LETTER
TO THE
A New Simple Corneal Limbal Protection Technique During Corneal Collagen Cross-Linking
EDITOR
punched soft contact lens was fit just before UV-A irradiation and hold on the cornea during CCL (Fig. 3a,b). Ultraviolet-A irradiation was performed as described by Wollensak et al.1
DISCUSSION To the Editor: Keratoconus is a noninflammatory progressive disease, which is characterized by thinning and steepening of cornea and corneal collagen cross-linking (CCL) is the only procedure that can stop the progression of corneal ectasia associated with keratoconus.1 Despite the efficacy of CCL, the effect of ultraviolet A (UV-A) on limbal stem cells is still unclear. So, recently, investigator’s researches are focusing on limbal stem cell damage of UV-A during CCL2–4 and showed the UV-A damage through CCL in layers of corneal epithelial cells at the limbus and suggested the use of polymethylmethacrylate protective rings for limbal protection. In this study, we aimed to describe a new simple corneal limbus protection technique with 8.5-mm punched UV-block soft contact lenses during CCL.
SURGICAL TECHNIQUE In this technique, UV-A transmittance of different silicone hydrogel and daily disposable contact lenses was evaluated before starting epi-on and epi-off CCL. The ultraviolet-A light at 365 nm wavelength (Apollo; Meran Med Inc., Burhaniye, Istanbul) for UV-A source and UV light meter (LUTRON UVC-254 UV Light Meter; Taipei, Taiwan) to measure UV-A radiation were used (Fig. 1a,b). The highest UV-A blockage contact lens was selected and punched with 8.5-mm Barron Corneal Punch System (Altomed, Boldon Business Park, England) (Fig. 2a,b). Then, 5% proparacaine hydrochloride (Alcaine; Alcon Laboratories, Puurs, Belgium) and topical miotic drop of 1% pilokarpine (Bilim Medicine, Istanbul, Türkiye) was applied to eye just before CCL. The central 8.5-mm corneal epithelium was debrided by crescent knife (Beaver; Visitec International, Inc., Waltham, MA) with the assisted 20% alcohol for epi-off CCL, and epithelium debridement was not performed for epi-on CCL. Before UV-A irradiation, as a photosensitizer, riboflavin 0.1% (VibeX; Avedro Inc., Waltham, MA) for epi-off CCL and the transepithelial formulation of riboflavin (ParaCel–VibeX Xtra; Avedro Inc.) for epi-on CCL were applied as described using the manufacturers’ suggested protocol. The
Collagen cross-linking is widely used to stop progression of corneal ectasia, such as keratoconus, pellucid marginal degeneration, and post–laser-assisted in situ keratomileusis ectasia.1 The most important concern in CCL treatment is cytotoxic effect of UV-A.5 It is known that UV-A may damage corneal epithelium, keratocytes, and endothelium; however, riboflavin acts as a photosensitizer and absorbs UV-A and decreases the effect on endothelium. Additionally, UV-A has possible toxic effect on limbal stem cells, and research is focusing on limbal stem cell damage of UV-A during CCL, recently.3,4,6 Matalia et al.2 showed the damage of UV-A on ex vivo–cultured limbal epithelial cells, and riboflavin had blocked (but not all) the effect of UV-A, and Thorsrud et al.3 disclosed in their in vitro experimental study that riboflavin–UV-A treatment was cytotoxic and reduced cell expansion of limbal epithelial cells. And recently, Moore et al.4 demonstrated the oxidative nuclear DNA damage of limbal epithelial cells after CCL. In light of recent studies, limbal protection should be provided. Also, the globus type keratoconus and pellucid marginal degeneration (need wide diameter irradiating area), and drug-resistant peripheral keratitis and low-compliance patients who do not maintain the fixation adequately during CxL need further limbal protection. As described by Moore and Mazzotta et al.,4,7 we consider the necessity of protection of corneal epithelial stem cells (particularly these kind of patients), and we can protect corneal limbus simply with 8.5-mm punched UV-block contact lenses instead of PMMA rings. It has been shown by using confocal microscopy that subepithelial nerves disappeared after epi-off CCL,8 which can affect the process of epithelial healing. Therefore, protection of limbal epithelial cells is becoming an extra important issue for epithelial healing particularly for epi-off CCL. In contrast to epi-off CCL, there were no changes in subepithelial nerves after epi-on CCL,7 and the pathway of lacrimal reflex is not affected consequently. The healthy tears can relieve pain and itching associated with punctate epitheliopathy after epi-on CCL; however, epi-on CCL with 8.5-mm punched UV-block contact lenses reveal more comfort (Bilgihan K, et al, unpublished data, 2014).
FIG. 1. The measurement of UV-A with lenses (a) high UV transmittance contact lens and (b) low UV transmittance contact lens. UV-A, ultraviolet A.
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Eye & Contact Lens Volume 41, Number 2, March 2015
Copyright @ Contact Lens Association of Opthalmologists, Inc. Unauthorized reproduction of this article is prohibited.
Eye & Contact Lens Volume 41, Number 2, March 2015
Letter to the Editor
FIG. 2. (a and b): Contact lens has been punched with 8.5-mm barron corneal punch system.
FIG. 3. (a and b): Epi-off CCL with 8.5-mm punched UV-block contact lenses. CCL, collagen cross-linking.
Additional randomized prospective clinical studies are required to better define the differences between limbal protection CCL and nonlimbal protection CCL. Consequently, the using of punched UV-block contact lenses can be a new simple method for corneal limbal protection during CCL.
Kamil Bilgihan, M.D. Erdem Yuksel, M.D. Department of Ophthalmology, Faculty of Medicine, Gazi University, Ankara, Turkey The authors have no funding or conflicts of interest to disclose. REFERENCES 1. Wollensak G, Spoerl E, Th Seiler. Riboflavin/ultraviolet-A induced collagen cross-linking for the treatment of keratoconus. Am J Ophthalmol 2003;135: 620–627.
© 2015 Contact Lens Association of Ophthalmologists
2. Matalia H, Shetty R, Dhamodaran K, et al. Potential apoptotic effect of ultraviolet-A irradiation during cross-linking: a study on ex vivo cultivated limbal epithelial cells. Br J Ophthalmol 2012;96:1339–1345. 3. Thorsrud A, Nicolaissen B, Drolsum L. Corneal collagen cross-linking in vitro: inhibited regeneration of human limbal epithelial cells after riboflavin-ultraviolet-A exposure. J Cataract Refract Surg 2012;38:1072–1076. 4. Moore JE, Atkinson SD, Azar DT, et al. Protection of corneal epithelial stem cells prevents ultraviolet A damage during corneal collagen cross-linking treatment for keratoconus. Br J Ophthalmol 2014;98:270–274. 5. Wollensak G, Spoerl E, Reber F, et al. Corneal endothelial cytotoxicity of riboflavin/UV-A treatment in vitro. Ophthalmic Res 2003;35:324–328. 6. Wollensak G, Spoerl E, Wilsch M, et al. Keratocyte apoptosis after corneal collagen cross-linking using riboflavin/UV-A treatment. Cornea 2004;23:43–49. 7. Mazzotta C, Traversi C, Baiocchi S. Corneal healing after riboflavin ultraviolet-A collagen cross-linking determined by confocal laser scanning microscopy in vivo: early and late modifications. Am J Ophthalmol 2008; 146:527–533. 8. Touboul D, Efron N, Smadja D, et al. Corneal confocal microscopy following conventional, transepithelial, and accelerated corneal collagen cross-linking procedures for keratoconus. J Refract Surg 2012;28:769–776.
131
Copyright @ Contact Lens Association of Opthalmologists, Inc. Unauthorized reproduction of this article is prohibited.
TO THE
A New Simple Corneal Limbal Protection Technique During Corneal Collagen Cross-Linking
EDITOR
punched soft contact lens was fit just before UV-A irradiation and hold on the cornea during CCL (Fig. 3a,b). Ultraviolet-A irradiation was performed as described by Wollensak et al.1
DISCUSSION To the Editor: Keratoconus is a noninflammatory progressive disease, which is characterized by thinning and steepening of cornea and corneal collagen cross-linking (CCL) is the only procedure that can stop the progression of corneal ectasia associated with keratoconus.1 Despite the efficacy of CCL, the effect of ultraviolet A (UV-A) on limbal stem cells is still unclear. So, recently, investigator’s researches are focusing on limbal stem cell damage of UV-A during CCL2–4 and showed the UV-A damage through CCL in layers of corneal epithelial cells at the limbus and suggested the use of polymethylmethacrylate protective rings for limbal protection. In this study, we aimed to describe a new simple corneal limbus protection technique with 8.5-mm punched UV-block soft contact lenses during CCL.
SURGICAL TECHNIQUE In this technique, UV-A transmittance of different silicone hydrogel and daily disposable contact lenses was evaluated before starting epi-on and epi-off CCL. The ultraviolet-A light at 365 nm wavelength (Apollo; Meran Med Inc., Burhaniye, Istanbul) for UV-A source and UV light meter (LUTRON UVC-254 UV Light Meter; Taipei, Taiwan) to measure UV-A radiation were used (Fig. 1a,b). The highest UV-A blockage contact lens was selected and punched with 8.5-mm Barron Corneal Punch System (Altomed, Boldon Business Park, England) (Fig. 2a,b). Then, 5% proparacaine hydrochloride (Alcaine; Alcon Laboratories, Puurs, Belgium) and topical miotic drop of 1% pilokarpine (Bilim Medicine, Istanbul, Türkiye) was applied to eye just before CCL. The central 8.5-mm corneal epithelium was debrided by crescent knife (Beaver; Visitec International, Inc., Waltham, MA) with the assisted 20% alcohol for epi-off CCL, and epithelium debridement was not performed for epi-on CCL. Before UV-A irradiation, as a photosensitizer, riboflavin 0.1% (VibeX; Avedro Inc., Waltham, MA) for epi-off CCL and the transepithelial formulation of riboflavin (ParaCel–VibeX Xtra; Avedro Inc.) for epi-on CCL were applied as described using the manufacturers’ suggested protocol. The
Collagen cross-linking is widely used to stop progression of corneal ectasia, such as keratoconus, pellucid marginal degeneration, and post–laser-assisted in situ keratomileusis ectasia.1 The most important concern in CCL treatment is cytotoxic effect of UV-A.5 It is known that UV-A may damage corneal epithelium, keratocytes, and endothelium; however, riboflavin acts as a photosensitizer and absorbs UV-A and decreases the effect on endothelium. Additionally, UV-A has possible toxic effect on limbal stem cells, and research is focusing on limbal stem cell damage of UV-A during CCL, recently.3,4,6 Matalia et al.2 showed the damage of UV-A on ex vivo–cultured limbal epithelial cells, and riboflavin had blocked (but not all) the effect of UV-A, and Thorsrud et al.3 disclosed in their in vitro experimental study that riboflavin–UV-A treatment was cytotoxic and reduced cell expansion of limbal epithelial cells. And recently, Moore et al.4 demonstrated the oxidative nuclear DNA damage of limbal epithelial cells after CCL. In light of recent studies, limbal protection should be provided. Also, the globus type keratoconus and pellucid marginal degeneration (need wide diameter irradiating area), and drug-resistant peripheral keratitis and low-compliance patients who do not maintain the fixation adequately during CxL need further limbal protection. As described by Moore and Mazzotta et al.,4,7 we consider the necessity of protection of corneal epithelial stem cells (particularly these kind of patients), and we can protect corneal limbus simply with 8.5-mm punched UV-block contact lenses instead of PMMA rings. It has been shown by using confocal microscopy that subepithelial nerves disappeared after epi-off CCL,8 which can affect the process of epithelial healing. Therefore, protection of limbal epithelial cells is becoming an extra important issue for epithelial healing particularly for epi-off CCL. In contrast to epi-off CCL, there were no changes in subepithelial nerves after epi-on CCL,7 and the pathway of lacrimal reflex is not affected consequently. The healthy tears can relieve pain and itching associated with punctate epitheliopathy after epi-on CCL; however, epi-on CCL with 8.5-mm punched UV-block contact lenses reveal more comfort (Bilgihan K, et al, unpublished data, 2014).
FIG. 1. The measurement of UV-A with lenses (a) high UV transmittance contact lens and (b) low UV transmittance contact lens. UV-A, ultraviolet A.
130
Eye & Contact Lens Volume 41, Number 2, March 2015
Copyright @ Contact Lens Association of Opthalmologists, Inc. Unauthorized reproduction of this article is prohibited.
Eye & Contact Lens Volume 41, Number 2, March 2015
Letter to the Editor
FIG. 2. (a and b): Contact lens has been punched with 8.5-mm barron corneal punch system.
FIG. 3. (a and b): Epi-off CCL with 8.5-mm punched UV-block contact lenses. CCL, collagen cross-linking.
Additional randomized prospective clinical studies are required to better define the differences between limbal protection CCL and nonlimbal protection CCL. Consequently, the using of punched UV-block contact lenses can be a new simple method for corneal limbal protection during CCL.
Kamil Bilgihan, M.D. Erdem Yuksel, M.D. Department of Ophthalmology, Faculty of Medicine, Gazi University, Ankara, Turkey The authors have no funding or conflicts of interest to disclose. REFERENCES 1. Wollensak G, Spoerl E, Th Seiler. Riboflavin/ultraviolet-A induced collagen cross-linking for the treatment of keratoconus. Am J Ophthalmol 2003;135: 620–627.
© 2015 Contact Lens Association of Ophthalmologists
2. Matalia H, Shetty R, Dhamodaran K, et al. Potential apoptotic effect of ultraviolet-A irradiation during cross-linking: a study on ex vivo cultivated limbal epithelial cells. Br J Ophthalmol 2012;96:1339–1345. 3. Thorsrud A, Nicolaissen B, Drolsum L. Corneal collagen cross-linking in vitro: inhibited regeneration of human limbal epithelial cells after riboflavin-ultraviolet-A exposure. J Cataract Refract Surg 2012;38:1072–1076. 4. Moore JE, Atkinson SD, Azar DT, et al. Protection of corneal epithelial stem cells prevents ultraviolet A damage during corneal collagen cross-linking treatment for keratoconus. Br J Ophthalmol 2014;98:270–274. 5. Wollensak G, Spoerl E, Reber F, et al. Corneal endothelial cytotoxicity of riboflavin/UV-A treatment in vitro. Ophthalmic Res 2003;35:324–328. 6. Wollensak G, Spoerl E, Wilsch M, et al. Keratocyte apoptosis after corneal collagen cross-linking using riboflavin/UV-A treatment. Cornea 2004;23:43–49. 7. Mazzotta C, Traversi C, Baiocchi S. Corneal healing after riboflavin ultraviolet-A collagen cross-linking determined by confocal laser scanning microscopy in vivo: early and late modifications. Am J Ophthalmol 2008; 146:527–533. 8. Touboul D, Efron N, Smadja D, et al. Corneal confocal microscopy following conventional, transepithelial, and accelerated corneal collagen cross-linking procedures for keratoconus. J Refract Surg 2012;28:769–776.
131
Copyright @ Contact Lens Association of Opthalmologists, Inc. Unauthorized reproduction of this article is prohibited.
