Backscattered light from the cornea before and after laser-assisted subepithelial keratectomy for myopia

Abstract

The anterior part of the corneal backscatter profile decreased significantly after LASEK. A significant reduction in forward light scatter was also seen, although it was not correlated to backward light scatter.

Evaluation of corneal optical properties in subjects wearing hydrogel etafilcon A contact lenses and the effect of administering mannitol-enriched sodium hyaluronate ophthalmic solution

“…Farris et al 14 and Korb and Exford 33 reported that this phenomenon was due to a localized epithelial response to CL wear, resulting in a focal increase of backscattered light. In our study, the corneal backscattered light in the epithelium (measured as peak intensity in this study) could be related to the distortion of the surface microstructure, 34 and the backscattered light in the stroma (measured as average intensity) could be related to local hydration. 15 , 35 …”

Corneal structure and transparency

“…Since then, techniques based on measuring the scattered rather than the transmitted light have been developed. These include Scheimpflug photography ( Smith et al., 1990 , Beckman Rehnman et al., 2011 , Rozema et al., 2011 ), video pachometry using a slit lamp ( Lohmann et al., 1992 , Connon et al., 2003 , Patel et al., 2007 ), confocal microscopy ( Jester et al., 2001 ) and optical coherence tomography ( Wang et al., 2004 , Hoffart, 2013 ). Most of these techniques detect back-scattered light.…”

“…Most of these techniques detect back-scattered light. Forward scatter has been measured using confocal microscopy ( Ginis et al., 2009 ), by making direct measurement in excised corneas ( De Brouwere et al., 2008 ) or by using stray light techniques on humans in vivo ( Van den Berg et al., 2013 , Patel et al., 2008 , Rozema et al., 2011 ) for which commercially equipment is available. In so-called Direct Compensation Stray Light measurements, a test field consisting of a dark circle split into left and right halves is surrounded by a bright ring-shaped flickering light, which serves as the glare source.…”

<p>Straylight As The Result Of Refractive Correction</p>

“…The results were consistent: post-operative straylight values in myopes after laser-assisted in situ keratomileusis (LASIK)/ laser-assisted epithelial keratomileusis (LASEK)10–14 or after phakic intraocular lens (pIOL) implantation15,16 were on average slightly lower than pre-operative straylight measurements. Assumptions were made that these improvements are the result of ill-tolerated contact lenses pre-operatively 13,15,16. Another factor that might have played a role in these findings is the effect of change in retinal image size due to correction of the refractive error.…”