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Safety and Efficacy of Sequential Intracorneal Ring Segment Implantation and Cross-linking in Pediatric Keratoconus
CORRESPONDENCE Safety and Efficacy of Sequential Intracorneal Ring Segment Implantation and Cross-linking in Pediatric Keratoconus
(5 out of 12) reached a 4-year follow-up, making the statistical evaluation very difficult, even more so if we take into account that in some patients both eyes were evaluated and in others only 1 eye, introducing in this way a bias in the study.5 MADDALENA DE BERNARDO
EDITOR: WE READ WITH GREAT INTEREST THE ARTICLE BY
PALMIRO CORNETTA
Abdelmassih and associates1 about safety and efficacy of sequential intracorneal ring segment implantation and cross-linking in pediatric keratoconus published in the Journal. The authors are to be congratulated for their interesting idea, but we would like to make some comments. The authors analyzed the astigmatic correction achieved with this treatment, but unfortunately they forgot to perform the vectorial analysis that could help to better understand the corneal astigmatic changes induced by the treatment.2,3 In fact, without this evaluation it is very difficult to understand if the spherical changes are attributable to a real refractive correction or to a misalignment of the cylindrical correction that, as is well known, will result in a cylinder undercorrection and a spherical change.4 In Tables 2 to 5, which report the visual, refractive, and topographic parameters, there are the mean and standard deviation, but the authors did not report the ranges of the evaluated parameters that could have given further information on the effect of the treatment. Furthermore, we agree with the authors that more cases examined over a longer follow-up period are needed to validate their results because the number of examined patients was very low and fewer than half of the patients
Salerno, Italy
0002-9394/$36.00 http://dx.doi.org/10.1016/j.ajo.2017.06.039
©
2017
NICOLA ROSA
FUNDING/SUPPORT: NO FUNDING OR GRANT SUPPORT. Financial Disclosures: The following authors have no financial disclosures: Maddalena De Bernardo, Palmiro Cornetta, and Nicola Rosa. The authors attest that they meet the current ICMJE criteria for authorship.
REFERENCES
1. Abdelmassih Y, el-Khoury S, Dirani A, et al. Safety and efficacy of sequential intracorneal ring segment implantation and cross-linking in pediatric keratoconus. Am J Ophthalmol 2017;178:51–57. 2. Calossi A, Verzella F, Penso A. Computer program to calculate vectorial change of refraction induced by refractive surgery. Refract Corneal Surg 1993;9(4):276–282. 3. Alpins N. Astigmatic analysis by the Alpins method. J Cataract Refract Surg 2001;27(1):31–49. 4. Rosa N, De Bernardo M, Romano MR, et al. Analysis of photoastigmatic keratectomy with the cross-cylinder ablation. Indian J Ophthalmol 2012;60(4):283–287. 5. Karakosta A, Vassilaki M, Plainis S, et al. Choice of analytic approach for eye-specific outcomes: one eye or two? Am J Ophthalmol 2012;153(3):571–579.e1.
ELSEVIER INC. ALL
RIGHTS RESERVED.
1
(5 out of 12) reached a 4-year follow-up, making the statistical evaluation very difficult, even more so if we take into account that in some patients both eyes were evaluated and in others only 1 eye, introducing in this way a bias in the study.5 MADDALENA DE BERNARDO
EDITOR: WE READ WITH GREAT INTEREST THE ARTICLE BY
PALMIRO CORNETTA
Abdelmassih and associates1 about safety and efficacy of sequential intracorneal ring segment implantation and cross-linking in pediatric keratoconus published in the Journal. The authors are to be congratulated for their interesting idea, but we would like to make some comments. The authors analyzed the astigmatic correction achieved with this treatment, but unfortunately they forgot to perform the vectorial analysis that could help to better understand the corneal astigmatic changes induced by the treatment.2,3 In fact, without this evaluation it is very difficult to understand if the spherical changes are attributable to a real refractive correction or to a misalignment of the cylindrical correction that, as is well known, will result in a cylinder undercorrection and a spherical change.4 In Tables 2 to 5, which report the visual, refractive, and topographic parameters, there are the mean and standard deviation, but the authors did not report the ranges of the evaluated parameters that could have given further information on the effect of the treatment. Furthermore, we agree with the authors that more cases examined over a longer follow-up period are needed to validate their results because the number of examined patients was very low and fewer than half of the patients
Salerno, Italy
0002-9394/$36.00 http://dx.doi.org/10.1016/j.ajo.2017.06.039
©
2017
NICOLA ROSA
FUNDING/SUPPORT: NO FUNDING OR GRANT SUPPORT. Financial Disclosures: The following authors have no financial disclosures: Maddalena De Bernardo, Palmiro Cornetta, and Nicola Rosa. The authors attest that they meet the current ICMJE criteria for authorship.
REFERENCES
1. Abdelmassih Y, el-Khoury S, Dirani A, et al. Safety and efficacy of sequential intracorneal ring segment implantation and cross-linking in pediatric keratoconus. Am J Ophthalmol 2017;178:51–57. 2. Calossi A, Verzella F, Penso A. Computer program to calculate vectorial change of refraction induced by refractive surgery. Refract Corneal Surg 1993;9(4):276–282. 3. Alpins N. Astigmatic analysis by the Alpins method. J Cataract Refract Surg 2001;27(1):31–49. 4. Rosa N, De Bernardo M, Romano MR, et al. Analysis of photoastigmatic keratectomy with the cross-cylinder ablation. Indian J Ophthalmol 2012;60(4):283–287. 5. Karakosta A, Vassilaki M, Plainis S, et al. Choice of analytic approach for eye-specific outcomes: one eye or two? Am J Ophthalmol 2012;153(3):571–579.e1.
ELSEVIER INC. ALL
RIGHTS RESERVED.
1