Interest In Glaucoma Research Articles

Defining stable glaucoma: a Delphi consensus survey of UK optometrists with a specialist interest in Glaucoma.

Increasing demand on hospital services has led to the development of alternative community-based services, often run by optometrists for monitoring 'stable' and low-risk glaucoma patients. An online Delphi exercise was undertaken to derive a consensus definition of 'stable glaucoma' amongst optometrists with a special interest in glaucoma. Participants were asked to score their agreement for various clinical parameters. Results from each round were used to inform subsequent rounds. 31 optometrists participated in the study. 100%, 77%, and 68% completion rates were achieved over three rounds respectively. Consensus was reached for 7 parameters: Stability should be defined over a period of 36-48 months, summary measure Visual Field (VF), and/or Trend Analysis should be used to assess VF stability. Two or more decibel (dB) of change of VF mean deviation (MD) is considered unstable. Intraocular pressure (IOP) should be below a target defined by the patient's clinician or a fixed-percentage reduction compared to the presenting IOP. No treatment change during the stability assessment period is considered stable. Imaging with Ocular Coherence Topography Retinal Nerve Fibre Layer (OCT RNFL) assessment should be used to define glaucoma stability. Overview by a glaucoma consultant was considered important for glaucoma monitoring schemes. This Delphi exercise has generated a consensus definition for glaucoma stability by UK Optometrists with a specialist interest in glaucoma. This consensus definition can be used to inform the selection of suitable patients from hospital services for transfer to monitoring in community-based 'stable' optometry run glaucoma clinics.

Developing standards for the development of glaucoma virtual clinics using a modified Delphi approach

PurposeTo obtain consensus opinion for the development of a standards framework for the development and implementation of virtual clinics for glaucoma monitoring in the UK using a modified Delphi methodology.MethodsA...

The Capacity of Eye Care Services for Patients with Glaucoma in Botswana

ABSTRACTPurpose: To evaluate current delivery of glaucoma care in Botswana; in particular, the service infrastructure available and glaucoma-related workload.Methods: A multi-center cross-sectional study was undertaken comprising government eye care institutions and ophthalmic personnel across Botswana. Data on human resources, equipment types and numbers, diagnostic criteria routinely used, treatments routinely provided, and new and repeat glaucoma consultations were obtained through quantitative and qualitative surveys.Results: In 27 government eye care institutions there were two general ophthalmologists, neither of whom had a subspecialty interest in glaucoma, 64 ophthalmic nurses, two optometrists, one low vision therapist, one refractionist, and two equipment technicians. Only 8.5% of available ophthalmic human resources were taken up with provision of glaucoma care. About 1/3 of hospitals did not have tonometers, most primary hospitals lacked slit lamp biomicroscopes and most hospitals lacked sensitive diagnostic equipment. A diagnosis of glaucoma was made by either an ophthalmic nurse or an ophthalmologist, but only 10% of institutions could meet recommendations for follow-up assessment. Topical glaucoma medications were prescribed by almost all hospital clinics, usually by ophthalmic nurses. Drug choices were largely determined by local availability. Glaucoma surgery accounted for 0.8% of total eye operations. Glaucoma patients took up 8.5% of total clinic visits. The total number of glaucoma visits was highest in the two hospitals with ophthalmologists. New glaucoma cases took up 10.3% of total glaucoma visits.Conclusion: This study highlights the challenges faced in caring for glaucoma patients in Botswana; in particular, lack of professional human resources, equipment and availability of effective treatments.

Glaucoma-related Changes in the Mechanical Properties and Collagen Micro-architecture of the Human Sclera.

ObjectiveThe biomechanical behavior of the sclera determines the level of mechanical insult from intraocular pressure to the axons and tissues of the optic nerve head, as is of interest in glaucoma. In this study, we measure the collagen fiber structure and the strain response, and estimate the material properties of glaucomatous and normal human donor scleras.MethodsTwenty-two posterior scleras from normal and diagnosed glaucoma donors were obtained from an eyebank. Optic nerve cross-sections were graded to determine the presence of axon loss. The specimens were subjected to pressure-controlled inflation testing. Full-field displacement maps were measured by digital image correlation (DIC) and spatially differentiated to compute surface strains. Maps of the collagen fiber structure across the posterior sclera of each inflated specimen were obtained using synchrotron wide-angle X-ray scattering (WAXS). Finite element (FE) models of the posterior scleras, incorporating a specimen-specific representation of the collagen structure, were constructed from the DIC-measured geometry. An inverse finite element analysis was developed to estimate the stiffness of the collagen fiber and inter-fiber matrix.ResultsThe differences between glaucoma and non-glaucoma eyes were small in magnitude. Sectorial variations of degree of fiber alignment and peripapillary scleral strain significantly differed between normal and diagnosed glaucoma specimens. Meridional strains were on average larger in diagnosed glaucoma eyes compared with normal specimens. Non-glaucoma specimens had on average the lowest matrix and fiber stiffness, followed by undamaged glaucoma eyes, and damaged glaucoma eyes but the differences in stiffness were not significant.ConclusionThe observed biomechanical and microstructural changes could be the result of tissue remodeling occuring in glaucoma and are likely to alter the mechanical environment of the optic nerve head and contribute to axonal damage.

MicroRNAs that target RGS5.

An earlier meta-analysis on gene expression data derived from four microarray, two cDNA library, and one SAGE experiment had identified RGS5 as one of only ten non-housekeeping genes that were reported to be expressed in human trabecular meshwork (TM) cells by all studies. RGS5 encodes regulator of G-protein signaling-5. The TM tissue is the route of aqueous fluid outflow, and is relevant to the pathology of glaucoma. MicroRNAs constitute the most recently identified components of the cellular machinery for gene regulation in eukaryotic cells. Given our long standing interest in glaucoma, we aimed to identify miRNAs that may target RGS5. Eight miRNAs were selected for study using bioinformatics tools and available data on miRNAs expressed in the eye. Their effects were assessed using the dual luciferase assay. 3'-UTR segments of RGS5 mRNA were cloned downstream of a luciferase coding gene in psiCHECK2 vectors, and these were co-transfected with each of the miRNAs into HEK293 cells. The outcomes evidenced that one or more of the segments are in fact targeted by miR-7, miR-9, miR-96, miR-23a, miR-23b, miR-204, and miR-211. Down regulations by the miRNAs were statistically significant. The effect of miR-204 is considered particularly important as this miRNA is well known to regulate eye development and to affect multiple ocular functions. Our results justify further studies on regulation of RGS5 expression and RGS5 downstream functions by these miRNAs.

Cambridge community Optometry Glaucoma Scheme

With a higher life expectancy, there is an increased demand for hospital glaucoma services in the United Kingdom. The Cambridge community Optometry Glaucoma Scheme (COGS) was initiated in 2010, where new referrals for suspected glaucoma are evaluated by community optometrists with a special interest in glaucoma, with virtual electronic review and validation by a consultant ophthalmologist with special interest in glaucoma. 1733 patients were evaluated by this scheme between 2010 and 2013. Clinical assessment is performed by the optometrist at a remote site. Goldmann applanation tonometry, pachymetry, monoscopic colour optic disc photographs and automated Humphrey visual field testing are performed. A clinical decision is made as to whether a patient has glaucoma or is a suspect, and referred on or discharged as a false positive referral. The clinical findings, optic disc photographs and visual field test results are transmitted electronically for virtual review by a consultant ophthalmologist. The number of false positive referrals from initial referral into the scheme. Of the patients, 46.6% were discharged at assessment and a further 5.7% were discharged following virtual review. Of the patients initially discharged, 2.8% were recalled following virtual review. Following assessment at the hospital, a further 10.5% were discharged after a single visit. The COGS community-based glaucoma screening programme is a safe and effective way of evaluating glaucoma referrals in the community and reducing false-positive referrals for glaucoma into the hospital system.

The effectiveness of schemes that refine referrals between primary and secondary care—the UK experience with glaucoma referrals: the Health Innovation & Education Cluster (HIEC) Glaucoma Pathways Project

ObjectivesA comparison of glaucoma referral refinement schemes (GRRS) in the UK during a time period of considerable change in national policy and guidance.DesignRetrospective multisite review.SettingThe outcomes of clinical examinations by...

The impact of glaucoma referral refinement criteria on referral to, and first‐visit discharge rates from, the hospital eye service: the Health Innovation & Education Cluster (HIEC) Glaucoma Pathways project

To assess the impact of referral refinement criteria on the number of patients referred to, and first-visit discharges from, the Hospital Eye Service (HES) in relation to the National Institute for Health & Clinical Excellence (NICE) Glaucoma Guidelines, Joint College Group Guidance (JCG) and the NICE commissioning guidance. All low-risk (one risk factor: suspicious optic disc, abnormal visual field (VF), raised intra-ocular pressure (IOP) (22-28 mmHg) or IOP asymmetry (>5 mmHg) and high-risk (more than one risk factor, shallow anterior chamber or IOP >28 mmHg) referrals to the HES from 2006 to 2011 were analysed. Low-risk referrals were seen by Optometrists with a specialist interest in glaucoma and high-risk referrals were referred directly to the HES. Two thousand nine hundred and twelve patient records were analysed. The highest Consultant first-visit discharge rates were for referrals based on IOP alone (45% for IOP 22-28 mmHg) and IOP asymmetry (53%), VF defect alone (46%) and for abnormal IOP and VF (54%). The lowest first-visit discharge rates were for referrals for suspicious optic disc (19%) and IOP >28 mmHg (22%). 73% of patients aged 65-80 and 60% of patients aged >80 who were referred by the OSI due to an IOP between 22-28 mmHg would have satisfied the JCG criteria for non-referral. For patients referred with an IOP >28 mmHg and an otherwise normal examination, adherence to the NICE commissioning guidance would have resulted in 6% fewer referrals. In 2010 this scheme reduced the number of patients attending the HES by 15%, which resulted in a saving of £16 258 (13%). The results support that referrals for a raised IOP alone or in combination with an abnormal VF be classified as low-risk and undergo referral refinement. Adherence to the JCG and the NICE commissioning guidance as onward referral criteria for specialist optometrists in this referral refinement scheme would result in fewer referrals.

The effect of changes in referral behaviour following NICE guideline publication on agreement of examination findings between professionals in an established glaucoma referral refinement pathway: The Health Innovation & Education Cluster (HIEC) Glaucoma Pathways project

AimTo investigate whether the publication of the National Institute for Health and Clinical Excellence (NICE) glaucoma guidelines had an effect on the agreement of examination findings between professionals involved in...

Attitudes of consultant ophthalmologists in the UK to initial management of glaucoma patients presenting with severe visual field loss: a national survey

Recent National Institute of Clinical Excellence guidance suggests primary surgery should be offered to patients presenting with glaucoma with severe visual field loss. We undertook a survey of UK consultant ophthalmologists to determine if this represents current practice and explore attitudes towards managing patients with advanced glaucoma at presentation. Questionnaire evaluation study. All consultant ophthalmologists currently practicing in the UK. A single-page questionnaire was posted to all consultants (n = 910) currently practicing in the UK along with a pre-paid return envelope. A second questionnaire was sent to non-responders (n = 459). Questionnaire responses. 626 responses were received representing 68.8% of the population surveyed. 152 (24%) volunteered a specialist interest in glaucoma. Consensus opinion for both glaucoma specialists (64.9%) and non-glaucoma specialists (62.4%) was to start with primary medical therapy, most commonly citing surgical risk as the primary reason (23% and 22%, respectively) for this approach. Most felt the highest intraocular pressure measurement during follow up (measured in clinic) was the most important variable for prevention of further visual loss (60% of glaucoma specialists and 55% of non-glaucoma specialists). Eighty-three per cent of all responders suggested they would change their practice if evidence supporting primary surgery as a safe and more effective approach existed. Recent National Institute of Clinical Excellence guidance does not reflect the current management approach of UK ophthalmologists. The primary concern was related to potential complications of surgery although most practitioners would be willing to change their practice if evidence existed supporting primary surgery in patients presenting with advanced glaucoma.

A geometric morphometric assessment of the optic cup in glaucoma

The morphologic appearance of the optic disc is of interest in glaucoma. In contrast to descriptive classification systems that are currently used, a quantitative approach to the analysis of optic disc morphology is required. Our goal was to determine the optimal method for quantifying optic cup shape by comparing traditional (ovality, form-factor and neuroretinal rim (NRR) width ratio) and geometric morphometric approaches. Left optic disc stereophotographs of 160 (80 normal and 80 glaucomatous (stratified by severity)) subjects were examined. The optic cup margins were stereoscopically delineated with a custom tracing system and saved as a series of discrete points. The geometric morphometric methods of elliptic Fourier analysis (EFA) and sliding semi-landmark analysis (SSLA) were used to eliminate variation unrelated to shape (e.g. size) and yield a series of shape variables. Differences in optic cup shape between normal and glaucoma groups were investigated. Discriminant functions were computed and the sensitivity and specificity of each technique determined. Receiver operator characteristic (ROC) curves were calculated for all methods and evaluated in their potential to discriminate between normal and glaucomatous eyes based on the shape variables. All geometric morphometric methods revealed differences between normal and glaucomatous eyes in optic cup shape, in addition to the traditional parameters of ovality, form-factor and NRR width ratio ( p < 0.0005). SSLA (minimum bending energy criterion – 18 points) had the best sensitivity (83%) and area under the curve (AUC) (0.91). EFA (72 points) performed similarly well (74%, 0.89) as did the set of traditional shape-based variables (76%, 0.86). This study demonstrated that a geometric morphometric approach for discriminating between normal and glaucomatous eyes in optic cup shape is superior to that provided by traditional single parameter shape measures. Such analytical techniques could be incorporated into future automated optic disc screening modalities.

Development of a competency framework for optometrists with a specialist interest in glaucoma

To develop a competency framework, using a modified Delphi methodology, for optometrists with a specialist interest in glaucoma, which would provide a basis for training and accreditation. A modified iterative Delphi technique was used using a 16-member panel consisting almost exclusively of sub-specialist optometrists and ophthalmologists. The first round involved scoring the relevance of a draft series of competencies using a 9-point Likert scale with a free-text option to modify any competency or suggest additional competencies. The revised framework was subjected to a second round of scoring and free-text comment. The Delphi process was followed by a face-to-face structured workshop to debate and agree the final framework. The version of the framework agreed at the workshop was sent out for a 4-month period of external stakeholder validation. There was a 100% response to round 1 and an 94% response to round 2. All panel members attended the workshop. The final version of the competency framework was validated by a subsequent stakeholder consultation and contained 19 competencies for the diagnosis of glaucoma and 7 further competencies for monitoring and treatment. Application of a consensus methodology consisting of a modified Delphi technique allowed the development of a competency framework for glaucoma specialisation by optometrists. This will help to shape the development of a speciality curriculum and potentially could be adapted for other healthcare professionals.

Biaxial mechanical testing of human sclera

The biomechanical environment of the optic nerve head (ONH), of interest in glaucoma, is strongly affected by the biomechanical properties of sclera. However, there is a paucity of information about the variation of scleral mechanical properties within eyes and between individuals. We thus used biaxial testing to measure scleral stiffness in human eyes. Ten eyes from 5 human donors (age 55.4±3.5 years; mean±SD) were obtained within 24 h of death. Square scleral samples (6 mm on a side) were cut from each ocular quadrant 3–9 mm from the ONH centre and were mechanically tested using a biaxial extensional tissue tester (BioTester 5000, CellScale Biomaterials Testing, Waterloo). Stress–strain data in the latitudinal (toward the poles) and longitudinal (circumferential) directions, here referred to as directions 1 and 2, were fit to the four-parameter Fung constitutive equation W= c( e Q −1), where Q = c 1 E 11 2 + c 2 E 22 2 + 2 c 3 E 11 E 22 and W, c’s and E ij are the strain energy function, material parameters and Green strains, respectively. Fitted material parameters were compared between samples. The parameter c 3 ranged from 10 −7 to 10 −8, but did not contribute significantly to the accuracy of the fitting and was thus fixed at 10 −7. The products c⁎ c 1 and c⁎ c 2, measures of stiffness in the 1 and 2 directions, were 2.9±2.0 and 2.8±1.9 MPa, respectively, and were not significantly different (two-sided t-test; p=0.795). The level of anisotropy (ratio of stiffness in orthogonal directions) was 1.065±0.33. No statistically significant correlations between sample thickness and stiffness were found (correlation coefficients=−0.026 and −0.058 in directions 1 and 2, respectively). Human sclera showed heterogeneous, near-isotropic, nonlinear mechanical properties over the scale of our samples.

3D morphometry of the human optic nerve head

Human optic nerve head (ONH) anatomy is of interest in glaucoma. Our goal was to carry out a morphometric study of the human ONH based on 3D reconstructions from histologic sections. A set of 10 human ONHs (from four pairs of eyes plus two singles) were reconstructed in an iterative procedure that required the resulting geometries to satisfy a set of quality control criteria. Five models corresponded to eyes fixed at 5 mmHg and the other five models to eyes fixed at 50 mmHg. Several aspects of ONH morphology were measured based on surface and point landmarks: the thicknesses of the lamina cribrosa (LC), the peripapillary sclera and the pre-laminar neural tissue (peripapillary and within the cup); the minimum distance between the anterior surface of the LC and the subarachnoid space; the surface area of the anterior and posterior surfaces of the LC; and the diameter of the scleral canal opening. Our results showed that about one third of the anterior LC surface was obscured from view from the front by the sclera. In all eyes the LC inserted into the pia mater, and not only into the sclera. The variations in ONH morphology between eyes of a pair exceeded, or were of the same order as, changes in morphology due to acute changes in IOP. The reconstruction and morphometry techniques introduced are suitable for application to the ONH. Comparison of measurements in eyes fixed at different pressures suggested small effects on geometry of the increase in IOP. A large variability in ONH morphology, even between contralateral eyes of different IOP, was observed. We conclude that reconstruction of human ONH anatomy from 3D histology is possible, but that large inter-individual anatomic variations make morphometric analysis of the ONH very difficult in the absence of large sample numbers. The insertion of the pia mater into the LC may have biomechanical implications and should be further investigated. Emerging clinical imaging techniques such as deep-scanning OCT will be limited to investigation of the central and mid-peripheral regions of the LC due to optical “occluding” by the peripapillary sclera.

Can a community optometrist-based referral refinement scheme reduce false-positive glaucoma hospital referrals without compromising quality of care? The community and hospital allied network glaucoma evaluation scheme (CHANGES)

To describe the design, activity, and quality of the referral refinement phase of a novel glaucoma shared-care scheme. Eight Optometrists with a Specialist Interest in glaucoma (OSI) were trained to perform a community-based comprehensive glaucoma evaluation of low-risk glaucoma hospital referrals (only one/none of the following factors noted for either eye: abnormal optic disc, abnormal visual field, abnormal intraocular pressure (IOP; 22-28 mmHg or IOP asymmetry)) using equipment standardized to that of the hospital glaucoma service. One hundred and thirty-eight (27%) of a total of 512 glaucoma-related referrals were deemed 'low risk'. Their choice of OSI discharged 40 (35%). The consultant agreed (virtually) with the decision to discharge with 28 (70%) and disagreed with 12 (30%). Comparing findings between OSI and consultant for 99 referred patients, sensitivity, specificity, and negative predictive values for a suspicious optic disc were 78, 61, and 79%, respectively. For an IOP of >21 mmHg, they were 74, 85, and 90%, respectively. For an occludable anterior chamber angle (Van Herick's versus gonioscopy), they were 69, 88, and 94%, respectively. This referral refinement process can reduce numbers of false-positive referrals attending the hospital glaucoma service while retaining a relatively high level of examination quality.

The accuracy of accredited glaucoma optometrists in the diagnosis and treatment recommendation for glaucoma

Aim:To compare the diagnostic performance of accredited glaucoma optometrists (AGO) for both the diagnosis of glaucoma and the decision to treat with that of routine hospital eye care, against a...

Doppler-Sonographie bei Normaldruckglaukompatienten

Ocular hemodynamics is of great interest in glaucoma, especially since vascular disturbances may play a pathogenetic role in disease development. To investigate the hemodynamic differences between normal pressure glaucoma patients and normal volunteers, flow velocities of the retrobulbar vessels were measured by colour Doppler imaging. 15 patients with normal pressure glaucoma (NPG) and 15 healthy volunteers underwent colour Doppler imaging (CDI) of the retrobulbar vessels. The patients and the volunteers were especially gender- and age-matched. Peak systolic velocities (PSV), end-diastolic velocities (EDV), and resistive indices (RI) of the ophthalmic artery and central retinal artery were obtained. In NPG patients, PSV and EDV in the central retinal artery were significantly decreased, whereas RI was increased in central retinal artery and the ophthalmic artery. Colour Doppler imaging is a non-invasive technique that allows further estimation of the ocular circulatory status. Particularly in the group of patients with disturbed hemodynamics, like NPG patients, it was able to show a reduction of the retrobulbar hemodynamics.

Biomechanics of Schlemm's Canal Endothelial Cells: Influence on F-Actin Architecture

Aqueous humor drains from the eye through Schlemm's canal, a small endothelial-lined collecting duct. Schlemm's canal endothelial cells may be important in controlling the pressure within the eye (and hence are of interest in glaucoma), and are subject to an unusual combination of shear stress and a basal-to-apical pressure gradient. We sought to characterize this biomechanical environment and determine its effects on F-actin architecture in situ. A theoretical model of flow in Schlemm's canal was used to estimate shear stresses applied to endothelial cells by flowing aqueous humor. Alignment of Schlemm's canal endothelial cells in human eyes was quantified by scanning electron microscopy. F-actin architecture was visualized by fluorescent labeling and compared for closely adjacent cells exposed to different biomechanical environments. We found that, despite the relatively low flow rate of aqueous humor, shear stresses experienced by Schlemm's canal endothelial cells could reach those in the arterial system. Schlemm's canal endothelial cells showed a statistically significant preferential alignment, consistent with a shear-mediated effect. Schlemm's canal endothelial cells subjected to a basal-to-apical pressure gradient due to transendothelial flow showed a prominent marginal band of F-actin with relatively few cytoplasmic filaments. Adjacent cells not subject to this gradient showed little marginal F-actin, with a denser cytoplasmic random network. We conclude that Schlemm's canal endothelial cells experience physiologically significant levels of shear stress, promoting cell alignment. We speculate that this may help control the calibre of Schlemm's canal. F-actin distribution depends critically on the presence or absence of transendothelial flow and its associated pressure gradient. In the case of this pressure gradient, mechanical reinforcement around the cell periphery by F-actin seems to be critical.

Glaucoma Services in the Gambia

Objectives:To determine the existing glaucoma services at the three levels of eye care in The Gambia To highlight the problems with these services Methodology: Through observation, oral interviews examination of The Gambia's documented eye care plan, data on personnel and their role, diagnostic equipment, treatment and follow-up at the three levels of eye care were critically analysed. Results: Gonioscopy, perimetry and the surgical treatment of glaucoma are only performed at the tertiary centre where the ophthalmologists are based. The pro-blems with the existing glaucoma services in The Gambia ranged from lack of a structured programme to lack of regular ophthalmologists with an interest in glaucoma, as well as a limited supply and variety of antiglaucoma therapy. Conclusion: Preventive measures to reduce blindness from glaucoma in The Gambia are not part of the public health programme at present [Nig. J. Ophthalmology Vol.11(1) 2003: 19-23]

Ophthalmic Surgery: Principles and Practice

The editor has collaborated with 11 other surgeons to produce this excellent volume. As in any multiauthored book, the chapters are of varying quality. Some of the contributors have written magnificent chapters, while other contributions are rather sketchy. With the editor's interest in glaucoma, it is no surprise that the chapter on glaucoma is outstanding. Dr Spaeth has also written some chapters on principles and basic concepts, and these are worth reading for anybody who wants to do ophthalmic surgery. The chapters on cataract (George Weinstein) and the cornea (S. A. Boruchoff and G. N. Foulks) are outstanding. They present the problem in a concise and precise form and describe and evaluate the various surgical procedures. The chapter on plastic surgery (C. R. Leone) has excellent drawings that should help orient any young surgeon who would like to operate on the lids or the lacrimal apparatus. It is refreshing to