1 Editorial Neuroprotection and other novel therapies for glaucoma. 2013

Nucci, Carlo / Strouthidis, Nicholas G / Khaw, Peng Tee. · ·Curr Opin Pharmacol · Pubmed #23142029.

ABSTRACT: -- No abstract --

2 Review Glaucoma management in the era of artificial intelligence. 2020

Devalla, Sripad Krishna / Liang, Zhang / Pham, Tan Hung / Boote, Craig / Strouthidis, Nicholas G / Thiery, Alexandre H / Girard, Michael J A. ·Department of Biomedical Engineering, National University of Singapore, Singapore, Singapore. · Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore. · School of Optometry & Vision Sciences, Cardiff University, Cardiff, UK. · Newcastle Research & Innovation Institute, Singapore, Singapore. · NIHR Biomedical Research Centre, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK. · Discipline of Clinical Ophthalmology and Eye Health, University of Sydney, Sydney, New South Wales, Australia. · Department of Statistics and Applied Probability, National University of Singapore, Singapore, Singapore. · Department of Biomedical Engineering, National University of Singapore, Singapore, Singapore mgirard@nus.edu.sg. ·Br J Ophthalmol · Pubmed #31640973.

ABSTRACT: Glaucoma is a result of irreversible damage to the retinal ganglion cells. While an early intervention could minimise the risk of vision loss in glaucoma, its asymptomatic nature makes it difficult to diagnose until a late stage. The diagnosis of glaucoma is a complicated and expensive effort that is heavily dependent on the experience and expertise of a clinician. The application of artificial intelligence (AI) algorithms in ophthalmology has improved our understanding of many retinal, macular, choroidal and corneal pathologies. With the advent of deep learning, a number of tools for the classification, segmentation and enhancement of ocular images have been developed. Over the years, several AI techniques have been proposed to help detect glaucoma by analysis of functional and/or structural evaluations of the eye. Moreover, the use of AI has also been explored to improve the reliability of ascribing disease prognosis. This review summarises the role of AI in the diagnosis and prognosis of glaucoma, discusses the advantages and challenges of using AI systems in clinics and predicts likely areas of future progress.

3 Review Translating ocular biomechanics into clinical practice: current state and future prospects. 2015

Girard, Michaël J A / Dupps, William J / Baskaran, Mani / Scarcelli, Giuliano / Yun, Seok H / Quigley, Harry A / Sigal, Ian A / Strouthidis, Nicholas G. ·In Vivo Biomechanics Laboratory, Department of Biomedical Engineering, National University of Singapore , Singapore . ·Curr Eye Res · Pubmed #24832392.

ABSTRACT: Biomechanics is the study of the relationship between forces and function in living organisms and is thought to play a critical role in a significant number of ophthalmic disorders. This is not surprising, as the eye is a pressure vessel that requires a delicate balance of forces to maintain its homeostasis. Over the past few decades, basic science research in ophthalmology mostly confirmed that ocular biomechanics could explain in part the mechanisms involved in almost all major ophthalmic disorders such as optic nerve head neuropathies, angle closure, ametropia, presbyopia, cataract, corneal pathologies, retinal detachment and macular degeneration. Translational biomechanics in ophthalmology, however, is still in its infancy. It is believed that its use could make significant advances in diagnosis and treatment. Several translational biomechanics strategies are already emerging, such as corneal stiffening for the treatment of keratoconus, and more are likely to follow. This review aims to cultivate the idea that biomechanics plays a major role in ophthalmology and that the clinical translation, lead by collaborative teams of clinicians and biomedical engineers, will benefit our patients. Specifically, recent advances and future prospects in corneal, iris, trabecular meshwork, crystalline lens, scleral and lamina cribrosa biomechanics are discussed.

4 Review Recent advances in OCT imaging of the lamina cribrosa. 2014

Sigal, Ian A / Wang, Bo / Strouthidis, Nicholas G / Akagi, Tadamichi / Girard, Michael J A. ·Department of Ophthalmology, UPMC Eye Center, Eye and Ear Institute, Ophthalmology and Visual Science Research Center, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, USA. · NIHR Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore. · Department of Ophthalmology and Visual Sciences, Kyoto University Graduate School of Medicine, Kyoto, Japan. · Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore In vivo Biomechanics Laboratory, Department of Biomedical Engineering, National University of Singapore, Singapore, Singapore. ·Br J Ophthalmol · Pubmed #24934221.

ABSTRACT: The lamina cribrosa (LC) is believed to be the site of injury to retinal ganglion cell axons in glaucoma. The ability to visualise this structure has the potential to help increase our understanding of the disease and be useful in the early detection of glaucoma. While for many years the research on the LC was essentially dependent on histology and modelling, a number of recent advances in optical coherence tomography (OCT) have dramatically improved the ability to visualise the LC, such that it is now possible to image the LC in vivo in humans and animals. In this review, we highlight recent advances in OCT imaging of the LC, in the technology, processing and analysis, and discuss the impact that these will have on the ability to diagnose and monitor glaucoma, as well as to expand our understanding of its pathophysiology. With this manuscript, we aspire to share our excitement on the achievements and potential of recent developments as well as advise caution regarding the challenges that remain before imaging of the LC and optic nerve can be used routinely in clinical practice.

5 Review Teleglaucoma: ready to go? 2014

Strouthidis, N G / Chandrasekharan, G / Diamond, J P / Murdoch, I E. ·NIHR Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK Singapore Eye Research Institute, Singapore, Singapore. · Institute of Ophthalmology, London, UK. · Bristol Eye Hospital, Bristol, UK. ·Br J Ophthalmol · Pubmed #24723617.

ABSTRACT: Telemedicine technologies and services allow today's ophthalmic clinicians to remotely diagnose, manage and monitor several ophthalmic conditions from a distance. But is this the case for glaucomas? There has been a proliferation of telemedicine friendly devices in recent years that improves the capabilities of the clinician in managing glaucomas. The existing instruments still need to align themselves with accepted industry standards. There are successful programmes running in several areas of the world. The safety and efficacy of these programmes needs further exploration. The inability of a single device or test to diagnose glaucomas satisfactorily has also hampered progress in remotely diagnosing these conditions. There is, however, significant potential for telemedicine-friendly devices to remotely monitor the progress of glaucoma and, thereby, reduce some of the workload on an overstretched health service.

6 Review Imaging of the lamina cribrosa in glaucoma: perspectives of pathogenesis and clinical applications. 2013

Kim, Tae-Woo / Kagemann, Larry / Girard, Michaël J A / Strouthidis, Nicholas G / Sung, Kyung Rim / Leung, Christopher K / Schuman, Joel S / Wollstein, Gadi. ·Department of Ophthalmology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seoul, Republic of Korea. ·Curr Eye Res · Pubmed #23768229.

ABSTRACT: The lamina cribrosa (LC) is a sieve-like structure in the sclera where retinal ganglion cell axons exit from the eye. The LC has been known to play a critical role in the pathogenesis of glaucoma. With the advent of imaging technologies, such as enhanced depth imaging, spectral-domain optical coherence tomography (OCT) enables us to unveil the LC in vivo features. The application of adaptive optics technology and a compensatory image-processing algorithm has further improved the visualization of the beams and pores and neural pathways of the LC and the scleral insertion sites. Monitoring the changes of these structures in relation to acute and chronic elevation of intraocular pressure would be germane to decipher the relationship between the stress and strain response of the LC and optic nerve damage and improve our understanding of glaucoma pathophysiology. While the impact of investigating the integrity of LC is substantive, considerable challenges remain for imaging the LC. Nevertheless, with the rapid development of the OCT technology, it is expected that some of these limitations can be overcome and the potentials of LC imaging will be unraveled.

7 Review Altering the way the optic nerve head responds to intraocular pressure-a potential approach to glaucoma therapy. 2013

Strouthidis, Nicholas G / Girard, Michael J A. ·NIHR Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, EC1 V 2PD, UK. nick.strouthidis@moorfields.nhs.uk ·Curr Opin Pharmacol · Pubmed #22999652.

ABSTRACT: Over the past decade, engineering principles have been used to explain why a mechanical load, intraocular pressure, can lead to the development of glaucomatous optic neuropathy. This has led to the 'biomechanical theory' of glaucoma, which posits that the behavior of optic nerve head connective tissues (specifically within the peripapillary sclera and lamina cribrosa) in response to intraocular pressure (regardless of its magnitude) can directly and indirectly influence the physiology and pathophysiology of the optic nerve head. Given that the biomechanics of the sclera and lamina cribrosa probably influence retinal ganglion cell loss in glaucoma, the idea that altering biomechanical behavior might be protective against glaucoma is an appealing notion. There is some evidence to suggest that stiffening the peripapillary sclera may be protective against the development of glaucoma in an animal model. It is technically possible to stiffen the sclera in vivo using collagen cross-linking techniques already applied in vivo to the cornea in the treatment of keratoconus. It has yet to be established whether scleral cross-linking is safe in humans and that it confers anything more than a theoretical advantage in terms of reducing the risk of glaucomatous damage.

8 Article The Relationship Between Ambient Atmospheric Fine Particulate Matter (PM2.5) and Glaucoma in a Large Community Cohort. 2019

Chua, Sharon Y L / Khawaja, Anthony P / Morgan, James / Strouthidis, Nicholas / Reisman, Charles / Dick, Andrew D / Khaw, Peng T / Patel, Praveen J / Foster, Paul J / Anonymous21621124. ·National Institute for Health Research (NIHR) Biomedical Research Centre at Moorfields Eye Hospital National Health Service Foundation Trust & UCL Institute of Ophthalmology, London, United Kingdom. · UCL Institute of Ophthalmology, University College London, London, United Kingdom. · School of Optometry & Vision Sciences, Cardiff University, Cardiff, Wales, United Kingdom. · Topcon Healthcare Solutions Research & Development, Oakland, New Jersey, United States. · Bristol Medical School Translational Health Sciences, University of Bristol, Bristol, United Kingdom. ·Invest Ophthalmol Vis Sci · Pubmed #31764948.

ABSTRACT: Purpose: Glaucoma is more common in urban populations than in others. Ninety percent of the world's population are exposed to air pollution above World Health Organization (WHO) recommended limits. Few studies have examined the association between air pollution and glaucoma. Methods: Questionnaire data, ophthalmic measures, and ambient residential area air quality data for 111,370 UK Biobank participants were analyzed. Particulate matter with an aerodynamic diameter < 2.5 μm (PM2.5) was selected as the air quality exposure of interest. Eye measures included self-reported glaucoma, intraocular pressure (IOP), and average thickness of macular ganglion cell-inner plexiform layer (GCIPL) across nine Early Treatment Diabetic Retinopathy Study (ETDRS) retinal subfields as obtained from spectral-domain optical coherence tomography. We examined the associations of PM2.5 concentration with self-reported glaucoma, IOP, and GCIPL. Results: Participants resident in areas with higher PM2.5 concentration were more likely to report a diagnosis of glaucoma (odds ratio = 1.06, 95% confidence interval [CI] = 1.01-1.12, per interquartile range [IQR] increase P = 0.02). Higher PM2.5 concentration was also associated with thinner GCIPL (β = -0.56 μm, 95% CI = -0.63 to -0.49, per IQR increase, P = 1.2 × 10-53). A dose-response relationship was observed between higher levels of PM2.5 and thinner GCIPL (P < 0.001). There was no clinically relevant relationship between PM2.5 concentration and IOP. Conclusions: Greater exposure to PM2.5 is associated with both self-reported glaucoma and adverse structural characteristics of the disease. The absence of an association between PM2.5 and IOP suggests the relationship may occur through a non-pressure-dependent mechanism, possibly neurotoxic and/or vascular effects.

9 Article In Vivo Three-Dimensional Lamina Cribrosa Strains in Healthy, Ocular Hypertensive, and Glaucoma Eyes Following Acute Intraocular Pressure Elevation. 2018

Beotra, Meghna R / Wang, Xiaofei / Tun, Tin A / Zhang, Liang / Baskaran, Mani / Aung, Tin / Strouthidis, Nicholas G / Girard, Michaël J A. ·Ophthalmic Engineering & Innovation Laboratory, Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, Singapore. · Singapore Eye Research Institute, Singapore National Eye Centre, Singapore. · Duke-NUS Medical School, Singapore. · Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore. · NIHR Biomedical Research Centre, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom. · Discipline of Clinical Ophthalmology and Eye Health, University of Sydney, Sydney, New South Wales, Australia. ·Invest Ophthalmol Vis Sci · Pubmed #29340640.

ABSTRACT: Purpose: To compare in vivo lamina cribrosa (LC) strains (deformations) following acute IOP elevation in healthy, glaucoma, and ocular hypertensive subjects. Methods: There were 20 healthy, 20 high-tension primary open-angle glaucoma (POAG), 16 primary angle-closure glaucoma (PACG), and 20 ocular hypertensive (OHT; with normal visual fields) eyes studied. For each test eye, the optic nerve head was imaged three times (at baseline IOP, following an acute elevation of IOP to approximately 35 then 45 mm Hg using an ophthalmodynamomter) using optical coherence tomography (OCT). A three-dimensional (3D) strain-mapping algorithm was applied to both sets of baseline and IOP-elevated OCT volumes to extract IOP-induced 3D strains. Octant-wise LC strains were also extracted to study the pattern of local deformation. Results: The average LC strain in OHT subjects (3.96%) was significantly lower than that measured in healthy subjects (6.81%; P < 0.05). On average, POAG subjects experienced higher strain than the PACG subjects (4.05%), healthy subjects experienced higher strains than the POAG and PACG subjects, but these difference were not statistically significant. Local LC deformations showed lowest strain in the infero-temporal and temporal octant in the POAG and OHT subjects. Conclusions: We demonstrate measurable LC strains in vivo in humans as a response to acute IOP elevation. In this population, our data suggest that OHT LCs experience lower IOP-induced strains than healthy LCs.

10 Article A Deep Learning Approach to Digitally Stain Optical Coherence Tomography Images of the Optic Nerve Head. 2018

Devalla, Sripad Krishna / Chin, Khai Sing / Mari, Jean-Martial / Tun, Tin A / Strouthidis, Nicholas G / Aung, Tin / Thiéry, Alexandre H / Girard, Michaël J A. ·Ophthalmic Engineering and Innovation Laboratory, Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, Singapore. · Department of Statistics and Applied Probability, National University of Singapore, Singapore. · GePaSud, Université de la Polynésie Française, Tahiti, French Polynesia. · Singapore Eye Research Institute, Singapore National Eye Centre, Singapore. · NIHR Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom. · Discipline of Clinical Ophthalmology and Eye Health, University of Sydney, Sydney, New South Wales, Australia. · Yong Loo Lin School of Medicine, National University of Singapore, Singapore. ·Invest Ophthalmol Vis Sci · Pubmed #29313052.

ABSTRACT: Purpose: To develop a deep learning approach to digitally stain optical coherence tomography (OCT) images of the optic nerve head (ONH). Methods: A horizontal B-scan was acquired through the center of the ONH using OCT (Spectralis) for one eye of each of 100 subjects (40 healthy and 60 glaucoma). All images were enhanced using adaptive compensation. A custom deep learning network was then designed and trained with the compensated images to digitally stain (i.e., highlight) six tissue layers of the ONH. The accuracy of our algorithm was assessed (against manual segmentations) using the dice coefficient, sensitivity, specificity, intersection over union (IU), and accuracy. We studied the effect of compensation, number of training images, and performance comparison between glaucoma and healthy subjects. Results: For images it had not yet assessed, our algorithm was able to digitally stain the retinal nerve fiber layer + prelamina, the RPE, all other retinal layers, the choroid, and the peripapillary sclera and lamina cribrosa. For all tissues, the dice coefficient, sensitivity, specificity, IU, and accuracy (mean) were 0.84 ± 0.03, 0.92 ± 0.03, 0.99 ± 0.00, 0.89 ± 0.03, and 0.94 ± 0.02, respectively. Our algorithm performed significantly better when compensated images were used for training (P < 0.001). Besides offering a good reliability, digital staining also performed well on OCT images of both glaucoma and healthy individuals. Conclusions: Our deep learning algorithm can simultaneously stain the neural and connective tissues of the ONH, offering a framework to automatically measure multiple key structural parameters of the ONH that may be critical to improve glaucoma management.

11 Article Association of Functional Loss With the Biomechanical Response of the Optic Nerve Head to Acute Transient Intraocular Pressure Elevations. 2018

Tun, Tin A / Atalay, Eray / Baskaran, Mani / Nongpiur, Monisha E / Htoon, Hla M / Goh, David / Cheng, Ching-Yu / Perera, Shamira A / Aung, Tin / Strouthidis, Nicholas G / Girard, Michaël J A. ·Singapore Eye Research Institute and Singapore National Eye Centre, Singapore. · Ophthalmic Engineering and Innovation Laboratory, Department of Biomedical Engineering, National University of Singapore, Singapore. · Eskisehir Osmangazi University Faculty of Medicine, Eskisehir, Turkey. · Duke-National University of Singapore Medical School, Singapore. · Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore. · Discipline of Clinical Ophthalmology and Eye Health, University of Sydney, Sydney, Australia. · National Institute for Health Research Biomedical Research Centre, Moorfields Eye Hospital National Health Service Foundation Trust and University College London Institute of Ophthalmology, London, United Kingdom. ·JAMA Ophthalmol · Pubmed #29302683.

ABSTRACT: Importance: The acute biomechanical response of the optic nerve head (ONH) to intraocular pressure (IOP) elevations may serve as a biomarker for the development and progression of glaucoma. Objective: To evaluate the association between visual field loss and the biomechanical response of the ONH to acute transient IOP elevations. Design, Setting, and Participants: In this observational study, 91 Chinese patients (23 with primary open-angle glaucoma [POAG], 45 with primary angle-closure glaucoma, and 23 without glaucoma) were recruited from September 3, 2014, through February 2, 2017. Optical coherence tomography scans of the ONH were acquired at baseline and at 2 sequential IOP elevations (0.64 N and then 0.90 N, by applying forces to the anterior sclera using an ophthalmodynamometer). In each optical coherence tomography volume, lamina cribrosa depth (LCD) and minimum rim width (MRW) were calculated. The mean deviation (MD) and the visual field index (VFI), as assessed by automated perimetry, were correlated with IOP-induced changes of LCD and MRW globally and sectorially. Main Outcomes and Measures: The LCD, MRW, MD, and VFI. Results: Among the 91 patients, 39 (42.9%) were women; the mean (SD) age was 65.48 (7.23) years. In POAG eyes, a greater change in LCD (anterior displacement) was associated with worse MD and VFI (R = -0.64; 95% CI, -0.97 to -0.31; P = .001; and R = -0.57; 95% CI, -0.94 to -0.19; P = .005, respectively) at the first IOP elevation, and a greater reduction in MRW was also associated with worse MD and VFI (first IOP elevation: R = -0.48; 95% CI, -0.86 to -0.09; P = .02; and R = -0.57; 95% CI, -0.94 to -0.20; P = .004, respectively; second IOP elevation: R = -0.56; 95% CI, -0.98 to -0.13; P = .01; and R = -0.60; 95% CI, -1.03 to -0.17; P = .008, respectively), after adjusting for age, sex, and baseline IOP. A correlation was found between the reduction in MRW in the inferior-temporal sector and the corresponding visual field cluster in POAG eyes at the second elevation (ρ = -0.55; 95% CI, -0.78 to -0.18; P = .006). Conclusions and Relevance: The biomechanical response of the ONH to acute IOP elevations was associated with established visual field loss in POAG eyes, but not in primary angle-closure glaucoma eyes. This suggests that ONH biomechanics may be related to glaucoma severity in POAG and that the 2 glaucoma subgroups exhibit inherently different biomechanical properties.

12 Article Effect of acute intraocular pressure elevation on the minimum rim width in normal, ocular hypertensive and glaucoma eyes. 2018

Sharma, Sourabh / Tun, Tin A / Baskaran, Mani / Atalay, Eray / Thakku, Sri Gowtham / Liang, Zhang / Milea, Dan / Strouthidis, Nicholas G / Aung, Tin / Girard, Michael Ja. ·Singapore National Eye Center, Singapore Eye Research Institute, Singapore, Singapore. · Ophthalmic Engineering & Innovation Laboratory, Department of Biomedical Engineering, National University of Singapore, Singapore, Singapore. · Duke-NUS Graduate Medical School, National University of Singapore, Singapore, Singapore. · NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore, Singapore. · NIHR Biomedical Research Centre, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK. · Discipline of Clinical Ophthalmology and Eye Health, University of Sydney, Sydney, NSW, Australia. · Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore. ·Br J Ophthalmol · Pubmed #28490427.

ABSTRACT: BACKGROUND: To estimate and compare changes in the Bruch's membrane opening-minimum rim width (BMO-MRW) and area in normal, ocular hypertensive and glaucoma eyes following acute elevations in intraocular pressure (IOP). METHODS: The optic nerve heads (ONHs) of 104 subjects (31 normals, 20 ocular hypertension (OHT) and 53 with primary glaucoma) were imaged using Spectral-domain optical coherence tomography (OCT; Spectralis, Heidelberg Engineering, Germany). IOP was raised twice by applying a force (0.64 n then 0.9 n) to the anterior sclera using an ophthalmo-dynamometer. After each IOP increment, IOP was held constant, measured with a Tonopen (AVIA applanation tonometer, Reichert, Depew, New York, USA), and ONH was rescanned with OCT. In each OCT volume, BMO-MRW and area were calculated and at each IOP increment. RESULTS: The baseline MRW was significantly smaller in glaucoma subjects (174.3±54.3 µm) compared with normal (287.4±42.2 µm, p<0.001) and OHT subjects (255.4±45.3 µm, p<0.001). MRW of glaucoma subjects was significantly thinner at the first and second IOP elevations than that at baseline (both p<0.01), but no significant change was noted in normal and OHT subjects. There was no significant change of BMO area at acute IOP elevations from baseline in all diagnoses (all p>0.05). CONCLUSION: Acute IOP elevation leads to compression of the nerve fibre layers of neuroretinal rim in glaucoma subjects only without changing ONH size. This suggests that the neural and connective tissues at ONH level in glaucoma subjects are more susceptible to acute IOP episodes than OHT or normal controls.

13 Article A Digital Staining Algorithm for Optical Coherence Tomography Images of the Optic Nerve Head. 2017

Mari, Jean-Martial / Aung, Tin / Cheng, Ching-Yu / Strouthidis, Nicholas G / Girard, Michaël J A. ·GePaSud, Université de la Polynésie française, Tahiti, French Polynesia. · Singapore Eye Research Institute, Singapore National Eye Centre, Singapore ; Department of Ophthalmology, YLL School of Medicine, National University of Singapore, Singapore. · Singapore Eye Research Institute, Singapore National Eye Centre, Singapore ; Department of Ophthalmology, YLL School of Medicine, National University of Singapore, Singapore ; Ophthalmology and Visual Sciences Academic Clinical Program (Eye ACP), Duke-NUS Medical School, Singapore. · Singapore Eye Research Institute, Singapore National Eye Centre, Singapore ; NIHR Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK ; Discipline of Clinical Ophthalmology and Eye Health, University of Sydney, Sydney, NSW, Australia. · Singapore Eye Research Institute, Singapore National Eye Centre, Singapore ; Ophthalmic Engineering & Innovation Laboratory, Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, Singapore. ·Transl Vis Sci Technol · Pubmed #28174676.

ABSTRACT: PURPOSE: To digitally stain spectral-domain optical coherence tomography (OCT) images of the optic nerve head (ONH), and highlight either connective or neural tissues. METHODS: OCT volumes of the ONH were acquired from one eye of 10 healthy subjects. We processed all volumes with adaptive compensation to remove shadows and enhance deep tissue visibility. For each ONH, we identified the four most dissimilar pixel-intensity histograms, each of which was assumed to represent a tissue group. These four histograms formed a vector basis on which we 'projected' each OCT volume in order to generate four digitally stained volumes P1 to P4. Digital staining was also verified using a digital phantom, and compared with k-means clustering for three and four clusters. RESULTS: Digital staining was able to isolate three regions of interest from the proposed phantom. For the ONH, the digitally stained images P1 highlighted mostly connective tissues, as demonstrated through an excellent contrast increase across the anterior lamina cribrosa boundary (3.6 ± 0.6 times). P2 highlighted the nerve fiber layer and the prelamina, P3 the remaining layers of the retina, and P4 the image background. Further, digital staining was able to separate ONH tissue layers that were not well separated by k-means clustering. CONCLUSION: We have described an algorithm that can digitally stain connective and neural tissues in OCT images of the ONH. TRANSLATIONAL RELEVANCE: Because connective and neural tissues are considerably altered in glaucoma, digital staining of the ONH tissues may be of interest in the clinical management of this pathology.

14 Article Verification of a virtual fields method to extract the mechanical properties of human optic nerve head tissues in vivo. 2017

Zhang, Liang / Thakku, Sri Gowtham / Beotra, Meghna R / Baskaran, Mani / Aung, Tin / Goh, James C H / Strouthidis, Nicholas G / Girard, Michael J A. ·NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore, Singapore. · Ophthalmic Engineering and Innovation Laboratory, Department of Biomedical Engineering, National University of Singapore, 4 Engineering Drive 3, Block E4 #04-08, Singapore, 117583, Singapore. · Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore. · Eye-ACP, Office of Clinical, Academic and Faculty Affairs, Duke-NUS Medical School, Singapore, Singapore. · Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore. · Tissue Repair Laboratory, Department of Biomedical Engineering, National University of Singapore, Singapore, Singapore. · NIHR Biomedical Research Centre, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK. · Discipline of Clinical Ophthalmology and Eye Health, University of Sydney, Sydney, NSW, Australia. · Ophthalmic Engineering and Innovation Laboratory, Department of Biomedical Engineering, National University of Singapore, 4 Engineering Drive 3, Block E4 #04-08, Singapore, 117583, Singapore. mgirard@nus.edu.sg. · Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore. mgirard@nus.edu.sg. ·Biomech Model Mechanobiol · Pubmed #27909833.

ABSTRACT: We aimed to verify a custom virtual fields method (VFM) to estimate the patient-specific biomechanical properties of human optic nerve head (ONH) tissues, given their full-field deformations induced by intraocular pressure (IOP). To verify the accuracy of VFM, we first generated 'artificial' ONH displacements from predetermined (known) ONH tissue biomechanical properties using finite element analysis. Using such deformations, if we are able to match back the known biomechanical properties, it would indicate that our VFM technique is accurate. The peripapillary sclera was assumed anisotropic hyperelastic, while all other ONH tissues were considered isotropic. The simulated ONH displacements were fed into the VFM algorithm to extract back the biomechanical properties. The robustness of VFM was also tested against rigid body motions and noise added to the simulated displacements. Then, the computational speed of VFM was compared to that of a gold-standard stiffness measurement method (inverse finite element method or IFEM). Finally, as proof of principle, VFM was applied to IOP-induced ONH deformation data (obtained from one subject's eye imaged with OCT), and the biomechanical properties of the prelamina and lamina cribrosa (LC) were extracted. From given ONH displacements, VFM successfully matched back the biomechanical properties of ONH tissues with high accuracy and efficiency. For all parameters, the percentage errors were less than 0.05%. Our method was insensitive to rigid body motions and was also able to recover the material parameters in the presence of noise. VFM was also found 125 times faster than the gold-standard IFEM. Finally, the estimated shear modulus for the prelamina and the LC of the studied subject's eye were 33.7 and 63.5 kPa, respectively. VFM may be capable of measuring the biomechanical properties of ONH tissues with high speed and accuracy. It has potential in identifying patient-specific ONH biomechanical properties in the clinic if combined with optical coherence tomography.

15 Article In Vivo 3-Dimensional Strain Mapping of the Optic Nerve Head Following Intraocular Pressure Lowering by Trabeculectomy. 2016

Girard, Michaël J A / Beotra, Meghna R / Chin, Khai Sing / Sandhu, Amanjeet / Clemo, Monica / Nikita, Eleni / Kamal, Deborah S / Papadopoulos, Maria / Mari, Jean Martial / Aung, Tin / Strouthidis, Nicholas G. ·Ophthalmic Engineering & Innovation Laboratory, Department of Biomedical Engineering, National University of Singapore, Singapore; Singapore Eye Research Institute, Singapore National Eye Centre, Singapore. Electronic address: mgirard@nus.edu.sg. · Ophthalmic Engineering & Innovation Laboratory, Department of Biomedical Engineering, National University of Singapore, Singapore. · NIHR Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom. · Université de la Polynésie française, Tahiti, French Polynesia. · Singapore Eye Research Institute, Singapore National Eye Centre, Singapore. · Singapore Eye Research Institute, Singapore National Eye Centre, Singapore; NIHR Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom; Discipline of Clinical Ophthalmology and Eye Health, University of Sydney, Sydney, NSW, Australia. ·Ophthalmology · Pubmed #26992836.

ABSTRACT: PURPOSE: To map the 3-dimensional (3D) strain of the optic nerve head (ONH) in vivo after intraocular pressure (IOP) lowering by trabeculectomy (TE) and to establish associations between ONH strain and retinal sensitivity. DESIGN: Observational case series. PARTICIPANTS: Nine patients with primary open-angle glaucoma (POAG) and 3 normal controls. METHODS: The ONHs of 9 subjects with POAG (pre-TE IOP: 25.3±13.9 mmHg; post-TE IOP: 11.8±8.6 mmHg) were imaged (1 eye per subject) using optical coherence tomography (OCT) (Heidelberg Spectralis, Heidelberg Engineering GmbH, Heidelberg, Germany) before (<21 days) and after (<50 days) TE. The imaging protocol was repeated for 3 controls in whom IOP was not altered. In each post-TE OCT volume, 4 tissues were manually segmented (prelamina, choroid, sclera, and lamina cribrosa [LC]). For each ONH, a 3D tracking algorithm was applied to both post- and pre-TE OCT volumes to extract IOP-induced 3D displacements at segmented nodes. Displacements were filtered, smoothed, and processed to extract 3D strain relief (the amount of tissue deformation relieved after TE). Strain relief was compared with measures of retinal sensitivity from visual field testing. MAIN OUTCOME MEASURES: Three-dimensional ONH displacements and strain relief. RESULTS: On average, strain relief (averaged or effective component) in the glaucoma ONHs (8.6%) due to TE was higher than that measured in the normal controls (1.07%). We found no associations between the magnitude of IOP decrease and the LC strain relief (P > 0.05), suggesting biomechanical variability across subjects. The LC displaced posteriorly, anteriorly, or not at all. Furthermore, we found linear associations between retinal sensitivity and LC effective strain relief (P < 0.001; high strain relief associated with low retinal sensitivity). CONCLUSIONS: We demonstrate that ONH displacements and strains can be measured in vivo and that TE can relieve ONH strains. Our data suggest a wide variability in ONH biomechanics in the subjects examined in this study. We further demonstrate associations between LC effective strain relief and retinal sensitivity.

16 Article Trabeculectomy for normal tension glaucoma: outcomes using the Moorfields Safer Surgery technique. 2016

Jayaram, Hari / Strouthidis, Nicholas G / Kamal, Deborah S. ·Glaucoma Service, Moorfields Eye Hospital, London, UK NIHR Biomedical Research Centre for Ophthalmology, UCL Institute of Ophthalmology & Moorfields Eye Hospital, London, UK Casey Eye Institute, Portland, Oregon, USA. · Glaucoma Service, Moorfields Eye Hospital, London, UK NIHR Biomedical Research Centre for Ophthalmology, UCL Institute of Ophthalmology & Moorfields Eye Hospital, London, UK Singapore Eye Research Institute, Singapore, Singapore Discipline of Clinical Ophthalmology and Eye Health, University of Sydney, Sydney, New South Wales, Australia. · Glaucoma Service, Moorfields Eye Hospital, London, UK. ·Br J Ophthalmol · Pubmed #26198279.

ABSTRACT: AIMS: To evaluate long-term outcomes and complications of trabeculectomy for normal tension glaucoma (NTG) with contemporary surgical techniques. METHODS: Retrospective consecutive, non-comparative case series of 131 eyes of 98 patients undergoing trabeculectomy between 2007 and 2013 in a dedicated NTG clinic. Data collected during routine clinical care were analysed. Assessment of clinical outcomes included intraocular pressure (IOP) reduction, bleb function, final visual acuity, evidence of glaucoma progression, postoperative complications and further surgical intervention. Surgical failure was defined as a failure to meet specified IOP-related criteria, the need to undergo further glaucoma surgery for raised IOP or loss of light perception vision. A further analysis was also performed which considered failure as glaucoma progression following surgery. Outcomes were evaluated using Kaplan-Meier life-table analysis. RESULTS: The cumulative percentages of unqualified success as defined by a ≥30% reduction of IOP from baseline preoperative maximum (95% CI; IOP of all eyes: mean±SD) at 1, 2, 3 and 4 years after surgery were 91.1% (84.1% to 95.1%; 9.7±2.9 mm Hg), 74.1% (63.7% to 81.8%; 10.3±3.0 mm Hg), 64.8% (52.7% to 74.6%; 10.6±2.5 mm Hg) and 62.1% (49.3% to 72.6%; 10.2±2.1 mm Hg), respectively. At 2 years of follow-up there was no significant association between either previous cataract surgery or ethnicity and failure. Cumulative percentages of unqualified success at 4 years after surgery as defined by a filtering trabeculectomy bleb or absence of glaucoma progression were 91.6% (83.2% to 95.9%) and 92.3% (81.3% to 97.0%), respectively. Postoperative complications such as early (2.3%) and late (0.8%) hypotony were significantly lower than suggested by the current literature. CONCLUSIONS: Trabeculectomy in NTG patients undertaken using contemporary surgical techniques and intensive postoperative management is associated with more successful long-term outcomes and fewer complications than the currently available literature suggests.

17 Article Retinal and optic nerve changes in glaucoma: From animal study to clinical implication. 2015

Chew, Shenton S L / Martins, Alessandra / Strouthidis, Nicholas. ·NIHR Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK. · Discipline of Clinical Ophthalmology and Eye Health, University of Sydney, Sydney, NSW, Australia; Sydney Eye Hospital, Sydney, NSW, Australia. · NIHR Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK; Discipline of Clinical Ophthalmology and Eye Health, University of Sydney, Sydney, NSW, Australia; Singapore Eye Research Institute, Singapore, Singapore. Electronic address: nick.strouthidis@moorfields.nhs.uk. ·Prog Brain Res · Pubmed #26497790.

ABSTRACT: Animal models of experimental glaucoma provide the ability to longitudinally characterize changes in the optic nerve head and surrounding retinal nerve fiber layer with various imaging modalities and compare them to histomorphometric changes. Analysis of the optic nerve head surface by confocal scanning laser tomography and structures deep to this by spectral domain optical coherence tomography allow for the detection of the earliest structural changes seen in glaucoma. Algorithms utilizing these parameters along with retinal nerve fiber layer measurement are likely to play an important role in the future of glaucoma progression monitoring.

18 Article Measures of socioeconomic status and self-reported glaucoma in the U.K. Biobank cohort. 2015

Shweikh, Y / Ko, F / Chan, M P Y / Patel, P J / Muthy, Z / Khaw, P T / Yip, J / Strouthidis, N / Foster, P J / Anonymous6880840. ·Division of Genetics and Epidemiology, NIHR Biomedical Research Centre, Moorfields Eye Hospital and UCL Institute of Ophthalmology, London, UK. · Department of Public Health and Primary Care, University of Cambridge, Cambridge, UK. · Singapore Eye Research Institute, Singapore, Singapore. · Discipline of Clinical Ophthalmology and Eye Health, University of Sydney, Sydney, NSW, Australia. ·Eye (Lond) · Pubmed #26315700.

ABSTRACT: PURPOSE: To determine ocular, demographic, and socioeconomic associations with self-reported glaucoma in the U.K. Biobank. METHODS: Biobank is a study of U.K. residents aged 40-69 years registered with the National Health Service. Data were collected on visual acuity, intraocular pressure (IOP), corneal biomechanics, and questionnaire from 112,690 participants. Relationships between ocular, demographic, and socioeconomic variables with reported diagnosis of glaucoma were examined. RESULTS: In all, 1916 (1.7%) people in U.K. Biobank reported glaucoma diagnosis. Participants reporting glaucoma were more likely to be older (mean 61.4 vs. 56.7 years, P<0.001) and male (2.1% vs. 1.4%, P=0.001). The rate of reported glaucoma was significantly higher in Black (3.28%, P<0.001) and Asian (2.14%, P=0.009) participants compared with White participants (1.62%, reference). Cases of reported glaucoma had a higher mean IOP (18 mm Hg both eyes, P<0.001), lower corneal hysteresis (9.96 right eye, 9.89 left eye, P<0.001), and lower visual acuity (0.09 logMAR right eye, 0.08 logMAR left eye, P<0.001) compared with those without (16 mm Hg both eyes, hysteresis 10.67 right eye, 10.63 left eye, 0.03 logMAR right eye, 0.02 logMAR left eye). The mean Townsend deprivation index was -0.72 for those reporting glaucoma and -0.95 for those without (P<0.001), indicating greater relative deprivation in those reporting glaucoma. Multivariable logistic regression showed that people in the lowest income group (<£18,000/year) were significantly more likely to report a diagnosis of glaucoma compared with any other income level (P<0.01). We observed increasing glaucoma risk across the full range of income categories, with highest risk among those of lowest income, and no evidence of a threshold effect. CONCLUSIONS: In a large U.K. cohort, individuals reporting glaucoma had more adverse socioeconomic characteristics. Study of the mechanisms explaining these effects may aid our understanding of health inequality and will help inform public health interventions.

19 Article Long-Term Outcomes of Trabeculectomy Augmented with Mitomycin C Undertaken within the First 2 Years of Life. 2015

Jayaram, Hari / Scawn, Richard / Pooley, Francisco / Chiang, Mark / Bunce, Catey / Strouthidis, Nicholas G / Khaw, Peng Tee / Papadopoulos, Maria. ·Glaucoma Service, Moorfields Eye Hospital, London, United Kingdom; National Institute of Health Research Biomedical Research Centre for Ophthalmology, University College London Institute of Ophthalmology and Moorfields Eye Hospital, London, United Kingdom; Casey Eye Institute, Oregon Health & Science University, Portland, Oregon. · Glaucoma Service, Moorfields Eye Hospital, London, United Kingdom. · Glaucoma Service, Moorfields Eye Hospital, London, United Kingdom; Glaucoma Department, Fundación Oftalmológica Los Andes, Santiago, Chile. · Glaucoma Service, Moorfields Eye Hospital, London, United Kingdom; National Institute of Health Research Biomedical Research Centre for Ophthalmology, University College London Institute of Ophthalmology and Moorfields Eye Hospital, London, United Kingdom; Glaucoma Department, Queensland Eye Institute and City Eye Centre, Brisbane, Australia. · National Institute of Health Research Biomedical Research Centre for Ophthalmology, University College London Institute of Ophthalmology and Moorfields Eye Hospital, London, United Kingdom; London School of Hygiene & Tropical Medicine, London, United Kingdom. · Glaucoma Service, Moorfields Eye Hospital, London, United Kingdom; National Institute of Health Research Biomedical Research Centre for Ophthalmology, University College London Institute of Ophthalmology and Moorfields Eye Hospital, London, United Kingdom; Singapore Eye Research Institute, Singapore, Republic of Singapore; Discipline of Clinical Ophthalmology and Eye Health, University of Sydney, Sydney, Australia. · Glaucoma Service, Moorfields Eye Hospital, London, United Kingdom; National Institute of Health Research Biomedical Research Centre for Ophthalmology, University College London Institute of Ophthalmology and Moorfields Eye Hospital, London, United Kingdom. · Glaucoma Service, Moorfields Eye Hospital, London, United Kingdom; National Institute of Health Research Biomedical Research Centre for Ophthalmology, University College London Institute of Ophthalmology and Moorfields Eye Hospital, London, United Kingdom. Electronic address: maria.papadopoulos@moorfields.nhs.uk. ·Ophthalmology · Pubmed #26315044.

ABSTRACT: PURPOSE: To evaluate the long-term effectiveness and safety of mitomycin C (MMC)-augmented trabeculectomy undertaken within the first 2 years of life for the surgical management of glaucoma. DESIGN: Retrospective, consecutive, noncomparative case series. PARTICIPANTS: All children who underwent MMC-augmented trabeculectomy within 2 years of birth between May 2002 and November 2012. METHODS: The medical records of 40 consecutive eyes of 26 children who underwent surgery by a single surgeon were reviewed. Data collected during routine clinical care were analyzed. MAIN OUTCOME MEASURES: Assessment of clinical outcomes included intraocular pressure (IOP), final visual acuity, bleb morphology, surgical complications (early and late), postoperative interventions, and further glaucoma surgery performed. Surgical success was defined as final IOP of 5 mmHg or more and of 21 mmHg or less, with anti-glaucoma medications (qualified success) and without (complete success), stable ocular dimensions and optic disc cupping, and no further glaucoma surgery (including needling) or loss of light perception. Surgical outcomes were evaluated using Kaplan-Meier life table analysis. RESULTS: Forty eyes of 26 children were studied over a mean follow-up period of 62.8 months. Most cases (80%) were of primary congenital glaucoma after failed goniotomy surgery. Cumulative probabilities of survival at 1, 5, and 7 years were 78%, 67%, and 60%, respectively. Of eyes regarded as successful, 96% (25/26 eyes) had controlled IOP without topical medication and 44% achieved visual acuity of 20/40 or better. In only 1 of the 40 eyes did a cystic avascular bleb develop, with all the other eyes being non-cystic in nature (diffuse and elevated or flat) at final follow-up. Sixty-four percent (9/14 eyes) of cases regarded as failures ultimately underwent glaucoma drainage device implantation. CONCLUSIONS: A contemporary pediatric trabeculectomy technique augmented with MMC is an effective procedure in the management of glaucoma within the first 2 years of life, as shown by the successful long-term outcomes and low incidence of sight-threatening complications. Trabeculectomy after failed goniotomy surgery or as a primary surgical intervention may offer a phakic infant with glaucoma an excellent opportunity to achieve long-term control of IOP without medications and may be associated with optimal visual outcomes.

20 Article A Global Shape Index to Characterize Anterior Lamina Cribrosa Morphology and Its Determinants in Healthy Indian Eyes. 2015

Thakku, Sri Gowtham / Tham, Yih-Chung / Baskaran, Mani / Mari, Jean-Martial / Strouthidis, Nicholas G / Aung, Tin / Cheng, Ching-Yu / Girard, Michael J A. ·Singapore Eye Research Institute, Singapore National Eye Centre, Singapore. · Singapore Eye Research Institute, Singapore National Eye Centre, Singapore 2Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore. · Singapore Eye Research Institute, Singapore National Eye Centre, Singapore 2Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 3Duke-National University of Singapore Graduate Medical School, Singapore. · University of French Polynesia, Tahiti, French Polynesia. · Singapore Eye Research Institute, Singapore National Eye Centre, Singapore 5National Institute for Health Research Biomedical Research Centre, Moorfields Eye Hospital National Health Service Foundation Trust & University College London Institute of Ophtha. · Singapore Eye Research Institute, Singapore National Eye Centre, Singapore 7Department of Biomedical Engineering, National University of Singapore, Singapore. ·Invest Ophthalmol Vis Sci · Pubmed #26047047.

ABSTRACT: PURPOSE: Lamina cribrosa (LC) morphology could be implicated in the progression of glaucoma. To date, no established, quantifiable parameter to assess LC shape in vivo exists. We aim to introduce a new global shape index for the anterior LC (LC-GSI) and to identify associations with ocular factors in a healthy Indian population. METHODS: Optical coherence tomography (OCT) scans of the optic nerve head (ONH) were performed on 162 healthy subjects. Optic nerve head structures were delineated and a geometric characterization of anterior LC morphology was obtained by measuring curvature along 180 LC cross sections and representing it as LC-GSI ranging from -1 to +1. Lamina cribrosa depth and curvature were also reported. Linear regression was used to identify factors associated with LC morphology. RESULTS: The typical healthy LC had a saddle rut-like appearance, with a central ridge visible in superior-inferior cross sections. A more prominent central ridge (larger LC-GSI) was associated with shorter axial length (P < 0.001), smaller Bruch's membrane opening (BMO) area (P = 0.020), smaller vertical cup-to-disc ratio (VCDR) (P = 0.007), and larger minimum rim width (BMO-MRW) (P = 0.001). A deeper LC was associated with male sex (P < 0.001), shorter axial length (P = 0.003), larger VCDR (P < 0.001), and smaller BMO-MRW (P = 0.002). Age and IOP were not significantly associated with LC morphology in healthy eyes. CONCLUSIONS: The LC-GSI is a single index that quantifies overall LC shape in an intuitive way. Ocular determinants of LC-GSI in healthy eyes included risk factors for glaucoma (axial length, VCDR, and BMO-MRW), highlighting the potential role of LC morphological characterization in the diagnosis and monitoring of glaucoma.

21 Article Lamina cribrosa visibility using optical coherence tomography: comparison of devices and effects of image enhancement techniques. 2015

Girard, Michaël J A / Tun, Tin A / Husain, Rahat / Acharyya, Sanchalika / Haaland, Benjamin A / Wei, Xin / Mari, Jean M / Perera, Shamira A / Baskaran, Mani / Aung, Tin / Strouthidis, Nicholas G. ·In Vivo Biomechanics Laboratory, Department of Biomedical Engineering, National University of Singapore, Singapore Singapore Eye Research Institute, Singapore National Eye Centre, Singapore. · Singapore Eye Research Institute, Singapore National Eye Centre, Singapore. · Centre for Quantitative Medicine, Duke-NUS Graduate Medical School, Singapore. · Centre for Quantitative Medicine, Duke-NUS Graduate Medical School, Singapore Department of Statistics and Applied Probability, National University of Singapore, Singapore. · Singapore Eye Research Institute, Singapore National Eye Centre, Singapore Centre for Quantitative Medicine, Duke-NUS Graduate Medical School, Singapore. · Department of Medical Physics and Bioengineering, UCL, London, United Kingdom. · Singapore Eye Research Institute, Singapore National Eye Centre, Singapore Centre for Quantitative Medicine, Duke-NUS Graduate Medical School, Singapore Yong Loo Lin School of Medicine, National University of Singapore, Singapore. · Singapore Eye Research Institute, Singapore National Eye Centre, Singapore NIHR Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom Discipline of Clinical Ophthalmology and Eye Health, University of Sydney, Sydney, New South Wales, Australia. ·Invest Ophthalmol Vis Sci · Pubmed #25593025.

ABSTRACT: PURPOSE: To compare the visibility of the lamina cribrosa (LC) in optic disc images acquired from 60 glaucoma and 60 control subjects using three optical coherence tomography (OCT) devices, with and without enhanced depth imaging (EDI) and adaptive compensation (AC). METHODS: A horizontal B-scan was acquired through the center of the disc using two spectral-domain (Spectralis and Cirrus; with and without EDI) and a swept-source (DRI) OCT. Adaptive compensation was applied post acquisition to improve image quality. To assess LC visibility, four masked observers graded the 1200 images in a randomized sequence. The anterior LC was graded from 0 to 4, the LC insertions from 0 to 2, and the posterior LC either 0 or 1. The effect of EDI, AC, glaucoma severity, and other clinical/demographic factors on LC visibility was assessed using generalized estimating equations. RESULTS: The anterior LC was the most detectable feature, followed by the LC insertions. Adaptive compensation improved anterior LC visibility independent of EDI. Cirrus+EDI+AC generated the greatest anterior LC visibility grades (2.79/4). For LC insertions visibility, DRI+AC was the best method (1.10/2). Visibility of the posterior LC was consistently poor. Neither glaucoma severity nor clinical/demographic factors consistently affected LC visibility. CONCLUSIONS: Adaptive compensation is superior to EDI in improving LC visibility. Visibility of the posterior LC remains poor suggesting impracticality in using LC thickness as a glaucoma biomarker.

22 Article Age-related differences in longitudinal structural change by spectral-domain optical coherence tomography in early experimental glaucoma. 2014

Yang, Hongli / He, Lin / Gardiner, Stuart K / Reynaud, Juan / Williams, Galen / Hardin, Christy / Strouthidis, Nicholas G / Downs, J Crawford / Fortune, Brad / Burgoyne, Claude F. ·Optic Nerve Head Research Laboratory, Devers Eye Institute, Legacy Health, Portland, Oregon, United States Discoveries in Sight Research Laboratories of the Devers Eye Institute, Legacy Health, Portland, Oregon, United States. · Discoveries in Sight Research Laboratories of the Devers Eye Institute, Legacy Health, Portland, Oregon, United States. · National Institute for Health Research Biomedical Research Centre at Moorfields Eye Hospital National Health Service Foundation Trust and University College London Institute of Ophthalmology, London, United Kingdom. · Ocular Biomechanics and Biotransport Program, University of Alabama at Birmingham School of Medicine, Birmingham, Alabama, United States. ·Invest Ophthalmol Vis Sci · Pubmed #25190652.

ABSTRACT: PURPOSE: To characterize age-related differences in the magnitude of spectral-domain optical coherence tomography (SD-OCT) structural change in early experimental glaucoma (EG). METHODS: Both eyes from four young (1.4-2.6 years) and four old (18.6-21.9 years) rhesus monkeys were imaged at least three times at baseline, and then every 2 weeks after laser-induced, chronic, unilateral IOP elevation until the onset of EG (confocal scanning laser tomographic surface change confirmed twice). Two to 20 weeks after EG onset, animals were euthanized and optic nerve axon counts for all eyes were performed. Masked operators delineated retinal and ONH landmarks in 40 radial B-scans from each eye and imaging session to quantify change from baseline in five SD-OCT neural and connective tissue parameters. The effects of EG, age, and EG × age interactions on the magnitude, rate (magnitude per postlaser time), and IOP responsiveness (magnitude per cumulative IOP insult) of postlaser parameter change were individually assessed using general estimating equation models. RESULTS: Presac SD-OCT RNFLT and minimum rim width change and postmortem axon loss was not significantly different in old compared with young EG eyes. The rate of change and IOP responsiveness of the parameters anterior lamina cribrosa surface depth relative to Bruch's membrane opening (BMO) and BMO depth relative to peripheral Bruch's membrane were significantly lower (P < 0.05) in the old compared with the young EG eyes. CONCLUSIONS: At similar postlaser times, levels of cumulative IOP insult and axonal damage, SD-OCT-detected ONH connective tissue structural change is greater in young compared with old monkey EG eyes.

23 Article Longitudinal detection of optic nerve head changes by spectral domain optical coherence tomography in early experimental glaucoma. 2014

He, Lin / Yang, Hongli / Gardiner, Stuart K / Williams, Galen / Hardin, Christy / Strouthidis, Nicholas G / Fortune, Brad / Burgoyne, Claude F. ·Optic Nerve Head Research Laboratory, Devers Eye Institute, Legacy Health, Portland, Oregon. ·Invest Ophthalmol Vis Sci · Pubmed #24255047.

ABSTRACT: PURPOSE: We determined if the detection of spectral-domain optical coherence tomography (SDOCT) optic nerve head (ONH) change precedes the detection of confocal scanning laser tomography (CSLT) ONH surface, SDOCT retinal nerve fiber layer (RNFL), scanning laser perimetry (SLP), and multifocal electroretinography (mfERG) change in eight experimental glaucoma (EG) eyes. METHODS: Both eyes from eight monkeys were tested at least three times at baseline, and then every 2 weeks following laser-induced chronic unilateral IOP elevation. Event and trend-based definitions of onset in the control and EG eyes for 11 SDOCT neural and connective tissue, CSLT surface, SDOCT RNFL, SLP, and mfERG parameters were explored. The frequency and timing of onset for each parameter were compared using a logrank test. RESULTS: Maximum post-laser IOP was 18 to 42 mm Hg in the EG eyes and 12 to 20 mm Hg in the control eyes. For event- and trend-based analyses, onsets were achieved earliest and most frequently within the ONH neural and connective tissues using SDOCT, and at the ONH surface using CSLT. SDOCT ONH neural and connective tissue parameter change preceded or coincided with CSLT ONH surface change in most EG eyes. The SDOCT and SLP measures of RNFL thickness, and mfERG measures of visual function demonstrated similar onset rates, but occurred later than SDOCT ONH and CSLT surface change, and in fewer eyes. CONCLUSIONS: SDOCT ONH change detection commonly precedes or coincides with CSLT ONH surface change detection, and consistently precedes RNFLT, SLP, and mfERG change detection in monkey experimental glaucoma.

24 Article Relationship between ganglion cell-inner plexiform layer and optic disc/retinal nerve fibre layer parameters in non-glaucomatous eyes. 2013

Tham, Yih-Chung / Cheung, Carol Y / Koh, Victor T / Cheng, Ching-Yu / Sidhartha, Elizabeth / Strouthidis, Nicholas G / Wong, Tien Y / Aung, Tin. ·Singapore Eye Research Institute, Singapore National Eye Centre, , Singapore, Singapore. ·Br J Ophthalmol · Pubmed #24123901.

ABSTRACT: AIMS: To determine the relationship between macular ganglion cell-inner plexiform layer (GC-IPL) thickness and optic disc/retinal nerve fibre layer (RNFL) parameters in non-glaucomatous eyes measured by spectral-domain optical coherence tomography (SD-OCT). METHODS: 491 non-glaucomatous Chinese aged 40-80 years were recruited from a population-based study and underwent standardised ophthalmic examination. SD-OCT was used to measure GC-IPL thickness, optic disc parameters and RNFL thickness. Univariate and multiple linear regression analyses were performed to assess the association between GC-IPL and optic disc/RNFL parameters. RESULTS: In univariate analyses, all RNFL parameters and rim area were significantly correlated with all macular GC-IPL parameters (p<0.001, r=0.12-0.56). In multiple regression analyses, after adjusting for age, gender, disc area, signal strength and axial length, average RNFL thickness (per µm decrease) was most strongly correlated with average GC-IPL thickness (β=-0.30, standardised β=-0.499, p<0.001) compared with other optic disc/RNFL parameters. CONCLUSIONS: Our study demonstrated only fair correlations between macular GC-IPL and optic disc/RNFL parameters measured by SD-OCT. This information is important for further evaluation of macular GC-IPL thickness as an additional marker in detecting glaucomatous damage and progression.

25 Article In vivo optic nerve head biomechanics: performance testing of a three-dimensional tracking algorithm. 2013

Girard, Michaël J A / Strouthidis, Nicholas G / Desjardins, Adrien / Mari, Jean Martial / Ethier, C Ross. ·Department of Bioengineering, National University of Singapore, Singapore, Republic of Singapore. mgirard@invivobiomechanics.com ·J R Soc Interface · Pubmed #23883953.

ABSTRACT: Measurement of optic nerve head (ONH) deformations could be useful in the clinical management of glaucoma. Here, we propose a novel three-dimensional tissue-tracking algorithm designed to be used in vivo. We carry out preliminary verification of the algorithm by testing its accuracy and its robustness. An algorithm based on digital volume correlation was developed to extract ONH tissue displacements from two optical coherence tomography (OCT) volumes of the ONH (undeformed and deformed). The algorithm was tested by applying artificial deformations to a baseline OCT scan while manipulating speckle noise, illumination and contrast enhancement. Tissue deformations determined by our algorithm were compared with the known (imposed) values. Errors in displacement magnitude, orientation and strain decreased with signal averaging and were 0.15 µm, 0.15° and 0.0019, respectively (for optimized algorithm parameters). Previous computational work suggests that these errors are acceptable to provide in vivo characterization of ONH biomechanics. Our algorithm is robust to OCT speckle noise as well as to changes in illumination conditions, and increasing signal averaging can produce better results. This algorithm has potential be used to quantify ONH three-dimensional strains in vivo, of benefit in the diagnosis and identification of risk factors in glaucoma.

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