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Comparative Anatomy and Physiology of the Mammalian Eye
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
The retina is the most complex of all the ocular tissues. The classic description of the retina includes 10 layers which, from the outside in, are as follows (see Figures 17, 18, and 19): Retinal pigment epitheliumPhotoreceptor outer segmentsOuter limiting membraneOuter nuclear layerOuter plexiform layerInner nuclear layerInner plexiform layerGanglion cell layerNerve fiber layerInner limiting membrane
Cryosurgery of the retina
Published in A Peyman MD Gholam, A Meffert MD Stephen, D Conway MD FACS Mandi, Chiasson Trisha, Vitreoretinal Surgical Techniques, 2019
Ingrid Kreissig, Harvey A Lincoff
If the recovery of RPE is delayed, undifferentiated retinal neuroepithelial cells may spread directly along the basement membrane and attach to it with hemidesmosomal-like structures (Fig. 5.8). The residual retina becomes a thin band of neuroepithelium between the inner limiting membrane and the RPE basement membrane. Finally, if the cryocoagulation is severe enough to cause necrosis of the basement membrane of RPE, surviving neuroepithelium may infiltrate the collagen lamellae of Bruch’s membrane24 and cause a chorioretinal scar (Figs 5.9 and 5.10).
Special Senses
Published in Pritam S. Sahota, James A. Popp, Jerry F. Hardisty, Chirukandath Gopinath, Page R. Bouchard, Toxicologic Pathology, 2018
Kenneth A. Schafer, Oliver C. Turner, Richard A. Altschuler
Secondary vitreous is neuroectodermal in origin and refers to the vitreous body in fully developed eyes. The transparent vitreous body fills the vitreous chamber and helps maintain the shape of the globe, transmits light to the retina, and maintains the normal position of the retina (Hockwin et al. 1991; Samuelson 2007). The vitreous body is composed mostly of water, but also contains hyaluronic acid, histiocytes (hyalocytes), complex carbohydrates, and collagen fibrils that join the retinal inner limiting membrane (ILM). The gel-to-liquid ratio of the vitreous body varies among species and age (Samuelson 2007). The vitreous body is a storage site for retinal metabolites and protects the lens and retina from toxic compounds. Hyaluronic acid not only provides viscoelasticity but also acts as a barrier to the diffusion of macromolecules. Processes leading to decreased hyaluronic acid and vitreal liquefaction will affect the nutrient supply, waste removal, and drug delivery to the lens and retina.
Vitreous Humor: Composition, Characteristics and Implication on Intravitreal Drug Delivery
Published in Current Eye Research, 2023
Deepakkumar Mishra, Shilpkala Gade, Katie Glover, Ravi Sheshala, Thakur Raghu Raj Singh
Occupying the vitreous cavity, the vitreous humour is a homogenous, viscoelastic hydrogel structure that helps to maintain the shape of the eyeball through its continuous contact with the retina by inner limiting membrane (Figure 1(A)). The vitreous also acts to prevent physical damage to lens and retina by absorbing any mechanical impact, as well as preventing oxidative damage.20,21 Another crucial role of the vitreous is in the transmission of light, as the transparent nature of the vitreous allows the passage of refracted light towards the photoreceptors of the retinal tissue. The received light is then converted to electrical signals by the photoreceptors which are subsequently processed in the brain. Similar the cornea, the vitreous has a refractive index of 1.336,22,23 which is crucial to its role in the transmission of light.
High myopia and vitreal veils in a patient with Poretti– Boltshauser syndrome due to a novel homozygous LAMA1 mutation
Published in Ophthalmic Genetics, 2022
Nawid Faizi, Ingele Casteels, Bruno Termote, Paul Coucke, Elfride De Baere, Marieke De Bruyne, Irina Balikova
Biallelic mutations in LAMA1 were found to underly PTBHS (4). LAMA1 encodes laminin alpha-1, one of the subunits of laminin-1 (α1β1γ1) and laminin-3 (α1β2γ1). Laminin makes up a major component of the basement membrane, such as the inner limiting membrane of the eye. It provides integrity of the tissue by connecting basement membranes and extracellular matrix to cells. There are nine genes encoding the laminin subunits that are associated with disease in humans. The expression of laminin alpha-1 is specific to certain tissues. It is detected in neuronal, urogenital, and mesodermal tissues, as well as in the vasculature of the brain and the embryonic and mature lens. The role of laminin alpha-1 in the development of the eye was also demonstrated in a mouse model and in the study of lens development in zebrafish (5–7).
Diabetic eye: associated diseases, drugs in clinic, and role of self-assembled carriers in topical treatment
Published in Expert Opinion on Drug Delivery, 2021
Axel Kattar, Angel Concheiro, Carmen Alvarez-Lorenzo
Systemic administration of ocular drugs is compromised by the blood-retinal barrier. The inner limiting membrane of the retinal pigment epithelium prevents passage of high-molecular-weight molecules from blood to vitreous and vice versa [56]. Müller cells and astrocytes form tight junctions to regulate the passage of molecules between the outer choroid and the inner retina. Although the information on ocular bioavailability after drug systemic administration in humans is limited, some reports evidenced that for small drugs, such as ciprofloxacin, similar drug levels can be obtained in aqueous humor after topical instillation of the free drug or oral administration. The levels in vitreous humor are commonly higher after oral administration, but at expenses of exposing the whole organism to high drug dose [57]. Also, interestingly, the drug can be found in tear fluid after oral administration but not because of distribution through the eye, as reported for cyclosporine A [58]. The blood-retinal barrier efficiently prevents cyclosporine A diffusion from blood to the anterior segment, except during concomitance of inflammatory processes [59].