Crystalens HD intraocular lens analysis using an adaptive optics visual simulator

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.

Effect of even and odd-order aberrations on the accommodation response

AIM

To investigate the potential effect that odd and even-order monochromatic aberrations may have on the accommodation response of the human eye.

METHODS

Eight healthy subjects with astigmatism below 1 D, best corrected visual acuity 20/20 or better and normal findings in an ophthalmic examination were enrolled. An adaptive optics system was used in order to measure the accommodation response of the subjects' eyes under different conditions: with the natural aberrations being present, and with the odd and even-order aberrations being corrected. Three measurements of accommodation response were monocularly acquired at accommodation demands ranging from 0 to 4 D (0.5 D step).

RESULTS

The accommodative lag was greater for the accommodative demands of 1.5, 3, 3.5 and 4 D for the condition in which the even-order aberrations were corrected, in comparison to that obtained for the natural aberrations and corrected odd-order aberrations for the same accommodation demands. No statistically significant differences were found between the accommodation responses under the three conditions.

CONCLUSION

The odd and even-order aberrations are not helping the visual system to accommodate, because their partial correction do not affect the accommodation performance.

Psychophysical Vision Simulation of Diffractive Bifocal and Trifocal Intraocular Lenses

PURPOSE

The visual performance of monofocal, bifocal, and trifocal intraocular lenses was evaluated by human individuals using a vision simulator device. This allowed investigation of the visual impression after cataract surgery, without the need actually to implant the lenses.

METHODS

The randomized, double-masked, three-way cross-over study was conducted on 60 healthy male and female subjects aged between 18 and 35 years. Visual acuity (Early Treatment Diabetic Retinopathy Study; ETDRS) and contrast sensitivity tests (Pelli-Robson) under different lighting conditions (luminosities from 0.14-55 cd/m², mesopic to photopic) were performed at different distances.

RESULTS

Visual acuity tests showed no difference for corrected distance visual acuity data of bi- and trifocal lens prototypes (P = 0.851), but better results for the trifocal than for the bifocal lenses at distance corrected intermediate (P = 0.021) and distance corrected near visual acuity (P = 0.044). Contrast sensitivity showed no differences between bifocal and trifocal lenses at the distant (P = 0.984) and at the near position (P = 0.925), but better results for the trifocal lens at the intermediate position (P = 0.043). Visual acuity and contrast sensitivity showed a strong dependence on luminosity (P < 0.001).

CONCLUSIONS

At all investigated distances and all lighting conditions, the trifocal lens prototype often performed better, but never worse than the bifocal lens prototype.

TRANSLATIONAL RELEVANCE

The vision simulator can fill the gap between preclinical lens development and implantation studies by providing information of the perceived vision quality after cataract surgery without implantation. This can reduce implantation risks and promotes the development of new lens concepts due to the cost effective test procedure.

Visual Outcomes and Accommodative Response of the Lumina Accommodative Intraocular Lens

PURPOSE

To compare visual acuity, accommodation, and contrast sensitivity of the AkkoLens Lumina accommodative intraocular lens (AkkoLens Clinical b.v., Breda, The Netherlands) with a standard monofocal intraocular lens (IOL).

DESIGN

Randomized clinical trial.

METHODS

The study enrolled 86 eyes with cataract that all required cataract surgery and IOL implantation. The study group included 61 eyes that were implanted with the Lumina. The control group included 25 eyes that were implanted with an Acrysof SA60AT (Alcon, Fort Worth, TX, USA) monofocal IOL. The distance and near visual acuities, contrast sensitivity, and accommodation were measured over a 1-year follow-up period. Accommodation was measured subjectively, using defocus curves, and objectively, with an open-field autorefractor.

RESULTS

Uncorrected (UDVA) and corrected (CDVA) distance visual acuities did not differ significantly between the groups (P ≥ .21) over the 12 months. However, the uncorrected near visual acuity (UNVA) was 0.07 ± 0.08 logRAD for the Lumina group and 0.37 ± 0.19 logRAD for the control group (P < .01) and the corrected distance near visual acuity (CDNVA) was 0.11 ± 0.12 LogRAD for the Lumina group and 0.41 ± 0.15 LogRAD for the control group (P < .01). Defocus curves showed a statistically significant difference between groups for defocus ranging from -4.50 to -0.50 diopters (D) (P < .01) with significantly higher visual acuities for the Lumina group. Subjective accommodation, as determined from defocus curves, was 3.05 ± 1.06, 3.87 ± 1.27, and 5.59 ± 1.02 D for the Lumina group and 1.46 ± 0.54, 2.00 ± 0.52, and 3.67 ± 0.75 D for the control group at visual acuities of 0.10, 0.20, and 0.4 logMAR for both groups, respectively. The objective accommodation, measured by an open-field autorefractor, was 0.63 ± 0.41, 0.69 ± 0.45, 0.91 ± 0.51, and 1.27 ± 0.76 D for the Lumina group and 0.10 ± 0.15, 0.12 ± 0.15, -0.06 ± 0.09 and 0.07 ± 0.10 D for the control group at accommodation stimuli of 2.0, 2.5, 3.0, and 4.0 D, respectively. Contrast sensitivity was the same for both groups (P ≥ .26).

CONCLUSIONS

The Lumina accommodative IOL effectively restores the visual function, accommodation, and contrast sensitivity after cataract surgery with no influence on the postoperative contrast sensitivity.

Aberrometry in patients implanted with accommodative intraocular lenses

PURPOSE

To evaluate the objective accommodative response, change of aberrations, and depth of focus in eyes implanted with the Crystalens accommodative intraocular lens (IOL) at different accommodative demands.

DESIGN

Prospective, observational study.

METHODS

Eleven cataract patients (22 eyes) who underwent implantation of a Crystalens accommodative IOL, and control groups of 9 normal subjects (17 eyes) and 17 pseudophakic patients (17 eyes) implanted with monofocal IOLs were evaluated. A custom-developed laser ray tracing aberrometer was used to measure the optical aberrations. The monochromatic wave aberrations were described using a sixth-order Zernike polynomial expansion. Measurements were obtained under dilated and natural viewing conditions (for accommodative efforts ranging from 0 to 2.5 diopters [D]). The accommodative response was obtained by analyzing changes in paraxial defocus (associated to changes in defocus) and by evaluating the differences in the effective defocus (associated with defocus, spherical aberrations, and pupil diameter) with the accommodative demand. Depth of focus was estimated from through-focus objective optical quality.

RESULTS

Wave aberration measurements were highly reproducible. Vertical trefoil (Z3(-3)) was the predominant higher-order aberration in the Crystalens group and significantly higher (P < .0001) than in the young group, but similar to the monofocal IOL group. The coma root mean square also was higher (P < .005) in the Crystalens group than in the young group. On average, the defocus term (Z2(0)), astigmatism, or higher-order aberrations did not change systematically with accommodative demand in Crystalens eyes. As found for paraxial defocus, the effective defocus in Crystalens eyes did not show significant differences between conditions: 0.34 ± 0.48 D (far), 0.32 ± 0.50 D (intermediate), and 0.34 ± 0.44 D (near). Depth of focus was statistically significantly higher in the Crystalens eyes than in the control groups.

CONCLUSIONS

The accommodative response of eyes implanted with the Crystalens accommodative IOLs, measured objectively using laser ray tracing aberrometry, was lower than 0.4 D in all eyes. Several subjects showed changes in astigmatism, spherical aberration, trefoil, and coma with accommodation, which must arise from geometrical and alignment changes in the lens with accommodative demand. Pseudoaccommodation from increased depth of focus may contribute to near vision functionality in Crystalens-implanted patients.