Management of cataract in a visually immature child poses many challenges to the ophthalmologist. The need for early intervention is well established to prevent visual deprivation amblyopia.1 Introduction of new microsurgical techniques, instrumentation and high molecular weight viscoelastics have enabled surgeons to remove cataracts safely at an early age. In the management of surgical aphakia, which can be as amblyogenic as the cataract itself, the various options available include spectacles,234 contact lenses56 and recently, primary implantation of intraocular lenses (IOLs).789
In recent years primary IOL implantation is fast becoming the preferred modality of treatment for most children older than two years of age. It has been extensively used with favorable results in children older than two years.78910 In contrast, IOL implantation as a modality of aphakic correction in an infantile eye is debatable. Prime among the problems of primary IOL implantation in infants include difficulty in selecting the appropriate diopteric power of the IOL. In addition, the small dimension of the infant eye with a small capsular bag,1112 decreased scleral rigidity and increased tissue reactivity leading to excessive postoperative inflammation,1314 make IOL implantation technically more difficult in these patients.
There is growing evidence in the literature to support the use of IOLs as a primary modality for correction of aphakia after cataract surgery in children less than two years.11131516 The aim of the present study was to determine the outcome of primary IOL implantation following cataract surgery in children less than two years of age.
Materials and Methods
This prospective study was conducted in a tertiary eye care center in North India. We included 45 eyes of 27 consecutive children with congenital / developmental cataract, who were referred to the lens clinic between January 1997 and December 2001. The inclusion criteria were:
- Children aged less than two years, with developmental cataract, no history of trauma, no evidence of any systemic disease and no associated ocular abnormality such as aniridia, microcornea, microphthlamia, glaucoma or any corneal abnormality.
- Eyes with axial length more than 17.50 mm.
- Children completing a minimum of one year postoperative follow-up
Detailed history was obtained from the parents of each child. All children underwent complete ocular evaluation and wherever necessary, examination under anesthesia (EUA) was performed. Light fixation was recorded in each child. Pupillary reactions were carefully noted and whenever possible, slit-lamp biomicroscopy of anterior segment was done. Pupils were dilated and anatomical location of lens opacity was noted. Dilated fundus examination was performed in each child. B-scan ultrasonography was performed to rule out any posterior segment abnormality in children where media was obscured due to cataract. Axial length of each eye was measured and IOL power was calculated based on Dahan's recommendations.17 Heparin surface modified polymethylmethacrylate (HSM-PMMA Pharmacia 811C ®, Advanced Medical Optics, Inc. Santa Ana, California, USA) IOLs were used. Informed consent was obtained from the parents of all children explaining the risks of the surgical procedure and the need for repeated follow-up visits.
All children were admitted a day before surgery and topical antibiotic (ofloxacin 0.3%) was instilled into the conjunctival sac of each patient six times/day. Two hours prior to surgery, pupil was dilated with phenylephrine 2.5%, tropicamide 1% and cyclopentolate 1% applied three times at ½ hour intervals in each case. All surgical procedures were performed by the senior surgeon (JR) under general anesthesia. A scleral tunnel incision starting 1mm posterior to the limbus was followed by entry into the anterior chamber using 3.0 mm keratome. A continuous curvilinear capsulorrhexis was initiated with needle cystitome and completed with Uttrata forceps after injecting sodium hyaluronate 14 mg/ml (Healon GV ®, Advanced Medical Optics, Inc. Santa Ana, California, USA) into the anterior chamber. In children with white diffuse cataract or dense zonular cataract, anterior capsule was stained with trypan blue dye 0.6% (Bluerhex ®, Dr. Agarwal's Lab, Chennai, India) to facilitate capsulorrhexis. Multiple quadrant hydrodissection was performed by injecting balanced salt solution plus under the capsulorrhexis margin.18 Nucleus and cortical aspiration was done using automated bimanual irrigation-aspiration. Primary posterior capsulorrhexis (PPC) was initiated with needle cystitome under high magnification and completed with Uttrata forceps. Anterior vitrectomy was done using automated vitreous cutter. An attempt was made to keep the size of anterior capsulorrhexis between 4.5 to 5 mm and that of PPC between 3.5 to 4 mm. When possible, the IOL was placed in the capsular bag. The scleral tunnel incisions were closed either with a single cross or interrupted 10-0 nylon sutures. At the end of the surgical procedure, gentamicin sulphate (20 mg) and dexamethasone sodium phosphate (2 mg) were given subconjunctivally. In cases of bilateral cataract the other eye was operated within two weeks. Each eye was separately analyzed.
Postoperatively topical ofloxacin 0.3% was used four times/ day along with prednisolone acetate 1% every hourly in the first week. Topical drops were tapered over the next six-eight weeks according to ocular inflammatory response. Topical cyclopentolate 1% twice daily was used for six weeks. The children were followed up on day 1, day 2, day 5, at two weeks, four weeks, eight weeks and then at three-monthly intervals. At each follow-up visit, complete ocular examination including slit-lamp biomicroscopy was performed in cooperative children to note corneal clarity, IOL positioning and central media clarity whereas at one month and one year detailed examination under microscope including intraocular pressure (IOP) measurement was done in all children. IOP was recorded by Perkins applanation tonometer under general anesthesia. Secondary outcome measures assessed were fixation preference, steadiness, ocular alignment and retinoscopy. The cover test observations were carefully noted for fixation preference and steadiness. Any deviation of eye was recorded and thereafter dilated examination of retina was performed.
Amblyopia therapy was initiated within two weeks of surgery after retinoscopy and proper refractive correction with glasses aimed for near vision (2.5 to 3 D were added for near correction). Detailed EUA was carried out at one month, one year and whenever red glow was found dull during retinoscopy. Examination was done under the operating microscope to document posterior capsular opacification (PCO) - posterior as well as peripheral to IOL optic. IOPs were recorded and loose sutures were removed during EUA. Children who developed significant PCO were considered for surgical pars plana membranectomy.
Retinoscopy was done by a single optometrist to avoid any subjective variation. Initial retinoscopy was done two weeks after surgery and then at every follow-up visit. Spectacle prescription was modified after refraction. During follow-up, children were given 'E' chart training at home and equivalent Snellen's acuity was noted wherever possible. The data were analyzed using Chi-square test and P values < 0.05 were considered significant. Any child found to be missing at required follow-up visit was reminded and recalled by post. All children included in the analysis adhered to subsequent follow-up schedule. The missed visit findings were adjusted to the nearest scheduled follow-up.
All the data were compiled in prospective completed data forms. The study included 45 eyes of 27 children of congenital/ developmental cataract. The age ranged from three weeks to 23.5 months with a mean age of 11.45 ± 6.82 (mean ± SD) months. There were 22 males and five females. Eighteen children had bilateral disease and nine had unilateral cataract. There were 17 children aged less than or equal to 12 months whereas 10 children were more than one year of age. Zonular cataract was seen in the majority (78.3%).
On initial preoperative examination, 17 eyes had central steady and maintained fixation whereas 28 eyes could not fix at a near (33 cm) target and had wandering eye movements. Ten eyes had nystagmus. Three children with bilateral cataract and one patient with unilateral cataract had convergent strabismus. Follow-up ranged from 12 months to 48 months with mean follow-up of 18 months ± 9.1 months.
Axial length ranged from 17.50 mm to 21.93 mm with mean of 19.65 mm ± 1.03 mm. Out of 28 eyes of 17 children, less than one year of age, the mean axial length was 19.36 mm ± 0.88 mm. The mean axial length of 17 eyes of 10 children older than one year was 19.86 mm ± 1.06 mm. The difference was statistically nonsignificant. The IOL power ranged from 22.0 diopter (D) to 27.0D with mean value of 23.95 ± 0.87 D.
The mean postoperative hypermetropia at one week in children less than one year was 6.60D ± 2.64D whereas in children between one to two years it was 4.78D ± 1.93D. At one year, hypermetropia reduced to 3.03D ± 2.53D and 2.56D ± 1.5D in children less than one year and children between one to two years respectively [Fig. 1].
During follow-up, opacification of the anterior and posterior capsule peripheral to IOL optic was seen in all cases [Fig. 2], but re-opacification of central visual axis (visually significant PCO) was found only in six eyes (13.3%). The time interval between the primary surgery and development of significant PCO ranged from eight months to 29 months with mean of 12.67 ± 8.18 months. Out of six eyes that required additional surgical intervention for significant PCO, four eyes belonged to children younger than one year at the time of primary surgery.
Four eyes (8.9%) had significant anterior chamber reaction with fibrin membrane formation over IOL surface in the early postoperative period but all of them resolved with frequent topical steroid application. Eight eyes had deposits over the IOL surface but none was visually significant. Significant posterior synechiae due to irido-capsular adhesion was seen in seven eyes (15.6%) during follow-up [Fig. 3]. All these seven eyes had difficulty in pupillary dilatation during follow-up and surgical release of synechiae was performed. Five out of these seven eyes also had significant PCO. Posterior synechiae were released during surgical membranectomy and anterior vitrectomy in these five eyes. In the remaining two eyes surgical release of synechiae was performed. Two of the eyes had pupillary capture of IOL (one eye only an edge and other complete optic capture) but their visual axis was clear [Fig. 4].
During follow-up, seven children (12 eyes) cooperated for 'E' chart or Snellen's acuity evaluations. Seven of these 12 eyes (58.3%) had 20/40 or better visual acuity. No postoperative retinal complications or IOL dislocation was seen during the follow-up period. IOP recorded during follow-up was normal in all the eyes.
It is now well established that the critical period of surgery for visually significant unilateral congenital cataract is from birth to six weeks of age, while in bilateral dense cataract, permanent sensory deprivation can occur if the surgery is delayed beyond three-four months of age.19 In children less than two years, the axial length and keratomety change rapidly in contrast to those more than two years old, where these changes are slower. Therefore it has been found practical to rely on the axial length alone when the IOL dioptric power is chosen for infants.17 A large myopic shift is to be expected and Dahan et al.17 recommend undercorrecting these children with IOLs, so that they can grow into emmetropia/mild myopia in adult life. Our study showed no major refractive surprises while adopting this strategy for IOL power calculation and the recorded hyperopia at one year was amenable to occlusion treatment. It is also likely that the children would be emmetropic or slightly myopic by the time they would be school going, which is the desirable outcome we aimed for. Determining the appropriate IOL power for an infant eye poses a unique challenge. Gordon et al. found that major changes in axial length occur in the first two years of life.12 This makes IOL implantation in these infants more unpredictable and significant under-correction must be done to achieve a near normal refractive status in adult life. The issues to be considered are increase in the axial length and refractive change in the developing eye and special consideration has to be given to the reliability of IOL formulae in predicting postoperative refraction. Griener et al. reported a reduction in axial growth in infantile eyes following IOL implantation and concluded that this probably reduces the magnitude of the myopic shift in these eyes.20 O'Keefe et al. reported a mean myopic shift of 6.0 D after a mean follow-up of 41 months.15 In our series the axial length varied from 17.50 mm to 21.93 mm with a mean of 19.65 mm ± 1.03 mm. The major drawback of under-correcting an infant eye is that the eye becomes hypermetropic and needs repeated spectacle correction.
When choosing an IOL for implantation in very young infants special consideration must be given to the small size of the eye and selection of a biomaterial that will be compatible with the eye for a lifetime. Knight-Nanan et al. implanted IOLs in seven eyes of congenital cataract aged between one to 22 months with favorable outcome.9 The increased tissue reactivity in small children predisposes them to the risk of severe postoperative inflammation but there is no large-scale study to pinpoint the appropriate IOL material for these infants. Only four eyes in our series had significant fibrinous reaction, all of which resolved with frequent topical steroid instillation. Though recent evidence supports the use of acrylic IOLs in children,2122 economic consideration in the developing world preclude their use in all children. However, Heparin surface modified PMMA IOL showed good results in our study and may be considered a viable alternative.
The surgical approach to cataract extraction and IOL implantation in younger children requires careful consideration of posterior capsule management. PCO is very common after cataract extraction in children, which can present an amblyogenic hazard. Strategies to maintain a clear visual axis are therefore necessary to achieve visual rehabilitation in such cases. Trivedi et al. reported visual axis opacification with AcrySof IOL in 37.9% of children less than one year of age even though a PPC with anterior vitrectomy had been performed.23 Vasavada et al. found that the anterior vitreous face is more reactive in infants and can act as a scaffold not only for lens epithelial cell proliferation but also pigment epithelial cells, fibrinous exudates and cells that result from the breakdown of the blood aqueous barrier.24 In their series, opacification of the visual axis was found in 62.5% of cases where anterior vitrectomy was not performed along with PPC, whereas PPC coupled with anterior vitrectomy ensured that no eye had PCO. In our series, we noted re-opacification of the visual axis in 13.3% of the eyes despite PPC and anterior vitrectomy. Since we were adopting the anterior route for posterior capsulorrhexis and that too prior to IOL implantation, we chose to do it with a manual method compared to vitrector because PPC done manually has greater resistance to a radial tear as compared to vitrector during IOL insertion.
The final goal of infantile cataract surgery is successful visual rehabilitation. Knight-Nanan et al. found that all the seven eyes of congenital cataract operated between one and 22 months of age had central steady and maintained fixation postoperatively.9 Hutchinson et al. noticed central steady and maintained fixation or better vision in 49.5% of eyes in children less than 24 months where cataract extraction with primary IOL implantation was done.11 In the present series, good visual outcome was achieved with primary IOL implantation in all but three cases.
Carefully and meticulously performed primary IOL implantation appears to be a safe and effective method of aphakic correction in children younger than two years of age. PPC and anterior vitrectomy reduces the rate of secondary opacification of the visual axis in a pseudophakic eye. We report on short-term results of infantile cataract surgery with IOL implantation. While long-term follow-up of these infants is required for the evaluation of the final visual outcome after primary IOL implantation, glaucoma and PCO, the present level of microsurgical techniques does appear to lay at rest some of the earlier concerns regarding IOL implantation in these children.
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Conflict of Interest:
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