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B. Vasudevan, T.L. Simpson, J.G. Sivak; Refractive Index of the Bovine Cornea . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2552.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Given the refractive importance of the human cornea, surprisingly little attention has been directed to the study of local variations in corneal index. This study addresses this issue Methods: Fifty fresh (4 to 6 hours after enucleation) bovine corneas obtained from an abattoir were used for the study. Calibration measurements indicated little or no variation in refractive index over the 1 to 2 hour duration of the experiments. The refractive index of the central, nasal and temporal corneal epithelium was measured with a bench- top Abbe Refractometer. Refractive index of the central anterior and posterior stroma was also measured. Central corneal thickness of 10 additional bovine eyes were measured using Optical Coherence Tomography (OCT), A-scan ultrasonography and mechanical calipers. Results: The mean refractive index of the nasal, temporal and central corneal epithelium was 1.375(SD± 0.001), 1.374(SD± 0.002), and 1.376(SD± 0.003), respectively. The mean refractive indices of the central anterior and posterior stroma were 1.373(SD ±0.002) and 1.370(SD± 0.003), respectively. OCT showed higher values of central corneal thickness, in comparison to A-scan and calipers. As in the case of refractive index, there is no effect of duration of the experiment on these readings. Conclusions: There are small but significant local differences in the refractive index of the bovine cornea when comparing the center and periphery. Also, the refractive index of the epithelium is higher than that of the anterior and posterior stroma. These variations support earlier work indicating that local corneal index variation may be important in calculations related to human refractive surgery.
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