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M. Guillon, C. Maissa; The Effect of Optimising Silicone Hydrogels Key Physical Properties on Extended Wear Clinical Performance . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2382.
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ACUVUE ® ADVANCETM with HYDRACLEARTM (galyfilcon A) (Dk=60) a non–coated silicone hydrogel was designed to incorporate a balance of various clinically relevant physical properties (e.g rigidity, surface wetting, and oxygen) for daily wear. O2Optix (lotrafilcon B) a plasma surface treated silicone hydrogel design is focused on higher oxygen transmissibility (Dk=110) for daily and extended wear. Both lenses, which have a higher oxygen transmissibility than current hydrogels used for extended wear, are CE marked for such application. The purpose of the investigation was to test the extended wear clinical performance in terms of ocular tissue tolerance and on eye wettability.of these two silicone hydrogel materials.
The investigation was a bilateral, group controlled, randomised, prospective multisite investigation of three month duration. The subjects wore the contact lenses for up to 6 nights and 7 days without removal and the contact lenses were replaced weekly.
The investigation carried out on current contact lens wearing subjects (lotrafilcon B n=57, Galyfilcon A n=49) led to the following results: i. A similarly good tolerance was achieved for the two contact lens types, in particular, corneal staining was judged slight or absent in the majority of cases.
ii. lotrafilcon B produced marginally more limbal hyperaemia than galyfilcon A (p = 0.099; Slight or less lotrafilcon B 53.0% Galyfilcon A 58.2%; Mild or worse lotrafilcon B 26.5% Galyfilcon A 14.0%)
iii. Conjunctival indentation was significantly (p=0.001 to <0.001) worse with lotrafilcon B than with galyfilcon A; the differences were associated with a significantly lower incidence of no indentation with lotrafilcon B than Galyfilcon A (No indentation lotrafilcon B 34.3%; galyfilcon A 54.7%).
iv. The tear film structure at the contact lens front surface was significantly better for Galyfilcon A than lotrafilcon B. The lipid layer was thicker for Galyfilcon A (p=0.001) with in particular a lower incidence of inefficient, transient patterns was greater (lotrafilcon B 45.8%, galyfilcon A 19.4%). Similarly the aqueous layer was thicker (p=0.001) with a greater incidence of layers of normal thickness (lotrafilcon B = 36.1%, galyfilcon A = 51.6%).
The results showed that galyfilcon A achieved a better clinical physiological performance than lotrafilcon B. The higher oxygen transmissibility of the latter did not produce superior corneal physiological benefits but the higher silicone content lead to more unwanted limbal mechanical effects, due to higher material rigidity, and poorer tear film structure.
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