|Year : 2013 | Volume
| Issue : 3 | Page : 207-211
Diffractive multifocal intraocular lens compared to pseudo-accommodative intraocular lens implant for unilateral cataracts in pre-presbyopic patients
Rajesh Subhash Joshi
Department of Ophthalmology, Indira Gandhi Government Medical College, Nagpur, Maharashtra, India
|Date of Web Publication||9-Jul-2013|
Rajesh Subhash Joshi
77, Panchtara Housing Society, Manish Nagar, Somalwada, Wardha Road, Nagpur - 440 015, Maharashtra
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Purpose: To evaluate the efficacy of diffractive multifocal and pseudo-accommodative IOLs in pre-presbyopes with cataract.
Materials and Methods: A prospective randomized control study was performed on patients with cataract in the pre-presbyopic age group. Patients were randomly allocated to 2 groups: Group 1 comprised 12 patients who underwent implantation of a diffractive multifocal IOL and Group 2 comprised 13 patients who underwent implantation of a pseudo-accommodative IOL after standard phacoemulsification. Efficacy was measured by postoperative distance and near uncorrected visual acuity, contrast sensitivity, spectacle independence, and glare and halo.
Between-group comparison was performed with the unpaired t test. Fisher's exact test was used for categorical variables. All the tests were two-sided with confidence interval set at 95%.
Results: The study patients were aged 22-35 years and included 14 females and 11 males. All examinations were performed 6 months postoperatively by a second observer unaware of the study objectives. Mean uncorrected distance visual acuity was 0.125 ± 0.1 LogMAR in Group 1 and 0.1385 ± 0.1 in Group 2 (P = 0.7993). Near visual acuity was 0.0917 ± 0.1 in Group 1 and 0.386 ± 0.2 in Group 2 (P < 0.0001). Contrast sensitivity was good in both groups based on the Pelli-Robson chart (P = 0.3919). Night-time glare was present in 3 (25%) patients in Group 1 and in 2 (15.4%) patients in Group 2. No patients in either group had difficulty driving during the day or night. Ten patients in Group 1 (83.3%) and 7 patients in Group 2 (53.85%) had spectacle independence (P = 0.1249).
Conclusion: Greater proportions of patients who underwent diffractive multifocal implantation achieved functional distance and near vision as compared to those in the pseudo-accommodative IOL group. There was greater variability in near vision in patients who received the pseudo-accommodative IOL as compared to those in the multifocal IOLs. Contrast sensitivity remained adequate in both the groups. There were more glare and halos in the multifocal group as compared to those in the pseudo-accommodative group. More patients achieved spectacle independence with multifocal IOLs.
Keywords: Accommodative IOL, Contrast Sensitivity, Diffractive Multifocal Intraocular Lens, Phacoemulsification, Pre-Presbyopic Cataract
|How to cite this article:|
Joshi RS. Diffractive multifocal intraocular lens compared to pseudo-accommodative intraocular lens implant for unilateral cataracts in pre-presbyopic patients. Middle East Afr J Ophthalmol 2013;20:207-11
|How to cite this URL:|
Joshi RS. Diffractive multifocal intraocular lens compared to pseudo-accommodative intraocular lens implant for unilateral cataracts in pre-presbyopic patients. Middle East Afr J Ophthalmol [serial online] 2013 [cited 2020 Aug 14];20:207-11. Available from: http://www.meajo.org/text.asp?2013/20/3/207/114792
| Introduction|| |
Presbyopia correction is challenging in patients undergoing cataract surgery. An ideal intraocular lens (IOL) simulates the original function of the crystalline lens and provides the patient with multifocal vision.  Current strategies to correct postoperative presbyopia include reading glasses, contact lenses, or monovision. Each of these modalities has some inherent disadvantages.
Young patients with unilateral or bilateral cataracts due to a developmental reason, trauma, diabetes, and steroid-induced cataracts requiring cataract surgery may face difficulties adapting to postoperative presbyopia. Implanting monofocal IOL forces them to use bifocal glasses, which may be cosmetically unacceptable. Clinical studies have shown improved uncorrected near visual acuity and decreased spectacle dependence in patients with multifocal IOLs as compared to monofocal.  Pseudo-accommodative IOLs were also developed to reduce spectacle dependence. Implantation of either multifocal or accommodative lenses in the posterior chamber after cataract surgery improves both near and distance vision. But standard visual acuity is a crude measurement of visual performance and cannot represent all aspects of visual function. Therefore, objective evaluation of visual performance of these IOLs by contrast sensitivity testing is important.
Young patients' activities range from driving, reading, writing, and computer work, which are better indicators of visual performance of these two types of lenses. Considering this reason, we performed a study to compare accommodative and diffractive multifocal IOLs in a randomized, control trial in pre-presbyopic patients with cataract. In this study, we compared the efficacy, visual acuity, contrast sensitivity, spectacle independence, and glare and halos of the two different lenses.
| Materials and Methods|| |
The study comprised of 25 patients who were pre-presbyopic with cataracts who were randomly allocated to receive either an accommodating or multifocal IOLs from January 2007 through February 2008 in a medical college. Research and ethical approval for the study was obtained from the Research and Ethics Committee of the medical college.
The patients were divided into 2 groups based on the type of IOL that was implanted: Group 1 was comprised of 12 patients implanted with multifocal diffractive IOLs (i-diff, Care group, India) and Group 2 was comprised of 13 patients who underwent implantation with an accommodating IOL (Ultrasmart, Appasamy associates, India).
Inclusion criteria were pre-presbyopic age with a unilateral cataract, corneal astigmatism less than 1.0 D, axial length between 22.0 to 25.0 mm, and preoperative pupil size less than or equal to 6 mm. Exclusion criteria were subluxated cataracts, distorted pupil, retinal pathology, prior retinal surgery or laser treatment, high myopia and hyperopia, amblyopia, glaucoma, history of previous refractive surgery, other eye with a monofocal implant and monocular patients. Intraoperative exclusion criteria were zonular damage, vitreous loss, capsulorhexis tear, and pupillary trauma during the surgery.
All patients underwent a thorough informed consent procedure that involved a discussion of the risks and benefits of the implants. This study adhered to the tenets of the Declaration of Helsinki. Patients were randomized to receive either a multifocal diffractive IOL with a 4.0 D additions or a pseudo-accommodative IOL. The randomization schedule was generated by software from Geoffrey C. Urbainiak available online (www.randomizer.org). On the day of surgery, the patient was asked to select two envelopes containing either a multifocal or accommodative IOL. The surgeon was not aware of the patient intervention until the selection. A second observer performed all the examinations after 6 months. The results were disclosed after analysis of data. Considering near visual acuity as the most important criteria, the power of study was 85% with the available sample size (n = 25).
Preoperatively, all patients underwent a thorough examination that included measurement of distance and near visual acuity with an Early Treatment Diabetic Retinopathy Study (ETDRS) chart, slit lamp evaluation, grade of cataract (Emery and Little classification),  applanation tonometry, keratometry, and dilated fundus examination. Axial length was measured by immersion biometry. IOL power was calculated with the Sanders, Retzlaff, and Kraff-II theoretical formula (A-Constant of diffractive multifocal and pseudo-accommodative IOL = 118.0).
A single experienced surgeon performed all cataract extractions with the patient receiving topical (0.5%) proparcaine 5 min prior to the surgery. The topical anesthetic was supplemented with 0.5 ml subconjunctival injection of 2% xylocaine nasally. All patients underwent a 2.8 mm clear corneal temporal incision. A 5.5 mm capsulorhexis was created to cover a 6 mm optic of the IOL. The phacoemulsification settings were vacuum 250 cc, flow rate 30 cc, and power 30-50% in a pulse mode (Swisstech, Oertli phacoemulsification system, Switzerland). A thorough cortical wash and vacuum polishing of the posterior capsule was performed. After completion of the procedure, patients received either multifocal diffractive IOL with a 4.0 D additions or a pseudo-accommodative IOL, placed in the capsular bag. All the operations were uneventful.
The diffractive multifocal IOL has a 6 mm optic with 12.5 mm overall diameter, whereas the pseudo-accommodative IOL has a 6 mm optic with 11 mm overall length with 4 flexible haptics designed to allow the lens to move anteriorly in the capsular bag secondary to ciliary muscle contraction. Both the lenses have an aspheric optic, 360° square edge and are made of hydrophilic acrylic material.
Following surgery, the patients were treated with combined antibiotic and steroids drops 4 times per day for 1 month. All patients had a routine 1-day postoperative examination. All study examinations were performed 6 months postoperatively by the second examiner, who was unaware of the objective of the study. The examination included measurement of uncorrected visual acuity (UCVA) and best corrected visual acuity (BCVA) at 4 m with an illuminated chart for distance visual acuity and 40 cm for near visual acuity with an ETDRS chart. Photopic lighting conditions were maintained for all visual acuity tests.
Contrast sensitivity was tested at 1 meter with the Pelli-Robson chart. Spectacle independence was based on whether patients required glasses for routine work. The data were entered in an excel sheet and statistical analysis was performed with SPSS software, 13.0 (IBM Corp., New York, NY, USA). Between-group comparison was performed with the unpaired t-test. Fisher's exact test was used for categorical variables. All the tests were two-sided with confidence interval set at 95%.
A P-value < 0.05 indicated statistical significance.
| Results|| |
Patients ranged in age from 22 years to 35 years (29.52 ± 4.1 years and included 14 females (56%) and 11 males (44%). Grade 1 nuclear sclerosis was present in 18 (72%) patients and grade 2 in 7 (28%) patients. All patients underwent unilateral IOL implantation. Surgery was uneventful and successful in all patients. The capsulorhexis remained intact in all patients with the IOLs were well-centered inside the capsular bag. There were no cases of rupture of posterior capsule or vitreous loss.
The postoperative course was uneventful in all patients. During follow-up, the IOL remained well-centered in the capsular bag in all patients. One patient in each group developed posterior capsular opacification (PCO) that did not require YAG capsulotomy as it was thin and not affecting vision. There were no "signs of shrinkage" of rim of the anterior capsular margin in the follow-up period.
Visual acuity and contrast sensitivity
The mean uncorrected distance visual acuity was 0.125 ± 0.1 logMar (range, 0 logMAR to 0.3 logMAR) in Group 1 and 0.1385 ± 0.1 logMAR (range, 0 logMAR to 0.3 logMAR) in Group 2 (P = 0.7993, two tailed analysis). Of note, both groups had the same range.
There was a statistically significant difference between groups in near vision. Mean near vision was 0.0917 ± 0.1 in Group 1 and 0.3846 ± 0.2 in Group 2 (P < 0.0001). The range of visual acuity in group 2 was variable from 0.1-0.6.
Mean contrast sensitivity was 1.527 ± 0.1 in Group 1 and 1.575 ± 0.2 in Group 2 (P = 0.3919).
Spectacle independence was assessed at 6 months according to a pre-prepared questionnaire [Table 1]. Group 1 patients were satisfied with unaided visual acuity. Two patients (16.7%) in this group required spectacles, of which 1 patient (8.33%) required spectacles full time.
|Table 1: Spectacle independence in both patients who underwent monocular implantation of a multifocal or accommodating intraocular lens|
Click here to view
In Group 2, 7 patients (53.85%) did not require spectacles. The difference between groups was not statistically significant (P = 0.1249).
Glare and halos
Postoperative night-time glare was present in 3 (25%) patients in multifocal group and 2 (15.4%) patients in Group 2. One patient in Group 2 complained of halos. No patients in either group had difficulty in driving in photopic or scotopic conditions.
| Discussion|| |
A major concern after implantation of monofocal lens in a young patient with a unilateral cataract is near vision. The loss of accommodation in this group of patients can be particularly difficult because of their active lifestyle. Patients implanted with monofocal IOLs have little or no depth of focus in an operated eye, yet normal accommodation in a fellow un-operated eye. For binocular functioning, we believe that young patients with an uncomplicated unilateral cataract are suitable to undergo implantation of either diffractive or accommodative lenses, which provide distance and near vision.
Cillino et al.,  compared a new generation of diffractive multifocal IOLs (Tecnis ZM 900; AMO Inc., Abbott Park, Ill., USA) with monofocal IOLs and found that multifocal IOLs provide better near and distance visual acuity and greater spectacle independence (87.5%) than monofocal IOLs (20%). A comparison of accommodative IOLs (Crystalens HD) with monofocal IOL (2010) also found that uncorrected near visual acuity was statistically significantly better in the accommodating IOL group as compared to the monofocal group (J5 versus J3; P = 0.01).  However, the accommodative benefit of accommodative IOLs decreases with time due to capsular fibrosis. 
Our study suggests that implantation of diffractive multifocal or accommodative IOLs in patient whose other eye is phakic provides good functional vision for distance. We did find a statistically significant difference in near vision between groups (P < 0.0001). Vries et al.,  reported performance of an Acrysof ReSTOR IOL (FDA approved) at 6 months. They found that monocular uncorrected distance visual acuity was 0.128 ± 0.1 logMAR and near visual acuity was 0.020 ± 0.1 logMAR.  This correlates with the visual performance of the diffractive multifocal IOL in our study. Claoue  compared the Array multifocal (AMO Inc., Abbott Park, Ill., USA) with 1CU accommodating IOL (HumanOptics AG, Erlangen, Germany). Claoue  found a statistically significantly greater proportion of the multifocal IOL group achieved near UCVA of N/5 or better as compared to the accommodating IOL group (76.5% versus 44.4% respectively). Claoue  also found that 94.4% patients with multifocal IOLs and 50% with accommodating IOLs reported spectacle independence. These outcomes correlate with our study.
The mechanism of an accommodative IOL is the focus shift principle that allows pseudophakic accommodation.  We found the patients with an accommodative IOL had variable near vision performance ranging from 0.1 to 0.6 logMAR. This is in contrast to the near vision performance of the multifocal group, which was consistent (0-0.2 logMAR). This could be due to variable accommodation of the accommodative IOLs.
A long-term study of accommodative lenses has shown loss of accommodative power due to high incidence of anterior and posterior capsule opacification.  In our study, 1 patient in each group had faint PCO and no signs of anterior capsular fibrosis. Reduced PCO could be due to meticulous polishing of the posterior capsule and the square edge of the lens. However, long-term follow-up of these patients is important. Complications such as decreased near vision due to loss of accommodative power of the lens or lens shift in the bag due to capsular fibrosis needs to be considered while implanting these lenses in young patients. Development of posterior segment pathology requiring visualization of the peripheral retina and treatment of retinal lesions laser therapy or surgery should also be considered when opting for these lenses.
Ten (83.3%) patients in Group 1 and 7 (53.85%) patients Group 2 were spectacle independent (P = 0.1249). Two patients in Group 1 had to use spectacles for distance and near, while 5 patients in Group 2 had to depend on spectacles for near (P = 0.1070). However, the difference between groups was not statistically significant. This could be because of the small sample size. It is comparatively easy to recruit many patients with senile cataracts than in a younger age group. Second, the eye dominance with unilateral implantation could not be ascertained from our data.
Previous studies have reported a diminution in contrast sensitivity after implantation of multifocal lens as compared to monofocal implants.  This is because of the division of light energy through two focal points produced by a multifocal IOL.  In our study, contrast sensitivity values were lower in diffractive multifocal group as compared to accommodative group; however, there was no significant reduction in contrast (P = 0.3919). In an accommodative IOL, contrast sensitivity is less of an issue because the lens optic is similar to a monofocal implant and they work independent of the pupillary size. Mesci et al.,  evaluated visual acuity and contrast sensitivity after accommodative, refractive, and diffractive multifocal IOL implantation. They concluded that diffractive multifocal IOL resulted in more favorable visual acuities and higher contrast values than accommodative and refractive multifocal IOLs. 
Glare and halos are dyphotopsias that occur with multifocal and accommodative IOLs. No patients in either group had daytime glare postoperatively; however, 25% patients in Group 1 and 15.4% patients in Group 2 had night-time glare. Studies from the western hemisphere have reported an incidence of glare and halos at 40.4% after diffractive multifocal IOL implantation.  Since high-contrast conditions, i.e., very bright light source in the presence of a very dark background, is required to stimulate halos for both distance and near,  day-time glare is less of an issue in our area. Night-time glare may be more likely because of non-cataractous phakic and intraocular stray light levels that are higher than levels in eyes with a monofocal or multifocal IOL.  These ocular stray lights may explain night glare reported with the diffractive multifocal group. In an accommodative IOL, the lens optic in the pupillary area is similar to a monofocal implant; however, once the pupil dilates, the edges of the diffractive steps present in the peripheral optic can cause glare. However, no patients in either group complained of difficulty in driving at night or daytime.
Is summary, unilateral implantation of either diffractive multifocal or an accommodative IOL in a pre-presbyopic cohort with cataract provides good visual outcome. More patients with accommodative IOLs were dependent on spectacles for near vision; however, the difference between groups was not significant statistically. Despite that the sample size is small, this study is unique in comparing young patients with cataract.
| Acknowledgement|| |
I thank Dr. Avinash Turankar, Associate Professor, Department of Pharmacology, Government Medical College and Hospital for the statistical assistance.
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