[Characteristics of corneal topography in candidates for surgery for myopia].

Introduction: Videokeratography analyses the corneal anterior topography. It is necessary in refractive surgery to estimate the anatomical effect of the surgery and to eliminate early Keratoconus.

Methodology: Corneal anterior topography was studied on 70 consecutive patients (140 eyes) candidates for low myopia surgery (-1 to -6); 87 eyes were wearing regularly contact lenses. With the topographic analysis machine of EYESYS compagny, keratometry (Km) at 3 mm, astigmatism (delta K) at 3 mm, I-S value at 3 mm and 5 mm according to Rabinowitz method were measured in each eye.

Results: The average keratometry was 43.50 +/- 1.87 D. The average astigmatism was 0.909 +/- 0.75 D. 51 eyes presented an asymmetric corneal and among them 32 ware contact lenses regularly; 8 eyes out of 140 (6%) presented the association of an high central Keratometry value (> or = 47 D) and corneal asymmetry (I-S > 0.5 value).

Comments: The incidence of Keratoconus is higher in a candidate population for refractive surgery by self-selection. Its frequency is difficult to evaluate accurately because of the present limits for the diagnostic measures. In this population, it seems to represent about 6%.

Conclusion: The videokeratography before refractive surgery is necessary to reveal corneal anterior topography abnormalities and to eliminate early Keratoconus.