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Krystal L. Schulle, James E. Walsh, Jan P. Bergmanson; The Scleral Contact Lens - A Viable UVR Filter. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6535.
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Scleral contact lenses larger than 15mm cover the entire cornea, limbus and palisades of Vogt and would therefore potentially be a useful blocker of ultraviolet radiation (UVR). The purpose of this study was to assess UVR transmittance of scleral lenses manufactured from buttons with UVR blocker formulated into the plastic with the objective of determining their efficacy as UVR protective ophthalmic devices.
A novel Ocean Optics USB4000 fiber optic spectrometer based instrument set up improves on classic spectrophotometer cuvette based methods, as the latter introduces up to four additional refracting and reflecting surfaces and absorbing media that lead to light losses not related to the test lens. With our design we measured the test lens/material by placing the detecting fiber directly behind the surface of the test object. The light source illuminated the front surface with a parallel test beam of light and was placed in close proximity to the optical element under test allowing a short beam path minimizing losses due to unwanted refraction, reflection and absorption of our parallel test beam. Test lenses, -3.00D (TruForm; Texas) were hexafocon A & B (Boston XO and XO2) with and without UVR blocker and hofocon A (TYRO-97) with blue handling tint but no UVR blocker. Three lenses from each group were measured.
The non-UVR blocking materials (hofocon A, hexafocon A), blue and clear tint, were close to 100% transparent to 300nm level or below. The hexafocon A & B with UVR blocker had similar absorption characteristics with 50% absorption at 374nm and opaque at 365nm. Center vs. periphery absorption characteristics were minimal or within 5%.
UVR blocking scleral contact lenses made from hexafocon A & B, are very close to ANSI Class 1 UVR blocking standard for ophthalmic devices, filtering out 99% of UVB and over 87% of UVA. We conclude that scleral contact lenses made from such a plastic formulation are viable UVR protective ocular devices, while the non-UVR blocking material offered little or no useful protection.
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