Computer-assisted videokeratography of corneal topography after radial keratotomy
S. J. Bogan, R. K. Maloney, C. D. Drews and G. O. Waring 3rd
Department of Ophthalmology, Emory University School of Medicine, Atlanta, GA 30322.
We used computer-assisted videokeratography to compare the topographies of
32 corneas from 23 subjects after radial keratotomy with those of 47 normal
corneas from 47 subjects controlled for age and preoperative keratometric
and refractive power. Three ophthalmologists independently classified
color-coded videokeratographs based on the color-coded pattern of dioptric
power distribution and the cross-sectional shape. Corneas that had radial
keratotomy exhibited a polygonal pattern not seen in normal eyes; this
occurred in 59% of corneas. All normal corneas demonstrated a
cross-sectional shape configuration that was steeper centrally than
peripherally; 79% of corneas after radial keratotomy had a shape that was
flatter centrally than peripherally. After radial keratotomy, the dioptric
power increased from the center to the periphery (radius of approximately
4.6 mm) by 2.8 +/- 2.2 diopters (mean +/- SD), with a sharp inflection zone
("paracentral knee") 2.7 mm from the center; normal corneas showed a smooth
decrease in power from the center to the periphery of 1.9 +/- 0.5 diopters.
