Study on Orbscan-II corneal topography system in screening of early keratoconus

Objective To evaluate the important role of Orbscan-II corneal topography system in screening early keratoconus before excimer laser refractive surgery. Methods Orbscan-II corneal topography system was performed on 15 patients (27 eyes) before refractive surgery, to screen earlykeratoconus, whose BCVA satisfactory and slit-lamp microscope and keratometer’s examination were normal and were diagnosed clearly after 1-year follow-up survey. Results The increase of the center refractive power of the cornea, I-S value, SimK value, Diff value conduced to the diagnoses of early keratoconus. The following 5 indices helped to make the diagnosis of early keratoconus: (1) the center refractive power of the cornea 46.50 D; (2) difference of both center refractive power of cornea 1.50 D;(3) I-S value 1.50 D. (4) cornea thinnest thickness≤460 μm, difference of both eyes≥15 μm; (5) Diff value of anterior surface of cornea≥0.025, Diff value of posterior surface of cornea≥0.050. If more than two items above were abnormal, the patients should be followed up regularly. The diagnosis could be made if it developed further. Conclusion Orbscan-II is an effective method in screening of early keratoconus before refractive surgery.