Posterior Capsular Opacification following Primary IOL Implantation in first two years of life
Supratik Bandyopadhyay, Jagat Ram, GS Brar, J Sukhija, Amod Gupta

INTRODUCTION
Management of cataract in a visually immature child poses many unique challenges to the ophthalmologist.  The need for early intervention is well established to prevent visual deprivation amblyopia.1-3 New surgical instrumentation and high quality viscoelastic have enabled surgeons to remove cataracts safely at an early age. In recent years, IOL's have been extensively used as a primary procedure after cataract extraction in children older than 2 years with favorable results.4-6 Controversy still exists regarding the advisability of implanting an IOL in an infantile eye.  IOL's provide an immediate full-time correction of an aphakic eye with optics that closely simulates that of a crystalline lens and the treatment of amblyopia becomes easier.7,8 The disadvantages of primary IOL implantation in infantile cataract include msall dimension of the infant eye, increased post operative inflammation and more importantly difficulty in selecting the appropriate dioptric power of the IOL.7 The aim of the present study was to find out the rate of PCO following primary posterior capsulotomy and anterior vitrectomy and implantation of IOL in children younger than 2 years.

MATERIAL AND METHODS
This prospective study included 45 eyes of 27 children of congenital cataract aged less than 2 years.  Patients with traumatic cataract, other ocular problem in addition to the cataract or eyes with axial length less than 17.50 mm were excluded from the study.  Details of age, sex, primary diagnosis, family history, associated systemic or ocular disorders were obtained from the parents of each child.  All children underwent complete ophthalmological examination. Visual acuity was assessed in patients who were aged more than 3 months and whether they could follow and fix at a light source kept at 33 cms was noticed.  Anatomical location of lens opacity was noted. This was followed by dilated fundus examination in each patient.  Where cataract was too dense, B-scan ultrasonography was considered to rule out any posterior segment abnormality.  Axial length of each eye was measured by a scan and IOL power was calculated based on Dahan's recommendations.9 An IOL power was selected to achieve under correction by 4-6 diopters depending upon the age of the child, in the expectation of myopic shift with age due to growth of the eye ball.10 IOL's having 12mm over all diameter with optics made up of either Polymethyl methacrylate late (PMMA) or acrylic material with PMMA haptics were selected in all patients.  All patients underwent phacoaspiration of the cataract and intra ocular lens implantation under GA.  IOL was placed in the bag or captured through the posterior capsulotomy.  At each follow-up, clarity of the visual axis, intra-ocular pressure, retinoscopy and posterior segment evaluation was carried out. Examination under anesthesia was performed at 1month, 3 months and 6 months after surgery or when poor retinoscopic glow was encountered. Sutures were removed during EUA.

RESULTS
The study included 45 eyes of 27 children of congenital cataract with age ranged from 3 weeks to 23.5 months with a mean age of 11.45+6.82 (Mean+SD) years.  There were 20 male and 7 female patients.  Type of cataract varied but zonular cataract was seen in majority (78.51%) of the eyes.  Initial subjective visual acuity assessment was not possible as patients were too young and visual acuity testing was limited to identifying fixation pattern of the cataractous eye.  Out of 45 eyes 17 eyes had central steady and maintained fixation whereas 28 eyes could not fix at a near (33cm) target and had wandering eye movements.  6 eyes with unilateral disease and 4 eyes with bilateral disease had nystagmus.  4 eyes of 2 patients with wandering eye movement had alternate convergent strabismus.

IOL power calculation was based on preoperative measurement of axial length of the cataractous eye as recommended by Dahan et al.11 Axial length ranged from 17.50 to 21.93 mm with mean of 19.65+1.03 (Mean+SD). 37 eyes received Pharmacia all PMMA IOL (811C) where as 8 eyes had foldable acrylic IOL (ACRYSOF ALCON MA 60 BM) implanted.  The IOL power that was used ranged from 22 to 25.5 D with mean value of 23.95+0.87 diopter.  28 out of 45 eyes (62.22%) had a capsular bag implantation of IOL, whereas 14 (37.78%) had an optic capture of IOL done.

During follow up re-opacification of visual axis developed in 6 eyes (13.33%).  The time interval between the primary surgery and development of re-opacification ranged from 8 months to 29 months with mean of 12.67+8.18 months.  5 out of 37 eyes (13.51%) with PMMA IOL and 1 eye with acrylic IOL (12.5%) developed visually significant PCO and required surgery (p>0.05). Twenty eight eyes had a capsular bag implantation of IOL and significant PCO occurred in 3 eyes (10.71%).  Out of 17 eyes with an optic capture of IOL, 3 eyes (17.24%) developed PCO (p>0.05).  All 6 eyes had poor retinoscopic glow due thick membrane formation behind the IOL and surgical membranectomy was done.

The mean retinoscopy at 1 weak postoperatively was 5.86+2.52, which was reduced to 4.59+2.04 at 3 months, and 2.84+2.17 at 1 year.  The mean myopic shift at 1-year follow up was 3.02+1.82D.  Follow up ranged from 12 to 48 months with mean follow up of 18 to 48+9.13 months.

Amblyopia therapy (occlusion) was given when required and compliance was excellent.  At 1 year follow up all the eyes had central steady and maintained fixation but nystagmus persisted in 3 eyes.  During follow up 7 patients (12 eyes) were old enough to cooperate in 'E' chart and all had better than 6/24 vision, out of which 6/12 or better vision was seen in 7 eyes (58.33%).  No serious postoperative complication was noted in any of the patients.  4 eyes (9.66%) had significant anterior chamber reaction with fibrin membrane formation over IOL surface but all of them resolved with frequent topical steroid application.  No postoperative retinal complication or IOL dislocation was seen during the follow up period.

DISCUSSION
Implantation of IOLs in infants and young children remains controversial.  However the result of the present study confirms the findings of few others where use of modern surgical techniques and instrumentation have made it possible to safety place on IOL in the eye of an infant.7,10-12

There are studies reporting to safety of IOL implantation in very young infants.  Sinskey and co-authors reported implanting an IOL into the cilliary sulcus of a 17 day old infant.11 Knight-Nanan and co-authors implanted IOLs in 6 eyes of congenital cataract aged between 1 to 7 months.13 Hutchinson et al reported safety of IOL implantation and normal ocular growth rates following intraocular lens implantation in the first 2 years of life.15 Implantation of IOLs in young children is becoming more and more popular worldwide and is becoming standard of care in management of congenital cataract.12

In our series the axial length varied from 17.50 to 21.93 mm with a mean of 19.65+1.03mm.  We have used recommendations of Dahan and Drusedau for calculation of IOL power depending upon the axial length.9

The surgical approach to cataract extraction and IOL implantation in younger children required careful consideration of posterior capsule management.  We have done a primary posterior capsulectomy with anterior vitrectomy in all the eyes.  Although few studies have reported absence of PCO8,15,16 in their series following the same procedure (primary posterior capsulotomy and anterior vitrectomy) we had secondary opacification of the visual axis seen in 6(14.28%) of the eyes.  Despite primary posterior capsulotomy (PPC) lens epithelial cells can grow on the anterior vitreous face which may result in secondary opacification of the visual axis.  Adequate size of PPC and sufficient anterior vitrectomy (nearly 1/3rd of anterior vitreous) is important to reduce the rate of PCO.

Gimbel proposed posterior capsulorrhexis with optic capture as an alternative method for preventing PCO.  They proposed apposition of anterior and posterior capsular leaflets prevents lens epithelial cell migration thus reducing PCO.17 We found no statistically significant difference in PCO rate in eyes having in the bag fixation or optic capture of IOL when primary posterior capsulotomy and anterior vitrectomy was done.

There are still many dark zones which needs to be explored regarding use of IOLs in children younger than 2 years.  Success is difficult to ascertain in terms of vision.  Although the retinoscopy data from our study shows every possibility of emmetropisation in adulthood long term follow up of these eyes is required to confirm our result.

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Address for Correspondence
Dr. Supratik Bandyopadhyay, Deptt. of Ophthalmology,
PGIMER, Chandigarh