Background:The aim of the study is to raise the awareness of the influence of coma-like higher-order aberrations(HOAs)on power and orientation of refractive astigmatism(RA)and to explore how to account for that influe...Background:The aim of the study is to raise the awareness of the influence of coma-like higher-order aberrations(HOAs)on power and orientation of refractive astigmatism(RA)and to explore how to account for that influence in the planning of topography-guided refractive surgery in eyes with coma-like-aberrations-dominant corneal optics.Methods:Eleven eyes with coma-like-aberrations-dominant corneal optics and with low lenticular astigmatism(LA)were selected for astigmatism analysis and for treatment simulations with topography-guided custom ablation.Vector analysis was used to evaluate the contribution of coma-like corneal HOAs to RA.Two different strategies were used for simulated treatments aiming to regularize irregular corneal optics:With both strategies correction of anterior corneal surface irregularities(corneal HOAs)were intended.Correction of total corneal astigmatism(TCA)and RA was intended as well with strategies 1 and 2,respectively.Results:Axis of discrepant astigmatism(RA minus TCA minus LA)correlated strongly with axis of coma.Vertical coma influenced RA by canceling the effect of the with-the-rule astigmatism and increasing the effect of the against-the-rule astigmatism.After simulated correction of anterior corneal HOAs along with TCA and RA(strategies 1 and 2),only a small amount of anterior corneal astigmatism(ACA)and no TCA remained after strategy 1,while considerable amount of ACA and TCA remained after strategy 2.Conclusions:Coma-like corneal aberrations seem to contribute a considerable astigmatic component to RA in eyes with coma-like-aberrations dominant corneal optics.If topography-guided ablation is programmed to correct the corneal HOAs and RA,the astigmatic component caused by the coma-like corneal HOAs will be treated twice and will result in induced astigmatism.Disregarding RA and treating TCA along with the corneal HOAs is recommended instead.展开更多
Corneal collagen cross-linking(CXL)is a therapeutic procedure aiming at increasing the corneal stiffness in the keratoconus eyes by induction of cross-links within the extracellular matrix.It is achieved by ultraviole...Corneal collagen cross-linking(CXL)is a therapeutic procedure aiming at increasing the corneal stiffness in the keratoconus eyes by induction of cross-links within the extracellular matrix.It is achieved by ultraviolet-A(370 nm)irradiation of the cornea after saturation with the photosensitizer riboflavin.In the conventional CXL protocol,a minimum de-epithelialized corneal thickness of 400μm is recommended to avoid potential irradiation damage to the corneal endothelium.In advanced keratoconus,however,stromal thickness is often lower than 400μm,which limits the application of CXL in that category.Efforts have been undertaken to modify the conventional CXL procedure to be applicable in thin corneas.The current review discusses different techniques employed to achieve this end and their results.The overall safety and efficacy of the modified CXL protocols are good,as most of them managed to halt the progression of keratectasia without postoperative complications.However,the evidence of safety and efficacy in the use of modified CXL protocols is still limited to few studies with few patients involved.Controlled studies with long-term follow-up are required to confirm the safety and efficacy of the modified protocols.展开更多
Background:To evaluate the safety and efficacy of an approach that combines corneal customized transepithelial therapeutic ablation to treat irregular corneal optics and accelerated corneal collagen cross-linking(CXL)...Background:To evaluate the safety and efficacy of an approach that combines corneal customized transepithelial therapeutic ablation to treat irregular corneal optics and accelerated corneal collagen cross-linking(CXL)to strengthen the corneal tissue and stop the progression of keratoconus.The transepithelial therapeutic ablation applied a novel concept named central corneal regularization(CCR)which could correct the corneal morphological irregularities and the eye’s spherocylindrical refractive error with minimal stromal tissue removal.Methods:Retrospective study.Eyes that underwent CCR combined with CXL were evaluated preoperatively and up to 12 months postoperatively for visual acuity,subjective refraction,corneal haze,pachymetry and maximum keratometry(Kmax).Results:Twenty four eyes of 24 patients with a mean age of 28.92±9.88 years were treated.The mean spherical equivalent(SE)refractive error changed from−0.74±1.17 D preoperatively to−1.05±1.52 D at 12 months postoperatively.The mean uncorrected distance visual acuity(UDVA)and corrected distance visual acuity(CDVA)improved.No eye lost lines of CDVA,21 had a mean improvement of 3.21 lines.The mean cylinder error and Kmax value dropped from−3.06±1.83 D and 51.38±3.29 D to−1.04±0.80 D and 48.70±2.58 D,respectively.The mean haze score at 3,6 and 12 months was 0.56,0.19 and 0.06,respectively.Conclusions:CCR combined with CXL offers promising results as a safe and effective treatment in keratoconic patients.展开更多
文摘Background:The aim of the study is to raise the awareness of the influence of coma-like higher-order aberrations(HOAs)on power and orientation of refractive astigmatism(RA)and to explore how to account for that influence in the planning of topography-guided refractive surgery in eyes with coma-like-aberrations-dominant corneal optics.Methods:Eleven eyes with coma-like-aberrations-dominant corneal optics and with low lenticular astigmatism(LA)were selected for astigmatism analysis and for treatment simulations with topography-guided custom ablation.Vector analysis was used to evaluate the contribution of coma-like corneal HOAs to RA.Two different strategies were used for simulated treatments aiming to regularize irregular corneal optics:With both strategies correction of anterior corneal surface irregularities(corneal HOAs)were intended.Correction of total corneal astigmatism(TCA)and RA was intended as well with strategies 1 and 2,respectively.Results:Axis of discrepant astigmatism(RA minus TCA minus LA)correlated strongly with axis of coma.Vertical coma influenced RA by canceling the effect of the with-the-rule astigmatism and increasing the effect of the against-the-rule astigmatism.After simulated correction of anterior corneal HOAs along with TCA and RA(strategies 1 and 2),only a small amount of anterior corneal astigmatism(ACA)and no TCA remained after strategy 1,while considerable amount of ACA and TCA remained after strategy 2.Conclusions:Coma-like corneal aberrations seem to contribute a considerable astigmatic component to RA in eyes with coma-like-aberrations dominant corneal optics.If topography-guided ablation is programmed to correct the corneal HOAs and RA,the astigmatic component caused by the coma-like corneal HOAs will be treated twice and will result in induced astigmatism.Disregarding RA and treating TCA along with the corneal HOAs is recommended instead.
文摘Corneal collagen cross-linking(CXL)is a therapeutic procedure aiming at increasing the corneal stiffness in the keratoconus eyes by induction of cross-links within the extracellular matrix.It is achieved by ultraviolet-A(370 nm)irradiation of the cornea after saturation with the photosensitizer riboflavin.In the conventional CXL protocol,a minimum de-epithelialized corneal thickness of 400μm is recommended to avoid potential irradiation damage to the corneal endothelium.In advanced keratoconus,however,stromal thickness is often lower than 400μm,which limits the application of CXL in that category.Efforts have been undertaken to modify the conventional CXL procedure to be applicable in thin corneas.The current review discusses different techniques employed to achieve this end and their results.The overall safety and efficacy of the modified CXL protocols are good,as most of them managed to halt the progression of keratectasia without postoperative complications.However,the evidence of safety and efficacy in the use of modified CXL protocols is still limited to few studies with few patients involved.Controlled studies with long-term follow-up are required to confirm the safety and efficacy of the modified protocols.
文摘Background:To evaluate the safety and efficacy of an approach that combines corneal customized transepithelial therapeutic ablation to treat irregular corneal optics and accelerated corneal collagen cross-linking(CXL)to strengthen the corneal tissue and stop the progression of keratoconus.The transepithelial therapeutic ablation applied a novel concept named central corneal regularization(CCR)which could correct the corneal morphological irregularities and the eye’s spherocylindrical refractive error with minimal stromal tissue removal.Methods:Retrospective study.Eyes that underwent CCR combined with CXL were evaluated preoperatively and up to 12 months postoperatively for visual acuity,subjective refraction,corneal haze,pachymetry and maximum keratometry(Kmax).Results:Twenty four eyes of 24 patients with a mean age of 28.92±9.88 years were treated.The mean spherical equivalent(SE)refractive error changed from−0.74±1.17 D preoperatively to−1.05±1.52 D at 12 months postoperatively.The mean uncorrected distance visual acuity(UDVA)and corrected distance visual acuity(CDVA)improved.No eye lost lines of CDVA,21 had a mean improvement of 3.21 lines.The mean cylinder error and Kmax value dropped from−3.06±1.83 D and 51.38±3.29 D to−1.04±0.80 D and 48.70±2.58 D,respectively.The mean haze score at 3,6 and 12 months was 0.56,0.19 and 0.06,respectively.Conclusions:CCR combined with CXL offers promising results as a safe and effective treatment in keratoconic patients.
