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PubMed2005

A vision of our own.

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Accommodation, Ocular↗
PubMed2005

Feasibility and development of a high-power real accommodating intraocular lens.

PURPOSE: To develop an accommodating intraocular lens (IOL) that changes power with ciliary body action and generates a minimum of 8.0 diopters (D) by manipulation of a flexible material between a sulcus-fixated rigid plate and a ciliary muscle-operated capsular diaphragm. SETTING: Vissum-Instituto Oftalmológico de Alicante and Miguel Hernández University, Alicante, Spain. METHODS: The feasibility of the concept was tested by a laboratory lens model. An implantable measuring device was constructed to simulate the lens action. The device was implanted in monkey eyes to measure the various parameters involved with such IOLs. Based on these measurements, an accommodating IOL prototype was built and implanted in monkeys' eyes. Pharmacologic agents were used to achieve ciliary relaxation and spasm. Ultrasound biomicroscopy (UBM) imaging was used to document the active changes of the IOL flexible lens curvature as related to the ciliary muscles status. RESULTS: The laboratory model produced more than 50.0 D of accommodation. The UBM demonstrated changes in lens curvature between cyclospasm to cycloplegia of calculated 9.0 to 53.0 D for flexible material with a refractive index of 1.41. CONCLUSIONS: Flexible material is capable of being manipulated when placed between a scleral-fixated rigid plane and the ciliary muscles-operated capsular diaphragm. Such manipulation as used by the IOL concept presented here has generated an active change of more than 40.0 D in the monkey eye.

Accommodation, Ocular↗
PubMed2006

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.

Accommodation, Ocular↗
PubMed2006

Pseudophakic accommodation with 2 models of foldable intraocular lenses.

PURPOSE: To evaluate the amplitude of pseudophakic accommodation of 2 foldable intraocular lenses (IOLs) by measuring the anterior chamber depth (ACD) shift during a 1-year follow-up. SETTING: Department of Ophthalmology, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary. METHODS: This prospective study comprised 44 eyes of 44 cataract patients operated on with phacoemulsification and in-the-bag implantation of Akreos Disc (22 eyes) or AcrySof MA60BM (22 eyes) IOLs. The ACD was measured by A-scan during fixation at 30 cm and again after instillation of cyclopentolate 1%. The ACD shift was calculated by subtracting the ACD under cyclopentolate from the ACD during fixation at 30 cm. Follow-up measurements were performed 3, 6, and 12 months after surgery. Statistical analysis concerning the difference between the 2 groups was done by the Student unpaired t test. RESULTS: The ACD shift was greater in the AcrySof group than in the Akreos Disc group at all 3 follow-up examinations. The difference was highly significant between the 2 groups at 6 and 12 months (both P = .004). After the operation, the ACD shift increased continuously with time in both groups. The mean ACD shift reached 0.57 mm +/- 0.25 (SD) in the AcrySof group and 0.42 +/- 0.24 mm in the Akreos group at 12 months. CONCLUSIONS: The 3-piece AcrySof MA60BM IOL with 10-degree posterior angulation had a significantly higher capacity for pseudophakic accommodation than the 1-piece plate-haptic Akreos Disc IOL. The continuous increase in the ACD shift in the postoperative period may mean that patients learn to achieve better accommodation with an IOL as time goes on.

Accommodation, Ocular↗
PubMed2006

Optical analysis of an accommodating intraocular lens.

PURPOSE: To model the feasibility of an accommodating intraocular lens (IOL) that allows near vision by means of an anterior translation within the capsular bag. SETTING: University of Waterloo, Waterloo, Ontario, Canada. METHODS: Model eyes were constructed and analyzed based on experimental data using Code V, a computerized optical design tool. The potential near vision of IOLs of different powers was calculated as they were moved anteriorly within the capsular bag. The conditions under which a spherical lens performs well and when an aspheric design should be considered were determined. RESULTS: Accommodation (the dioptric change from the far to the near point) varies linearly with lens movement and is sensitive to corneal and IOL powers. Simple equations were derived and accurately predicted induced accommodation. Retinal image quality varies significantly with pupil size and IOL power. However, image quality is minimally affected by the amount of induced accommodation. CONCLUSIONS: From an optical standpoint accommodation with adequate image quality can be achieved by anterior movement of a spherical IOL within the capsular bag.

Accommodation, Ocular↗
PubMed2006

Biometry accuracy.

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Accommodation, Ocular↗
PubMed2006

Visual outcomes after accommodating intraocular lens implantation.

PURPOSE: To evaluate and compare the visual outcomes and accommodative amplitude in cataract patients after implantation of the Crystalens intraocular lens (IOL) (Eyeonics) versus standard monofocal IOLs. SETTING: Ten clinics in a nationwide multicenter study in the United States. METHODS: A multicenter comparative interventional case series with masked randomized postoperative examination of 224 eyes of 112 patients was performed by a single observer. Patients were divided into 2 groups (56 patients; 112 eyes each) depending on which IOL was implanted (Crystalens or monofocal). Accommodation was measured using 1 objective (dynamic retinoscopy) and 2 subjective methods (defocus and near point of accommodation). Visual acuity measurements were performed under the same conditions with standard visual acuity charts. RESULTS: Uncorrected monocular near vision was significantly better in the Crystalens group than in the standard monofocal group, with 101 of 112 eyes (90%) and 17 of 112 (15%), respectfully, reading J3 or better postoperatively. All 56 Crystalens patients had a binocular uncorrected near visual acuity of J3 or better compared with 16 of 56 (29%) standard monofocal patients. The mean postoperative monocular (0.85 +/- 0.30 [SD] versus 0.70 +/- 0.19, P<.01) and binocular (1.16 +/- 0.17 versus 1.01 +/- 0.14, P<.01) distance uncorrected visual acuities were also better in the Crystalens group than in the control group. All patients in the study achieved a corrected distance visual acuity of 20/20 or better. Measures of accommodation were significantly higher in Crystalens patients than in the monofocal IOL patients (dynamic retinoscopy 2.42 +/- 0.39 diopters [D] versus 0.91 +/- 0.24 D, P<.01; monocular defocus 1.74 +/- 0.48 D versus 0.75 +/- 0.25 D, P<.01; monocular near point of accommodation 9.5 +/- 3.1 inches versus 34.7 +/- 9.8 inches, P<.01). Perceived accommodation (5.79 D) was significantly greater than the measured accommodation (1.96 to 2.42 D) in Crystalens patients (paired t test, P<.01). CONCLUSIONS: The Crystalens IOL provided better uncorrected near and distance visual outcomes than standard monofocal IOLs in all analyses performed. Patients perceived a greater accommodation than measured. Understanding why this occurred could lead to valuable advances in accommodating IOL technology.

Accommodation, Ocular↗
PubMed2006

Objective measurement of intraocular lens movement and dioptric change with a focus shift accommodating intraocular lens.

PURPOSE: To objectively measure the shift and refractive change of the 1CU accommodating intraocular lens (IOL) (HumanOptics) and compare them to that of a monofocal AcrySof MA30 IOL (Alcon Laboratories) in the fellow eye. SETTING: Ophthalmology Department, St. Thomas' Hospital, London, United Kingdom. METHODS: Thirty patients who had bilateral cataract surgery 18 to 24 months previously with a 1CU IOL prospectively randomly allocated to 1 eye and an AcrySof MA30 monofocal IOL to the other eye were examined. Distance correction, near vision, reading fluency, near point, and defocus to minus spheres were measured. Intraocular lens shift to an accommodative stimulus following instillation of pilocarpine 4% was measured with the ACMaster. Refractive change between distance and near was measured with the Tracey wavefront analyzer. RESULTS: Of the original 30 patients recruited, complete measurements could only be obtained for 20. There was no significant difference in near visual function with either IOL. A small anterior movement of the 1CU was seen with accommodation 0.010 mm +/- 0.028 (SD). After pilocarpine 4% instillation, a forward movement of 0.220 +/- 0.169 mm was seen with the 1CU compared to a backward movement of 0.028 +/- 0.095 with the MA30. There was no significant correlation between distance corrected near visual acuity and IOL movement. No change in spherical equivalent between distance and near was seen on wavefront analysis of either IOL. CONCLUSIONS: Small forward movement of the 1CU IOL was seen with accommodation and increased following pilocarpine, compared to the posterior movement of the MA30 IOL. The amount of the IOL shift was not sufficient to provide useful near vision, but the difference suggests that the engineering concept behind the 1CU IOL is valid.

Accommodation, Ocular↗
PubMed2006

Clinical evaluation of the Crystalens AT-45 accommodating intraocular lens: results of the U.S. Food and Drug Administration clinical trial.

PURPOSE: To evaluate the 12-month U.S. phase II clinical trial results of the Crystalens AT-45 (eyeonics, Inc.) intraocular lens (IOL) used to provide uncorrected distance, intermediate, and near visual acuities in patients having cataract extraction and to compare in a substudy the contrast sensitivity and near visual acuity in patients with the Crystalens AT-45 IOL and those receiving a standard IOL. SETTING: Fourteen clinical sites throughout the U.S. for efficacy and 3 non-U.S. sites for safety and efficacy. METHODS: Patients 50 years or older had small-incision cataract extraction with implantation of the Crystalens AT-45 IOL. Unilateral implantation was followed by fellow-eye implantation. Postoperatively, uncorrected distance, near, and intermediate visual acuities were determined. Near and intermediate visual acuities were tested through a distance correction to eliminate potential pseudoaccommodative effects of residual myopia and corneal cylinder. A substudy tested contrast sensitivity under mesopic conditions with and without glare, as well as visual acuity in a subset of Crystalens AT-45 patients and a control group receiving a standard IOL. RESULTS: A total of 263 patients participated in the U.S. clinical trial and had 1 year of follow-up. Near visual acuities through the distance correction of 20/40 (J3) or better, monocularly and bilaterally, respectively, were seen in 90.1% and 100%; intermediate near visual acuities were seen in 99.6% and 100%. More than half the bilaterally implanted Crystalens AT-45 patients achieved uncorrected near acuity of 20/25 (J1) or better through the distance correction, and 84% achieved 20/32 (J2) or better. In the substudy, monocular near vision through the distance correction of 20/25 (J1) or better was seen in 50.4% with the Crystalens AT-45 IOL and in 4.7% with the standard IOLs. Mesopic contrast sensitivity results with and without glare for the Crystalens AT-45 were similar to those with standard monofocal IOLs. Nearly all patients (74 patients; 97.3%) who bilaterally were within 0.50 diopter of plano postoperatively achieved 20/32 (J2) or better uncorrected near, intermediate, and distance visual acuities. CONCLUSIONS: The Crystalens AT-45 accommodating IOL provided good uncorrected near, intermediate, and distance vision in pseudophakic patients. Contrast sensitivity with the Crystalens AT-45 was not diminished relative to standard monofocal IOLs, and near and intermediate visual performance was significantly better than with standard IOLs.

Accommodation, Ocular↗
PubMed2006

Age-related behavior of posterior chamber lenses in myopic phakic eyes during accommodation measured by anterior segment partial coherence interferometry.

PURPOSE: To evaluate age-related position shifts of the crystalline lens and the implantable contact lens (ICL, Staar Surgical) by a new, commercially available, anterior segment partial coherence interferometer, the ACMaster (Carl Zeiss Meditec), during accommodation in myopic eyes. SETTING: ALZ Augenklinik, Munich, Germany. METHODS: Fifty-three eyes of 29 consecutive patients were measured after myopic ICL implantation before and during subjective accommodation to a stimulus of 3 diopters (D) by anterior segment partial coherence interferometry (PCI). Nine eyes were also measured with a 5.00 diopters (D) stimulus; 14 eyes were measured repeatedly at different visits. The mean patient age was 33 years +/- 9 (SD) (range 21 to 59 years). The preoperative mean sphere was -7.6 +/- 1.9 D (range -5.0 to -11.5 D) and the cylinder, -1.4 +/- 1.1 D (range 0 to -4.25 D). RESULTS: Older patients had a tendency toward smaller vaults on desaccommodation between the ICL and the crystalline lens compared to younger individuals. In younger patients, there was a decrease of the vault on accommodation, whereas it increased in older persons (P = .005). During accommodation, the more the anterior lens surface shifted forward, the more the ICL bulged (P = .005). The change in vaulting was significantly larger at 5.00 D than at 3.00 D accommodation stimulus (P = .012). CONCLUSIONS: The behavior of ICLs in relation to the crystalline lens during accommodation varied with age and could be shown by PCI. The position shift of the ICL depended on the initial vault at desaccommodation and the ability of the anterior lens surface to bulge forward. Even though the crystalline lens stiffened, and therefore accommodation deteriorated with age, there was still a movement of the ICL, pointing to the role of the ciliary muscle movement in accommodation.

Accommodation, Ocular↗