1281LETTERS

using the Camellin formula2 when the patient clinicalhistory is unknown.1 With the Camellin formula, it ispossible to calculate the radius of curvature of theposterior corneal surface based on the measurementof the curvature radius of the anterior corneal surface,corneal pachymetry, and a series of pachymetry mea-surements performed in a 3.0 mm circular zone.1 Itthen is possible to obtain the relative keratometricrefractive index without knowing the surgicallyinduced refractive change. Therefore, unless we havemisunderstood this, the Camellin–Calossi formuladoes not always require preoperative data.dMegumi Saiki, PhD, Kazuno Negishi, MD, Naoko Kato,MD, Rika Ogino, Hiroyuki Arai, MD, Ikuko Toda, MD,Murat Dogru, MD, Kazuo Tsubota, MD

REFERENCES1. Camellin M, Calossi A. A new formula for intraocular lens power

calculation after refractive corneal surgery. J Refract Surg

2006; 22:187–199

2. Camellin M. Proposed formula for the dioptric power evaluation

of the posterior corneal surface. Refract Corneal Surg 1990; 6:

261–264

Corneal collagen crosslinking and herpetickeratitis

In their recent case report, Ferrari et al.1 analyzed thecase of a 30-year-old womanwho had corneal collagencrosslinking (CXL) for the management of recurrentherpetic keratitis. The intervention was unsuccessful,and 15 days after the initial treatment, tectonic pene-trating keratoplasty was required due to excessivethinning and melting.

It is known that herpes simplex virus (HSV) reacti-vation is triggered by a variety of factors such as stress,immunosuppression, and laser surgery. Presumably,the use of ultraviolet-A light is a stimulus for the virus,as the authors mention, and therefore CXL does notalways represent a treatment option for this kind ofinfection.

Most important, there are 2 cases in the literature(Kymionis et al.2 and Yuksel et al.3) that describe theoccurrence of herpetic keratitis following CXL treat-ment for progressive keratoconus. In both cases, therewas no history of HSV and topical and oral treatmentswere required to control the infection.

Therefore, even though CXL has been proposed asan alternative treatment for infectious keratitis,4 itshould be applied in specific cases, not in every case in-dependent of the underlying cause of the infection. Tosupport this argument, there are no reports demon-strating treatment of herpetic keratitis with CXL.

J CATARACT REFRACT SURG -

Careful patient selection is of extreme importance,especially when testing a relatively new technique, tominimize possible complications and provide a satis-fying result.

George D. Kymionis, MD, PhDDimitra M. Portaliou, MD

Heraklion, Crete, Greece

REFERENCES1. Ferrari G, Iuliano L, Vigan�oM, Rama P. Impending corneal perfo-

ration after collagen crosslinking for herpetic keratitis. J Cataract

Refract Surg 2013; 39:638–641

2. Kymionis GD, Portaliou DM, Bouzoukis DI, Suh LH, Pallikaris AI,

Markomanolakis M, Yoo SH. Herpetic keratitis with iritis after

corneal crosslinking with riboflavin and ultraviolet A for keratoco-

nus. J Cataract Refract Surg 2007; 33:1982–1984

3. Yuksel N, Bilgihan K, Hondur AM. Herpetic keratitis after corneal

collagen cross-linking with riboflavin and ultraviolet-A for progres-

sive keratoconus. Int Ophthalmol 2011; 31:513–515

4. Iseli HP, Thiel MA, Hafezi F, Kampmeier J, Seiler T. Ultraviolet A/

riboflavin corneal cross-linking for infectious keratitis associated

with corneal melts. Cornea 2008; 27:590–594

Reply : We thank Dr. Kymionis and Dr. Portalioufor their insightful comments and fully agree withwhat they say. Our case is different from the 2 previ-ously described (Kymionis et al. and Yuksel et al.),since herpetic keratitis did not appear de novo aftertreatment, triggered as Kymionis and Portaliousuggest by UVA exposure, but was already present.We imagine that the colleague who treated ourpatient decided to use crosslinking in this case, basedon the reported effects of this procedure. Heprobably aimed to kill the virus, stop melting, andstrengthen the stroma, thus preventing perforation.However, we should bear in mind that CXL transito-rily deprives the corneal tissue of cells and nerves,although we cannot exclude a positive effect on ma-trix metalloproteinase and inflammatory cells. Yet,in this case the effect of CXL on the inflammatory re-action was unbalanced and predisposed to the pro-gression of melting and subsequent perforation,instead of preventing or treating it. Hence, we thankDr. Kymionis and Dr. Portaliou for this opportunityto stress once again that CXL should be evaluatedcarefully when deciding to treat new diseases, as inour case.dGiulio Ferrari, MD, Lorenzo Iuliano, MD,Maurizia Vigan�o, MD, Paolo Rama, MD

Hydroimplantation of intraocular lensesWe read with interest and some concern the recent

article by Qazi et al.1 The authors suggestperforming intraocular lens (IOL) implantation under

VOL 39, AUGUST 2013