Refractive Growth of the Crystalline Lens in the Infant Aphakia Treatment Study.

Objective: To compare the rate of refractive growth (RRG3) of the crystalline lens ("lens") versus the eye excluding the lens ("globe") for the fellow, noncataractous eyes of participants in the Infant Aphakia Treatment Study. Design: Retrospective cohort study. Subjects: A total of 114 children who had unilateral cataract surgery as infants were recruited. Biometric and refraction data were obtained from the normal eyes at surgery and at 1, 5, and 10 years. Subjects were included if complete data (axial length [AL], corneal power, and refraction) were available at surgery and at 10 years of age. Methods: At surgery and at 1, 5, and 10 years, AL, corneal power, and cycloplegic refraction were measured in the normal eyes. For each eye, the RRG3 was defined by linear regression of refraction at the intraocular lens (IOL) plane against log10 (age + 0.6 years). The RRG3 for the globe was based on IOL power for emmetropia; the RRG3 for the lens was based on IOL power calculated to give the observed refractions. Intraocular lens powers were calculated with the Holladay 1 formula. The means were compared with a paired 2-tailed t test, and linear regression was used to look for a correlation between RRG3 of the lens globe. Main Outcome Measures: The RRG3 of the lens and globe. Results: Complete data were available for 107 normal eyes. The mean RRG3 of the lenses was -12.0 ± 2.5 diopters (D) and the mean RRG3 of the globes was -14.1 ± 2.7 D (P < 0.001). The RRG3 of the lens correlated with the RRG3 of the globe (R 2  = 0.25, P < 0.001). Conclusions: The RRG3 was 2 D more negative in globes compared with lenses in normal eyes. Globes with a greater rate of growth tended to have lenses with a greater rate of growth.

The contribution of intraocular lens calculation accuracy to the refractive error predicted at 10 years in the Infant Aphakia Treatment Study.

PURPOSE: To determine the relative contribution of intraocular lens (IOL) calculation accuracy and ocular growth variability to the long-term refractive error predicted following pediatric cataract surgery. METHODS: Pseudophakic eyes of children enrolled in the Infant Aphakia Treatment Study (IATS) were included in this study. Initial absolute prediction error (APE) and 10-year APE were calculated using the initial biometry, IOL parameters, postoperative refractions, and mean rate of refractive growth. The cohort was divided into children with a low-initial APE (≤1.0 D) and a high-initial APE ( >1.0 D). The 10-year APE was compared between the two groups using the Mann-Whitney U test. Linear regression was used to estimate the variability in prediction error explained by the initial IOL calculation accuracy. RESULTS: Forty-two children with IOL placement in infancy were included. Seventeen eyes had a low initial APE, and 25 eyes had a high initial APE. There was no significant difference in APE 10 years following surgery between individuals with a low initial APE (median, 2.67 D; IQR, 1.61-4.12 D) and a high initial APE (median, 3.45 D; IQR, 1.64-5.10 D) (P = 0.7). Initial prediction error could explain 12% of the variability in the prediction error 10 years following surgery. CONCLUSIONS: IOL calculation accuracy contributed minimally to the refractive error predicted 10 years after cataract surgery in the setting of high variability in the rate of refractive growth.

Effective lens position and pseudophakic refraction prediction error at 10½ years of age in the Infant Aphakia Treatment Study.

BACKGROUND: The refraction prediction error (PE) for infants with intraocular lens (IOL) implantation is large, possibly related to an effective lens position (ELP) that is different than in adult eyes. If these eyes still have nonadult ELPs as they age, this could result in persistently large PE. We aimed to determine whether ELP or biometry at age 10½ years correlated with PE in children enrolled in the Infant Aphakia Treatment Study (IATS). METHODS: We compared the measured refraction of eyes randomized to primary IOL implantation to the "predicted refraction" calculated by the Holladay 1 formula, based on biometry at age 10½ years. Eyes with incomplete data or IOL exchange were excluded. The PE (predicted - measured refraction) and absolute PE were calculated. Measured anterior chamber depth (ACD) was used to assess the effect of ELP on PE. Multiple regression analysis was performed on absolute PE versus axial length, corneal power, rate of refractive growth, refractive error, and best-corrected visual acuity. RESULTS: Forty-three eyes were included. The PE was 0.63 ± 1.68 D; median absolute PE, 0.85 D (IQR, 1.83 D). The median absolute PE was greater when the measured ACD was used to calculate predicted refraction instead of the standard A-constant (1.88 D [IQR, 1.72] D vs 0.85 D [IQR, 1.83], resp. [P = 0.03]). Absolute PE was not significantly correlated with any other parameter. CONCLUSIONS: Variations in ELP did not contribute significantly to PE 10 years after infant cataract surgery.

The accuracy of intraocular lens calculation varies by age in the Infant Aphakia Treatment Study.

Refraction predictions from intraocular lens (IOL) calculation formulae are inaccurate in children. We sought to quantify the relationship between age and prediction error using a model derived from the biometry measurements of children enrolled in the Infant Aphakia Treatment Study (IATS) when they were ≤7 months of age. We calculated theoretical predicted refractions in diopters (D) using axial length, average keratometry, and IOL powers at each measurement time point using the Holladay 1 formula. We compared the predicted refraction to the actual refraction and calculated the absolute prediction error (APE). We found that the median APE was 1.60 D (IQR, 0.73-3.11 D) at a mean age (corrected for estimated gestational age) of 0.20 ± 0.14 years and decreased to 1.11 D (IQR, 0.42-2.20 D) at 10.60 ± 0.27 years. We analyzed the association of age with APE using linear mixed-effects models adjusting for axial length, average keratometry, and IOL power and found that as age doubled, APE decreased by 0.25 D (95% CI, 0.09-0.40 D). The accuracy of IOL calculations increases with age, independent of biometry measurements and IOL power.

Refractive growth variability in the Infant Aphakia Treatment Study.

PURPOSE: Prediction of refraction after cataract surgery in children is limited by the variance in rate of refractive growth (RRG3). This study compared RRG3 in aphakic and pseudophakic eyes with their fellow, normal eyes in the Infant Aphakia Treatment Study. SETTING: Twelve clinical sites in the United States. DESIGN: Randomized clinical trial. METHODS: Infants randomized to unilateral cataract extraction had RRG3 calculated based on biometric data (axial length and keratometry) at cataract surgery and at 10 years of age, for both the normal and cataract eyes. Subjects were included if complete biometric data from both eyes were available both at surgery and at 10 years. Variance in RRG3 was compared between the groups with Pitman test for equality of variance between correlated samples. RESULTS: Longitudinal biometric data were available for 103 of the 114 patients enrolled. RRG3 was -15.00 diopters (D) (3.00 D) for normal eyes (reported as mean [SD]), -17.70 D (6.20 D) for aphakic eyes, and -16.70 D (6.20 D) for pseudophakic eyes (P < .0001 for comparison of variances in RRG3 between normal and all operated eyes). Further analysis found differences in the variance in axial length growth (P < .0001) between operated and normal eyes; the variance in keratometry measurement change did not reach significance. CONCLUSIONS: The standard deviation in the RRG3 of normal eyes in our study was half of that found in eyes that underwent cataract surgery.

Comparison of the rate of refractive growth in aphakic eyes versus pseudophakic eyes in the Infant Aphakia Treatment Study.

PURPOSE: To compare the rate of refractive growth (RRG) between aphakic eyes and pseudophakic eyes in the Infant Aphakia Treatment Study (IATS). SETTING: Twelve clinical sites across the United States. DESIGN: Randomized clinical trial. METHODS: Patients randomized to unilateral cataract extraction with contact lens correction versus intraocular lens (IOL) implantation in the IATS had their rate of refractive growth (RRG3) calculated based on the change in refraction from the 1-month postoperative examination to age 5 years. The RRG3 is a logarithmic formula designed to calculate the RRG in children. Two-group t tests were used to compare the mean refractive growth between the contact lens group and IOL group and outcomes based on age at surgery and visual acuity. RESULTS: Longitudinal refractive data were studied for 108 of 114 patients enrolled in the IATS (contact lens group, n = 54; IOL group, n = 54). The mean RRG3 was similar in the contact lens group (-18.0 diopter [D] ± 11.0 [SD]) and the IOL group (-19.0 ± 9.0 D) (P = .49). The RRG3 value was not correlated with age at cataract surgery, glaucoma status, or visual outcome in the IOL group. In the aphakia group, only visual outcome was correlated with refractive growth (P = .01). CONCLUSIONS: Infants' eyes had a similar rate of refractive growth after unilateral cataract surgery whether or not an IOL was implanted. A worse visual outcome was associated with a higher RRG in aphakic, but not pseudophakic, eyes. FINANCIAL DISCLOSURE: None of the authors has a financial or proprietary interest in any material or method mentioned.

Slipping the knot: a comparison of knots used in adjustable suture strabismus surgery.

PURPOSE: To evaluate the frictional force created by different knots used in adjustable suture strabismus surgery. METHODS: To allow the simulation of strabismus surgery suture tying methods a model using 6-0 polyglactin 910 suture was created. Three different knots were evaluated: (1) the sliding noose knot with a double wrap of suture, (2) the cinch knot with a single throw on both sides of the pole suture, (2) and a single-throw square knot. (Bow-tie knots were not included.) A digital force meter was used to measure the force (gram-force [gf]) required to overcome the static friction created by the knot. Each simulation was repeated with new suture material 5 times and the force required after subsequent repositioning was also recorded. RESULTS: The force to overcome static friction of the sliding noose knot was 240 gf [95% CI, 187-284 gf]; of the cinch knot, 150 gf [95% CI, 123-167 gf]; and of the square knot, 110 gf [95% CI, 95-121 gf]. Subsequent movement of each knot along the same suture required progressively less force, with the sliding noose maintaining the most static friction. CONCLUSIONS: The sliding noose knot generates the most frictional force and also maintains the most friction after subsequent repositioning. Important consideration should be given to multiple repositioning movements, because the force required for each subsequent repositioning decreases.

A case of familial exudative vitreoretinopathy identified after genetic testing.

We report the case of a 21-month-old girl who was found to have familial exudative vitreoretinopathy after genetic testing revealed a genetic deletion at 7q22. She had previously been followed for exotropia; however, fundus examinations in the office were thought to be normal. After the pediatric geneticist identified the link between 7q22 deletions and vitreoretinopathies an examination under anesthesia was performed. Fluorescein angiography during this examination confirmed the presence of avascular areas of the retina.

Reanalysis of refractive growth in pediatric pseudophakia and aphakia.

BACKGROUND: The current model of refractive growth in children (RRG2) is calculated as the slope of aphakic refraction at the spectacle plane versus the logarithm of adjusted age. However, this model fails in infants because of the optical effect of vertex distance of a spectacle lens on the effective power at the cornea. In this study, we developed a new model of refractive growth (RRG3) that eliminates the optical effect of vertex distance on the RRG2 model. METHODS: We calculated RRG3 values for pseudophakic and aphakic eyes previously analyzed for RRG2. Inclusion criteria were age ≤10 years at the time of cataract surgery and follow-up time between measured refractions of at least 3.6 years and at least the age at first refraction plus 0.6 years. For both pseudophakic and aphakic eyes, we compared RRG3 values in children who had cataract surgery before age 6 months with those in children aged 6 months or older. RESULTS: A total of 78 pseudophakic and 70 aphakic eyes met the inclusion criteria. Ages at surgery ranged from 0.25 to 9 years, with a 9.5-year mean follow-up time. The mean RRG3 value was not significantly different between the surgical age groups for both pseudophakic eyes (P = 0.053) and aphakic eyes (P = 0.59). CONCLUSIONS: The RRG3 values were not significantly different between the surgical age groups for both pseudophakic and aphakic eyes. Consequently, RRG3 is theoretically applicable even in the small eyes of infants having surgery before 6 months of age.

Intraocular lens power calculation for humanitarian missions based on partial biometry.

PURPOSE: To determine whether the correlation between corneal power (K) and axial length (AL) can be used for intraocular lens (IOL) power calculation when biometric data are incomplete. SETTING: Developing regions served by United States Navy humanitarian assistance missions. DESIGN: Case series. METHODS: Measurements of K and AL were collected from all adult cataract surgery charts and used to calculate emmetropic IOL powers. A formula for estimating K or AL was derived by Deming regression analysis. The emmetropic IOL powers were calculated by hypothetical scenarios as follows: (1) K estimated from the formula and measured AL, (2) mean population K and measured AL, (3) measured K and estimated AL, and (4) measured K and mean population AL. The mean absolute refractive error (MAE) was calculated for each hypothetical scenario and an additional scenario (scenario 5) using single IOL power for all eyes. The MAEs were compared with a paired t test. RESULTS: The formula derived from Deming regression analysis was K = 74.56 - 1.317 × AL. The MAE for the scenarios were (1) 0.90 diopters (D), (2) 1.11 D, (3) 1.91 D, (4) 1.55 D, and (5) 1.22 D. The MAE for scenario 1 was significantly less (P<.01) than that for scenarios 2 and 5. The MAE for scenario 5 was significantly less than that for scenarios 3 and 4. CONCLUSIONS: The correlation between K and AL can be used to improve accuracy of IOL calculation when K is unavailable. When the AL is unavailable, the mean population IOL power is most accurate. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

Predictability of intraocular lens calculation and early refractive status: the Infant Aphakia Treatment Study.

OBJECTIVE: To report the accuracy of intraocular lens (IOL) power calculations and the early refractive status in pseudophakic eyes of infants in the Infant Aphakia Treatment Study. METHODS: Eyes randomized to receive primary IOL implantation were targeted for a postoperative refraction of +8.0 diopters (D) for infants 28 to 48 days old at surgery and +6.0 D for those 49 days or older to younger than 7 months at surgery using the Holladay 1 formula. Refraction 1 month after surgery was converted to spherical equivalent, and prediction error (PE; defined as the calculated refraction minus the actual refraction) and absolute PE were calculated. Baseline eye and surgery characteristics and A-scan quality were analyzed to compare their effect on PE. MAIN OUTCOME MEASURES: Prediction error. RESULTS: Fifty-six eyes underwent primary IOL implantation; 7 were excluded for lack of postoperative refraction (n = 5) or incorrect technique in refraction (n = 1) or biometry (n = 1). Overall mean (SD) absolute PE was 1.8 (1.3) D and mean (SD) PE was +1.0 (2.0) D. Absolute PE was less than 1 D in 41% of eyes but greater than 2 D in 41% of eyes. Mean IOL power implanted was 29.9 D (range, 11.5-40.0 D); most eyes (88%) implanted with an IOL of 30.0 D or greater had less postoperative hyperopia than planned. Multivariate analysis revealed that only short axial length (<18 mm) was significant for higher PE. CONCLUSIONS: Short axial length correlates with higher PE after IOL placement in infants. Less hyperopia than anticipated occurs with axial lengths of less than 18 mm or high-power IOLs. Application to Clinical Practice Quality A-scans are essential and higher PE is common, with a tendency for less hyperopia than expected. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00212134.

Competency checklists for strabismus surgery and retinopathy of prematurity examination.

PURPOSE: To evaluate two checklist tools that are designed to guide, document, and assess resident training in strabismus surgery and examination of infants at risk for retinopathy of prematurity (ROP). METHODS: A panel of staff surgeons from several teaching institutions evaluated the checklists and provided constructive feedback. All former residents who had been trained via the use of these checklist tools were asked to take self-assessment surveys on competency in strabismus surgery and ROP examination. A Likert 5-point scale was used for all evaluations, with 1 being the lowest rating and 5 the highest rating. RESULTS: Six experts in strabismus and seven in ROP rated the checklists. Their comments were used to revise the checklists, which were sent to the same group for reevaluation. The mean Likert score for the final checklists was 4.9 of 5.0 for both checklists. Of 16 former residents, 9 responded to the self-assessments with a mean overall score of 4.1 (of 5.0) for strabismus surgery and 3.9 for ROP examination. CONCLUSIONS: These checklist tools can be used to assess the quality of a resident's training and experience in these specific ophthalmology skills. They are complementary to other curriculum and assessment tools and can serve to organize the educational experience while ensuring a uniformity of training.

The optics of aphakic and pseudophakic eyes in childhood.

The growth of the eye results in a myopic shift in aphakic and pseudophakic eyes during childhood. Cataract surgery after the age of 6 months, with or without lens implantation, appears to have little effect on the rate of refractive growth. Most children with pseudophakia have a large amount of myopic shift. This myopic shift is greatest in children with surgery at younger ages. It is also greater in eyes with high-power intraocular lenses due to an optical phenomenon analogous to the effect of vertex distance. The amount of myopic shift and the variance in rate of refractive growth can be predicted using an empiric, logarithmic model. We describe a revision of this logarithmic model to extend it patients with surgery before 3 months of age. We also analyze the variance in the rate of refractive growth, based on data from pseudophakic children with the longest follow-up in proportion to age.

Theoretical strategy for choosing piggyback intraocular lens powers in young children.

INTRODUCTION: The normal growth of a young child's pseudophakic eye can result in a large myopic shift. Temporary polypseudophakia using piggyback intraocular lenses (IOLs) has been proposed as a means to reduce the amount of myopic shift by removing the anterior IOL when the eye becomes sufficiently myopic. Since the rate of refractive growth can be used to predict the refractive curve over time in pseudophakic children, we used this knowledge to develop a theoretical strategy for choosing IOL power combinations for temporary polypseudophakia. METHODS: We used a novel Pediatric Piggyback IOL Calculator to develop a strategy for choosing the powers of the anterior and posterior IOLs. We graphed the predicted results for several combinations of piggyback IOL powers and chose the combination of IOL powers that appeared to give the best results, based on the known rate of refractive growth (5.4 D) and its standard deviation (2.4 D). We aimed for a combination to minimize the hyperopic or myopic refractive error during the first 6 years of life to facilitate amblyopia management and minimize the refractive error at age 20 years. RESULTS: We found optimal results when the initial postoperative goal refraction with polypseudophakia was moderate hyperopia and the anterior IOL had approximately 20% of the total required IOL power. CONCLUSIONS: This theoretical strategy can be used to determine piggyback IOL powers to use in children.

Intraocular lens power requirements for humanitarian missions.

PURPOSE: To develop a generalized method to determine an optimum set of intraocular lens (IOL) powers for humanitarian missions. SETTING: Humanitarian missions to Central America, South America, and Southeast Asia. METHODS: Biometric data of adults who had cataract surgery on 2 humanitarian missions were reviewed, and the ideal emmetropic IOL power for each eye was calculated. Using statistical modeling, the number of extra IOLs required at each power to account for natural variation inherent in random population samples was calculated. To limit the total number of IOLs and maximize availability of suitable IOLs for each patient, a tolerance strategy for choosing IOL powers was developed and the ideal proportion of extra IOLs required at each power was empirically determined. RESULTS: Data of 103 patients were reviewed. The mean IOL power was 20.38 diopters (D) +/- 2.32 (SD). Applying a tolerance strategy to accept IOLs with powers 0.5 D below or 1.0 D above the emmetropic IOL power, the number of extra IOLs required at each power was decreased to a fraction of the fourth root of the number of eyes anticipated to require that IOL power. The model predicted that with this strategy, fewer than 2% of all patients would be rejected due to lack of an IOL with a suitable power. CONCLUSIONS: The spreadsheet-based IOL power prediction model calculated an ideal distribution of IOLs to order for humanitarian cataract surgery. It is generalizable to missions of any size and should help planners minimize costs while ensuring excellent refractive outcomes.

The association between myopic shift and visual acuity outcome in pediatric aphakia.

PURPOSE: The advent of intraocular lens implantation after pediatric cataract surgery necessitates an increased understanding of refractive development. The significant variation in rate and amount of refractive change among eyes, both aphakic and pseudophakic, is well recognized, although the causes of such variation remain unclear. The purpose of this study was to determine if a correlation exists between the rate of refractive growth (RRG) and visual acuity outcome in pediatric aphakia. METHODS: Multicenter, retrospective observational case series. One hundred and twenty-five eyes of 85 patients with cataract surgery before 1 year of age and a minimum of 3 years of follow-up were analyzed. RRG was calculated for each eye using the logarithmic model of ocular growth and compared with final logMAR acuity using linear regression. RESULTS: The correlation of RRG with final logMAR acuity was statistically significant (r(2) = 0.10; P <.01), ie, 10% of variance in RRG is related to acuity outcome. The correlation was higher in unilaterally aphakic patients (n = 44; r(2) = 0.19; P <.01) than in bilaterally aphakic patients (n = 81; r(2) = 0.08; P <.01). Eyes with visual acuity of 20/60 or better had a significantly lower RRG than those with poorer acuity (4.1 v 5.4 diopters (D); P <.01). CONCLUSIONS: RRG in aphakia is correlated with visual acuity outcome. Eyes with poorer acuity have a greater RRG.