Dear Editor:

We would like to thank De Bernardo et al. for replying to our article about the effects of accelerated corneal crosslinking on the ocular response analyzer waveform-derived parameters in patients with progressive keratoconus.

The name of our study is not “Topographic parameters evaluation before and after accelerated corneal crosslinking in progressive keratoconus”. Our aim was to evaluate the effect of accelerated corneal crosslinking (CXL) on corneal biomechanics, based on ocular response analyzer-waveform derived parameters, in patients with progressive keratoconus. Therefore, we discussed changes in corneal biomechanics rather than topographic changes after CXL treatment.

De Bernardo et al. stated that corneal volume should be much more sensitive than the methods we used to assess potential keratoconus progression. However, this assertion is not supported by published studies. Therefore, we defined progression as an increase in the diopter (D) value of the maximum keratometry 1.0 over a period of three months in children and of six months in adults^(1-3).

Also De Bernardo et al. indicated that assessing the astigmatic axis changes is a requirement to estimate the astigmatic correction properly. As they have stated in their own work, the advantage of the method described by Calossi⁽⁴⁾ is the simplicity of a computer program using vectorial analysis of the refractive changes induced by surgery. However, surgically induced, refractive changes are not the subject of our study, and we think that they are sufficient to show spherical and cylindrical refractive changes as in many CXL studies.

We analyzed crosslinking-treated eye parameters in our study, and studies evaluating the effect of CXL treatment on the cornea, do not need to choose sides^(5-7).

Murat M. Uzel et al.

REFERENCES

1. Mathews PM, De Rojas JO, Rapuano PB, Zemsky CJ, Florakis GJ, Trokel SL, et al. Correlation of Scheimpflug densitometry changes with clinical outcomes after corneal crosslinking. J Cataract Refract Surg. 2018;44(8):993-1002.

2. Gore DM, Leucci MT, Anand V, Fernandez-Vega Cueto L, Arba Mosquera S, Allan BD. Combined wavefront-guided transepithelial photorefractive keratectomy and corneal crosslinking for visual rehabilitation in moderate keratoconus. J Cataract Refract Surg. 2018;44(5):571-80.

3. Mazzotta C, Traversi C, Baiocchi S, Bagaglia S, Caporossi O, Villano A, et al. Corneal collagen cross-linking with riboflavin and ultraviolet a light for pediatric keratoconus: ten-year results. Cornea. 2018;37(5):560-6.

4. Calossi A, Verzella F, Penso A. Computer program to calculate vectorial change of refraction induced by refractive surgery. Refract Corneal Surg. 1993;9(4):276-82.

5. Lang PZ, Hafezi NL, Khandelwal SS, Torres-Netto EA, Hafezi F, Randleman JB. Comparative functional outcomes after corneal crosslinking using standard, accelerated, and accelerated with higher total fluence protocols. Cornea. 2019 Jan 23. doi: 10.1097/ ICO.0000000000001878. [Epub ahead of print]

6. Spadea L, Di Genova L, Tonti E. Corneal stromal demarcation line after 4 protocols of corneal crosslinking in keratoconus determined with anterior segment optical coherence tomography. J Cataract Refract Surg. 2018;44(5):596-602.

7. Fischinger I, Seiler TG, Santhirasegaram K, Pettenkofer M, Lohmann CP, Zapp D. Corneal crosslinking (CXL) with 18-mW/cm2 irradiance and 5.4-J/cm2 radiant exposure-early postoperative safety. Graefes Arch Clin Exp Ophthalmol. 2018;256(8):1521-5.