OPHTHALMIC APPLICATION

Ophthalmic Applications.—There has been little new material here. There is some overlap with information reported under sutures and contained in Section 4. Further examples of the use of hydrogels include reports on cornealand retinal surgery, development of scleral buckling agents, and animal experiments with hydrogel kertoprostheses of different water contents. 

Tighe has contributed a chapter on materials to the recently published text on contact-lens practice edited by Stone and Phillips. The measurement of mechanical properties of materials in this field has been discussed by the same authorand others. Although an interdependence of individual tear-fluid chemistry, surface 

Ophthalmic Applications.—Polymers have a wide variety of uses in ocular surgery. These have been summarized by Refojo in one of the collections previously cited. Specific clinical reports include the use of silicone rubber in orbital 

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The ophthalmic applications for plastics lenses include contact lenses which are now made of acrylic plastics. Another material for this application is a special hydrophillic acrylic polymer used in soft contact lenses. These lenses are much more comfortable than rigid contact lenses. 

One of the key parameters for correlating molecular structure and chemical properties with bioavailability has been transcorneal flux or, alternatively, the corneal permeability coefficient. The epithelium has been modeled as a lipid barrier (possibly with a limited number of aqueous pores that, for this physical model, serve as the equivalent of the extracellular space in a more physiological description) and the stroma as an aqueous barrier (Fig. 11). The endothelium is very thin and porous compared with the epithelium [189] and often has been ignored in the analysis, although mathematically it can be included as part of the lipid barrier. Diffusion through bilayer membranes of various structures has been modeled for some time [202] and adapted to ophthalmic applications more recently [203,204]. For a series of molecules of similar size, it was shown that the permeability increases with octa-nol/water distribution (or partition) coefficient until a plateau is reached. Modeling of this type of data has led to the earlier statement that drugs need to be both... 

In summary, there are numerous variables to be adjusted and many choices of excipients required when tailoring a formulation of a particular therapeutic agent for ophthalmic application. But ultimately the choice rests on finding an economically viable formulation that clinically enhances the therapeutic index for that drug. 

Examples of silicones in ophthalmic application have been described.5 1 However, some problems have been reported with the use of silicones in retinal tamponade.542 Silicones are widely used in contact lenses because of their unusually good oxygen permeability and bioinertness, but the need for novel materials continues. Low-modulus fluorosiloxane-based hydrogel lenses with a wide range of water content and high-oxygen permeability have been described in a number of papers.543-... 

The three main classes that have been much studied for ophthalmic applications are spiroindolinonaphthoxazines (see section 1.2.3), diarylnaphthopyrans (see section 1.2.4) and fulgides (see section 1.2.5). How these different photochromic classes match up to the desired criteria for use in lenses is shown in Table 1.9. From this it can be seen that fulgides exhibit only a fair fatigue resistance and spiroindolinonaphthoxazines suffer from a high temperature dependency. Consequently, for this photochromic outlet, naphthopyrans have become the molecules of choice. Typical... 

The biocompatibility of FCLs and the special requirements related to the tests for this group of substances will be discussed with special emphasis on ophthalmic application. 

Ophthalmic application may cause paresthesia of conjunctiva or mydriasis. 

The reaction product of dimethyl malonate and 1,6-hexanediol with dimethyl-aminobenzaldehyde, 4-methoxy-benzaldehyde, and 3-nitrobenzaldehyde was previously prepared by the authors (2) and used in ophthalmic applications. 

Nadolol is noteworthy for its very long duration of action its spectrum of action is similar to that of timolol. Timolol is a nonselective agent with no local anesthetic activity. It has excellent ocular hypotensive effects when administered topically in the eye. Levobunolol (nonselective) and betaxolol (E -selective) are also used for topical ophthalmic application in glaucoma the latter drug may be less likely to induce bronchoconstriction than nonselective antagonists. Carteolol is a nonselective 13-receptor antagonist. 

In conclusion, the approval of Restasis by the FDA is an important milestone in lipid emulsion research for ophthalmic application. This approval reflects the achievements of the last decade in terms of the availability of better ingredients, improved manufacturing processes, feasibility of sterilization, and better understanding of the optimization process. In all of the comparative studies done so far, positively charged SME achieved better ocular bioavailability regardless of the studied drug. Research efforts are underway to further explore the mechanism of interaction of positively charged SMEs with ocular tissues and to translate the results of this research into enhanced clinical performance. 

Adverse Effects. The primary problems associated with systemic administration of vidarabine include gastrointestinal distress (nausea, vomiting, diarrhea) and CNS disturbances (dizziness, hallucinations, mood changes). Ophthalmic application may produce local irritation (itching, redness, swelling) in some individuals. 

The topical ophthalmic application of hydroxyeicosatetraenoic acid derivatives, (III), prepared by Gamache (3) was effective in preventing ophthalmic inflammatory disorders involving cytokine secretion and used in treating conjunctivitis, iritis, uveitis, and episcleritis. 

Pignatello, R.,Bucolo, C., Spedalieri, G., Maltese, A., and Puglisi, G. (2002),Flurbiprofen-loaded acrylate polymer nanosuspensions for ophthalmic application, Biomaterials, 23(15), 3247-3255. 

Although most commonly used topical anesthetics are similar in onset, duration, and depth of anesthesia (see Chapter 6), several important differences exist. For diagnostic and treatment procedures requiring topical anesthesia, the clinician essentially has two choices tetracaine or proparacaine. Both provide rapid onset of anesthesia within 10 to 20 seconds and last approximately 10 to 20 minutes. If prolonged anesthesia is required, it may be accomplished by repeated application.Tetracaine may cause more discomfort upon instillation than proparacaine and typically results in more corneal compromise. In general, proparacaine 0.5% has a low incidence of hypersensitivity reactions and is the anesthetic of choice for topical anesthesia in ophthalmic applications. Other anesthetics that have occasional topical application are cocaine (4% to 10%) and lidocaine (4%). 

For the administration of an ophthalmic ointment to a child who can cooperate, the child should tilt his or her head backwards and look up. After the hands have been washed, the person to administer the medication should gently pull down the lower eyelid(s) for drug administration. A thin layer of ointment should then be placed in the lower eyelid(s). Afterwards, the eyelid(s) should be closed for 1 to 2 min to allow for the spreading of the medication and absorption. During this process, the tip of the ophthalmic applicator should not touch the eye. After administration is completed, the tip of the applicator tube should be cleaned with a clean tissue and be tightly capped. The package insert should also be reviewed for specific information. 

The use of povidone K 30 in effervescent cleaning tablets for contact lenses is an indirect ophthalmic application. Table 102 shows the composition of a perborate cleaning tablet taken from the literature. 

The effect of lomefloxacin on cultured rabbit corneal epithelial cells was evaluated because of its potential use for ophthalmic application. The results along with pharmacokinetic data indicate that therapeutically effective concentrations may be achieved without any cytotoxic effects (45). 

Cell-Based Delivery Systems Development of Encapsulated Cell Technology for Ophthalmic Applications... 

Neurotech USA is developing ECT for ophthalmic applications, primarily due to the many unmet medical needs in the field of ophthalmology. Although many topical pharmaceutical agents such as antibiotics and anti-inflammatory agents are available for the eye, few treatments, if any, are available for the common causes of blindness that affect millions of people worldwide. Many of these devastating diseases are... 

Two closely related basic esters, pramoxine (No. 12) and dyclonine10 (No. 13), find a variety of nonparenteral applications. These include topical uses for pain caused by abrasions and bums, and skin and rectal pruritis from any cause (e.g., hemorrhoids, dermatoses). Solutions are too irritant for ophthalmic applications, but they can be used in gargles and lozenges for sore throats (Sucrets). 

Other biomedical applications of polymers include sustained and controlled drug delivery formulations for implantation, transdermal and trans-cornealuses, intrauterine devices, etc. (6, 7). Major developments have been reported recently on the use of biomaterials for skin replacement (8), reconstruction of vocal cords (9), ophthalmic applications such as therapeutic contact lenses, artificial corneas, intraocular lenses, and vitreous implants (10), craniofacial, maxillofacial, and related replacements in reconstructive surgery (I), and neurostimulating and other electrical-stimulating electrodes (I). Orthopedic applications include artificial tendons (II), prostheses, long bone repair, and articular cartilage replacement (I). Finally, dental materials and implants (12,13) are also often considered as biomaterials. 

Of the growing applications of HA-Na over the past two decades, those pertaining to ophthalmic and orthopedic areas are paramoimt. Recent ophthalmic applications include the use of HA-Na solution in situations dealing with ... 

For ophthalmic applications, properly formulated drug-loaded nanoparticles (DNPs) are reported to provide ease of application just like eye drop solutions, with the added advantage of being patient friendly, due to less frequent application and extended duration of retention in the extraocular portion. The drug may be attached to a nanoparticle matrix, or dissolved, encapsulated, and entrapped, giving rise to different terminologies as nanoparticles, nanospheres, or nanocapsules. " ... 

Agnihotri, S.M. Vavia, RR. Diclofenac-loaded biopolymeric nanosuspensions for ophthalmic application. Nanomed. Nanotechnol. 2009, 5 (1), 90-95. 

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