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Jos J. Rozema, Carina Koppen, Marie-José B. Tassignon; Changes In Forward And Backward Light Scatter After Corneal Crosslinking. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5278.
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To study the changes in corneal transparency that occur after corneal crosslinking in keratoconus patients by measuring the forward and backward light scatter originating from the cornea. This is done for both the standard crosslinking procedure, as well as the transepithelial procedure.
This study includes 49 eyes of 36 keratoconus patients (age: 24.3 ± 8.6, range [12 - 46]), who were divided into two groups: 16 eyes that underwent standard crosslinking and 33 eyes that underwent transepithelial crosslinking. Forward light scatter was measured by means of the Oculus C-Quant. Backward light scatter was obtained by image analysis of 25 corneal Scheimpflug images as provided by the Oculus Pentacam. For each of these images the average backscatter profile in a zone of 1 mm diameter around the corneal apex was analyzed for profile shape and prevalence of grey values. A rough calibration of corneal depth was obtained by comparing the number of pixels in the central corneal backscatter profile with the central pachymetry. Both measurements were performed preoperatively and 6 months postoperatively.
The forward light scatter showed a statistically significant increase from 1.00 to 1.09 log units in the standard crosslinking group (paired t test, P < 0.01), and from 0.89 to 1.00 in the transepithelial group (P < 0.001). In standard crosslinking the backscatter profile increased significantly in the stromal region, roughly at a depth of 100-400 µm from the epithelium (P < 0.01). In transepithelial crosslinking statistically significant increases were found in the epithelial and anterior stromal layers up till a depth of 100 µm from the epithelium (P < 0.01).
Both the standard and transepithelial crosslinking techniques cause statistically significant increases in forward and backwards light scatter. Depending on the crosslinking technique used, these increases affect different parts of the backscatter profile: the stromal layer in the standard technique and the anterior stroma in the transepithelial technique. In both cases this corresponds with the corneal layers where the crosslinking effect is expected to occur.
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