- Email: [email protected]
Pilot study of new focus-shift accommodating intraocular lens
ARTICLE
Pilot study of new focus-shift accommodating intraocular lens Georgia Cleary, MBBS, MRCOphth, David J. Spalton, FRCOphth, FRCP, FRCS, John Marshall, PhD, FRCPath, FMedSci
PURPOSE: To determine the visual and accommodative performance of the OPAL-A focus-shift accommodating intraocular lens (IOL). SETTING: Department of Ophthalmology, St. Thomas’ Hospital, London, United Kingdom. METHODS: In this study comprising unilateral phacoemulsification and accommodating IOL implantation, patients were followed for 6 months. Corrected distance (CDVA) and distancecorrected near (DCNVA) visual acuities were measured. Objective amplitude of accommodation was measured with an autorefractor and subjective amplitude of accommodation, using push-up tests and defocus curves. Physiological and pilocarpine-stimulated IOL movement was measured by anterior segment optical coherence tomography. RESULTS: The mean values at 1 month, 3 months, and 6 months, respectively, were as follows: CDVA, 0.06 G 0.08 (SD), 0.08 G 0.09, and 0.05 G 0.09; DCNVA, 0.31 G 0.15, 0.31 G 0.15, and 0.34 G 0.16; objective amplitude of accommodation, 0.36 G 0.38 diopters (D), 0.12 G 0.34 D, and 0.10 G 0.34 D; subjective amplitude of accommodation, 2.79 G 0.86 D, 2.55 G 0.85 D, and 2.50 G 0.62 D with push-up test and 0.90 G 0.40 D, 0.78 G 0.23 D, and 0.93 G 0.35 D with defocus curves. The maximum physiologic IOL shift at 1 month (mean 45.2 G 63.4 mm) occurred with a 3.0 D accommodative stimulus. At 6 months, the mean pilocarpine-stimulated forward IOL shift was 306 G 161 mm. CONCLUSIONS: Objective accommodation and forward axial shift were clinically insignificant with the accommodating IOL. The near visual performance was attributed to depth of focus rather than to true pseudophakic accommodation. FINANCIAL DISCLAIMER: No author has a financial or proprietary interest in any material or method mentioned. J Cataract Refract Surg 2010; 36:762–770 Q 2010 ASCRS and ESCRS
Restoration of accommodation after phacoemulsification cataract surgery remains a significant challenge. Several successful strategies to achieve spectacle independence after cataract surgery are available; these include monovision, multifocal intraocular lenses (IOLs), and presbyopic corneal procedures. However, none is capable of restoring the dynamic optical status of the prepresbyopic eye without loss of contrast or dysphotopic symptoms. Restoration of clear vision through a continuous range of focal lengths with intact stereopsis can only be achieved by bilateral implantation of IOLs that produce an optical change in the refractive state of the eye. Ciliary muscle function has been shown to be preserved beyond the onset of presbyopia.1 Commercially available and emerging accommodating IOL 762
Q 2010 ASCRS and ESCRS Published by Elsevier Inc.
designs take advantage of this fact, using ciliary muscle action to generate forward IOL movement with near visual stimulation, which increases the effective IOL power. In the case of monofocal accommodating IOLs, this mechanism of action is known as the focus–shift principle. The theoretical amount of objective accommodation achieved by forward IOL shift depends on corneal curvature, IOL power, and axial length (AL). In a laboratory ray-tracing study,2 1.0 mm of forward IOL shift produced 1.30 diopters (D) of accommodation in an eye with an AL of 24.0 mm and a 20.00 D posterior chamber IOL. Several focus-shift accommodating IOLs have been evaluated in clinical studies.3–9 In general, focus-shift accommodating IOLs are reported to deliver less objective accommodation than subjective accommodation, and 0886-3350/10/$dsee front matter doi:10.1016/j.jcrs.2009.11.025
PILOT STUDY OF FOCUS-SHIFT ACCOMMODATING IOL
forward axial IOL shift has been correspondingly limited or even backward.4,6,7 In the present pilot study, the visual and accommodative performance of a prototype focus-shift accommodating IOL design was evaluated. This IOL differs from previous designs in that the optic–haptic junctions have a greater degree of flexibility.
PATIENTS AND METHODS This prospective single-center open-label pilot study was performed at the Department of Ophthalmology, St. Thomas’ Hospital, London, United Kingdom. It was approved by the St. Thomas’ Research Ethics Committee and adhered to the tenets of the Declaration of Helsinki. All participants gave written informed consent. Patients with age-related cataract were prospectively recruited to have unilateral cataract extraction and implantation of a prototype focus-shift accommodating IOL. Patients were required to be 18 years of age or older, willing and able to provide informed consent, and able to attend scheduled follow-up visits. Other inclusion criteria were a diagnosis of age-related cataract, potential visual acuity of 20/30 or better, and clear ocular media apart from cataract. Exclusion criteria included corneal astigmatism of 1.50 D or greater, mesopic pupil diameter smaller than 3.0 mm, and ocular disease (eg, anterior segment pathology, intraocular inflammation, glaucoma, diabetic retinopathy, age-related macular degeneration, previous intraocular surgery). Patients were also excluded if the corrected distance visual acuity (CDVA) was 6/60 or worse in the fellow eye and if they were taking systemic steroids, immunosuppressive agents, or topical or systemic medication that could interfere with accommodation. A small control group of patients having cataract surgery was also recruited for comparison. These patients met the same inclusion and exclusion criteria and had an identical surgical procedure except for implantation of a control IOL (AcrySof SA60AT, Alcon, Inc.).
Submitted: August 30, 2009. Final revision submitted: November 23, 2009. Accepted: November 24, 2009. From the Departments of Ophthalmology, St. Thomas’ Hospital (Cleary, Spalton) and The Rayne Institute (Marshall), Department of Ophthalmology, Kings College London, London, United Kingdom; Centre for Ophthalmology and Visual Science (Cleary), Perth, Western Australia. Presented at the XXVI Congress of the European Society of Cataract & Refractive Surgeons, Berlin, Germany, September 2008 and the ASCRS Symposium on Cataract, IOL and Refractive Surgery, San Francisco, California, USA, April 2009. Funded by Bausch & Lomb, Rochester, New York, New York, USA, which participated in the design and monitoring of the study. Corresponding author: David J. Spalton, Department of Ophthalmology, St. Thomas’ Hospital, Westminster Bridge Road, London SE1 7EH United Kingdom. E-mail: [email protected].
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Prototype Intraocular Lens All patients in the study group had implantation of an OPAL-A prototype accommodating IOL (HumanOptics AG). The 1-piece IOL is hydrophilic acrylic with a 5.5 mm diameter biconvex spherical optic and 4 flexible closed-loop haptics with an overall diameter of 9.8 mm (Figure 1). It is intended for implantation into the capsular bag. The IOL optic is designed to shift forward on the flexible haptics with accommodative effort. Biometry was performed by partial coherence interferometry (PCI) (IOLMaster, Carl Zeiss Meditec); the targeted postoperative refraction was plano.
Surgical Technique Surgery was performed by the same surgeon (D.J.S.) using a standardized technique. Topical anesthesia (tetracaine 1%) was administered, and a 2.75 mm clear corneal incision was made. Anesthesia was supplemented by intracameral preservative-free lignocaine 1%. The anterior chamber was filled with sodium hyaluronate 1.0% (Provisc). A 4.0 to 4.5 mm continuous curvilinear capsulorhexis was created; this was followed by hydrodissection, phacoemulsification using a stop-and-chop technique, and irrigation and aspiration to clear the capsular bag. The bag was refilled with the ophthalmic viscosurgical device (OVD) and the IOL injected into the bag with a Naviject 2.8 injector and Naviglide 2.8 cartridge (Medicel AG). The IOL was centered in the capsular bag, taking care to ensure all haptics were positioned correctly and free from folding or buckling. The OVD was aspirated from the anterior chamber and capsular bag and from behind the IOL. Intraocular lens centration and haptic configuration were rechecked, and the anterior chamber was refilled with a balanced salt solution. Cefuroxime 1 mg was injected into the anterior chamber and the corneal wound hydrated.
Postoperative Assessment All patients in the study group (ie, with accommodating IOLs) were reviewed on the first postoperative day. Subsequent follow-up was at 1, 3, and 6 months postoperatively. At each time point, patients had the following evaluations: subjective refraction, visual acuity, subjective amplitude of accommodation using defocus curves and the push-up test, objective accommodation, and IOL shift. Subjective refraction was performed with a Snellen test chart at 6 m. The maximum plus sphere and minimum minus cylinder consistent with best acuity were prescribed. Duochrome testing was performed to a red-equals-green endpoint. All visual acuity measurements were performed monocularly under daylight conditions without glare using an Optec 6500 vision-testing device (Stereo Optical Co., Inc.). The CDVA was measured with the instrument on the far setting, simulating optical infinity. Distance-corrected intermediate visual acuity (DCIVA) was measured by placing a 1.50 D spherical lens in the instrument in front of the test eye while the patient viewed the far test chart, simulating a 66.7 cm target. Distance-corrected near visual acuity (DCNVA) measurements were performed with the instrument set to the near setting, simulating a 40 cm near target. Guessing was encouraged; however, patients could only proceed to the next line if they correctly identified 3 or more letters. Visual acuity was scored to the number of letters correct and then converted to logMAR format.
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Figure 1. Prototype accommodating IOL.
To measure subjective amplitude of accommodation with defocus curves, patients viewed the same far test chart on the vision-testing device with the distance correction in place in a trial frame. Spherical trial lenses ranging in power from 2.50 to 0.50 D and C0.50 to C2.50 D were placed in the trial frame in random order, after which logMAR acuity was recorded for each trial lens. Guessing was again encouraged. Analysis of defocus curve subjective amplitude of accommodation was performed with a relative acuity level (corrected visual acuity plus 0.04 logMAR) using the method described by Gupta et al.10 Subjective amplitude of accommodation with the push-up test was measured monocularly with the distance correction in place using the Royal Air Force (RAF) rule. Patients viewed the N8 line of text on the attached test chart. If the N8 line was not clear, a C2.50 D correction was added to the test eye; this was subtracted from the final subjective amplitude of accommodation. The test chart was moved toward the patient at approximately 2 cm per second. The patient was instructed to keep the print clear for as long as possible and then indicate the point at which the print became blurred. The distance on the RAF rule was noted. The amplitude of accommodation (D) was calculated as the inverse of the near point (m) (minus C2.5 D if near correction used). The near point was measured 3 times, and the 3 measurements were averaged. Objective accommodation was measured using an autorefractor (NVision-K 5001, Shin-Nippon Commerce Inc.). A Badal lens system was fitted to the autorefractor to maintain constant target size across all viewing distances. This consisted of a C5.00 D lens and an illuminated Maltesecross target attached to the front of the autorefractor by a fixation rail. In the distance position, the target was 20 cm from the C5.00 D lens. To stimulate accommodation, the target was moved toward the patient in 1.00 D steps, which were marked along the fixation rail. Autorefraction was captured through a trial frame with the best distance correction in place and the fellow eye occluded. Measurements were taken under 4 conditions: distance and 1.00 D, 2.00 D, and 3.00 D of accommodative stimulation.
During accommodative measurements, patients were encouraged to focus on the center of the Maltese cross, making it as clear as possible. Ten autorefractions were captured under each condition; the weighted average calculated by the instrument was used. The mean spherical equivalent (SE) was recorded. Intraocular lens shift was determined by measuring the change in anterior chamber depth (ACD) to accommodative stimulation with an anterior segment optical coherence tomography (AS-OCT) system (Visante, Carl Zeiss Meditec). The subjective refraction was entered to ensure the image of the test target was located at the far point during distance measurements. Patients were positioned at the AS-OCT device and instructed to view the test target within the instrument. The image of the anterior segment was optimized by adjustments of the patient in the x, y, and z planes and was also adjusted for angle k, per the manufacturer’s instructions. Measurements were captured in the quad-scan mode of the AS-OCT device; thus, four 2-dimensional images of the anterior segment, all separated by 45 degrees, were captured under each of the 4 test conditions. To capture images in quad-scan mode, the entire anterior segment must be visible; therefore, the upper and lower eyelids were gently retracted, taking care not to distort the globe. Measurements were captured under distance conditions and then under 1.00 D, 2.00 D, and 3.00 D accommodative conditions. This was achieved by introducing defocus via the optometer integrated in the AS-OCT instrument. After image capture, the anterior chamber tool was manually applied to each image and the ACD (from the anterior corneal surface to the anterior IOL surface) noted. The 4 ACD measurements captured under each testing condition were averaged to give a single ACD value. Intraocular lens movement was then calculated by subtracting the ACD under the various accommodative conditions from the ACD under distance conditions. The control group was reviewed 6 months postoperatively and had the same measurements described above. At 6 months, patients with an accommodating IOL attended 1 additional visit to determine forward axial IOL shift stimulated by pilocarpine. This was not performed at the standard 6-month visit because of routine pupil dilation. The ACD was measured with the AS-OCT system, as described above, before and 60 minutes after administration of pilocarpine 4%.
Statistical Analysis Continuous variables were described as the mean G SD. No sample-size calculation was performed because this was a pilot study. Data were checked for normality with the D’Agostino-Pearson test. Unpaired data (6-month accommodating IOL data versus control data) were compared with 2-tailed unpaired t tests. A Bonferroni adjustment was made in view of multiple comparisons (11 parameters compared; P!.0045 considered significant). GraphPad Prism software (version 5.0b, GraphPad Software Inc.) was used.
RESULTS Twenty-two patients were recruited to the pilot study and had implantation of the prototype accommodating IOL. The control group comprised 10 patients. The mean age of the 12 men and 10 women in the accommodating IOL group was 61.5 G 11.7 years.
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Table 1. Visual acuity, amplitude of accommodation, and axial IOL movement results.
Control IOL
Accommodating IOL Parameter Visual acuity (logMAR CDVA DCIVA DCNVA Objective AoA (D) 1.0 D stimulus 2.0 D stimulus 3.0 D stimulus Subjective AoA (push-up test) (D) Subjective AoA (defocus curves) (D) Axial IOL movement (mm) 1.0 D stimulus 2.0 D stimulus 3.0 D stimulus
Difference Between Means (Accommodating Control)
1 Month
3 Months
6 Months
6 Months
Mean G SD
95% CI
0.06 G 0.08 0.18 G 0.13 0.31 G 0.15
0.08 G 0.09 0.20 G 0.12 0.31 G 0.15
0.05 G 0.09 0.24 G 0.10 0.34 G 0.16
0.08 G 0.07 0.33 G 0.12 0.40 G 0.12
0.03 G 0.03 0.09 G 0.04 0.06 G 0.06
0.03 to 0.10 0.18 to 0.01 0.18 to 0.05
.327 .033 .282
0.22 G 0.26 0.19 G 0.26 0.36 G 0.38 2.79 G 0.86 0.90 G 0.40
0.05 G 0.18 0.15 G 0.27 0.12 G 0.34 2.55 G 0.85 0.78 G 0.23
0.01 G 0.37 0.04 G 0.47 0.10 G 0.34 2.50 G 0.62 0.93 G 0.35
0.04 G 0.19 0.04 G 0.40 0.11 G 0.31 2.18 G 0.84 0.64 G 0.37
0.05 G 0.13 0.08 G 0.18 0.21 G 0.13 0.32 G 0.27 0.28 G 0.13
0.31 to 0.23 0.29 to 0.45) 0.06 to 0.48 0.22 to 0.87 0.00 to 0.56
.737 .662 .127 .235 .05
10.9 G 29.6 38.6 G 52.0 45.2 G 63.4
2.9 G 22.8 8.1 G 38.6 21.4 G 51.5
3.3 G 29.0 20.5 G 50.0 29.0 G 60.8
1.0 G 13.7 1.0 G 14.5 8.0 G 5.7
2.3 G 9.7 19.5 G 16.3 37.0 G 19.8
17.5 to 22.2 13.8 to 52.7 3.4 to 77.5
P Value*
.812 .241 .071
AoA Z amplitude of accommodation; CI Z 95% confidence interval; CDVA Z corrected distance visual acuity; DCIVA Z distance-corrected intermediate visual acuity; DCNVA Z distance-corrected near visual acuity; IOL Z intraocular lens; stimulus Z accommodative stimulus *Unpaired t test; 6 month accommodating versus control; P!.0045 considered significant after Bonferroni correction for multiple comparisons
The prototype IOL was implanted in 12 right eyes and 10 left eyes. The mean IOL power was 22.6 G 2.3 D. One patient died from unrelated health problems after the 1-month follow-up visit. All remaining patients completed 6 months of follow-up. The mean SE by subjective refraction was 0.81 G 0.52 D, 0.71 G 0.60 D, and 0.76 G 0.61 D at 1 month, 3 months, and 6 months, respectively. Table 1 and Figure 2 show the visual acuity results. Figure 3 shows the mean defocus curves. Table 1 shows the mean values of objective amplitude of
accommodation, subjective amplitude of accommodation (with push-up tests and defocus curves), and axial IOL movement. Figure 4 shows the objective amplitude of accommodation and Figure 5, axial IOL movement. The mean forward IOL movement stimulated by pilocarpine 6 months postoperatively was 306 G 161 mm. Two IOL-related complications were observed. In 1 eye, 1 proximal segment of 1 haptic was displaced anteriorly through an oversized asymmetric capsulorhexis (Figure 6, A). This was first noted at the 1-month postoperative visit and resulted in slight tilting of the IOL optic. The anterior displacement of
Figure 2. Distance-corrected logMAR visual acuity at distance, intermediate, and near (CDVA Z distance-corrected distance visual acuity; DCIVA Z distance-corrected intermediate visual acuity [66.7cm]; DCNVA Z distance-corrected near visual acuity [40 cm]).
Figure 3. Postoperative mean defocus curves for the accommodating IOL at 1, 3, and 6 months. The error bars indicate the SD.
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Figure 4. Stimulus-response curves of objective accommodation measured with the autorefractor. The error bars indicate the SD.
the haptic loop appeared slightly worse at the 3-month visit (Figure 6, B) but remained stable thereafter. The patient was asymptomatic, and no intervention was necessary. A similar clinical picture was observed in another eye. Both proximal segments of 1 haptic were displaced anteriorly through a normal-sized capsulorhexis, and the distal part of the haptic lay behind the equator of the IOL optic. In addition, 1 proximal segment of 1 further haptics was displaced anteriorly into the capsulorhexis. Again, slight IOL tilt resulted; however, the IOL remained stable thereafter and no intervention was required. DISCUSSION Achieving the goal of postoperative spectacle independence while delivering high-quality visual performance is considered to be the major challenge in cataract surgery. The ideal way to achieve this is to restore accommodation by providing a dynamic range of clear vision at all distances from far to near, facilitated by an actual change in the optical power of the eye with near visual effort.11 This would avoid the problems associated with corneal and lenticular multifocal procedures, including loss of contrast sensitivity and dysphotopic symptoms.12 It is well recognized that presbyopia does not result from loss of ciliary muscle function with age. Highresolution magnetic resonance imaging studies show changes in the configuration of the ciliary muscles with accommodative effort long after the onset of presbyopia,1 and ultrasound biomicroscopy (UBM) findings in live rhesus monkeys confirm that the architecture and accommodative movement of the ciliary muscle–zonule–capsule complex is maintained after standard phacoemulsification.13 These critical facts form the basis of lenticular strategies for the
Figure 5. Stimulus-response curves of forward IOL shift measured by AS-OCT. The error bars indicate the SD (IOL Z intraocular lens).
restoration of accommodation with focus-shift accommodating IOLs, dual-optic accommodating IOLs, and lens-refilling procedures.14,15 There are many methods of assessing the performance of accommodating IOLs. Psychophysical tests, including DCNVA and subjective amplitude of accommodation, are frequently used. Subjective amplitude of accommodation can be calculated from the push-up test or from defocus curves; both methods overestimate objective accommodation.16 This is because subjective accommodation is influenced by true accommodation and by pseudoaccommodation, which result from enhanced depth of focus due to optical factors including pupil miosis, coma and spherical aberrations, corneal multifocality, and against-the-rule astigmatism.17–19 Cortical adaptation may also play a role. The ideal way to assess accommodation is to show an objective change in optical power with near visual effort. The NVision-K 5001 autorefractor and iTrace aberrometer (Tracey Technologies, Inc.) have been used for this purpose.4,16 Both instruments have been validated in relation to subjective refraction and have an open field of view; thus, patients are able to view real visual targets in free space, allowing stimulation of accommodation as the target distance is reduced.20,21 Forward axial IOL movement can be evaluated as a surrogate measure of accommodation. The amount of IOL movement is determined as a change in ACD with accommodative stimulation, which can be a near visual stimulus or pharmacologic stimulation with topical pilocarpine to produce a supraphysiological stimulus. Although this does not represent IOL movement under everyday situations, it may serve as proof of principle behind a particular IOL design.
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Figure 6. Digital retroillumination images of an eye in which the capsulorhexis was oversized and asymmetrical. A: One month postoperatively, protrusion of the proximal segment of 1 haptic was noted. B: Three months postoperatively, further protrusion was visible. No progression was noted at subsequent visits.
Various techniques have been used to measure axial IOL movement. The most accurate is dual-beam PCI, which is closely rivaled by the newer optical lowcoherence interferometry.22–25 Other techniques include ultrasound biomicroscopy, Scheimpflug videokeratography, and oblique slit methods. In the present study, we used AS-OCT, which has been validated for ACD measurements in phakic and pseudophakic eyes.22,26,27 Overall, the present study found that the prototype accommodating IOL did not show clinically significant accommodation. Corrected distance visual acuity degraded with decreasing target distance from distance to near. Objective accommodation was clinically insignificant; the greatest mean optical change was seen 1 month postoperatively, measuring 0.36 G 0.38 D in response to a 3.00 D near stimulus. Objective amplitude of accommodation fell progressively thereafter. Subjective amplitude of accommodation, calculated from the push-up test and defocus curves, overestimated objective accommodation. The largest values for amplitude of accommodation were with the push-up test, with the mean measuring 2.79 G 0.86 D 1 month postoperatively. The N8 line on the RAF rule is relatively large, approximately equivalent to 6/24 at 25 cm. The use of this large visual stimulus likely contributed to the overestimation of amplitude of accommodation with the push-up test. Axial IOL movement was clinically insignificant and, corresponding to objective accommodation, was at its maximum (mean 45.2 G 63.4 mm in response to 3.00 D near stimulus) 1 month postoperatively. No clinically or statistically significant differences were observed between the accommodating IOL group and the control IOL at the 6month visit. However, the control group was nonrandomized and small, possibly contributing to a type II statistical error.
Several focus-shift accommodating IOLs have been evaluated clinically; however, research methodology varies.28 The 1CU IOL (HumanOptics AG) has been the subject of numerous studies and, similar to the prototype accommodating IOL we studied, is a 1-piece hydrophilic acrylic IOL with 4 flexible haptics. The prototype accommodating IOL has thinner closed loop haptics and, therefore, might be predicted to shift more effectively. Heatley et al.3 evaluated the 1CU IOL in a randomized fellow-eye comparison study in which the AcrySof MA30 IOL (Alcon, Inc.) served as a control. At the 6-month follow-up, patients with the accommodating IOL had significantly better DCNVA. By the 12-month follow-up, however, there was no difference between the 2 IOLs. These patients were reevaluated between 18 months and 24 months postoperatively.4 At that time, there was no significant difference between the 2 IOLs in the near correction required to read J1, the subjective near point, or the minus sphere defocus to read 0.3 logMAR. Objective accommodation was negligible with both IOLs (mean: 0.035 G 0.233 D, accommodating; 0.066 G 0.235 D control), similar to our results with the accommodating IOL at 6 months (mean 0.10 G 0.34 D). Subjective accommodation far overestimated the objective accommodation of both IOLs. A noncomparative study of the 1CU IOL by Wolffsohn et al.5 found different amounts of objective accommodation with 2 autorefractors. Four months postoperatively, the mean objective accommodation was 0.32 G 0.23 D with a PowerRefractor autorefractor (PlusOptiX GmbH) (again similar in magnitude to our prototype IOL results at 1 month; mean 0.36 G 0.38 D) and 0.72 G 0.38 D with an SRW-autorefractor 5000 (Shin-Nippon Commerce Inc.); however, the amplitudes decreased 2 years postoperatively. The 1CU IOL showed even higher objective amplitude of accommodation in another study using the PowerRefractor autorefractor29; the mean objective amplitude of
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accommodation was 1.19 G 0.71 D, 0.96 G 0.72 D, and 1.00 G 0.44 D at 4 weeks, 3 months, and 6 months, respectively, which is far greater than the values we observed with the prototype accommodating IOL. The accommodative movement of the 1CU IOL has also been evaluated. In a randomized study,4 IOL movement was measured by PCI between 18 months and 24 months postoperatively; the mean was 0.009 G 0.025 mm to 1.50 D near visual stimuli and 0.010 G 0.028 mm to 2.50 D near visual stimuli. These results are similar to our accommodating IOL results at 6 months. Forward movement of the 1CU IOL was significantly greater than that of the control IOL (3-piece AcrySof MA30), which moved backward with accommodative effort. The mean forward movement of the 1CU IOL after administration of pilocarpine was 0.220 G 0.169 mm, similar to the mean for the prototype IOL in our study (0.306 G 0.161 mm) at 6 months. These results are also comparable to those in a nonrandomized study by Kriechbaum et al.,30 who found that the mean forward movement of the 1CU IOL was 0.010 G 0.025 mm with near visual stimulation and 0.201 G 0.137 mm after administration of topical pilocarpine; the movement was measured with the laboratory prototype of the ACMaster PCI device between 1 year and 2 years postoperatively. The DCNVA was not significantly different from that with the 3-piece control IOLs. Another randomized fellow-eye comparison study31 found the median forward movement of the 1CU IOL was 314 mm after administration of topical pilocarpine; a monofocal 3-piece control IOL moved backward by 63 mm. The difference between the 2 IOL models was statistically significant. Overall, despite differences in haptic design, accommodative shift with the prototype IOL in our study appears comparable to that of the 1CU IOL, although we used AS-OCT rather than PCI to measure IOL movement. Other studies32–34 found that the 1CU IOL had better near visual performance than nonaccommodating control IOLs; however, these studies did not measure accommodation objectively. In a nonrandomized study, Dogru et al.35 found significantly better DCNVA in eyes with a 1CU IOL than in eyes with a 3-piece control IOL at 3, 6, and 12 months. In another randomized study,36 patients had bilateral implantation of 1CU IOLs, conventional monofocal IOLs, or multifocal IOLs. In the study, bilateral accommodating IOLs performed significantly better than bilateral monofocal IOLs in binocular uncorrected near visual acuity and binocular DCNVA, reading speed, and critical print size. Defocusing favored the accommodating IOL group over the monofocal IOL group at 3 months, but not at 18 months; significantly more patients in the accommodating IOL group than in the monofocal control group were spectacle independent.
The Crystalens AT-45 accommodating IOL (Bausch & Lomb) received U.S. Food and Drug Administration approval in November 2003 based on psychophysical assessments. This model, an early iteration of the Crystalens, is a modified plate-haptic silicone IOL. It has 2 plate haptics that are hinged adjacent to the optic. A study evaluating IOL shift with PCI7 showed that the Crystalens AT-45 IOL moved backward (mean 151 G 84 mm) after pilocarpine stimulation 3 months postoperatively, thus differing from the clinical behavior of the prototype accommodating IOL in our study. Using UBM, Marchini et al.37 assessed axial movement of the Crystalens AT-45 IOL using a different protocol and found a net forward IOL shift between relaxed accommodation (after topical cyclopentolate) and active accommodation (viewing a near stimulus at 40 cm). Marchini et al. found a mean change in ACD of 0.24 G 0.17 mm 1 month postoperatively and 0.17G 0.27 mm at 12 months. However, their study had several limitations. First, UBM is prone to misalignment off-axis and convergence effects from fellow-eye stimulation. Furthermore, the protocol measured the change in ACD from near visual stimulation to pharmacologic relaxation of the ciliary muscle with cyclopentolate, potentially exaggerating the results of IOL movement. Thus, the results of Marchini et al. cannot be compared with our results with the prototype accommodating IOL. There are fewer studies of the Tetraflex KH-3500 accommodating IOL (Lenstec, Inc.). This is a microincision 1-piece hydrophilic acrylic IOL with 2 haptics that, similar to those of the prototype IOL in our study, are thin and flexible with a closed-loop design. As with other accommodating IOLs, the subjective amplitude of accommodation was greater than the objective amplitude of accommodation (mean 3.10 G 1.60 D versus 0.39 G 0.53 D) between 2 weeks and 3 weeks postoperatively, although both measurements were significantly higher than with the control IOL (Softec 1, Lenstec, Inc.).6 These results were similar to those of the accommodating IOL in our study, which had a mean objective amplitude of accommodation 0.36 G 0.38 D at 1 month. In conclusion, the OPAL-A IOL, like other focus-shift accommodating IOLs, failed to show clinically meaningful IOL shift and objective accommodation with physiologic near visual stimulation. This IOL suffers from a flaw inherent to all focus-shift IOLs; that is, a large forward shift is required to achieve a clinically significant myopic refractive change. If achieved, large optic translations can result in iris chafing and pigment dispersion, compromising the safety of these IOLs. Thus, alternative lenticular strategies for restoring accommodation are necessary.
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REFERENCES 1. Strenk SA, Strenk LM, Guo S. Magnetic resonance imaging of aging, accommodating, phakic, and pseudophakic ciliary muscle diameters. J Cataract Refract Surg 2006; 32:1792–1798 2. Nawa Y, Ueda T, Nakatsuka M, Tsuji H, Marutani H, Hara Y, Uozato H. Accommodation obtained per 1.0 mm forward movement of a posterior chamber intraocular lens. J Cataract Refract Surg 2003; 29:2069–2072 3. Heatley CJ, Spalton DJ, Hancox J, Kumar A, Marshall J. Fellow eye comparison between the 1CU accommodative intraocular lens and the Acrysof MA30 monofocal intraocular lens. Am J Ophthalmol 2005; 140:207–213 4. Hancox J, Spalton D, Heatley C, Jayaram H, Marshall J. Objective measurement of intraocular lens movement and dioptric change with a focus shift accommodating intraocular lens. J Cataract Refract Surg 2006; 32:1098–1103 5. Wolffsohn JS, Hunt OA, Naroo S, Gilmartin B, Shah S, Cunliffe IA, Benson MT, Mantry S. Objective accommodative amplitude and dynamics with the 1CU accommodative intraocular lens. Invest Ophthalmol Vis Sci 2006; 47:1230–1235. Available at: http://www.iovs.org/cgi/reprint/47/3/1230. Accessed January 14, 2010 6. Wolffsohn JS, Naroo SA, Motwani NK, Shah S, Hunt OA, Mantry S, Sira M, Cunliffe IA, Benson MT. Subjective and objective performance of the Lenstec KH-3500 "accommodative" intraocular lens. Br J Ophthalmol 2006; 90:693–696. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1860198/pdf/ 693.pdf. Accessed January 14, 2010 7. Koeppl C, Findl O, Menapace R, Kriechbaum K, Wirtitsch M, Buehl W, Sacu S, Drexler W. Pilocarpine-induced shift of an accommodating intraocular lens: AT-45 Crystalens. J Cataract Refract Surg 2005; 31:1290–1297 8. Cumming JS, Colvard DM, Dell SJ, Doane J, Fine IH, Hoffman RS, Packer M, Slade SG. Clinical evaluation of the Crystalens AT-45 accommodating intraocular lens; results of the U.S. Food and Drug Administration clinical trial. J Cataract Refract Surg 2006; 32:812–825 9. Legeais JM, Werner L, Werner L, Abenhaim A, Renard G. Pseudoaccommodation: BioComFold versus a foldable silicone intraocular lens. J Cataract Refract Surg 1999; 25:262–267 10. Gupta N, Wolffsohn JSW, Naroo SA. Optimizing measurement of subjective amplitude of accommodation with defocus curves. J Cataract Refract Surg 2008; 34:1329–1338 11. Glasser A. Restoration of accommodation: surgical options for correction of presbyopia. Clin Exp Optom 2008; 91: 279–295 12. Martı´nez Palmer A, Go´mez Fain˜a P, Espan˜a Albelda A, Comas Serrano M, Saad DN, Castilla Ce´spedes M. Visual function with bilateral implantation of monofocal and multifocal intraocular lenses: a prospective, randomized, controlled clinical trial. J Refract Surg 2008; 24:257–264 13. Wasilewski R, McDonald JP, Heatley GA, Lu¨tjen-Drecoll E, Kaufman PL, Croft MA. Surgical intervention and accommodative responses, II: forward ciliary body accommodative movement is facilitated by zonular attachments to the lens capsule. Invest Ophthalmol Vis Sci 2008; 49:5495–5502. Available at: http://www.iovs.org/cgi/reprint/49/12/5495. Accessed January 14, 2010 14. McLeod SD, Vargas LG, Portney V, Ting A. Synchrony dualoptic accommodating intraocular lens. Part 1: optical and biomechanical principles and design considerations. J Cataract Refract Surg 2007; 33:37–46 15. Nishi O, Nishi K, Nishi Y, Chang S. Capsular bag refilling using a new accommodating intraocular lens. J Cataract Refract Surg 2008; 34:302–309
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16. Win-Hall DM, Glasser A. Objective accommodation measurements in pseudophakic subjects using an autorefractor and an aberrometer. J Cataract Refract Surg 2009; 35:282–290 17. Nakazawa M, Ohtsuki K. Apparent accommodation in pseudophakic eyes after implantation of posterior chamber intraocular lenses: optical analysis. Invest Ophthalmol Vis Sci 1984; 25:1458–1460. Available at: http://www.iovs.org/cgi/reprint/25/ 12/1458.pdf. Accessed January 14, 2010 18. Oshika T, Mimura T, Tanaka S, Amano S, Fukuyama M, Yoshitomi F, Maeda N, Fujikado T, Hirohara Y, Mihashi T. Apparent accommodation and corneal wavefront aberration in pseudophakic eyes. Invest Ophthalmol Vis Sci 2002; 43:2882– 2886. Available at: http://www.iovs.org/cgi/reprint/43/9/2882. Accessed January 14, 2010 19. Trindade F, Oliveira A, Frasson M. Benefit of against-the-rule astigmatism to uncorrected near acuity. J Cataract Refract Surg 1997; 23:82–85 20. Davies LN, Mallen EAH, Wolffsohn JS, Gilmartin B. Clinical evaluation of the Shin-Nippon NVision-K 5001/Grand Seiko WR5100K autorefractor. Optom Vis Sci 2003; 80:320–324 21. Cleary G, Spalton DJ, Patel PM, Lin P-F, Marshall J. Diagnostic accuracy and variability of autorefraction by the Tracey Visual Function Analyzer and the Shin-Nippon NVision-K 5001 in relation to subjective refraction. Ophthalmic Physiol Opt 2009; 29:173–181 22. Cleary G, Spalton DJ, Marshall J. Anterior chamber depth measurements in eyes implanted with an accommodating intraocular lens: agreement between the AC Master and the Visante OCT In press. J Cataract Refract Surg 23. Buckhurst PJ, Wolffsohn JS, Shah S, Naroo SA, Davies LN, Berrow EJ. A new optical low coherence reflectometry device for ocular biometry in cataract patients. Br J Ophthalmol 2009; 93:949–953 24. Kriechbaum K, Leydolt C, Findl O, Bolz M, Drexler W. Comparison of partial coherence interferometers: ACMaster versus laboratory prototype. J Refract Surg 2006; 22:811–816 25. Cruysberg LPJ, Doors M, Verbakel F, Berendschot TTJM, De Brabander J, Nuijts RMMA. Evaluation of the Lenstar LS 900 non-contact biometer. Br J Ophthalmol 2010; 94:106–110 26. Nemeth G, Vajas A, Tsorbatzoglou A, Kolozsvari B, Modis L Jr, Berta A. Assessment and reproducibility of anterior chamber depth measurement with anterior segment optical coherence tomography compared with immersion ultrasonography. J Cataract Refract Surg 2007; 33:443–447 27. Baikoff G, Jodai HJ, Bourgeon G. Measurement of the internal diameter and depth of the anterior chamber: IOLMaster versus anterior chamber optical coherence tomographer. J Cataract Refract Surg 2005; 31:1722–1728 28. Findl O, Leydolt C. Meta-analysis of accommodating intraocular lenses. J Cataract Refract Surg 2007; 33:522–527 29. Langenbucher A, Huber S, Nguyen NX, Seitz B, GusekSchneider GC, Ku¨chle M. Measurement of accommodation after implantation of an accommodating posterior chamber intraocular lens. J Cataract Refract Surg 2003; 29:677–685 30. Kriechbaum K, Findl O, Koeppl C, Menapace R, Drexler W. Stimulus-driven versus pilocarpine-induced biometric changes in pseudophakic eyes. Ophthalmology 2005; 112:453–459 31. Findl O, Kriechbaum K, Menapace R, Koeppl C, Sacu S, Wirtitsch M, Buehl W, Drexler W. Laserinterferometric assessment of pilocarpine-induced movement of an accommodating intraocular lens; a randomized trial. Ophthalmology 2004; 111:1515–1521 32. Mastropasqua L, Toto L, Nubile M, Falconio G, Ballone E. Clinical study of the 1CU accommodating intraocular lens. J Cataract Refract Surg 2003; 29:1307–1312 33. Ku¨chle M, Seitz B, Langenbucher A, Gusek-Schneider GC, Martus P, Nguyen NX. Comparison of 6-month results of
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implantation of the 1CU accommodative intraocular lens with conventional intraocular lenses; the Erlangen Accommodative Intraocular Lens Study Group. Ophthalmology 2004; 111:318–324 34. Marchini G, Mora P, Pedrotti E, Manzotti F, Aldigeri R, Gandolfi SA. Functional assessment of two different accommodative intraocular lenses compared with a monofocal intraocular lens. Ophthalmology 2007; 114:2038–2043 35. Dogru M, Honda R, Omoto M, Toda I, Fujishima H, Arai H, Matsuyama M, Nishijima S, Hida Y, Yagi Y, Tsubota K. Early visual results with the 1CU accommodating intraocular lens. J Cataract Refract Surg 2005; 31:895–902 36. Harman FE, Maling S, Kampougeris G, Langan L, Khan I, Lee N, Bloom PA. Comparing the 1CU accommodative, multifocal, and monofocal intraocular lenses; a randomized trial. Ophthalmology 2008; 115:993–1001
37. Marchini G, Pedrotti E, Sartori P, Tosi R. Ultrasound biomicroscopic changes during accommodation in eyes with accommodating intraocular lenses; pilot study and hypothesis for the mechanism of accommodation. J Cataract Refract Surg 2004; 30:2476–2482
J CATARACT REFRACT SURG - VOL 36, MAY 2010
First Author: Georgia Cleary, MBBS, MRCOphth Department of Ophthalmology, St. Thomas’ Hospital, London, United Kingdom
Pilot study of new focus-shift accommodating intraocular lens Georgia Cleary, MBBS, MRCOphth, David J. Spalton, FRCOphth, FRCP, FRCS, John Marshall, PhD, FRCPath, FMedSci
PURPOSE: To determine the visual and accommodative performance of the OPAL-A focus-shift accommodating intraocular lens (IOL). SETTING: Department of Ophthalmology, St. Thomas’ Hospital, London, United Kingdom. METHODS: In this study comprising unilateral phacoemulsification and accommodating IOL implantation, patients were followed for 6 months. Corrected distance (CDVA) and distancecorrected near (DCNVA) visual acuities were measured. Objective amplitude of accommodation was measured with an autorefractor and subjective amplitude of accommodation, using push-up tests and defocus curves. Physiological and pilocarpine-stimulated IOL movement was measured by anterior segment optical coherence tomography. RESULTS: The mean values at 1 month, 3 months, and 6 months, respectively, were as follows: CDVA, 0.06 G 0.08 (SD), 0.08 G 0.09, and 0.05 G 0.09; DCNVA, 0.31 G 0.15, 0.31 G 0.15, and 0.34 G 0.16; objective amplitude of accommodation, 0.36 G 0.38 diopters (D), 0.12 G 0.34 D, and 0.10 G 0.34 D; subjective amplitude of accommodation, 2.79 G 0.86 D, 2.55 G 0.85 D, and 2.50 G 0.62 D with push-up test and 0.90 G 0.40 D, 0.78 G 0.23 D, and 0.93 G 0.35 D with defocus curves. The maximum physiologic IOL shift at 1 month (mean 45.2 G 63.4 mm) occurred with a 3.0 D accommodative stimulus. At 6 months, the mean pilocarpine-stimulated forward IOL shift was 306 G 161 mm. CONCLUSIONS: Objective accommodation and forward axial shift were clinically insignificant with the accommodating IOL. The near visual performance was attributed to depth of focus rather than to true pseudophakic accommodation. FINANCIAL DISCLAIMER: No author has a financial or proprietary interest in any material or method mentioned. J Cataract Refract Surg 2010; 36:762–770 Q 2010 ASCRS and ESCRS
Restoration of accommodation after phacoemulsification cataract surgery remains a significant challenge. Several successful strategies to achieve spectacle independence after cataract surgery are available; these include monovision, multifocal intraocular lenses (IOLs), and presbyopic corneal procedures. However, none is capable of restoring the dynamic optical status of the prepresbyopic eye without loss of contrast or dysphotopic symptoms. Restoration of clear vision through a continuous range of focal lengths with intact stereopsis can only be achieved by bilateral implantation of IOLs that produce an optical change in the refractive state of the eye. Ciliary muscle function has been shown to be preserved beyond the onset of presbyopia.1 Commercially available and emerging accommodating IOL 762
Q 2010 ASCRS and ESCRS Published by Elsevier Inc.
designs take advantage of this fact, using ciliary muscle action to generate forward IOL movement with near visual stimulation, which increases the effective IOL power. In the case of monofocal accommodating IOLs, this mechanism of action is known as the focus–shift principle. The theoretical amount of objective accommodation achieved by forward IOL shift depends on corneal curvature, IOL power, and axial length (AL). In a laboratory ray-tracing study,2 1.0 mm of forward IOL shift produced 1.30 diopters (D) of accommodation in an eye with an AL of 24.0 mm and a 20.00 D posterior chamber IOL. Several focus-shift accommodating IOLs have been evaluated in clinical studies.3–9 In general, focus-shift accommodating IOLs are reported to deliver less objective accommodation than subjective accommodation, and 0886-3350/10/$dsee front matter doi:10.1016/j.jcrs.2009.11.025
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forward axial IOL shift has been correspondingly limited or even backward.4,6,7 In the present pilot study, the visual and accommodative performance of a prototype focus-shift accommodating IOL design was evaluated. This IOL differs from previous designs in that the optic–haptic junctions have a greater degree of flexibility.
PATIENTS AND METHODS This prospective single-center open-label pilot study was performed at the Department of Ophthalmology, St. Thomas’ Hospital, London, United Kingdom. It was approved by the St. Thomas’ Research Ethics Committee and adhered to the tenets of the Declaration of Helsinki. All participants gave written informed consent. Patients with age-related cataract were prospectively recruited to have unilateral cataract extraction and implantation of a prototype focus-shift accommodating IOL. Patients were required to be 18 years of age or older, willing and able to provide informed consent, and able to attend scheduled follow-up visits. Other inclusion criteria were a diagnosis of age-related cataract, potential visual acuity of 20/30 or better, and clear ocular media apart from cataract. Exclusion criteria included corneal astigmatism of 1.50 D or greater, mesopic pupil diameter smaller than 3.0 mm, and ocular disease (eg, anterior segment pathology, intraocular inflammation, glaucoma, diabetic retinopathy, age-related macular degeneration, previous intraocular surgery). Patients were also excluded if the corrected distance visual acuity (CDVA) was 6/60 or worse in the fellow eye and if they were taking systemic steroids, immunosuppressive agents, or topical or systemic medication that could interfere with accommodation. A small control group of patients having cataract surgery was also recruited for comparison. These patients met the same inclusion and exclusion criteria and had an identical surgical procedure except for implantation of a control IOL (AcrySof SA60AT, Alcon, Inc.).
Submitted: August 30, 2009. Final revision submitted: November 23, 2009. Accepted: November 24, 2009. From the Departments of Ophthalmology, St. Thomas’ Hospital (Cleary, Spalton) and The Rayne Institute (Marshall), Department of Ophthalmology, Kings College London, London, United Kingdom; Centre for Ophthalmology and Visual Science (Cleary), Perth, Western Australia. Presented at the XXVI Congress of the European Society of Cataract & Refractive Surgeons, Berlin, Germany, September 2008 and the ASCRS Symposium on Cataract, IOL and Refractive Surgery, San Francisco, California, USA, April 2009. Funded by Bausch & Lomb, Rochester, New York, New York, USA, which participated in the design and monitoring of the study. Corresponding author: David J. Spalton, Department of Ophthalmology, St. Thomas’ Hospital, Westminster Bridge Road, London SE1 7EH United Kingdom. E-mail: [email protected].
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Prototype Intraocular Lens All patients in the study group had implantation of an OPAL-A prototype accommodating IOL (HumanOptics AG). The 1-piece IOL is hydrophilic acrylic with a 5.5 mm diameter biconvex spherical optic and 4 flexible closed-loop haptics with an overall diameter of 9.8 mm (Figure 1). It is intended for implantation into the capsular bag. The IOL optic is designed to shift forward on the flexible haptics with accommodative effort. Biometry was performed by partial coherence interferometry (PCI) (IOLMaster, Carl Zeiss Meditec); the targeted postoperative refraction was plano.
Surgical Technique Surgery was performed by the same surgeon (D.J.S.) using a standardized technique. Topical anesthesia (tetracaine 1%) was administered, and a 2.75 mm clear corneal incision was made. Anesthesia was supplemented by intracameral preservative-free lignocaine 1%. The anterior chamber was filled with sodium hyaluronate 1.0% (Provisc). A 4.0 to 4.5 mm continuous curvilinear capsulorhexis was created; this was followed by hydrodissection, phacoemulsification using a stop-and-chop technique, and irrigation and aspiration to clear the capsular bag. The bag was refilled with the ophthalmic viscosurgical device (OVD) and the IOL injected into the bag with a Naviject 2.8 injector and Naviglide 2.8 cartridge (Medicel AG). The IOL was centered in the capsular bag, taking care to ensure all haptics were positioned correctly and free from folding or buckling. The OVD was aspirated from the anterior chamber and capsular bag and from behind the IOL. Intraocular lens centration and haptic configuration were rechecked, and the anterior chamber was refilled with a balanced salt solution. Cefuroxime 1 mg was injected into the anterior chamber and the corneal wound hydrated.
Postoperative Assessment All patients in the study group (ie, with accommodating IOLs) were reviewed on the first postoperative day. Subsequent follow-up was at 1, 3, and 6 months postoperatively. At each time point, patients had the following evaluations: subjective refraction, visual acuity, subjective amplitude of accommodation using defocus curves and the push-up test, objective accommodation, and IOL shift. Subjective refraction was performed with a Snellen test chart at 6 m. The maximum plus sphere and minimum minus cylinder consistent with best acuity were prescribed. Duochrome testing was performed to a red-equals-green endpoint. All visual acuity measurements were performed monocularly under daylight conditions without glare using an Optec 6500 vision-testing device (Stereo Optical Co., Inc.). The CDVA was measured with the instrument on the far setting, simulating optical infinity. Distance-corrected intermediate visual acuity (DCIVA) was measured by placing a 1.50 D spherical lens in the instrument in front of the test eye while the patient viewed the far test chart, simulating a 66.7 cm target. Distance-corrected near visual acuity (DCNVA) measurements were performed with the instrument set to the near setting, simulating a 40 cm near target. Guessing was encouraged; however, patients could only proceed to the next line if they correctly identified 3 or more letters. Visual acuity was scored to the number of letters correct and then converted to logMAR format.
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Figure 1. Prototype accommodating IOL.
To measure subjective amplitude of accommodation with defocus curves, patients viewed the same far test chart on the vision-testing device with the distance correction in place in a trial frame. Spherical trial lenses ranging in power from 2.50 to 0.50 D and C0.50 to C2.50 D were placed in the trial frame in random order, after which logMAR acuity was recorded for each trial lens. Guessing was again encouraged. Analysis of defocus curve subjective amplitude of accommodation was performed with a relative acuity level (corrected visual acuity plus 0.04 logMAR) using the method described by Gupta et al.10 Subjective amplitude of accommodation with the push-up test was measured monocularly with the distance correction in place using the Royal Air Force (RAF) rule. Patients viewed the N8 line of text on the attached test chart. If the N8 line was not clear, a C2.50 D correction was added to the test eye; this was subtracted from the final subjective amplitude of accommodation. The test chart was moved toward the patient at approximately 2 cm per second. The patient was instructed to keep the print clear for as long as possible and then indicate the point at which the print became blurred. The distance on the RAF rule was noted. The amplitude of accommodation (D) was calculated as the inverse of the near point (m) (minus C2.5 D if near correction used). The near point was measured 3 times, and the 3 measurements were averaged. Objective accommodation was measured using an autorefractor (NVision-K 5001, Shin-Nippon Commerce Inc.). A Badal lens system was fitted to the autorefractor to maintain constant target size across all viewing distances. This consisted of a C5.00 D lens and an illuminated Maltesecross target attached to the front of the autorefractor by a fixation rail. In the distance position, the target was 20 cm from the C5.00 D lens. To stimulate accommodation, the target was moved toward the patient in 1.00 D steps, which were marked along the fixation rail. Autorefraction was captured through a trial frame with the best distance correction in place and the fellow eye occluded. Measurements were taken under 4 conditions: distance and 1.00 D, 2.00 D, and 3.00 D of accommodative stimulation.
During accommodative measurements, patients were encouraged to focus on the center of the Maltese cross, making it as clear as possible. Ten autorefractions were captured under each condition; the weighted average calculated by the instrument was used. The mean spherical equivalent (SE) was recorded. Intraocular lens shift was determined by measuring the change in anterior chamber depth (ACD) to accommodative stimulation with an anterior segment optical coherence tomography (AS-OCT) system (Visante, Carl Zeiss Meditec). The subjective refraction was entered to ensure the image of the test target was located at the far point during distance measurements. Patients were positioned at the AS-OCT device and instructed to view the test target within the instrument. The image of the anterior segment was optimized by adjustments of the patient in the x, y, and z planes and was also adjusted for angle k, per the manufacturer’s instructions. Measurements were captured in the quad-scan mode of the AS-OCT device; thus, four 2-dimensional images of the anterior segment, all separated by 45 degrees, were captured under each of the 4 test conditions. To capture images in quad-scan mode, the entire anterior segment must be visible; therefore, the upper and lower eyelids were gently retracted, taking care not to distort the globe. Measurements were captured under distance conditions and then under 1.00 D, 2.00 D, and 3.00 D accommodative conditions. This was achieved by introducing defocus via the optometer integrated in the AS-OCT instrument. After image capture, the anterior chamber tool was manually applied to each image and the ACD (from the anterior corneal surface to the anterior IOL surface) noted. The 4 ACD measurements captured under each testing condition were averaged to give a single ACD value. Intraocular lens movement was then calculated by subtracting the ACD under the various accommodative conditions from the ACD under distance conditions. The control group was reviewed 6 months postoperatively and had the same measurements described above. At 6 months, patients with an accommodating IOL attended 1 additional visit to determine forward axial IOL shift stimulated by pilocarpine. This was not performed at the standard 6-month visit because of routine pupil dilation. The ACD was measured with the AS-OCT system, as described above, before and 60 minutes after administration of pilocarpine 4%.
Statistical Analysis Continuous variables were described as the mean G SD. No sample-size calculation was performed because this was a pilot study. Data were checked for normality with the D’Agostino-Pearson test. Unpaired data (6-month accommodating IOL data versus control data) were compared with 2-tailed unpaired t tests. A Bonferroni adjustment was made in view of multiple comparisons (11 parameters compared; P!.0045 considered significant). GraphPad Prism software (version 5.0b, GraphPad Software Inc.) was used.
RESULTS Twenty-two patients were recruited to the pilot study and had implantation of the prototype accommodating IOL. The control group comprised 10 patients. The mean age of the 12 men and 10 women in the accommodating IOL group was 61.5 G 11.7 years.
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Table 1. Visual acuity, amplitude of accommodation, and axial IOL movement results.
Control IOL
Accommodating IOL Parameter Visual acuity (logMAR CDVA DCIVA DCNVA Objective AoA (D) 1.0 D stimulus 2.0 D stimulus 3.0 D stimulus Subjective AoA (push-up test) (D) Subjective AoA (defocus curves) (D) Axial IOL movement (mm) 1.0 D stimulus 2.0 D stimulus 3.0 D stimulus
Difference Between Means (Accommodating Control)
1 Month
3 Months
6 Months
6 Months
Mean G SD
95% CI
0.06 G 0.08 0.18 G 0.13 0.31 G 0.15
0.08 G 0.09 0.20 G 0.12 0.31 G 0.15
0.05 G 0.09 0.24 G 0.10 0.34 G 0.16
0.08 G 0.07 0.33 G 0.12 0.40 G 0.12
0.03 G 0.03 0.09 G 0.04 0.06 G 0.06
0.03 to 0.10 0.18 to 0.01 0.18 to 0.05
.327 .033 .282
0.22 G 0.26 0.19 G 0.26 0.36 G 0.38 2.79 G 0.86 0.90 G 0.40
0.05 G 0.18 0.15 G 0.27 0.12 G 0.34 2.55 G 0.85 0.78 G 0.23
0.01 G 0.37 0.04 G 0.47 0.10 G 0.34 2.50 G 0.62 0.93 G 0.35
0.04 G 0.19 0.04 G 0.40 0.11 G 0.31 2.18 G 0.84 0.64 G 0.37
0.05 G 0.13 0.08 G 0.18 0.21 G 0.13 0.32 G 0.27 0.28 G 0.13
0.31 to 0.23 0.29 to 0.45) 0.06 to 0.48 0.22 to 0.87 0.00 to 0.56
.737 .662 .127 .235 .05
10.9 G 29.6 38.6 G 52.0 45.2 G 63.4
2.9 G 22.8 8.1 G 38.6 21.4 G 51.5
3.3 G 29.0 20.5 G 50.0 29.0 G 60.8
1.0 G 13.7 1.0 G 14.5 8.0 G 5.7
2.3 G 9.7 19.5 G 16.3 37.0 G 19.8
17.5 to 22.2 13.8 to 52.7 3.4 to 77.5
P Value*
.812 .241 .071
AoA Z amplitude of accommodation; CI Z 95% confidence interval; CDVA Z corrected distance visual acuity; DCIVA Z distance-corrected intermediate visual acuity; DCNVA Z distance-corrected near visual acuity; IOL Z intraocular lens; stimulus Z accommodative stimulus *Unpaired t test; 6 month accommodating versus control; P!.0045 considered significant after Bonferroni correction for multiple comparisons
The prototype IOL was implanted in 12 right eyes and 10 left eyes. The mean IOL power was 22.6 G 2.3 D. One patient died from unrelated health problems after the 1-month follow-up visit. All remaining patients completed 6 months of follow-up. The mean SE by subjective refraction was 0.81 G 0.52 D, 0.71 G 0.60 D, and 0.76 G 0.61 D at 1 month, 3 months, and 6 months, respectively. Table 1 and Figure 2 show the visual acuity results. Figure 3 shows the mean defocus curves. Table 1 shows the mean values of objective amplitude of
accommodation, subjective amplitude of accommodation (with push-up tests and defocus curves), and axial IOL movement. Figure 4 shows the objective amplitude of accommodation and Figure 5, axial IOL movement. The mean forward IOL movement stimulated by pilocarpine 6 months postoperatively was 306 G 161 mm. Two IOL-related complications were observed. In 1 eye, 1 proximal segment of 1 haptic was displaced anteriorly through an oversized asymmetric capsulorhexis (Figure 6, A). This was first noted at the 1-month postoperative visit and resulted in slight tilting of the IOL optic. The anterior displacement of
Figure 2. Distance-corrected logMAR visual acuity at distance, intermediate, and near (CDVA Z distance-corrected distance visual acuity; DCIVA Z distance-corrected intermediate visual acuity [66.7cm]; DCNVA Z distance-corrected near visual acuity [40 cm]).
Figure 3. Postoperative mean defocus curves for the accommodating IOL at 1, 3, and 6 months. The error bars indicate the SD.
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Figure 4. Stimulus-response curves of objective accommodation measured with the autorefractor. The error bars indicate the SD.
the haptic loop appeared slightly worse at the 3-month visit (Figure 6, B) but remained stable thereafter. The patient was asymptomatic, and no intervention was necessary. A similar clinical picture was observed in another eye. Both proximal segments of 1 haptic were displaced anteriorly through a normal-sized capsulorhexis, and the distal part of the haptic lay behind the equator of the IOL optic. In addition, 1 proximal segment of 1 further haptics was displaced anteriorly into the capsulorhexis. Again, slight IOL tilt resulted; however, the IOL remained stable thereafter and no intervention was required. DISCUSSION Achieving the goal of postoperative spectacle independence while delivering high-quality visual performance is considered to be the major challenge in cataract surgery. The ideal way to achieve this is to restore accommodation by providing a dynamic range of clear vision at all distances from far to near, facilitated by an actual change in the optical power of the eye with near visual effort.11 This would avoid the problems associated with corneal and lenticular multifocal procedures, including loss of contrast sensitivity and dysphotopic symptoms.12 It is well recognized that presbyopia does not result from loss of ciliary muscle function with age. Highresolution magnetic resonance imaging studies show changes in the configuration of the ciliary muscles with accommodative effort long after the onset of presbyopia,1 and ultrasound biomicroscopy (UBM) findings in live rhesus monkeys confirm that the architecture and accommodative movement of the ciliary muscle–zonule–capsule complex is maintained after standard phacoemulsification.13 These critical facts form the basis of lenticular strategies for the
Figure 5. Stimulus-response curves of forward IOL shift measured by AS-OCT. The error bars indicate the SD (IOL Z intraocular lens).
restoration of accommodation with focus-shift accommodating IOLs, dual-optic accommodating IOLs, and lens-refilling procedures.14,15 There are many methods of assessing the performance of accommodating IOLs. Psychophysical tests, including DCNVA and subjective amplitude of accommodation, are frequently used. Subjective amplitude of accommodation can be calculated from the push-up test or from defocus curves; both methods overestimate objective accommodation.16 This is because subjective accommodation is influenced by true accommodation and by pseudoaccommodation, which result from enhanced depth of focus due to optical factors including pupil miosis, coma and spherical aberrations, corneal multifocality, and against-the-rule astigmatism.17–19 Cortical adaptation may also play a role. The ideal way to assess accommodation is to show an objective change in optical power with near visual effort. The NVision-K 5001 autorefractor and iTrace aberrometer (Tracey Technologies, Inc.) have been used for this purpose.4,16 Both instruments have been validated in relation to subjective refraction and have an open field of view; thus, patients are able to view real visual targets in free space, allowing stimulation of accommodation as the target distance is reduced.20,21 Forward axial IOL movement can be evaluated as a surrogate measure of accommodation. The amount of IOL movement is determined as a change in ACD with accommodative stimulation, which can be a near visual stimulus or pharmacologic stimulation with topical pilocarpine to produce a supraphysiological stimulus. Although this does not represent IOL movement under everyday situations, it may serve as proof of principle behind a particular IOL design.
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Figure 6. Digital retroillumination images of an eye in which the capsulorhexis was oversized and asymmetrical. A: One month postoperatively, protrusion of the proximal segment of 1 haptic was noted. B: Three months postoperatively, further protrusion was visible. No progression was noted at subsequent visits.
Various techniques have been used to measure axial IOL movement. The most accurate is dual-beam PCI, which is closely rivaled by the newer optical lowcoherence interferometry.22–25 Other techniques include ultrasound biomicroscopy, Scheimpflug videokeratography, and oblique slit methods. In the present study, we used AS-OCT, which has been validated for ACD measurements in phakic and pseudophakic eyes.22,26,27 Overall, the present study found that the prototype accommodating IOL did not show clinically significant accommodation. Corrected distance visual acuity degraded with decreasing target distance from distance to near. Objective accommodation was clinically insignificant; the greatest mean optical change was seen 1 month postoperatively, measuring 0.36 G 0.38 D in response to a 3.00 D near stimulus. Objective amplitude of accommodation fell progressively thereafter. Subjective amplitude of accommodation, calculated from the push-up test and defocus curves, overestimated objective accommodation. The largest values for amplitude of accommodation were with the push-up test, with the mean measuring 2.79 G 0.86 D 1 month postoperatively. The N8 line on the RAF rule is relatively large, approximately equivalent to 6/24 at 25 cm. The use of this large visual stimulus likely contributed to the overestimation of amplitude of accommodation with the push-up test. Axial IOL movement was clinically insignificant and, corresponding to objective accommodation, was at its maximum (mean 45.2 G 63.4 mm in response to 3.00 D near stimulus) 1 month postoperatively. No clinically or statistically significant differences were observed between the accommodating IOL group and the control IOL at the 6month visit. However, the control group was nonrandomized and small, possibly contributing to a type II statistical error.
Several focus-shift accommodating IOLs have been evaluated clinically; however, research methodology varies.28 The 1CU IOL (HumanOptics AG) has been the subject of numerous studies and, similar to the prototype accommodating IOL we studied, is a 1-piece hydrophilic acrylic IOL with 4 flexible haptics. The prototype accommodating IOL has thinner closed loop haptics and, therefore, might be predicted to shift more effectively. Heatley et al.3 evaluated the 1CU IOL in a randomized fellow-eye comparison study in which the AcrySof MA30 IOL (Alcon, Inc.) served as a control. At the 6-month follow-up, patients with the accommodating IOL had significantly better DCNVA. By the 12-month follow-up, however, there was no difference between the 2 IOLs. These patients were reevaluated between 18 months and 24 months postoperatively.4 At that time, there was no significant difference between the 2 IOLs in the near correction required to read J1, the subjective near point, or the minus sphere defocus to read 0.3 logMAR. Objective accommodation was negligible with both IOLs (mean: 0.035 G 0.233 D, accommodating; 0.066 G 0.235 D control), similar to our results with the accommodating IOL at 6 months (mean 0.10 G 0.34 D). Subjective accommodation far overestimated the objective accommodation of both IOLs. A noncomparative study of the 1CU IOL by Wolffsohn et al.5 found different amounts of objective accommodation with 2 autorefractors. Four months postoperatively, the mean objective accommodation was 0.32 G 0.23 D with a PowerRefractor autorefractor (PlusOptiX GmbH) (again similar in magnitude to our prototype IOL results at 1 month; mean 0.36 G 0.38 D) and 0.72 G 0.38 D with an SRW-autorefractor 5000 (Shin-Nippon Commerce Inc.); however, the amplitudes decreased 2 years postoperatively. The 1CU IOL showed even higher objective amplitude of accommodation in another study using the PowerRefractor autorefractor29; the mean objective amplitude of
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accommodation was 1.19 G 0.71 D, 0.96 G 0.72 D, and 1.00 G 0.44 D at 4 weeks, 3 months, and 6 months, respectively, which is far greater than the values we observed with the prototype accommodating IOL. The accommodative movement of the 1CU IOL has also been evaluated. In a randomized study,4 IOL movement was measured by PCI between 18 months and 24 months postoperatively; the mean was 0.009 G 0.025 mm to 1.50 D near visual stimuli and 0.010 G 0.028 mm to 2.50 D near visual stimuli. These results are similar to our accommodating IOL results at 6 months. Forward movement of the 1CU IOL was significantly greater than that of the control IOL (3-piece AcrySof MA30), which moved backward with accommodative effort. The mean forward movement of the 1CU IOL after administration of pilocarpine was 0.220 G 0.169 mm, similar to the mean for the prototype IOL in our study (0.306 G 0.161 mm) at 6 months. These results are also comparable to those in a nonrandomized study by Kriechbaum et al.,30 who found that the mean forward movement of the 1CU IOL was 0.010 G 0.025 mm with near visual stimulation and 0.201 G 0.137 mm after administration of topical pilocarpine; the movement was measured with the laboratory prototype of the ACMaster PCI device between 1 year and 2 years postoperatively. The DCNVA was not significantly different from that with the 3-piece control IOLs. Another randomized fellow-eye comparison study31 found the median forward movement of the 1CU IOL was 314 mm after administration of topical pilocarpine; a monofocal 3-piece control IOL moved backward by 63 mm. The difference between the 2 IOL models was statistically significant. Overall, despite differences in haptic design, accommodative shift with the prototype IOL in our study appears comparable to that of the 1CU IOL, although we used AS-OCT rather than PCI to measure IOL movement. Other studies32–34 found that the 1CU IOL had better near visual performance than nonaccommodating control IOLs; however, these studies did not measure accommodation objectively. In a nonrandomized study, Dogru et al.35 found significantly better DCNVA in eyes with a 1CU IOL than in eyes with a 3-piece control IOL at 3, 6, and 12 months. In another randomized study,36 patients had bilateral implantation of 1CU IOLs, conventional monofocal IOLs, or multifocal IOLs. In the study, bilateral accommodating IOLs performed significantly better than bilateral monofocal IOLs in binocular uncorrected near visual acuity and binocular DCNVA, reading speed, and critical print size. Defocusing favored the accommodating IOL group over the monofocal IOL group at 3 months, but not at 18 months; significantly more patients in the accommodating IOL group than in the monofocal control group were spectacle independent.
The Crystalens AT-45 accommodating IOL (Bausch & Lomb) received U.S. Food and Drug Administration approval in November 2003 based on psychophysical assessments. This model, an early iteration of the Crystalens, is a modified plate-haptic silicone IOL. It has 2 plate haptics that are hinged adjacent to the optic. A study evaluating IOL shift with PCI7 showed that the Crystalens AT-45 IOL moved backward (mean 151 G 84 mm) after pilocarpine stimulation 3 months postoperatively, thus differing from the clinical behavior of the prototype accommodating IOL in our study. Using UBM, Marchini et al.37 assessed axial movement of the Crystalens AT-45 IOL using a different protocol and found a net forward IOL shift between relaxed accommodation (after topical cyclopentolate) and active accommodation (viewing a near stimulus at 40 cm). Marchini et al. found a mean change in ACD of 0.24 G 0.17 mm 1 month postoperatively and 0.17G 0.27 mm at 12 months. However, their study had several limitations. First, UBM is prone to misalignment off-axis and convergence effects from fellow-eye stimulation. Furthermore, the protocol measured the change in ACD from near visual stimulation to pharmacologic relaxation of the ciliary muscle with cyclopentolate, potentially exaggerating the results of IOL movement. Thus, the results of Marchini et al. cannot be compared with our results with the prototype accommodating IOL. There are fewer studies of the Tetraflex KH-3500 accommodating IOL (Lenstec, Inc.). This is a microincision 1-piece hydrophilic acrylic IOL with 2 haptics that, similar to those of the prototype IOL in our study, are thin and flexible with a closed-loop design. As with other accommodating IOLs, the subjective amplitude of accommodation was greater than the objective amplitude of accommodation (mean 3.10 G 1.60 D versus 0.39 G 0.53 D) between 2 weeks and 3 weeks postoperatively, although both measurements were significantly higher than with the control IOL (Softec 1, Lenstec, Inc.).6 These results were similar to those of the accommodating IOL in our study, which had a mean objective amplitude of accommodation 0.36 G 0.38 D at 1 month. In conclusion, the OPAL-A IOL, like other focus-shift accommodating IOLs, failed to show clinically meaningful IOL shift and objective accommodation with physiologic near visual stimulation. This IOL suffers from a flaw inherent to all focus-shift IOLs; that is, a large forward shift is required to achieve a clinically significant myopic refractive change. If achieved, large optic translations can result in iris chafing and pigment dispersion, compromising the safety of these IOLs. Thus, alternative lenticular strategies for restoring accommodation are necessary.
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First Author: Georgia Cleary, MBBS, MRCOphth Department of Ophthalmology, St. Thomas’ Hospital, London, United Kingdom