- Email: [email protected]
Duration of form deprivation and visual outcome in infants with bilateral congenital cataracts
Duration of form deprivation and visual outcome in infants with bilateral congenital cataracts Saurabh Jain, MS, FRCOphth, Jane Ashworth, PhD, FRCOphth, Susmito Biswas, FRCOphth, and I. Chris Lloyd, FRCS, FRCOphth PURPOSE
To determine optimal timing for operating on dense bilateral congenital cataracts and to define latent periods for binocular visual deprivation.
METHODS
A retrospective review of the records of children that had undergone bilateral lensectomies at our center. Infants with bilateral, dense, visually significant cataracts who had undergone lensectomy within the first year of life from 1992 to 2000 were identified. Children with other ocular anomalies, neurological and systemic disorders, intraocular lenses, or with fewer than 5 years of follow-up were excluded.
RESULTS
A total of 13 children were identified. The mean age at surgery was 8.7 weeks (range, 3–20; SD 5.3). The mean interval between surgeries of the 2 eyes was 3.8 days (range 0-7; SD 3.2). The median final visual acuity at 5 years of age was 6/18 (range, 6/5–6/36). There was a moderate correlation between (log) visual outcome and time to surgery (r 5 0.59, p 5 0.002, r2 5 0.35).
CONCLUSIONS
Visual acuity after surgery for bilateral congenital cataracts appears to decline exponentially with duration of visual deprivation. ( J AAPOS 2010;14:31-34)
V
isual outcomes after surgery for bilateral congenital cataracts have improved with advances in surgical techniques and better understanding of postoperative refractive correction and amblyopia treatment. The optimum timing for surgery, however, remains unclear. Unilateral visual deprivation in neonates during a ‘‘subcortical,’’ or latent, period for visual development, postulated to last for approximately 6 weeks of age, does not appear to affect eventual visual outcome.1 This latent period is followed by a sensitive period of cortical plasticity, which lasts approximately 7 to 8 years.2 During this period, episodes of even minor visual impairment can affect final visual function, although the effect of any adverse event becomes less marked with increasing maturity. The latent period for binocular deprivation has been more difficult to determine, but it has been posited to be around 10 weeks.3 A previous study from this unit postulated that the latent period for fixation stability and binocularity may be as short as 3 weeks.4 To further explore the optimum timing for cataract surgery in infants, we retrospectively assessed
Author affiliations: The University of Manchester, Manchester Academic Health Science Centre, Manchester Royal Eye Hospital, Manchester, United Kingdom Presented at the 35th meeting of the American Academy of Pediatric Ophthalmology and Strabismus (AAPOS) at San Francisco, California, April 17-21, 2009. Submitted April 18, 2009. Revision accepted November 24, 2009. Reprint requests: Mr. Saurabh Jain, Consultant Pediatric Ophthalmologist, Department of Ophthalmology, Royal Free Hospital, London NW3 2QG, United Kingdom (email: [email protected]). Copyright Ó 2010 by the American Association for Pediatric Ophthalmology and Strabismus. 1091-8531/2010/$36.00 1 0 doi:10.1016/j.jaapos.2009.11.016
Journal of AAPOS
a cohort of children with dense bilateral congenital cataracts who had undergone bilateral lensectomies.
Methods and Materials We retrospectively identified infants with bilateral dense, visually significant congenital cataracts who had undergone lensectomy without primary lens implantation within the first year of life from 1992 to 2000. Case notes were obtained and reviewed for collection of relevant data, including age at the time of surgery for each eye, duration between surgery on the 2 eyes, any underlying ocular and/or systemic diagnosis, intraoperative complications, further surgery or laser treatment, and visual acuity after 5 years of follow-up. Children with coexistent ocular anomalies, systemic neurodevelopmental disorders that precluded accurate assessment of visual acuity, fewer than 5 years of follow-up, and poor compliance with refractive correction or subsequent amblyopia therapy (occlusion or optical penalization) were excluded from the study. Infants with significant postoperative complications that affected final visual acuity, such as endophthalmitis and retinal detachment, also were excluded. All lensectomies were performed by the use of an anterior approach via temporal and nasal 20-gauge limbal incisions. Anterior capsulotomy was performed with a cystitome and vitrector or by continous curvilinear capsulorhexis under viscoelastic. The lens was aspirated by the use of a bimanual technique with a vitrectomy cutter and infusion positioned alternately through the 20-gauge ports. All eyes underwent posterior capsulotomy and limited anterior vitrectomy.5 The anterior chamber was irrigated with balanced salt solution containing heparin at the end of the procedure to minimize the risk of postoperative fibrinous uveitis. A peripheral iridotomy was performed with the vitrector in all eyes.
31
32
Jain et al
The second eye was operated upon either at the same time or within a week of the first, ensuring that the first operated eye was kept patched in the interim period. Topical mydriatics (cyclopentolate 0.5% in infants younger than 6 months of age and 1% in older children), steroids (prednisolone phosphate 1%), and antibiotics (chloramphenicol 0.5%) were prescribed for 4 to 6 weeks postoperatively in a tapering dose on the basis of the inflammatory activity observed on slit-lamp examination. Topical atropine 1% was used only in the presence of pupillary block or posterior synechiae. All cataracts were operated upon by the authors (ICL, SB, and JLA) or by their fellows under close supervision. Residual hypermetropic refractive error was corrected by the use of either contact lenses or spectacles. Patients were closely monitored in a dedicated pediatric cataract clinic staffed by ophthalmologists, optometrists, and orthoptists. Amblyopia, identified by interocular visual acuity difference, was treated with occlusion therapy. Statistical analysis was performed by the use of SPSS version 10. (SPSS Inc, Chicago, IL) Neither time nor visual acuity was normally distributed, and both variables were log transformed for analysis with the Pearson correlation.
Volume 14 Number 1 / February 2010 Table 1. Clinical characteristics and visual outcomes in a cohort of 13 children Age at Visual outcome Time between Serial number surgery (weeks) operated eye surgeries (days) 1 2 3 4 5 6 7 8 9 10 11
Results During the study period a total of 98 eyes in 49 children had cataract surgery. Of these, 82 eyes in 41 children were left aphakic and 16 pseudophakic. Of the 41 aphakic children, 25 (61%) were excluded from analysis on account of insufficient follow-up (3), neurodevelopmental systemic disorders (5), associated ocular malformations (10), noncompliance with amblyopia therapy (2), and surgical complications affecting final visual acuity (5). The mean age at surgery of all patients operated upon for congenital cataracts in this period was 7.7 weeks. The mean age of those excluded from the cohort analysed was 7.1 weeks. Data from the remaining 26 eyes (13 patients) were tabulated and analyzed (Table 1). The overall mean age at surgery was 8.7 weeks (range, 3-20; SD 5.3) and the mean interval between surgery of the 2 eyes was 3.8 days (range 0-7, SD 3.2). Visual Acuity and Age at Surgery The median final visual acuity at 5 years of age was 6/18 (range 6/5-6/36). There was a moderate correlation between (log) visual outcome and age at surgery (r 5 0.59, p 5 0.002, r2 5 0.35). The final visual acuity achieved after bilateral congenital cataract surgery decreased exponentially with age at surgery (Figure 1), with no demonstrable break point when plotted on a logarithmic scale (Figure 2). There was also a moderate correlation between log visual acuity of the better eye at 5 years of age and the age at surgery (r 5 0.580, p 5 0.038, r2 5 0.34)
Discussion It is widely believed that early surgery leads to better visual acuity outcomes in patients with bilateral congenital cata-
12 13
8 8 5 6 16 16 4 4.5 4 4 12 12 5 4 15 15 5 6 3 4 5 6 20 20 9 10
6/9 6/18 6/9 6/24 6/19 6/19 6/6 6/9 6/5 6/5 6/12 6/12 6/15 6/19 6/24 6/18 6/9 6/18 6/9 6/9 6/9 6/9 6/36 6/18 6/36 6/36
2 6 0 5 0 2 7 0 7 7 7 0 7
racts. This early intervention has to be balanced against the risk of associated problems, particularly glaucoma and anesthetic complications.6,7 Birch and Stager8 found that surgery performed for unilateral dense congenital cataracts before 6 weeks of age minimized the effects of unilateral visual deprivation on the developing visual system.8 Bilateral visual deprivation appears to affect the visual system differently: the neurophysiological changes in this situation are not caused by unequal competition for cortical representation. Animal studies have shown that prolonged early monocular visual deprivation leads to asymmetric changes of the striate cortex ocular dominance columns and the layers of the lateral geniculate nuclei as well as complete loss of binocularity.9,10 In contrast, similar binocular deprivation has been shown to lead to symmetric loss of only a third of striate cortex neurons.10,11 This disparity in the neurophysiological changes observed in animals has made it difficult to define a latent period for binocular deprivation in children.3 Gelbart and colleagues12 reported on 24 children operated on for bilateral congenital cataracts. They noted visual acuities of 20/60 or better in all eyes undergoing surgery before 8 weeks of age and 20/200 or worse in 86% of eyes who underwent surgery thereafter. Bradford and colleagues13reviewed the medical records of 33 children with bilateral congenital cataracts: 21 underwent surgery before 8 weeks of age and the rest later in infancy. They suggested that age of surgery was not prognostically related to visual outcome. However,
Journal of AAPOS
Volume 14 Number 1 / February 2010
FIG 1. Visual acuity (at 5 years of age) exhibits an exponential decrease with increasing initial age at surgery in 13 children (26 eyes).
a significant proportion of the children had coexistent ocular disorders, and the late surgery group included infants with acquired cataracts, making their results difficult to interpret. Abadi and colleagues4 studied the effect of the duration and severity of early-onset visual deprivation on ocular alignment and stability. The study group consisted of 33 children (aged 1 week to 12.8 years) with infantile cataracts who were observed for up to 61 months to assess visual acuity and fixation stability. Of these, 5 children experienced bilateral major form deprivation and underwent surgery between 4 and 14 weeks of age. Of the 5, 2 exhibited unstable fixation before surgery after experiencing only 8 weeks of visual deprivation. All 5 exhibited postoperative fixation instability (3 manifest latent nystagmus, 1 latent nystagmus, and 1 congenital nystagmus). The authors interpreted these results as suggesting that deprivation periods as short as 3 weeks can lead to a sustained nystagmus, which is usually of the manifest latent variety.4 Lambert and colleagues3 noted a linear trend between visual outcome and age at surgery for children with bilateral visually significant congenital cataracts, although this trend failed to reach statistical significance. In a series of 43 children with 5 years of follow-up, visual acuity of 20/100 or worse occurred only in eyes undergoing surgery after 10 weeks of age. However, good visual acuity outcomes were achieved in both groups, with final visual acuity of 20/40 or better in 67% in patients who had surgery at age 10 weeks or younger and 55% who were operated after age 10 weeks (p 5 0.54). The authors concluded that there was no significant visual advantage in performing cataract surgery at any particular time before 10 weeks of age. Birch and colleagues14 recently reported on 37 infants with dense bilateral congenital cataracts that were removed by 31 weeks of age. They demonstrated that their data best
Journal of AAPOS
Jain et al
33
FIG 2. Logarithmic values of the visual acuity at 5 years and the initial age of surgery demonstrating an inverse linear relationship with no clear break point.
fit a bilinear model with a break point at 14 weeks. During weeks 0 to 14, mean visual acuity decreased by 1 line per 3-week delay in surgery; after 14 weeks, visual acuity was independent of age of surgery, averaging 20/80. They found that early surgery (\4 weeks of age) gave the best visual outcomes irrespective of the risk of complications, as no patient who had had surgery before 4 weeks had a visual acuity worse than 20/60 (average, 20/40) in their group. They did not find evidence of a latent period in children with dense bilateral congenital cataracts and thus advocated early surgery to minimize the risk of deprivational amblyopia. We, on the contrary, have not found a biphasic fit to our data.14 Our results indicate that visual acuity (at 5 years of age) exhibits an exponential decrease with increasing initial age at surgery. We have also demonstrated an exponentially inverse relationship between the logarithmic values of age of surgery and final visual outcome and no clear break point. This may be in part attributable to the largely early surgery in our cohort: only 6 eyes (23%) were operated on after 14 weeks of age. However, we agree with Birch and colleagues14 that binocular visual deprivation for even as short a period as 4 weeks appears to adversely affect visual outcome.
Acknowledgments We thank Dr. John Hurst, Department of Academic Respiratory Medicine, Royal Free Hospital, for statistical support and help in designing the figures for this study. We also acknowledge the support received from the NIHR Manchester Biomedical Research Centre (BRC). References 1. Elston JS, Timms C. Clinical evidence for the onset of the sensitive period in infancy. Br J Ophthalmol 1992;76:327-8.
34
Jain et al
2. Von Noorden GK, Crawford MLJ. The sensitive period. Trans Ophthal Soc UK 1979;99:442-6. 3. Lambert SR, Lynn MJ, Reeves R, Plager DA, Buckley EG, Wilson ME. Is there a latent period for the surgical treatment of children with dense bilateral congenital cataracts? J AAPOS 2006;10:30-36. 4. Abadi RV, Forster JE, Lloyd IC. Ocular motor outcomes after bilateral and unilateral infantile cataracts. Vision Res 2006;46:940-52. 5. Lloyd IC, Ashworth J, Biswas S, Abadi RV. Advances in the management of congenital and infantile cataract. Eye 2007;21:1301-9. 6. Kuhli-Hattenbach C, Lu¨chtenberg M, Kohnen T, Hattenbach LO. Risk factors for complications after congenital cataract surgery without intraocular lens implantation in the first 18 months of life. Am J Ophthalmol 2008;146:1-7. 7. Watts P, Abdolell M, Levin AV. Complications in infants undergoing surgery for congenital cataract in the first 12 weeks of life: Is early surgery better? J AAPOS 2003;7:81-5. 8. Birch EE, Stager DR. The critical period for surgical treatment of dense congenital unilateral cataract. Invest Ophthalmol Vis Sci 1996;37:1532-8.
Volume 14 Number 1 / February 2010 9. Wiesel TN, Hubel DH. Comparison of the effects of unilateral and bilateral eye closure on cortical unit responses in kittens. J Neurophysiol 1965;28:1029-40. 10. Wiesel TN, Hubel DH. Extent of recovery from the effects of visual deprivation in kittens. J Neurophysiol 1965;28: 1060-72. 11. Crawford MLJ, Pesch TW, Von Noorden GK, Harwerth RS, Smith EL. Bilateral Form deprivation in monkeys—electrophysiologic and anatomic consequences. Inv Ophthalmol Vis Sci 1991;32: 2328-36. 12. Gelbart SS, Hoyt CS, Jastrebski G, Marg E. Long-term visual results in bilateral congenital cataracts. Am J Ophthalmol 1982;93: 615-21. 13. Bradford GM, Keech RV, Scott WE. Factors affecting visual outcome after surgery for bilateral congenital cataracts. Am J Ophthalmol 1994;117:58-64. 14. Birch EE, Cheng C, Stager DR Jr, Weakley DR Jr, Stager DR Sr. The critical period for surgical treatment of dense bilateral cataracts. J AAPOS 2009;13:67-71.
Journal of AAPOS
To determine optimal timing for operating on dense bilateral congenital cataracts and to define latent periods for binocular visual deprivation.
METHODS
A retrospective review of the records of children that had undergone bilateral lensectomies at our center. Infants with bilateral, dense, visually significant cataracts who had undergone lensectomy within the first year of life from 1992 to 2000 were identified. Children with other ocular anomalies, neurological and systemic disorders, intraocular lenses, or with fewer than 5 years of follow-up were excluded.
RESULTS
A total of 13 children were identified. The mean age at surgery was 8.7 weeks (range, 3–20; SD 5.3). The mean interval between surgeries of the 2 eyes was 3.8 days (range 0-7; SD 3.2). The median final visual acuity at 5 years of age was 6/18 (range, 6/5–6/36). There was a moderate correlation between (log) visual outcome and time to surgery (r 5 0.59, p 5 0.002, r2 5 0.35).
CONCLUSIONS
Visual acuity after surgery for bilateral congenital cataracts appears to decline exponentially with duration of visual deprivation. ( J AAPOS 2010;14:31-34)
V
isual outcomes after surgery for bilateral congenital cataracts have improved with advances in surgical techniques and better understanding of postoperative refractive correction and amblyopia treatment. The optimum timing for surgery, however, remains unclear. Unilateral visual deprivation in neonates during a ‘‘subcortical,’’ or latent, period for visual development, postulated to last for approximately 6 weeks of age, does not appear to affect eventual visual outcome.1 This latent period is followed by a sensitive period of cortical plasticity, which lasts approximately 7 to 8 years.2 During this period, episodes of even minor visual impairment can affect final visual function, although the effect of any adverse event becomes less marked with increasing maturity. The latent period for binocular deprivation has been more difficult to determine, but it has been posited to be around 10 weeks.3 A previous study from this unit postulated that the latent period for fixation stability and binocularity may be as short as 3 weeks.4 To further explore the optimum timing for cataract surgery in infants, we retrospectively assessed
Author affiliations: The University of Manchester, Manchester Academic Health Science Centre, Manchester Royal Eye Hospital, Manchester, United Kingdom Presented at the 35th meeting of the American Academy of Pediatric Ophthalmology and Strabismus (AAPOS) at San Francisco, California, April 17-21, 2009. Submitted April 18, 2009. Revision accepted November 24, 2009. Reprint requests: Mr. Saurabh Jain, Consultant Pediatric Ophthalmologist, Department of Ophthalmology, Royal Free Hospital, London NW3 2QG, United Kingdom (email: [email protected]). Copyright Ó 2010 by the American Association for Pediatric Ophthalmology and Strabismus. 1091-8531/2010/$36.00 1 0 doi:10.1016/j.jaapos.2009.11.016
Journal of AAPOS
a cohort of children with dense bilateral congenital cataracts who had undergone bilateral lensectomies.
Methods and Materials We retrospectively identified infants with bilateral dense, visually significant congenital cataracts who had undergone lensectomy without primary lens implantation within the first year of life from 1992 to 2000. Case notes were obtained and reviewed for collection of relevant data, including age at the time of surgery for each eye, duration between surgery on the 2 eyes, any underlying ocular and/or systemic diagnosis, intraoperative complications, further surgery or laser treatment, and visual acuity after 5 years of follow-up. Children with coexistent ocular anomalies, systemic neurodevelopmental disorders that precluded accurate assessment of visual acuity, fewer than 5 years of follow-up, and poor compliance with refractive correction or subsequent amblyopia therapy (occlusion or optical penalization) were excluded from the study. Infants with significant postoperative complications that affected final visual acuity, such as endophthalmitis and retinal detachment, also were excluded. All lensectomies were performed by the use of an anterior approach via temporal and nasal 20-gauge limbal incisions. Anterior capsulotomy was performed with a cystitome and vitrector or by continous curvilinear capsulorhexis under viscoelastic. The lens was aspirated by the use of a bimanual technique with a vitrectomy cutter and infusion positioned alternately through the 20-gauge ports. All eyes underwent posterior capsulotomy and limited anterior vitrectomy.5 The anterior chamber was irrigated with balanced salt solution containing heparin at the end of the procedure to minimize the risk of postoperative fibrinous uveitis. A peripheral iridotomy was performed with the vitrector in all eyes.
31
32
Jain et al
The second eye was operated upon either at the same time or within a week of the first, ensuring that the first operated eye was kept patched in the interim period. Topical mydriatics (cyclopentolate 0.5% in infants younger than 6 months of age and 1% in older children), steroids (prednisolone phosphate 1%), and antibiotics (chloramphenicol 0.5%) were prescribed for 4 to 6 weeks postoperatively in a tapering dose on the basis of the inflammatory activity observed on slit-lamp examination. Topical atropine 1% was used only in the presence of pupillary block or posterior synechiae. All cataracts were operated upon by the authors (ICL, SB, and JLA) or by their fellows under close supervision. Residual hypermetropic refractive error was corrected by the use of either contact lenses or spectacles. Patients were closely monitored in a dedicated pediatric cataract clinic staffed by ophthalmologists, optometrists, and orthoptists. Amblyopia, identified by interocular visual acuity difference, was treated with occlusion therapy. Statistical analysis was performed by the use of SPSS version 10. (SPSS Inc, Chicago, IL) Neither time nor visual acuity was normally distributed, and both variables were log transformed for analysis with the Pearson correlation.
Volume 14 Number 1 / February 2010 Table 1. Clinical characteristics and visual outcomes in a cohort of 13 children Age at Visual outcome Time between Serial number surgery (weeks) operated eye surgeries (days) 1 2 3 4 5 6 7 8 9 10 11
Results During the study period a total of 98 eyes in 49 children had cataract surgery. Of these, 82 eyes in 41 children were left aphakic and 16 pseudophakic. Of the 41 aphakic children, 25 (61%) were excluded from analysis on account of insufficient follow-up (3), neurodevelopmental systemic disorders (5), associated ocular malformations (10), noncompliance with amblyopia therapy (2), and surgical complications affecting final visual acuity (5). The mean age at surgery of all patients operated upon for congenital cataracts in this period was 7.7 weeks. The mean age of those excluded from the cohort analysed was 7.1 weeks. Data from the remaining 26 eyes (13 patients) were tabulated and analyzed (Table 1). The overall mean age at surgery was 8.7 weeks (range, 3-20; SD 5.3) and the mean interval between surgery of the 2 eyes was 3.8 days (range 0-7, SD 3.2). Visual Acuity and Age at Surgery The median final visual acuity at 5 years of age was 6/18 (range 6/5-6/36). There was a moderate correlation between (log) visual outcome and age at surgery (r 5 0.59, p 5 0.002, r2 5 0.35). The final visual acuity achieved after bilateral congenital cataract surgery decreased exponentially with age at surgery (Figure 1), with no demonstrable break point when plotted on a logarithmic scale (Figure 2). There was also a moderate correlation between log visual acuity of the better eye at 5 years of age and the age at surgery (r 5 0.580, p 5 0.038, r2 5 0.34)
Discussion It is widely believed that early surgery leads to better visual acuity outcomes in patients with bilateral congenital cata-
12 13
8 8 5 6 16 16 4 4.5 4 4 12 12 5 4 15 15 5 6 3 4 5 6 20 20 9 10
6/9 6/18 6/9 6/24 6/19 6/19 6/6 6/9 6/5 6/5 6/12 6/12 6/15 6/19 6/24 6/18 6/9 6/18 6/9 6/9 6/9 6/9 6/36 6/18 6/36 6/36
2 6 0 5 0 2 7 0 7 7 7 0 7
racts. This early intervention has to be balanced against the risk of associated problems, particularly glaucoma and anesthetic complications.6,7 Birch and Stager8 found that surgery performed for unilateral dense congenital cataracts before 6 weeks of age minimized the effects of unilateral visual deprivation on the developing visual system.8 Bilateral visual deprivation appears to affect the visual system differently: the neurophysiological changes in this situation are not caused by unequal competition for cortical representation. Animal studies have shown that prolonged early monocular visual deprivation leads to asymmetric changes of the striate cortex ocular dominance columns and the layers of the lateral geniculate nuclei as well as complete loss of binocularity.9,10 In contrast, similar binocular deprivation has been shown to lead to symmetric loss of only a third of striate cortex neurons.10,11 This disparity in the neurophysiological changes observed in animals has made it difficult to define a latent period for binocular deprivation in children.3 Gelbart and colleagues12 reported on 24 children operated on for bilateral congenital cataracts. They noted visual acuities of 20/60 or better in all eyes undergoing surgery before 8 weeks of age and 20/200 or worse in 86% of eyes who underwent surgery thereafter. Bradford and colleagues13reviewed the medical records of 33 children with bilateral congenital cataracts: 21 underwent surgery before 8 weeks of age and the rest later in infancy. They suggested that age of surgery was not prognostically related to visual outcome. However,
Journal of AAPOS
Volume 14 Number 1 / February 2010
FIG 1. Visual acuity (at 5 years of age) exhibits an exponential decrease with increasing initial age at surgery in 13 children (26 eyes).
a significant proportion of the children had coexistent ocular disorders, and the late surgery group included infants with acquired cataracts, making their results difficult to interpret. Abadi and colleagues4 studied the effect of the duration and severity of early-onset visual deprivation on ocular alignment and stability. The study group consisted of 33 children (aged 1 week to 12.8 years) with infantile cataracts who were observed for up to 61 months to assess visual acuity and fixation stability. Of these, 5 children experienced bilateral major form deprivation and underwent surgery between 4 and 14 weeks of age. Of the 5, 2 exhibited unstable fixation before surgery after experiencing only 8 weeks of visual deprivation. All 5 exhibited postoperative fixation instability (3 manifest latent nystagmus, 1 latent nystagmus, and 1 congenital nystagmus). The authors interpreted these results as suggesting that deprivation periods as short as 3 weeks can lead to a sustained nystagmus, which is usually of the manifest latent variety.4 Lambert and colleagues3 noted a linear trend between visual outcome and age at surgery for children with bilateral visually significant congenital cataracts, although this trend failed to reach statistical significance. In a series of 43 children with 5 years of follow-up, visual acuity of 20/100 or worse occurred only in eyes undergoing surgery after 10 weeks of age. However, good visual acuity outcomes were achieved in both groups, with final visual acuity of 20/40 or better in 67% in patients who had surgery at age 10 weeks or younger and 55% who were operated after age 10 weeks (p 5 0.54). The authors concluded that there was no significant visual advantage in performing cataract surgery at any particular time before 10 weeks of age. Birch and colleagues14 recently reported on 37 infants with dense bilateral congenital cataracts that were removed by 31 weeks of age. They demonstrated that their data best
Journal of AAPOS
Jain et al
33
FIG 2. Logarithmic values of the visual acuity at 5 years and the initial age of surgery demonstrating an inverse linear relationship with no clear break point.
fit a bilinear model with a break point at 14 weeks. During weeks 0 to 14, mean visual acuity decreased by 1 line per 3-week delay in surgery; after 14 weeks, visual acuity was independent of age of surgery, averaging 20/80. They found that early surgery (\4 weeks of age) gave the best visual outcomes irrespective of the risk of complications, as no patient who had had surgery before 4 weeks had a visual acuity worse than 20/60 (average, 20/40) in their group. They did not find evidence of a latent period in children with dense bilateral congenital cataracts and thus advocated early surgery to minimize the risk of deprivational amblyopia. We, on the contrary, have not found a biphasic fit to our data.14 Our results indicate that visual acuity (at 5 years of age) exhibits an exponential decrease with increasing initial age at surgery. We have also demonstrated an exponentially inverse relationship between the logarithmic values of age of surgery and final visual outcome and no clear break point. This may be in part attributable to the largely early surgery in our cohort: only 6 eyes (23%) were operated on after 14 weeks of age. However, we agree with Birch and colleagues14 that binocular visual deprivation for even as short a period as 4 weeks appears to adversely affect visual outcome.
Acknowledgments We thank Dr. John Hurst, Department of Academic Respiratory Medicine, Royal Free Hospital, for statistical support and help in designing the figures for this study. We also acknowledge the support received from the NIHR Manchester Biomedical Research Centre (BRC). References 1. Elston JS, Timms C. Clinical evidence for the onset of the sensitive period in infancy. Br J Ophthalmol 1992;76:327-8.
34
Jain et al
2. Von Noorden GK, Crawford MLJ. The sensitive period. Trans Ophthal Soc UK 1979;99:442-6. 3. Lambert SR, Lynn MJ, Reeves R, Plager DA, Buckley EG, Wilson ME. Is there a latent period for the surgical treatment of children with dense bilateral congenital cataracts? J AAPOS 2006;10:30-36. 4. Abadi RV, Forster JE, Lloyd IC. Ocular motor outcomes after bilateral and unilateral infantile cataracts. Vision Res 2006;46:940-52. 5. Lloyd IC, Ashworth J, Biswas S, Abadi RV. Advances in the management of congenital and infantile cataract. Eye 2007;21:1301-9. 6. Kuhli-Hattenbach C, Lu¨chtenberg M, Kohnen T, Hattenbach LO. Risk factors for complications after congenital cataract surgery without intraocular lens implantation in the first 18 months of life. Am J Ophthalmol 2008;146:1-7. 7. Watts P, Abdolell M, Levin AV. Complications in infants undergoing surgery for congenital cataract in the first 12 weeks of life: Is early surgery better? J AAPOS 2003;7:81-5. 8. Birch EE, Stager DR. The critical period for surgical treatment of dense congenital unilateral cataract. Invest Ophthalmol Vis Sci 1996;37:1532-8.
Volume 14 Number 1 / February 2010 9. Wiesel TN, Hubel DH. Comparison of the effects of unilateral and bilateral eye closure on cortical unit responses in kittens. J Neurophysiol 1965;28:1029-40. 10. Wiesel TN, Hubel DH. Extent of recovery from the effects of visual deprivation in kittens. J Neurophysiol 1965;28: 1060-72. 11. Crawford MLJ, Pesch TW, Von Noorden GK, Harwerth RS, Smith EL. Bilateral Form deprivation in monkeys—electrophysiologic and anatomic consequences. Inv Ophthalmol Vis Sci 1991;32: 2328-36. 12. Gelbart SS, Hoyt CS, Jastrebski G, Marg E. Long-term visual results in bilateral congenital cataracts. Am J Ophthalmol 1982;93: 615-21. 13. Bradford GM, Keech RV, Scott WE. Factors affecting visual outcome after surgery for bilateral congenital cataracts. Am J Ophthalmol 1994;117:58-64. 14. Birch EE, Cheng C, Stager DR Jr, Weakley DR Jr, Stager DR Sr. The critical period for surgical treatment of dense bilateral cataracts. J AAPOS 2009;13:67-71.
Journal of AAPOS