Keratoconus is a condition characterized by biomechanical instability of the cornea, presenting in a progressive, asymmetric and bilateral way. Corneal collagen crosslinking(CXL) with riboflavin and Ultraviolet-A(UVA)...Keratoconus is a condition characterized by biomechanical instability of the cornea, presenting in a progressive, asymmetric and bilateral way. Corneal collagen crosslinking(CXL) with riboflavin and Ultraviolet-A(UVA) is a new technique of corneal tissue strengthening that combines the use of riboflavin as a photo sensitizer and UVA irradiation. Studies showed that CXL was effective in halting the progression of keratoconus over a period of up to four years. The published studies also revealed a reduction of max K readings by more than 2 D, while the postoperative spherical equivalent(SEQ) was reduced by an average of more than 1 D and refractive cylinder decreased by about1 D. The major indication for the use of CXL is to inhibit the progression of corneal ecstasies, such as keratoconus and pellucid marginal degeneration. CXL may also be effective in the treatment and prophylaxis of iatrogenic keratectasia, resulting from excessively aggressive photo ablation. This treatment has been used to treat infectious corneal ulcers with apparent favorable results. Most recent studies demonstrate the beneficial impact of CXL for iatrogenic ecstasies, pellucid marginal degeneration, infectious keratitis, bullous keratopathy and ulcerative keratitis. Several long-term and short-term complications of CXL have been studied and documented. The possibility of a secondary infection after the procedure exists because the patient is subject to epithelial debridement and the application of a soft contact lens. Formation of temporary corneal haze,permanent scars, endothelial damage, treatment failure,sterile infiltrates, bullous keratopathy and herpes reactivation are the other reported complications of this procedure.展开更多
AIM:To compare the safety and efficacy of conventional versus accelerated(9 mW/cm^2)corneal collagen crosslinking(CXL)in progressive keratoconus at the 2-year follow-up.METHODS:In this prospective study,consecutive pr...AIM:To compare the safety and efficacy of conventional versus accelerated(9 mW/cm^2)corneal collagen crosslinking(CXL)in progressive keratoconus at the 2-year follow-up.METHODS:In this prospective study,consecutive progressive keratoconus patients were randomized to receive either conventional CXL(CCXL)or accelerated CXL(ACXL;using hydroxypropyl methylcellulose-assisted riboflavin imbibition for 10 min at 9 mW/cm^2).Visual,refractive,keratometric,topographic,and aberrometric outcomes and stromal demarcation line depth(DLD)measurements were compared at the end of a 2-year follow-up.RESULTS:Thirty-two eyes from 32 patients in the CCXL and 27 eyes from 27 patients in the ACXL groups completed 2-year follow-up.At 2y post-CXL,both uncorrected and corrected visual acuities improved significantly in both groups.The improvements in keratometric readings,flattening rate(flattening of the maximum keratometry more than 1 D),3 topographic indices,and vertical coma were significantly better in the CCXL group compared to the ACXL group(P<0.05).The DLD as measured by anterior segment optical coherence tomography or in vivo confocal microscopy was better detectable and significantly deeper in the CCXL group compared to the ACXL group.The deeper DLD was found to be significantly correlated with improvements in the mean keratometry measurements.Progression was noted in 11.1%of eyes in the ACXL group,whereas progression was not observed in any patient eye in the CCXL group.CONCLUSION:In this prospective randomized study,ACXL is less effective in halting the progression of keratoconus at a 2-year follow-up compared to CCXL.展开更多
Background:To compare the safety and efficacy of iontophoresis-assisted epithelial-on corneal crosslinking(I-CXL)using 0.1%riboflavin-distilled water solution with standard epithelium-off corneal crosslinking(S-CXL)fo...Background:To compare the safety and efficacy of iontophoresis-assisted epithelial-on corneal crosslinking(I-CXL)using 0.1%riboflavin-distilled water solution with standard epithelium-off corneal crosslinking(S-CXL)for progressive keratoconus.Methods:In a retrospective analysis,progressive keratoconus patients treated with I-CXL(17 eyes of 17 patients)or S-CXL(13 eyes of 13 patients)were included.All patients were followed up at least 12 months.All patients underwent detailed ophthalmologic examinations involving pre-and postoperative visual acuity,topographic parameters and pachymetry.Intra-and postoperative complications were recorded.Results:No statistically significant differences were observed between the two groups at baseline with respect to visual acuity,age and thinnest corneal thickness(TCT).The postoperative decreases of K1 and Kmean in the S-CXL group represented statistically significantly better results than in the I-CXL group(t=2.093 and 2.123,P=0.046 and 0.043,respectively).Alterations of other parameters showed no significant differences between the two groups.There were no failure cases in the two groups.Conclusions:I-CXL using 0.1%riboflavin-distilled water solution provided effective treatment for progressive keratoconus at 12-month follow-up.However,the decreases of K1 and Kmean caused by I-CXL were less than those by S-CXL.Although treatment time,postoperative patient pain and risk of infection in I-CXL are all less than those in S-CXL,I-CXL is unable to completely replace S-CXL for progressive keratoconus temporarily.展开更多
AIM: To analyze the efficacy of ultraviolet (UV) light initiating corneal cross-linking (CXL). METHODS: The time-dependent absorption of UV light due to the depletion of the initiator (riboflavin) was calculated. The ...AIM: To analyze the efficacy of ultraviolet (UV) light initiating corneal cross-linking (CXL). METHODS: The time-dependent absorption of UV light due to the depletion of the initiator (riboflavin) was calculated. The effective dose of CXL with corneal surface covered by a thin layer of riboflavin was derived analytically. The cross linking time was calculated by the depletion level of the riboflavin concentration. A comprehensive method was used to derive analytic formulas. RESULTS: The effective dose of CXL was reduced by a factor (R) which was proportional to the thickness (d) and concentrations (C-0) of the riboflavin surface layer. Our calculations showed that the conventional dose of 5.4 J/cm(2) had a reduced effective dose of 4.3 and 3.45 J/cm(2), for d was 100 and 200 pm, respectively, and C-0=0.1%. The surface cross linking time was calculated to be T*=10.75s, for a depletion level of 0.135 and UV initial intensity of 30 mW/cm(2). The volume T* was exponentially increasing and proportional to exp (bdC(0)), with b being the steady state absorption coefficient. CONCLUSION: The effective dose of CXL is reduced by a factor proportional to the thickness and concentrations of the riboflavin surface layer. The wasted dose should be avoided by washing out the extra riboflavin surface layer prior to the UV light exposure.展开更多
Corneal cross-linking（CXL） is a noninvasive therapeutic procedure for keratoconus that is aimed at improving corneal biomechanical properties by induction of covalent cross-links between stromal proteins. It is acco...Corneal cross-linking（CXL） is a noninvasive therapeutic procedure for keratoconus that is aimed at improving corneal biomechanical properties by induction of covalent cross-links between stromal proteins. It is accomplished by ultraviolet A（UVA） radiation of the cornea, which is first saturated with photosensitizing riboflavin. It has been shown that standard epithelium-off CXL（S-CXL） is efficacious, and it has been recommended as the standard of care procedure for keratoconus. However, epithelial removal leads to pain, transient vision loss, and a higher risk of corneal infection. To avoid these disadvantages, transepithelial CXL was developed. Recently, iontophoresis has been adopted to increase riboflavin penetration through the epithelium. Several clinical observations have demonstrated the safety and efficacy of iontophoresisassisted epithelium-on CXL（I-CXL） for keratoconus. This review aimed to provide a comprehensive summary of the published studies regarding I-CXL and a comparison between I-CXL and S-CXL. All articles used in this review were mainly retrieved from the Pub Med database. Original articles and reviews were selected if they were related to the I-CXL technique or related to the comparison between I-CXL and S-CXL.展开更多
基金Supported by Jiangsu Province's Key Provincial Talents Program(RC2011104)
文摘Keratoconus is a condition characterized by biomechanical instability of the cornea, presenting in a progressive, asymmetric and bilateral way. Corneal collagen crosslinking(CXL) with riboflavin and Ultraviolet-A(UVA) is a new technique of corneal tissue strengthening that combines the use of riboflavin as a photo sensitizer and UVA irradiation. Studies showed that CXL was effective in halting the progression of keratoconus over a period of up to four years. The published studies also revealed a reduction of max K readings by more than 2 D, while the postoperative spherical equivalent(SEQ) was reduced by an average of more than 1 D and refractive cylinder decreased by about1 D. The major indication for the use of CXL is to inhibit the progression of corneal ecstasies, such as keratoconus and pellucid marginal degeneration. CXL may also be effective in the treatment and prophylaxis of iatrogenic keratectasia, resulting from excessively aggressive photo ablation. This treatment has been used to treat infectious corneal ulcers with apparent favorable results. Most recent studies demonstrate the beneficial impact of CXL for iatrogenic ecstasies, pellucid marginal degeneration, infectious keratitis, bullous keratopathy and ulcerative keratitis. Several long-term and short-term complications of CXL have been studied and documented. The possibility of a secondary infection after the procedure exists because the patient is subject to epithelial debridement and the application of a soft contact lens. Formation of temporary corneal haze,permanent scars, endothelial damage, treatment failure,sterile infiltrates, bullous keratopathy and herpes reactivation are the other reported complications of this procedure.
文摘AIM:To compare the safety and efficacy of conventional versus accelerated(9 mW/cm^2)corneal collagen crosslinking(CXL)in progressive keratoconus at the 2-year follow-up.METHODS:In this prospective study,consecutive progressive keratoconus patients were randomized to receive either conventional CXL(CCXL)or accelerated CXL(ACXL;using hydroxypropyl methylcellulose-assisted riboflavin imbibition for 10 min at 9 mW/cm^2).Visual,refractive,keratometric,topographic,and aberrometric outcomes and stromal demarcation line depth(DLD)measurements were compared at the end of a 2-year follow-up.RESULTS:Thirty-two eyes from 32 patients in the CCXL and 27 eyes from 27 patients in the ACXL groups completed 2-year follow-up.At 2y post-CXL,both uncorrected and corrected visual acuities improved significantly in both groups.The improvements in keratometric readings,flattening rate(flattening of the maximum keratometry more than 1 D),3 topographic indices,and vertical coma were significantly better in the CCXL group compared to the ACXL group(P<0.05).The DLD as measured by anterior segment optical coherence tomography or in vivo confocal microscopy was better detectable and significantly deeper in the CCXL group compared to the ACXL group.The deeper DLD was found to be significantly correlated with improvements in the mean keratometry measurements.Progression was noted in 11.1%of eyes in the ACXL group,whereas progression was not observed in any patient eye in the CCXL group.CONCLUSION:In this prospective randomized study,ACXL is less effective in halting the progression of keratoconus at a 2-year follow-up compared to CCXL.
基金This work was suppor ted by Beijing Municipal Science and Technology Commission(No.Z151100004015217).
文摘Background:To compare the safety and efficacy of iontophoresis-assisted epithelial-on corneal crosslinking(I-CXL)using 0.1%riboflavin-distilled water solution with standard epithelium-off corneal crosslinking(S-CXL)for progressive keratoconus.Methods:In a retrospective analysis,progressive keratoconus patients treated with I-CXL(17 eyes of 17 patients)or S-CXL(13 eyes of 13 patients)were included.All patients were followed up at least 12 months.All patients underwent detailed ophthalmologic examinations involving pre-and postoperative visual acuity,topographic parameters and pachymetry.Intra-and postoperative complications were recorded.Results:No statistically significant differences were observed between the two groups at baseline with respect to visual acuity,age and thinnest corneal thickness(TCT).The postoperative decreases of K1 and Kmean in the S-CXL group represented statistically significantly better results than in the I-CXL group(t=2.093 and 2.123,P=0.046 and 0.043,respectively).Alterations of other parameters showed no significant differences between the two groups.There were no failure cases in the two groups.Conclusions:I-CXL using 0.1%riboflavin-distilled water solution provided effective treatment for progressive keratoconus at 12-month follow-up.However,the decreases of K1 and Kmean caused by I-CXL were less than those by S-CXL.Although treatment time,postoperative patient pain and risk of infection in I-CXL are all less than those in S-CXL,I-CXL is unable to completely replace S-CXL for progressive keratoconus temporarily.
基金Supported by an internal grant from New Vision Inc.Talent-Xiamen(XM-200)Program(Xiamen Science&Technology Bureau,China)
文摘AIM: To analyze the efficacy of ultraviolet (UV) light initiating corneal cross-linking (CXL). METHODS: The time-dependent absorption of UV light due to the depletion of the initiator (riboflavin) was calculated. The effective dose of CXL with corneal surface covered by a thin layer of riboflavin was derived analytically. The cross linking time was calculated by the depletion level of the riboflavin concentration. A comprehensive method was used to derive analytic formulas. RESULTS: The effective dose of CXL was reduced by a factor (R) which was proportional to the thickness (d) and concentrations (C-0) of the riboflavin surface layer. Our calculations showed that the conventional dose of 5.4 J/cm(2) had a reduced effective dose of 4.3 and 3.45 J/cm(2), for d was 100 and 200 pm, respectively, and C-0=0.1%. The surface cross linking time was calculated to be T*=10.75s, for a depletion level of 0.135 and UV initial intensity of 30 mW/cm(2). The volume T* was exponentially increasing and proportional to exp (bdC(0)), with b being the steady state absorption coefficient. CONCLUSION: The effective dose of CXL is reduced by a factor proportional to the thickness and concentrations of the riboflavin surface layer. The wasted dose should be avoided by washing out the extra riboflavin surface layer prior to the UV light exposure.
基金Supported by Beijing Municipal Science and Technology Commission(No.Z151100004015217)
文摘Corneal cross-linking（CXL） is a noninvasive therapeutic procedure for keratoconus that is aimed at improving corneal biomechanical properties by induction of covalent cross-links between stromal proteins. It is accomplished by ultraviolet A（UVA） radiation of the cornea, which is first saturated with photosensitizing riboflavin. It has been shown that standard epithelium-off CXL（S-CXL） is efficacious, and it has been recommended as the standard of care procedure for keratoconus. However, epithelial removal leads to pain, transient vision loss, and a higher risk of corneal infection. To avoid these disadvantages, transepithelial CXL was developed. Recently, iontophoresis has been adopted to increase riboflavin penetration through the epithelium. Several clinical observations have demonstrated the safety and efficacy of iontophoresisassisted epithelium-on CXL（I-CXL） for keratoconus. This review aimed to provide a comprehensive summary of the published studies regarding I-CXL and a comparison between I-CXL and S-CXL. All articles used in this review were mainly retrieved from the Pub Med database. Original articles and reviews were selected if they were related to the I-CXL technique or related to the comparison between I-CXL and S-CXL.
