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Development of Ophthalmic Formulations
Published in Sandeep Nema, John D. Ludwig, Parenteral Medications, 2019
Paramita Sarkar, Martin Coffey, Mohannad Shawer
Glaucoma is a sight-threatening optic neuropathy. The disease is characterized by increased IOP, excavation of the optic nerve head, reduction in the number of retinal ganglion cells, and a resultant progressive loss of visual field. Elevated IOP is a major risk factor, and available antiglaucoma drugs treat this facet of the disease. The most common form of the disease is open-angle glaucoma in which IOP rises as a result of decreased outflow of aqueous humor through the trabecular meshwork and Schlemm’s canal. Antiglaucoma drugs may act by decreasing aqueous humor production or increasing aqueous humor outflow (via the trabecular meshwork or the uveoscleral pathway) [65]. Drugs that affect aqueous humor production include beta-2-adrenergic receptor agonists, beta-1-adrenergic receptor agonists, alpha-2 adrenergic receptor agonists, and carbonic anhydrase inhibitors. The newest category of drugs used in the treatment for glaucoma is the prostaglandin analogs that affect aqueous humor outflow [66,67]. Most of these products need to be dosed once or twice daily. The prostaglandin analogs, however, have certain side effects associated with them, namely, iris hyperpigmentation and change in the length, color, and thickness of eyelashes; hyperemia; and pruritus.
Neuro-Ophthalmology
Published in Anthony N. Nicholson, The Neurosciences and the Practice of Aviation Medicine, 2017
The amplitude of the pupil response to light diminishes with age and has a considerable variance in the population in any given age group. Therefore, even with the help of quantitative pupillometry, it is not possible to identify a pupil light response as outside the normal range unless it is very severely affected. For this reason the relative afferent pupil defect, or Marcus Gunn (1850–1909) pupil, has become one of the most valuable signs in neuro-ophthalmology. It allows comparison of the strength of the pupil light reflex between the two eyes as the variance of the inter-ocular difference in the pupil light reflex is very low. The test depends upon the pupil light reflex being rather slow (120 milliseconds), which allows time to transfer the light stimulus from one eye to the other without the pupils having the time to dilate back to the size corresponding to the ambient light levels (Figure 17.7). If the test is positive, both pupils will be seen to dilate as the light source is introduced to the affected eye and to constrict as it is returned to the unaffected eye. The reduced number of functioning photosensitive ganglion cells in the affected eye will result in the effective luminance of the stimulus being reduced, exactly as if a neutral density filter (sunglasses) were placed in front of the eye. This is a sensitive test, but one that takes some practice. There are commercially available pupillometers that can quantify relative afferent pupillary defects (Volpe et al., 2009). Problems arise if there is a bilateral optic neuropathy. If the deficit is symmetrical, then there will be no difference between the pupil light reflex in each eye and the test will be negative. It can be used only to detect unilateral or substantially asymmetric deficits.
Gene Therapy for Retina and Eye Diseases
Published in Yashwant V. Pathak, Gene Delivery Systems, 2022
Glaucoma leads to the development of permanent blindness. Initially, the retinal nerve and optic nerve are damaged, causing optic neuropathy. Intraocular pressure management may provide therapeutic relief. The drainage angle formed by the cornea and iris divide glaucoma into open-angle and angle-closure forms. Congenital glaucoma is a birth defect (50).
XEN Gel Implant: a new surgical approach in glaucoma
Published in Expert Review of Medical Devices, 2018
Ankita Chaudhary, Lauriane Salinas, Jacopo Guidotti, André Mermoud, Kaweh Mansouri
Glaucoma is the second leading cause of blindness, affecting more than 70 million people worldwide with approximately 10% being bilaterally blind, making it the leading cause of irreversible blindness in the world [1]. Glaucoma is defined as a chronic progressive optic neuropathy, characterized by typical optic disk and retinal nerve fiber layer changes with corresponding visual field defects. An elevated intraocular pressure (IOP) has been considered as a major risk factor. The biological basis of glaucoma is poorly understood and the factors contributing to its progression have not been fully identified [2].