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PJ Ousley, MA Terry; Use Of A Portable Topography Machine For Screening Donor Tissue For Prior Refractive Surgery . Invest. Ophthalmol. Vis. Sci. 2002;43(13):150.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: More than half of the corneas procured for transplantation in the U.S. are procured as corneoscleral rims at the donor site, not as whole eyes. We are aware of no commercially available instrument that can objectively evaluate corneoscleral rims for the presence of refractive surgery. We therefore investigated whether a portable, hand-held topography unit could be used to screen donor eye tissue for prior corneal refractive surgery, either in the field before eye or rim removal or in the lab on whole globes. Methods: 22 presumed normal control donor eyes were measured with the Keratron "Scout" portable topography machine at the donor site before whole eye enucleation ("Field") and again in the lab after enucleation ("Lab"). 12 known refractive surgery eyes (six eyes that had undergone RK before death, four eyes with LASIK for myopia, and two eyes with hexagonal keratotomy for hyperopia) were also measured (in the lab only). Mean corneal curvature of the periphery (7 mm zone) was compared to the curvature of the central cornea (3 mm zone) in each eye of both the control and refractive surgery groups. Results: "Field" and "Lab" measurements of the control eyes were not significantly different and correlated well (r=.84; P<.001). The control eyes had a normal prolate shape, with the corneal curvature less in the periphery than in the center (mean difference -1.77±0.73 diopters in the lab). The RK and LASIK eyes were oblate, with the corneal curvature greater in the periphery than in the center (mean difference +1.99±2.09 diopters; P<.001 compared to control eyes). The hexagonal keratotomy eyes were steeper in the center than the control eyes, resulting in a more extreme prolate shape and a larger negative difference between the periphery and the center (mean difference -4.90±3.97 diopters; P<.05 compared to control eyes). Conclusion: The Scout topography unit can be used to measure corneal topography at the donor site, with the results comparing well to the corneal topography measured in the eye bank lab. Regional curvature differences between the periphery and the center could be used as a practical method for screening donor eyes for prior refractive surgery.
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