Aqueous deficiency

Several studies show that photorefractive keratectomy and laser in situ keratomileusis (LASIK) can induce or exacerbate dry eye. Refractive surgery is believed to cause aqueous-deficient dry eye by a neural-based mechanism. 

Other Vinyl Derivatives. PVP is a nonionic surfactant used in 3% to 5% concentrations to increase viscosity of solutions. Although it exhibits surface-active properties similar to the cellulose ethers, PVP appears to have less abiUty to lower the interfacial tension at a water-oil interface. Nevertheless, in contrast to the cellulose ethers, PVP appears capable of forming hydrophilic coatings in the form of adsorbed layers. Because conjunctival mucin is believed to interact with the ocular surfece to form an adsorbing surface for aqueous tears, the formation by artificial means of a hydrophilic layer that would mimic conjimctival mucin (mucomimetic) appears to be clinically desirable. Both mucin- and aqueous-deficient dry eyes would benefit, because the wetting ability of the corneal surfece would be enhanced. 

Aqueous-deficient dry eyes are subdivided into Sjogren s syndrome (SS) and non-Sjogren s syndrome (non-SS). 

Non-Sjogren s Syndrome. Non-SS KCS can be congenital or acquired.This category encompasses all other aqueous deficiency dry eye syndrome subtypes, including the mucin-deficiency dry eye, caused by damage to the goblet cells from disease, injury, or avitaminosis A. 

Lack of aqueous production at birth is a disorder termed congenital alacrima. This rare condition may result from hypoplasia of lacrimal gland tissue or congenital paralysis of cranial nerves. Another congenital and equally rare cause of aqueous deficiency is familial dysau-tonomia (Riley-Day syndrome), a disorder associated with a short life span. 

Mucolytic Agents. Acetylcysteine, which is frequently used as a bronchial mucolytic agent in patients with cystic fibrosis, can be used topically in a weakened concentration for ophthalmic use. It is malodorous and may sting on instillation however, this drug is fairly effective in disrupting mucous strands that are often present in patients with aqueous deficiency dry eye. It is not commercially available in an ophthalmic formulation it must be compounded by a pharmacist. 

Albietz J, Sanfilippo P, Troutbeck R, et al. Management of filamentary keratitis associated with aqueous-deficient. OptomVis Sci 2003 80 420-430. 

Diazonium salts couple readily with aromatic primary amines, giving diazoamino compounds. If for instance an aqueous solution of aniline sulphate is diazotised with a deficiency of nitrous acid, only part of it is converted into benzenediazonium sulphate and the latter then couples with the unchanged aniline to give diazoaminobenzene. The reaction is carried out at the opti-CeHsNHj.HjSO + HONO = CbHsNjHSO, + zHaO... 

EthynodlolDia.ceta.te, Ethynodiol diacetate has been used alone, and in combination with an strogen, as an oral contraceptive and to treat disorders associated with progesterone deficiency (76). It may be crystallised from aqueous methanol (77) and is soluble in chloroform, ether, and ethanol sparingly soluble in fixed oils and insoluble in water (76). Extensive spectral and chromatographic data have been compiled (78). 

Reactions that occur with the development of an electron deficiency, such as aromatic electrophilic substitutions, are best correlated by substituent constants based on a more appropriate defining reaction than the ionization of benzoic acids. Brown and Okamoto adopted the rates of solvolysis of substituted phenyldimeth-ylcarbinyl chlorides (r-cumyl chlorides) in 90% aqueous acetone at 25°C to define electrophilic substituent constants symbolized o-. Their procedure was to establish a conventional Hammett plot of log (.k/k°) against (t for 16 /wcra-substituted r-cumyl chlorides, because meta substituents cannot undergo significant direct resonance interaction with the reaction site. The resulting p value of —4.54 was then used in a modified Hammett equation. 

Nickel sulfides are very similar to those of cobalt, consisting of NiS2 (pyrites structure, p. 680), Ni3S4 (spinel structure, p. 247), and the black, nickel-deficient Nii-j S (NiAs structure, p. 555), which is precipitated from aqueous... 

Other examples of linear correlations of log rate coefficients with — H0 have been reported though most of them are deficient in some respect. Satchell474 observed such a correlation in the dedeuteration of anisole and benzene in various aqueous or acetic acid solutions of sulphuric acid, and aqueous perchloric acid, media at 25 °C. First-order rate coefficients are given in Table 127 along with those for dedeuteration of [4,5-2H2]-l,3,5-trimethoxybenzene and -2-hy-droxy-l,3-dimethoxybenzene475. For the ortho- andpara-monodeuterated anisoles the slopes of the log rate versus — H0 plots were the same for aqueous sulphuric acid and for acetic acid-sulphuric acid so that it was concluded that the A-l mechanism therefore applied to non-aqueous media as well as to aqueous media. The fact that the slope of the log rate coefficient versus —H0 plot was less (1.12) for benzene in aqueous perchloric acid than that (1.36) previously found in aqueous... 

In spite of well identified deficiencies, the status of the existing thermodynamic data on solid halides and related compounds is rather satisfactory. By contrast, the data on aqueous halogeno-complexes are fragmentary, sometimes contradictory and in most cases limited to stability constants in such a context, recommendation of best values can be made for a few species only. 

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