Visual Outcomes and Complications of Piggyback Intraocular Lens Implantation Compared to Aphakia for Infantile Cataract.

PURPOSE: To evaluate the long-term visual outcomes and complications of the piggyback intraocular lens (IOL) implantation compared to aphakia for infantile cataract. PATIENTS AND METHODS: In a comparative study from 1998 to 2007, piggyback IOL implantation (piggyback IOL group) was performed for 14 infants (23 eyes) with infantile cataract and 20 infants (32 eyes) who were aphakic (aphakia group) after infantile cataract surgery. Data were collected on logMAR visual acuity, and postoperative complications over a mean follow-up time of 6.2 ± 1.7 years and 5.8 ± 1.7 years.
RESULTS: The mean age at surgery was 7.5 ± 0.6 months and 6.0 ± 3.3 months for the piggyback and the aphakic group respectively (P > 0.05). At the last follow-up visit, visual acuity was 0.85 ± 0.73 (median = 0.70, interquartile range = 0.3-1.32) in the piggyback IOL group and 0.89 ± 0.56 (median = 0.86, interquartile range = 0.50-1.24) in the aphakic group (P > 0.05). There was a positive relationship between age and visual outcomes in the aphakic group (r = 0.4, P = 0.04) but not in the piggyback IOL group (P = 0.48). There was no significant difference between the mean myopic shift in the piggyback IOL group (-5.28 ± 1.06 D) and the aphakic group (-5.10 ± 1.02 D) (P > 0.05). The incidence of reoperation due to complications in piggyback IOL group was higher than aphakic group (%48 vs. %16, respectively, P ≤ 0.01). However, in patients older than 6 months, this risk was not significantly different compared to the aphakic group.
CONCLUSIONS: Although piggyback IOL implantation for infantile cataract is optically acceptable as a treatment option, there is no significant difference in visual outcomes compared to aphakia. The incidence in reoperation due to complications in patients aged 6 months or younger is higher than those treated with aphakia.

INTRODUCTION

Congenital cataract is an important cause of reversible blindness among children. The prevalence of congenital cataract is reported to be between 3.0 and 4.5 per 10,000 children.12 Timely cataract extraction, refractive correction and amblyopia management have a significant role in visual prognosis. The best optical management in cataract surgeries during the 1st year of life (infancy) remains controversial. A complicated aspect in cataract surgery among this group is the optimal optical correction after cataract surgery. A recent increase in intraocular lens (IOL) implantation in the pediatric population is due to technical developments and promotion of IOL technology3 however, there are some challenging factors in IOL implantation during infancy (the 1st year of life). IOL implantation in infants and children is not approved by the United States Food and Drug Administration due to greater tissue reactivity to IOL material. Another problem is the changing axial length and keratometry as children age, complicating permanent correction with IOLs.456 It has been documented that the axial length of the eye and the corneal curvature change logarithmically according to age, particularly during the first 2 years of life. The other challenging factors are related to the small size of the infantile globe, the growing pattern of the eye and the subsequent myopic shift of the eye, complicating IOL implantation in infants.378 Piggyback IOL implantation has been used for full optical correction during infancy.489 In this technique, a posterior permanent IOL is implanted in the capsular bag, and an anterior temporary IOL is implanted in the ciliary sulcus. With this technique, the myopic shift of the eye over time can be compensated with explantation of the anterior IOL.7 This concept was first proposed by Gayton and Sanders in 1993.8 In 2001 Wilson et al. proposed “temporary pseudophakia” for this technique of IOL implantation and demonstrated good visual outcomes.9 In 2009, Boisvert et al. reported a new theoretical strategy for choosing proper IOL power for achieving emmetropia after removal of the temporary IOL.4

In this study, we evaluate the long-term visual outcomes and complications of piggyback IOL implantation compared with aphakia and secondary IOL implantation in patients with infantile cataract.

PATIENTS AND METHODS

All infants who participated in our study were admitted to Rassoul Akram Hospital (a Referral Hospital in Tehran, Iran). Written informed consent for the study was obtained from parents or the legal guardian of the children. All parents or legal guardians underwent a full presentation detailing IOL implantation and aphakia with contact lens or spectacle correction. The research adhered to the tenets of the declaration of Helsinki and was approved by the Institutional Review Board and Ethics Committee of the Tehran University of Medical Sciences.

In this historical cohort study, piggyback IOL implantation was performed for 14 infants (23 eyes) (piggyback IOL group) with infantile cataract from 1998 to 2007. Furthermore, in the same time period, we evaluated 20 infants (32 eyes) who were candidates for infantile cataract surgery and subsequent aphakia (aphakia group) during the 1st year of life. In the aphakia group, 14 eyes received contact lens correction, 10 received spectacle correction and 8 eyes underwent secondary IOL implantation. Visual outcomes and complications were followed for a period of at least 4 years.

For all patients, we performed a systemic workup through a pediatrics consult. Keratometry, axial length, and white-to-white measurements were performed, and IOL implant power was calculated based on the Hoffer Q formula or SRK/T formula.10 In all patients, a limbal incision was carried out, and capsulotomy was performed using a vitrector. After aspiration of the lens material using a bimanual aspiration/irrigation device or the aspiration mode of the vitrectomy device, posterior capsulotomy was performed using a vitrector. Subsequent anterior vitrectomy was performed via the anterior approach. In patients who were selected for piggyback IOL implantation, a permanent polymethyl-methacrylate (PMMA) IOL was used followed by a temporary PMMA IOL placed in the sulcus. The power of the anterior IOL was calculated based on the estimated change in refraction during an infant's developmental period. In the majority of cases it was estimated to be about one-third of the total IOL power.4 Acetylcholine 1% (miochol) was used for intraocular instillation and the limbal incision was closed with an interrupted 10-0 nylon suture. One patient who was scheduled for piggyback IOL implantation formed a severe fibrin reaction during IOL implantation, and the surgery was converted to an aphakic procedure, and the patient was excluded from the study. For all patients subconjunctival long acting betamethasone was injected, and a diluted solution of betadine (5%) was applied at the end of the surgery. Antibiotic/corticosteroid and cycloplegic eyedrops were started 1-day postoperatively. Follow-up visits were scheduled for 1-day, 2 days, 1-week and 1-month postoperatively and further visits were scheduled according to the medical status of the patient. Visual acuities were measured using a tumbling E. The anterior segment, posterior segment, refraction, intraocular pressure (IOP) and ocular motility were checked at each visit (examination was performed under anesthesia if necessary). When the Hoffer Q formula or SRK/T formula predicted emmetropia after removal of sulcus fixated IOL, the anterior IOL was removed.

We did not perform a sample size calculation in advance (we recruited infants in the piggyback IOL group during the course of the study). However, based on the observed standard deviation of visual acuities in two groups (0.73 and 0.56 logMAR), our study has 20% and 40% power to detect 0.2 and 0.3 logMAR difference in visual acuity in two groups, respectively. To evaluate 0.2 logMAR difference in our study with a power of 95% and 0.05 of Type I error, 248 eyes (124 eyes in each group) were required. However, this sample size of infants was far too large to enroll from our center.

Visual acuities were changed to logMAR values for statistical analysis and for presenting the data in this study. To describe data, frequency was used for qualitative variables, mean, standard deviation, median, and range for quantitative variables. All analyses were performed with SPSS software (version 16; IBM Corp., Armonk, NY, USA). P <0.05 were considered statistically significant. The Kolmogorov–Smirnov test was used to evaluate the normal distribution of quantitative data. Based on this test, the Mann–Whitney or Student's t-test was used to compare the continuous variables between groups. The percent of complications in each group was compared using the two-sided Fisher's exact test. The Spearman correlation coefficient was calculated to evaluate the relation between variables.

RESULTS

A total of 55 eyes from 34 infants (17 males and 17 females) with infantile cataract were enrolled. There were 23 eyes of 14 infants (8 males and 6 females) in the piggyback IOL group. There were 32 eyes from 20 consecutive infants (9 males and 11 females) with infantile cataract who underwent cataract surgery without implantation IOL (aphakia group) in the same period. In the piggyback IOL group, five patients underwent unilateral cataract surgery. The patients in piggyback IOL group were followed up for 6.2 ± 1.7 years. In aphakic group (32 eyes), eight patients underwent unilateral cataract. The mean length of follow-up in the aphakic group was 5.8 ± 1.7 years, and follow-up lasted at least 4 years for both groups.

There were no statistically significant differences in age or any other demographic data between groups [Table 1]. Associated ocular abnormalities were persistent fetal vasculature (PFV) (5 cases), microphthalmos (axial length less than two standard deviations below the age-adjusted mean) (5 cases), nystagmus (14 cases) and strabismus (16 cases) [Table 2]. The first postoperative refraction at 1-month for the piggyback IOL group was +0.52 ± 1.58 D. The mean visual acuity in the piggyback IOL group was 0.85 ± 0.73 logMAR (median = 0.7 logMAR, interquartile range = 0.3 logMAR to 1.32 logMAR) at the end of follow-up. Age at the time of surgery was not significantly correlated to visual acuity (r = 0.155, P = 0.481). Thirteen eyes (41%) of this group underwent anterior IOL removal during the course of this study. Of these eyes, two eyes of one patient underwent Ahmed valve implantation which was associated with anterior IOL removal sooner than the expected, and the remaining 11 eyes underwent IOL explantation at the expected time. In these 11 eyes, the mean refraction was −0.40 ± 3.10 D, 1-month after IOL removal, and the visual acuity was 0.64 ± 0.46 logMAR (median = 0.59 logMAR, interquartile range = 0.32 logMAR to 0.93 logMAR) at the end of follow-up. The mean visual acuity in the aphakia group with secondary implantation of IOL (8 eyes) was 1.13 ± 0.89 logMAR (median = 0.96 logMAR, interquartile range = 0.47 logMAR to 1.67 logMAR) at the end of follow-up and the mean refraction for this group was −0.40 ± 1.57 1-month after IOL implantation. The mean visual acuity in the aphakia group without IOL implantation (24 eyes) was 0.81 ± 0.39 logMAR (median = 0.79 logMAR, interquartile range = 0.52 logMAR to 1.06 logMAR).

Table 1

Demographic data of patients

Table 2

Associated ocular abnormalities in piggyback and aphakic groups

There was no significant difference between the mean visual acuity in the aphakia group (0.89 ± 0.56 logMAR) (median = 0.86 logMAR, interquartile range = 0.50 logMAR to 1.24 logMAR) and the piggyback IOL group (0.85 ± 0.73 logMAR) (median = 0.79 logMAR, interquartile range = 0.32 logMAR to 1.22 logMAR) (Mann–Whitney test; P > 0.05). Considering two age groups (under and above 6 months old), there was no significant difference in visual acuity between groups for each age group [Table 3] (P > 0.05). In the aphakia group, there was a statistically significant relationship between age at surgery and visual acuity (r = 0.4, P = 0.04). In the piggyback IOL group, there were 3 (13%) cases of IOL capture that were easily repositioned under mask anesthesia. There were 2 (9%) cases of mild IOL decentration that did not require repositioning. There was 1 (4%) case of vitreous tag likely due to prolapse of tenacious vitreous despite meticulous attention during vitrectomy, adhering to the posterior site of the wound, causing mild decentration of IOL. The patient did not develop cystoid macular edema and was followed without any complication. There were 8 (35%) cases of visual axis opacification (VAO) also known as posterior capsular opacification and 2 (9%) cases of membrane formation that underwent reoperation for membrane removal and removal of the opacification. We did not encounter any significant anterior capsular phimosis leading to reoperation. Glaucoma was defined as IOP >21 mmHg associated with increased cupping of the optic disk compared to the baseline examination. There were 2 (9%) cases of glaucoma; both underwent a shunt procedure, and there were no cases of vitreous hemorrhage. There was 1 (4%) case of retinal detachment requiring vitreoretinal surgery (for one patient who underwent shunt insertion 1-month earlier). The incidence of reoperation due to complications in the piggyback IOL group was statistically significantly greater than the aphakia group (48% vs. 16% respectively, P = 0.03). There were 15 and 17 cases more than 6 months in the aphakic and piggyback groups respectively, and there was no significant difference between reoperation rates between groups after 6 months (6% vs. 9%) respectively. The comparative list of complications is presented in Table 3. VAO was statistically significantly higher in the piggyback IOL group compared to the aphakia group (8 out of 23 [35%] vs. 2 out of 32 [6%] in piggyback IOL and aphakic groups, respectively, P = 0.01). The mean spherical equivalent refraction change (using retinoscopy) at the spectacle plane 1-year postoperatively was defined as a myopic shift at the 1st year. This parameter was −5.28 ± 1.06 D in the piggyback IOL group and was −5.10 ± 1.02 D in the aphakic group (P > 0.05).

Table 3

Distribution of long-term postoperative adverse effects

DISCUSSION

Spectacles and contact lenses are solutions for optical correction in infantile aphakia after cataract surgery. However, there are some disadvantages related to contact lenses and incorrect methods of spectacle use. Advances in contact lens technology, have allowed successful use in aphakic infants,11 however, 50% of infants may experience poor compliance with contact lens wear.12 Visual performance after infantile cataract extraction has been related to the good compliance with contact lens wear.13 Hence, considering the degree of parental compliance with contact lens wear is critical.

IOL implantation in the pediatric population is gaining popularity.814 In a study using a mail out questionnaire surveying ophthalmologists in the UK and Ireland, only 25% of respondents preferred not to perform primary IOL implantation in a child under 1-year old with infantile cataract.15 There are reports of successful visual outcomes after primary implantation of IOLs in pediatric cataract surgery, especially for unilateral cataract surgeries; however, these studies have reported an increased risk of complications and reoperations.1617181920 Despite a primary posterior capsulectomy and anterior vitrectomy, VAO can occur after infantile cataract surgery. In our study, the rate of VAO was 35% (8/23) of patients in the piggyback IOL group and 6% (2/32) of patients in the aphakic group. Astle et al. reported a 70.8% risk of VAO in children younger than 1-year who underwent lensectomy and IOL implantation.19 Because of the high incidence of VAO, they proposed that cataract surgery and IOL implantation in children younger than 2 years should a two-stage procedure.21

Gupta et al.'s study of children <2 years old reported that primary implantation of IOL was a safe method of visual rehabilitation in this age group. They reported a low risk of VAO (6.7%) and none of their patients developed glaucoma postoperatively.22 A study from India proposed that primary IOL implantation was a successful method for correcting aphakia in children under 2 years old. They noted a 13.3% rate of VAO after cataract surgery.23

Lu et al. in a study on primary IOL implantation in infants aged 6–12 months documented a 26.9% risk of VAO.24 Trivedi et al.25 reported that 23.6% of infantile cataract and primary IOL implantation, required reoperation for VAO. This rate was higher in female infants but did not differ between various acrylic hydrophobic IOL models used in Trivedi et al.'s study.25 Wilson et al. reported that piggyback IOL group had a higher rate of reoperations compared to the patients with single IOL in the bag.8 According to the literature, the mean incidence of VAO in eyes after lensectomy, posterior capsulectomy, anterior vitrectomy and a hydrophobic acrylic IOL implantation is 44% (8.1–80%).26 The risk of VAO after cataract surgery increases with time.27 The risk for VAO is 2.7 greater when in infants under 6 months of age at the time of the surgery compared to infants older than 6 months.28

In our study, there were two cases of pupillary membrane formation (9%) in the piggyback IOL group leading to reoperation which is in line with other studies. The risk of membrane formation and VAO was higher in the pseudophakic group compared to the aphakic group.20 The source of the differences in the incidence of VAO may be related to patient age, the time since the surgery, the type of IOL and perhaps different threshold levels for detecting opacification.

Glaucoma is a postoperative complication of pediatric cataract surgery. The risk may increase with microcornea, microophthalmos, PFV and younger age.24 There is some controversy about the protective role of IOL implantation against glaucoma after infantile cataract surgery. For example, a study29 on infants who underwent cataract surgery in the 1st year of life, found a 13% chance of glaucoma in pseudophakic eyes compared to a 33% chance of glaucoma in aphakic eyes. However, they concluded that despite a significantly lower incidence of glaucoma, primary IOL implantation following cataract surgery in infants was not protective against glaucoma.29 They also concluded that the mean time of diagnosing glaucoma in pseudophakic eyes was lower than aphakic eyes, and younger infants at the time of the surgery (≤2.5 months) had higher risk of glaucoma.29 However, in this study, the mean age of aphakic patients was significantly lower than pseudophakic patients. Asrani et al.30 proposed two theories for this decrease in the risk of glaucoma; the first is that chemical components from the vitreous in aphakic eyes can damage the trabecular meshwork. The IOL and posterior capsule seal and block the chemical material to access the anterior chamber. Thus the IOL prevents glaucoma. The second theory is that the aphakic state damages the trabecular meshwork through a lack of support, the IOL prevents this structural damage thus reducing the risk of glaucoma over the long-term.30 Wilson et al. documented that no one of 15 eyes with implanted piggyback IOL had glaucoma compared to 6% of eyes with a single IOL implantation [Table 4].8 Present the different studies reporting pseudophakic glaucoma associated with primary implantation of IOL in infants. In our study, two eyes (9%) in the piggyback IOL group developed glaucoma compared to three eyes in the aphakic group (9%), and the difference was not statistically significant (P > 0.050). These results are comparable with two other large studies, which reported no difference between pseudophakic and aphakic groups.2031 However, glaucoma developed at a younger age in pseudophakic eyes. Interestingly, none of infants with secondary implants developed glaucoma or VAO after implantation.

Table 4

Previous studies of pseudophakic glaucoma associated with primary IOL implantation in infants

Choosing the correct IOL power in infantile cataract is complicated due to the constant growth of the eye during childhood. The axial length of an infant's eye increases with age, causing a myopic effect. This is compensated by a decrease in keratometric value, resulting in a logarithmic change in refractive error.42 While most of the corneal flattening is complete in the first 3 months, most of axial elongation occurs in the first 18 months.2942 Thus, refractive outcomes after IOL implantation may be different between studies depending on the IOL power used in cataract surgery. According to the changing pattern of axial length and keratometry, the highest change in refraction takes place during the 1st year after surgery. IOL implantation may slow axial length growth after childhood cataract surgery. Due to the shift in IOL position as the patient ages, the myopic shift in pseudophakic eyes is significantly greater than aphakic eyes, although in unilateral cataracts implanted with IOL, pseudophakic eyes showed the same axial length growth as the other normal eye.14 In our study, a myopic shift after 1-year postoperatively, in the piggyback IOL group and aphakic group, was −5.28 D and −5.10 D respectively. There was no significant difference between these two groups (P > 0.05). This may be related to pushing the posterior lens by the anterior lens, which may compensate the difference between myopic shift in pseudophakic and aphakic eyes.24313342434445 Lloyd et al. studied 25 infants who underwent primary IOL implantation before 1-year of life and documented an average 4.83 D myopic shift at 12 months. The mean myopic shift was 5.3 D in infants who underwent surgery before 10 weeks of age. Their results were comparable with other studies.13142743

In our study, the mean refraction 1-month after piggyback IOL implantation was +0.52 ± 1.58 D, thus refractive outcome after piggyback IOL implantation seems to be favorable 1-month postoperatively compared to the aphakic group. At the end of follow-up, the visual acuity in the piggyback IOL group was 0.85 ± 0.73 logMAR. In the piggyback IOL group, the anterior IOL removal, and mean refraction was −0.40 ± 3.10 D that was acceptable and the visual acuity was 0.64 ± 0.04 logMAR. Although visual acuity in the piggyback IOL group was better than the aphakic group, the difference was not statistically significant (P > 0.05). There was no significant difference in visual acuity between unilateral aphakic and piggyback groups (5 vs. 8 cases). This finding could be due to small sample size in each of these groups. In general, the rate of complications and reoperations was higher in the piggyback IOL group than the aphakic group. The mean age of these complications excluding strabismus surgery and one case of retinal detachment in aphakic patients was approximately 6 months or lower [Table 3]. Thus caution is advised when performing piggyback IOL implantation at this age. Interestingly the rate of complications was similar between in patients older than 6 months. In this age group, although visual acuity in the aphakic group was higher than the piggyback IOL group, it was not statistically significant (P > 0.05). As mentioned, there was a relationship between patient age at the time of operation and visual acuity in the aphakic group. The lower correlation coefficient in the piggyback IOL group may be related to the higher reoperation rate and adverse events in this group. A drawback of this study was the relatively low number of the cases.

CONCLUSION

Although piggyback IOL implantation for infantile cataract is optically acceptable as a treatment option, and there is no significant difference in visual outcomes compared to aphakia. The incidence of reoperation in patients aged 6 months or younger is higher than those treated with aphakia. For the age group older than 6 months, this incidence showed no difference compared to the aphakic group, although there was no significant difference in visual acuity in this group compared to the aphakic group. However, the limitation of aphakic correction, especially in relation to noncompliance in children during their development should be considered. More studies are warranted for this age group, especially for unilateral cataract cases.

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Nil.

Conflicts of interest

There are no conflicts of interest.