Comparison of two types of visual quality analyzer for the measurement of high order aberrations

AIM： To compare the difference and agreement of KR- lW and iTrace for measurement of high order aberrations.METHODS： KR-1W and iTrace were respectively used in a group of healthy people （40 volunteers, 32 eyes） to measure the high order aberration （HOA） of corneal, internal and total ocular. The clinical difference and agreement of two instruments were respectively evaluated by paired-samples 1-test and Bland-Altman analysis. RESULTS： The paired-samples t-test showed that the corneal HOA measured by the two instruments had no statistical differences （P〉0.05）; but the internal and total ocular HOA had significant statistical differences （P〈 0.05）, and the mean results measured by iTrace were higher than that of KR-1W. However, Bland-Altman analysis revealed that the HOA of corneal and internal were all in 95% limits of agreement; and just one point of total ocular HOA was beyond the 95% limits of agreement. CONCLUSION： KR-1W and iTrace were consistent well in the measurement of corneal, internal and total ocular HOA, especially for the cornea.

Comparison of correcting myopia and astigmatism with SMILE or FS-LASIK and postoperative higher-order aberrations

AIM:To compare the effect of myopia and astigmatism correction and postoperative change in higher-order aberration as results of receiving small-incision lenticule extraction(SMILE)and femtosecond laser-assisted in situ keratomileusis(FS-LASIK).METHODS:A prospective and non-randomized controlled study was conducted.The subjects are divided into two groups according to different operations received:229 eyes of 116 patients in the SMILE group and 168 eyes of 86 patients in the FS-LASIK group.All subjects were followed up for 3 mo by monitoring their uncorrected visual acuity(UCVA),best-corrected visual acuity(BCVA),spherical equivalent,higher-order aberrations,and the preoperative and postoperative complications.RESULTS:At 1 wk,1,and 3 mo post-surgery,224 eyes(97.8%),227 eyes(99.1%)and 229 eyes(100%)had UCVA≥20/20 in the SMILE group,while 165 eyes(98.2%),167 eyes(99.4%)and 167 eyes(99.4%)had UCVA≥20/20 in the FS-LASIK group,respectively(χ^(2)=0.146,2.135,and 1.124;all P>0.05).BCVA reduction was not observed in both groups at 1 and 3 mo of post-surgery(χ^(2)=0.734 and 1.898,P>0.05).There was no statistically significant difference in the spherical equivalent between the two groups at 1 and 3 mo post-surgery,though the percentage of the spherical equivalent within±0.50 D at 3 mo postsurgery was 98%in the SMILE group,which was higherthan that of the FS-LASIK group(92%,χ^(2)=1.872,P>0.05).The root mean square(RMS)values of total high-order aberration,coma,and spherical aberration of the two groups increased significantly in the early postoperative period and decreased after 3 mo,but the values were still higher than the preoperative levels(P<0.05);there was no significant difference between the two groups in the RMS values of total higher-order aberrations and specific higherorder aberrations(P>0.05).The incidence of complications in the SMILE group was lower than that in the FS-LASIK group(χ^(2)=14.52,P<0.05).CONCLUSION:SMILE and FS-LASIK can effectively treat myopia,significantly improve visual acuity,and increase the total high-order aberration,spherical aberration,and coma.The incidence of complications after SMILE is relatively low.

Single-step transepithelial photorefractive keratectomy in high myopia：qualitative and quantitative visual functions

AIM：To investigate quantitative and qualitative optical outcomes of single-step transepithelial photorefractive keratectomy（Trans PRK）in high myopia.METHODS：In a prospective interventional case-series,30 eyes with high myopia（-6.00 to-8.75 D）with（up to-3.00 D）or without astigmatism were enrolled from Bina Eye Hospital,Tehran,Iran. One-step Trans PRK was performed with aberration-free aspherical optimized profile and SCHWIND AMARIS 500 laser. One-year follow-up results for refraction,visual acuities,vector analysis,ocular wavefront（OWF）and corneal wave-front（CWF）higher order aberrations（HOA）,contrast sensitivity（CS）,and postoperative haze were assessed.RESULTS：After the surgery,both photopic and mesopic CSs significantly improved（both P〈0.001）. We detected significant induction of OWF coma and trefoil（P〈0.001 for both）HOAs; CWF coma（P=0.002）,spherical（P〈0.001）,and tetrafoil（P=0.003）HOAs in 6 mm analysis diameter; and CWF trefoil（P=0.04）HOA in 4 mm analysis diameter. The range of mean induction observed for various HOAs was0.005-0.11 μm. The 86.7% of eyes reached an uncorrected distance visual acuity of 20/20 or better; 96.7% of eyes were within ±0.5 D of targeted spherical refraction. In vector analysis,mean correction index value was 1.03 and mean index of success was 0.22. By 12mo after the operation,no eye lost any number of corrected distancevisual acuity lines. We detected no corneal haze greater than 1~＋ throughout the follow-up.CONCLUSION：Our findings show promising effects of single-step Trans PRK on quality of vision in high myopic eyes. It also improves refraction and visual acuity.

Comparative analysis of the clinical outcomes between wavefront-guided and conventional femtosecond LASIK in myopia and myopia astigmatism

AIM:To compare the clinical outcomes of wavefront guided femtosecond LASIK(WFG LASIK)and conventional femtosecond LASIK(NWFG LASIK)in eyes with myopia and myopia astigmatism.METHODS:This was a retrospective,nonrandomized,comparative investigation enrolling 236 eyes of 122 patients(18-50 y)with low&moderate and high myopia.The WFG group including 97 eyes(50 patients)undergone WFG LASIK and the NWFG group including 139 eyes(72 patients)undergone conventional LASIK.Mean efficacy index,high order aberrations(HOAs),pupil size and the quality of visual questionnaire were evaluated 6 mo postoperatively.RESULTS:There is no difference between WFG group(-0.054±0.049 in logMAR)and NWFG group(-0.040±0.056)in uncorrected distance visual acuity(UDVA)postoperatively.The myopia astigmatism is higher in WFG group than that in NWFG group(P<0.05).However,the mean efficacy index(MEI)in the WFG group(1.09±0.106)is better than that in the NWFG group(1.036±0.124;P<0.001).Increased HOAs were observed in NWFG group(0.30±0.196)than that in WFG group(0.146±0.188;P<0.001).The pupil size is larger in WFG group(5.15±0.76 mm)than that in NWFG group(4.32±0.52 mm).The patients are satisfied with the clinical surgery,yet WFG group showed better visual quality using the questionnaire survey.Meanwhile,high myopia would result in worse MEI,HOAs and visual quality than low&moderate myopia.CONCLUSION:WFG and NWFG FS-LASIK are both effective and safe procedures to correct low&moderate and high myopia,but WFG FS-LASIK gives a better postoperative MEI,aberrometric control and predictable outcome.Meanwhile,WFG FS-LASIK is better than NWFG FS-LASIK in correction of myopia astigmatism.Low&moderate myopia allow better clinical outcomes than high myopia using any surgical method.

Tilt and decentration with various intraocular lenses: A narrative review

We find that tilt and decentration of intraocular lens (IOL) commonly cause visualquality deterioration after cataract surgery. Multiple factors affect IOL tilt anddecentration in the pre-, mid-, and post-operation phases. Moreover, the tilt anddecentration of 1-piece IOL are less correlated with internal ocular HOAs thanthose of 3-piece IOL. Aspherical IOLs are more sensitive to decentration or tiltthan spherical IOLs. Furthermore, the optical performance of toric IOLs with anaccurate axis remains stable irrespective of tilt and decentration. The opticalquality of asymmetric multifocal IOLs varies significantly after decentration andtilt in different directions. The image quality enhances or deteriorates in thedirection of the decentered IOL. An extended depth of focus IOL can achievegood visual acuity in the distant, intermediate, and near range. Additionally, itstilt and decentration have less impact on the vision than bifocal and trifocal IOL.This is the first review that compares the effect of IOL tilt and decentration onimage quality for various IOL designs. The result indicates that a deeperunderstanding of tilt and decentration of various IOLs can help achieve a bettervisual effect to visually improve refractive cataract surgery.

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.