reply: use of isoptocarpine in corneal collagen crosslinking

1
is whether the follow-up will reveal long-term side effects and complications affecting the cornea or under- lying tissue. It is common knowledge that riboflavin has a double role in corneal collagen crosslinking. Riboflavin induces the cross links but, at the same time, it accumulates in the anterior chamber, protecting the eye from the UVA irradiation. 2 Another way of providing the maximum protective effect to tissues predisposed to the harmful action of UVA irradiation might be the use of isoptocarpine, a slowly hydrolyzed muscarinic agonist used as a mi- otic. The miosis provoked probably minimizes the amount of UVA irradiation absorbed by the crystalline lens and the retina. Adding the use of isoptocarpine drops during patient preparation for surgery (1 drop 10 minutes before the beginning of the procedure) requires zero time but might provide a significant advantage in the long-term outcome of this procedure. George D. Kymionis, MD, PhD Dimitra M. Portaliou, MD Heraklion, Crete, Greece REFERENCES 1. Hayes S, O’Brart DP, Lamdin LS, Doutch J, Samaras K, Marshall J, Meek KM. Effect of complete epithelial debridement before riboflavin–ultraviolet-A corneal collagen crosslinking therapy. J Cataract Refract Surg 2008; 34:657–661 2. Wollensak G. Crosslinking treatment of progressive keratoconus: new hope. Curr Opin Ophthalmol 2006; 17:356–360 REPLY: We thank Kymionis and Portaliou for their kind comments about our recent article and also for their interesting suggestion about the preoperative use of isoptocarpine drops to minimize the exposure of the retina and lens to UVA irradiation during corneal cross-linkage therapy. Based on current treat- ment protocols with complete epithelial debridement, adequate time for riboflavin 0.1% corneal stromal absorption, and homogeneous UV irradiance of 3 mW/cm 2 , the work of Spoerl et al. 1 indicates that the radiant exposures achieved at the lens and retina are considerably less than their respective UV damage thresholds. However, any therapeutic modality that further reduces radiant exposure to these tissues merits further investigation.dDavid P. O’Brart, MD, Sally Hayes, PhD REFERENCE 1. Spoerl E, Mrochen M, Sliney D, Trokel S, Seiler T. Safety of UVA– riboflavin cross-linking of the cornea. Cornea 2007; 26:385–389 Initial report of IOL-induced accommodation I noted one important omission in the extensive bib- liography of the article by Marchini et al. 1 in which ultrasound biomicroscopy demonstrated movement of the capsular-fixated intraocular lens (IOL) during accommodation. In 1985, Spencer Thornton, MD, was the first ophthalmologist to demonstrate this phe- nomenon. He presented his initial observations at the Hawaiian Ophthalmological Society meeting (‘‘An IOL That Gives Accommodation?’’ Ocular Surgery News, May 1, 1985, pages 1,45; S.P. Thornton, MD, ‘‘Accommodating IOLs [letter],’’ Ocular Surgery News, October 1, 1985, pages 3–4). Thornton’s work was subsequently published in a peer-reviewed journal. 2 Robert H. Osher, MD Cincinnati, Ohio, USA REFERENCES 1. Marchini G, Pedrotti E, Modesti M, Visentin S, Tosi R. Anterior segment changes during accommodation in eyes with a monofo- cal intraocular lens: high-frequency ultrasound study. J Cataract Refract Surg 2008; 33:949–956 2. Thornton SP. Lens implantation with restored accommodation. Curr Canad Ophthalmic Pract 1986; 4:60,62,82 REPLY: We agree with Osher, but even if we had known that Thornton was the first ophthalmologist to demonstrate anterior movement of a 3-piece loop IOL using A-scan biometry, we would not have found the original article. That is because Thornton’s impor- tant work was published in a journal that was not indexed in the medical indexes. We think it would have been incorrect to include an article that we could not read.dGiorgio Marchini, PhD, Emilio Pedrotti, MD, Silvia Visentin, MD Refractive outcome of phacovitrectomy The refractive results of phacovitrectomy are in- creasingly important, and the paper by Patel et al. 1 adds useful data and demonstrates that the accuracy of the refractive outcome of phacovitrectomy for mac- ular hole is comparable to that of phacoemulsification alone. The authors found a mean postoperative predic- tion error (PPE) of 0.39 diopters (D) with the com- bined procedure and postulated that this small myopic shift may be secondary to anterior displace- ment of the intraocular lens (IOL) by intravitreal gas pressure. However, Patel et al. used historical control data from Murphy et al., 2 who also found a small my- opic PPE of 0.32 D in their series of solitary uncom- plicated phacoemulsification surgeries. The question arises as to whether the myopic shift Patel et al. observed is unique to the phacovitrectomy procedure, the precise surgical technique and IOL used, or the indication of macular hole surgery only. 2009 LETTERS J CATARACT REFRACT SURG - VOL 34, DECEMBER 2008

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is whether the follow-up will reveal long-term sideeffects and complications affecting the cornea orunder-lying tissue. It is common knowledge that riboflavinhas a double role in corneal collagen crosslinking.Riboflavin induces the cross links but, at the sametime, it accumulates in the anterior chamber, protectingthe eye from the UVA irradiation.2

Another way of providing the maximum protectiveeffect to tissues predisposed to the harmful action ofUVA irradiation might be the use of isoptocarpine,a slowly hydrolyzed muscarinic agonist used as a mi-otic. The miosis provoked probably minimizes theamount of UVA irradiation absorbed by the crystallinelens and the retina.

Adding the use of isoptocarpine drops duringpatient preparation for surgery (1 drop 10 minutesbefore the beginning of the procedure) requires zerotime but might provide a significant advantage inthe long-term outcome of this procedure.

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

Heraklion, Crete, Greece

REFERENCES1. Hayes S, O’Brart DP, Lamdin LS, Doutch J, Samaras K,

Marshall J, Meek KM. Effect of complete epithelial debridement

before riboflavin–ultraviolet-A corneal collagen crosslinking

therapy. J Cataract Refract Surg 2008; 34:657–661

2. Wollensak G. Crosslinking treatment of progressive keratoconus:

new hope. Curr Opin Ophthalmol 2006; 17:356–360

ultrasound biomicroscopy demonstrated movementof the capsular-fixated intraocular lens (IOL) duringaccommodation. In 1985, Spencer Thornton, MD,was the first ophthalmologist to demonstrate this phe-nomenon. He presented his initial observations at theHawaiian Ophthalmological Society meeting (‘‘AnIOL That Gives Accommodation?’’ Ocular SurgeryNews, May 1, 1985, pages 1,45; S.P. Thornton, MD,‘‘Accommodating IOLs [letter],’’ Ocular SurgeryNews, October 1, 1985, pages 3–4). Thornton’s workwas subsequently published in a peer-reviewedjournal.2

Robert H. Osher, MDCincinnati, Ohio, USA

REFERENCES1. Marchini G, Pedrotti E, Modesti M, Visentin S, Tosi R. Anterior

segment changes during accommodation in eyes with a monofo-

cal intraocular lens: high-frequency ultrasound study. J Cataract

Refract Surg 2008; 33:949–956

2. Thornton SP. Lens implantation with restored accommodation.

Curr Canad Ophthalmic Pract 1986; 4:60,62,82

REPLY: We agree with Osher, but even if we hadknown that Thornton was the first ophthalmologistto demonstrate anterior movement of a 3-piece loopIOL using A-scan biometry, we would not have foundthe original article. That is because Thornton’s impor-tant work was published in a journal that was notindexed in the medical indexes. We think it wouldhave been incorrect to include an article that we couldnot read.dGiorgio Marchini, PhD, Emilio Pedrotti, MD,Silvia Visentin, MD

Refractive outcome of phacovitrectomyThe refractive results of phacovitrectomy are in-

creasingly important, and the paper by Patel et al.1

adds useful data and demonstrates that the accuracyof the refractive outcome of phacovitrectomy for mac-ular hole is comparable to that of phacoemulsificationalone. The authors found amean postoperative predic-tion error (PPE) of �0.39 diopters (D) with the com-bined procedure and postulated that this smallmyopic shift may be secondary to anterior displace-ment of the intraocular lens (IOL) by intravitreal gaspressure. However, Patel et al. used historical controldata from Murphy et al.,2 who also found a small my-opic PPE of �0.32 D in their series of solitary uncom-plicated phacoemulsification surgeries. The question

2009LETTERS

REPLY: We thank Kymionis and Portaliou for theirkind comments about our recent article and also fortheir interesting suggestion about the preoperativeuse of isoptocarpine drops to minimize the exposureof the retina and lens to UVA irradiation duringcorneal cross-linkage therapy. Based on current treat-ment protocols with complete epithelial debridement,adequate time for riboflavin 0.1% corneal stromalabsorption, and homogeneous UV irradiance of 3mW/cm2, the work of Spoerl et al.1 indicates that theradiant exposures achieved at the lens and retina areconsiderably less than their respective UV damagethresholds. However, any therapeutic modality thatfurther reduces radiant exposure to these tissuesmerits further investigation.dDavid P. O’Brart, MD,Sally Hayes, PhD

REFERENCE1. Spoerl E, Mrochen M, Sliney D, Trokel S, Seiler T. Safety of UVA–

riboflavin cross-linking of the cornea. Cornea 2007; 26:385–389

Initial report of IOL-induced accommodationI noted one important omission in the extensive bib-

liography of the article by Marchini et al.1 in which

arises as to whether the myopic shift Patel et al.observed is unique to the phacovitrectomy procedure,the precise surgical technique and IOL used, or theindication of macular hole surgery only.

J CATARACT REFRACT SURG - VOL 34, DECEMBER 2008