We thank Drs Ashar and Vadavalli for their interest in our article.
The inclusion criteria taken to indicate that keratoconus was progressive were at least 2 of the following parameters: age 10 to 36 years; UCVA/BSCVA deterioration > 0.50 diopters (D); Sph/Cyl increase > 0.50 D; K readings increase > 0.50 D; SAI/SI increase > 0.50 D; reduction in corneal thickness (thinnest point) ≥ 10 μm; and biomicroscope and confocal microscope evidence of “clear” cornea (absence of scar and Vogt striae). The worst eye was treated as first. Forty-four patients were enrolled in the first 6 months and this was followed by 48 months of minimum follow-up by the same operators. In vivo scanning laser confocal microscopy provided a reliable preoperative and postoperative measurement of mean corneal thickness in all patients, confirming that pachymetry after cross-linking does not significantly change. Postoperative pachymetric underestimation provided by the white light source involved all series (44 patients). Twenty-two patients were reexamined with the partially coherent anterior segment tomography, demonstrating that there was a not statistically significant reduction in corneal pachymetry after cross-linking treatment. An insight into pachymetric evaluation after cross-linking is now in press by the same authors of the present article. Physiological endothelial cell loss is obviously a variable parameter. Endothelial cell loss of 0.6% per year was referred to normal nonoperated corneas. We want to remark here that the percentage of endothelial cell loss by a mean of 2% per year referred in our study to keratoconic corneas often subjected to contact lens wear and treated by riboflavin ultraviolet A cross-linking (operated pathologic corneas, not normal corneas). In our long-term experience with this treatment, endothelial cell loss remains under the values reported in literature for operated eyes.
Young age represents the most important negative prognostic factor for keratoconus progression with higher risk of keratoplasty. In our experience, young patients under 18 years have the higher progression rate, but also reached the best functional result after cross-linking. Patients under 18 years represent 29% of our treatments. Patients between 19 and 26 years represent 58% and patients over 27 years, 13%. A comparative analysis of cross-linking results in different age groups was presented by us in the last World Ophthalmology Congress (A. Caporossi, C. Mazzotta, communication at WOC Berlin, June 6, 2010) showing that patients under 18 years old reached the best functional results. Our study was not masked but a prospective nonrandomized open trial. Uncorrected visual acuity and best spectacle-corrected visual acuity improvements were statistically significant after cross-linking as was demonstrated. It is obvious that cross-linking is not a refractive procedure but a stabilizing treatment against ectasia progression with positive refractive implications due to collagen lamellae compaction, keratoconic apex flattening, and improved corneal symmetry. To date, we have experience of more than 450 treatments in Siena with an evidence-based long-term efficacy of the treatment in progressive keratoconus, confirming all the data published in the article.