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David Alonso-Caneiro, Alyra J. Shaw, Michael J. Collins; Using Anterior Segment Optical Coherence Tomography To Assess Limbal/Scleral Changes After Contact Lens Wear. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4729.
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Traditionally, instruments for measuring ocular surface topography are limited to measurement of the corneal surface and cannot measure out to the limbus or sclera. Consequently, corneal changes after contact lens wear are well documented, however little is known about the effect of contact lenses on the limbal/scleral region. Anterior OCT allows imaging of the limbus and sclera to observe the influence of contact lens wear on this region.
Nasal and temporal horizontal, 5 mm B-scans (centred on the limbus) were taken for 6 subjects using a commercial SOCT before and after 6 hours of contact lens wear for 3 different lenses (hydrogel sphere, silicone hydrogel sphere and silicone hydrogel toric), with at least 1 day of no contact lens wear between lenses. Iris features and alignment techniques were used to register 6 (3 pre and 3 post) OCT scans for each subject and condition. To assess the shape of the ocular surface, points were manually selected along the first hyper-reflective layer. Each scan was divided into corneal and limbal/scleral regions using the termination of Bowman’s layer as the marker for the division point. The RMS error was calculated to describe the variation in the surface profile between pre and post contact lens wear (Figure: overlaid B-scans indicating the first hyper-reflective layer variations).
There was only a slight variation in the profile of the corneal region due to contact lens wear (mean RMSE = 3.8μm) while a greater variation for the limbal/scleral region was observed (mean RMSE = 9.3μm). The variations were significantly greater for the nasal compared with the temporal location (p<0.05). Comparing the different contact lenses, the mean RMS errors were significantly greater for the toric lens (14.3μm) compared with the two spherical lenses (8.6μm silicone hydrogel, 8.7μm hydrogel), but only for the nasal location (p<0.05).
Significant changes in the limbal/scleral region were observed after contact lens wear while there were limited corneal changes. It has been shown that OCT is a powerful tool that can be used to observe the effects of contact lenses on the ocular surface. Further work is needed to understand the influence of ocular surface and contact lens parameters on these changes.
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