[Two years experience with the new accommodative 1 CU intraocular lens]

Accommodative Intraocular Lenses: Short-Term Visual Results of Two Different Lens Types

Purpose

To compare the ability of two types of accommodative intraocular lenses (IOLs) to provide uncorrected near and distance visual acuity (VA) after cataract surgery.

Methods

A total of 108 eyes of 75 patients underwent cataract surgery by phacoemulsification and IOL implantation either bilaterally or monocularly with one of two types of accommodative IOLs: the AT-45 lens (69 eyes) or the 1-CU lens (39 eyes). Patients were followed for up to 1 year after cataract surgery. Near VA was measured through the distance correction to obtain the true near vision effect of the accommodating IOL.

Results

Uncorrected distance VA of 20/30 or better was achieved by 84.6% of the bilaterally implanted 1-CU patients and 73.6% of the bilaterally implanted AT-45 IOL patients 1 year following surgery. Uncorrected near VA of J1 or better was achieved by 42% of the patients with the bilateral 1-CU implant and 36.8% of the patients with the bilateral AT-45 implant. For J3 or better near acuity, the values were 92.3% for the bilateral 1-CU patients and 84.2% for the bilateral AT-45 patients at 1 year. A total of 54% of the eyes with 1-CU implants underwent a mild myopic shift (<1.0 D), 21% had a mild hyperopic shift, and 45% of the eyes were emmetropic at 1 year.

Conclusions

Both accommodative IOLs provided good near and distance vision postoperatively. The 1-CU IOL appears clinically to provide slightly better uncorrected distance and distance-corrected near VA than the AT-45 lens.

Biomechanical eye model and measurement setup for investigating accommodating intraocular lenses

We present a biomechanical eye model to induce pseudophakic accommodative movement for evaluation of the focal shift of accommodative intraocular lenses. Therefore, an accommodative intraocular lens (IOL) was implanted into freshly enucleated porcine eyes. The eyes were glued into a mechanical apparatus to expand the ciliar body effectuating mechanical accommodation. An optical coherence tomographer was used to measure positional and geometrical changes of the IOL for different levels of expansion. The expansion unit allowed stretching of the globe of several millimeters. With the biomechanical eye model we were able to simulate the mechanical functionality of accommodation as well as to measure the lens vault and change in geometry. Accommodative vault could only be measured with an intact vitreous, indicating that the vitreous plays an important role for the functionality of accommodative IOLs.

Functionalised polysiloxanes as injectable, in situ curable accommodating intraocular lenses

The aged eye's ability to change focus (accommodation) may be restored by replacing the hardened natural lens with a soft gel. Functionalised polysiloxane macromonomers, designed for application as an injectable, in situ curable accommodating intraocular lens (A-IOL), were prepared via a two-step synthesis. Prepolymers were synthesised via ring opening polymerisation (ROP) of octamethylcyclotetrasiloxane (D(4)) and 2,4,6,8-tetramethylcyclotetrasiloxane (D(4)(H)) in toluene using trifluoromethanesulfonic acid (TfOH) as catalyst. Hexaethyldisiloxane (HEDS) was used as the end group to control the molecular weight of the prepolymers, which were then converted to macromonomers by hydrosilylation of the SiH groups with allyl methacrylate (AM) to introduce polymerisable groups. The resulting macromonomers had an injectable consistency and thus, were able to be injected into and refill the empty lens capsular bag. The macromonomers also contained a low ratio of polymerisable groups so that they may be cured on demand, in situ, under irradiation of blue light, in the presence of a photo-initiator, to form a soft polysiloxane gel (an intraocular lens) in the eye. The pre-cure viscosity and post-cure modulus of the polysiloxanes, which are crucial factors for an injectable, in situ curable A-IOL application, were controlled by adjusting the end group and D(4)(H) concentrations, respectively, in the ROP. The macromonomers were fully cured within 5 min under light irradiation, as shown by the rapid change in modulus monitored by photo-rheology. Ex vivo primate lens stretching experiments on an Ex Vivo Accommodation Simulator (EVAS) showed that the polysiloxane gel refilled lenses achieved over 60% of the accommodation amplitude of the natural lens. An in vivo biocompatibility study in rabbits using the lens refilling (Phaco-Ersatz) procedure demonstrated that the soft gels had good biocompatibility with the ocular tissue. The polysiloxane macromonomers meet the targeted optical and mechanical properties of a young natural crystalline lens and show promise as candidate materials for use as injectable, in situ curable A-IOLs for lens refilling procedures.

Biomechanical analysis of the accommodative apparatus in primates

BACKGROUND

The restoration of natural accommodation in the presbyopic and cataract affected eye is a subject of intense research effort. A new instrument has been developed to test the viability and efficacy of procedures and methods to restore accommodation ex vivo in animal or human eyes.

METHODS

A section of the globe containing the crystalline lens, zonules, ciliary muscle and sclera is bonded into eight curved shoes. After dissecting the sclera between the shoes, even radial load is applied to stretch the zonules and capsular bag to simulate the natural accommodative process. The associated change in optical power is measured using a modified Scheiner's disk method. Changes in the diameter of the lens and ciliary processes are recorded, as well as zonular load.

RESULTS

No effective change in power was observed for the three presbyopic human eyes under four millimetres diameter stretching; the diameter of the ciliary aperture increased by between 1.8 mm and 2.3 mm, while the maximum increase in lens diameter was 0.19 mm. For the three younger monkey eyes, the diameter of the ciliary aperture increased by 1.4 mm with a corresponding increase in the lens diameter of between 0.50 mm and 0.65 mm. Stretching forces were generally higher for the human than for the monkey eyes, reaching maxima of 35 mN and 52 mN, respectively. The monkey eyes changed power by between 9.1 and 10.1 dioptres. An almost identical, progressive increase for lens diameter, power and stretching force versus stretch distance was found for all three monkey eyes.

CONCLUSION

The better understanding of the mechanisms and forces involved in the primate accommodative apparatus will assist with the development of accommodating IOLs and other methods to restore accommodation.

[Measurement of accommodation using optical biometry]

BACKGROUND

Making accommodation possible for all age groups is a topic of great interest. We applied optical biometry in order to study the physiological mechanisms in detail. Longitudinal relations in the optical axis were measured during accommodation in volunteers of different ages and lens states.

METHODS

A total of 60 subjects (children, adolescents, adults, and pseudophakes) were examined using the IOL Master. We measured anterior chamber depth (ACD), axial length (AL), and changes in these two measurements during accommodation.

RESULTS

Near accommodation (NA) in adolescents caused the largest ACD decrease (0.14+/-0.03 mm). ACD decreased in adults during NA but not in pseudophakic patients of comparable age. AL increased during NA in all groups by 0.01+/-0.01 mm.

CONCLUSIONS

ACD decreased with age. Using a physiological stimulus, no change in ACD was measured during NA in pseudophakic patients. The documented increase in AL needs to be evaluated further.

Meta-analysis of accommodating intraocular lenses

Accommodating intraocular lenses (IOLs) based on the concept of optic shift were introduced to restore accommodation after cataract surgery. Currently, 3 types of accommodating IOLs are commercially available: 1CU (HumanOptics), BioComFold (Morcher), and AT-45 Crystalens (eyeonics, Inc.). We present a meta-analysis of the peer-reviewed data from studies of these IOLs that use optic-shift measurements and visual acuity as the main outcome measures. In the 6 randomized controlled studies, 5 of which studied the 1CU IOL, the visual acuity results showed moderate to no improvement in near visual acuity compared with control IOLs and a statistically significant but small and inter-patient variable anterior shift of the IOL optic after pilocarpine stimulation. More clinical trials with randomized, controlled, and patient- and examiner-masked study designs that follow the guidelines of evidence-based medicine are needed to prove a benefit of accommodating focus-shift IOLs.

Akkommodationsfähigkeit unter Einbeziehung refraktiver, biometrischer und demographischer Parameter

PURPOSE

The aim of this study was to evaluate the accommodation ability in healthy phakic eyes in relation to refraction and biometric parameters in order to get comparable results for patients with the accommodative 1 CU posterior chamber lens.

METHODS

The study included 120 normal eyes of 120 patients (77 males, 43 females, mean age: 40+/-18, range: 11-70 years). The inclusion criteria were spherical equivalent for distance refraction <2 D, astigmatism <1.5 D, and a best-corrected visual acuity > or =0.8. Exclusion criteria were diabetes, glaucoma, cataract, traumas, or previous surgery. Subjects were divided into six age groups at increments of 10 years. Each group consisted of 20 subjects. Measurements included subjective and objective refraction (D), the accommodation ability (D) assessed with an accommodometer, and biometric parameters using the IOLMaster. In addition, the relation of anterior chamber depth and length of the eye was calculated for analyzing the relationship of anterior eye segment and accommodation.

RESULTS

The spherical equivalent for distance refraction was 0.04+/-0.6 D with a range of -1.5 to 2.0 D. There was no sex-related significant difference of accommodation range. The accommodation range (D) decreased significantly with increasing age (p<0.0001, r=-0.895). The highest decrease could be found between the ages of 30 and 50 years. In subsequent years, the decline in accommodation ability was comparatively less. In association with the anterior chamber depth and the relation of anterior chamber depth and length of the eye, the accommodation ability fell with increasing age (p<0.001). The length of the eye did not correlate with the accommodation ability (p=0.8).

CONCLUSION

There is a strong relationship between accommodation ability and age. Accommodation ability decreases strongly from the 3rd to the 5th decade; after that the loss of accommodation ability is relatively lower. The increase in lens thickness during the life span can implicate a correlation between the change of anterior chamber depth in relation to the length of the eye and a decrease of accommodation ability. Our results confirm Duane's hypothesis of accommodation and age.

Predicting the performance of accommodating intraocular lenses using ray tracing

PURPOSE

To predict and compare the amount of accommodation achievable by pseudophakic accommodating intraocular lenses (IOLs) using optical ray-tracing analysis.

SETTING

Computational laboratory.

METHODS

Two-element IOLs (2E-IOL, with mobile front or back optical elements) were compared with single-element IOLs (1E-IOL). Modeling using computer-assisted ray tracing of both IOL types assumed lens elements were equiconvex/equiconcave. The 4 possible combinations of configurations representing a wide range of varying positive and negative power (up to +40 diopters [D]) of front and back optical elements were evaluated.

RESULTS

The 1E-IOLs offered limited amplitude of accommodation with axial shift (approximately 1.2 D/mm). For 2E-IOLs, configurations with high positive-power front elements returned the best amplitude of accommodation (up to approximately 3.0 D/mm when the front element power was +40 D).

CONCLUSIONS

Considering the maximum potential amounts of axial shifts available, 1E-IOLs were predicted to provide 1.0 D of accommodation or less and 2E-IOLs were predicted to provide up to 3.0 D to 4.0 D depending on design configuration and amount of axial shift achievable. Potential issues relating to accommodative aniseikonia and spherical aberration have been identified.

Contrast and glare sensitivity after implantation of AcrySof and Human Optics 1CU intraocular lenses

PURPOSE

To evaluate contrast and glare sensitivity of a newly developed, potentially accommodative intraocular lens.

METHODS

The clinical interventional prospective randomized study included 20 patients (23 eyes) undergoing standard phacoemulsification with clear cornea incision in topical anesthesia. In the study group (10 eyes), the 1CU Human Optics intraocular lens (optics diameter 5.5 mm) was implanted. The control group (13 eyes) received the monofocal AcrySof intraocular lens (optics diameter: 6.0 mm). Using a newly developed contrast measuring device, contrast and glare sensitivity were tested 4 weeks after surgery.

RESULTS

The study group and control group did not vary significantly in contrast (p=0.38) or glare sensitivity (p=0.52).

CONCLUSIONS

The results suggest that the newly developed 1CU Human Optics intraocular lens and the standard AcrySof intraocular lens do not vary significantly in glare and contrast sensitivity.

Early visual results with the 1CU accommodating intraocular lens

PURPOSE

To prospectively assess the clinical outcome after implantation of the 1CU accommodating intraocular lens (IOL) and a foldable acrylic IOL (AcrySof, Alcon).

SETTING

Department of Ophthalmology, Tokyo Dental College, Ichikawa Hospital, Ichikawa, and Minami Aoyama Eye Clinics, Tokyo, Yokohama, Japan.

METHODS

Twenty-two eyes of 16 patients with cataract had phacoemulsification implantation of 1CU accommodating IOL. Twenty eyes of 10 age-matched and sex-matched patients with cataract had the same surgery but with a foldable acrylic IOL. All patients had assessments of the amplitude of accommodation, refraction, uncorrected and best corrected distance and near visual acuity, and distance corrected near visual acuity before surgery up to 12 months after surgery. Contrast visual acuities were measured 1 year after surgery. Anterior segment photography, intraocular pressure measurements, specular microscopy, and computerized topography were also performed.

RESULTS

The final best corrected distance visual acuity was above 20/25 in all eyes with the 1CU and the AcrySof IOLs. The mean distance corrected near visual acuity was significantly higher in the 1CU IOL group than in the acrylic IOL group after 3 months. None of the eyes with the AcrySof IOL implants displayed an accommodative response at any examination. The peak mean amplitude of accommodation with the 1CU IOLs was observed at 3 months and was 0.5 diopters +/- 0.44 (SD). Accommodation amplitude declined after 6 months.

CONCLUSION

The 1CU IOL provided additional near acuity postoperatively, but the benefit disappeared at 12 months with a concomitant decrease in accommodation amplitude owing to an increase in anterior and posterior capsular opacities.

Performance of the 1CU accommodating intraocular lens in relation to capsulorhexis size

PURPOSE

To assess the correlation between continuous curvilinear capsulorhexis (CCC) size and visual outcomes in patients with an accommodating intraocular lens (IOL).

SETTING

Heidelberg IOL and Refractive Surgery Research Group, Department of Ophthalmology, Ruprecht-Karls-University of Heidelberg, Heidelberg, Germany.

METHODS

Nineteen eyes had phacoemulsification and implantation of a 1CU accommodating IOL (HumanOptics AG). Three months after surgery, the uncorrected and best corrected distance and near visual acuities and the distance corrected near visual acuity were measured. Retroillumination photographs were taken to assess CCC size and centration and the amount of overlap between the CCC and IOL optic. The photographs were analyzed using Evaluation of Posterior Capsule Opacification system software.

RESULTS

The mean age of the patients was 53.5 years (range 30 to 73 years). The mean uncorrected distance acuity improved from 0.05 preoperatively to 0.70 at 3 months and the best corrected near acuity, from 0.30 to 0.94. The mean postoperative distance corrected near acuity was 0.5 (range 0.1 to 1.0), which improved to 0.9 with near correction. The mean CCC size (4.3 mm) and amount of CCC decentration (0.35 mm) did not correlate with visual outcomes. However, there was a correlation between the amount of CCC-optic overlap (mean 35%; range 16% to 55%) and distance corrected near acuity (r = 0.641, P = .003). Distance corrected near acuity was better with less overlapping; that is, with a larger CCC.

CONCLUSIONS

A larger capsulorhexis with less CCC-optic overlapping gave better near visual outcomes. Results indicate that an overlap between 25% and 35%, which correlates with a CCC between 4.5 mm and 5.0 mm, provides the best capsule strength without compromising accommodation with the single-piece 1CU IOL.

Accommodative intraocular lenses: current status

PURPOSE OF REVIEW

The possibility of using a monofocal IOL with accommodative ability allows refractive cataract surgery with a clearly decreased potential of photic phenomena. Three IOLs of different designs and materials have demonstrated accommodative ability, but the degree of accommodative amplitude has been reported to different extents and variabilities. The plate-haptic CrystaLens has a hinged design that might permit forward movement of the optic as a result of pressure changes in the vitreous cavity. The 1CU has modified haptics that bend in the bag as the lens capsule contracts, which are supposed to cause anterior displacement of the lens optic. With the dual-optic one-piece Synchrony, springlike haptics separate a high-plus anterior lens from a posterior minus lens. With accommodative effort, the capsular bag expands and the springs express kinetic energy, which might allow the optics to separate as the anterior lens moves forward.

RECENT FINDINGS

This article seeks to clarify and distinguish the concepts of true accommodation and pseudo accommodation. Current designs of accommodative IOLs are supposed to work by the focus-shift principle to allow true pseudophakic accommodation. Studies that biometrically assessed optic shift found no or only low amplitudes of forward movement. The amount of forward movement, if present, was highly variable between patients. To date, most studies present psychophysical data for the proof of concept, which alone seems insufficient. Capsule bag performance and posterior capsule opacification with accommodative IOLs seem worse than those with standard intraocular lenses.

SUMMARY

The potential clinical benefits of accommodative IOL technology for both cataract patients and refractive patients may place accommodative IOLs in a competitive position with multifocal IOL technology.

Accommodation after Nd: YAG capsulotomy in patients with accommodative posterior chamber lens 1CU

PURPOSE

After initial encouraging results with the accommodative 1CU posterior chamber lens (PCIOL), we investigated the rate, the postoperative time point of posterior capsular opacification (PCO) necessitating YAG capsulotomy and the accommodative range after Nd: YAG capsulotomy in patients with 1CU-PCIOL.

PATIENTS AND METHODS

This prospective clinical study included 65 patients who underwent phacoemulsification and implantation of the accommodative 1CU-PCIOL with postoperative follow-up from 3 to 24 months. Postoperative examination was performed 3, 6 and 12 months after surgery, then before and 6 weeks after Nd: YAG capsulotomy. Measurements included: the best corrected distance visual acuity, distance refraction, near visual acuity (Birkhauser charts in 35 cm) obtained with best distance correction, accommodative range measured by subjective near point with an accodommometer and defocusing with a visual acuity fall to 0.4.

RESULTS

Both best corrected distance visual acuity (1.1+/-0.1) and near visual acuity with best distance correction (0.4+/-0.1) remained stable over the follow-up period until 12 months postoperatively. The accommodative range determined by near point was stable (mean 2.0+/-0.5 D). Also, the defocusing range remained stable over 12 months (1.8+/-0.4 D). A clinically relevant posterior capsule opacification with a significant decrease of visual acuity (0.4+/-0.2) and a need for Nd: YAG capsulotomy was diagnosed in 12 patients between 15 and 22 (mean 20+/-4, median 20) months postoperatively. All capsulotomies were performed without complication. Six weeks after capsulotomy, best corrected distance visual acuity was improved (1.1+/-0.1), near visual acuity with best distance correction was 0.4+/-0.1 and the accommodative range determined by near point was 1.95+/-0.6 D and by defocusing was 1.88+/-0.47 D. Six weeks after capsulotomy, measurements of the accommodative range did not show any statistical difference to the 12-month results before the occurrence of PCO (P>0.5).

CONCLUSIONS

A clinically relevant PCO with a significant decrease of visual acuity necessitating Nd: YAG capsulotomy occurred mainly after 15 postoperative months in patients with 1CU. Our results indicate that Nd: YAG capsulotomy may not affect the accommodation ability of the 1CU. Nevertheless, long-term studies are needed to further analyze the accommodative properties.

Functional vision after cataract removal with multifocal and accommodating intraocular lens implantation

PURPOSE

To compare the efficacy (functional vision, spectacle dependence) of the Array multifocal intraocular lens (IOL) (Advanced Medical Optics) and the 1CU accommodating IOL (HumanOptics AG).

SETTING

Hartswood Hospital, Brentwood, United Kingdom.

METHODS

This prospective study comprised patients scheduled to have standard phacoemulsification surgery with IOL implantation. Patients expressing a preference for spectacle independence were allocated to the Array multifocal IOL group. Those expressing no preference received the 1CU accommodating IOL. Efficacy measures included distance and near uncorrected visual acuity (UCVA), dynamic retinoscopy, and patient-reported spectacle independence.

RESULTS

Seventeen patients (34 eyes) had bilateral implantation of the Array multifocal IOL, and 5 patients (9 eyes) had implantation of the 1CU accommodating IOL. Six to 18 months after surgery, 82.4% of eyes in the multifocal IOL group and 77.8% in the accommodating IOL group achieved a distance UCVA of 20/20 (Snellen) or better; the difference between groups was not significant. However, a significantly greater proportion in the multifocal IOL group than in the accommodating IOL group (76.5% versus 44.4%) achieved a near UCVA of N5 (Snellen 20/40) or better (P=.0068). Sixteen patients (94.1%) with Array IOLs and 2 patients (50.0%) with 1CU IOLs reported spectacle independence. Dynamic retinoscopy showed that the mean accommodative effect in the 1CU group was 0.44 diopter.

CONCLUSIONS

In this single-surgeon single-site study, a greater proportion of Array multifocal IOL recipients than 1CU IOL recipients achieved functional near visual acuity. Only 1 patient with an Array IOL required corrective spectacles at the last visit.

Correction of presbyopia with refractive multifocal phakic intraocular lenses

PURPOSE

To evaluate the efficacy of and specify the conditions required for implantation of an anterior chamber multifocal phakic intraocular lens (IOL) to correct presbyopia.

SETTING

Monticelli Clinic, Marseilles, France.

METHOD

Fifty-five eyes of 33 patients (21 women, 12 men) had implantation of a foldable anterior chamber multifocal phakic IOL. The initial refraction was between -5.00 diopters (D) and +5.00 D. The IOL had an addition of +2.50 D. An uncorrected distance acuity of 0.6 or better (decimal scale) and an uncorrected near acuity (Parinaud scale) of 3 or better (Parinaud 2 approximately equal to Jaeger 1) was considered a successful postoperative result.

RESULTS

The mean follow-up was 42.6 weeks +/- 18 (SD). Postoperatively, the mean refraction was -0.12 +/- 0.51 D, the mean decimal uncorrected distance acuity was 0.78 +/- 0.20, and the mean Parinaud uncorrected near acuity was 2.3 +/- 0.6. Eighty-four percent of eyes achieved an uncorrected distance acuity of 0.60 or better and an uncorrected near acuity of Parinaud 3 or better. The IOL was explanted in 4 eyes for different, but essentially optical, reasons. No significant anatomic complications were observed.

CONCLUSIONS

Implantation of an anterior chamber multifocal phakic IOL to correct presbyopia was effective and gave good predictability. The procedure is reversible in cases of patient intolerance to the IOL, unwanted optical phenomena, or complications. Strict inclusion criteria should be used for patient selection.

A mathematical model of factors that influence the performance of accommodative intraocular lenses

In this work a mathematical model of capsule movement during pseudophakic accommodation is described to allow identification and evaluation of factors that may explain the variation in effect of accommodative intraocular lenses (IOLs) between patients. The model assumes that increasing vitreous pressure pushes the lens capsule forward as a circular diaphragm and that this movement is from a fixed fulcrum. With an IOL in situ, the capsule is taken to have a non-uniform thickness due to the presence of the anterior capsulorhexis. The model assumes a uniform capsular elasticity and ignores contributions from cellular elements such as posterior capsule opacification. Using our model and a regression formula to calculate capsular bag size, taking into account axial length and keratometry values, we are able to predict accommodative effect in individual patients. By simple geometry we have developed a mathematical model to identify variables that are important in pseudophakic accommodation. It provides the basis for the development of a more complex model that would address the movement of a lens taking into account the influence of the zonular system during accommodation.

Difficult lens power calculations

PURPOSE OF REVIEW

Although cataract extraction seems to be feasible without major technical obstacles, the surgical technique has changed completely, and patients are no longer satisfied with good spectacle-corrected vision but anticipate complete visual rehabilitation after cataract surgery, without correction. To fulfill this desire, toric or accommodative intraocular lenses are of increasing popularity, and the intraocular lens power calculation after keratorefractive surgery has been improved.

RECENT FINDINGS

In this review article, we provide an overview of different mathematical strategies of calculating the intraocular lens power with standard formulas and with new algorithms, such as paraxial or numeric ray-tracing. These enhanced techniques may improve the validity of lens power calculation due to reduction of the prediction error, especially in cases with high or excessive corneal astigmatism and after refractive laser surgery. Furthermore, a new calculation scheme for the determination of bitoric eikonic intraocular lenses allows a distortion-free imaging in astigmatic eyes. The biometric determinants for the different formulas and calculation schemes are discussed in detail.

SUMMARY

In difficult cases, standard calculation schemes are overemployed and new mathematical algorithms are necessary to adequately address these problems. Ray-tracing algorithms and other complex mathematical computation schemes are of increasing interest and will more and more replace conventional calculation formulas for determination of intraocular lens power.