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Keywords:

  • bilateral congenital cataract;
  • postoperative complication;
  • secondary intraocular lens implantation;
  • visual acuity

Abstract.

  1. Top of page
  2. Abstract.
  3. Patients and Methods
  4. Results
  5. Discussion
  6. References

Purpose:  To evaluate the long-term visual outcome after early surgery of bilateral dense congenital cataracts, aphakic correction with glasses and secondary intraocular lens (IOL) implantation around 2 years of age.

Methods:  The medical records of paediatric patients who underwent cataract extraction, aphakic correction and secondary IOL implantation from 1993 to 2004 at Seoul National University Children’s Hospital were reviewed retrospectively. Age at secondary IOL implantation, axial length (AL), best corrected visual acuity (BCVA), refractive error, ocular alignment, stereopsis, and postoperative ocular complications were recorded.

Results:  Thirty-seven paediatric bilateral pseudophakic patients were identified with a mean follow-up period of 81.4 months. Best corrected visual acuity of 20/40 or better were attained in 44.0% of eyes, and the median BCVA was 20/50. Preoperative factors associated with poor visual prognosis included cataract surgery after 8 weeks of age, interocular AL difference of 0.5 mm or more, and glaucoma. Amblyopic eyes showed more myopic change compared to fellow eyes. Good or moderate binocular function was achieved in 18.9% of all patients. Incidences of strabismus, glaucoma, posterior capsular opacity formation were 46.0%, 32.4% and 4.0%, respectively.

Conclusion:  Good postoperative BCVA and binocular function were achieved in most healthy children with bilateral dense congenital cataract and no posterior segment pathology. Early cataract surgery, aphakic correction with glasses and secondary IOL implantation around 2 years of age appears to be appropriate methods.

Visual outcomes following congenital cataract surgery have improved because of the better understanding of the sensitive periods for the development and reversal of amblyopia, the timing of cataract removal, and improved surgical techniques (Ledoux et al. 2007). Most paediatric ophthalmologists agree that intraocular lens (IOL) implantation is the appropriate treatment of aphakic rehabilitation in paediatric cataract surgery (Bartholomew et al. 2003). Primary IOL implantation has become the preferred approach in children above 2 years, but IOL implantation in children under 2 years remains controversial as these eyes are more susceptible to intense posterior capsular opacification (PCO) and excessive uveal inflammations (Basti et al. 1996; Wilson 1996). Primary IOL implantation for the treatment of congenital cataracts in patients younger than 1 year of age has been carried out in some cases. Although there is huge debate about the timing of IOL implantation, primary aphakia, aphakic correction with glasses, and secondary IOL implantation around 2 years of age can be the better method to prevent the complications which are mentioned earlier (Ahmadieh & Javadi 2001; Bartholomew et al. 2003). Intraocular lens implantation after 3–4-year-old can decrease the efficiency of aphakic rehabilitation. In previous studies, there have been few reports regarding children who have undergone secondary IOL implantation around 2 years of age for the management of bilateral congenital cataract. Previous articles have reported the surgical results of bilateral congenital cataract in small sample sizes with short lengths of follow-up. The aim of this study was to investigate the long-term clinical results of early cataract surgery, aphakic correction with glasses, and secondary IOL implantation around 2-year-old for the management of bilateral dense congenital cataract.

Patients and Methods

  1. Top of page
  2. Abstract.
  3. Patients and Methods
  4. Results
  5. Discussion
  6. References

This was a retrospective study of children who were diagnosed as bilateral congenital cataract at our department between 1993 and 2004. After obtaining institutional review board approval, a medical record review was undertaken. Congenital cataract was defined when the patients younger than 6 months had cataract. Patients who had a co-existing organic ocular defects, retinopathy of prematurity, posterior-type persistent hyperplastic primary vitreous were excluded. Patients with Down syndrome or systemic diseases able to influence learning ability were also excluded. The red reflex was poor in both eyes of all patients because the cataracts were dense. All children had previously undergone simultaneous irrigation and aspiration (I&A) of the lens, posterior capsulectomy and anterior vitrectomy in both eyes within 2 weeks after the diagnosis of congenital cataract. Around 2 years of age, these patients were operated for secondary IOL implantations of both eyes in separate surgeries. Preoperative slit lamp biomicroscopy, fundus examination and B-scan ultrasonography were performed in all children under sedation with oral chloral hydrate. Follow-up examinations in uncooperative children were also performed under sedation. Cooperative children were examined without sedation in follow-up. Cataracts were categorized to the type of opacity; total, nuclear and posterior polar. Intraocular lens power was calculated with the SRK-II formula based on axial length (AL) and keratometry readings. The target IOL power was selected after taking into consideration the predicted future growth of the eye and the consequent myopic shift. Target IOL power in children around 2 years of age was +1.00∼+4.00 diopters (D). Patients who showed an interocular AL difference of 0.5 mm or more were classified into the ‘different’ AL group and those showing <0.5 mm difference into ‘similar’ AL group, respectively.

All surgeries were performed by one experienced surgeon (Y.S. Yu). Under general anaesthesia, mechanical anterior capsulorhexis, I&A of lens, posterior capsulectomy, and anterior vitrectomy were performed using vitrector. Aphakic correction with glasses were started 1 week after surgery. During follow-up, the patients who showed amblyopia received occlusion therapy. Secondary IOL implantations were performed through a 6 -mm sized scleral tunnel incision 2 mm from the superior limbus. One piece polymethylmethacrylate IOL were used in all surgeries. The IOL was inserted in the capsular bag or fixated in the ciliary sulcus. When inserting in the capsular bag, adhesion between the anterior and posterior capsule was dissected with microvitreoretinal blade before IOL implantation. If posterior synechiae or reproliferated lens material were found, all were removed before IOL implantation. In all cases, sodium hyaluronate 1.4% (Healon GV; AMO Inc., Santa Anc, CA, USA) was used and sclerotomy sites or scleral tunnel incisions were closed with interrupted 8-0 polyglactin sutures.

During regular follow-up after secondary IOL implantation, manifest or cycloplegic refraction, measurement of intraocular pressure (IOP) with pneumatic tonometer, strabismus examination with Krimsky test or alternative cover test were performed. Visual acuities were measured after 4 years of age using the Snellen chart. Until 3–4-year-old, the patients were examined every 4 months, Until 7–8-year-old, the patients were examined every 6 months. After 9-year-old, yearly check-up was carried out. Patients who showed a visual acuity (VA) difference of two or more Snellen lines between the two eyes were grouped as amblyopic patients. Ocular deviations were measured in prism diopters (PD). Children with a deviation equal to or larger than 10 PD were considered to have strabismus and some underwent corrective surgery. Sensory fusion was assessed using the Worth 4-dot test. Fusion was measured at both near (1/3 m) and at distance (6 m). Stereoacuity was assessed by means of the Titmus stereo test. Near fusion and Titmus stereo test was performed with the children wearing their near glasses or adding +3.0 D trial lenses. Binocular function was graded as ‘good’ if measured stereo acuity was 100 seconds of arc or better and as ‘moderate’ if measured stereo acuity was between 100 and 200 seconds and if there was fusion of the Worth 4-dot test at both distance and near. The eyes in which the IOP was higher than 25 mmHg were defined as having glaucoma and were treated either medically or surgically.

Multivariate analysis was used to evaluate the factors that influenced final best corrected visual acuity (BCVA). p-Value of <0.05 was considered statistically significant.

Results

  1. Top of page
  2. Abstract.
  3. Patients and Methods
  4. Results
  5. Discussion
  6. References

From 1993 to 2004, 54 patients were diagnosed with bilateral congenital cataract and underwent surgery. Seventy-four eyes of 37 patients were included in our study. Mean follow-up period was 81.4 ± 21.3 months (range 36–144 months). The mean age of all patients at final follow-up was 7.8 years (range 4–10 years). Details of preoperative patient demographics are listed in Table 1.

Table 1.   Patients demographics.
Number of eyes/patients74/37
Sex
 Male21 (57%)
 Female16 (43%)
Cause
 Idiopathic22 (59%)
 Hereditary15 (41%)
Opacity type
 Total38 (51%)
 Nuclear32 (44%)
 Posterior subcapsular4 (5%)

Mean age at I&A of lens was 13.6 ± 5.3 weeks (range 4–26 weeks). Seven patients underwent cataract surgery before 8 weeks from birth. There were no children who had strabismus before cataract surgery. The postoperative refractive error at 3 months after I&A of lens is shown in Table 2. All children showed good compliance with aphakic glasses. Two patients had visual axis opacification (VAO) at 5 and 20 months after cataract surgery, respectively, and underwent reoperation. There were no incidences of glaucoma or strabismus before secondary IOL implantation.

Table 2.   Postoperative refraction error at postoperative 3 months of irrigation and aspiration (I&A) of lens, after posterior chamber intraocular lens (PC-IOL) insertion and at final follow-up in bilateral congenital cataract patients.
  1. SE = spherical equivalent; D = diopters; AST = amount of astigmatism.

Post I&A (postoperative 3 months)SE: +15.8 D (+11.0∼+20.5 D)
AST: 0.4 D (0∼2.5 D)
After secondary PC-IOL insertion (postoperative 3 months)SE: +1.6 D (+5.8∼−4.0 D)
AST: 0.7 D (0∼3.0 D)
Final follow-upSE: −1.7 D (+4.5∼−9.5 D)
AST: 1.1 D (0∼5.0 D)

Mean age at secondary IOL implantation was 25.9 ± 3.9 months (range 17–30 months). Mean AL at secondary IOL implantation was 20.88 ± 1.59 mm (range 17.47–24.68 mm). The number of patients in the ‘different AL’ group was 11. The ‘different AL’ group showed a longer AL than the ‘similar AL group’, which was statistically significant (different AL: 21.35 ± 1.92 mm, similar AL: 20.70 ± 1.40 mm, p = 0.026, Mann–Whitney test). The numbers of eyes which were fixated to the ciliary sulcus or implanted in the capsular bag were 62 and 12, respectively. The postoperative refractive error at 3 months after posterior chamber intraocular lens (PC-IOL) insertion is shown in Table 2. Table 3 shows the difference in target and postoperative refraction at 3 month after PC-IOL insertion. The difference between the target and postoperative refraction was <2 D in most eyes (52 eyes, 71%). Myopic and hyperopic shift were present in 54 eyes (73%) and in 20 eyes (27%), respectively.

Table 3.   Difference in target refraction and postoperative refraction at postoperative 3 months of posterior chamber intraocular lens (PC-IOL) insertion in bilateral congenital cataract patients.
Target refraction – post op 3-months refraction (diopters)Number of eyes%
  1. D = diopters.

D < −2.011
−2.0 ≤ D < −1.057
−1.0 ≤ D < 1.03345
1.0 ≤ D < 2.01419
2.0 ≤ D < 3.01115
3.0 ≤ D1013
Total74100

Seventeen patients (46%) showed strabismus at final follow-up. Exotropia (nine patients, 24%) was more common than esotropia (seven patients, 19%). Dissociated vertical deviation (DVD) was demonstrated in one patient (3%). The mean prism deviation was 30 PD in exotropia and 35 PD in esotropia. Five patients underwent strabismus surgery for exotropia, three for esotropia, and one for DVD, respectively. Surgical intervention was successful in 80% of strabismus patients, with no evidence of strabismus recurrence at final follow-up. Visual axis opacification developed in both eyes of one patient at 52 months after secondary IOL implantation. Glaucoma showed the highest incidence among the postoperative complications, with 24 eyes (32%) showing IOP elevation. The glaucoma rate in the ‘different’ and ‘similar’ AL group was 36% and 31%, respectively. During the period between I&A of lens and secondary IOL implantation, there were no incidences of glaucoma.

Glaucoma developed at mean 62 months (range 24–102 months) after I&A of lens, and eight patients (66%) have glaucoma in 4–6 years after I&A. All glaucoma incidences were in both eyes of a single patient. Sixteen eyes maintained stable IOP with the use of a single anti-glaucoma medication, Cosopt® (MSD, Whitehouse Station, NJ, USA), and six eyes, with the use of two or more IOP lowering agents (Cosopt®, Alphagan® (Allergan, Irvine, USA) and Xalatan® (Pfizer, New York, NY, USA)). One patient received Ahmed operations in both eyes. Band keratopathy and scleromalacia occurred in one eye, respectively.

Final BCVA are summarized in Table 4. Median BCVA at final follow-up was 20/50. The mean BCVA at final follow-up was better in the posterior polar type opacity compared to others, but there were no significant differences according to the type of opacities (p = 0.432, multivariate analysis). Thirteen patients (35%) showed a BCVA of 20/40 or better in both eyes. Twelve patients (32%) showed a BCVA difference of two or more Snellen lines between the two eyes. The mean final BCVA in patients who had undergone cataract surgery before 8 weeks from birth was 0.36 ± 0.23 logMAR (Minimal angle of resolution) and these patients demonstrated a significantly better mean BCVA (0.51 ± 0.41, logMAR) compared to that of patients who received surgery after 8 weeks (p = 0.046). The incidence of patients showing a difference of two or more Snellen line between both eyes was 20% in the ‘different AL’ group and 33.3% in the ‘similar AL’ group, respectively. The mean BCVA in the ‘similar AL’ group was better significantly than that in the ‘different AL’ group (logMAR – 0.44 ± 0.35, 0.61 ± 0.47, p = 0.044). The mean final BCVA in strabismus patients was not statistically different from that of orthotropic patients (strabismus/orthotropia: 0.47 ± 0.41/0.42 ± 0.25 (logMAR), p = 0.162). The amblyopia rate in strabismus patients was higher than that in orthotropic patients (33% versus 27%). Glaucoma patients had significantly worse visual prognosis than normal IOP patients [BCVA (logMAR): high IOP – 0.59 ± 0.49, normal IOP – 0.43 ± 0.32, p = 0.036]. Overall results are shown in Table 5.

Table 4.   Best corrected visual acuities (BCVA) at final follow-up.
BCVA at final follow-upEyes%
  1. VA = visual acuity.

20/20 ≤ VA33
20/25 ≤ VA < 20/20710
20/40 ≤ VA < 20/252331
20/100 ≤ VA < 20/402534
20/200 ≤ VA < 20/1001115
VA < 20/20057
Total74100
Table 5.   Multivariate analysis of the best corrected visual acuities (BCVA) according to clinical features at final follow-up.
 BCVA (logMAR)p-Value
  1. IOP = intraocular pressure.

  2. * Statistically significant (multivariate analysis).

Time of cataract surgery
 Before 8 weeks0.36 ± 0.230.046*
 After 8 weeks0.51 ± 0.41
Lens opacity type
 Total0.58 ± 0.490.432
 Nuclear0.39 ± 0.22
 Posterior polar0.34 ± 0.12
Axial length (AL)
 Similar AL group0.44 ± 0.350.044*
 Different AL group0.61 ± 0.47
Strabismus
 Orthotropia0.42 ± 0.250.162
 Heterotropia0.47 ± 0.41
Glaucoma
 Normal IOP0.43 ± 0.320.036*
 High IOP0.59 ± 0.49

The refractive error at final follow-up is shown in Table 2. The mean change in myopic regression at final follow-up after secondary IOL implantation in all patients was −3.3 ± 2.4 D. The mean change in myopic regression in patients 8 years or older was −5.5 ± 2.7 D in eyes whose VA were 20/40 or better and −5.7 ± 4.3 D in eyes whose VA were <20/40 (p = 0.064, independent t-test). The mean change in myopic regression in amblyopia patients 8 years or older was −5.8 ± 3.1 D in the fellow eyes and −7.8 ± 3.4 D in amblyopic eyes (p = 0.001, independent t-test). Figure 1 shows the changes in mean spherical equivalent (SE) from secondary IOL implantation to final follow-up in the groups of BCVA of 20/40 or better and <20/40. Figure 2 shows the changes in SE of the amblyopic and fellow eyes in patients with amblyopia.

image

Figure 1.  Change in mean spherical equivalent from secondary intraocular lens implantation to final follow-up according to best corrected visual acuities.

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image

Figure 2.  Change in mean spherical equivalent from secondary intraocular lens implantation to final follow-up in amblyopic and fellow eyes.

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Two patients (5%) showed good binocular function. Of the patients whose BCVA of both eyes were 20/40 or better, 15% achieved stereopsis of 100 seconds of arc or less. Seven patients (19%) showed stereopsis ranging from 200 seconds of arc to 100 seconds of arc. One patient with moderate stereopsis at final follow-up had undergone strabismus surgery for exotropia at 24 months after cataract extraction.

Discussion

  1. Top of page
  2. Abstract.
  3. Patients and Methods
  4. Results
  5. Discussion
  6. References

The BCVA at final follow-up in this study corresponds with the results of several studies on congenital and infantile bilateral cataracts performed during the past 20 years. They report BCVA of 20/40 or better for over 40% of subjects mostly (Christensen et al. 1992; Petersen & Robb 1992; Bradford et al. 1994; Arné et al. 1998). Results from recent studies regarding primary IOL implantation in bilateral congenital cataract show that the median final BCVA achieved were 20/63, 20/60, 6/18 (Chak et al. 2006; Gouws et al. 2006; Lundvall & Zetterström 2006). The median BCVA in this study was 20/50 and 10 eyes (14%) attained a BCVA of 20/25 or better. Through these results, we may assume that primary I&A of lens, aphakic glasses, and secondary IOL implantation around 2 years of age may show better visual prognosis than early primary IOL implantation. Our previous study concerning secondary IOL implantation at various ages older than 2 years showed a median BCVA of 20/66 (Kim et al. 2008). It is thought that early visual rehabilitation using IOL around 2 years will increase visual prognosis. Because the long-term visual outcome may be predicted at 7 years of age, the subjects in our study (mean age: 8-year-old) are proper for evaluation of long-term visual outcome (Jonsson et al. 2009).

The critical period for surgical treatment of congenital cataracts within the first 8 weeks of life has been proposed in several studies (Fellows et al. 1981; Gelbart et al. 1982; Kugelberg 1992). The superior BCVA in patients who underwent cataract surgery before 8 weeks is coincident with the concept of this critical period, although there is debate about critical period. As lens opacities in all patients were visually significant, the BCVA would be expected to be irrespective of the opacity type. The cause of the difference in BCVA between the ‘different’ and ‘similar AL’ group will be because of the difference of stimulus deprivation between both eyes. Because more deprivation effect causes longer elongation of the eye (Wiesel & Raviola 1977; Chalupa et al. 1982), the longer AL in different AL group than in similar AL group will be correlated with worse BCVA. The higher glaucoma incidence in the different AL group may be also a factor for poor visual prognosis.

Mean SE 3 months after IOL implantation showed myopic change from the estimated preoperative IOL power. These changes may be because of IOL fixation in the ciliary sulcus in most eyes. Given that secondary IOL implantation into the capsular bag is a difficult surgical technique, sulcus fixation technique should be used in most surgeries.

Myopic change in pseudophakic eyes is larger and more rapid than phakic eyes and the younger the child at the time of implantation, greater the myopic shift (Dahan & Drusedau 1997; Crouch et al. 2002) Children who underwent IOL implantation at 1–18 months showed a mean myopic change of −6.39 ± 3.68 D (Crouch et al. 2002). Our study showed a myopic change of 3.5 D. Because most eye growth occurs during the first 2 years of life, myopic change in eyes undergoing IOL implantation after 2 years is less than eyes which receive early primary IOL implantation. Also the amblyopic eye showed the more myopic change compared to the fellow eye. Several previous studies already showed that stimulus deprivation amblyopia lead to elongation of the eye (Wiesel & Raviola 1977; Chalupa et al. 1982). The elongation effect in the amblyopic eyes may bring about more myopic change.

Incidence of stratbismus was 46% in this study and exotropia was more common than esotropia. This result was similar to previous studies and our study also cannot arrive at a conclusion regarding the importance of the convergence mechanism in the type of strabismus in patients with paediatric pseudophakia (Gelbart et al. 1982; France & Frank 1984; Neely et al. 2005). Compared with the incidence of strabismus in the general population (1.3–4.5%), pseudophakic patients in this study had a higher frequency of strabismus (Neely et al. 2005).

Our study showed that 15% and 54% of the patients who achieved 20/40 or better VA in both eyes had good and moderate binocular function, respectively. Binocular vision was present in 24.3% of all patients. These results are superior to the binocular function results of Lundvall & Kugelberg (2002) (18.2%). Choung et al. (2007) and Kohnen et al. (1999) reported that 21.4% and 12.5% of unilateral congenital cataract achieved a stereopsis of 100 seconds of arc or better, respectively. As unilateral congenital cataract patients have two amblyogenic factors, pattern vision deprivation and anisometropia, bilateral congenital cataract patients are expected to show better binocular function and stereopsis (Kohnen et al. 1999). Because there are few reported results regarding stereopsis in bilateral congenital cataract patients, our results are thought to be meaningful, but further studies should be performed in the future.

Postoperative complications in congenital cataract surgery include VAO, secondary glaucoma, fibrinoid reactions, decentralization of the pupil, retinal detachment and endophthalmitis (Keech et al. 1989). Incidence of secondary glaucoma and VAO in our study was 32% and 8%, respectively. Risk factors for glaucoma after the operation of the congenital cataract are microphthalmos and early cataract surgery (Asrani et al. 2000; Byrne et al. 2000). The severe inflammatory response after congenital cataract surgery in early age can induce adhesion of the angle (Keech et al. 1989). Several authors have noted a low incidence of glaucoma in children with pseudophakic eyes, the implication being that pseudophakia in children somehow protects against glaucoma (Hiles 1984; Desai & Vasavada 1997; Asrani et al. 2000; Byrne et al. 2000; Kirwan et al. 2009). These results were explained with the theory that IOL implantation can support the structure of the trabecular meshwork and prevent toxic material of the vitreous from directly contacting the trabecular meshwork and subsequently inducing glaucoma (Catalano et al. 1991). Glaucoma incidence in our study was slightly high compared to other studies (Golub et al. 2006; Billson et al. 2007; Kirwan et al. 2009). We cannot explain theses phenomenon, but the long-term follow-up period may elevate glaucoma incidence. Because complicated surgical procedures, including IOL manipulation at an early age, and the long maintenance of the aphakic state may be causes for secondary glaucoma, primary aphakia and secondary IOL implantation around 2 years may contribute to lowering glaucoma incidence. Posterior capsulectomy and anterior vitrectomy in congenital cataract surgery remarkably lowers the incidence of PCO (Caporossi et al. 1990). Resultingly, the incidence of PCO in our study was low as expected. There were no other postoperative complications except band keratopathy and scleromalacia. But several studies concerning early primary IOL implantation demonstrated various postoperative complications (VAO, corectopia, pupillary membrane formation, retinal detachment and endophthalmitis) and required additional surgeries (Buckley et al. 1999; Autrata et al. 2005; Gouws et al. 2006; Lundvall & Zetterström 2006). The low incidence of postoperative complications found in our study compared to that in early primary IOL implantation patients appear to show the superiority of the primary aphakia, aphakic glasses, and secondary IOL implantation procedure.

Contact lenses offer several advantages over spectacles in paediatric age group, but the patients using contact lenses showed poorer compliance than patients using aphakic glasses and the parents of patients complained contact lens wearing in Korea. So, we have used aphakic glasses for visual rehabilitation. From this study, we think that wearing aphakic glasses can be good method for postoperative visual rehabilitation in bilateral congenital cataract.

In conclusion, satisfactory BCVA and binocular function were achieved in most otherwise healthy children with dense bilateral congenital cataract and no posterior segment pathology, through early cataract surgery, aphakic correction and secondary IOL implantation around 2 years of age. The occurrence of strabismus and secondary glaucoma needs to be checked during regular follow-up examinations. We believe that the long-term follow-up and large sample size of patients in our study itself carries strong significance. Moreover, early cataract surgery, aphakic glasses, and secondary IOL implantation around 2 years seems to be appropriate method in the treatment of the congenital cataracts.

References

  1. Top of page
  2. Abstract.
  3. Patients and Methods
  4. Results
  5. Discussion
  6. References