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Nucci P (ed): Pediatric Cataract.

Dev Ophthalmol. Basel, Karger, 2016, vol 57, pp 29–39 (DOI: 10.1159/000442498)

Changes in Ocular Growth after Pediatric Cataract Surgery Scott R. Lambert Department of Ophthalmology, School of Medicine, Emory University, Atlanta, Ga., USA

Abstract The human eye undergoes extensive changes during early childhood, including axial elongation, corneal flattening and reduced lens power. Animal studies have shown that removing the crystalline lens during infancy retards axial elongation. Axial elongation has been studied in children after cataract extraction both directly and indirectly. Children with a unilateral congenital cataract generally have a shorter axial length in their cataractous eye than in their fellow eye. This difference usually persists after cataract surgery. While some studies have reported a modest reduction in axial elongation after cataract extraction, the magnitude of this effect is much less than what has been reported in animal models. Choosing an intraocular lens (IOL) power for implantation into a child’s eye is complicated by continued ocular growth, the inaccuracy of IOL power calculation formulas for small eyes, and the difficulty of accurately measuring the biometrics of a child’s eye. In addition, given the fixed position of an IOL in the eye, increasing elongation of the posterior segment of the eye relative to the anterior segment magnifies the myopic shift that occurs with ocular growth. The targeted refractive error in young children undergoing IOL implantation should be an undercorrection in anticipa© 2016 S. Karger AG, Basel tion of a future myopic shift.

The human eye undergoes extensive changes during early childhood, including axial elongation, corneal flattening and a reduced lens power. On a population basis, these changes result in a non-Gaussian distribution of refractive errors clustered near emmetropia that is often referred to as ‘emmetropization.’ Emmetropization is believed

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Normal Ocular Growth in Children

to arise from the ability of an infant’s eye to recognize a defocused retinal image and then to grow by the appropriate amount to bring this image into focus. In addition to visual stimuli, genetic and environmental factors have also been reported to influence ocular growth during childhood [1–3].

Ocular biometrics have been assayed in both longitudinal and cross-sectional studies using ultrasonography, keratometry and cycloplegic retinoscopy in normal infants. Full-term infants have a mean axial length of 16.8–17.0 mm at birth [4–7]. The eye elongates by approximately 3.0 mm during the first year of life [8]. On average, the mean increase in axial length during the first month of life is 0.28 mm. However, the mean rate of axial elongation slows to 0.14 mm/month by age 6 months [8]. Axial growth during childhood is best modeled by the quadratic expression 17.190 + 0.128 × (age in weeks) – 0.0013 × (age in weeks)2 [4]. At birth, the cornea has a mean power of 51 D [6]. However, during the first 2 months of life, the cornea flattens on average by 6 D to a mean corneal power of 45 D. The cornea then flattens by an average of 0.2 D/month until age 1 year. After the first year of life, the power of the cornea usually remains relatively constant [9]. The crystalline lens also flattens during the first year of life, resulting in a reduction in the estimated lens power from 34.4 ± 2.3 D at birth to 26.5 ± 0.6 D at 12 months of age [6].

Rabbit Model Several animal models have been used to study the effect of lensectomy on ocular growth. Kugelberg et al. [10] used a juvenile rabbit model to study the effect of lens aspiration on ocular growth. They initially performed a unilateral lensectomy on 3-week-old rabbits while using the fellow eye as a control. Axial length measurements were obtained preoperatively and at fixed intervals postoperatively using ultrasonography. Eyes that developed glaucoma were excluded from the analyses.

Aphakic eyes were found to be consistently shorter than control eyes. Additional studies were then performed using 2- to 3-week-old rabbits that underwent bilateral lens aspiration coupled with the implantation of either a custom-designed polymethyl methacrylate (PMMA) intraocular lens (IOL) (4.5 mm optic diameter, 7.8 mm overall diameter, +21 D) or a single-piece acrylic IOL (AcrySof SA30AT, Alcon, Fort Worth, Tex., USA; 5.5 mm optic diameter, 13.0 mm overall diameter, +20 D) in one eye [11, 12]. Two months after surgery, the mean axial lengths of aphakic eyes and pseudophakic eyes with acrylic IOLs were similar, whereas pseudophakic eyes with PMMA IOLs were shorter (aphakic, 13.5 mm; acrylic IOL, 13.3 mm; PMMA, 12.5 mm). They concluded that implanting a PMMA IOL, but not an acrylic IOL, reduces ocular growth after lensectomy. They hypothesized that axial elongation may be reduced secondary to stretching of the capsular bag after PMMA IOL implantation.

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Nucci P (ed): Pediatric Cataract.

Dev Ophthalmol. Basel, Karger, 2016, vol 57, pp 29–39 (DOI: 10.1159/000442498)

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Animal Models of Ocular Growth Following Lensectomy

Monkey Model A rhesus monkey model has also been used to evaluate the effect of unilateral lensectomy on ocular growth. Initially, the effect of unilateral lensectomy (mean age, 6 days; range, 0–14 days) was studied and was coupled with optical correction of the aphakic eye with an extended wear contact lens and part-time occlusion of the fellow eye with an occluder contact lens [13]. With this treatment, monkeys (n = 12) had a mean reduction in axial elongation of their aphakic eyes of 2.2 mm (range, 0.4–3.5 mm reduction) after a follow-up period ranging from 8 to 26 months. Later, a monkey model was developed to simulate a unilateral congenital cataract by placing a translucent contact lens on the right eyes of newborn monkeys a few hours after birth (fig. 1) [14, 15]. A lensectomy was then performed on the right eyes 11–16 days later. In some cases, the right eyes were left aphakic and were focused with a contact lens, while in other cases, a monofocal or multifocal PMMA IOL was implanted into the capsular bag. Postoperatively, the left eyes were occluded with an opaque contact lens on a part-time basis to simulate patching therapy. Serial measurements of axial length and intraocular pressure were then performed every 1–2 weeks. Five weeks postoperatively, the axial lengths of the right eyes were significantly shorter than those of the left eyes (mean, –0.7 mm; range, +0.3 to –1.8 mm) [16]. However, the interocular differences in axial length between eyes with multifocal and monofocal IOLs were the same at each time ranges tested, so their data were pooled. By 52 weeks of age, the mean axial lengths of the right eyes were 2.0 mm shorter (range, 0.1 mm longer to 3.7 mm shorter) than those of the left eyes (fig. 2). After 1 year of follow-up, only one of the 20 monkeys in the cohort had a longer axial length in their right eye than in their left eye (fig. 3). However, during the second year of life, the interocular difference in axial length remained relatively unchanged. An even larger effect on axial elongation was noted in aphakic eyes. Since no difference was noted in the axial elongation of the

Ocular Growth after Pediatric Cataract Surgery

Nucci P (ed): Pediatric Cataract.

Dev Ophthalmol. Basel, Karger, 2016, vol 57, pp 29–39 (DOI: 10.1159/000442498)

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Fig. 1. An infant rhesus monkey wearing an opalescent contact lens on his right eye to simulate a unilateral congenital cataract.

0.5

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Fig. 2. Axial length difference between the right and left eyes of the normal (n = 39), monocular aphakia (n = 18), and monocular pseudophakia (n = 20) groups plotted as a function of age.

Printed with permission from Lambert et al. [16].

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Fig. 3. Axial length measurements of the right (OD) and left (OS) eyes plotted as a function of age. For the monkeys presented in the first row (Group 1), a monofocal IOL was implanted into the right eye, and the left eye was untreated. For the monkeys in the second row (Group 2), a monofocal IOL was implanted into the right eye, and the left eye was occluded by 70%. For the monkeys in the third row (Group 3), a multifocal IOL was implanted into the right eye, and the left eye was untreated. For the monkeys in the fourth row (Group 4), a multifocal IOL was implanted into the right eye, and 70% occlusion therapy was applied to the left eye. Printed with permission from Lambert et al. [16].

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Nucci P (ed): Pediatric Cataract.

Dev Ophthalmol. Basel, Karger, 2016, vol 57, pp 29–39 (DOI: 10.1159/000442498)

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aphakic eyes left uncorrected vs. those treated with contact lenses, their data were pooled and analyzed together. At 52 weeks of age, the mean axial length difference between the right and left eyes was 2.3 mm (range, 1.3–4.0 mm), and this difference remained relatively unchanged during the second year of life. In contrast, for control monkeys, the mean interocular axial length difference was minimal (0 or 0.1 mm) for all age ranges studied.

To study the effect of age on the retardation of axial elongation following lensectomy, 4 rhesus monkeys underwent a unilateral lensectomy at age 4 days, 13 days, 7.5 months or 1 year [17]. While a large effect on axial elongation was noted in the monkey that underwent a lensectomy at 4 days of age (fig. 4a), a smaller effect was noted after a unilateral lensectomy at 13 days of age (fig. 4b); almost no effect was noted after a unilateral lensectomy at 7.5 and 12 months of age (fig. 4c, d). Thus, the degree of retardation of axial elongation induced by lensectomy is strongly dependent on age.

Since the visual system of rhesus monkeys matures four times more rapidly than that of humans, a 4-day-old monkey would be equivalent to a 2-week-old neonate, and a 13-day-old monkey would be to a 2-month-old infant [18].

Ocular Growth after Pediatric Cataract Surgery

Nucci P (ed): Pediatric Cataract.

Dev Ophthalmol. Basel, Karger, 2016, vol 57, pp 29–39 (DOI: 10.1159/000442498)

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Fig. 4. Axial length plotted against age for the right and left eyes of monkey RZA6 (a), which underwent a lensectomy at 0.6 weeks of age, monkey RGZ5 (b), which underwent a lensectomy at 1.9 weeks of age, monkey ROW5 (c), which underwent a lensectomy at 32 weeks of age, and monkey RGN5 (d), which underwent a lensectomy at 51 weeks of age. Printed with permission from Lambert [17].

To determine the molecular basis for the retardation of axial elongation after lensectomy, a cohort of infant monkeys underwent a unilateral lensectomy between 4 and 7 days of age [19]. Once the interocular axial length difference was >0.4 mm, the monkeys were sacrificed and scleral gene expression was compared between the treated and fellow eyes. The treated eyes were found to have upregulated expression of genes corresponding to various extracellular matrix proteins, including decorin, biglycan, several collagens and tenascin, as well as cell adhesion, cytoskeletal and cell cycle proteins and downregulated expression of apoptosis genes. These changes were not present after a sham operation, suggesting that physical trauma or inflammation alone was not responsible for these changes. Therefore, it was postulated that ocular growth might be retarded in these eyes secondary to visual blur, the loss of lens-derived growth signals or a combination of both factors. The molecular mechanism underlying these changes was hypothesized to be initiated by the loss of lens-derived soluble signals, resulting in changes in gene expression in the retina and sclera that reduced scleral pliability.

Based on the premise that dopamine and its metabolites are soluble signals that control ocular growth, their levels were assayed in monkeys after a unilateral lensectomy performed 1 week after birth. The animals were then sacrificed when there was an interocular axial length difference >0.4 mm. The levels of dopamine and its metabolites in the central and peripheral retinas were then compared between the treated and untreated eyes. No differences were noted in the peripheral retinas, but the levels of dopamine metabolites were significantly elevated in the central retinas of the treated eyes [20]. These findings suggest that dopamine metabolites may be among the soluble proteins that modulate ocular growth after lensectomy in neonates.

Ocular Growth after Pediatric Cataract Surgery

Aphakia Axial elongation was studied directly in the Infant Aphakia Treatment Study (IATS) using a cohort of children (n = 57) who underwent a unilateral lensectomy between the ages of 1 and 6 months (mean, 1.8 months) [21]. Axial length was measured using ultrasound or optical biometry before cataract surgery and then at ages 12 months and 5 years. During the first year of life, the mean rate of axial elongation was noted to be nearly constant in aphakic eyes (0.17 mm/month) [8]. In contrast, the rate of axial elongation steadily declined in the fellow eyes until age 12 months (fig. 4). At age 5 years, the mean change in axial length relative to baseline prior to cataract extraction was slightly reduced in aphakic eyes compared to the fellow eyes (aphakic, 3.7 mm; fellow, 3.9 mm), but this difference was not statistically significant. Sminia et al. [22]

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Nucci P (ed): Pediatric Cataract.

Dev Ophthalmol. Basel, Karger, 2016, vol 57, pp 29–39 (DOI: 10.1159/000442498)

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In children, axial elongation has been studied both directly and indirectly after cataract extraction with and without IOL implantation.

Pseudophakia Accurately predicting axial elongation is particularly important when an IOL is implanted into a child’s eye. If greater axial elongation than anticipated occurs, it may be necessary to exchange the IOL when the child is older. Alternatively, if less axial elongation than anticipated occurs, the child may need to wear spectacles or contact lenses for hyperopic correction on a long-term basis.

Griener et al. [25] evaluated axial elongation in 11 infants who underwent unilateral cataract surgery and IOL implantation at a mean age of 3 months. After a mean follow-up duration of 5.6 years, 10 of the 11 eyes had less axial elongation in their

Ocular Growth after Pediatric Cataract Surgery

Nucci P (ed): Pediatric Cataract.

Dev Ophthalmol. Basel, Karger, 2016, vol 57, pp 29–39 (DOI: 10.1159/000442498)

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measured baseline axial lengths in 25 children who underwent cataract surgery at a mean age of 4.8 months (range, 0.8–17 months) and then after a mean follow-up duration of 4.3 years (range, 1.0–11.9 years). Nineteen of the children were left aphakic, whereas 6 underwent primary IOL implantation. Mean axial elongation was significantly reduced in the operated eyes by a mean of nearly 0.3 mm compared to the fellow eyes (operated eyes, 2.65 mm; fellow eyes, 2.92 mm; p = 0.049). These findings are consistent with animal studies reporting a retardation of axial elongation after lensectomy, although the magnitude of change was reduced. The smaller effect of lensectomy on the retardation of axial elongation in these two studies compared to animal studies may be related to the older age of these children at the time of cataract surgery.

Indirect studies of axial elongation in aphakic eyes have relied on longitudinal assessments of refractive error to estimate ocular growth. Since the refractive error of aphakic eyes is a function of two variables, axial length and corneal power, and since corneal power remains relatively constant after the first year of life, changes in refractive error have been used as a surrogate for changes in axial length. McClatchey and Parks [23] studied the myopic shift of 146 aphakic eyes that underwent cataract surgery during the first decade of life and for which at least 3 years of follow-up data were available. They found that these children had an average 10 D myopic shift from infancy to adulthood. They noted that children who underwent cataract surgery during the first 3 months of life had reduced myopic shift compared to children who underwent cataract surgery after age 3 months, suggesting that surgery during early infancy retards axial elongation. No other variables, including visual acuity, glaucoma, the type of cataract or laterality, were found to be associated with the rate of myopic shift.

Nystrom et al. [24] studied a small cohort of children (n = 28) who underwent unilateral or bilateral cataract surgery at a median age of 1.6 months. All eyes were left aphakic after cataract surgery. They reported a mean myopic shift of 8.9 D during the first 6 months following cataract surgery, followed by a myopic shift of 2.8 D during the subsequent 6 months. They also noted that a logarithmic model best fit the regression curve for refraction in aphakic eyes. While the study by McClatchey and Parks [23] suggests that there is a smaller myopic shift after early cataract surgery, the difference was relatively small. The study by Nystrom et al. [24] did not study the effect of age on the magnitude of the myopic shift.

pseudophakic eyes than in their fellow eye (mean axial length difference, 0.30 mm).

However, one outlier had greater axial elongation in his pseudophakic eye (1.8 mm).

This patient also had the shortest cataractous eye preoperatively (17.1 mm). This study suggests that while cataract extraction and IOL implantation generally slightly retard axial elongation, other factors may occasionally cause the opposite effect.

Fan et al. [26] evaluated axial elongation in 20 children (bilateral cataracts, n = 14; unilateral cataract, n = 6) who underwent cataract extraction and IOL implantation at a mean age of 6.7 months (range, 3–12 months). Preoperatively, the mean axial length of the cataractous eyes was 0.18 mm shorter than their fellow eyes in children with unilateral cataracts. After a 3 year follow-up period, the cataractous eyes elongated an average of 0.33 mm less than the fellow eyes (cataractous eyes, 2.84 mm; fellow eyes, 3.17 mm). When the eyes undergoing unilateral and bilateral cataract surgery were pooled together, their mean increase in axial length was 2.71 mm. These findings are consistent with animal studies showing less axial growth in eyes that underwent cataract surgery during infancy.

Hussin and Markham [27] evaluated axial elongation in 21 children (bilateral cataracts, n = 9; unilateral cataract, n = 12) who underwent cataract extraction and IOL implantation at a mean age of 4.5 months (range, 3 weeks to 9 months). After a follow-up duration of 5 years or longer, they reported that axial growth after unilateral cataract surgery was similar between the treated and fellow eyes (treated, 5.15 mm; fellow, 5.12 mm). They also reported greater mean axial elongation in eyes that underwent unilateral compared to bilateral cataract surgery (right eyes, 5.44 mm; left eyes 5.72 mm). They concluded that cataract surgery and IOL implantation did not affect axial elongation.

Lambert et al. [8] evaluated axial elongation in 57 infants in the IATS who underwent unilateral cataract extraction and IOL implantation at a mean age of 1.8 months.

The axial elongation of pseudophakic eyes was relatively constant during the first year of life regardless of the age at which cataract surgery was performed. At age 5 years, the change in axial length from baseline was similar between the pseudophakic and fellow eyes (pseudophakic eyes, 4.0 mm; fellow eyes, 3.5 mm) [unpubl. data]. Eyes that developed glaucoma had greater axial elongation than eyes that were normotensive.

Axial length at age 5 years was not correlated with visual outcome (p = 0.34). This study did not show retardation of ocular growth after early cataract surgery and IOL implantation.

McClatchey and Parks [23] reported that the myopic shift that occurs in children after cataract surgery is best described as the change in refraction versus the log of the age span studied. In aphakic eyes, they referred to this semi-log slope as the rate of myopic shift. Since most of the growth of an infant eye occurs in the posterior segment, an IOL implanted during infancy will be farther from the retina as the eye grows, resulting in

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Dev Ophthalmol. Basel, Karger, 2016, vol 57, pp 29–39 (DOI: 10.1159/000442498)

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Rate of Refractive Growth

a larger myopic shift compared to an aphakic eye. To account for the change in IOL position as the eye grows, McClatchey et al. [28] developed a formula that calculates the rate of refractive growth (RRG). The RRG mathematically removed the refractive effect of an IOL so that the refractive changes in pseudophakic eyes can be compared to those in aphakic eyes. In children, the RRG is negative since these eyes are undergoing a myopic shift; the greater the negative value, the greater the myopic shift. McClatchey et al.

[28] made two subsequent refinements to the RRG formula. First, he factored in utero ocular growth to reduce the inherent inaccuracy of the formula near age zero by defining age as the chronological age + 6 months in the formula. This new formula, RRG2, made it possible to more accurately calculate the RRG during the first 3 months of life.

Second, they eliminated the assumption that children wear spectacles at a vertex distance of 12 mm. This was done by mathematically shifting the position of the measured refraction from the spectacle plane to the crystalline lens plane [29]. This new formula, RRG3, was then tested in a cohort of children who underwent cataract surgery with or without IOL implantation. Whereas using the RRG and RRG2 formulas, the mean rate of refractive growth was significantly reduced in children undergoing cataract surgery and IOL implantation at <6 months of age compared to ≥6 months of age, this difference did not quite reach statistical significance using the RRG3 formula (<6 months, –11 ± 4; ≥6 months, –14 ± 7; p = 0.053), suggesting that some of the changes reported using the RRG and RRG2 formulas were spurious. A reduction in the RRG using the RRG3 formula was also noted in aphakic eyes (<6 months, –15 ± 9; ≥6 months, –17 ± 10; p = 0.59), but this difference was also not statistically significant. Thus, while these data suggest that there may be a reduced myopic shift in infants undergoing cataract surgery during the first 6 months of life, consistent with a reduction in axial elongation in these eyes, this difference was not statistically significant.

In addition to ocular elongation, the targeted refractive error and the prediction error impact the actual refractive error resulting from cataract extraction and IOL implantation in children. Some general ophthalmologists target emmetropia or low myopia when implanting IOLs in children based on the assumption that this will reduce the risk of these eyes developing amblyopia. However, later in childhood, many of these eyes become highly myopic and must be corrected with high-minus contact lenses or glasses or must undergo an IOL exchange or corneal refractive surgery. In addition, there is no empirical evidence that this approach improves visual outcome [30]. Pediatric ophthalmologists generally target an undercorrection based on the premise that a child’s eye will continue to elongate after cataract surgery and that it is better for this eye to be near emmetropia when the eye is fully grown rather than to be highly myopic [31–33]. The magnitude of the undercorrection is usually based on the age of the child, but other factors, such as the refractive error of the fellow eye and the parents, must also be considered.

Ocular Growth after Pediatric Cataract Surgery

Nucci P (ed): Pediatric Cataract.

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Targeted Refractive Error and Prediction Error after Intraocular Lens Implantation

IOL implantation during childhood is associated with a much larger prediction error than that after adult cataract surgery. This larger prediction error is likely due to many factors, including inherent errors in IOL power formulas developed for adultsized eyes, inaccurate axial length and keratometry measurements, and the increased difficulty of implanting an IOL into a child’s eye [34]. For these reasons, the median absolute prediction error can exceed 3.0 D with certain IOL power formulas. Even the best IOL power formulas for pediatric eyes have median absolute prediction errors exceeding 1.0 D [35]. A large absolute prediction error further complicates the prediction of the optimal IOL power for implantation into a child’s eye.

Conclusions

Animal studies have consistently shown a large reduction in axial elongation after neonatal lens extraction. While several studies have shown a small reduction in axial elongation after neonatal lens extraction in children, this effect is less robust in children than in animal models. This difference may reflect the older age of children when they undergo cataract surgery compared to animal models of lensectomy. There is also tremendous variability between individual patients, making it difficult to predict the magnitude of axial elongation at the time of cataract surgery. This is less of an issue if the eye is left aphakic but is of paramount concern when an IOL is implanted into the eye during infancy or early childhood.

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2 Jones LA, Sinnott LT, Mutti DO, Mitchell GL, Moeschberger ML, Zadnik K: Parental history of myopia, sports and outdoor activities, and future myopia. Invest Ophthalmol Vis Sci 2007;48:3524–3532.

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5 Fledelius HC, Christensen AC: Reappraisal of the human ocular growth curve in fetal life, infancy, and early childhood. Br J Ophthalmol 1996;80:918–921.

6 Gordon RA, Donzis PB: Refractive development of the human eye. Arch Ophthalmol 1985; 103: 785– 789.

7 Manzitti E, Gamio S, Damel A, Benozzi J: Eye length in congenital cataracts; in Cotlier E, Taylor DS, Lambert SR (eds): Congenital Cataracts. Georgetown, RG Landes, 1994.

8 Lambert SR, Lynn MJ, DuBois LG, Cotsonis GA, Hartmann EE, Wilson ME: Axial elongation following cataract surgery during the first year of life in the infant aphakia treatment study. Invest Ophthalmol Vis Sci 2012;53:7539–7545.

9 Russell B, Ward MA, Lynn M, Dubois L, Lambert SR: The infant aphakia treatment study contact lens experience: one-year outcomes. Eye Contact Lens 2012;38:234–239.

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Scott R. Lambert, MD Department of Ophthalmology School of Medicine, Emory University 1365-B Clifton Rd, Atlanta, GA 30322 (USA) E-Mail slamber @ emory.edu

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14 Lambert SR, Fernandes A, Grossniklaus H, DrewsBotsch C, Eggers H, Boothe RG: Neonatal lensectomy and intraocular lens implantation: effects in rhesus monkeys. Invest Ophthalmol Vis Sci 1995;36:300–310.

15 Lambert SR, Fernandes A, Drews-Botsch C, Boothe RG: Multifocal versus monofocal correction of neonatal monocular aphakia. J Pediatr Ophthalmol Strabismus 1994;31:195–201.

16 Lambert SR, Fernandes A, Drews-Botsch C, Tigges M: Pseudophakia retards axial elongation in neonatal monkey eyes. Invest Ophthalmol Vis Sci 1996;37: 451–458.

17 Lambert SR: The effect of age on the retardation of axial elongation following a lensectomy in infant monkeys. Arch Ophthalmol 1998;116:781–784.

18 Boothe RG, Dobson V, Teller DY: Postnatal development of vision in human and nonhuman primates.

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19 Tarnuzzer RW, Fernandes A, Iuvone PM, Lambert SR: Neonatal aphakia retards ocular growth and alters scleral gene expression in rhesus monkeys. Mol Vis 2005;11:36–49.

20 Iuvone PM, Haque R, Fernandes A, Lambert SR: Neonatal aphakia is associated with altered levels of dopamine metabolites in the non-human primate retina. Exp Eye Res 2015;140:187–189.

21 Lambert SR, Buckley EG, Drews-Botsch C, DuBois L, Hartmann E, Lynn MJ, Plager DA, Wilson ME: The infant aphakia treatment study: design and clinical measures at enrollment. Arch Ophthalmol 2010; 128:21–27.

22 Sminia ML, de Faber JT, Doelwijt DJ, Wubbels RJ, Tjon-Fo-Sang M: Axial eye length growth and final refractive outcome after unilateral paediatric cataract surgery. Br J Ophthalmol 2010;94:547–550.