Discrepancies between Intraocular Lens Implant Power Prediction Formulas in Pediatric Patients

Intraocular lens calculation using the ESCRS online calculator in pediatric eyes undergoing lens extraction

PURPOSE

To evaluate the ESCRS online calculator for intraocular lens (IOL) calculation in children undergoing lens extraction and primary IOL implantation.

SETTING

Department of Ophthalmology, Goethe-University Frankfurt, Frankfurt am Main, Germany.

DESIGN

Retrospective, consecutive case series.

METHODS

Eyes that received phacoemulsification and IOL implantation (Acrysof SN60AT) due to congenital or juvenile cataract were included. We compared the mean prediction error (MPE), mean and median absolute prediction error (MAE, MedAE) of formulas provided by the recently introduced online calculator provided by the ESCRS with the SRK/T formula, as well as the number of eyes within ±0.5 diopters (D), ±1.0 D, ±2.0 D of target refraction. Postoperative spherical equivalent was measured by retinoscopy 4 to 12 weeks postoperatively.

RESULTS

60 eyes from 47 patients with a mean age of 6.5 ± 3.2 years met the inclusion criteria. Mean axial length was 22.27 ± 1.19 mm. Mean preoperative spherical equivalent (SE) was -0.25 ± 3.78 D, and mean postoperative SE was 0.69 ± 1.53 D. The MedAE was lowest in the SRK/T formula (0.56 D, ± 1.03) performed significantly better ( P = .037) than Hoffer QST and Kane, followed by BUII (0.64 D, ± 0.92), Pearl DGS (0.65 D, ± 0.94), EVO (0.69 D, ± 0.94), Hoffer QST (0.75 D, ± 0.99), and Kane (0.78 D, ± 0.99). All of those were significantly above zero ( P < .001). 41 eyes received an intraoperative optic capture (68%). When excluding eyes that did not receive intraoperative optic capture (n = 19; 32%), the MedAE was shown to be lower.

CONCLUSIONS

Using modern IOL calculation formulas provided by the ESCRS calculator provides good refractive predictability and compares for most of the formulas with the results with SRK/T. In addition, the formulas seem to anticipate the postoperative refraction better for eyes that receive a posterior optic capture.

Predictive Accuracy of the Hill-RBF 2.0 Formula in Pediatric Eyes: Comparison of 5 Intraocular Lens Formulas

PURPOSE

To compare the predictive accuracy of the Hill-Radial Basis Function (Hill-RBF) 2.0 formula with the Barrett Universal II, Hoffer Q, SRK/T, and Holladay 1 formulas in pediatric eyes.

METHODS

In this observational study, 99 eyes of 70 children 4 to 18 years old with clinically significant congenital or developmental cataracts attending the pediatric ophthalmology clinic in Guru Nanak Eye Centre were included. Optical biometry was performed in all patients with the Lenstar LS-900 (Haag-Streit). Intraocular lens (IOL) power predicted by the Hill-RBF formula was selected. Mean absolute prediction error (MAE) at 8 weeks of follow-up was calculated for the Hill-RBF, Barrett Universal II, Hoffer Q, SRK/T, and Holladay 1 IOL power formulas. Percentages of eyes having residual refraction within ±0.50, ±0.50 to ±1.00, and greater than ±1.00 diopters (D) of target refraction were calculated.

RESULTS

The MAEs were 1.08 ± 1.00 D for the Hill-RBF, 1.24 ± 1.20 D for the Barrett Universal II, 1.25 ± 1.06 D for the Hoffer Q, 1.25 ± 1.10 D for the SRK/T, and 1.28 ± 1.01 D for the Holladay 1 formulas. The Hill-RBF formula had the lowest MAE, which was significantly lower than the Holladay 1 and Hoffer Q formulas. However, the difference in MAE between the Hill-RBF and the SRK/T and Barrett Universal II formulas was not statistically significant (P > .05). The Hill-RBF group had the maximum percentage of eyes with residual error within ±0.50 D of the target refraction.

CONCLUSIONS

The overall evidence from the studies indicates that the Hill-RBF method that uses artificial intelligence and works independent of specific anatomical features is non-inferior to the Barrett Universal II, Hoffer Q, SRK/T, and Holladay 1 formulas in pediatric eyes. [J Pediatr Ophthalmol Strabismus. 20XX;X(X):XX-XX.].

Accuracy of Intraocular Lens Power Calculation Formulas in Patients With Multifocal Intraocular Lens Implantation With Optic Capture in Berger Space for Pediatric Cataract

PURPOSE

To assess the accuracy of intraocular lens (IOL) calculation formulas in pediatric patients with multifocal IOL implantation with optic capture in Berger space.

METHODS

This prospective observational study enrolled 68 children (101 eyes), aged 3 to 14 years, who received multifocal IOL (Tecnis ZMB00; Abbott Medical Optics) implantation with optic capture in Berger space from June 2019 to June 2020 in Qingdao Eye Hospital. Ocular biometry was performed using the IOLMaster 700 (Carl Zeiss Meditec). The IOL power and intended postoperative refraction were calculated using the Hoffer Q, Barrett Universal II, Holladay, Holladay2, SRK/T, Haigis, and SRKII formulas. The refractive state of patients, prediction error, and absolute prediction error were evaluated.

RESULTS

The mean absolute error of the formulas was significantly different (0.49 diopters [D], Hoffer Q; 0.52 D, Barrett Universal II; 0.47 D, Holladay; 0.54 D, Holladay2; 0.52 D, SRK/T; 0.67 D, Haigis; 0.99 D, SRKII; P < .001). However, the Hoffer Q, Barrett Universal II, Holladay, Holladay2, and SRK/T formulas had a similar accuracy in predicting refractive error within ±0.50 D (62.4%, 59.4%, 62.4%, 62.4%, and 58.4%). There was a trend toward a greater prediction error in eyes with a shorter axial length (≤ 22 mm) or a steeper cornea (> 43.50 D), for which the Hoffer Q and Holladay2 formulas were more accurate. When the axial length was greater than 22 mm or the corneal curvature was 43.50 D or less, the Holladay, Hoffer Q, and Barrett Universal II formulas were more accurate.

CONCLUSIONS

For patients with pediatric cataract treated with multifocal IOL implantation with optic capture in Berger space, the Hoffer Q, Barrett Universal II, Holladay, Holladay2, and SRK/T formulas performed better than the other formulas. [J Pediatr Ophthalmol Strabismus. 20XX;X(X):XX-XX.].

Challenges in pediatric cataract surgery: comparison of intraocular lens power calculation formulas using optical biometry

PURPOSE

Comparison of the accuracy of intraocular lens (IOL) power calculation formulas (SRK II, SRK/T, Holladay 1, Hoffer Q and Barrett II Universal, Haigis) in pediatric cataract surgery using optical biometry.

METHOD

This prospective study included seventy eyes of 70 patients between ages of 3-15 who had undergone cataract surgery with IOL implantation. Anterior segment parameters and axial length (AL) were measured with an optical biometer. Barrett II Universal formula results were used to determine the diopter of implanted IOL. Postoperative refraction was taken at first month, and differences from the estimated refractive value [mean absolute predictive error (APE)] were compared between formulas. Formulas were also compared according to AL.

RESULTS

The lowest APE was achieved with Barrett II formula (0.64 ± 0.73D) and the highest with Haigis formula (1.06 ± 0.84D) in the whole study population (p < 0.01). APE values were lowest with Holladay 1 (0.79 ± 0.71D) and highest with Haigis (1.44 ± 0.92D) in patients with an AL ≤ 22 mm; lowest APE was achieved with Barrett II (0.47 ± 0.54D) and highest with Haigis (0.84 ± 0.72D) in patients with an AL > 22 mm.

CONCLUSION

Barrett II formula had the best results in eyes with average AL, and SRK/T and Holladay 1 formulas were better in eyes with shorter AL. Haigis formula statistically had the highest predictive error in all formulas.

Accuracy of Intraocular Lens Power Calculation Formulas in Pediatric Cataract Patients: A Systematic Review and Meta-Analysis

Background: Among the various intraocular lens (IOL) power calculation formulas available in clinical settings, which one can yield more accurate results is still inconclusive. We performed a meta-analysis to compare the accuracy of the IOL power calculation formulas used for pediatric cataract patients.

Methods: Observational cohort studies published through April 2021 were systematically searched in PubMed, Web of Science, and EMBASE databases. For each included study, the mean differences of the mean prediction error and mean absolute prediction error (APE) were analyzed and compared using the random-effects model.

Results: Twelve studies involving 1,647 eyes were enrolled in the meta-analysis, and five formulas were compared: Holladay 1, Holladay 2, Hoffer Q, SRK/T, and SRK II. Holladay 1 exhibited the smallest APE (0.97; 95% confidence interval [CI]: 0.92–1.03). For the patients with an axial length (AL) less than 22 mm, SRK/T showed a significantly smaller APE than SRK II (mean difference [MD]: −0.37; 95% CI: −0.63 to −0.12). For the patients younger than 24 months, SRK/T had a significantly smaller APE than Hoffer Q (MD: −0.28; 95% CI: −0.51 to −0.06). For the patients aged 24–60 months, SRK/T presented a significantly smaller APE than Holladay 2 (MD: −0.60; 95% CI: −0.93 to −0.26).

Conclusion: Due to the rapid growth and high variability of pediatric eyes, the formulas for IOL calculation should be considered according to clinical parameters such as age and AL. The evidence obtained supported the accuracy and reliability of SRK/T under certain conditions.

Systematic Review Registration: PROSPERO, identifier: INPLASY202190077.

Intraocular lens power calculation formula in congenital cataracts: Are we using the correct formula for pediatric eyes?

The major challenge these days in pediatric cataract surgery is not the technique of surgery or intraocular lens (IOL) used but the postoperative refractive error. Amblyopia occurring due to postoperative refractive error which the child has; destroys the benefit obtained by a near-perfect and timely surgery. Even if we settle the debate as to what should be the ideal postoperative target refraction, there is a postoperative surprise that is not explained by our conventional insights of an accurate power calculation in children. The role of IOL power calculation formulae in affecting the postoperative refractive error should not be underestimated. Therefore, which age-appropriate formula is to be used for children is unclear. This review is an update on major IOL power calculation formulas used in pediatric eyes. We have tried to define why we should not be using these formulas made for adult eyes and review the literature in this regard.

Comparison of the Accuracy of IOL Power Calculation Formulas for Pediatric Eyes in Children of Different Ages

Purpose

This study aims to compare the accuracy of five intraocular lens (IOL) power calculation formulas (SRK/T, Hoffer Q, Holladay 1, Haigis, and Holladay 2) for pediatric eyes in children of different ages.

Methods

In this prospective study, patients who received cataract surgery and IOL implantation in the capsular bag were enrolled. We compared the calculation accuracy of 5 formulas at 1 month postoperatively and performed subgroup analysis with the patients divided into three groups according to their ages at the time of surgery as follows: group 1 (age ≤ 2 years, 35 eyes), group 2 (2 years < age < 5 years, 38 eyes), and group 3 (age > 5 years, 29 eyes).

Results

75 patients (102 eyes) were enrolled in this study. The Haigis formula got the smallest PE among all formulas in all three groups. With regard to APE, there were no statistical differences among the formulas except group 2, with the SRK/T formula a little smaller, the Holladay 2 formula a little larger in group 1, and the Haigis formula a little smaller in group 3. In group 2, the Haigis formula had the lowest APE (0.87 ± 0.61 D), while the Holladay 2 formula had the largest (1.71 ± 1.20 D, p < 0.001), followed by the Holladay 1 formula (1.51 ± 1.07 D, p=0.002). On comparing the percentage of APE within 0.5 D and 1.0 D obtained with 5 formulas in each group, there were no statistical differences. The SRK/T formula and the Holladay 1 formula showed the highest percentage (40.00% and 60.00%) in group 1. While the Haigis formula got the highest percentage in less than 0.5 D (34.21%) and less than 1 D (60.53%) in group 2. In group 3, the Holladay 2 formula and the Haigis formula got the highest percentage less than 0.5 D (58.62%) and less than 1 D (79.31%). The multiple linear regression indicated that the age at the time of surgery was a significant factor affecting the accuracy of APE; after removing the age, AL was the only factor that affected the accuracy of APE.

Conclusion

The SRK/T and the Holladay 1 formulas were relatively accurate in patients younger than 2 years old, while the Haigis formula performed better in patients older than 2.

Update on Intraocular Lens Formulas and Calculations

Investigators, scientists, and physicians continue to develop new methods of intraocular lens (IOL) calculation to improve the refractive accuracy after cataract surgery. To gain more accurate prediction of IOL power, vergence lens formulas have incorporated additional biometric variables, such as anterior chamber depth, lens thickness, white-to-white measurement, and even age in some algorithms. Newer formulas diverge from their classic regression and vergence-based predecessors and increasingly utilize techniques such as exact ray-tracing data, more modern regression models, and artificial intelligence. This review provides an update on recent literature comparing the commonly used third- and fourth-generation IOL formulas with newer generation formulas. Refractive outcomes with newer formulas are increasingly more and more accurate, so it is important for ophthalmologists to be aware of the various options for choosing IOL power. Historically, refractive outcomes have been especially unpredictable in patients with unusual biometry, corneal ectasia, a history of refractive surgery, and in pediatric patients. Refractive outcomes in these patient populations are improving. Improved biometry technology is also allowing for improved refractive outcomes and surgery planning convenience with the availability of newer formulas on various biometry platforms. It is crucial for surgeons to understand and utilize the most accurate formulas for their patients to provide the highest quality of care.

Accuracy of 8 intraocular lens power calculation formulas in pediatric cataract patients

PURPOSE

To compare the accuracy of the eight formulas for intraocular lens (IOL) power calculation in pediatric cataract patients.

METHODS

A retrospective study. A total of 68 eyes (68 patients) that underwent uneventful cataract surgery and posterior chamber IOL implantation in the capsular bag were enrolled. We compared the calculation accuracy of the 8 formulas at 1 month postoperatively and performed subgroup analysis according to age or axial length (AL).

RESULTS

The mean age at surgery was 34.07 ± 24.60 months and mean AL was 21.12 ± 1.42 mm. The mean prediction errors (PE) of eight formulas for all patients were as follows: SRK II (- 0.66), SRK/T (- 0.44), Holladay 1 (- 0.36), Hoffer Q (- 0.09), Olsen (0.71), Barrett (0.37), Holladay 2 (- 0.70), and Haigis (0.50). There was significant difference among the 8 formulas (p < 0.0001), while no significant difference of absolute PE was found among the 8 formulas in all patients (p = 0.053). Moreover, in patients younger than 2 years old or with AL ≤ 21 mm, SRK/T formula was relatively accurate in 34% and 39% of eyes, respectively. While in patients older than 2 or with AL > 21 mm, Barrett and Haigis formulas were better (58% and 47% for Barrett, 52% and 53% for Haigis).

CONCLUSION

Overall, in patients younger than 2 years old or with AL ≤ 21 mm, SRK/T formulas were relatively accurate, while Barrett and Haigis formulas were better in patients older than 2 or with AL > 21 mm.

Accuracy of intraocular lens power calculations in paediatric eyes

IMPORTANCE

There is no clear consensus on which intraocular lens (IOL) power calculation formula provides the best refractive prediction in the paediatric population.

BACKGROUND

To evaluate the predictability of desired postoperative refractive outcomes by using six IOL formulas in paediatric cataract cases.

DESIGN

Retrospective case series.

PARTICIPANTS

A total of 377 eyes in 377 paediatric patients (<13 years of age) who received primary IOL implants in the capsular bag.

METHODS

This study utilized formulas, namely, SRK II, SRK/T, Hoffer Q, Holladay 1, T2 and Super formula. Prediction errors were calculated based on the difference between the postoperative refraction and the refraction predicted by each formula.

MAIN OUTCOME MEASURES

The mean prediction error, mean absolute error, median absolute error, percentages of eyes within the prediction errors of ±0.50 D, ±1.00 D and ± 2.00 D.

RESULTS

The mean axial length was 22.48 ± 1.91 mm (<22.0 mm for 161 eyes). The average age at surgery was 55.21 ± 28.01 months (<24 months for 37 eyes). The mean prediction error was positive (hyperopic error) with all formulas. Compared to the other IOL power formulas, SRK II showed significantly higher absolute errors (P < .001). Hoffer Q and Holladay 1 generated the least absolute error, followed closely by Super formula. Multiple logistic analyses indicated that age at time of surgery was an independent factor significantly contributing to the refractive surprise using all formulas.

CONCLUSIONS AND RELEVANCE

SRK II was the least predictable formula in this study. HofferQ and Holladay 1 yielded the best predictive values.

Updates on managements of pediatric cataract

Purpose

A comprehensive review in congenital cataract management can guide general ophthalmologists in managing such a difficult situation which remains a significant cause of preventable childhood blindness. This review will focus on surgical management, postoperative complications, and intraocular lens (IOL)-related controversies.

Methods

Electrical records of PubMed, Medline, Google Scholar, and Web of Science from January 1980 to August 2017 were explored using a combination of keywords: "Congenital", "Pediatric", "Childhood", "Cataract", "Lens opacity", "Management", "Surgery", "Complication", "Visual rehabilitation”, and "Lensectomy". A total number of 109 articles were selected for the review process.

Results

This review article suggests that lens opacity obscuring the red reflex in preverbal children and visual acuity of less than 20/40 is an absolute indication for lens aspiration. For significant lens opacity that leads to a considerable risk of amblyopia, cataract surgery is recommended at 6 weeks of age for unilateral cataract and between 6 and 8 weeks of age for bilateral cases. The recommended approach in operation is lens aspiration via vitrector and posterior capsulotomy and anterior vitrectomy in children younger than six years, and IOL implantation could be considered in patients older than one year. Most articles suggested hydrophobic foldable acrylic posterior chamber intraocular lens (PCIOL) for pediatrics because of lower postoperative inflammation. Regarding the continuous ocular growth and biometric changes in pediatric patients, under correction of IOL power based on the child's age is an acceptable approach. Considering the effects of early and late postoperative complications on the visual outcome, timely detection, and management are of a pivotal importance. In the end, the main parts of post-operation visual rehabilitation are a refractive correction, treatment of concomitant amblyopia, and bifocal correction for children in school age.

Conclusions

The management of congenital cataracts stands to challenge for most surgeons because of visual development and ocular growth. Children undergoing cataract surgery must be followed lifelong for proper management of early and late postoperative complications. IOL implantation for infants less than 1 year is not recommended, and IOL insertion for children older than 2 years with sufficient capsular support is advised.

Validation of Guidelines for Undercorrection of Intraocular Lens Power in Children

PURPOSE

Initial undercorrection of intraocular lens (IOL power) is a common practice in children undergoing pediatric cataract surgery. However, the long-term refractive status of these children is largely unknown. The purpose of this study is to analyze the long-term refractive status of these children.

DESIGN

Retrospective observational study.

METHODS

We analyzed records of children (<7 years of age) who underwent cataract surgery with a primary IOL implantation and had completed follow-up to ≥7 years of age. Data were collected regarding demographics, etiology of cataract, method of undercorrection, and serial follow-up refractions. Prediction error was defined as refractive error minus emmetropia. The main outcome measure was prediction error at 7 years of age.

RESULTS

Eighty-four eyes of 56 children (28 unilateral and 28 bilateral cases) met the study criteria. The median age at surgery was 3.3 years (interquartile range 2.7-5 years), and the median follow-up period was 3.75 years. At 7 years of age, the median absolute prediction was 1.5 diopters (interquartile range 0.75-2 diopters). Seven of 84 (8.3%) children achieved emmetropia while an equal proportion were myopic (45%) or hypermetropic (46%). Prediction error (adjusted for using both eyes) at 7 years of age was not significantly different in any group (P > .05). Maximum myopic shift was observed in children <2 years of age. Age at surgery was the only significant factor that influenced prediction error (â = -0.32; P = .001).

CONCLUSION

This study suggests that children undercorrected using guidelines suggested by Enyedi and associates may achieve an acceptable refractive error at 7 years of age. However, in children <2 years of age, more hypermetropia may be observed. More studies are needed to validate various methods of undercorrection and compare with other guidelines.

Paediatric intraocular lens implants: accuracy of lens power calculations

PurposeThis study aims to evaluate the accuracy of lens prediction formulae on a paediatric population.MethodsA retrospective case-note review was undertaken of patients under 8 years old who underwent cataract surgery with primary lens implantation in a regional referral centre for paediatric ophthalmology, excluding those whose procedure was secondary to trauma. Biometric and refractive data were analysed for 43 eyes, including prediction errors (PE). Statistical measures used included mean absolute error (MAE), median absolute error (MedAE), Student's t-test and Lin's correlation coefficient.ResultsThe mean PE using the SRK-II formula was +0.96 D (range -2.47D to +2.41 D, SD 1.33 D, MAE 1.38 D, MedAE 1.55, n=15). The mean PE was smaller using SRK/T (-0.18 D, range -3.25 D to +3.95 D, SD 1.70 D, MAE 1.30 D, MedAE 1.24, n=27). We performed an analysis of the biometry data using four different formula (Hoffer Q, Holladay 1, SRK-II and SRK/T). Hoffer Q showed a smaller MedAE than other formulae but also a myopic bias.ConclusionOur clinical data suggest SRK/T was more accurate in predicting post-operative refraction in this cohort of paediatric patients undergoing cataract surgery. Hoffer Q may have improved accuracy further.

Predictability of intraocular lens power calculation formulae in infantile eyes with unilateral congenital cataract: results from the Infant Aphakia Treatment Study

PURPOSE

To compare accuracy of intraocular lens (IOL) power calculation formulae in infantile eyes with primary IOL implantation.

DESIGN

Comparative case series.

METHODS

The Hoffer Q, Holladay 1, Holladay 2, Sanders-Retzlaff-Kraff (SRK) II, and Sanders-Retzlaff-Kraff theoretic (SRK/T) formulae were used to calculate predicted postoperative refraction for eyes that received primary IOL implantation in the Infant Aphakia Treatment Study. The protocol targeted postoperative hyperopia of +6.0 or +8.0 diopters (D). Eyes were excluded for invalid biometry, lack of refractive data at the specified postoperative visit, diagnosis of glaucoma or suspected glaucoma, or sulcus IOL placement. Actual refraction 1 month after surgery was converted to spherical equivalent and prediction error (predicted refraction - actual refraction) was calculated. Baseline characteristics were analyzed for effect on prediction error for each formula. The main outcome measure was absolute prediction error.

RESULTS

Forty-three eyes were studied; mean axial length was 18.1 ± 1.1 mm (in 23 eyes, it was <18.0 mm). Average age at surgery was 2.5 ± 1.5 months. Holladay 1 showed the lowest median absolute prediction error (1.2 D); a paired comparison of medians showed clinically similar results using the Holladay 1 and SRK/T formulae (median difference, 0.3 D). Comparison of the mean absolute prediction error showed the lowest values using the SRK/T formula (1.4 ± 1.1 D), followed by the Holladay 1 formula (1.7 ± 1.3 D). Calculations with an optimized constant showed the lowest values and no significant difference between the Holladay 1 and SRK/T formulae (median difference, 0.3 D). Eyes with globe AL of less than 18 mm had the largest mean and median prediction error and absolute prediction error, regardless of the formula used.

CONCLUSIONS

The Holladay 1 and SRK/T formulae gave equally good results and had the best predictive value for infant eyes.

Refractive changes after removal of anterior IOLs in temporary piggyback IOL implantation for congenital cataracts

Purpose

To assess the refractive change and prediction error after temporary intraocular lens (IOL) removal in temporary polypseudophakic eyes using IOL power calculation formulas and Gills' formula.

Methods

Four consecutive patients (7 eyes) who underwent temporary IOL explantation were enrolled. Postoperative refractions calculated using IOL power calculation formulas (SRK-II, SRK-T, Hoffer-Q, Holladay, and the modified Gills' formula for residual myopia and residual hyperopia) were compared to the manifest spherical equivalents checked at 1 month postoperatively.

Results

The mean ages of temporary piggyback IOL implantation and IOL removal were 6.71 ± 3.68 months (range, 3 to 12 months) and 51.14 ± 18.38 months (range, 29 to 74 months), respectively. The average refractive error was -13.11 ± 3.10 diopters (D) just before IOL removal, and improved to -1.99 ± 1.04 D after surgery. SRK-T showed the best prediction error of 1.17 ± 1.00 D. The modified Gills' formula for myopia yielded a relatively good result of 1.47 ± 1.27 D, with only the variable being axial length.

Conclusions

Formulas to predict refractive change after temporary IOL removal in pediatric polypseudophakia were not as accurate as those used for single IOL implantation in adult eyes. Nonetheless, this study will be helpful in predicting postoperative refraction after temporary IOL removal.

[Treatment of pediatric cataracts. Part 2: IOL implantation, postoperative complications, aphakia management and postoperative development]

There is a lot of uncertainty concerning intraocular lens (IOL) implantation for pediatric cataracts. The appropriate age which ocular abnormalities are contraindications and according to which formula IOL should be calculated are controversial. In addition to the imperative of identifying postoperative complications, such as secondary cataract formation and secondary glaucoma in a sufficiently timely manner, a modern management of aphakia with refractive compensation and occlusion is necessary. Some easy rules can help prevent pitfalls.

Accuracy of intraocular lens power calculation formulae in children less than two years

PURPOSE

To assess the accuracy of IOL power calculation formulae in children less than 2 years of age.

DESIGN

Retrospective, comparative study, comprising of 128 eyes of 84 children.

METHODS

We analyzed records of children less than 2 years with congenital cataract who underwent primary IOL implantation. Data were analyzed for prediction error using the 4 commonly used IOL power calculation formulae. We calculated the absolute prediction error with each of the formulae and the formula that gave least variability was determined. The formula that gave the best prediction error was determined.

RESULTS

Mean age at surgery was 11.7 ± 6.2 months. Absolute prediction error was found to be 2.27 ± 1.69 diopters (D) with SRK II, 3.23 ± 2.24 D with SRK T, 3.62 ± 2.42 D with Holladay, and 4.61 ± 3.12 D with Hoffer Q. The number of eyes with absolute prediction error within 0.5 D was 27 (21.1%) with SRK II, 8 (6.3%) with SRK T, 12 (9.4%) with Holladay, and 5 (3.9%) with Hoffer Q. Comparison between different formulae showed that the absolute prediction error with SRK II formula was significantly better than with other formulae (P < .001). Prediction error with SRK II formula was not affected by any factor such as age (P = .31), keratometry (P = .32), and axial length (P = .27) of the patient. Axial length influenced the absolute prediction error with Holladay (P = .05) and Hoffer Q formulae (P = .002). Mean keratometry influenced prediction error (P = .03) with SRK T formula.

CONCLUSION

Although absolute prediction error tends to remain high with all present IOL power calculation formulae, SRK II was the most predictable formula in our series.

Long-term Outcomes of Undercorrection Versus Full Correction After Unilateral Intraocular Lens Implantation in Children

PURPOSE

To evaluate the impact of full correction vs undercorrection on the magnitude of the myopic shift and postoperative visual acuity after unilateral intraocular lens (IOL) implantation in children.

DESIGN

Retrospective case control study.

METHODS

The medical records of 24 children who underwent unilateral cataract surgery and IOL implantation at 2 to <6 years of age were reviewed. The patients were divided into 2 groups based on their 1-month-postoperative refraction: Group 1 (full correction) -1.0 to +1.0 diopter (D) and Group 2 (undercorrection) ≥+2.0 D. The main outcome measures included the change in refractive error per year and visual acuity for the pseudophakic eyes at last follow-up visit. The groups were compared using the independent groups t test and Wilcoxon rank sum test.

RESULTS

The mean age at surgery (Group 1, 4.2±0.9 years, n=12; Group 2, 4.5±1.0 years, n=12; P=.45) and mean follow-up (Group 1, 5.8±3.7 years; Group 2, 6.1±3.5 years; P=.69) were similar for the 2 groups. The change in refractive error (Group 1, -0.4±0.5 D/y; Group 2, -0.3±0.2 D/y; P=.70) and last median logMAR acuity (Group 1, 0.4; Group 2, 0.4; P=.54) were not significantly different between the 2 groups.

CONCLUSIONS

We did not find a significant difference in the myopic shift or the postoperative visual acuity in children aged 2 to <6 years of age following unilateral cataract surgery and IOL implantation if the initial postoperative refractive error was near emmetropia or undercorrected by 2 diopters or more.

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.

Prediction error and accuracy of intraocular lens power calculation in pediatric patient comparing SRK II and Pediatric IOL Calculator

Background

Despite growing number of intraocular lens power calculation formulas, there is no evidence that these formulas have good predictive accuracy in pediatric, whose eyes are still undergoing rapid growth and refractive changes. This study is intended to compare the prediction error and the accuracy of predictability of intraocular lens power calculation in pediatric patients at 3 month post cataract surgery with primary implantation of an intraocular lens using SRK II versus Pediatric IOL Calculator for pediatric intraocular lens calculation. Pediatric IOL Calculator is a modification of SRK II using Holladay algorithm. This program attempts to predict the refraction of a pseudophakic child as he grows, using a Holladay algorithm model. This model is based on refraction measurements of pediatric aphakic eyes. Pediatric IOL Calculator uses computer software for intraocular lens calculation.

Methods

This comparative study consists of 31 eyes (24 patients) that successfully underwent cataract surgery and intraocular lens implantations. All patients were 12 years old and below (range: 4 months to 12 years old). Patients were randomized into 2 groups; SRK II group and Pediatric IOL Calculator group using envelope technique sampling procedure. Intraocular lens power calculations were made using either SRK II or Pediatric IOL Calculator for pediatric intraocular lens calculation based on the printed technique selected for every patient. Thirteen patients were assigned for SRK II group and another 11 patients for Pediatric IOL Calculator group. For SRK II group, the predicted postoperative refraction is based on the patient's axial length and is aimed for emmetropic at the time of surgery. However for Pediatric IOL Calculator group, the predicted postoperative refraction is aimed for emmetropic spherical equivalent at age 2 years old. The postoperative refractive outcome was taken as the spherical equivalent of the refraction at 3 month postoperative follow-up. The data were analysed to compare the mean prediction error and the accuracy of predictability of intraocular lens power calculation between SRK II and Pediatric IOL Calculator.

Results

There were 16 eyes in SRK II group and 15 eyes in Pediatric IOL Calculator group. The mean prediction error in the SRK II group was 1.03 D (SD, 0.69 D) while in Pediatric IOL Calculator group was 1.14 D (SD, 1.19 D). The SRK II group showed lower prediction error of 0.11 D compared to Pediatric IOL Calculator group, but this was not statistically significant (p = 0.74). There were 3 eyes (18.75%) in SRK II group achieved acccurate predictability where the refraction postoperatively was within ± 0.5 D from predicted refraction compared to 7 eyes (46.67%) in the Pediatric IOL Calculator group. However the difference of the accuracy of predictability of postoperative refraction between the two formulas was also not statistically significant (p = 0.097).

Conclusions

The prediction error and the accuracy of predictability of postoperative refraction in pediatric cataract surgery are comparable between SRK II and Pediatric IOL Calculator. The existence of the Pediatric IOL Calculator provides an alternative to the ophthalmologist for intraocular lens calculation in pediatric patients. Relatively small sample size and unequal distribution of patients especially the younger children (less than 3 years) with a short time follow-up (3 months), considering spherical equivalent only.

Comparison of intraocular lens power calculation formulae in pediatric eyes

PURPOSE

To evaluate accuracy of intraocular lens (IOL) power calculation formulae (SRK II, SRK/T, Holladay 1, Hoffer Q) in pediatric eyes.

DESIGN

Retrospective case series.

PARTICIPANTS

One hundred thirty-five eyes of 96 children with congenital, developmental, or acquired cataracts who underwent uncomplicated cataract surgery and IOL implantation by a single surgeon over a 10-year period.

METHODS

Axial length (AL), keratometry (K), and manufacturer's A constant were employed in 4 common IOL power calculation formulae to predict the refractive outcome. Retinoscopy was measured at 4 to 8 weeks postoperatively and converted to spherical equivalent. For analysis, eyes were grouped by age at surgery, AL, and mean K.

MAIN OUTCOME MEASURES

We determined the prediction error (PE) = predicted refraction - actual refraction and the absolute PE = |predicted refraction - actual refraction|. The formula that gave the best prediction (minimum PE) was determined.

RESULTS

The mean age at surgery was 6.4 years. Mean absolute PE was 1.11 for the SRK II, 0.84 for SRK/T, 0.76 for Holladay, and 0.76 for Hoffer Q formulae. There was a trend toward greater PE in eyes of younger children (< or =2 years), shorter AL (AL < or = 22 mm) and steeper corneas (mean K > 43.5 diopters [D]). On comparing absolute PE obtained with 4 formulae in each patient, Hoffer Q gave the minimum PE in 46% of eyes compared with 23% with SRK II, 18.5% with SRK/T, and 12.5% with Holladay 1. The SRK/T, Holladay 1, and Hoffer Q were similar in accurately predicting refractive error within +/-0.5 D in about 43% eyes. When clinically significant deviation in PE occurred (>0.5 D), there was usually an undercorrection (72%), except for Hoffer Q, which was almost as likely to overcorrect as undercorrect (44% vs 56%). The PE was lower with office measurements when compared with anesthesia measurements, owing probably to better fixation in older children with higher ALs.

CONCLUSION

The PE was insignificant (PE < or = 0.5 D) in 43% eyes, and similar for all formulae. However, the Hoffer Q was predictable for the highest number of eyes. When the PE was >0.5 D, most formulae gave an undercorrection, except for the Hoffer Q, which the surgeon may want to consider when targeting postoperative refractions.

Emmetropization and eye growth in young aphakic chickens

PURPOSE

To establish a chick model to investigate the trends of eye growth and emmetropization after early lensectomy for congenital cataract.

METHODS

Four monocular treatments were applied: lens extraction (LX); sham surgery/-30 D lens; LX/+20 D lens; and LX/+30-D lens (nine per group). Lens powers were selected to slightly undercorrect or overcorrect the induced hyperopia in LX eyes and to induce comparable hyperopia in sham-surgery eyes. Refractive errors and axial ocular dimensions were measured over a 28-day period. External ocular dimensions were obtained when the eyes were enucleated on the last day.

RESULTS

The growth patterns of experimental (Exp) eyes varied with the type of manipulation. All eyes experiencing hyperopia initially grew more than their fellow eyes and exhibited myopic shifts in refraction. The sham/-30 D lens group showed the greatest increase in optical axial length, followed by the LX group, and then the LX/+20 D lens group. The Exp eyes of the LX/+30 D lens group, which were initially slightly myopic, grew least, and showed a small hyperopic shift. Lensectomized eyes enlarged more equatorially than axially (i.e., oblate), irrespective of the optical treatment applied.

CONCLUSIONS

The refractive changes observed in young, aphakic eyes are consistent with compensation for the defocus experienced, and thus emmetropization. However, differences in the effects of lensectomy compared to those of sham surgery raise the possibility that the lens is a source of essential growth factors. Alterative optical and mechanical explanations are offered for the oblate shapes of aphakic eyes.

Accuracy of biometry in pediatric cataract extraction with primary intraocular lens implantation

PURPOSE

To determine the accuracy of predicted postoperative refractive outcomes in pediatric patients having cataract surgery with intraocular lens (IOL) implantation and to compare them with other variables historically considered important in cataract surgery.

SETTING

Tertiary care referral hospital.

METHODS

This retrospective review comprised 203 eyes of 153 consecutive pediatric patients (< or = 18 years old) having cataract extraction with primary posterior chamber IOL implantation in the capsular bag. All cases were performed by 1 of 2 surgeons, and all refractions were performed manually by an experienced pediatric ophthalmologist using a retinoscope.

RESULTS

In all patients, the mean absolute value (MAE) of the prediction error was 1.08 diopters (D) +/- 0.93 (SD). Age at time of surgery and corneal (K) mean curvature were significantly correlated with the absolute value of the prediction error (P = .0006 and P = .0088, respectively). A multiple regression model showed that age at time of surgery and K mean curvature were the only 2 variables significantly associated with MAE; axial length, formula, surgeon, and A-scan type were not significantly associated with prediction error.

CONCLUSIONS

Data from 203 consecutive primary pediatric IOL implantations showed the heterogeneous nature of the variables involved in predictions of refractive outcomes in this population. The complexities of this issue support the need for specific methods of measurement and an IOL calculation formula for the pediatric population.

Effect of axial length and keratometry measurement error on intraocular lens implant power prediction formulas in pediatric patients

PURPOSE

To examine the relationship between axial length and keratometry measurement errors and intraocular lens (IOL) power calculations for pediatric eyes.

METHODS

The sensitivity of IOL power calculation to errors in axial length and keratometry measurements was computed as a function of axial length and keratometry for the SRK II, Hoffer Q, Holladay I, SRK/T, and Haigis formulas.

RESULTS

The sensitivity of the IOL power calculation to an axial length measurement error is increased at 4 to 14 D/mm error in axial length in children compared with 3 to 4 D/mm error in axial length in adults. The error in calculation is 0.8 to 1.3 D/D error in keratometry measurement for both children and adults.

CONCLUSIONS

Axial length measurement errors in pediatric eyes may lead to large errors in IOL power calculations.

Intraocular lens power calculation in children

With improving surgical technique and equipment, the acceptable age for placing an intraocular lens in infants and children is becoming younger. The tools for predicting intraocular lens power have not necessarily kept up, as current theoretical and regression intraocular lens power prediction formulas are largely based on adult eyes at axial lengths, anterior chamber depth, and keratometric values much different than those seen in infants. In addition, the adult eye has matured and is no longer growing, whereas the eyes of infants and children may continue to note changes in axial length, keratometric values, and possibly optical characteristics. Another source of error in intraocular lens power selection that is more likely to occur in pediatric patients than in adult patients is inaccuracy in measurement of axial length or keratometric power. A review of current tools and considerations for intraocular lens power prediction in infants and children is presented.