AIM:To compare the results of corneal cross-linking(CXL)with isotonic(IR)and hypotonic riboflavin(HR)in patients with keratoconus.

METHODS: Retrospective study of 29 eyes/keratoconus patients submitted to CXL, 15 eyes with application of IR(IR group)and 14 eyes with application of HR(HR group). The parameters analysed included(1-year follow-up): best corrected visual acuity(BCVA), sphere and cylinder, central and finer pachymetry, mean and maximum keratometry(Km and Kmax respectively), complications and progression.

RESULTS: An increase on the BCVA scale(LogMAR, logarithm of the minimal angle of resolution)was observed in the two groups: 0.26±0.57(IR)and 0.47±0.72(HR)before treatment, and 0.13±0.79(IR)and 0.29±1.52(HR)at the 1y. Only at 1y, the difference was statistically significant(P=0.018, group IR with higher BCVA). The central pachymetry(μm)decreased at 1mo in both groups, and increased in the following months: 497±28 μm(IR)and 432±14 μm(HR)before treatment, and 480±31 μm(IR)and 424±15 μm(HR)to the 1y. The thinner pachymetry(μm)presented the same evolution: 487±29 μm(IR)and 410±20 μm(HR)before treatment, and 468±33 μm(IR)and 413±13μm(HR)at 1y. Km and Kmax decreased in both groups(P>0.05). 6 eyes from each group presented transitory haze. No eye progressed to the 1y.

CONCLUSION:The use of hypotonic riboflavin seems to be a valid alternative for performing the traditional corneal cross-linking technique in eyes with a central corneal thickness of <400 μm.