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Computer and Human Vision Systems
Published in Sheila Anand, L. Priya, A Guide for Machine Vision in Quality Control, 2019
The retina is the light-sensitive membrane that lines the inner surface of the back of the eyeball. Images are formed on the retina and it transmits those visual messages to the brain using electrical signals. Ora serrata is a special structure that demarcates the sensitive part of retina from its non-sensory part. This layer lies close to the choroid and consists of a single layer of cells containing the pigment. The choroid lies between the sclera and the retina. It supplies the blood vessels that nourish the outer two-thirds of the retina. The space between the lens and retina is covered by a transparent colorless fluid known as vitreous humor or simply as vitreous. The vitreous humor is fluid-like near the center, and gel-like near the edges. It is surrounded by a layer of collagen, called vitreous membrane, that separates it from the rest of the eye. With age, the vitreous humor begins to shrink and problems like posterior retinal detachment or retinal tears occur.
Perceptual Impairments
Published in Julie A. Jacko, The Human–Computer Interaction Handbook, 2012
Julie A. Jacko, V. Kathlene Leonard, Molly A. McClellan, Ingrid U. Scott
Management of diabetic retinopathy includes referring the patient to an internist for optimal glucose and blood pressure control. In the Early Treatment Diabetic Retinopathy Study, focal or grid laser photocoagulation treatment for clinically significant macular edema reduced the risk of moderate visual loss, increased the chance of visual improvement, and was associated with only mild loss of visual field (Early Treatment Diabetic Retinopathy Study Research Group 1995). Intravitreal triamcinolone acetonide and other intra-vitreal anti-VEGF agents are currently under investigation for the treatment of diabetic macular edema. Panretinal laser photocoagulation treatment of eyes with high-risk proliferative diabetic retinopathy reduced the risk of severe visual loss by 50% compared to untreated control eyes (Diabetic Retinopathy Study Research Group 1981). Surgery is often indicated for nonclearing vitreous hemorrhage and for tractional retinal detachment involving or threatening the macula.
Development of Ophthalmic Formulations
Published in Sandeep Nema, John D. Ludwig, Parenteral Medications, 2019
Paramita Sarkar, Martin Coffey, Mohannad Shawer
Vitreous humor is a gel-like material that occupies the space between the lens and the retina. The vitreous humor is composed mainly of water (98%–99.7%), collagen fibrils, and hyaluronic acid [25]. It supports the posterior surface of the lens and helps keep the neural part of the retina in place. The normal aging process can lead to liquefaction of the vitreous (>50% by age 80–90) and posterior vitreous detachment. The close proximity of the vitreous to the retina and choroid makes this cavity a direct place for drug delivery to the posterior tissues.
Detection of macular diseases in optical coherence tomography image
Published in International Journal of Parallel, Emergent and Distributed Systems, 2020
Xiaoming Liu, Zhou Yang, Wei Hu, Jun Liu, Kai Zhang
Many macular diseases can lead to vision decreasing or blindness such as macular edema, macular hole and age-related macular degeneration (shown in Figure 2). Macular edema [3] occurs when fluid and protein deposit on the macular and cause retina to thicken or swell. It can be classified into cystoid macular edema involving fluid accumulation in the outer plexiform layer, and diabetic macular edema caused by leaking macular capillaries. Macular hole [4] is a small break in the macular. The vitreous is a jelly-like substance in the eye, and it is usually adherent to retina. Along with the growth of age, vitreous get watery and begin to separate from the retinal surface. The higher the degree of attachment between vitreous and retina, the more likely macular hole is developed. Age-related macular degeneration [5] typically occurs in older people where the severity is divided into early, intermediate and late types. Drusen, which appear as a bulge, is an important clinical indicator for this disease, and it occurs at the neighbourhood of retinal pigment epithelium (RPE).