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Posters | Archive
October 2007


Radial Power Profiles of Single Vision Silicone Hydrogel Lenses

Andrew Roy, Craig A. Woods, Desmond Fonn


: There are currently five single vision silicone hydrogel lenses available (lotrafilcon A lotrafilcon B, balfilcon A, galyfilcon A, senofilcon A), each produced using a different manufacturing process or material. Anecdotal practitioner commentary would suggest some of these silicone hydrogel lenses perform differently with respect to visual performance. This study was designed to compare the power profile of these silicone hydrogel lenses available on the market and to investigate any differences.

Methods: Two different labelled powers (-3.00D and -6.00D) were measured of the 5 study lens designs using the Rotlex Contest Plus interferometer. The radial power profiles were measured over a 3mm radius for each lens design.

Results: The radial power profiles of the silicone hydrogel lenses varied, although some common trends were identified.  The lotrafilcon A design had less negative spherical aberration than all other lens designs regardless of lens power (p<0.01). Balafilcon A had more negative spherical aberration but only for the -3.00D designs (p<0.01). The lotrafilcon B design had the most negative spherical aberration in the -6.00D (p<0.01).  Considering a nominal value for lens power (measured 1.75mm from the lens centre) galyfilcon A and senofilcon A were over powered for both -3.00D and -6.00D, all the other designs were within a ±0.25D tolerance.

Conclusion: A large variation in the spherical aberration may be the reason for the reported variations in vision measures for some of the silicone hydrogel lenses. Despite similar labelling, different silicone hydrogel contacts lens designs yield a wide spectrum of power profiles. Of the ten lenses measured, four were over powered compared to the labelled value for the nominal vertex power.

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