PURPOSE: To assess and analyze the two-year results of corneal collagen cross-linking with riboflavin using ultraviolet-A light in the treatment of keratoconus and to evaluate the efficacy of this procedure. DESIGN: Retrospective study. METHODS: The preoperative and postoperative data of 58 eyes of 40 keratoconus patients were revised. The intervention was only conventional corneal collagen cross linking in an indicated keratoconus patient. The data included UCVA, BCVA, slit lamp examination, keratometry, refractometry, pachymetry and corneal topography. Postoperative follow up program was 1, 3, 6, 12, 24 months. RESULTS: The mean age was 16.9 ± 6.35 years (range 12-39 years) and the mean follow-up was 23.05 ± 1.55 months (range 12 to 30 months). Fifty-eight eyes of 40 patients with a follow-up of at least 24 months were analyzed. The preoperative values on the day of treatment were compared with postoperative values of the 24-month examination. This showed that BCVA improved at least one line in 53.4% (31/58) of eyes, remained stable in 36.2 % (21/58) of eyes (P=0.006) and decreased by only one line in 10.3 % (6/58). Astigmatism remained stable (within ± 0.50 D) in 86.2% (50/58) of eyes while decrease by a mean of 1.20 D 13.8 % in (8/58) of eyes. The K value of the apex decreased by a mean of 2.73 D in 65.5% (38/58) of eyes (P=0.004), remained stable (within ± 0.50 D) in 25.9% (15/58) of eyes and increase by 1.00 D in 8.6 % (5/58) of eyes. The maximum K value decreased by a mean of 2.47D in 55.1% (32/58) of eyes (P=0.004), remained stable (within ± 0.50 D) in 38% (22/58) of eyes and increase by 1.00 D in 6.9 % (4/58) of eyes. Corneal wave front analysis revealed that spherical and higher-order aberrations did not show significant variations in the follow-up period. The coma component showed a very significant reduction at six months after treatment and persisted throughout the follow-up period (P=0.003). CONCLUSION: This study proved that corneal cross-linking is beneficial as both visual preserving and visual improving procedures. K readings are the main indicator of success or failure of the procedure. Central corneal thickness can be an indicator of improvement, there is a reciprocal relationship between them. Best chance is for patients with corneal thickness more than 400 ?m. It is advised that the crosslinkologist should store the riboflavin in the refrigerator from +4° C to +8° C and discard it immediately after surgery. Use of steroid from the first postoperative day was helpful. Most postoperative visual improvement resulted from decrease of myopia whereas there was no remarkable improvement of astigmatism.