Visual quality assessment after presbyopic laser in-situ keratomileusis

AIM： To assess visual quality after presbyopia correction using an aspheric ablation profile and a micro-monovision protocol. METHODS： This is a retrospective interventional study. Fifty-four eyes of 27 patients （mean age, 50.2±7.5y） who underwent presbyopia correction with an aspheric micro-monovision protocol were enrolled. The values of modulation transfer function （MTF） cutoff frequency, Strehl ratio, objective scattering index （OSI） and accommodation range were quantitatively assessed using the HD analyzer. Preoperative and postoperative contrast sensitivity （CS） at far （2.5 m） and near （40 cm） distance and higher-order aberrations （HOAs） were analyzed. Subjective visual satisfaction was evaluated by self-reported questionnaire regarding optical visual symptoms. RESULTS： One year after presbyopia correction, no significant differences were found in the MTF cutoff frequency, Strehl ratio and OSI, however, the lID analyzer accommodation range significantly differed postoperatively （P=0.004）. Postoperative CS at 12 and 18 cpd at near showed statistically significant improvement （P=0.020 and 0.008, respectively）. Visual performance by self-reported questionnaire revealed satisfactory results in terms of subjective visual quality improvement. CONCLUSION： Objective optical quality parameters show good visual outcomes. Subjective visual quality assessed by self-reported questionnaire in the presbyopia correction group show satisfactory results.

Microstructure evolution of laser solid forming of Ti-Al-V ternary system alloys from blended elemental powders

Morphology evolution of prior β grains of laser solid forming （LSF） Ti-xAl-yV （x 11,y 20） alloys from blended elemental powders is investigated. The formation mechanism of grain morphology is revealed by incorporating columnar to equiaxed transition （CET） mechanism during solidification. The morphology of prior β grains of LSF Ti-6Al-yV changes from columnar to equiaxed grains with increasing element V content from 4 to 20 wt.-%. This agrees well with CET theoretical prediction. Likewise, the grain morphology of LSF Ti-xAl-2V from blended elemental powders changes from large columnar to small equiaxed with increasing Al content from 2 to 11 wt.-%. The macro-morphologies of LSF Ti-8Al-2V and Ti-11Al-2V from blended elemental powders do not agree with CET predictions. This is caused by the increased disturbance effects of mixing enthalpy with increasing Al content, generated in the alloying process of Ti, Al, and V in the molten pool.

Presbyopic correction on the cornea

Purpose:The aim of this systematic review was to synthesize and appraise the evidence of the benefits of presbyopic correction on the cornea for visual function.Summary:Comprehensive search was conducted in MEDLINE using keywords like“presbylasik”,“presbyopic refractive surgery”,“corneal pseudoaccommodation”and“corneal multifocality”.We reviewed corrected and uncorrected visual acuities for distance and near(uncorrected distance visual acuity(UDVA),uncorrected near visual acuity(UNVA),corrected distance visual acuity(CDVA),distance corrected near visual acuity(DCNVA),corrected near visual acuity(CNVA)),along with the refractive outcomes in spherical equivalent(SE)and astigmatism comparing the differences observed between preoperative myopic and hyperopic patients,as well as among techniques.Thirty-one studies met the inclusion and quality criteria.Monovision provides excellent distance and near uncorrected acuities,but with a 17%retreatment and a 5%reversal rate.Initial multifocal ablations result in 12%loss of 2 or more lines of CDVA,and a 21%retreatment rate.Laser Blended Vision provides excellent UDVA,but with a 19%retreatment rate.Initial experiences with Supracor show moderate predictability and a 22%retreatment rate.Intracor results in 9%loss of 2 or more lines of CDVA.KAMRA provides excellent UDVA,with only a 1%retreatment rate,but a 6%reversal rate.Initial experiences with PresbyMAX provided excellent UNVA and DCNVA,showing excellent predictability and a 1%reversal rate.Conclusions:The findings have implications for clinicians and policymakers in the health-care industry and emphasize the need for additional trials examining this important and widely performed clinical procedure.