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Monographs of Topical Drugs that Have Caused Contact Allergy/Allergic Contact Dermatitis
Published in Anton C. de Groot, Monographs in Contact Allergy, 2021
Echothiophate is a potent, long-acting cholinesterase inhibitor with parasympathomimetic activity. Its iodide salt echothiophate iodide (CAS number 513-10-0, EC number 208-152-1, molecular formula C9H23INO3PS) potentiates the action of endogenous acetylcholine by inhibiting acetylcholinesterase that hydrolyzes acetylcholine. When applied topically to the eye, this agent prolongs stimulation of the parasympathetic receptors at the neuromuscular junctions of the longitudinal muscle of the ciliary body. Contraction of longitudinal muscle pulls on the scleral spur, and opens the trabecular meshwork, thereby increasing aqueous humor outflow from the eye and reducing intraocular pressure. Echothiopate iodide is indicated for use in the treatment of subacute or chronic angle-closure glaucoma after iridectomy or where surgery is refused or contraindicated (1).
Draw a diagram of the anterior chamber drainage angle and write short notes on the anatomy of the structure
Published in Nathaniel Knox Cartwright, Petros Carvounis, Short Answer Questions for the MRCOphth Part 1, 2018
Nathaniel Knox Cartwright, Petros Carvounis
From anterior to posterior, the following structures may be seen on gonioscopy: Schwalbe’s line, the posterior termination of Descemet’s membrane, appears as an opaque line and lies anterior to the commencement of the trabecular meshworkthe corneal wedge coincides with Schwalbe’s line. It can be identified on gonioscopy as the point where the reflections of a narrow slitlamp beam from the internal and external corneal surfaces meetthe trabecular meshwork, which contains Schlemm’s canal and is attached to the scleral spur. In certain pathological conditions the trabeculum becomes hyperpigmentedthe canal of Schlemm can be seen in some eyes without trabecular pigmentation as a slightly darker line deep to the posterior trabeculum. Schlemm’s canal is lined by endothelium and aqueous passes into it in vacuoles formed from the endothelium of the trabecular meshwork. It is not in direct communication with the aqueousthe scleral spur is one of the most consistent angle landmarks between individuals. It is seen as a shiny white band of sclera running between the trabecular meshwork and ciliary body. The longitudinal muscle fibres of the ciliary muscle insert into the scleral spurthe anterior face of the ciliary body is marked by a pigmented band. Its width depends on the position of iris insertioniris processes can be seen in about one-third of eyes. Iris processes are small insertions of the anterior iris surface which insert at the level of the scleral spur. They are less common with increasing agenormal blood vessels run in a radial direction at the base of the angle recess. Pathological blood vessels may run in any direction.
Analyzing Anatomical Factors Contributing to Angle Closure Based on Anterior Segment Optical Coherence Tomography Imaging
Published in Current Eye Research, 2022
Bingsong Wang, Kai Cao, Zhiheng Wang, Ye Zhang, Nathan Congdon, Tao Wang
The anterior segment of all participants was imaged in the sitting position (CASIA OCT, Tomey, Inc, Nagoya, Japan). All participants were imaged in the same darkened ambient light conditions by an experienced operator, masked to other test results and clinical information regarding the participants. Scans were centered on the pupil, and cross-sectional images were obtained from the nasal and temporal angles using the standard anterior segment single-scan mode. To obtain the best-quality image, the examiner adjusted the saturation and noise and optimized the polarization for each scan during the examination. Images were processed using the device’s specialized measurement software. First the location of the scleral spur was identified by an experienced glaucoma specialist, then the software automatically measured anterior segment parameters. The accuracy of the software has been confirmed by previous studies.10,13,17,18
Clinical role of swept source optical coherence tomography in anterior segment diseases: a review
Published in Seminars in Ophthalmology, 2021
Amar Pujari, Divya Agarwal, Namrata Sharma
Similar to superior corneal, lenticular, and axial length measurements of SS-ASOCT, its enhanced scan speed and deeper tissue penetration abilities has enabled more meticulous study of Scleral spur (SS), Schwalbe’s Line (SL), Schlemm’s Canal (SC), and iris profile with a 3-dimensional reconstruction.35,36 Considering these possibilities, Chen Z et al. explored the effect of aging on angle parameters. With increasing age, progressive decline in Schlemm’s canal area and its diameter, and an increase in trabecular meshwork thickness with static width were evident.37 In addition, among the four quadrants of SC area and diameter, the nasal and temporal quadrants were found to be wider.37 However, Shi et al. contradicted these observations by noting no significant differences between nasal and temporal SC area, perimeter and diameter (in Asian normal eyes).38 Hence, age-related changes in angle parameters may be evident for the time being; however, further large-scale studies with specific attention to quadrant-wise affection are warranted.
Biomechanics of suprachoroidal drug delivery: From benchtop to clinical investigation in ocular therapies
Published in Expert Opinion on Drug Delivery, 2021
Shelley E. Hancock, Chen-Rei Wan, Nathan E. Fisher, Rafael V. Andino, Thomas A. Ciulla
In addition to scleral thickness, the extracellular matrix connections between the sclera and the choroid/ciliary body should be considered in order to understand the boundaries of fluid flow within the SCS. At the scleral spur, the sclera adheres tightly to the ciliary body and thus the suprachoroidal and supraciliary spaces are occluded anteriorly, as seen in Figure 1. Consequently, fluid introduced into the pars plana region will expand the SCS and flow posteriorly, thereby minimizing anterior chamber exposure [23], as seen in Figure 2. The flow of fluid in the SCS is further enhance by the natural pressure differential in the eye which decreases posteriorly. Emi et al. measured the hydrostatic pressures in the SCS through direct cannulation, observing pressures 0.8 ± 0.2 mm Hg below the IOP anteriorly and 3.7 ± 0.4 mm Hg below the IOP posteriorly [24]. This pressure differential, the driving force for uveoscleral outflow, may enhance the posterior spread of drugs injected into the SCS, and thereby facilitate the treatment of macular disorders in addition to peripheral chorioretinal disorders.