Principles of Dialysis

Dialysis involves the separation of two compartments containing differing concentrations of a solute in solution by a semi-permeable membrane. This membrane allows passage of solutes of sufficiently small size from one compartment to the other along a concentration gradient. Theoretically, the solute concentration in both compartments will establish equilibrium such that there is no net flux of solute the concentration of solute not bound to nonpermeable macromolecules then will be equal in...

Epiretinal Implant

Efforts to develop an independently functioning epiretinal device for patients with outer retina degeneration are also promising for restoring simple basic visual perception (67,72,75-78). It is a similar concept to the subretinal prosthesis. Epiretinal devices are constructed, however, to utilize the output capacity of spared ganglion cells to transmit the signals they generate to activate the visual system. They are designed to rest on the inner surface of the retina rather than being...

References

F. (1996). Anatomy, microcirculation, and ultrastructure of the ciliary body. In The Glaucomas, 2nd ed., Ritch, R., Sields, M. B., Krupin, T., eds. C. V. Mosby Publishers, St. Louis, pp. 125-138. 2. Krupin, T., and Civan, M. M. (1996). Physiologic basic of aqueous humor formation. In The Glaucomas, 2nd ed., Ritch, R., Sields, M. B., Krupin, T., eds. C. V. Mosby Publishers, St. Louis, pp. 252-253. 3. Cole, D. F. (1974). Comparative aspects of intraocular fluids....

Drug Transport Across Ocular Barriers

The general goal of ophthalmic drug delivery is to maximize drug levels in the target eye tissues while minimizing the levels in the remainder of the body. Ocular delivery can be achieved by topical administration, systemic administration, periocular injections, and intraocular injections. Topical administration of drugs results in higher drug concentrations in the extrao-cular barriers (conjunctiva, cornea), followed by the anterior chamber and its structures (aqueous humor, lens), with...

Clinical Trials

The success of the RPE and IPE transplants in animal models has prompted several pilot studies in AMD and RP patients. A surgical team of ophthalmologists at the Johns Hopkins Medical Institute recently attempted a Phase 1 clinical trial aimed at restoring vision with fetal human neural retinal transplants (36). Patients selected for the transplant had advanced cases of retinitis pigmentosa and neovascular age-related macular degeneration. The objective of the pilot...

Macular Degeneration

The two most common degenerative diseases of the retina are macular degeneration and retinitis pigmentosa. In both diseases, degeneration of photoreceptor cells is the underlying cause of the pathology. Dysfunction of the RPE cells and choroidal neovascularization are also major contributing factors in the development of macular degeneration. Diseases that are grouped as macular degenerations affect central vision. Damage to the macular region is the primary cause for the loss of vision....

Intravitreal Administration

Intravitreal injection is the most direct approach for delivering drug to the vitreous humor and retina however, this method of administration has been associated with serious side efects, such as endophthalmitis, cataract, hemorrhage, and retinal detachment (59). In addition, multiple injections are usually required, further increasing the risk. Nevertheless, intravitreal injection continues to be the mode of choice for treatment of acute intraocular therapy. The kinetic behavior of...

Herpes Simplex Virus Infection

Herpes viruses are among the most well-studied microorganisms that cause chronic infection and are a well-described cause of ocular diseases (89,102). Ocular degeneration due to infection with herpes simplex type 1 (HSV-1) and herpes simplex type 2 (HSV-2) is a leading cause of blinding keratitis in industrialized countries (102,103). Analysis of ocular viral isolates demonstrated that HSV-1 is responsible for about 85 of ocular HSV infections (102,103). Ocular HSV-1 infection consists of an...

Info

A EXT extrapolated method determined by extrapolating log-linear elimination phase t0 C at t0 and dividing into the intracameral dose. b SS steady-state method determined by maintaining a constant concentration of drug on the cornea of an anesthetized rabbit and measuring aqueous humor concentrations of drug over time during infusion and postinfusion. See Table 3 for equatiaon for VSS. a EXT extrapolated method determined by extrapolating log-linear elimination phase t0 C at t0 and dividing...

Antiviral Agent for Treatment of Cytomegalovirus Retinitis

Human cytomegalovirus is a member of the herpesvirus family, which also includes the herpes simplex (discussed below), varicella zoster, and Epstein-Barr viruses (88,89). Cytomegalovirus (CMV) and herpes simplex are the most studied of the microorganisms responsible for the opportunistic infections associated with acquired immunodeficiency syndrome (AIDS) (90). Cytomegalovirus infection in AIDS patients is most commonly manifested as retinitis (CMV retinopathy) and is the most common cause of...

Microdialysis Probe Recovery

A major concern in using microdialysis as a tool for the determination of unbound drug concentrations in the in vivo as well as in vitro settings is the Figure 1 Custom-designed microdialysis probe for posterior or anterior chamber placement into the rabbit eye. Figure 1 Custom-designed microdialysis probe for posterior or anterior chamber placement into the rabbit eye. assessment of recovery. Recovery may be defined as the proportion of solute extracted from the medium surrounding the probe...

Dry

Though collagen shields have a lubricating effect, they are not useful as a treatment for keratoconjunctivitis sicca because they must be applied in the physician's office and they are not transparent. Kaufman et al. (66) tested a similar system, with the addition of therapeutic agents during manufacturing (Collasomes), for drug delivery to the ocular surface. The size of Collasomes was 1 mm x 0.1 mm x 2 mm. Ease of application and minimal interference with vision were the advantages of this...

Conclusions

The last 10-20 years have seen the development and optimization of the technology of iontophoresis as a noninvasive method of drug delivery. Peptide and protein drugs (e.g., insulin and vasopressin) have been delivered iontophoretically without the pain and side effects associated with traditional subcutaneous injection (10,165,166). Iontophoresis also has the potential to revolutionize clinical diagnosis and monitoring procedures in that it offers an avenue for extracting information from the...

2014 And 2015 Research References On The Aqueous Humour Electrolytes

Iontophoresis in drug delivery Basic principles and applications. Crit. Rev. Therp. Drug Carrier Systems, 11 161213. 2. Guy, R. H., Kalia, Y. N., Delgado-Charro, M. B., Merino, V., Lopez, A., and Marro, D. (2000). Iontophoresis electrorepulsion and electroosmosis. J. Control Release, 64 129-132. 3. Merino, V., Kalia, Y. N., and Guy, R. H. (1997). Transdermal therapy and diagnosis by iontophoresis. Trends Biotechnol, 15 288-290. 4. Duke-Elder, S. (1962)....

Microdialysis

The method of microdialysis provides an important alternative for obtaining intra-ocular pharmacokinetic data (10,32,42,47,100). Complete concen-tration-versus-time profiles can be obtained in individual animals by perfusing a fine cannula with normal saline at a fixed flow rate. Drug in the surrounding tissue (solute) diffuses down its concentration gradient into the perfusate and is collected for analysis. Details of this method are covered extensively elsewhere in this text. Microdialysis...

Intraocular Pharmacokinetics Using Microdialysis

Breaching Endothelial Cells

Gunnarson et al. (22) first utilized in vivo dialysis technique to sample the vitreous chamber. Studies were carried out to measure endogenous amino acids in the preretinal vitreous space. The effects of high potassium and nipecotic acid, a potent gamma-aminobutyric acid (GABA) inhibitor, on amino acid concentrations were measured. A dialysis probe was implanted in the vitreous of the eye of albino rabbits (Fig. 1). The integrity of the blood-retinal barrier was demonstrated by measuring the...

Treatment of Hyperhidrosis Tap Water Iontophoresis

The first dermatological application of iontophoresis was to treat hyperhidrosis (32). Hyperhidrosis is a condition characterized by pathologically excessive sweating due to abnormal secretion of the eccrine sweat glands in various parts of the body primarily the palms, soles and axillae (33-35) . Iontophoresis of tap water has been very effective (> 90 of patients) in inhibiting palmar and plantar hyperhidrosis, but the results are less rewarding for axillary hyperhidrosis (33,35).

Mechanisms Of Ocular Drug Absorption

Topical delivery into the cul-de-sac is, by far, the most common route of ocular drug delivery. Adsorption from this site may be corneal or noncor-neal. A schematic diagram of the human eye is depicted in Figure 1. The so-called noncorneal route of absorption involves penetration across the sclera and conjunctiva into the intraocular tissues. This mechanism of absorption is usually nonproductive, as drug penetrating the surface of the eye beyond the corneal-scleral limbus is taken up by the...