Postoperative visual performance with a bifocal and trifocal diffractive intraocular lens during a 1-year follow-up

AIM：To evaluate and compare the clinical outcomes with a diffractive bifocal and trifocal intraocular lens（IOL）during a 12-month follow-up.METHODS：Prospective comparative study including75 eyes of 38 patients（44-70y）undergoing uneventful cataract surgery.Each patient was randomly assigned to one type of IOL,bifocal（35 eyes）or trifocal（40 eyes）.Visual,refractive,and contrast sensitivity changes were evaluated in a 12-month follow-up.The binocular defocus curve was also measured at 12mo postoperatively.RESULTS：No statistically significant differences between groups were found in postoperative uncorrected and corrected distance visual acuities（P≥0.276）.Postoperative corrected near visual acuity（33 cm）was significantly better in the trifocal group during all follow-up（P≤0.004）as well as 6-month uncorrected near（P=0.008）and distancecorrected near visual acuities（P=0.016）（33/40 cm）.Significantly better uncorrected intermediate and distance corrected-intermediate visual acuity were found during all follow-up in the trifocal group（P〈0.001）,which was consistent with differences among groups in binocular defocus curve.Differences among groups in contrast sensitivity were minimal,being only significant at 6 months for some low to medium spatial frequencies（P≤0.006）.CONCLUSION：Bifocal and trifocal diffractive IOLs are able to provide an effective visual restoration which is maintained during a 12-month follow-up,with a clear benefit of the trifocal IOL for the intermediate vision.

Comparison of trifocal toric and bifocal toric intraocular lens implantation in patients with cataract and high corneal astigmatism

AIM:To investigate and compare the quality of life,satisfaction,contrast sensitivity,glare,depth perception,and intraocular lens(IOL)rotation in patients who underwent trifocal toric and bifocal toric IOLs.METHODS:A total of 80 eyes of 40 patients were included in this prospective study.Twenty patients in each group were implanted with trifocal toric and bifocal toric IOL,respectively.Preoperative and postoperative 6-month measurements were recorded for both patient groups.Comprehensive anterior and posterior segment examinations,distance-intermediate-near visual acuity values and the visual function scale questionnaire results were evaluated at these examinations.Patient satisfaction,contrast sensitivity,glare,intermediate-near and distance stereopsis and IOL rotation were also evaluated.RESULTS:No significant difference was found between the groups in terms of distance and near visual acuities(P=0.269,P=0.451).Intermediate visual acuity was significantly increased in the trifocal toric group(P<0.001).The visual function scale results were increased after surgery in both groups(P=0.001 and P<0.001),with no difference determined between them(P=0.158 and P=0.691).The number of patients wearing glasses was low in both groups and there was no significant difference between the groups(P>0.05).The overall satisfaction in the trifocal toric group was significantly higher than in the bifocal toric group(P=0.03).The highest sensitivity was observed at 6 cpd spatial frequency in all patients under photopic conditions(1.80±0.24 logU,1.74±0.20 logU).Distance-intermediate-near binocular depth perception results in both groups were higher in the trifocal toric group(P=0.02,0.048,0.003,respectively).Although there was no significant difference for 3 meters stereopsis,the trifocal toric group had higher depth perception(P=0.577).Mean rotation was 5.76°±3.93°in the trifocal toric group and 12°±7.1°in the bifocal toric group.CONCLUSION:Better results in the middle distance are obtained in the trifocal toric group and less IOL rotation due to digital system-coordinated surgery.Moreover,the overall satisfaction in the trifocal toric group is significantly higher than in the bifocal toric group.

Multifocal and extended depth of focus intraocular lenses

Advances in intraocular lens(IOL)design have rendered cataract surgery a refractive procedure.Newer IOL types include bifocal,trifocal and extended depth of focus(EDOF)IOLs.Their basic difference nestles in the number of focal points that each lens provides,which in turn leads to different visual outcomes.Familiarity of surgeons with the various characteristics of each lens is of utmost importance for accurate IOL selection to match each patient’s needs.In this review,we aim to compare the clinical outcomes after implantation of multifocal and EDOF IOLs in terms of distance,intermediate and near vision,contrast sensitivity,and reading performance.Finally,we discuss the defocus curve and the optical and photic phenomena associated with each type of IOL.

Bifocal-Lens Converging Based OAM Wireless Communications

Orbital angular momentum(OAM)based radio vortex wireless communications have received much attention recently because it can significantly increase the spectrum efficiency.The uniform circular array(UCA)is a simple antenna structure for high spectrum efficiency radio vortex wireless communications.How-ever,the OAM based electromagnetic waves are vortically hollow and divergent,which may result in the signal loss.Moreover,the divergence of corresponding OAM based electromagnetic wave increases as the order of OAM-mode increases.Therefore,it is difficult to use high-order OAM-mode,because the corresponding received signal-to-noise ratio(SNR)is very small.To overcome the difficulty of high-order OAM modes transmission,in this paper we propose a lens antenna based electromagnetic waves converging scheme,which maintains the angular identification of multiple OAM-modes for radio vortex wireless communications.We further develop a bifocal lens antenna to not only converge the electromagnetic wave,but also compensate the SNR loss on traditional electromagnetic waves.Simulation results show that the proposed bifocal lens can converge the OAM waves into cylinder-like beams,providing an efficient way to in-crease the spectrum efficiency of wireless communications.