***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: PURPOSE : To evaluate 1‐year outcomes of corneal collagen crosslinking ( CXL ) for treatment of keratoconus and corneal ectasia . SETTING : Cornea and refractive surgery subspecialty practice . DESIGN : Prospect i ve r and omized controlled clinical trial . METHODS : Collagen crosslinking was performed in eyes with keratoconus or ectasia . The treatment group received st and ard CXL and the sham control group received riboflavin alone . Principal outcomes included uncorrected ( UDVA ) and corrected ( CDVA ) distance visual acuities , refraction , astigmatism , and topography‐derived outcomes of maximum and average keratometry ( K ) value . RESULTS : The UDVA improved significantly from 0.84 logMAR ± 0.34 ( SD ) ( 20/137 ) to 0.77 ± 0.37 logMAR ( 20/117 ) ( P = .04 ) and the CDVA , from 0.35 ± 0.24 logMAR ( 20/45 ) to 0.23 ± 0.21 logMAR ( 20/34 ) ( P<.001 ) . Fifteen patients ( 21.1 % ) gained and 1 patient lost ( 1.4 % ) 2 or more Snellen lines of CDVA . The maximum K value decreased from baseline by 1.7 ± 3.9 diopters ( D ) ( P<.001 ) , 2.0 ± 4.4 D ( P = .002 ) , and 1.0 ± 2.5 D ( P = .08 ) in the entire cohort , keratoconus subgroup , and ectasia subgroup , respectively . The maximum K value decreased by 2.0 D or more in 22 patients ( 31.0 % ) and increased by 2.0 D or more in 3 patients ( 4.2 % ) . CONCLUSIONS : Collagen crosslinking was effective in improving UDVA , CDVA , the maximum K value , and the average K value . Keratoconus patients had more improvement in topographic measurements than patients with ectasia . Both CDVA and maximum K value worsened between baseline and 1 month , followed by improvement between 1 , 3 , and 6 months and stabilization thereafter . Financial Disclosure : No author has a financial or proprietary interest in any material or method mentioned . Additional disclosure is found in the footnotes The aim was to assess one‐year changes in uncorrected and corrected contrast sensitivity ( CS ) and glare under scotopic conditions after accelerated cross‐linking ( CXL ) using the 18 mW/cm2 protocol for the treatment of progressive keratoconus and compare results with unoperated controls Purpose To compare the outcomes of the conventional and accelerated corneal collagen cross-linking ( CXL ) in patients with bilateral progressive keratoconus ( KC ) . Methods Fifteen consecutive patients with bilateral progressive KC were enrolled . In each patient , the fellow eyes were r and omly assigned to the conventional CXL ( 3 mW/cm2 for 30 min ) or accelerated CXL ( ACXL ) ( 9 mW/cm2 for 10 min ) groups . Manifest refraction ; uncorrected and corrected distant visual acuity ; maximum and mean keratometry ; corneal hysteresis and corneal resistance factor ; endothelial cell density and morphology ; central corneal thickness ; and wavefront aberrations were measured before and 12 months after the CXL . Results Manifest refraction spherical equivalent and refractive cylinder improved significantly only in conventional group . Uncorrected and corrected distant visual acuity did not change significantly in either group . Also there was no significant change in the maximum and mean keratometry after 12 months . There was significant decrease in central corneal thickness in both groups which was more prominent in conventional group . Endothelial cell density reduced only in the conventional group which was not statistically significant ( P = 0.147 ) . CH , CRF , and wavefront aberrations did not change significantly in either group . We did not observe any significant difference in the changes of the variables between the two groups . Conclusions Accelerated CXL with 9 mW/cm2 irradiation for 10 min had similar refractive , visual , keratometric , and aberrometric results and less adverse effects on the corneal thickness and endothelial cells as compared with the conventional method after 12 months follow-up . However , r and omized clinical trials with longer follow-ups and larger sample sizes are needed The recent introduction of accelerated crosslinking ( CXL ) has sparked a great amount of interest in the ophthalmic community . CXL causes corneal stromal collagen fibre stiffening through photopolymerisation of riboflavin.1,2 The setting s of conventional CXL , as per Dresden protocol , are 3 mW/cm irradiance from a 370-nm light source to illuminate the riboflavin-treated eye for 30 min leading to a cumulative dose of 5.4 J/cm.3 The concept of accelerated CXL is based on the Bunden – Roscoe reciprocity law,4 where an overall cumulative dose of 5.4 J/cm is achieved with treatment parameters set at higher intensity and simultaneous reduction in exposure time . In accordance with this , animal studies found that an equivalent corneal stiffness increase to conventional CXL can be achieved with illumination intensity of up to 40–45 mW/cm , corresponding to illumination times of B2 min.5 Although the Bunden – Roscoe reciprocity law may be valid for a certain dose range and therefore a true linear relationship between dose and time is unlikely to exist , the radicals that generate the cross-links are formed in a shorter period of time when the radiation intensity is increased from 3 to 10 mW/cm.6 Initial studies , performed on porcine eyes , showed that accelerated CXL performed at 10 mW/cm for 9 min was equivalent to conventional CXL in biomechanical stiffness.6,7 When the cornea is treated with conventional CXL a demarcation line is seen at B300mm.8,9 This demarcation line , seen in anterior segment optical coherence tomography ( AS-OCT ) , demonstrates the depth of treatment with the corneal stroma lying anterior to this demarcation line that has been cross-linked and hence strengthened . Although keratoconus , at least during its early stages , is a predominantly posterior corneal disease , it is thought to be the anterior weaker stroma that needs to be strengthened to halt disease progression and subsequent ectasia . It is precisely this part of the cornea that is treated and stiffened with accelerated CXL , as a demarcation line is seen with AS-OCT at an average depth of 100–150 mm.10 In addition , the fact that the photodynamic reaction is limited to the anterior 100–150 mm of the cornea enables treatment , at least in theory , of thin corneas ( o400 mm ) whose treatment is not routinely advisable with st and ard conventional CXL . Accelerated CXL would allow treatment of a considerably larger amount of patients compared with the conventional CXL . Favourable results have been observed with accelerated CXL and have been reported to be equal to conventional CXL.11 In a r and omised prospect i ve study of 21 patients with mean follow-up of 46 months , Kanellopoulos found that accelerated CXL was comparable with conventional CXL in terms of its visual improvement and longevity.11 Mean sphere was reduced by B2.5 dioptres in both groups . Both the accelerated and the conventional CXL groups had an average reduction in Kmax of 2–3 dioptres.11 Clinical ly , several studies have found no increase or significant endothelial loss in corneas that underwent accelerated CXL.10,11 Microscopically , more keratocyte apoptosis was observed in the accelerated CXL group immediately after treatment but a similar re population was observed after 6 months.10 There is transient nerve plexus damage due to epithelial debridement and irradiation . However , these microscopic differences observed immediately after accelerated CXL seem to be of little consequence in the long run.10 C O N T R O V E R S Y Eye ( 2014 ) 28 , 784–785 & 2014 Macmillan Publishers Limited All rights reserved 0950 - Abstract Purpose : To compare outcomes of accelerated and conventional corneal cross-linking ( CXL ) for progressive keratoconus ( KC ) . Material s and methods : Patients were divided into two groups as the accelerated CXL group and the conventional CXL group . The uncorrected distant visual acuity ( UDVA ) , corrected distant visual acuity ( CDVA ) , refraction and keratometric values were measured preoperatively and postoperatively . The data of the two groups were compared statistically . Results : The mean UDVA and CDVA were better at the six month postoperative when compared with preoperative values in two groups . While change in UDVA and CDVA was statistically significant in the accelerated CXL group ( p = 0.035 and p = 0.047 , respectively ) , it did not reach statistical significance in the conventional CXL group ( p = 0.184 and p = 0.113 , respectively ) . The decrease in the mean corneal power ( Km ) and maximum keratometric value ( Kmax ) were statistically significant in both groups ( p = 0.012 and 0.046 , respectively in the accelerated CXL group , p = 0.012 and 0.041 , respectively , in the conventional CXL group ) . There was no statistically significant difference in visual and refractive results between the two groups ( p > 0.05 ) . Conclusions : Refractive and visual results of the accelerated CXL method and the conventional CXL method for the treatment of KC in short time period were similar . The accelerated CXL method faster and provide high throughput of the patients Purpose To compare the 6‐month results of accelerated and st and ard collagen crosslinking ( CXL ) treatment of progressive keratoconus . Setting Noor Eye Hospital , Tehran , Iran . Design Prospect i ve r and omized clinical trial . Methods Two groups of eyes ( intervention and control ) received corneal collagen crosslinking ( CXL ) treatment . The intervention group received accelerated CXL ( 18 mW/cm2 , 5 minutes ) , and the control group received st and ard CXL ( 3 mW/cm2 , 30 minutes ) . The eyes were evaluated for changes in the visual indices , refraction , and topography preoperatively and 1 , 3 , and 6 months postoperatively and regarding corneal rigidity indices and the endothelial cell count ( ECC ) preoperatively and at 6 months . Results The study evaluated 62 eyes ( 31 patient ) in 2 groups . The mean changes in uncorrected ( P = .733 ) and corrected ( P = .646 ) distance visual acuities and manifest refraction spherical equivalent ( P = .598 ) did not differ statistically significantly between the 2 groups . The central corneal thickness was higher in the st and ard group than the accelerated group ( P = .025 ) . The mean decrease in the maximum keratometry ( K ) ( P = .865 ) and mean K ( P = .974 ) and the mean changes in the asphericity ( P = .272 ) were not statistically significantly different between the 2 groups . The mean changes in corneal hysteresis ( CH ) ( P = .548 ) and the corneal resistance factor ( CRF ) ( P = 1.000 ) , CH – CRF ( P = .282 ) , and the area under the peak 2 ( P = .260 ) were similar in both groups . The mean decrease in the ECC was not statistically significantly different between the 2 groups ( P = .218 ) . Conclusion Based on 6‐month results , accelerated and st and ard corneal CXL arrested the progression of keratoconus similarly . Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned Purpose . To evaluate the long-term results of accelerated corneal cross-linking ( CXL ) in patients with progressive keratoconus . Methods . Sixteen patients underwent accelerated CXL  at 6 mW/cm2 for 15 minutes in one eye . The follow-up visits were scheduled on 7 days , 14 days , and 3 , 12 , and 24 months after the treatment . Results . There were no significant differences ( P > 0.05 ) between preoperative and 2-year postoperative mean values , respectively , in terms of uncorrected visual acuity , best spectacle-corrected visual acuity , maximum keratometry K max⁡ , minimum keratometry K min⁡ , corneal astigmatism , and corneal eccentricity index . We noted a significant flattening of the cornea in 18.7 % of patients with a higher preoperative K max⁡ value ( > 50 D ) and its steepening in patients with a lower K max⁡ value ( < 50 D ) ( 6.25 % ) . There was no significant difference in the central corneal thickness and the apical corneal thickness preoperatively and 2 years postoperatively . The mean demarcation line depth was 282 ± 11 μm . Persistent corneal haze was noted in 25 % of patients . Conclusions . Accelerated CXL appears to be a relatively effective procedure for the treatment of keratoconus in 2-year follow-up PURPOSE To compare the long-term outcomes of accelerated and st and ard corneal cross-linking protocol s in the treatment of progressive keratoconus . DESIGN Prospect i ve r and omized clinical trial . METHODS Thirty-one eyes with keratoconus were treated with an accelerated protocol ( 18 mW/cm(2 ) , 5 min ) and all contralateral eyes were treated with the st and ard method ( 3 mW/cm(2 ) 
    Output:
    
Analysis of variance of one-year changes showed that longer irradiation times were associated with a greater corneal flattening effect , although there was no difference in terms of improvement in vision or refraction .