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‘Abnormal’ corneal topography patterns more common than normal
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More than half the corneal topographies of refractive surgery candidates did not fall within the “normal” patterns of spherical or spherocylindrical error in a retrospective study of unoperated candidates. The study authors noted that it is difficult to know “where to draw the line between reasonable and risky” for corneal refractive surgery in candidates with lower steep corneal patterns that might indicate developing keratoconus.
David Varssano, MD, and colleagues retrospectively analyzed the videokeratographies of 100 refractive surgery candidates who had not undergone surgery. Their corneal topographic patterns were computed by videokeratographer software and analyzed using statistical software.
The 100 potential refractive surgery candidates included 41 women and 59 men; average age was 32, with a range from 17.5 to 63.5 years. A total of 200 eyes were analyzed. The topographic patterns were spherical (36 eyes), spherocylindrical (60), upper steep (32), lower steep (43), irregular astigmatism (9), decentered (3), suspected keratoconus (11) and probable keratoconus (6 eyes).
Topography results alone were the reason for rejection of 27 eyes from surgery. After consideration, the 43 eyes with a “lower steep” pattern were also rejected, the researchers said.
The authors noted that, of the nine software-calculated indices, only “keratoconus index” could distinguish between spherocylindrical and lower steep patterns.
The study is published in the August issue of Cornea.