Early changes in corneal densitometry after FS-LASIK combined with accelerated corneal cross-linking for correction of high myopia

AIM:To observe the effects of femtosecond laserassisted excimer laser in situ keratomileusis combined with accelerated corneal cross-linking(FS-LASIK Xtra)on corneal densitometry after correcting for high myopia.METHODS:In this prospectively study,130 patients underwent FS-LASIK or FS-LASIK Xtra for high myopia.Their right eyes were selected for inclusion in the study,of which 65 cases of 65 eyes in the FS-LASIK group,65 patients with 65 eyes in the FS-LASIK Xtra group.Patients were evaluated for corneal densitometry at 1,3,and 6mo postoperatively using Pentacam Scheimpflug imaging.RESULTS:Preoperative differences in corneal densitometry between the FS-LASIK and FS-LASIK Xtra groups in different ranges were not statistically significant(P>0.05).Layer-by-layer analysis revealed statistically significant differences in the anterior(120μm),central,and total layer corneal densitometry between the FS-LASIK and FS-LASIK Xtra groups at 1 and 3mo postoperatively(all P<0.05),the FS-LASIK Xtra group is higher than that of the FS-LASIK group.Analysis of different diameter ranges showed statistically significant differences between the FS-LASIK group and the FS-LASIK Xtra group at 1mo postoperatively in the ranges of 0–2,2–6,and 6–10 mm(both P<0.05);At 3mo postoperatively,the FS-LASIK Xtra group is higher than that of the FS-LASIK group in the ranges of 0–2 and 2–6 mm(P<0.05).At 6mo postoperatively,there were no statistically significant differences in corneal densitometry between the FS-LASIK group and the FS-LASIK Xtra group in different diameter ranges(all P>0.05).CONCLUSION:There is an increase in internal corneal densitometry during the early postoperative period after FS-LASIK Xtra for correction of high myopia.However,the densitometry values decreased to the level of conventional FS-LASIK at 6mo after surgery,with the most significant changes observed in the superficial central zone.

Different accelerated corneal collagen cross-linking treatment modalities in progressive keratoconus

Background:To compare the outcomes of two different protocols of accelerated corneal crosslinking(CXL)on visual,corneal high order aberrations(HOA)and topographic parameters in patients with progressive keratoconus.Methods:In this prospective comparative study,sixty-six eyes of 66 patients with progressive keratoconus were divided into two groups;37 eyes in Group 1 received 18 mW/cm^(2) for five minutes,and 29 eyes in Group 2 were treated with 9 mW/cm^(2) for 10 min.The uncorrected distant visual acuity(UCVA),best-corrected distant visual acuity(BCVA),corneal HOAs and topography parameters were measured preoperatively and postoperatively at the end of 12 months.The data for the two groups were compared statistically.Results:The mean UCVA and BCVA were significantly improved at the postoperative 12 months compared with the preoperative values in both groups(P<0.05 for all).A significant improvement in corneal HOAs was observed in both groups(P<0.05 for all).The change in corneal coma value was significantly higher in Group 2(P<0.05).The change in keratometric values K1,K2,AvgK and maximum keratometry(AKf)were significantly higher in Group 2(P<0.05 for all).The regression model showed that the most important factor predicting the change in AKf was the type of CXL(β=−0.482,P=0.005).Conclusions:Accelerated CXL using 10 min of UVA irradiance at 9 mW/cm^(2) showed better topographic improvements and coma values than five minutes of UVA irradiance at 18 mW/cm^(2) independent of keratoconus severity.

Experimental study on the treatment of rabbit corneal melting after alkali burn with Collagen cross-linking

AIM: To evaluate the effect of Collagen cross-linking on the prevention of melting in rabbit corneas after alkali burn. METHODS: Twenty New Zealand white rabbits were randomly divided into model control group and collagen cross-linking treatment group. The second group of rabbits received collagen cross linked treatment. Both groups were applied with antibiotic eye drops to prevent infection. The corneas were evaluated for melting, opacity, pathological and immunohistochemistry, record the changes when 28 days after the animals were killed. RESULTS: In the control group, 6 out of 8 rabbits showed corneal melting after injury (14 +/- 4) days, while two corneal perforated. In collagen cross-linking treatment group, one rabbit showed corneal melting after injury 23 days, without corneal perforation; corneal dissolution rate between the two groups was significantly different (P <0.05). Pathological examination suggested that in the treatment group, mild corneal edema, mild damage to collagen fibers, inflammatory cell infiltration was significantly less than the control group. Immunohistochemistry showed that corneal collagen fibers arranged in neat rows in the control group. CONCLUSION: Collagen cross-linking treatment not only can prevent and delay the corneal melting after alkali burn, but also can reduce the destruction of corneal collagen fibers and infiltration of inflammatory cells in the corneal tissue.

A short-term study of corneal collagen cross-linking with hypo-osmolar riboflavin solution in keratoconic corneas

AIM: To report the 3mo outcomes of collagen crosslinking(CXL) with a hypo-osmolar riboflavin in thin corneas with the thinnest thickness less than 400 μm without epithelium.METHODS: Eight eyes in 6 patients with age 26.2±4.8y were included in the study. All patients underwent CXL using a hypo-osmolar riboflavin solution after its de-epithelization. Best corrected visual acuity, manifest refraction, the thinnest corneal thickness, and endothelial cell density were evaluated before and 3mo after the procedure.RESULTS: The mean thinnest thickness of the cornea was 408.5 ±29.0 μm before treatment and reduced to369.8 ±24.8 μm after the removal of epithelium. With the application of the hypo-osmolar riboflavin solution, the thickness increased to 445.0 ±26.5 μm before CXL and recover to 412.5 ±22.7 μm at 3mo after treatment, P =0.659). Before surgery, the mean K-value of the apex of the keratoconus corneas was 57.6 ±4.0 diopters, and slightly decreased(54.7±4.9 diopters) after surgery(P =0.085). Mean best-corrected visual acuity was 0.55 ±0.23 logarithm of the minimal angle of resolution, and increased to 0.53±0.26 logarithm after surgery(P =0.879).The endothelial cell density was 2706.4 ±201.6 cells/mm2 before treatment, and slightly decreased( 2641. 2 ±218.2 cells/mm2) at last fellow up(P =0.002).CONCLUSION: Corneal collagen cross-linking with a hypo-osmolar riboflavin in thin corneas seems to be a promising treatment. Further study should be done to evaluate the safety and efficiency of CXL in thin corneas for the long-term.

Corneal collagen cross-linking and liposomal amphotericin B combination therapy for fungal keratitis in rabbits

AIM： To observe the therapeutic effect of corneal collagen cross-linking（CXL） in combination with liposomal amphotericin B in fungal corneal ulcers.METHODS： New Zealand rabbits were induced fungal corneal ulcers by scratching and randomly divided into 3groups, i.e. control, treated with CXL, and combined therapy of CXL with 0.25% liposomal amphotericin B（n =5 each）. The corneal lesions were documented with slit-lamp and confocal microscopy on 3, 7, 14, 21 and 28 d after treatment. The corneas were examined with transmission electron microscopy（TEM） at 4wk.RESULTS： A rabbit corneal ulcer model of Fusarium was successfully established. The corneal epithelium defect areas in the two treatment groups were smaller than that in the control group on 3, 7, 14 and 21d（P 〈0.05）. The corneal epithelium defect areas of the combined group was smaller than that of the CXL group（P 〈0.05） on 7 and 14 d, but there were no statistical differences on 3, 21 and 28 d. The corneal epithelium defects of the two treatment groups have been healed by day 21. The corneal epithelium defects of the control group were healed on 28 d. The diameters of the corneal collagen fiber bundles（42.960 ±7.383 nm in the CXL group and 37.040±4.160 nm in the combined group） were thicker than that of the control group（24.900±1.868 nm）,but there was no difference between the two treatment groups. Some corneal collagen fiber bundles were distorted and with irregular arrangement, a large number of fibroblasts could be seen among them but no inflammatory cells in both treatment groups. CONCLUSION： CXL combined with liposomal amphotericin B have beneficial effects on fungal corneal ulcers. The combined therapy could alleviate corneal inflammattions, accelerate corneal repair, and shorten the course of disease.

Comparative 2-year outcomes of conventional and accelerated corneal collagen crosslinking in progressive keratoconus

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.

Scheimpflug imaged corneal changes on anterior and posterior surfaces after collagen cross-linking

AIM:To compare the anterior and posterior corneal parameters before and after collagen cross-linking therapy for keratoconus.METHODS:Collagen cross-linking was performed in31 eyes of 31 keratoconus patients(mean age 30.6±8.9y).Prior to treatment and an average 7mo after therapy,Scheimpflug analysis was performed using Pentacam HR.In addition to corneal thickness assessments,corneal radius,elevation,and aberrometric measurements were performed both on anterior and posterior corneal surfaces.Data obtained before and after surgery were statistically analyzed.RESULTS:In terms of horizontal and vertical corneal radius,and central corneal thickness no deviations were observed an average 7mo after operation.Corneal higher order aberration showed no difference neither on anterior nor on posterior corneal surfaces.During follow-up period,no significant deviation was detected regarding elevation values obtained by measurement in mm units between the 3.0-8.0 mm-zones.CONCLUSION:Corneal stabilization could be observed in terms of anterior and posterior corneal surfaces,elevation and higher order aberration values 7mo after collagen cross-linking therapy for keratoconus.

Clinical outcomes at one year following keratoconus treatment with accelerated transepithelial cross-linking

This study evaluated the clinical outcomes in keratoconus corneas following accelerated transepithelial corneal collagen cross-linking（CXL）（Avedro KXL system,Waltham,MA,USA） over one year of follow-up.The mean depth of the demarcation line measured by optical coherence tomography（OCT） was 205.19 μm.One month after surgery,a non-statistically significant change was noted in sphere（P= 0.18） and in spherical equivalent（P= 0.17）,whereas a significant improvement was observed in corrected distance visual acuity（P=0.04）.A significant change was observed in topographic astigmatism（P= 0.03） and posterior corneal a sphericity（P= 0.04）.Accelerated transepithelial CXL may be a useful technique for the management of progressive keratoconus.

Analysis of the effective dose of ultraviolet light in corneal cross-linking

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.

Topography versus non-topography-guided photorefractive keratectomy with corneal cross-linking variations in keratoconus

AIM:To compare the visual results of non-topographyguided and topography-guided photorefractive keratectomy(PRK)applying sequential and simultaneous corneal crosslinking(CXL)treatment for keratoconus.METHODS:Interventional and comparative prospective study.Sixty-nine eyes(36 patients)suffering from keratoconus(stages 1 Amsler-Krumeich classification)were divided into four groups:sequential topography-guided photorefractive keratectomy with CXL,simultaneous topography-guided photorefractive keratectomy with CXL,simultaneous nontopography guided photorefractive keratectomy with CXL,and sequential non-topography guided photorefractive keratectomy with CXL.The main outcome measures were pre-and postoperative uncorrected distance visual acuity(UDVA),best corrected distance visual acuity(CDVA),manifest refraction,contrast sensitivity,and keratometry.RESULTS:All analyzed visual,contrast sensitivity,and refractive parameters showed a significant improvement in the four groups(all P<0.05).A noticeable improvement was seen in keratometry in all the groups,and a remarkable difference was observed between topography-guided groups in comparison to non-topography-guided groups(P<0.05).Interestingly,the improvement in all parameters showed a degree of stability to the end of the follow-up.CONCLUSION:The treatment priorities in all four groups are safety,efficacy,and predictability in the correction of the sphero-cylindrical errors in mild and moderate keratoconus.No significant differences among groups in the recorded objective outcomes were found.

Corneal collagen crosslinking in keratoconus and other eye disease

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.

5-year follow-up of combined non-topography guided photorefractive keratectomy and corneal collagen cross linking for keratoconus

AIM： To evaluate the visual outcomes of simultaneous non-topography guided photorefractive keratectomy（PRK） and corneal collagen cross-linking（CXL） in eyes with keratoconus 5 y after the procedure.METHODS： Prospective, interventional, non-randomized, and non-controlled case series design was used. Sixty eyes of 30 patients（16 males and 14 females; age： 21-41 y） with mild, non-progressive（stages 1-2） keratoconus were enrolled. Refraction, uncorrected distance visual acuity（UDVA） and corrected distance visual acuity（CDVA）, flat and steep keratometry readings, and adverse events were evaluated preoperatively and postoperatively. Data were collected preoperatively and postoperatively at 3 mo, 1, 2, 3, 4, and 5 y follow-up visits after combined non-topography-guided PRK with CXL was performed. All patients had at least 5 y of follow-up.RESULTS： All study parameters showed a statistically significant improvement at 5 y over baseline values. The mean follow-up time was 68.20±4.71 mo（range： 60-106 mo）. Patients showed a significant improvement in UDVA from 1.24±0.79 log MAR prior to combined non-TG-PRK＋CXL to 0.06±0.15 log MAR postoperatively at the time of their last follow-up visit. CDVA significantly increased from 0.06±0.19 log MAR preoperatively to 0.03±0.12 log MAR postoperatively. A significant decrease in the mean spherical equivalent（SE） refraction was observed from-2.28±1.8 to-0.79±0.93 diopters（D）（P〈0.05）, and the manifest sphere decreased from-1.62±1.23 to-0.27±0.21 D（P=0.001）. The manifest cylinder significantly decreased from-1.73±0.86 to-0.29±0.34 D postoperatively（P=0.001）. The mean steep keratometry was 45.13±1.32 vs 47.28±2.12 D preoperatively（P〈0.05）, and the preoperative mean steepest keratometry（Kmax） 48.6±3.1 was reduced significantly to 46.8±2.9 postoperatively（P〈0.05）. CONCLUSION： Combined non-TG-PRK with 15 min CXL is an effective and safe option for correcting mild refractive error and improving visual acuity in patients with mild stable keratoconus.

Corneal collagen cross-linking epithelium-on vs. epithelium-off: a systematic review and meta-analysis

Background The purpose of the study was to determine the advantages and disadvantages of epi-on corneal cross-linking(CXL)techniques compared with standard epi-off CXL.Methods We searched MEDLINE and EMBASE for randomized controlled trials(RCTs)and non-randomized studies of interventions(NRSIs)and we evaluated the selected papers according to the Cochrane risk of bias tool.We considered,as primary outcomes,average Kmax flattening,changes in uncorrected and corrected distance visual acuity(UDVA and CDVA);as secondary outcomes,we considered changes in pachymetry values and endothelial cell density(ECD).We also investigated adverse events related to the treatments and treatment failure.Meta-analysis was conducted with a fixed or random-effects model using weighted mean difference(MD)with 95%confidence interval(CI)as the effect size.Results A total of 15 studies were included and among these 15 trials,9 were RCTs and 6 were NRSIs,but only 4 studies showed no high risk of bias and were included in this meta-analysis.Our analysis revealed significant postoperative differences in CDVA(MD=0.07;95%CI 0.04 to 0.10;P<0.001),and no significative differences in UDVA,Kmax,central corneal thickness(CCT)and ECD(P>0.05).Epi-on CXL protocol was found to be significantly less prompt to have risks of delay in epithelial healing(P=0.035)and persistent stromal haze(P=0.026).Conclusion Epi-on CXL is as effective as epi-off CXL.Except for a higher significant improvement in CDVA with current epi-on protocols,our meta-analysis demonstrates that epi-on and epi-off CXL have comparable effects on visual,topographic,pachymetric,and endothelial parameters.Epi-on CXL has clinical advantages in terms of comfort and avoidance of complications as it reduces the risk of developing delay in epithelial healing and persistent stromal haze.

应用带蒂角膜上皮瓣下等渗核黄素及恢复上皮瓣的快速角膜胶原交联术治疗薄圆锥角膜

目的:评估带蒂角膜上皮瓣下等渗核黄素及恢复上皮瓣的快速角膜胶原交联术(A-CXL)治疗过薄圆锥角膜(去上皮后角膜厚度小于400μm)患者的疗效和安全性。方法:回顾性研究。纳入2017-09/2020-12于成都中医大银海眼科医院屈光手术科治疗圆锥角膜患者46例74眼。根据术前最薄点角膜厚度(TCT)分为两组:TCT为400-<450μm的患者行带蒂角膜上皮瓣下等渗核黄素及恢复上皮瓣A-CXL 16例20眼,手术方法为做带蒂角膜上皮瓣并掀开,等渗核黄素滴眼,将角膜上皮瓣重新恢复后,进行紫外线照射,照射结束后,刮除角膜上皮瓣。TCT≥450μm的患者行去上皮A-CXL手术30例54眼。随访12 mo,收集所有患者手术前后最佳矫正视力(BCVA)、Sirius三维角膜地形图、角膜内皮细胞密度检查结果。结果:术后12 mo,带蒂角膜上皮瓣A-CXL组患者Kmax较术前无差异(P>0.005),去上皮A-CXL组患者Kmax较术前显著降低(P<0.005)。两组术后12 mo BCVA(LogMAR)、角膜前后表面曲率(K1、K2)及角膜内皮细胞密度较术前均无差异(均P>0.005)。两组各指标术后12 mo与术前变化量比较均无差异(均P>0.05)。结论:带蒂角膜上皮瓣下等渗核黄素及恢复上皮瓣A-CXL对于TCT为400-<450μm圆锥角膜患者安全可行,与去上皮A-CXL手术控制圆锥角膜进展的趋势相似。

Combined corneal CXL and photorefractive keratectomy for treatment of keratoconus: a review

Keratoconus and iatrogenic keratectasia are the corneal ectatic disorders occurring due to biomechanical weakening of the cornea resulting in distorted images,myopia, and irregular astigmatism. Corneal collagen cross-linking(CXL) is performed to arrest keratoconus successfully. The main aim of this review is to discuss the safety and efficacy of the adjuvant therapies, such as the combination of CXL and photorefractive keratectomy(PRK) for the treatment of corneal ectatic disorders. A comprehensive literature search was performed using PubM ed, MEDLINE, and Scopus using keywords ‘collagen’‘keratoconus’,‘keratectasia’,‘collagen cross-linking’,and ‘photorefractive keratectomy’. Search results were restricted to clinical studies published in English. Corneal CXL effectively arrests the progression of keratoconus by enhancing corneal rigidity. However, functional vision is not improved by cross-linking. Combining CXL to refractive surgeries such as topography-guided PRK or transepithelial PRK is found to be a safe and effective method in providing corneal stability as well as significantly improving functional visual acuity with few minor complications. This combined technique also prevents regression of keratoconus and reduce the risk of keratectasia. CXL combined with PRK is a promising therapeutic approach in ophthalmology that can be successfully used to treat progressive keratoconus and other corneal ectatic disorders and to enhance visual acuity.

去上皮与跨上皮快速角膜交联术在圆锥角膜中的疗效对比

目的对比去上皮与跨上皮快速角膜交联术(accelerated corneal collagen crosslinking,ACXL)在圆锥角膜中的临床疗效.方法选取圆锥角膜患者45例(45只眼),按治疗方案不同分为A组和B组,A组(21例21只眼)行去上皮ACXL,B组(24例24只眼)行跨上皮ACXL.比较术前及术后3个月2组的视力[裸眼视力(uncorrected visual acuity,UCVA)和最佳矫正视力(best corrected visual acuity,BCVA)]、角膜最薄点厚度、角膜最大曲率、角膜后表面高度及角膜内皮(角膜内皮细胞密度和六边形角膜内皮细胞比率).结果术后3个月,2组的UCVA、BC-VA、角膜后表面高度、角膜内皮细胞密度、六边形角膜内皮细胞比率与术前比较差异均无统计学意义(P>0.05);术前及术后3个月,2组间UCVA、BCVA、角膜后表面高度、角膜内皮细胞密度和六边形角膜内皮细胞比率比较差异均无统计学意义(P>0.05).术前,2组间角膜最薄点厚度和角膜最大曲率比较差异均无统计学意义(P>0.05);术后3个月,2组的角膜最薄点厚度和角膜最大曲率均较术前小(P<0.001或P<0.05),且B组的角膜最薄点厚度和角膜最大曲率均较A组大(P<0.05).结论去上皮与跨上皮ACXL治疗圆锥角膜均有效,在改善角膜厚度和角膜曲率方面跨上皮ACXL略逊于去上皮ACXL.

Collagen cross-linking:when and how?A review of the state of the art of the technique and new perspectives

Since the late 1990s corneal crosslinking(CXL)has been proposed as a new possibility to stop progression of keratoconus or secondary corneal ectasia,with the promising aim to prevent progressive visual loss due to the evolution of the pathology and to delay or avoid invasive surgical procedures such as corneal transplantation.The possibility of strengthening corneal tissue by means of a photochemical reaction of corneal collagen by the combined action of Riboflavin and ultraviolet A irradiation(UVA),radically modified the conservative management of progressive corneal ectasia.This is a review of the state of the art of CXL,reporting basic and clinical evidence.The paper describes basic principles,advantages and limits of different CXL techniques and possible future evolution of the procedure.

快速跨上皮核黄素-紫外光角膜胶原交联治疗圆锥角膜的临床疗效和安全性评价

背景研究证实经典角膜胶原交联法（CXL）可有效控制圆锥角膜的进展及角膜扩张，但由于其需要去上皮，因此引起较多不良反应和并发症。目前跨上皮核黄素-紫外线CXL已开始在临床上使用，但其有效性和安全性评价的研究较少。目的评价快速跨上皮核黄素-紫外线CXL治疗圆锥角膜的安全性及有效性。方法采用前瞻性自身对照系列病例观察研究设计，纳入2014年3—10月在北京同仁医院眼科就诊的圆锥角膜患者28例46眼，采用快速跨上皮核黄素-紫外线CXL治疗，术后随访1年。分别于术前、术后1周及术后1个月、3个月、6个月和12个月测定术眼的视力、屈光度、中央角膜厚度（CCT）、角膜内皮细胞计数、角膜地形图参数、眼前节光学相干断层扫描仪检查结果及角膜生物力学参数，对术眼手术前后的检查指标进行比较，评价快速跨上皮核黄素-紫外线CXL治疗的有效性。对随访期间术眼的刺激症状和不良反应进行观察，评价快速跨上皮核黄素-紫外线CXL治疗的安全性。结果所有手术顺利，未发现术中并发症及术后感染。术眼术后1d出现轻度刺激症状，均于术后3d缓解或消失。术眼术后1个月及以后等效球镜度（SE）较术前降低，但手术前后总体比较差异无统计学意义（F=0．722，P=0．614）；术眼术后12个月术眼柱镜度（CD）明显低于术前，差异有统计学意义（t=3．242，P=0．004）。术眼手术后不同时间点角膜内皮细胞密度、角膜内皮细胞面积的变异系数（CV）及六边形角膜内皮细胞比率值均接近于术前值，总体比较差异均无统计学意义（F=0．246、0．465、0．981，均P〉0．05）。术眼术后3个月和6个月的角膜厚度值分别为（467．86±52．92）和（468．51±52．96）μm，高于术前的（453．91±45．78）μm，但差异均无统计学意义（t=0．236、0．469，均P〉0．05），术眼术后12个月角膜厚度值为（488．67±51．44）μm，明显高于术前值，差异有统计学意义（t=3．681，P=0．002）。术眼术后3、6和12个月角膜曲率最大值（Ks）、角膜曲率最小值（Kf）及角膜平均曲率值（Avek）逐渐下降，但手术前后不同时间点间总体比较差异均无统计学意义（F=0．592、0．897、1．029，均P〉0．05）。术后1个月角膜基质层可见高密度光反射条带者39眼，占84．78％，深度平均为（214．38±31．92）μm。手术前后不同时间点角膜滞后量（CH）及角膜阻力因素（CRF）值的总体比较差异均无统计学意义（F=1．268、0．894，均P〉0．05）。结论快速跨上皮核黄素-紫外线CXL后圆锥角膜的角膜厚度增加，曲率逐渐扁平，角膜应力增强，因此可以有效地阻止圆锥角膜的进展，此外圆锥角膜患者用快速跨上皮核黄素-紫外线CXL治疗后不影响角膜上皮和内皮细胞的形态和功能，治疗后刺激症状轻，安全性较好。

快速角膜胶原交联术治疗圆锥角膜的安全及有效性研究

目的评价快速角膜胶原交联术(accelerated corneal collagen crosslinking,A-CXL)治疗圆锥角膜的安全性及有效性。方法收集2017年4月至2018年3月在郑州市第二人民医院眼科确诊为进展期圆锥角膜的患者37例(61眼),使用Avedro快速角膜胶原交联系统(30 mW·cm-2,4 min)进行手术。随访12个月,观察术前及术后最佳矫正视力(best corrected visual acuity,BCVA)、角膜内皮细胞密度(endothelial cell density,ECD)、角膜内皮细胞面积变异系数(coefficient variation of cell size,CV)及六边形角膜内皮细胞比例(percentage of hexagonal cells,Hex)、等效球镜度(spherical equivalent,SE)、角膜前表面最大曲率(maximum keratometry,Kmax)、角膜后表面高度(posterior corneal elevation,PCE)、最薄点角膜厚度(thinnest corneal thickness,TCT)的变化。结果术后1个月眼前段光学相干断层扫描检查发现39眼(63.9%)交联术后角膜前中基质层信号增强,可见明显分界线,深度(278.2±45.6)μm;角膜ECD和Hex分别较术前平均下降(97.6±138.6)个和(7.8±14.8)%,差异均有统计学意义(均为P<0.05),术后3个月二者均恢复至术前水平;角膜CV由术前(35.6±8.0)%增加至(40.6±7.1)%,差异有显著统计学意义(P<0.01);术后3个月时为(37.3±6.8)%,与术前相比差异仍有统计学意义(P<0.05);术后6个月时恢复至术前水平。术后12个月,BCVA及SE均较术前明显改善,差异均有显著统计学意义(均为P<0.01);Kmax及TCT分别下降(2.06±2.51)D和(8.9±10.8)μm,差异均有显著统计学意义(均为P<0.01);PCE保持稳定,与术前差异无统计学意义(P>0.05)。结论A-CXL手术后早期会出现短暂可逆性内皮细胞数量下降及形态改变,该手术可明显改善圆锥角膜患者角膜形态及视力,阻止或延缓角膜膨隆的进展。

跨上皮快速角膜胶原交联术治疗进展期圆锥角膜

目的:研究跨上皮快速角膜胶原交联术(CXL)治疗进展期圆锥角膜的临床效果和安全性。方法:前瞻性自身前后对照研究。收集自2016-08/2019-11在我院进行跨上皮快速CXL的进展期圆锥角膜患者37例47眼,分析患者术前,术后1、3、6、12mo的裸眼视力(UCVA)和最佳矫正视力(BCVA)、屈光状态、角膜透明度、角膜前表面最大K值(Kmax)、角膜最薄点厚度、角膜内皮细胞计数、眼压。结果:术后1、3、6、12mo患者UCVA较术前提高,但总体比较无差异(F=1.372,P=0.261)。患者术后1、3、6、12mo的BCVA均较术前提高,总体比较有差异(F=3.308,P=0.019),进一步比较发现术后3、6、12mo的BCVA与术前比较有差异(P=0.04、0.01、0.007)。患者术后1、3、6、12mo的球镜度数、柱镜度数、Kmax、角膜最薄点厚度与术前总体比较无差异(F=0.293、1.378、2.448、1.970,P=0.881、0.258、0.061、0.116)。术后1mo患者角膜内皮细胞计数与术前比较无差异(t=1.156,P=0.25)。患者术后各时间点眼压与术前比较无差异(F=1.221,P=0.321)。术后7眼出现角膜Haze(1级~2级),术后3~6mo有5眼Haze消退,角膜恢复透明,1眼遗留角膜云翳,1眼角膜中央基质线状混浊,但均未对视力造成影响。结论:跨上皮快速CXL可以显著提高圆锥角膜患者BCVA,稳定患者屈光状态、角膜形态和厚度,阻止或延缓圆锥角膜进展,使患者获得更好的视功能,同时手术时间短,术后并发症少,具有较好的安全性。