Graefes Arch Clin Exp Ophthalmol DOI 10.1007/s00417-014-2689-0
CATARACT
Hydrophobic acrylic versus polymethyl methacrylate intraocular lens implantation following cataract surgery in the first year of life Jagat Ram & Vaibhav K. Jain & Aniruddha Agarwal & Jaidrath Kumar
Received: 11 April 2014 / Revised: 25 May 2014 / Accepted: 28 May 2014 # Springer-Verlag Berlin Heidelberg 2014
Abstract Purpose To evaluate complication rates following implantation of hydrophobic acrylic versus polymethyl methacrylate (PMMA) intraocular lens (IOL) with cataract surgery in infants. Methods Records of children undergoing cataract surgery with IOL implantation in first year of life were retrospectively reviewed. Infants were divided into two groups—hydrophobic acrylic IOLs were implanted in group A, and PMMA IOLs in group B. Outcome measures included incidence of complications, additional surgical procedures, and refractive error changes. Results One hundred and thirteen eyes of 113 children (75 males) with mean age of 6.49±3.56 months were included. Group A included 62 eyes, and group B included 51 eyes. The two groups did not differ significantly in terms of age and axial length. There was no significant difference between the groups for incidence of posterior capsular opacification (PCO), pupillary membranes, glaucoma, fibrin on IOL surface or IOL malposition (p=0.09). Development of PCO was delayed in group A (p=0.049). Thirteen eyes of group A and 18 eyes of group B required additional surgical intervention (p=0.20) in the follow-up visits. Conclusion Comparable complications may be expected in infants with PMMA and hydrophobic acrylic lenses. Children implanted with PMMA IOLs may require earlier surgical reintervention for PCO. J. Ram (*) : V. K. Jain : A. Agarwal : J. Kumar Department of Ophthalmology, Advanced Eye Centre, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh 160012, India e-mail:
[email protected] A. Agarwal Ocular Imaging Research and Reading Center (OIRRC), Stanley M. Truhlsen Eye Institute, University of Nebraska Medical Center (UNMC), Omaha, NE, USA
Keywords Pediatric cataract . Cataract surgery in infant . Intraocular lens . Hydrophobic acrylic . Polymethyl methacrylate . Posterior capsule opacification
Introduction There has been an increasing trend towards the use of intraocular lens (IOL) for visual rehabilitation after cataract surgery in children below 1 year of age [1, 2]. Although some paediatric cataract surgeons prefer primary implantation of IOL in infants because of improved surgical techniques [3, 4], newer IOL designs [5–8], better estimation of IOL power calculation [9, 10], and predictable rates of postoperative complications and their management [11–13], this topic remains controversial. The most important challenge in the surgical management of cataract in infancy is prevention of posterior capsular opacification (PCO) and pupillary membrane formation due to high inflammatory response [14]. Main focus of paediatric cataract surgery has been the management of posterior capsule and the role of IOL material in preventing PCO [15–17]. In adults, available literature points towards lower PCO rates after implantation of hydrophobic acrylic IOLs as compared to polymethyl methacrylate (PMMA) IOLs [18, 19]. However, studies including children represent a heterogeneous cohort, with very few infants included in the analysis [17, 20, 21]. With this limited data, detailed analysis of complication rates between the two IOL types in infants has not been performed so far. While it is preferable to use hydrophobic acrylic IOLs over PMMA IOLs in adults due to their advantages such as smaller incision size and fewer postoperative interventions for PCO, we do not have sufficient data encouraging or refuting this claim in infants. In this study, we compared the complication and additional surgical intervention rates in infants
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undergoing primary IOL implantation with either hydrophobic acrylic or PMMA IOLs.
Material and methods Database maintained by the pediatric ophthalmology services in the Department of Ophthalmology at the Post Graduate Institute of Medical Education and Research was retrospectively reviewed to obtain records of children undergoing cataract surgery with IOL implantation less than 1 year of age from January 2007 to December 2009. Institutional ethical clearance was obtained to carry out this study, and the study adhered to the tenets of Helsinki. Children with both unilateral and bilateral congenital cataracts with minimum follow-up of 1 year were included in the study. However, for the purpose of analysis and to avoid correlation errors [22], only the first eye undergoing surgery in children with bilateral cataract was included. Children with other associated ocula r abnormalities including microphthalmos, corneal pathologies, persistent fetal vasculature, retinal disorders, and bupthalmos were excluded. Baseline complete ophthalmological examination was performed, including axial length measurements using A-Scan and keratometry measurements. Preoperative examination under anaesthesia was performed in uncooperative children. Prior to surgery, intraocular pressure (IOP) measurement was performed using Perkin’s tonometer, and indirect ophthalmoscopy was performed to check the status of the posterior segment. IOL power calculation was as per guidelines by Dahan and Drusedau [23]. Under-correction of 20 % was performed for calculating the IOL power based on age. Preoperatively, the parents/guardians were asked regarding the type of IOL to be implanted. The IOL implanted depended upon the choice exercised by the parents/guardians, largely based on affordability. The children were divided into two groups—group A included children who were implanted hydrophobic acrylic IOL, and group B included children who were implanted PMMA IOL. All surgeries were performed under general anesthesia by single surgeon (J.R). The technique of the surgery was same in all cases except for smaller incision size in group A (2.8 mm versus 5.5 mm). Anterior continuous curvilinear capsulorhexis (CCC) of approximately 5 mm was performed. Trypan blue dye (0.06 %) was used to stain the anterior capsule. Multi-quadrant hydrodissection was followed by irrigation/aspiration of the nucleus and cortex using Alcon Infiniti System (Alcon Labs Inc. Fort Worth, TX, USA). Primary posterior capsulotomy (PPC) of 3–3.5 mm was performed. Anterior vitrectomy (AV) was done in all cases, and IOL was implanted in the capsular bag. Either foldable hydrophobic acrylic (Alcon ®SA60AT/MA60AC or Sensar OptiEdge ®/Tecnis Acrylic ®, AMO, Abbott Park, IL,
USA) or polymethyl methacrylate (PMMA) IOLs (Aurolens ®, Aurolab, Madurai, India or Pharmacia 811C) were used (Table 1). The incisions were well-secured with 10–0 monofilament nylon interrupted sutures in both groups. A subconjunctival injection of gentamicin 20 mg and dexamethasone 4 mg was given at the end of surgery. Postoperatively, all the patients received topical betamethasone (0.1 %) instilled 8 to 10 times a day; moxifloxacin 0.5 % 4 times and homatropine 2 % twice daily and titrated further according to the level of ocular inflammation over a period of 6 weeks. Removal of nylon sutures was performed between 4 and 6 weeks postoperatively. Children were evaluated postoperatively at 1 week, 3 months, 6 months, every 3 months in the next year and then 6 monthly thereafter. Postoperative examinations included detailed clinical examination, retinoscopic measurements and periodic examination under anaesthesia for assessment of clarity of visual axis, IOL position, and measurement of IOP. Testing for refraction was performed by a single experienced pediatric optometrist, and mean retinoscopic spherical equivalent (MRSE) was calculated for every patient. The outcome measures included incidence of postoperative complications and posterior capsular opacification (PCO), requirement of any additional intraocular surgical procedures, changes in refraction, and IOP. Glaucoma was diagnosed in the presence of sustained rise in IOP of >21 mmHg and any one of the following: progressive optic disc changes, corneal enlargement, increased optic nerve cupping ≥ 0.2, or presence of epithelial edema/photophobia with corneal clouding. Other complications such as pupillary membrane, optic capture, IOL dislocation or subluxation, fibrin and pigments on IOL, hyphaema, phthisis bulbi, and endophthalmitis were noted. The results were analyzed using GraphPad Prism software version 6.0. The value of significance was set at 5 %. Age and axial length were compared using Student’s t-test. IOL-related complications were compared in either group using Chi-Square test or Fisher’s exact test, whichever was applicable. The complications following cataract surgery were analyzed as distinct events, and calculated in terms of per eye-year. Kaplan–Meier survival graphs for complications and requirement of additional surgery were analyzed using the Log-Rank statistics.
Results One hundred and thirteen eyes of 113 children fulfilling the inclusion criteria were included in the study. The mean age of all the children in the study was 6.49±3.56 months. There were 75 males and 38 females in the study with a mean axial length of 19.21±1.75 mm. Thirty-two children (28.31 %) were diagnosed with unilateral cataract, and 81 (71.68 %) had bilateral cataract. Group A included 62 children (22 females), and group B included 51 children (16 females).
Graefes Arch Clin Exp Ophthalmol Table 1 Details of the design of the intraocular lens (IOL) used in the study IOL name (Manufacturer)
Type
SA60AT (Alcon)
1-piece hydrophobic foldable Sensar OptiEdge 3-piece hydrophobic (AMO) foldable Tecnis Acrylic 3-piece hydrophobic (AMO) foldable Aurolens (Aurolab) 1-piece non-foldable 811C (Pharmacia) 1-piece non-foldable
Material, water content
Refractive Length, optic size, haptic index angulation, edge
Copolymer of phenylethyl acrylate and phenylethyl methacrylate, 0.2 % Copolymer of ethyl acrylate and ethyl methacrylate (optic), polymethyl methacrylate monofilament (haptic), 0.69 % Copolymer of ethyl acrylate and ethyl methacrylate (optic), polymethyl methacrylate monofilament (haptic), 0.69 % Polymethyl methacrylate, 0.22 % Polymethyl methacrylate, 0.22 %
1.55
Two children had a history of preterm delivery, but without any post-natal complications. The mean age of children in group A was 6.10 ± 3.53 months. Mean axial length measured preoperatively was 19.38±1.65 mm in this group. Group B included children with a mean age of 6.96±3.54 months and axial length of 19.04±1.85 mm. The mean IOL power implanted was 25.81± 2.70 in group A and 26.13±2.52 D in group B. There was no significant difference in the baseline preoperative parameters, as shown in Table 2. All children in either group underwent cataract surgery with implantation of IOL in the capsular bag after successful PPC and anterior vitrectomy. In group A, Alcon SA60AT IOL was implanted in 34 eyes (54.84 %), Sensar OptiEdge in 14 eyes (22.58 %), Tecnis Acrylic IOL in four eyes (6.45 %), and Alcon MA60AC in ten eyes (16.13 %). Patients of group B were implanted Aurolab PMMA IOL in 34 eyes (66.67 %) and Pharmacia 811C IOL in 17 eyes (33.33 %). All children completed 1 year of follow-up, and records were available for 58 children (51.32 %) up to 2 years and 33 children (29.20 %) up to 3 years. Overall mean postoperative follow-up period for all the patients was 26.02±19.34 months. Retinoscopy was performed for evaluation of refractive error in all children periodically. Taking all the children together, the MRSE values obtained at 6 months postoperative were 2.27±3.09 D, 1.58±3.27 D at 1 year, 0.70±3.92 D at 2 years and −0.25±3.97 D at 3 years postoperatively. Eleven eyes (17.74 %) of group A developed PCO after a mean interval of 8.38±3.25 months following surgery. The Table 2 Demographic details by the intraocular lens type Characteristic
Group A
Group B
P value
Mean age (years) Male:female Axial length (mm) Intraocular pressure (mm Hg) Mean IOL power (dioptres)
6.09±3.53 40:22 19.38±1.65 12.32±2.39 25.81±2.70
6.96±3.54 35:16 19.04±1.85 12.24±2.32 26.13±2.52
0.199 0.210* 0.313 0.845 0.525
*
Chi-Square test
1.47
13 mm, 6 mm, 0°, sharp posterior edge 13.5 mm, 6 mm, 5°, squared posterior edge 6 mm, 5°, squared posterior edge
1.49 1.49
13 mm, 6 mm, 10°, rounded edge 13 mm, 6 mm, 0°, rounded edge
1.47
incidence of PCO development in this group was 10.70 % per eye-year. In group B, PCO developed in 17 eyes (33.33 %) 6.31±3.22 months after cataract surgery, with an incidence rate of 11.96 % per eye-year. Although there was a higher number of patients in group B developing PCO, this did not reach statistical significance (p=0.09). Kaplan–Meier survival curve for the development of visual axis obscuration due to formation of PCO or pupillary membranes is shown in Fig. 1. The distribution of eyes developing PCO is detailed in Fig. 2. The occurrence of PCO was significantly delayed in patients of group A as compared to group B (p=0.049). Incidence of pupillary membrane formation was 4.86 % per eye-year in group A, and 2.11 % per eye-year in group B. The incidence of glaucoma was 3.89 % per eye-year in group A, and 2.11 % per eye-year in group B. Glaucoma was diagnosed after 15± 5.71 months in group A and 15.33±5.51 months in group B. There was no statistically significant difference in the incidence of any complications between the two groups (Table 3). One eye in group B developed acute endophthalmitis 5 days after surgery, which progressed to phthisis bulbi. This was a child with unilateral cataract undergoing a phacoemulsification at 2 months of age. This child received aggressive intravenous anti-microbial therapy combined with pars plana vitrectomy. In three eyes postoperatively, the IOL was found to be located in the sulcus within 2 months following surgery; these were two eyes in group A, and one eye in group B. In one eye of group A, one haptic of the IOL was in the bag and the other in the sulcus. No additional surgical procedures were required in these eyes. IOL dislocation into vitreous cavity was noted in one eye in group B 6 months after surgery. This case was managed by pars plana vitrectomy and removal of IOL. Subsequently, the child was taken up for transscleral fixation of IOL. Additional intraocular surgical procedures were performed for VAO secondary to either PCO or pupillary membranes in 13 eyes (20.97 %) in group A and 16 eyes in group B (31.37 %). There was no statistical difference in the number of patients subjected to additional surgery for clearance of visual axis in the two groups (p=0.20). The Kaplan–Meier survival curve for patients who were subjected to additional
Graefes Arch Clin Exp Ophthalmol Fig. 1 Survival curve for infants who developed visual axis obscuration due to posterior capsular opacification or pupillary membranes following cataract surgery in either group. The LogRank statistic is 1.34 and p=0.246
surgery is shown in Fig. 3. Piggy-back IOL implantation was performed in one eye of a patient in group B due to high myopic shift in the postoperative period, resulting in MRSE value of −6.25 D. The patient with IOL dislocation was managed with IOL removal, pars plana vitrectomy and trans-scleral fixation of IOL. None of the eyes required surgical correction of IOP. Table 4 summarizes these postoperative interventions.
Discussion In adults, hydrophobic acrylic IOLs have shown superior performance and fewer complication rates as compared to PMMA IOLs [18, 19]. The present study was undertaken to
Fig. 2 Graph showing development of PCO depending upon the type of intraocular lens (IOL) implanted. The stacked column graphs demonstrate that visually significant PCO is a cause of concern with implantation of a wide range of IOLs in children less than 1 year of age
determine the complication rates and performance of various IOL types in infants undergoing cataract surgery for congenital cataracts. We hypothesized that the infants may have lesser complications amongst the hydrophobic acrylic IOL group, as is evident in adults. However, our results suggest similar or slightly higher rates of complications amongst PMMA IOLs as compared to hydrophobic IOLs. Cataract surgery with primary IOL implantation in infancy is often complicated by development of VAO, secondary to PCO or pupillary membranes [1, 4, 5, 13–17, 20, 21]. Development of PCO has always been a major challenge, with high incidence rates in studies performed in young children. In the present study, overall rate of VAO due to PCO or pupillary membrane formation in both groups together was 31.86 % (36 of 113 eyes). Fewer patients with hydrophobic acrylic IOLs
Graefes Arch Clin Exp Ophthalmol Table 3 Incidence of complications in infants undergoing cataract surgery with intraocular lens implantation in either group
Table 4 Additional surgical procedure for management of postoperative complications in either group
Complications
Group A n (%)
Group B n (%)
P value*
Additional surgical procedure
Group A n (%)
Group B n (%)
P value
PCO Pupillary membrane Glaucoma Optic capture Fibrin & pigment over IOL IOL dislocation Hyphema Phthisis bulbi Endophthalmitis
11 (17.74) 5 (8.06) 4 (6.45) 2 (3.23) 1 (1.61) – – – –
17 (33.33) 3 (5.88) 3 (5.88) 2 (3.92) 4 (7.84) 1 (1.96) 1 (1.96) 1 (1.96) 1 (1.96)
0.09† 0.472 0.608 0.614 0.127 – – – –
Membranectomy Pupilloplasty Piggyback IOL implantation Re-fixation of IOL
11 (17.74) 2 (3.23) –
13 (25.49) 3 (5.88) 1 (1.96) 1 (1.96)
0.442* 0.407† – –
PCO posterior capsular opacification; IOL intraocular lens * †
Fisher’s exact probability test Chi-Square test with Yates correction
showed development of PCO, but this was not statistically significant (p=0.09). However, the most striking difference was that PCO developed earlier in children with PMMA IOLs (approximately 6 months) than in those with hydrophobic acrylic IOLs (approximately 8 months). Early development of PCO in children with PMMA IOLs despite PPC and AV in the critical period of visual development is undesirable. Higher postoperative inflammation is the corner-stone of development of PCO in young children [13–15, 17]. Larger incision size with PMMA IOLs may be arguably responsible for higher PCO rates discernible in adults. However in younger children, the generalized heightened immune response may not make this difference discernible. Routine use of PPC along with anterior vitrectomy reduces postoperative PCO regardless of the implanted IOL type [15, 16, 24]. InFig. 3 Survival curve for infants who required additional surgical interventions following cataract surgery in either group. The LogRank statistic is 1.465 and p= 0.226
* †
Chi-Square test with Yates correction Fisher’s exact probability test
the-bag implantation of IOL is important to ensure lesser incidence of postoperative VAO [20]. Combination of these factors may be responsible for lack of observable differences between the two IOL types in infants as compared to adults, provided IOL is implanted in the capsular bag. Glaucoma in pseudophakic infants has been a major concern, as reported previously [11]. A total of seven out of 113 eyes (6.19 %) developed glaucoma in the present series. The incidence of glaucoma in our series may be regarded similar to previous studies in children less than 1 year of age [1, 11, 13, 25]. In our study population, there were no differences in the incidence of postoperative glaucoma between the two groups. This matches with previous studies indicating that the IOL material may not be associated with increased risk of glaucoma [1, 17]. Implantation of IOL in the sulcus may increase chances of postoperative glaucoma in these children [1, 11, 13]. There was no difference in the rates of additional surgical interventions in either group for clearing the visual axis. A total of 31 of 113 eyes (27.43 %) required postoperative interventions for various indications (Table 3). Patients of
Graefes Arch Clin Exp Ophthalmol
group B underwent surgeries earlier due to faster development of VAO. No surgical difficulties were experienced while reoperating a patient with PMMA IOL versus hydrophobic acrylic IOL. This is in sync with studies performed in older children by Wilson et al. [20], Küchle et al. [21], and Rowe et al. [17] that show similar risks for capsulotomy with either IOL group. In the present study, in order to maintain comparability between the two groups, children with only congenital cataracts were included. Children with traumatic cataracts may be predisposed to higher inflammation [14, 26], and bias may result due to surgeons preferring to implant PMMA IOLs in such difficult cases. Recognizing the limitations of various statistical tests, both χ2 test and survival analysis were performed in our study to compare the two groups and ensure adjustment for potential confounding factors [27]. The choice of IOL in our study was based on the knowledge of biocompatibility profiles and rates of PCO development of various IOLs currently available. All the IOLs used in the study have a biconvex design, but with variable haptic angulation (Table 1). Presently, PMMA IOLs have been shown to have comparable or better uveal and capsular compatibility compared to hydrophobic IOLs [28]. However, compared to PMMA IOLs, hydrophobic IOLs are known to have lesser rates of development of PCO [18, 19, 29]. This could be attributed to smaller incision size required for hydrophobic acrylic IOLs since they are foldable. Other reasons may include structural modifications like sharp square-edge design in hydrophobic acrylic lenses that may mechanically prevent lens epithelial cell (LEC) proliferation. Migration of LECs may be facilitated by the round-edge design of the PMMA IOLs. Hydrophobic acrylic material is known to bind strongly to collagen, preventing PCO as per the ‘no space, no cells’ theory. Hydrophilic IOLs are not preferred in children, due to higher rates of PCO attributed to higher water content and non-favorable biocompatibility profile. Hydrophilic IOLs also exert higher attraction forces on the LECs promoting PCO [28]. Previous studies in older children include very few infants, thereby making detailed analysis difficult. In the series comparing the two IOL types by Rowe et al. [17], only 13 infants were included in the trial. In the study by Lundvall et al. [1] including 31 eyes of 28 children, results comparing the two IOL types were not elucidated. Küchle et al. [21] studied children less than 17 years of age but included very few infants, which did not permit analysis of complication rates between the two IOL types. A review by Fan et al. [4] also suggests the need for such a study in children less than 1 year of age. Paucity of literature explaining the differences in complications between the two IOL types in infants may lead to practical difficulty in choosing the type of IOL. This is especially true in patients with financial constraints, where hydrophobic acrylic IOLs may not be a preferred choice.
Conclusions of the present study are important, more so for financially constrained populations where PMMA IOLs may have to be implanted. Comparable complication rates with both the IOL groups shown in the present study may provide a rationale for pediatric cataract surgeons to use PMMA IOL in resource-strained countries. This may better enable them to meet the challenges of cataract blindness in the developing world. However, hydrophobic acrylic IOL remains our first preference in infants undergoing cataract surgery. The trend for lower PCO rates with hydrophobic acrylic IOL, as well as the delay in PCO formation, encourages the need for more research in this area. Continued efforts to lower the PCO rates with further improvements in IOL designs and materials are required to combat this problem in young children. Prospective cohort studies may also add more information in this regard. Acknowledgments There are no financial interest(s) to disclose. No funding was received to carry out the study. Competing interests None of the authors have any proprietary/ financial or non-financial competing interest to disclose. Financial disclosures The author/(s) do not have any financial or proprietary interests/affiliations or arrangements. Conflict of interest No conflict of interests exists for any author.
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