Long-term reading performance in patients with bilateral dual-optic accommodating intraocular lenses

BCLA CLEAR presbyopia: Management with intraocular lenses

Cataract surgery including intraocular lens (IOL) insertion, has been refined extensively since the first such procedure by Sir Harold Ridley in 1949. The intentional creation of monovision with IOLs using monofocal IOL designs has been reported since 1984. The first reported implantation of multifocal IOLs was published in 1987. Since then, various refractive and or diffractive multifocal IOLs have been commercialised. Most are concentric, but segmented IOLs are also available. The most popular are trifocal designs (overlaying two diffractive patterns to achieve additional focal planes at intermediate and near distances) and extended depth of focus designs which leave the patient largely spectacle independent with the reduced risk of bothersome contrast reduction and glare. As well as mini-monovision, surgical strategies to minimise the impact of presbyopia with IOLs includes mixing and matching lenses between the eyes and using IOLs whose power can be adjusted post-implantation. Various IOL designs to mimic the accommodative process have been tried including hinge optics, dual optics, lateral shifts lenses with cubic-type surfaces, lens refilling and curvature changing approaches, but issues in maintaining the active mechanism with post-surgical fibrosis, without causing ocular inflammation, remain a challenge. With careful patient selection, satisfaction rates with IOLs to manage presbyopia are high and anatomical or physiological complications rates are no higher than with monofocal IOLs.

Advances and challenges of intraocular lens design [Invited]

Phacoemulsification technique with intraocular lens implantation has been a common treatment for cataract patients. With rising demand among the public, new technologies for lens design have emerged to minimize intraocular aberrations, improving visual quality to the largest extent. This paper systematically reviews the development of materials applied in lens manufacturing, the different categories of intraocular lenses, and respective design principles. The advantages and potential drawbacks of intraocular lenses are illustrated in the paper, and prospective research to improve the design are presented in the end.

Clinical application of accommodating intraocular lens

The present review describes recent advances in application of accommodating intraocular lenses (AIOLs). Standard monofocal intraocular lenses (MIOLs) only correct distance vision, while AIOLs are designed to allow both good distance vision and near vision, which is achieved through the contraction and relaxation of ciliary muscles by providing transformation of the axial movement or curvature of the lens. Thus, AIOLs may be a better choice for those patients who demand a higher level of visual performance. Since techniques to analyze the performance of AIOLs have not been standardized, and there is a variety of both subjective and objective methods, it is hard to measure the performance of these intraocular lenses. By evaluating advantages and disadvantages of various AIOLs, and introducing techniques for measurement the performance postoperative, this paper can provide some relative information on choosing the type of AIOLs in the clinic.

Correction of presbyopia: An integrated update for the practical surgeon

Presbyopia results from loss or insufficiency of the eye's accommodative ability, and clinically manifests as the inability to focus near objects on the retina. It is one of the most common causes of visual impairment worldwide especially in adults of productive or working age. Various means of compensating for the loss of accommodative ability have been devised from optical tools such as spectacles and contact lenses, to topical medications and to surgical procedures. A comprehensive search on journal articles about topical and surgical correction of presbyopia was undertaken. The various techniques for presbyopia correction, as enumerated in these articles, are discussed in this paper with the addition of our personal experience and perspective on the future of these techniques.

Accommodating Intraocular Lenses

With an explosive increase in the worldwide prevalence of presbyopia, development of an accommodating intraocular lens (IOL) with expansive accommodative amplitude remains the holy grail in lens-based refractive surgery. A dynamic change in the dioptric power of the eye can be accomplished by various strategies alone or in combination, including changes in the position, shape, or refractive index of a single- or dual- optic IOL. This article reviews the cumulative advances in these various lens designs, along with clinical outcomes and complications of those that have been implanted. The challenges that remain in each cat-egory are also highlighted.

Development and validation of a new Chinese reading chart for children

PURPOSE

This study aimed to develop and validate a new Chinese reading chart for children. The characteristics of reading profiles among Hong Kong children were also investigated.

METHODS

A new reading chart was developed using the design principles of the MNREAD chart. Children (N = 169) aged seven to 11 years with normal vision and no developmental or reading difficulties were recruited from four local Hong Kong primary schools located in four different districts. Reading performance was measured using three versions of the new Chinese reading chart for children as well as six short passages. Repeated reading measures were conducted for 79 participants 4-8 weeks later. A linear mixed-model analysis was performed for the reading measures to identify the contribution of each source of variation (individual participant, among-charts within-session and between-sessions, and error) to the total variance.

RESULTS

Three reading parameters were derived from the Chinese reading chart for children - maximum reading speed (MRS), critical print size (CPS) and reading acuity (RA). Results from the linear mixed-model and Bland and Altman analyses revealed that all three versions of the chart were reproducible, with little variability among-charts and between-sessions (p < 0.001). The coefficient of repeatability for the MRS, CPS and RA was 0.08 logWPM, 0.16 logMAR and 0.14 logMAR respectively. The strong correlation between reading speed measured by the chart and ordinary children's reading passages confirmed the usefulness of the chart for assessing children's reading performance (Rc = 0.67, 95% CI of 0.60-0.73).

CONCLUSIONS

We developed and validated a new Chinese reading chart for children for quantifying reading performance in Chinese children with normal reading ability. This standardised clinical test can be reliably used to measure the MRS, CPS and RA in Chinese-speaking children. Further research is needed to evaluate the validity of this chart for assessing reading performance in Chinese children with reading difficulties, dyslexia or low vision.

Deformable Surface Accommodating Intraocular Lens: Second Generation Prototype Design Methodology and Testing

PURPOSE

Present an analysis methodology for developing and evaluating accommodating intraocular lenses incorporating a deformable interface.

METHODS

The next generation design of extruded gel interface intraocular lens is presented. A prototype based upon similar previously in vivo proven design was tested with measurements of actuation force, lens power, interface contour, optical transfer function, and visual Strehl ratio. Prototype verified mathematical models were used to optimize optical and mechanical design parameters to maximize the image quality and minimize the required force to accommodate.

RESULTS

The prototype lens produced adequate image quality with the available physiologic accommodating force. The iterative mathematical modeling based upon the prototype yielded maximized optical and mechanical performance through maximum allowable gel thickness to extrusion diameter ratio, maximum feasible refractive index change at the interface, and minimum gel material properties in Poisson's ratio and Young's modulus.

CONCLUSIONS

The design prototype performed well. It operated within the physiologic constraints of the human eye including the force available for full accommodative amplitude using the eye's natural focusing feedback, while maintaining image quality in the space available. The parameters that optimized optical and mechanical performance were delineated as those, which minimize both asphericity and actuation pressure. The design parameters outlined herein can be used as a template to maximize the performance of a deformable interface intraocular lens.

TRANSLATIONAL RELEVANCE

The article combines a multidisciplinary basic science approach from biomechanics, optical science, and ophthalmology to optimize an intraocular lens design suitable for preliminary animal trials.

Axial movement of the dual-optic accommodating intraocular lens for the correction of the presbyopia: optical performance and clinical outcomes

Presbyopia occurs in the aging eye due to changes in the ciliary muscle, zonular fibers, crystalline lens, and an increased lens sclerosis. As a consequence, the capacity of accommodation decreases, which hampers to focus near objects. With the aim of restoring near vision, different devices that produce multiple focuses have been developed and introduced. However, these devices are still unable to restore accommodation. In order to achieve that goal, dual-optic accommodating Intraocular Lenses have been designed, whose anterior optic displaces axially to increase ocular power, and focus near objects. Although dual-optic accommodating IOLs are relatively new, their outcomes are promising, as they provide large amplitudes of accommodation and a greater IOL displacement than single-optic accommodating IOLs. The outcomes show comfortable near vision, higher patients' satisfaction rates, and minimal postoperative complications like Posterior Capsular Opacification and Anterior Capsular Opacification, due to their design and material.

Clinical performance of a new aspheric dual-optic accommodating intraocular lens

Purpose

To describe the clinical performance of a new dual-optic intraocular lens (IOL) with an enhanced optic profile designed to mimic natural accommodation.

Patients and methods

Prospective multicenter clinical study with the new dual-optic aspheric accommodating IOL (Synchrony Vu) in 74 patients (148 eyes) undergoing cataract surgery. Refractive target was emmetropia. Examinations at 1 month and 6 months included subjective refractions; visual acuities at near, intermediate, and far; mesopic contrast sensitivity with and without glare; safety data; and subjective survey on dysphotopsia (halos and glare).

Results

Clinical data at 6 months showed 89% of the eyes within ±1.0 D spherical equivalent refraction. Mean binocular uncorrected and distance-corrected visual acuity was 20/20 at far (0.00±0.11 logMAR and −0.06±0.08 logMAR, respectively), 20/20 at intermediate (0.01±0.13 logMAR and −0.01±0.10 logMAR, respectively), and 20/25 at near (0.10±0.14 logMAR and 0.14±0.15 logMAR, respectively). Mesopic contrast sensitivity was within normal limits. Seventy-eight percent of the patients had no spectacles and 70% had no dysphotopsia. One eye had IOL repositioning within 1 month of surgery.

Conclusion

The new aspheric Synchrony Vu accommodating IOL provided good visual performance at a range of distances without affecting quality of vision and with minimal safety considerations.

Influence of intraocular lens implantation on anterior capsule contraction and posterior capsule opacification

PURPOSE

To evaluate whether and how intraocular lens (IOL) implantation influences the development of anterior capsule contraction and posterior capsule opacification (PCO).

SETTING

Department of Ophthalmology, Dokkyo Medical University, Mibu, Tochigi, Japan.

DESIGN

Experimental study.

METHODS

Phacoemulsification was performed in 8-week-old white rabbits. A hydrophobic acrylate IOL (12.5 mm) (YA-60BBR) was implanted in 1 eye and no IOL was implanted in the fellow eye. Slitlamp microscopy and anterior segment analysis were performed to evaluate anterior capsule contraction after the surgery. Four weeks postoperatively, sections of the eyes were made, and the thickness of the proliferated lens epithelial cell (LEC) layer at the posterior capsule was measured to assess the PCO. In addition, LECs from white rabbits were cultured in medium containing 50% aqueous humor or in medium containing 50% saline to determine the influence of the aqueous humor on LECs and to compare the degree of LEC proliferation.

RESULTS

Starting 2 weeks after surgery, anterior capsule contraction progressed more significantly in the IOL group than in the group without IOLs. Four weeks postoperatively, LEC thickness at the posterior capsule was significantly less in the group without IOLs than in the IOL group. In the culture study, LEC proliferation was more inhibited in the aqueous humor group than in the saline group.

CONCLUSIONS

Progression of anterior capsule contraction and PCO is less likely in aphakic eyes than in IOL-implanted eyes. The mechanism of prevention may involve aqueous humor-induced inhibition of LEC proliferation.

Outcomes of small aperture corneal inlay implantation in patients with pseudophakia

PURPOSE

To evaluate the improvement in near visual acuity after KAMRA corneal inlay (AcuFocus, Inc., Irvine, CA) implantation in patients with pseudophakia.

METHODS

A retrospective study analysis of patients with pseudophakia undergoing monocular corneal inlay implantation in the non-dominant eye was performed. The inlay was implanted monocularly in the non-dominant eye of patients. Manifest refractive spherical equivalent, uncorrected distance visual acuity, corrected distance visual acuity, uncorrected near visual acuity, and corrected near visual acuity were evaluated. The follow-up period was 3 months.

RESULTS

Thirteen eyes from 13 patients were evaluated. Four patients underwent LASIK for improved distance acuity at the time of inlay implantation. Mean uncorrected near visual acuity improved five lines (from J10 to J4) postoperatively. Mean uncorrected distance visual acuity, corrected distance visual acuity, and corrected near visual acuity remained stable and were 20/20, 20/16, and J1, respectively, before and after KAMRA implantation. Three eyes lost two lines and 1 eye lost one line of uncorrected distance visual acuity. Two eyes lost two lines and 1 eye lost 1 line of corrected distance visual acuity. Mean manifest refractive spherical equivalent changed before and after KAMRA implantation from -0.01 ± 1.07 diopters (D) (range: 2.25 to -1.88 D) to -1.12 ± 0.87 D (range: 0.25 to -2.75 D), respectively.

CONCLUSIONS

Implantation of a small aperture corneal inlay improved uncorrected near visual acuity while maintaining uncorrected and corrected distance visual acuity in monofocal patients with pseudophakia.

Visualization of the macula during elective pars plana vitrectomy in the presence of a dual-optic accommodating intraocular lens

We describe the case of a 69-year-old patient who had pars plana vitrectomy (PPV) for epiretinal membrane removal 18 months after cataract surgery with implantation of a dual-optic accommodating IOL (Synchrony). During PPV, visualization of the macula was perfect, and the postoperative visual outcome was excellent. To our knowledge, this is the first report of retinal visualization during PPV in the presence of a dual-optic accommodating IOL. When choosing a presbyopia-correcting IOL, surgeons should consider the advantage of macula visualization with an IOL with monofocal optics.

FINANCIAL DISCLOSURE(S)

Dr. Marques is a consultant to Abbott Medical Optics, Inc. No other author has a financial or proprietary interest in any material or method mentioned.

Quantification of age-related and per diopter accommodative changes of the lens and ciliary muscle in the emmetropic human eye

PURPOSE

To calculate age-related and per diopter (D) accommodative changes in crystalline lens and ciliary muscle dimensions in vivo in a single cohort of emmetropic human adults ages 30 to 50 years.

METHODS

The right eyes of 26 emmetropic adults were examined using ultrasonography, phakometry, anterior segment optical coherence tomography, and high resolution magnetic resonance imaging. Accommodation was measured both subjectively and objectively.

RESULTS

In agreement with previous research, older age was linearly correlated with a thicker lens, steeper anterior lens curvature, shallower anterior chamber, and lower lens equivalent refractive index (all P < 0.01). Age was not related to ciliary muscle ring diameter (CMRD) or lens equatorial diameter (LED). With accommodation, lens thickness increased (+0.064 mm/D, P < 0.001), LED decreased (-0.075 mm/D, P < 0.001), CMRD decreased (-0.105 mm/D, P < 0.001), and the ciliary muscle thickened anteriorly (+0.013 to +0.026 mm/D, P < 0.001) and thinned posteriorly (-0.011 to -0.015, P < 0.01). The changes per diopter of accommodation in LED, CMRD, and ciliary muscle thickness were not related to subject age.

CONCLUSIONS

The per diopter ciliary muscle contraction is age independent, even as total accommodative amplitude declines. Quantifying normal biometric dimensions of the accommodative structures and changes with age and accommodative effort will further the development of new IOLs designed to harness ciliary muscle forces.

Prevalence of corneal astigmatism before cataract surgery in Chinese patients

PURPOSE

To assess the demographics and distribution of corneal astigmatism before cataract surgery in Chinese patients.

SETTING

State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.

DESIGN

Clinic-based cross-sectional study.

METHODS

From July 2009 to May 2011, preoperative bilateral partial coherence interferometry (IOLMaster) was performed in consecutive patients having cataract surgery. Patient demographics and keratometric data were recorded.

RESULTS

The mean age of the 2849 patients (4831 eyes) was 70.56 years ± 9.55 (SD); there was a predominance of women patients (64.0%). The mean axial length was 23.58 ± 1.13 mm. The mean corneal astigmatism in this cohort was 1.01 D (range 0.05 to 6.59 D). Corneal astigmatism was between 0.25 D and 1.25 D in 67.7% of eyes, 1.25 D or higher in 27.5% eyes, and less than 0.25 D in 4.8% of eyes. Astigmatism was with the rule in 25.1% of eyes, against the rule (ATR) in 58.2% of eyes, and oblique in 16.7% of eyes. The mean steep keratometry measurement was 44.76 ± 1.56 D. Against-the-rule astigmatism increased significantly with older age.

CONCLUSIONS

Corneal astigmatism largely fell between 0.25 D and 1.25 D in these predominantly elderly female Chinese patients, and ATR astigmatism increased with age.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Five-year clinical study of patients with pseudophakic monovision

PURPOSE

To assess the long-term clinical outcomes and acceptability of pseudophakic monovision.

SETTING

Department of Ophthalmology, Kitasato University Hospital, Kanagawa, Japan.

DESIGN

Case series.

METHODS

Patients who had surgery using the monovision method with monofocal intraocular lenses had routine postoperative examinations. Assessed were visual acuity, near stereopsis, ocular deviation, patient satisfaction, and the rate of spectacle dependence preoperatively and 1, 3, and 6 months and 1, 2, 3, 4, and 5 years postoperatively.

RESULTS

The study enrolled 54 patients with a mean age of 74.7 years ± 7.9 (SD). The mean difference in the spherical equivalent refractive error between eyes of each patient was 2.13 diopters. The binocular uncorrected distance visual acuity was at least 0.10 logMAR in 98% of patients, with 76% achieving Jaeger 2 or better binocular uncorrected near visual acuity. Near stereopsis in patients who shifted from exophoria to intermittent exotropia decreased, although no serious problems were observed. The rate of spectacle dependence was 88% preoperatively, 41% at 1 year, and 22% at 5 years. Patient satisfaction improved gradually during the follow-up.

CONCLUSION

Pseudophakic monovision was an effective approach for correcting presbyopia throughout the 5-year observation period; however, a longer follow-up, including further studies is necessary to allow selection of appropriate patients.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.