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R.J. Garofalo, N. Dassanayake; Corneal Response of Chemical Agents Released by Hydrogel and Silicone–Hydrogel Lenses As a Function of Time . Invest. Ophthalmol. Vis. Sci. 2004;45(13):1538.
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Purpose: The adsorption and release of chemical agents found in commercially available multi–purpose solutions (MPS) were evaluated with contact lenses to determine the effect on corneal staining and subjective symptoms. Methods:A series of pilot research studies were conducted as a 2–week, prospective clinical trial, using a double–masked, randomized, crossover design. Adapted lens wearers wore hydrogel (Group II or Group IV) or silicone–hydrogel contact lenses for a maximum of 1; 2 or 4; 6 or 8 hours each day. New lenses were dispensed for each wear period. Prior to wear, lenses were presoaked in Alcon OPTI–FREE® MPDS [with POLYQUAD® (Polyquaternium–1)], Bausch & Lomb ReNu MultiPlus® MPS [with DYMED® (Polyaminopropyl biguanide)], CIBA Vision SOLO–care® PLUS MPS (with Polyhexanide), or AMOTM Complete® MoisturePLUS MPS (with Polyhexamethylene biguanide) for 12 hours overnight. At the end of each wearing period subjects rated comfort and ocular symptoms. The ocular surface was examined at baseline and after lens removal with fluorescein. The cornea was divided into five zones and evaluated according to its type (grades 0–4) and area (0–100%). The uptake of chemical agents from new, unworn control lenses was determined in vitro by UV spectroscopy. Results: Clinically significant levels of relatively asymptomatic corneal staining were observed at 1 and/or 2 hours when subjects wore the Group I and Group II lenses soaked in the PHMB–based systems. The PHMB systems showed greater incidents of staining (56–80%, Group I; 80–95%, Group II) than the POLYQUAD (12–30%, Group I; 3–35%, Group II) group. All signs were reduced or not measurable after 6–8 hours. When subjects used the Polyquad–based solution with the lens groups I, II, and IV, only minimal staining was observed at 1 and 2 hours of wear. Preliminary results from the in vitro experiments demonstrated that continued cycling was associated with uptake of PHMB, Aldox®, Tetronic 1304 and 1107 into the lenses. Conclusions: These preliminary data indicate that subjects who wear Group II hydrogel or Group I silicone–hydrogel lenses soaked in PHMB–based systems on a daily wear basis, may exhibit clinically meaningful corneal staining during the first few hours after insertion. Practitioners who fit these lens types should be aware of the potential ocular response without the associated subjective symptoms.
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