Use of a portable topography machine for screening donor tissue for prior refractive surgery

We investigated whether a portable, hand-held topography unit could be used to measure corneal topography either at the donor site or in the laboratory and whether the technology could be used to screen donor eye tissue for prior refractive surgery.

The corneal topography of 22 eyes of 12 normal donors was measured with the Keratron Scout portable topography machine before and after whole-eye enucleation. Field and laboratory measurements of central curvature, astigmatism, and the difference between the corneal curvature at the 7-mm and the 3-mm zone were compared. The 7-mm and 3-mm zone curvature differences were also used to screen for eyes that had undergone refractive surgery.

The mean central curvature of the normal eyes in the field [43.28 +/- 1.58 diopter (D)] was not significantly different from the mean curvature in the laboratory (43.52 +/- 1.72 D; p= 0.20). Field and laboratory astigmatism was 2.02 +/- 1.13 D and 1.64 +/- 1.38 D, respectively (p = 0.26, not significant). The eyes had a normal prolate shape, with the corneal power less in the periphery than in the center (mean difference between the 7-mm and 3-mm zone of -1.48 +/- 0.83 D in the field and -1.77 +/- 0.73 D in the lab; = 0.069). Field and laboratory measurements of corneal shape correlated well with each other. Eight of eight eyes with refractive surgery for myopia and one of two eyes with hexagonal keratotomy for hyperopia were outside 2 SD of the normal range.

The Scout can be used to measure corneal topography at the donor site and in the eye bank laboratory with comparable results. Regional power differences between the corneal periphery and center could be used as a method for screening donor eyes for prior refractive surgery.