252 LETTERS

REFERENCE1. Miyake T, Kamiya K, Amano R, Iida Y, Tsunehiro S, Shimizu K.

Long-term clinical outcomes of toric intraocular lens implantation

in cataract cases with preexisting astigmatism. J Cataract Refract

Surg 2014; 40:1654–1660

Reply : We agree with Dr. Yeoh that completeremoval of the OVD is essential to prevent toricIOL rotation, as mentioned in our article. We in-

tended to completely remove the OVD in all cases, notonly the OVD anterior to the IOL but also the OVD thatlies beneath the implanted IOL, to prevent postopera-tive IOL rotation. Nevertheless, in 6 of 378 eyes(1.6%), the IOL rotated more than 20 degrees. In theseeyes, the axial length was 25 mm or longer, cornealastigmatism was with-the-rule (WTR), and the IOLsrotated relatively soon after surgery. In our experience,a large IOL rotation may occur in the early postopera-tive period in some eyes with relatively long axiallengths and WTR astigmatism even if the OVD thatlies beneath the IOL has been removed.dToshiyuki Miyake, MD, Kazutaka Kamiya, MD, PhD,Kimiya Shimizu, MD, PhD

Corneal stromal demarcation line afterhigh-intensity (accelerated) collagencrosslinking

In the discussion section of the article by Tomitaet al.1 regarding accelerated corneal collagen crosslink-ing (CXL), the authors stated that the corneal stromaldemarcation line was at the depth of approximately350 mm in the accelerated CXL group (3 minutes ofultraviolet-A [UVA] irradiation at 30 mW/cm2 inten-sity) and of approximately 380 mm in the conventionalCXL group (30 minutes of UVA irradiation at3 mW/cm2 intensity).1 Yet in the results section, theauthors stated that the mean corneal stromal demarca-tion line depth was 294.38mmG 60.57 (SD) for acceler-ated CXL and 380.78 G 54.99 mm for conventionalCXL, while they reported no statistically significantdifference in the corneal stromal demarcation linedepth between the 2 groups.

We think it is necessary topoint out that the authorsdonot provide any information regarding the identificationand depth measurement of the corneal stromal demar-cation line and that the between-group difference in themean corneal stromal demarcation line depth seems tobe remarkable (294 mm versus 380 mm) even thoughthe authors reported no statistically significantdifference between the 2 treatment groups.1 A study by

J CATARACT REFRACT SURG -

Touboul et al.2 showed that with accelerated CXL(3-minute treatmentwith 30mW/cm2UVA irradiation),the corneal stromal demarcation line was generallylocated between depths of 100 mm and 150 mm. Inaddition, in our recent article,3 we showed that thecorneal stromal demarcation line was significantlydeeper after standard CXL (30-minute treatment with3 mW/cm2 UVA irradiation) than after high-intensityCXL (10-minute treatmentwith 9mW/cm2UVA irradi-ation). Specifically, the corneal stromal demarcationline was 350.78 G 49.34 mm after standard CXL and288.46G 42.37 mm after high-intensity CXL.

It has been suggested that the corneal stromaldemarcation line is correlated to the effective depthof the CXL.4 The findings of our recent study indicatethat high-intensity CXL could provide less effectiveCXL as the corneal stromal demarcation line depthwas shallower after high-intensity CXL than after stan-dard CXL.3 Moreover, the corneal stromal demarca-tion line depth may be different depending on theCXL protocol (time and UVA irradiation intensity)and unknown factors may also play a role. Since ithas not been established which depth of the cornealstromal demarcation line is sufficient for effectiveand safe CXL, we believe that the corneal stromaldemarcation line depth of the standard CXL shouldbe the gold standard target after every high-intensity(accelerated) or modified CXL treatment protocol.

Michael A. Grentzelos, MDGeorge D. Kymionis, MD, PhD

Heraklion, Crete, Greece

Editor's Note: The lack of a statistical power analysis is aweakness that limits the interpretation of the nonsignificantresults.

REFERENCES1. Tomita M, Mita M, Huseynova T. Accelerated versus conven-

tional corneal collagen crosslinking. J Cataract Refract Surg

2014; 40:1013–1020

2. Touboul D, EfronN, Smadja D, PraudD,Malet F, Colin J. Corneal

confocal microscopy following conventional, transepithelial, and

accelerated corneal collagen cross-linking procedures for kerato-

conus. J Refract Surg 2012; 28:769–776

3. Kymionis GD, Tsoulnaras KI, Grentzelos MA, Plaka AD,

Mikropoulos DG, Liakopoulos DA, Tsakalis NG, Pallikaris IG.

Corneal stroma demarcation line after standard and high-intensity

collagen crosslinking determined with anterior segment optical

coherence tomography. JCataractRefractSurg2014; 40:736–740

4. Kymionis GD, Grentzelos MA, Plaka AD, Tsoulnaras KI,

Diakonis VF, Liakopoulos DA, Kankariya VP, Pallikaris AI. Corre-

lation of the corneal collagen cross-linking demarcation line using

confocal microscopy and anterior segment optical coherence

tomography in keratoconic patients. Am J Ophthalmol 2014;

157:110–115

VOL 41, JANUARY 2015