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Ocular Axial Length Changes in Pseudophakic Children After Traumatic and Congenital Cataract Surgery
Ocular Axial Length Changes in Pseudophakic Children After Traumatic and Congenital Cataract Surgery Hana Leiba, MD, Amira Springer, MD, and Ayala Pollack, MD BACKGROUND
METHODS
RESULTS
CONCLUSIONS
Pseudophakic children tend to develop a large myopic shift. This may be in part due to accelerated growth in axial length. The purpose of this study was to evaluate and compare the postoperative change in axial length (⌬AL) in pseudophakic eyes, after extraction of traumatic or congenital cataract. Included in this retrospective study were 20 children who had undergone surgery for traumatic, unilateral congenital, or bilateral congenital cataracts. All patients were under 10 years old at the time of operation. Axial length was measured perioperatively as well as 1 year or more postoperatively. The three groups were subdivided according to patients’ ages ( below or above 5 years). The ⌬AL in the operated eyes was compared with ⌬AL of the fellow nonoperated eyes. The difference in ⌬AL between operated and fellow nonoperated eyes was compared among the groups. ⌬AL was greater for operated eyes than for fellow nonoperated eyes (traumatic cataract: p ⫽ 0.06; unilateral congenital cataract, p ⫽ 0.055). Axial elongation was significantly greater in children under 5 years old at operation than in those older than 5 ( p ⫽ 0.025). The difference in rate of ⌬AL between operated and fellow nonoperated eyes, per 1 year of follow-up, was similar for traumatic and unilateral congenital cataract groups. This study demonstrated a tendency toward greater axial lengthening in pseudophakic eyes of children, when compared with their nonoperated eyes. No significant difference was found in the tendency for increased axial lengthening between eyes operated on for traumatic cataracts and those operated on for congenital cataracts. ( J AAPOS 2006;10: 460-463)
C
hildren with normal eyes tend to develop a myopic shift over time.1,2 A cross-sectional study of children with normal eyes by Gordon and Donzis showed that, as the eye grows, the refractive error declines from an average of ⫹0.4 D at birth to ⫺0.5 D in adults. The axial length (AL) in these children increased from an average of 16.8 mm in full-term infants to 23.6 mm in adults.1 This increase in AL, which by itself would produce an extensive shift toward myopia, is offset by concomitant changes in the lens, which reduces its refractive power.1,2 In children with aphakic or pseudophakic eyes, however, where the refractive power of the lens remains constant, a larger myopic shift might be expected as the eye grows.3-8 It is a matter of debate whether the extent of the myopic
Author affiliations: Department of Ophthalmology, Kaplan Medical Center, Rehovot, Israel (Affiliated with The Hebrew University—Hadassah Medical School, Jerusalem, Israel). Presented at the 28th Annual Meeting of the American Association for Pediatric Ophthalmology and Strabismus, Seattle, Washington, March 20-24, 2002. Submitted March 26, 2002. Revision accepted June 19, 2006. Reprint requests: H. Leiba, MD, Department of Ophthalmology, Kaplan Medical Center, 76100, Rehovot, Israel (email: [email protected]). Copyright © 2006 by the American Association for Pediatric Ophthalmology and Strabismus. 1091-8531/2006/$35.00 ⫹ 0 doi:10.1016/j.jaapos.2006.06.006
460
shift seen in these children is related to the disequilibrium between the lens power and the AL or to excessive growth of these eyes, relative to that in normal phakic eyes.3-8 Some authors have observed a rapid increase in the AL of the operated eye of children with congenital cataract, compared with the fellow nonoperated eye, whereas others have reported a retardation in AL growth.9-11 Other studies have not found a trend toward retardation or acceleration of axial growth in pseudophakic compared with phakic eyes.12,13 The majority of the reports describe patients who underwent surgery for congenital cataract. The aim of the present study was to retrospectively evaluate and compare the change in axial length in pseudophakic children, who were operated for congenital cataract versus traumatic cataract.
Subjects and Methods We retrospectively reviewed the medical records of all patients, aged 10 years or younger at the time of operation, who had undergone extraction of congenital or traumatic cataract with intraocular lens implantation between 1986 and 1999. Only eyes with at least 1 year of follow-up were included in the study. In all cases polymethylmethacrylate (PMMA) lenses were used. All eyes included in the study had a record of at least two AL
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461
Table 1. Patients’ ages at time of operation and follow-up times Bilateral congenital cataract Traumatic cataract
Unilateral congenital cataract
First eye
Second eye
5 6.23 3.17-9.25 6.15 4.50-7.33
9 3.26 0.08-8.50 7.84 4.0-10.0
6 4.85 0.25-9.57 6.79 2.0-13.0
6 5.3 0.33-10.0 6.28 1.92-12.0
Number of patients Mean age (y) (range) Follow-up (y) (range)
Table 2. Changes in axial length of patients treated for traumatic cataract ⌬AL (mm) Patient
Age at operation (yr)
Follow-up (yr)
1 2 3 4 5 Mean
3.17 6 6 6.75 9.25 6.23
7.42 6.17 4.5 7.33 5.33 6.15
Final VA 20/33 20/30 20/40 20/60 20/33
Operated eye
Nonoperated fellow eye
p-value
2.76 1.25 1.52 2.17 3.04 2.15
1.28 0.79 1.72 0.87 1.07 1.14
0.06
VA: visual acuity; ⌬AL: last measured AL minus perioperative AL.
Table 3. Changes in axial length of patients treated for unilateral congenital cataract ⌬AL (mm) Patient
Age at operation (yr)
Follow-up (yr)
1 2 3 4 5 6 7 8 9 Mean
0.08 1 1.33 2 2 3.17 4.25 7 8.59 3.26
9 7 10 8.92 7.08 8.6 4 7.67 8.25 7.84
Final VA 20/100 NA 20/100 FC 20/200 FC 20/40 20/33 20/30
Operated eye
Nonoperated fellow eye
p-value
1 2.8 3.5 2.3 2 2.76 0.94 3.5 0.47 2.14
1 2.7 1 1.44 1.7 1.07 0.59 1.19 0.49 1.25
0.055
VA: visual acuity; ⌬AL: last measured AL minus perioperative AL; NA: nonapplicable; FC: finger counting.
measurements: one taken before or at the time of surgery and the other taken at the last follow-up examination. All measurements of AL, both perioperatively and during follow-up, were obtained using a contact ultrasonic biometer (model 820, Allergan, Humphrey, San Leandro, CA), capable of adequately measuring both phakic and pseudophakic eyes. Patients were sedated when necessary. Excluded were eyes with microphthalmia, glaucoma, persistent fetal vasculature, or retinal or optic nerve anomalies. The patients were divided into groups according to the type of cataract (traumatic, unilateral congenital, or bilateral congenital), and then into two subgroups according to age at the time of surgery ( younger than 5 years, or 5 years and older). The change in AL (⌬AL) in the operated eyes was compared with ⌬AL measured at the same time in the fellow nonoperated eyes. We also compared the change in AL values between the different groups. Student’s t-test was used for statistical analysis. Values of p ⬍ 0.05 were considered statistically significant.
Journal of AAPOS
Results Forty eyes of 20 patients were included in the study. Of these, 5 eyes underwent surgery for traumatic cataract, 9 eyes underwent surgery for unilateral congenital cataract, and 12 eyes (6 patients) underwent surgery for bilateral congenital cataract. Patients’ ages at the time of surgery and follow-up times are summarized in Table 1. Tables 2 to 4 show the postoperative changes in axial length (⌬AL) for patients with traumatic cataract, unilateral congenital cataract, and bilateral congenital cataract, respectively. The mean ⌬AL of the operated eyes in both traumatic and unilateral congenital cataract groups was greater than that of the nonoperated fellow eyes ( p ⫽ 0.06 and p ⫽ 0.055, respectively). In the bilateral congenital cataract group, the mean ⌬AL of the first operated eyes was slightly greater than the mean ⌬AL of the second operated eyes ( p ⫽ 0.85).
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Volume 10 Number 5 October 2006
Table 4. Changes in axial length of patients treated for bilateral congenital cataract Age at operation
Follow-up
⌬AL
Final VA
Patient
1st eye
2nd eye
1st eye
2nd eye
1st eye
2nd eye
1st eye
2nd eye
p-value
1 2 3 4 5 6 Mean
0.25 0.75 6 6.25 6.33 9.57 4.85
0.33 1.33 6.33 6.92 6.92 10 5.3
2 13 4 10.25 2.6 8.92 6.79
1.92 12 3.67 9.6 2 8.5 6.28
20/300 NA 20/133 20/25 20/30 20/133
20/300 NA 20/25 20/30 20/30 20/30
4.6 0.3 0.58 0.81 0 1.55 1.38
3.93 0.3 0 0.55 0 2 1.13
0.85
VA: visual acuity; ⌬AL: Last measured AL minus perioperative AL; NA: nonapplicable.
Table 5. The mean difference (in mm) between axial lengthening of operated and nonoperated fellow-eyes per one year of follow-up ⫽ (⌬AL[operated eye] ⫺ ⌬AL[nonoperated eye])/follow-up years
All patients Younger than 5 years at time of operation Five years or older at time of operation
Traumatic cataract
Unilateral congenital cataract
0.16 0.2
0.11 0.10
0.15
0.14
The mean ⌬AL of all operated eyes (1.72 ⫾ 1.34 mm, n ⫽ 26) was greater than that of all nonoperated eyes (1.21 ⫾ 0.56, n ⫽ 14), but the difference was not statistically significant ( p ⫽ 0.092). Twelve eyes were operated when the patients were younger than 5 years and 14 eyes were operated when the patients were 5 years or older. The mean ⌬AL was 2.26 ⫾ 1.40 mm in the younger group (with a mean follow-up time of 7.57 years) and 1.25 ⫾ 1.12 mm in the older group (with a mean follow-up time of 6.34 years). This difference was statistically significant ( p ⫽ 0.025). To eliminate the effect of differences in follow-up times between patients, the difference between the lengthening of the operated eye and the nonoperated fellow eye was calculated for each patient per 1 year of follow-up, in both the traumatic and the unilateral congenital cataract groups (Table 5). This was calculated by dividing the difference in the total lengthening of the operated and the nonoperated fellow eye by the total number of follow-up years for each patient. The difference in lengthening between the operated and nonoperated fellow eyes per 1 year of follow-up was similar for the traumatic cataract group (0.16 mm) and the unilateral congenital cataract group (0.11 mm). This similarity was consistently found in both younger and older subgroups.
Discussion A number of studies have documented a myopic shift in eyes operated on for cataract in childhood.3-8 With the increasing popularity of intraocular lens (IOL) implantation in children, factors such as axial elongation should be taken into consideration when calculating the power of the IOL to be implanted.
An increase in AL has been reported after cataract operation with and without IOL implantation.9,10 However, some authors have reported that most pseudophakic eyes grow according to the normal curve.12,13 Griener et al measured the AL in the eyes of 11 monocularly pseudophakic infants who were operated on between 2 and 4 months of age. In seven patients the mean growth in AL was 0.46 mm less in the pseudophakic eye than in the fellow eye; in one patient there was no difference in AL between the two eyes, and in three the AL in the pseudophakic eye was longer.11 In our study, the mean change in AL postoperatively was greater in the pseudophakic eyes than in the nonoperated fellow eyes, in both traumatic and unilateral congenital groups, with the difference reaching only borderline statistical significance (Tables 2 and 3). Gordon and Donzis showed that in normal eyes the greatest increase in AL occurs in the youngest age groups. After the age of 5 to 6 years the AL increases by approximately 1 mm, to its adult length. No significant increase in AL was noted after 10 to 15 years of age.1 Our study included only patients who were 10 years old or younger at the time of operation. The patients in the congenital cataract groups were younger than the patients in the traumatic cataract group (Table 1). These differences in ages between the groups might be expected, due to the different etiologies for surgery in the three groups of patients in our study. When all operated eyes were divided into subgroups according to age at the time of surgery, we found almost double the elongation for similar follow-up periods, in eyes of patients younger than 5 when compared with eyes of patients 5 years and older ( p ⫽ 0.025). It is possible that the age differences between the groups might have had some influence on the ⌬AL results. The pathogenesis of the increase in axial lengthening of operated eyes is not completely understood. Some investigators view it as a direct effect of cataract surgery.9,10 However, when the change in AL of 14 bilaterally aphakic children who underwent bilateral cataract extraction for congenital cataract was compared with the change in AL of 8 such eyes that were not operated on, no significant difference was found between the two groups.9 Other authors attribute the increased axial lengthening to the original ocular pathology and amblyopia. Studies in
Journal of AAPOS
Volume 10 Number 5 October 2006
animal models suggest that alteration of visual input in early life may affect the axial growth of the eye. Severe visual deprivation produced in these models by lid suturing,14 corneal opacification,15 or an opaque contact lens16 resulted in axial elongation. Cataract and ptosis have the same effect on humans.17,18 Smaller degrees of visual deprivation were shown to retard axial elongation. Bradley and colleagues19 reported that in monkeys reared from birth with monocular visual deprivation produced by a translucent contact lens, the AL of the treated eyes was shorter than that of the untreated fellow eyes. Axial elongation was also retarded in aphakic16 and pseudophakic20 monkeys. In our study, no persistent correlation was found between final visual acuities and the extent of axial elongation (Tables 2 to 4). To eliminate the effect of different follow-up times of the different patients on their total axial lengthening, we calculated the difference in lengthening of the two fellow eyes of each patient per 1 year of follow-up. No significant difference was found between patients operated for traumatic cataract and patients operated for unilateral congenital cataract with no other ocular pathology. This retrospective study has limitations. The relatively small number of patients limits the reliability of statistical analysis. In addition, patients in the congenital cataract groups were generally younger than patients in the traumatic cataract group, and the few cases of amblyopia were found only among the congenital cataract groups. Nevertheless, this study did demonstrate a tendency toward greater axial lengthening in pseudophakic eyes of children compared with their nonoperated eyes; it did not demonstrate a significant difference in the tendency for increased axial lengthening between eyes operated on for traumatic cataracts and those operated on for congenital cataracts.
Leiba, Springer, and Pollack
4.
5.
6. 7.
8.
9. 10.
11.
12.
13.
14. 15.
16.
17. 18.
References 1. Gordon RA, Donzis PB. Refractive development of the human eye. Arch Ophthalmol 1985;103:785-9. 2. Brown NP, Koretz JF, Bron AJ. The development and maintenance of emmetropia. Eye 1999;13:83-92. 3. Spierer A, Desatnik H, Blumenthal M. Refractive status in children after long-term follow-up of cataract surgery with intraoc-
Journal of AAPOS
19.
20.
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ular lens implantation. J Pediatr Ophthalmol Strabismus 1999;36:25-9. Lambert SR, Buckley EG, Plager DA, Medow NB, Wilson ME. Unilateral intraocular lens implantation during the first six months of life. J AAPOS 1999;3:344-9. Hutchinson AK, Drews-Botsch C, Lambert SR. Myopic shift after intraocular lens implantation during childhood. Ophthalmology 1997;104:1752-7. McClatchey SK, Parks MM. Theoretic refractive changes after lens implantation in childhood. Ophthalmology 1997;104:1744-51. Moore BD. Changes in aphakic refraction of children with unilateral congenital cataracts. J Pediatr Ophthalmol Strabismus 1989; 26:290-4. O’Keefe M, Fenton S, Lanigan B. Visual outcomes and complications of posterior chamber intraocular lens implantation in the first year of life. J Cataract Refrarct Surg 2001;27:2006-11. Rasooly R, BenEzra D. Congenital and traumatic cataract. Arch Ophthalmol 1988;106:1066-8. Kora Y, Shimizu K, Inatomi M, Fukado Y, Ozawa T. Eye growth after cataract extraction and intraocuar lens implantation in children. Ophthalmol Surg 1993;24:467-75. Griener ED, Dahan E, Lambert SR. Effect of age at time of cataract surgery on subsequent axial length growth in infant eyes. J Cataract Refract Surg 1999;25:1209-13. Hutchinson AK, Wilson E, Saunders RA. Outcomes and ocular growth rates after intraocular lens implantation in the first 2 years of life. J Catarct Refract Surg 1998;24:846-52. Flitcroft DI, Knight-Nanan D, Bowell R, Lanigan B, O’Keefe M. Intraocular lenses in children: changes in axial length, corneal curvature and refraction. Br J Ophthalmol 1999;83:265-9. Raviola E, Wiesel TN. An animal model of myopia. N Engl J Med 1985;312:1609-15. Weisel TN, Raviola E. Increase in axial length of the macaque monkey after corneal opacification. Invest Ophthalmol Vis Sci 1979; 18:1232-6. Tigges M, Tigges J, Fernandaes A, Eggers HM, Gammon JA. Postantal axial eye elongation in normal and visually deprived rhesus monkeys. Invest Ophthalmol Vis Sci 1990;31:1035-46. Rabin J, Van Sluyters R, Malach R. Emmetropization: a visiondependent phenomenon. Invest Ophthalmol 1981;20:561-4. Von Noorden GK, Lewis RA. Ocular axial length in unilateral congenital cataracts and blepharoptosis. Invent Ophthalmol Vis Sci 1987;28:750-2. Bradley DV, Fernandes A, Tigges M, Boothe RG. Diffuser contact lenses retard axial elongation in infant Rhesus monkeys. Vision Res 1996;36:509-14. Lambert SR, Fernandes A, Drews-Botsch C, Tigges M. Pseudophakia retards axial elongation in neonatal monkey eyes. Invest Ophthalmol Vis Sci 1996;37:451-8.
METHODS
RESULTS
CONCLUSIONS
Pseudophakic children tend to develop a large myopic shift. This may be in part due to accelerated growth in axial length. The purpose of this study was to evaluate and compare the postoperative change in axial length (⌬AL) in pseudophakic eyes, after extraction of traumatic or congenital cataract. Included in this retrospective study were 20 children who had undergone surgery for traumatic, unilateral congenital, or bilateral congenital cataracts. All patients were under 10 years old at the time of operation. Axial length was measured perioperatively as well as 1 year or more postoperatively. The three groups were subdivided according to patients’ ages ( below or above 5 years). The ⌬AL in the operated eyes was compared with ⌬AL of the fellow nonoperated eyes. The difference in ⌬AL between operated and fellow nonoperated eyes was compared among the groups. ⌬AL was greater for operated eyes than for fellow nonoperated eyes (traumatic cataract: p ⫽ 0.06; unilateral congenital cataract, p ⫽ 0.055). Axial elongation was significantly greater in children under 5 years old at operation than in those older than 5 ( p ⫽ 0.025). The difference in rate of ⌬AL between operated and fellow nonoperated eyes, per 1 year of follow-up, was similar for traumatic and unilateral congenital cataract groups. This study demonstrated a tendency toward greater axial lengthening in pseudophakic eyes of children, when compared with their nonoperated eyes. No significant difference was found in the tendency for increased axial lengthening between eyes operated on for traumatic cataracts and those operated on for congenital cataracts. ( J AAPOS 2006;10: 460-463)
C
hildren with normal eyes tend to develop a myopic shift over time.1,2 A cross-sectional study of children with normal eyes by Gordon and Donzis showed that, as the eye grows, the refractive error declines from an average of ⫹0.4 D at birth to ⫺0.5 D in adults. The axial length (AL) in these children increased from an average of 16.8 mm in full-term infants to 23.6 mm in adults.1 This increase in AL, which by itself would produce an extensive shift toward myopia, is offset by concomitant changes in the lens, which reduces its refractive power.1,2 In children with aphakic or pseudophakic eyes, however, where the refractive power of the lens remains constant, a larger myopic shift might be expected as the eye grows.3-8 It is a matter of debate whether the extent of the myopic
Author affiliations: Department of Ophthalmology, Kaplan Medical Center, Rehovot, Israel (Affiliated with The Hebrew University—Hadassah Medical School, Jerusalem, Israel). Presented at the 28th Annual Meeting of the American Association for Pediatric Ophthalmology and Strabismus, Seattle, Washington, March 20-24, 2002. Submitted March 26, 2002. Revision accepted June 19, 2006. Reprint requests: H. Leiba, MD, Department of Ophthalmology, Kaplan Medical Center, 76100, Rehovot, Israel (email: [email protected]). Copyright © 2006 by the American Association for Pediatric Ophthalmology and Strabismus. 1091-8531/2006/$35.00 ⫹ 0 doi:10.1016/j.jaapos.2006.06.006
460
shift seen in these children is related to the disequilibrium between the lens power and the AL or to excessive growth of these eyes, relative to that in normal phakic eyes.3-8 Some authors have observed a rapid increase in the AL of the operated eye of children with congenital cataract, compared with the fellow nonoperated eye, whereas others have reported a retardation in AL growth.9-11 Other studies have not found a trend toward retardation or acceleration of axial growth in pseudophakic compared with phakic eyes.12,13 The majority of the reports describe patients who underwent surgery for congenital cataract. The aim of the present study was to retrospectively evaluate and compare the change in axial length in pseudophakic children, who were operated for congenital cataract versus traumatic cataract.
Subjects and Methods We retrospectively reviewed the medical records of all patients, aged 10 years or younger at the time of operation, who had undergone extraction of congenital or traumatic cataract with intraocular lens implantation between 1986 and 1999. Only eyes with at least 1 year of follow-up were included in the study. In all cases polymethylmethacrylate (PMMA) lenses were used. All eyes included in the study had a record of at least two AL
Journal of AAPOS
Volume 10 Number 5 October 2006
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461
Table 1. Patients’ ages at time of operation and follow-up times Bilateral congenital cataract Traumatic cataract
Unilateral congenital cataract
First eye
Second eye
5 6.23 3.17-9.25 6.15 4.50-7.33
9 3.26 0.08-8.50 7.84 4.0-10.0
6 4.85 0.25-9.57 6.79 2.0-13.0
6 5.3 0.33-10.0 6.28 1.92-12.0
Number of patients Mean age (y) (range) Follow-up (y) (range)
Table 2. Changes in axial length of patients treated for traumatic cataract ⌬AL (mm) Patient
Age at operation (yr)
Follow-up (yr)
1 2 3 4 5 Mean
3.17 6 6 6.75 9.25 6.23
7.42 6.17 4.5 7.33 5.33 6.15
Final VA 20/33 20/30 20/40 20/60 20/33
Operated eye
Nonoperated fellow eye
p-value
2.76 1.25 1.52 2.17 3.04 2.15
1.28 0.79 1.72 0.87 1.07 1.14
0.06
VA: visual acuity; ⌬AL: last measured AL minus perioperative AL.
Table 3. Changes in axial length of patients treated for unilateral congenital cataract ⌬AL (mm) Patient
Age at operation (yr)
Follow-up (yr)
1 2 3 4 5 6 7 8 9 Mean
0.08 1 1.33 2 2 3.17 4.25 7 8.59 3.26
9 7 10 8.92 7.08 8.6 4 7.67 8.25 7.84
Final VA 20/100 NA 20/100 FC 20/200 FC 20/40 20/33 20/30
Operated eye
Nonoperated fellow eye
p-value
1 2.8 3.5 2.3 2 2.76 0.94 3.5 0.47 2.14
1 2.7 1 1.44 1.7 1.07 0.59 1.19 0.49 1.25
0.055
VA: visual acuity; ⌬AL: last measured AL minus perioperative AL; NA: nonapplicable; FC: finger counting.
measurements: one taken before or at the time of surgery and the other taken at the last follow-up examination. All measurements of AL, both perioperatively and during follow-up, were obtained using a contact ultrasonic biometer (model 820, Allergan, Humphrey, San Leandro, CA), capable of adequately measuring both phakic and pseudophakic eyes. Patients were sedated when necessary. Excluded were eyes with microphthalmia, glaucoma, persistent fetal vasculature, or retinal or optic nerve anomalies. The patients were divided into groups according to the type of cataract (traumatic, unilateral congenital, or bilateral congenital), and then into two subgroups according to age at the time of surgery ( younger than 5 years, or 5 years and older). The change in AL (⌬AL) in the operated eyes was compared with ⌬AL measured at the same time in the fellow nonoperated eyes. We also compared the change in AL values between the different groups. Student’s t-test was used for statistical analysis. Values of p ⬍ 0.05 were considered statistically significant.
Journal of AAPOS
Results Forty eyes of 20 patients were included in the study. Of these, 5 eyes underwent surgery for traumatic cataract, 9 eyes underwent surgery for unilateral congenital cataract, and 12 eyes (6 patients) underwent surgery for bilateral congenital cataract. Patients’ ages at the time of surgery and follow-up times are summarized in Table 1. Tables 2 to 4 show the postoperative changes in axial length (⌬AL) for patients with traumatic cataract, unilateral congenital cataract, and bilateral congenital cataract, respectively. The mean ⌬AL of the operated eyes in both traumatic and unilateral congenital cataract groups was greater than that of the nonoperated fellow eyes ( p ⫽ 0.06 and p ⫽ 0.055, respectively). In the bilateral congenital cataract group, the mean ⌬AL of the first operated eyes was slightly greater than the mean ⌬AL of the second operated eyes ( p ⫽ 0.85).
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Volume 10 Number 5 October 2006
Table 4. Changes in axial length of patients treated for bilateral congenital cataract Age at operation
Follow-up
⌬AL
Final VA
Patient
1st eye
2nd eye
1st eye
2nd eye
1st eye
2nd eye
1st eye
2nd eye
p-value
1 2 3 4 5 6 Mean
0.25 0.75 6 6.25 6.33 9.57 4.85
0.33 1.33 6.33 6.92 6.92 10 5.3
2 13 4 10.25 2.6 8.92 6.79
1.92 12 3.67 9.6 2 8.5 6.28
20/300 NA 20/133 20/25 20/30 20/133
20/300 NA 20/25 20/30 20/30 20/30
4.6 0.3 0.58 0.81 0 1.55 1.38
3.93 0.3 0 0.55 0 2 1.13
0.85
VA: visual acuity; ⌬AL: Last measured AL minus perioperative AL; NA: nonapplicable.
Table 5. The mean difference (in mm) between axial lengthening of operated and nonoperated fellow-eyes per one year of follow-up ⫽ (⌬AL[operated eye] ⫺ ⌬AL[nonoperated eye])/follow-up years
All patients Younger than 5 years at time of operation Five years or older at time of operation
Traumatic cataract
Unilateral congenital cataract
0.16 0.2
0.11 0.10
0.15
0.14
The mean ⌬AL of all operated eyes (1.72 ⫾ 1.34 mm, n ⫽ 26) was greater than that of all nonoperated eyes (1.21 ⫾ 0.56, n ⫽ 14), but the difference was not statistically significant ( p ⫽ 0.092). Twelve eyes were operated when the patients were younger than 5 years and 14 eyes were operated when the patients were 5 years or older. The mean ⌬AL was 2.26 ⫾ 1.40 mm in the younger group (with a mean follow-up time of 7.57 years) and 1.25 ⫾ 1.12 mm in the older group (with a mean follow-up time of 6.34 years). This difference was statistically significant ( p ⫽ 0.025). To eliminate the effect of differences in follow-up times between patients, the difference between the lengthening of the operated eye and the nonoperated fellow eye was calculated for each patient per 1 year of follow-up, in both the traumatic and the unilateral congenital cataract groups (Table 5). This was calculated by dividing the difference in the total lengthening of the operated and the nonoperated fellow eye by the total number of follow-up years for each patient. The difference in lengthening between the operated and nonoperated fellow eyes per 1 year of follow-up was similar for the traumatic cataract group (0.16 mm) and the unilateral congenital cataract group (0.11 mm). This similarity was consistently found in both younger and older subgroups.
Discussion A number of studies have documented a myopic shift in eyes operated on for cataract in childhood.3-8 With the increasing popularity of intraocular lens (IOL) implantation in children, factors such as axial elongation should be taken into consideration when calculating the power of the IOL to be implanted.
An increase in AL has been reported after cataract operation with and without IOL implantation.9,10 However, some authors have reported that most pseudophakic eyes grow according to the normal curve.12,13 Griener et al measured the AL in the eyes of 11 monocularly pseudophakic infants who were operated on between 2 and 4 months of age. In seven patients the mean growth in AL was 0.46 mm less in the pseudophakic eye than in the fellow eye; in one patient there was no difference in AL between the two eyes, and in three the AL in the pseudophakic eye was longer.11 In our study, the mean change in AL postoperatively was greater in the pseudophakic eyes than in the nonoperated fellow eyes, in both traumatic and unilateral congenital groups, with the difference reaching only borderline statistical significance (Tables 2 and 3). Gordon and Donzis showed that in normal eyes the greatest increase in AL occurs in the youngest age groups. After the age of 5 to 6 years the AL increases by approximately 1 mm, to its adult length. No significant increase in AL was noted after 10 to 15 years of age.1 Our study included only patients who were 10 years old or younger at the time of operation. The patients in the congenital cataract groups were younger than the patients in the traumatic cataract group (Table 1). These differences in ages between the groups might be expected, due to the different etiologies for surgery in the three groups of patients in our study. When all operated eyes were divided into subgroups according to age at the time of surgery, we found almost double the elongation for similar follow-up periods, in eyes of patients younger than 5 when compared with eyes of patients 5 years and older ( p ⫽ 0.025). It is possible that the age differences between the groups might have had some influence on the ⌬AL results. The pathogenesis of the increase in axial lengthening of operated eyes is not completely understood. Some investigators view it as a direct effect of cataract surgery.9,10 However, when the change in AL of 14 bilaterally aphakic children who underwent bilateral cataract extraction for congenital cataract was compared with the change in AL of 8 such eyes that were not operated on, no significant difference was found between the two groups.9 Other authors attribute the increased axial lengthening to the original ocular pathology and amblyopia. Studies in
Journal of AAPOS
Volume 10 Number 5 October 2006
animal models suggest that alteration of visual input in early life may affect the axial growth of the eye. Severe visual deprivation produced in these models by lid suturing,14 corneal opacification,15 or an opaque contact lens16 resulted in axial elongation. Cataract and ptosis have the same effect on humans.17,18 Smaller degrees of visual deprivation were shown to retard axial elongation. Bradley and colleagues19 reported that in monkeys reared from birth with monocular visual deprivation produced by a translucent contact lens, the AL of the treated eyes was shorter than that of the untreated fellow eyes. Axial elongation was also retarded in aphakic16 and pseudophakic20 monkeys. In our study, no persistent correlation was found between final visual acuities and the extent of axial elongation (Tables 2 to 4). To eliminate the effect of different follow-up times of the different patients on their total axial lengthening, we calculated the difference in lengthening of the two fellow eyes of each patient per 1 year of follow-up. No significant difference was found between patients operated for traumatic cataract and patients operated for unilateral congenital cataract with no other ocular pathology. This retrospective study has limitations. The relatively small number of patients limits the reliability of statistical analysis. In addition, patients in the congenital cataract groups were generally younger than patients in the traumatic cataract group, and the few cases of amblyopia were found only among the congenital cataract groups. Nevertheless, this study did demonstrate a tendency toward greater axial lengthening in pseudophakic eyes of children compared with their nonoperated eyes; it did not demonstrate a significant difference in the tendency for increased axial lengthening between eyes operated on for traumatic cataracts and those operated on for congenital cataracts.
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Journal of AAPOS
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