Artificial tear preparations

PVA can lower the surface tension of water, reduce interfacial tension at an oil/water interface and enhance tear film stability. These together with ease of sterilization, compatibility with a range of ophthalmic dmgs and an apparent lack of epithelial toxicity have led to the widespread use of PVA as a drag delivery vehicle and a component of artificial tear preparations. 

Substituted Cellulose Ethers. Since their introduction for ophthalmic use, MC and other substituted cellulose ethers such as hydroxyethylcellulose, hydroxypropylcel-lulose, hydroxypropyl methylcellulose (HPMC), and carboxymethylcellulose (CMC) have been used in artificial tear formulations.These colloids dissolve in water to produce colorless solutions of varying viscosity. They have the proper optical clarity, a refractive index similar to the cornea, and are nearly inert chemically. Their relative lack of toxicity, their viscous properties, and their beneficial effects on tear film stability have made cellulose ethers useful components of artificial tear preparations. Historically, the most frequently used representative of this group was MC. 

Nelson JD, Farris RL. Sodium hyaluronate and polyvinyl alcohol artificial tear preparations. Arch Ophthalmol 1988 106 484-487. 

Dry eye symptoms and significant ocular surface disease frequently occur in patients taking isotretinoin.The associated symptoms may be accompanied by blepharocon-jimctivitis. The presence of isotretinoin in tear fluid decreases stability (and tear break-up time) of the lipid layer of the tear film but may also cause a decrease in aqueous production, leading to ocular surface dryness. These effects could be responsible for the dry eye symptoms, contact lens intolerance, superficial punctate keratitis, and conjunctival irritation accompanying isotretinoin therapy. Use of artificial tear preparations may help to alleviate the associated discomfort. 

Artificial tear preparations Flypromellose polyacrylic acid Eye lubrication Tear deficiency Liquid gel, viscous eye-drops... 

Nelson JD, Farris RL. Sodium hyaluronate and polyvinyl alcohol artificial tear preparations A comparison in patients with keratoconjuncitvitis sicca. Arch Ophthalmol 1988 106 484-487 Neuhann Th. Capsulorhexis. In Steinert R. (ed) Cataract Surgery technique, complications S. 134-142... 

Sodium hyaluronate appears to be free of adverse ocular or systemic effects when nsed topically on the eye at the 0.1% concentration. Cnrrent limitations to its use as an artificial tear are the absence of a commercial preparation for the dry eye and its cost this agent is considerably more expensive than other dry eye preparations for longterm use. It is available in disposable syringes and can be prepared as a 0.1% topical solntion in saline. 

Tear supplements continue to be a rapidly evolving market.As many as 50 different over-the-counter artificial tears are available.These formulations are available either in unit-dose vials or in multidose bottle delivery systems and vary by consistency, active ingredients, and preservatives.Table 24-3 lists many of these preparations. 

Treatment is usually with tear substitutes ( artificial tears ), containing compounds that enhance wetting, viscosity and stability of tears. These are hypromellose, polyvinyl alcohol (PVA), carbomer 940, and hydrophobic ocular lubricants containing liquid and soft paraffins, such as Simple Eye Ointment. All preparations are available as P medicines. 

Hydroxypropyl cellulose (HPC) is used for the preparation of artificial tears, treat medical conditions characterized by insufficient tear production such as kerotoconjunctivitis sicca, recurrent corneal erosions, decreased corneal sensitivity, exposure, and neuroparalytic keratitis. It is also used as a disintegrant and a binder in tablets, sieving matrix for DNA separations by capillary and microchip electrophoresis and lubricant for artificial eyes, food additive, thickener, and as an emulsion stabilizer [111, 112]. 

Poly (2-hydroxypropyl. Me) ether Hydro-xypropyl methyl cellulose. HPMC. E463. Hypromellose, USAN. Hydroxypropyl-methylcellulose, JAN. Cellulose hydro-xypropyl methyl ether, BAN, INN [9(X)4-65-3] Prepared by etherification of alkaline cellulose with methyl chloride and propylene oxide. Commercial samples have methyl DS values of 1.1-2.0 and hydroxypropyl MS values of 0.1 - 1.0. Thickening and binding agent with widespread industrial uses in adhesives, building products, films, protective creams and colloids. Approved for food use in US and EU. Used in deep fried batters. Shows better water solubility and electrolyte tolerance than methylcellulose. Component of artificial tears. 

Artificial tear fluid (ATF) containing a mixture of proteins (lysozyme, albumin, and mucin) and lipids (triolein, cholesteryl linoleate, etc.) was prepared following the procedure published previously 7a), The total protein concentration of the ATF was 3.2 mg/mL as determined using the Pierce BCA protein assay. Hydrogel pieces (1x1 cm in area and --1 mm in thickness) were immersed and incubated with gentle shaking, for a period of 24h in ATF solution (2 mL per hydrogel piece) in a water bath maintained at 36 C. After incubation,... 

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