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Common Vitreoretinal Procedures
Published in Pradeep Venkatesh, Handbook of Vitreoretinal Surgery, 2023
Preoperative evaluation must also pay attention to the status of the corneal endothelium [endothelial cell count and other indices by specular microscopy]; depth of the anterior chamber; presence of vitreous in the anterior chamber and pupillary margin; extent of pupillary dilatation; damage to the iris, ciliary body, or trabecular meshwork; and presence of retinal tears. Taking note of the amount of capsular remnant, available, if any, would aid in planning the type of IOL that could be implanted. In addition, in case of dislocation following open globe trauma or cataract surgery, integrity of the open wound must be doubly confirmed. Any form of pressure on the globe must be avoided during local anaesthesia to prevent sudden wound dehiscence, vitreous loss, or even expulsive haemorrhage.
Preclinical Toxicology/Safety Considerations in the Development of Ophthalmic Drugs and Devices
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
Robert B. Hackett, Michael E. Stern
The corneal endothelium is a monolayer of cells on the internal aspect of the cornea (in the anterior chamber) which is bathed by the aqueous humor. These cells are primarily responsible for maintaining the proper level of corneal hydration. The corneal water content is approximately 72% in the normal, nonswollen, state. If this level is allowed to increase, the resulting corneal edema will cause back-scattering of light and eventual corneal opacity. This technique takes advantage of the direct correlation between corneal thickness and endothelial compromise.
Nanomedicines for Ocular NSAIDs: State-of-the-Art Update of the Safety on Drug Delivery
Published in Lajos P. Balogh, Nano-Enabled Medical Applications, 2020
Joana R. Campos, Joana Araújo, Elisabet Gonzalez-Mira, Maria A. Egea, Elena Sanchez-Lopez, Marta Espina, Selma B. Souto, Maria L. Garcia, Eliana B. Souto
The cornea is an important route for drug absorption after topical application. It consists of five different layers, namely epithelium, Bowman’s membrane, stroma, Descemet’s membrane, and endothelium [12]. The corneal epithelium, lipophilic in nature, acts as a selective barrier for small molecules and prevents the diffusion of macromolecules via the paracellular route, it plays a major role in limiting trans-corneal drug absorption with a drug permeability rate of only 10−7–10−5 cm s−1 [12–14]. While small lipophilic drugs are passively transported via the transcellular pathway, hydrophilic drugs undergo restricted permeation through tight junctions via the paracellular pathway [10]. The stroma, located below the epithelium, is a highly hydrophilic layer making up 90% of the cornea. The corneal stroma being hydrophilic impedes transport of lipophilic drug molecules while hydrophilic molecules generally diffuse freely through the stroma [10]. The corneal endothelium consists of a single layer of flattened epithelium-like cells and it is responsible for maintaining normal corneal hydration. Since the cornea is characterized by lipophilic and hydrophilic structures, it represents an effective barrier to the absorption of both hydrophilic and lipophilic molecules [15, 16].
Recent and Evolving Therapies in the Management of Endothelial Diseases
Published in Seminars in Ophthalmology, 2023
Shalini Singh, Sunita Chaurasia
Corneal endothelium is the innermost layer of the cornea, which has both barrier and pump function and very important to maintain cornea clarity.1,3 Corneal endothelial cells are incapable of replicating in vitro because their further replication is arrested at the G1 phase of the cell cycle. There is gradual debilitation of the endothelial cells because of the arrested cell cycle leading to decrease in both density and the number of endothelial cells with advancing age. The density of endothelial cells at birth is 3500–4000 cells/mm2, gradually declining to 2000 cells/mm2 by the age of 85.4,5 When endothelial cells are damaged, a cascade of events are initiated which leads the cells in the periphery to migrate towards the centre and form the new tight junction and finally regain the endothelial pump function. This migration is by an irregular endothelial cell which transforms into a hexagonal shape but with decrease in the density of the cells.6 This process continues throughout life, but the minimum density needed to maintain a transparent and functional cornea is 500 cells/mm.2,7
Rho-kinase inhibitors: Role in corneal endothelial disorders
Published in Seminars in Ophthalmology, 2023
Nimish Kumar Singh, Srikant Kumar Sahu
Corneal endothelium which is present on the inner surface of cornea plays a major role in maintaining corneal transparency through the endothelial pump mechanism. The endothelial cells do not have regenerative capacity and any loss in their number is compensated by migration of adjoining cells thereby decreasing their average density. Normal adult endothelial density ranges from 2000 to 2500 cells/mm.2 Decrease in endothelial density below 500–1000 cells/mm,2 due to various reasons, results in corneal edema and decompensation.4 Currently, posterior lamellar keratoplasties like Descemet stripping Endothelial Keratoplasty (DSEK) and Descemet Membrane Endothelial Keratoplasty (DMEK) are the only treatment options available for endothelial decompensation. Scarcity of appropriate donor cornea, perpetual risk of rejection, infection and side-effects of long-term corticosteroid use pose considerable hindrance in making these modalities available for all despite their high success rate.4 In such a scenario, the possible role of rho-kinase (ROCK) inhibitors in the treatment of endothelial disease can be a major breakthrough for restoring corneal transparency in such cases.
Design and Methodology of a Multi-Centre Clinical Trial of Low Dose Laser Cycloplasty for the Treatment of Malignant Glaucoma in China
Published in Ophthalmic Epidemiology, 2022
Haishuang Lin, Jibing Wang, Sujie Fan, Zuohong Wu, Xiaoping Xu, Qinhua Cai, Lijun Zhao, Sumian Cheng, Shaodan Zhang, Yuanbo Liang
An evaluation of the safety of the procedures was conducted and covered: Corneal injury: corneal injury was sought via an examination by conducting a corneal endothelium cell count.Anterior uveitis: inflammation in the anterior chamber was indicative of anterior uveitis.Hyphema: hyphema was determined by slit lamp examination.Lens injury: lens injury was determined following an examination by slit lamp.Hypotony: an IOP of ≤5 mmHg was defined to be hypotony.