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D. De Brouwere, G. Sgouros, H.S. Ginis, I.G. Pallikaris; A Physical Model of Corneal Scatter Following Refractive Procedures Based on Glass Microspheres Suspended in Carbomer Gel . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2990.
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© ARVO (1962-2015); The Authors (2016-present)
Corneal scatter following laser refractive surgery is increased and possibly has negative impact to visual performance. The purpose of the present study is to develop a physical model having similar scattering properties with the postoperative cornea and to use this model as a reference scatterer in single and double – pass measurements.
Glass microspheres (Jaygo Inc.) with diameter ranging from 1 to 20 microns were dissolved in 0.3% carbomer gel (Thilogel, Alcon Hellas) at different concentrations. The angular scattering distribution of the microspheres was measured by means of a single pass experiment. The ballistic ratio (the percentage of non scattered light) was measured at different concentrations for a sample thickness of 500 microns. The samples were placed between glass plates and mounted in front of a model eye to acquire double pass images with the WaveLight WaveFront Analyzer. The double – pass ballistic ratio was estimated by image analysis in Matlab. Finally, the mass concentration of the microsphere solution and ballistic ratio measured in the single pass and in the double pass experiment were correlated.
The scattering distribution corresponds well to previously estimated distributions for keratocytes. Full width at half maximum (FWHM) of the distribution was 4.2 degrees. A function was derived to correlate the concentration of the microspheres and the ballistic ratio of the sample (BR=1–9.441*C(1/2)). A strong correlation between the double pass and the single pass estimates of the ballistic ration was found.
Glass microspheres suspended in carbomer gel can be used to create scatter distributions similar to those reported for the cornea following laser refractive surgery. The percentage of scattered light (1–BR) can be controlled by varying the concentration of microspheres. The proposed physical model can be used either for phsychophysical measurements or as reference scatterer for the calibration of devices designed to measure corneal scatter.
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