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Purpose: This study investigates the influence of peripheral corneal thickness (PCT) and its curvature on tonometry readings., Material and Methods: The study included 49 patients (49 eyes) who were indicated for glaucoma surgery. Using bidirectional applanation tonometry, the following parameters were obtained: IOPcc, IOPg - intraocular pressure (IOP) corrected for corneal compensation, taken as the most reliable indicator; IOP converted to Goldmann measurement, taken as the result of applanation tonometry, ΔIOP (IOPcc-IOPg), CH and CRF (corneal hysteresis and corneal resistance factor). During corneal topography, the corneal thickness was studied in the center, PCT at 1.5; 2, 3, 4 and 5 mm from the center in four meridians, as well as ΔPCT (PCT 3 mm - PCT 1.5 mm), the curvature of the anterior and posterior surfaces of the cornea and the depth of the anterior chamber. Aberrometry was used to obtain refractometry data and the curvature of the anterior surface of the cornea. The influence of the studied parameters on ΔIOP was evaluated., Results: ΔIOP correlated with CRF ( r = -0.652), CH ( r = -0.873), central corneal thickness ( r = -0.293), PCT at all distances except 5 mm ( r = -0.297; -0.287; -0.302; -0.303), with the strong and weak meridians of the anterior surface of the cornea ( r =0.328; r =0.315), with the strong and weak meridians of the posterior surface, as well as the average curvature of the posterior surface ( r =0.307; r =0.332; r =0.328). After step-by-step selection of the above parameters for creating a linear regression model for ΔIOP calculation, CH, CRF and PCT 1.5mm remained in the model. The model describes ΔIOP with high accuracy (R 2 =0.974)., Conclusion: Biomechanical parameters of the cornea are the leading factor of applanation tonometry error. Individual linear dimensions of the cornea (thickness, curvature) have a lesser effect.

Purpose: Eyelid spasms might be associated with elevated intraocular pressure (IOP) in hemifacial spasm (HFS) patients. IOP assessment using a Goldmann applanation tonometer (GAT) is often compromised by eyelid spasms. This study aimed to assess the effect of HFS on IOP measurements using the transpalpebral tonometer Diaton® before and after treatment with botulinum toxin type A (BTX-A) and compared Diaton® and GAT measurements after treatment with BTX-A., Methods: IOP measurements were obtained with Diaton® in 27 patients with moderate-to-severe HFS before and after treatment with BTX-A. After treatment, the IOP was also measured using GAT and the results were compared with the ones measured with a Diaton®. The patients underwent automated perimetry, OCT, and pachymetry for screening to glaucoma., Results: Mean IOP with Diaton® was 11 ± 3.42 mmHg before treatment in the affected eye and 9 ± 2.98 mmHg in the contralateral eye. This difference was statistically significant (P = 0.012). However, after treatment with BTX-A, no interocular difference was found in IOP obtained with Diaton® (P = 0.204) or GAT (P = 0.971). Comparison between GAT and Diaton® measurements showed no significant differences after BTX-A treatment between the affected (P = 0.212) and contralateral eye (P = 0.971)., Conclusions: A significant reduction in IOP measurements on the affected side of HFS patients was observed after treatment with BTX-A, demonstrating that eyelid spasms may increase the IOP. No significant difference was observed between Diaton® and GAT measurements after the application of BTX-A. No differences were found in automated perimetry, OCT, and CCT when comparing affected eyes with contralateral eyes., (© 2023. The Author(s), under exclusive licence to Springer Nature B.V.)

Background and Objective: The corneal biomechanical properties in naïve, untreated glaucoma and ocular hypertension (OHT) eyes is interesting, because it may be a source of error in intraocular pressure (IOP) measurements by Goldmann applanation tonometer (GAT) and Ocular Response Analyzer (ORA) The main objective of this study was to evaluate the IOP values obtained using GAT and the ORA, in primary open angle glaucoma (POAG) and in OHT untreated eyes., Material and Methods: Observational, masked, cross sectional observational study. Newly diagnosed, untreated POAG and OHT eyes were included., Results: 51 POAG and 34 OHT eyes were analyzed. We found that IOPcc (IOP corneal-compensated) was significantly higher than GAT IOP in POAG (p = 0.0002) while we did not find any significant difference between both tonometers in OHT (p = 0.1)., Conclusions: GAT seems to underestimate the real IOP in untreated POAG eyes and it seems to be quite accurate in OHT eyes., (Copyright © 2023 Sociedad Española de Oftalmología. Published by Elsevier España, S.L.U. All rights reserved.)

Glaucoma is the leading cause of irreversible blindness, affecting around 80 million people worldwide. Glaucoma is a multifactorial disease of poorly understood pathogenesis, with intraocular pressure being the most significant risk factor. Currently there are different methods of intraocular pressure measurement, based on different physical principles, some of which are continuous measurement methods and others which are only measured in the medical office. The importance of the corneal biomechanical properties in intraocular pressure measurement is becoming increasingly clear. With the development of new instruments that can measure them, it will become possible to obtain more accurate intraocular pressure measurements within a short period of time. In the future, glaucoma patients will be better monitored with instruments capable of measuring intraocular pressure 24 hours a day., (Copyright © 2022. Published by Elsevier Inc.)

Glaucoma is the second leading cause of blindness in India. Despite advances in diagnosing and managing glaucoma, there is a lack of India-specific clinical guidelines on glaucoma. Ophthalmologists often refer to the European Glaucoma Society (EGS) and Asia-Pacific Glaucoma Society (APGS) guidelines. A group of glaucoma experts was convened to review the recently released EGS guideline (fifth edition) and the APGS guideline and explore their relevance to the Indian context. This review provides the salient features of EGS and APGS guidelines and their utility in Indian scenario. Glaucoma diagnosis should be based on visual acuity and refractive errors, slit-lamp examination, gonioscopy, tonometry, visual field (VF) testing, and clinical assessment of optic nerve head, retinal nerve fiber layer (RNFL), and macula. The intraocular pressure target must be individualized to the eye and revised at every visit. Prostaglandin analogues are the most effective medications and are recommended as the first choice in open-angle glaucoma (OAG). In patients with cataract and primary angle-closure glaucoma (PACG), phacoemulsification alone or combined phacoemulsification and glaucoma surgery are recommended. Trabeculectomy augmented with antifibrotic agents is recommended as the initial surgical treatment for OAG. Laser peripheral iridotomy and surgery in combination with medical treatment should be considered in high-risk individuals aged <50 years. In patients with phakic and PACG, phacoemulsification alone or combined phacoemulsification and glaucoma surgery are recommended. Visual acuity, VF testing, clinical assessment of the optic disc and RNFL, and tonometry are strongly recommended for monitoring glaucoma progression., Competing Interests: None

Purpose: This study examined characteristics of intraocular pressure (IOP) as measured during home tonometry in comparison with in-clinic tonometry in patients with glaucoma., Design: Retrospective cross-sectional study of glaucoma patients who completed 1 week of self-tonometry at a single academic center., Participants: Patients with glaucoma who completed home tonometry trials with the iCare HOME tonometer (iCare USA) for any reason., Methods: Home IOP measurements were compared with in-clinic tonometry performed during the 5 visits preceding home tonometry. Maximum daily IOP was correlated to time of day. Generalized estimating equations were used to evaluate patient characteristics and clinic-derived variables that predicted differences between home and clinic IOP., Main Outcome Measures: IOP mean, maximum, minimum, range, standard deviation and coefficient of variation were compared between clinic and home tonometry. IOP mean daily maximum (MDM) and mean daily range were calculated to describe recurrent IOP spiking., Results: A total of 107 eyes from 61 patients were analyzed. Mean age was 63.2 years (standard deviation [SD], 14.0 years) and 59.0% were women. Mean clinic and home IOPs were 14.5 mmHg (SD, 4.7 mmHg) and 13.6 mmHg (SD, 5.1 mmHg). Home tonometry identified significantly higher maximum IOP, lower minimum IOP, and greater IOP range than clinic tonometry (P < 0.001). Maximum daily IOP occurred outside of clinic hours (8 am-5 pm) on 50% of days assessed and occurred between 4:30 am and 8 am on 24% of days. Mean daily maximum IOP exceeded maximum clinic IOP in 44% of patients and exceeded target IOP by 3 mmHg, 5 mmHg, or 10 mmHg in 31%, 15%, and 6% of patients, respectively. Patient characteristics that predicted significant deviations between MDM and mean clinic IOP or target IOP in multivariate models included younger age, male gender, and absence of prior filtering surgery., Conclusions: Self-tonometry provides IOP data that supplements in-clinic tonometry and would not be detectable over daytime in-clinic diurnal curves. A subset of patients in whom home tonometry was ordered by their glaucoma clinician because of suspicion of occult IOP elevation demonstrated reproducible IOP elevation outside of the clinic setting. Such patients tended to be younger and male and not to have undergone previous filtering surgery., (Copyright © 2021 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)

Background: The purpose of this study was to evaluate the repeatability of masked Goldmann tonometry performed by optometry students on patients with glaucoma., Methods: Subjects were recruited from among patients scheduled to undergo selective laser trabeculoplasty at the Rosenberg School of Optometry clinic. Each subject had masked Goldmann tonometry performed by three examiners at each office visit: two fourth professional-year optometry interns and an attending optometrist. Each examiner performed three sequential masked tonometry measurements on each eye., Results: Twenty-eight interns and two optometrists performed masked Goldmann tonometry on 12 glaucoma patients. The co-efficient of variation was 9.1 per cent for the right eye and 12.1 per cent for the left eye for interns compared with 6.4 per cent right eye and 6.6 per cent left eye for optometrists. There was significant interaction between intern and patient on co-efficient of variation (two-factor analysis of variance, p = 0.005), indicating co-efficient of variation was influenced by both intern and patient factors. No such interaction was found for optometrist-performed measurements (p = 0.96). Mean interobserver difference for interns ranged between 0.9 and 3.1 mmHg, with 95 per cent limits of agreement that were proportional to mean intraocular pressure. Mean interobserver difference for optometrists ranged between 0.6 and 1.8 mmHg without proportionality bias. At higher pressure levels intern measurements became more variable and tended to overestimate optometrist measurements., Conclusions: Both intraobserver and interobserver repeatability of masked tonometry was lower for interns than experienced optometrists. Intern performance differed from optometrists in that intern measurements became more variable at higher intraocular pressure levels and were significantly influenced by patient factors. The present results support the need for trainee exposure to patients with abnormally elevated intraocular pressure. Research into factors that influence trainee Goldmann tonometry repeatability is needed., (© 2020 Optometry Australia.)

The novel coronavirus disease COVID-19 caused by Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) has resulted in a substantial change in eye care and clinical practice. There has been conflicting information and weak evidence on the virus's transmission through tears. Yet, virus detection on cornea and conjunctiva surface as a gateway for infection is not well-studied. Moreover, there have been no reported cases of SARS-CoV-2 transmission through tonometry to date. Thus, this uncertainty has urged this review on evidence-based guidelines and recommendations on tonometer use in the COVID-19 era. The aim of this article is to provide ophthalmologists with recommendations for tonometry practice based on current evidence and best practice guidelines., Competing Interests: There are no conflicts of interest., (Copyright: © 2020 Middle East African Journal of Ophthalmology.)

Primary open-angle glaucoma is a major cause of irreversible blindness in all countries of the world. The pathogenesis of primary open-angle glaucoma has not been resolved. In addition to increased intraocular pressure, pathogenetic factors of this disease such as reduced systemic blood pressure, deterioration of ocular blood flow, as well as vascular dysregulation, reperfusion damage and oxidative stress of ocular tissues are now generally recognized. The role of α1-adrenoreceptors in regulation of, for example, ocular blood flow, blood flow in the retina, permeability of the vascular wall etc has already been described., Purpose: To identify the effects of different subtypes of α1-adrenoreceptors on the level of systemic blood pressure in laboratory mice., Material and Methods: Features of blood pressure of 36 laboratory mice older than 18 months having a genetic defect (lines ADRA-1A, ADRA-1D and ADRA-1D) of one of the subtypes of α1-adrenoreceptors (α1a, α1b, α1d) were studied. The control group included ten healthy laboratory mice of the same age. The blood pressure of mice was measured with modern high-precision and noninvasive method using the Coda TM Standard system (Kent Scientific Corporation, U.S.A.)., Results: The mice of the ADRA-1A line were revealed to have reduced systolic and diastolic blood pressure and maximum level of pulse pressure, as well as the greatest fluctuations of pulse pressure; for the ADRA-1B line - the highest levels of systolic and diastolic blood pressure; for the ADRA-1D line - the smallest systolic and diastolic blood pressure and the minimum values of pulse pressure., Conclusion: The obtained results show the specific contribution of α1a, α1b and α1d subtypes of the adrenoreceptors in the maintenance of normal hemodynamic of an organism, which should be considered when studying pathogenesis of primary open-angle glaucoma.

Purpose: To evaluate the apparent intraocular pressure (IOP) change observed after treatment with latanoprost in naive eyes of patients with primary open-angle glaucoma (POAG) or ocular hypertension (OHT) using Goldmann applanation tonometer (GAT), ocular response analyzer (ORA) and Corvis ST tonometry., Methods: Prospective observational cohort study. One eye from each of 59 newly diagnosed patients with POAG or OHT in our institution was analysed. IOP readings obtained using GAT, ORA and Corvis at baseline and after a 3-month period of treatment with latanoprost were compared. Additionally, pre- and post-treatment biomechanical corneal parameters provided by the Corvis tonometer were analysed., Results: There was no statistically significant difference between the apparent treatment-induced IOP reductions when GAT and ORA were compared (p > 0.05). In contrast, the treatment-induced IOP reduction recorded using the Corvis tonometer was significantly smaller compared to the apparent IOP reduction observed with GAT and ORA (p = 0.0001 for both comparisons). With respect to biomechanical corneal properties, statistically significant changes were found after 3 months of treatment with latanoprost for the first corneal applanation time (AT1) (p = 0.001), second corneal applanation time (AT2) (p = 0.001) and deformation amplitude (DA) (p = 0.0003)., Conclusion: Following a 3-month course of latanoprost, the apparent treatment-induced IOP reduction in previously naïve patients with POAG or OHT differed depending on the tonometer used. Certain corneal biomechanical parameters assessed using Corvis ST exhibited a significant change. The ocular hypotensive effect of prostaglandin analogues may be overestimated when chronically treated patients are measured using GAT or ORA., (© 2019 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.)

Measuring intraocular pressure (IOP) is the cornerstone of a comprehensive glaucoma examination. In babies or small children, however, IOP measurements are problematic, cannot often be performed at the slit lamp, and sometimes require general anesthesia. Therefore, it is essential for an ophthalmologist who examines a pediatric patient to be aware of the different tonometers used in children, as well as the effects of central corneal thickness and anesthesia on IOP measurements. Goldmann applanation tonometry is the gold standard for IOP assessment. Most alternative tonometers tend to give higher IOP readings than the Goldmann applanation tonometer, and readings between different tonometers are often not interchangeable. Similar to Goldmann tonometry, many of these alternative tonometers are affected by central corneal thickness, with thicker corneas having artifactually high IOP readings and thinner corneas having artifactually lower IOP readings. Although various machines can be used to compensate for corneal factors (e.g., the dynamic contour tonometer and ocular response analyzer), it is important to be aware that certain ocular diseases can be associated with abnormal central corneal thickness values and that their IOP readings need to be interpreted accordingly. Because induction and anesthetics can affect IOP, office IOPs taken in awake patients are always the most accurate., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)

Intraocular pressure (IOP) is known to have a definite circadian rhythm and its fluctuation correlates well with glaucoma progression. Twenty-four hour monitoring of IOP is an important indicator intraocular pressure fluctuation, as well as its peaks and spikes. However, Diurnal variation in IOP is well recognized but many decisions in glaucoma management are taken after one or two IOP measurements. Patient directed self-tonometry can be preformed through the twenty-four cycle, and has been the subject of an ongoing debate. In this review, we studied the history of self-tonometry devices and the present technologies for future. The results of various techniques studied revealed that a standardized method of conducting diurnal variation is yet to be ascertained, and for this, a proper research method is required., (©Romanian Society of Ophthalmology.)

Objectives: To compare intraocular pressure (IOP) measurements obtained with the Icare Pro tonometer used in clinical practice and the Icare One self-tonometer., Materials and Methods: Fifty-two eyes of 52 healthy, right-handed individuals with no prior intraocular surgery or ocular trauma, structural ocular pathology, or systemic disease were evaluated. IOP was first measured using the Icare Pro tonometer. The participants were then told how to use the Icare One tonometer and asked to measure their own IOP. The results were analyzed statistically using SPSS v.24., Results: Of the 52 healthy participants, 16 (30.7%) were male and 36 (69.3%) were female. Their mean age was 31.6±6.3 (23-47) years. Mean IOP measured with the Icare Pro was 17.10±6.2 (11.5-25.2) mmHg, and the mean self-measured IOP with Icare One was 14.01±3.4 (7-24) mmHg. When the two methods were compared using Levene’s t-test, there was a significant mean difference of -3.08±0.6 (95% confidence interval: -4.39 -1.78; p<0.001)., Conclusion: In this study, there was a significant difference between the IOP measurements we made using the Icare Pro and the participants’ self-measured IOP using the Icare One, with the latter being relatively lower. This may be related to the fact that the participants were unfamiliar with using the Icare One. Although the Icare One is a promising tool for glaucoma patients to self-monitor their IOP, further studies are needed.

This review describes some of the most recent advances in the development and application of new technologies for detecting and managing glaucoma, including imaging, visual function testing, and tonometry. The widespread availability of mobile technology in the developing world is improving health care delivery, for example, with smartphones and mobile applications that allow patient data to be assessed remotely by health care providers., (Copyright 2018 Asia-Pacific Academy of Ophthalmology.)

This chapter provides an overview over the use of animal models in glaucoma research from a historical perspective. Strengths and limitations of various models are considered, and the challenges of translating results in animal experiments to successful clinical trials in humans are discussed.

Purpose: The purpose of this study is to compare intraocular pressure (IOP) measured by the Goldmann applanation tonometer (GAT), the Tono-Pen XL (TPXL), and a noncontact airpuff tonometer (NCT) in glaucoma patients and normal controls., Methodology: In the current study, two groups of individuals were recruited; the first group included glaucoma patients (glaucoma group) while the second one was a glaucoma-free group. The IOP was measured through GAT, NCT, and TPXL for the same participants by three different physicians in both groups. Measurements through the three devices were compared statistically. Correlations between different methods of assessment were also assessed., Results: In the glaucoma group, the mean IOP measured was 16.0 ± 5.5 mmHg (range, 6-40 mmHg) with GAT 20.5 ± 6.9 mmHg (range, 10-52 mmHg) with the TPXL, and 20.2 ± 6.5 mmHg (range, 8-50 mmHg) with the NCT. In the control group, the mean IOP was 14.0 ± 2.7 mmHg (range, 9-19 mmHg) with GAT, 17.3 ± 3.8 mmHg (range 6-30 mmHg) with the TPXL, and 17.9 ± 3.9 mHg (range 10-27 mmHg) with the NCT., Conclusion: IOP measurements were approved among the three devices with relatively higher readings using both NTC and TPXL. All three methods are required to address different situations that present in the daily clinical and surgical practice., Competing Interests: There are no conflicts of interest.

People residing in rural and remote areas (worldwide) have substantially worse outcome in early detection and diagnosis of glaucoma than those living in metropolitan areas. This gap can be reduced by improved glaucoma diagnosis activities in primary care, but there is little empirical evidence regarding use of tonometry in rural settings, or the expertise associated with quality of eye care. This article describes a feasibility study of a novel through-eyelid tonometer based on the use of an instrumented form of indentation and applanation tonometry.

Glaucoma is a multifactorial neurodegenerative ocular disease leading to progressive loss of retinal ganglion cells and their axons that form the optic nerve, causing blindness. Knowledge of the pathogenesis and development of equine glaucoma is in its infancy compared with human glaucoma. Glaucoma occurs most commonly secondary to uveitis and may be underdiagnosed or misdiagnosed in horses suffering from uveitis. Recognition and clinical diagnosis of glaucoma in the horse is improved with clinician awareness and the availability of handheld tonometers. Therapy for glaucoma is aimed at decreasing aqueous humor production through medical and surgical means. Even with therapy, long-term prognosis for vision is poor., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Measurement of the intraocular pressure (IOP) is central to the diagnosis and management of pediatric glaucoma. An examination under anesthesia is often necessary in pediatric patients. Different agents used for sedation or general anesthesia have varied effects on IOP. Hemodynamic factors, methods of airway management, tonometry technique, and body positioning can all affect IOP measurements. The most accurate technique is one that reflects the awake IOP. We review factors affecting IOP measurements in the pediatric population and provide recommendations on the most accurate means to measure IOP under anesthesia based on the present literature., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Purpose: The accuracy of contact tonometry may be compromised in cases with disorders affecting central corneal bio-mechanical properties. This study examined the reliability of rebound tonometry (RT) on the area of corneo-scleral limbus, instead of the conventional central corneal area, and the correlation of findings with ocular biometric parameters., Methods: This is a prospective cross-sectional study performed at the Department of Ophthalmology of the University Hospital of Heraklion, in Crete, Greece. Consecutive cataract surgery candidates without concomitant ocular pathology, apart from cataract, were included. RT was performed on the central cornea (central RT, CRT) as well as on the limbus and scleral spur area (limbal RT, LRT). Findings were correlated with Goldmann applanation tonometry (GAT) as well as axial length (AL), central corneal thickness (CCT), and corneal curvature (CC) measurements., Results: LRT readings were significantly correlated with central CRT as well as with GAT readings, whereas respective correlations with other parameters examined were not statistically significant., Conclusions: LRT may be used as an alternative tool in clinical practice to determine intraocular pressure when conventional devices and techniques might be inadequate or unreliable.

Monitoring intraocular pressure (IOP) is a critically important part of glaucoma management; however, clinical tonometry predominantly involves sitting postures and is unable to detect variations in response to posture changes, muscular effort, deep respirations and during a wide range of activities, such as playing high wind-resistance instruments and wearing swimming goggles in addition to eye touching and rubbing. For example, the usefulness of 24-hour tonometric phasing may be increased, if nocturnal assessments included side and prone sleeping postures rather than being limited to supine posture tonometry. Continuous monitoring of IOP, which allows unrestricted involvement in a full range of sleep and non-sleep IOP elevating activities would provide an ideal method of quantifying the frequency, duration and degree of episodes of elevation in addition to physiological and pathological circadian rhythmic variations due to treatment. Apart from the degree of exposure to episodes of elevation of IOP, genetic influences and family history of glaucoma, other factors which are or could be associated with increased susceptibility to develop or progress glaucomatous pathology include age, frailty, race, type and degree of refractive error, systemic hypotension and hypertension, vasospasm, migraine, pigmentary dispersion syndrome, pseudoexfoliation syndrome, obstructive sleep apnoea syndrome, diabetes as well as medication interactions and side effects. Such information, when combined with all details relating to episodes of elevation of IOP, appears likely to be a strong basis for the detection, diagnosis and treatment of glaucoma. This review examines the limitations of methods of longitudinal monitoring of IOP with reference to their validity and the varying degrees of invasiveness involved. Also mentioned is the potential value of knowing the frequency, duration and level of variations of optic nerve subarachnoid space pressure, as the interaction of such changes with IOP and their potential influence on the lamina cribrosa, may help determine pathological significance., (© 2016 Optometry Australia.)

Glaucoma is a leading cause of blindness, which is treatable but currently incurable. Numerous animal models therefore have both been and continue to be utilized in the study of numerous aspects of this condition. One important facet associated with the use of such models is the ability to accurately and reproducibly measure (by cannulation) or estimate (by tonometry) intraocular pressure (IOP). At this juncture there are several different approaches to IOP measurement in different experimental animal species, and the list continues to grow. We feel therefore that a review of this subject matter is timely and should prove useful to others who wish to perform similar measurements. The general principles underlying various types of tonometric and non-tonometric techniques for non-continuous determination of IOP are considered. There follows discussion of specific details as to how these techniques are applied to experimental animal species involved in the research of this disease. Specific comments regarding anesthesia, circadian rhythm, and animal handling are also included, especially in the case of rodents. Brief consideration is also given to possible future developments., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Injection of hypertonic saline via episcleral veins toward the limbus in laboratory rats can produce elevated intraocular pressure (IOP) by sclerosis of aqueous humor outflow pathways. This article describes important anatomic characteristics of the rat optic nerve head (ONH) that make it an attractive animal model for human glaucoma, along with the anatomy of rat aqueous humor outflow on which this technique is based. The injection technique itself is also described, with the aid of a supplemental movie, including necessary equipment and specific tips to acquire this skill. Outcomes of a successful injection are presented, including IOP elevation and patterns of optic nerve injury. These concepts are then specifically considered in light of the use of this model to assess potential neuroprotective therapies. Advantages of the hypertonic saline model include a delayed and relatively gradual IOP elevation, likely reproduction of scleral and ONH stresses and strains that may be important in producing axonal injury, and its ability to be applied to any rat (and potentially mouse) strain, leaving the unmanipulated fellow eye as an internal control. Challenges include the demanding surgical skill required by the technique itself, a wide range of IOP response, and mild corneal clouding in some animals. However, meticulous application of the principles detailed in this article and practice will allow most researchers to attain this useful skill for studying cellular events of glaucomatous optic nerve damage., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The diagnosis of glaucoma is highly dependent on a working understanding of the clinical signs and available diagnostic procedures. Clinical signs may be attributable to increased intraocular pressure and/or complex alterations in the physiology or molecular biology of the anterior segment, retinal ganglion cells, and optic nerve. Many diagnostic procedures seek to more fully characterize these alterations and to identify which clinical features increase the risk of overt primary angle closure glaucoma (PACG) occurring. Considerable progress has been made in identifying the anatomic features that predispose an eye to PACG, and in elucidating the role of reverse pupillary block., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Purpose: The purpose of this study is to provide better understanding of the Ocular Response Analyzer (ORA) and how reliable it is to produce intraocular pressure (IOP) measurements that are free of the effects of corneal stiffness parameters, and stiffness estimates that are independent of IOP., Materials and Methods: A numerical parametric study that closely represents the in-vivo conditions of the human eye and the ORA procedure was conducted to determine the correlation coefficient r(2) between ORA output and the values of true IOP and a number of stiffness parameters, namely corneal thickness, curvature and age. For the purpose of this exercise, the ORA output was put in the form k1P1+k2P2 where k1 and k2 were variables and P1 and P2 were ORA's measured applanation pressures. Two separate clinical datasets involving Moorfields Eye Hospital, London and the University of New South Wales, Sydney participants, respectively, were used to validate the numerical results., Results: The numerical study results show a strong association between (k1P1 + k2P2) and the true IOP over a wide range of k1 and k2 values apart from a narrow region approximately extending from (k1 = +2, k2 = -2) to (k1 = -2, k2 = +2). On the other hand, (k1· P1 + k2· P2) was found to have a strong association with CCT, R and age (the stiffness parameters) over the same narrow region, beyond which the association was weak. Similar trends were found with the two clinical datasets., Conclusions: The results of this study show the potential of the ORA to provide reliable IOP measurements with weak dependence on the cornea's stiffness parameters and the considerably reduced reliability in producing stiffness estimates that are unaffected by IOP values.