Ciliary body

Vision is vital for human activities, and eyes are very sensitive to a number of toxic insults induced by chemical compounds. The most serious outcome is permanent eye damage which may be so severe as to cause loss of vision. The eye consists of the cornea and conjunctiva, the choroid, the iris, and the ciliary body. It also contains the retina, which is of neural origin, and the optic nerve. The retina contains photoreceptors, a highly specific light-sensitive type of neural tissue. The eye also contains the lens and a small cerebrospinal fluid system, the aqueous humor system, that is important for the maintenance of the steady state of hydration of the lens and thus the transparency of the eye. 

FIGURE 24-1. In the normal eye, aqueous humor flows through the ciliary body into the posterior chamber, through the pupil into the anterior chamber, and out through the trabecular meshwork to the canal of Schlemm into the venous drculation. 

Carbonic anhydrase inhibitors decrease aqueous humor production by inhibition of the carbonic anhydrase isoenzyme II located in the ciliary body. In the eye, carbonic anhydrase catalyzes the conversion of water and carbon dioxide to bicarbonate and hydrogen ion, which is a significant step in aqueous humor production. Carbonic anhydrase inhibitors are available in systemic and topical preparations.10,13,14... 

Pilocarpine directly stimulates the muscarinic (M3) receptors of the ciliary body which causes contraction of the ciliary muscle. This results in widening of the spaces in the trabecular meshwork, which causes an increase in aqueous humor outflow and reduces IOP by 20% to 30%. 

Uveitis An inflammation of the uvea in the eye. Uveal structures include the iris, the ciliary body, and the choroid. 

Nevertheless, there are reports on enhancement of ocular drug absorption by bile salts [33], surfactants [200], and chelators [149], Newton et al. [35] demonstrated that Azone, an enhancer widely tested in transdermal drug delivery [201], increased the ocular absorption of cyclosporine, an immunosuppressant, by a factor of 3, thereby prolonging the survival of a corneal allograft. In 1986, Lee et al. [34] reported that 10 pg/mL cytochalasin B, an agent capable of condensing the actin microfilaments, increased the aqueous humor and iris-ciliary body concentrations of topically applied inulin (5 kDa) by about 70% and 700%, respectively, in the albino rabbit. 

In the eye, carotenoids occur mainly in the retina, but the xanthophylls, lutein and zeaxanthin, can also be detected in the lens and the ciliary body. The human lens contains lutein and zeaxanthin... 

Lutein and zeaxanthin are the dominant carotenoids in nonretinal eye tissue, and lycopene and p-carotene have been found in the ciliary body, which after the retina and the retinal pigment epithelium (RPE) contains the highest quantity of carotenoids (Bernstein et al. 2001). The orbital adipose tissue also contains measurable quantities of lutein and p-carotene, and possibly other carotenoids as minor constituents (Sires et al. 2001). It is also interesting to note that lutein was recently identified in the vitreous body of human fetuses, 15-28 weeks old (Yakovleva et al. 2007). However, these results may have to be considered with caution, because the vitreous bodies were described as substantially being penetrated with hyaloid blood vessels, which could have contaminated the vitreous with blood. 

S.K. Amaki,Y. Oguchi, T. Ogata, T. Suzuki, K. Akeo, and T. Hiramitsu, L-DOPA produced nitric oxide in the vitreous and caused greater vasodilation in the choroid and the ciliary body of melanotic rats than in those of amelanotic rats. Pigm. Cell. Res. 14, 256-263 (2001). 

Ciliary body Bladder Nicotine-like Striated muscle... 

Accommodation (fig. 9). The lens of the eye is suspended by the zonula (suspensory ligament) consisting of delicate transparent fibres attached on the one hand to the ciliary body and on the other to the elastic capsule covering the lens. At rest, this zonula is under tension and in consequence the lens assumes a flattened form. When the ciliary muscle contracts it pulls the... 

The muscle fibres of the ciliary bodies are innervated by the mrd or oculomotor nerve. As explained above, when these fibres contract they allow the lens to take up its natural shape. Direct stimulation of the Illrd nerve therefore produces accommodation for near objects. Parasympathomimetic drugs have a similar action, whereas atropine paralyses this effect and so accommodates the lens for seeing distant objects. 

Ciliary body- See Warnings. Disturbance of accommodation with blurred vision. This reaction is dose-related and reversible with cessation of therapy. 

Hypersensitivity to cholinesterase inhibitors or any component of the formulation active uveal inflammation or any inflammatory disease of the iris or ciliary body glaucoma associated with iridocyclitis. 

Beside the cardiac indications /3-blockers can be used in the therapy of glaucoma. Systemic but also the local application of these compounds can reduce intraocular pressure. The mechanism of this action is a reduced production of aqueous humor by the ciliary body. Although applied locally, jS-blockers might be absorbed in sufficient amounts to induce systemic side effects in susceptible individuals. 

Atropine, scopolamine, cyclopentolate Cyclogyl, AK-Pentolate, and others) and tropicamide Mydriacyl, Tropicacyl, and others) are among the antimuscarinic drugs used in ophthalmology. All of these agents are tertiary amines that reach the iris and ciliary body after... 

The duration of treatment for skin diseases is often longer than it is for malaria, and therefore, dose-related toxicities are important. The most serious toxicities are ophthalmological. Reversible alterations include ciliary body dysfunction and corneal changes with edema and deposits. Irreversible retinopathy also occurs however, it is less common with quinacrine than with the other two drugs. Toxicity may be asymptomatic, but the earliest symptoms are night blindness, scotoma, or tunnel vision. 

As mentioned above, impaired fluid absorption in kidney proximal tubule in AQPl deficiency indicates the need for high cell membrane water permeability for rapid, near-isosmolar fluid transport. The involvement of AQPs in fluid secretion by glands (salivary, submucosal, sweat, lacrimal), and by the choroid plexus and the ciliary body has been investigated using appropriate knockout mouse models. The general conclusion is that AQPs facilitate active fluid (secretion and absorption) when sufficiently rapid, in which case AQP deletion is associated with reduced volume and increased ion/solute content of secreted fluid. AQPs appear not to be needed when fluid secretion rate (per unit epithelial surface area) is low, as AQP-independent water permeability is high enough to support slow fluid secretion (or absorption). 

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