Accommodative intraocular lenses:where are we and where we are going

Presbyopia still remains the last frontier of refractive surgery.Its surgical management is under constant evolution due to the limitations that exist today with respect to its management,which is probably in relation with the multifactorial basis in which presbyopia is clinically developed in the human.Until currently,virtually all surgical techniques that have been proposed for its correction are based on the induction of pseudoaccommodation in the presbyopic eye,including multifocality.However,the real restoration of accommodation is more complex,and it has been tried by the use of different,so called,“accommodative”pseudophakic intraocular lenses(AIOL).Overall,the reported results with these lenses by independent authors have been modest in relation with the restoration of the accommodative power of the eye and these modest benefits are usually lost with time due to the long term changes in the capsular bag.This fact made these lenses to be almost abandoned in the last few years,but there are currently other AIOL models being used with innovative mechanisms of action and different anatomical support outside the capsular bag that offer encouraging preliminary results that could bring a new potential of application to these types of lenses.In this article,we will update the modern refractive surgeon about the fundamentals and provide updated information about the outcomes of AIOLs by reviewing the concept of accommodation,the different attempts that have been accomplished in the past,their demonstrated published results in human clinical trials,and the future alternatives that may arrive in the near future.

The use of intracorneal ring segments in keratoconus

Keratoconus is a corneal degeneration that usually appears during puberty and may seriously deteriorate the quality of life of the patients.This corneal disease is today the first indication of corneal transplantation in young patients.Until the last decade of the XX century,keratoplasty procedures were the only alternative to treat this pathological condition.In the beginning of the XXI century,intracorneal ring segments implantation was proposed as a therapeutic choice for treating keratoconus patients.Since then,several published articles have reported the benefits of this surgical procedure in treating this type of corneal ectatic disorder.The purpose of the present investigative work is to summarize the characteristic of the intracorneal ring segments and also to review the different features published in the literature in relation to this surgical technique for the treatment of keratoconus patients.

Artificial neural network to guide intracorneal ring segments implantation for keratoconus treatment:a pilot study

Background:To analyze the clinical results of an artificial neural network(ANN)that has been processed in order to improve the predictability of intracorneal ring segments(ICRS)implantation in keratoconus.Methods:This retrospective,comparative,nonrandomized,pilot,clinical study included a cohort of 20 keratoconic eyes implanted with intracorneal ring segments KeraRing(Mediphacos,Belo Horizonte,Brazil)using the ANN(ANN group)and 20 keratoconic eyes implanted with KeraRing using the manufacturer’s nomograms(nomogram group).Uncorrected distance visual acuity(UDVA),corrected distance visual acuity(CDVA)(visual acuity is expressed in decimal value and in LogMAR value in brackets),manifest refraction,corneal topography,tomography,aberrometry,pachymetry and volume analysis(Sirius System.CSO,Firenze,Italy)were performed during the preoperative visit;and the two groups,ANN group and nomogram group,did not differ significantly preoperatively in all of the parameters evaluated.These preoperative values were compared with the results obtained at the third-month visit.Mann-Whitney test and Wilcoxon test were used for the statistical analyses.Results:The spherical equivalent and the keratometric values decreased significantly in both groups.The CDVA improved from 0.60±0.23(0.22 LogMAR)pre-operatively to 0.73±0.21(0.14 LogMAR)post-operatively in the ANN group(p<0.005),and from 0.54±0.19(0.27 LogMAR)pre-operatively to 0.62±0.19(0.21 LogMAR)post-operatively in the nomogram group(p<0.01),with statistically significant difference between the two groups(p<0.05),being better in the ANN group.Coma-like aberrations decreased significantly in the ANN group,while in the nomogram group they did not change significantly,but no statistically significant difference was found between the two groups.Conclusions:ANN to guide ICRS provides an increase in the visual acuity,reduction in the spherical equivalent and improvement in the optical quality of keratoconus patients.ANN gives better results when compared with the manufacturer’s nomograms in terms of better corrected vision and reduction of the coma-like aberrations.The constant inclusion of new cases will make the predictability of ANN increasingly better as the software finetunes its learning.

Clinical outcomes with a new microincisional diffractive multifocal IOL

Background:To evaluate the refractive outcomes and the optical performance as well as the quality of life in patients implanted with a new diffractive multifocal intraocular lens(IOL).Methods:Prospective,clinical study including 41 cases of patients who underwent cataract surgery and were divided in two groups:group 1,including 20 eyes implanted with the multifocal IOL SeeLens MF(Hanita Lenses,Israel);group 2,21 eyes implanted with the Acrysof SA60AT IOL.Visual acuity,defocus curve,intraocular aberrations,contrast sensitivity function and quality of life were assessed during a follow up period of 6 months.Results:Significant improvement was observed in the uncorrected distance visual acuity(UDVA)and corrected distance visual acuity(CDVA)in both groups(p<0.02).The multifocal group showed better results in terms of uncorrected near visual acuity(UNVA)and distance-corrected near visual acuity(DCNVA)(p<0.01).Comparison of both groups showed better visual acuities for the multifocal IOL group in defocus levels from-3.0 D to-1.50 D(p≤0.01).At 6 months,there was a significant reduction of the internal higher order aberrations(p≤0.04).A significant increase in scotopic contrast sensitivity was detected for 6 cycles/°spatial frequency during follow up(p=0.04),but no significant changes were observed for the rest of spatial frequencies(p≥0.06).Visual Functioning Index(VF-14)questionnaire showed that patients reported high levels of satisfaction when performing daily tasks.Conclusions:The SeeLens MF IOL is able to successfully restore distance,near and intermediate visions after cataract surgery.It also provides functional intermediate vision with optimal intraocular optical quality.

Artificial neural network to guide intracorneal ring segments implantation for keratoconus treatment:a pilot study

Background:To analyze the clinical results of an artificial neural network(ANN)that has been processed in order to improve the predictability of intracorneal ring segments(ICRS)implantation in keratoconus.Methods:This retrospective,comparative,nonrandomized,pilot,clinical study included a cohort of 20 keratoconic eyes implanted with intracorneal ring segments KeraRing(Mediphacos,Belo Horizonte,Brazil)using the ANN(ANN group)and 20 keratoconic eyes implanted with KeraRing using the manufacturer's nomograms(nomogram group).Uncorrected distance visual acuity(UDVA),corrected distance visual acuity(CDVA)(visual acuity is expressed in decimal value and in logMAR value in brackets),manifest refraction,corneal topography,tomography,aberrometry,pachymetry and volume analysis(Sirius System,CSO,Firenze,Italy)were performed during the preoperative visit;and the two groups,ANN group and nomogram group,did not differ significantly preoperatively in all of the parameters evaluated.These preoperative values were compared with the results obtained at the third-month visit.Mann-Whitney test and Wilcox on test were used for the statistical analyses.Results:The spherical equivalent and the keratometric values decreased significantly in both groups.The CDVA improved from 0.60±0.23(0.22 logMAR)preoperatively to 0.73±0.21(0.14 logMAR)postoperatively in the ANN group(P<0.005),and from 0.54±0.19(0.27 logMAR)preoperatively to 0.62±0.19(0.21 logMAR)postoperatively in the nomogram group(P<0.01),with statistically significant difference between the two groups(P<0.05),being better in the ANN group.Coma-like aberrations decreased significantly in the ANN group,while in the nomogram group they did not change significantly,but no statistically significant difference was found between the two groups.Con elusions:ANN to guide ICRS provides an increase in the visual acuity,reduction in the spherical equivalent and improvement in the optical quality of keratoconus patients.ANN gives better results when compared with the manu facturer's no mograms in terms of better corrected vision and reduction of the coma-like aberrations.The constant inclusion of new cases will make the predictability of ANN increasingly better as the software finetunes its learning.