The transepithelial riboflavin solution should contain no dextran, but it should include 0.01% BAC and 0.44% NaCl to promote the permeability of riboflavin through the epithelium, resulting in a sufficient concentration of riboflavin in the corneal stroma.

We appreciate having another chance to point out that corneal CXL is a clinical procedure with complications and failures, and we are grateful that Kymionis et al. drew attention to more infrequent complications that were not mentioned in our discussion.We fully agree that an impact on the cornea such as CXL may initiate a recurrence of herpes keratitis and in cases with an ocular herpes history, systemic antimetabolite therapy is clearly indicated. Stimulation of an inflammatory reaction such as diffuse lamellar keratitis after LASIK by CXL is also not a surprising side effect, and we agree that topical steroids should precede CXL in cases of iatrogenic keratectasia.Please keep in mind: CXL is a technically easy procedure but represents a significant impact on the eye treated.dTobias Koller, MD, Theo Seiler, MD, PhD LETTERS

PURPOSE: To evaluate the safety, efficacy, and stability of LASIK, using positive cylinder and negative sphere nomograms in sequence (sequential ablation) to correct mixed astigmatism. METHODS: This prospective study included 40 eyes of 20 patients with mixed astigmatism. Patients underwent bilateral sequential ablation LASIK using the Technolas 217 excimer laser (Bausch & Lomb Surgical, Rochester, NY). The main outcome measures, uncorrected visual acuity (UCVA) and best spectacle-corrected visual acuity (BSCVA), were evaluated 3 and 12 months after surgery. RESULTS: Preoperative astigmatism ranged from + 1.75 to +6.00 diopters (D) and negative sphere from -0.50 to -3.00 D. The postoperative refraction at 3 months remained unchanged at 1 year postoperative in all patients. A total of 32 (80%) eyes showed no significant residual astigmatism (<0.50 D); the remaining 8 (20%) eyes had 0.50 to 1.00 D of residual astigmatism. Residual negative sphere was present in 2 eyes of 2 patients with a planned monovision target. In the remaining 38 (95%) eyes, no significant residual negative sphere was present. Sixteen (40%) eyes had one line of improvement in BSCVA. No eye lost lines of visual acuity. The efficacy index shows that uncorrected vision after surgery is equal or better than corrected vision before surgery. Less corneal tissue is removed and fewer laser spots are required compared to other techniques for the correction of mixed astigmatism. CONCLUSIONS: The sequential ablation approach to the correction of mixed astigmatism was efficacious, safe, and stable 1 year after surgery. [J Refract Surg. 2006;22:787-794.]

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Purpose: The aim of this study was to investigate the possibility of delivering riboflavin into the corneal stroma for cross-linking with the aid of a tensioactive substance (benzalkonium chloride), without removing the epithelium, in order to make corneal cross-linking (CXL) a less invasive technique. Methods: Rabbit corneas were cross-linked in vivo without removal of the epithelium, using riboflavin solution 0.1% to which benzalkonium chloride solution was added. The corneas were then examined by light and electron microscopy for evidence of collagen cross-linking. Control non-treated eyes were compared with treated ones. Results: The treated corneas were stiff and yellow in colour, and on light microscope examination they showed straight compact collagen fibres in comparison with control corneas in approximately 50% of the corneal thickness. Electron microscopy revealed regular arrangement of fibres in the outer 200µm with reduced inter-fibre distances in the treated corneas, but with no noticeable differences between control and treated corneas in the inner 100µm. Conclusion: The addition of benzalkonium chloride to the riboflavin solution facilitated its entry to the corneal stroma through the epithelium, and CXL occurred without epithelium removal. KeywordsBenzalkonium chloride, collagen fibres, corneal cross-linking, epithelium, riboflavin, ultraviolet A Disclosure: The authors have no conflicts of interest to declare. Materials and MethodsThe cross-linking was carried out at the Zooprophylaxis Institute,

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