Amblyopia Risk Factors In Children Research Articles

The UCI EyeMobile Preschool Vision Screening Program: Refractive Error and Amblyopia Results from the 2019-2020 School Year.

To introduce the University of California Irvine (UCI) EyeMobile for Children preschool vision screening program and describe the ophthalmic examination results of children who failed screening with the PlusoptiX S12C photoscreener during one school year. Children aged 30-72 months were screened with the PlusoptiX using ROC mode 3 during the 2019-2020 school year. Children who failed screening were referred for comprehensive eye examination on the EyeMobile mobile clinic. Presence of amblyopia risk factors (ARFs), amblyopia, and refractive error was determined via retrospective review of records. Amblyopia was defined as unilateral if there was ≥ 2-line interocular difference in the best-corrected visual acuity (BCVA) and as bilateral if BCVA was < 20/50 for children < 4 years old and < 20/40 for children ≥ 4 years old. ARFs were defined using 2021 American Association for Pediatric Ophthalmology and Strabismus (AAPOS) instrument-based screening guidelines. 5226 children were screened during the study period. Of the 546 children who failed screening, 350 (64%) obtained consent and were examined. Mean age of examined children was 4.45 years. Amblyopia was found in 8% of examined children, with unilateral amblyopia seen in 79% of amblyopic subjects. Glasses were prescribed to 246 (70.3%) children. Of the 240 children who received cycloplegic examinations, 43% had hyperopia and 30% had myopia. The positive predictive value (PPV) of the PlusoptiX screening for ARFs in children who received cycloplegic examinations was 70.4%. A significant proportion of Orange County preschoolers with refractive errors and amblyopia have unmet refractive correction needs. The PlusoptiX S12C photoscreener is an adequate screening device for the UCI EyeMobile for Children program, although modification of device referral criteria may lead to increased PPV. Further research is necessary to understand and overcome the barriers to childhood vision care in our community.

Amblyopia risk factors among pediatric patients in a hospital-based setting using photoscreening.

The aim of our study was to determine the prevalence of amblyopia risk factors in children visiting the American University of Beirut Medical Center (AUBMC) using automated vision screening. This was a hospital-based screening of 1102 children aged between 2 and 6 years. Vision screening was performed using PlusoptiX S12 over 2 years (2018-2020). The need for referral to a pediatric ophthalmologist was based on the amblyopia risk factors set forth by the American Association for Pediatric Ophthalmology and Strabismus. Referred patients underwent a comprehensive eye examination. A total of 1102 children were screened, 63 were referred for amblyopia risk factors (5.7%); 37/63 (59%) underwent comprehensive eye examination and 73% were prescribed glasses. Of the non-referred group of children, 6.35% had astigmatism, 6.25% were hyperopic and 3.27% were myopic. The refractive errors observed among the examined patients were distributed as follows: 41% astigmatism, 51% hyperopia, and 8% myopia; amblyopia was not detected. Refractive amblyopia risk factors were associated with the presence of systemic disorders. Bland-Altman plots showed most of the differences to be within limits of agreement. Using an automated vision screener in a hospital-based cohort of children aged 2 to 6 years, the rate of refractive amblyopia risk factors was 5.7%. Hyperopia was the most commonly encountered refractive error and children with systemic disorders were at higher risk.

Biometric features and amblyopia risk factors in children with congenital nasolacrimal duct obstruction that underwent probing after 1 year-old

Biometric features and amblyopia risk factors in children with congenital nasolacrimal duct obstruction that underwent probing after 1 year-old

Comparison of photoscreening and autorefractive screening for the detection of amblyopia risk factors in children under 3 years of age

To evaluate the effectiveness of photoscreening and autorefractive screening for the detection of amblyopia risk factors (ARFs) in a cohort of preterm and term-born children <3years of age. In this cross-sectional study, the Spot Vision photoscreener and the SureSight autorefractor were used to screen participants. The diagnostic and predictive values of the devices in detecting ARF based on American Association for Pediatric Ophthalmology and Strabismus (AAPOS) 2013 referral criteria was calculated using manufacturer criteria, the VIP 90 (90% specificity) and VIP 94 (94% specificity) criteria from the Vision in Preschool (VIP) study, and criteria recommended by Rowatt and colleagues. Results were evaluated using receiver operating characteristic (ROC) curves. A total of 368 patients (mean age, 14.4±10.4months) were included. The ARF rate was 25% according to the 2013 AAPOS criteria. The highest specificity and positive predictive values (PPV) were obtained with Spot Vision manufacturer criteria (specificity, 0.91; PPV, 0.69). SureSight manufacturer criteria showed very low specificity and PPV values (specificity, 0.43; PPV, 0.35) and a high false positive rate (57%). The highest specificity and PPV values for SureSight were obtained with the Rowatt criteria (specificity, 0.86; PPV, 0.62). In our study cohort, photoscreening with the Spot Vision manufacturer criteria seemed sufficient for vision screening in the 0-3years age group, with high specificity values.The Rowatt criteria may increase performance of the SureSight in this age group.

Application of deep learning and image processing analysis of photographs for amblyopia screening.

Purpose:Photo screeners and autorefractors have been used to screen children for amblyopia risk factors (ARF) but are limited by cost and efficacy. We looked for a deep learning and image processing analysis-based system to screen for ARF.Methods:An android smartphone was used to capture images using a specially coded application that modified the camera setting. An algorithm was developed to process images taken in different light conditions in an automated manner to predict the presence of ARF. Deep learning and image processing models were used to segment images of the face. Light settings and distances were tested to obtain the necessary features. Deep learning was thereafter used to formulate normalized risks using sigmoidal models for each ARF creating a risk dashboard. The model was tested on 54 young adults and results statistically analyzed.Results:A combination of low-light and ambient-light images was needed for screening for exclusive ARF. The algorithm had an F-Score of 73.2% with an accuracy of 79.6%, a sensitivity of 88.2%, and a specificity of 75.6% in detecting the ARF.Conclusion:Deep-learning and image-processing analysis of photographs acquired from a smartphone are useful in screening for ARF in children and young adults for a referral to doctors for further diagnosis and treatment.

Doğumsal Tek Taraflı Gözyaşı Kanal Tıkanıklığı Olan Olgularda Refraktif Durum

Objective: To investigate the refractive status and frequency of amblyopia risk factors in children who underwent probing for unilateral nasolacrimal duct obstruction (NLDO). Material and Methods: This descriptive cross-sectional study included 65 consecutive children with unilateral congenital NLDO who were still symptomatic at one year examination and necessiated nasolacrimal duct probing. A complete ophthalmic evaluation including cycloplegic refraction was performed. The spherical, cylindrical and spherical equivalent retinoscopy measurements of both eyes were noted. The risk factors for amblyopia and differences between refractive values of both eyes were evaluated. Results: The mean age at presentation was 20.4±9.2 months (range, 12 to 48 months). The left eye was involved in 30 (46.2 %) patients. Thirty-five subjects (54 %) were female. Nine children had amblyopia risk factors (13.8%). There was no statistically significant difference regarding cylindrical refractive error, spherical refractive error and spherical equivalent (p=0.9, p=0.9 and p=0.5 respectively) between two eyes. Conclusion: In the current study, no statistically significant difference was found between refractive values of both eyes. One tenth of children in our study group were found to be under risk of amblyopia mostly due to high astigmatism. Further studies about the effect of blurred vision on visual development of both eyes and binocular vision may provide more information about the refractive status in this group of patients.

A device for the assessment of both visual acuity and strabismus to identify amblyopic risk factors in preverbal and verbal children – pilot study

Instrument based vision screening for high refractive error and amblyopia is recommended for infants and children aged 1-3 years by the AAPOS. Eye-N-JOY (ENJ) is a novel device (patent no. US 9,844,317 B2), including a tablet, infrared camera, LCD glasses and cloud-based software. While child is watching images on the tablet screen, camera sensors track the child's eye movements as they respond to optical stimulation. The device provides a “pass” or “refer” result. The study assessed the accuracy of the ENJ device in identifying low vision or the presence of amblyopia risk factors in children

Diagnostic test accuracy of Spot and Plusoptix photoscreeners in detecting amblyogenic risk factors in children: a systemic review and meta-analysis.

Amblyopia is a permanent visual impairment developed in early childhood. Recently, instrument-based photoscreeners have been widely used for vision screening to detect amblyopia risk factors, which is key for the prevention and treatment of amblyopia. This meta-analysis aims to evaluate the diagnostic test accuracy of Spot and Plusoptix photoscreeners in detecting risk factors for amblyopia in children. An electronic literature search was performed in October 2018 using the MEDLINE, Embase, and Web of Science databases. Twenty-one publications with a total of 5022 subjects were included. Subjects given a comprehensive examination were considered to have amblyopia or amblyogenic risk factors based on the American Association for Pediatric Ophthalmology and Strabismus (AAPOS) referral criteria guidelines. The overall sensitivity for Spot and Plusoptix was 87.7% and 89.4%, respectively (p=0.38); the specificity was 78.0% and 89.9%, respectively (p=0.90). For subjects under 7years old (preschool children), the overall sensitivity for Spot and Plusoptix was 91.7% and 90.2%, respectively (p=0.81); the specificity was 82.6% and 93.0%, respectively (p=0.46). Both Spot and Plusoptix photoscreeners demonstrated good sensitivity and specificity in detecting amblyopia risk factors in children, especially at preschool ages. There was no significant difference in diagnostic test accuracy between them.

Unilateral congenital nasolacrimal duct obstruction and amblyopia risk factors.

IntroductionThis study aimed to investigate the prevalence of amblyopia risk factors in patients with unilateral congenital nasolacrimal duct obstruction (CNLDO).Patients and methodsA retrospective interventional case series was performed on all consecutive patients of unilateral CNLDO who underwent probing over a 6-month period in 2017. All patients underwent a complete ocular examination, retinoscopy, axial length measurements and keratometry. Risk factors for amblyopia were noted based on the American Association for Pediatric Ophthalmology and Strabismus guidelines. The fellow eye of the patients with CNLDO was taken as an internal control. Statistical analysis was performed using Stata version 13.0 statistical software. A p-value of ≤0.05 was considered statistically significant.ResultsOne hundred eyes of 50 patients were studied. The median age at presentation was 36 months without any gender predisposition (M: 26, F: 24). All patients presented with symptoms of epiphora. Seven (14%) of the patients were noted to have amblyopia risk factors: five (10%) were secondary to refractive errors and two (4%) had congenital cataracts. The anisometropia noted in the five patients showed the worse eye to be the one with CNLDO in all the cases. The common refractive error noted was a compound hyperopic astigmatism in three eyes followed by mixed astigmatism and simple hyperopia in one eye each.ConclusionThe prevalence of amblyopia risk factors in children with unilateral CNLDO is marginally higher than that reported in general population. Hence, a thorough evaluation should be carried out to detect amblyopia risk factors and for their prompt management.

Performance of Photoscreener in Detection of Refractive Error in All Age Groups and Amblyopia Risk Factors in Children in a Tribal District of Odisha: The Tribal Odisha Eye Disease Study (TOES) # 3.

PurposeTo evaluate effectiveness of Welch Allyn Spot Vision Screener in detecting refractive error in all age groups and amblyopia risk factors in children in a tribal district of India.MethodsAll participants received dry retinoscopy and photorefraction; children also received cycloplegic retinoscopy. Statistical analysis included Bland-Altman and coefficient of determination (R2).ResultsPhotoscreener could not elicit a response in 113 adults and 5 children of 580 recruited participants. In Bland-Altman analysis mean difference of Spot screener spherical equivalent (SSSE) and dry retinoscopy spherical equivalent (DRSE) was 0.32 diopters (D) in adults and 0.18 D in children; this was an overestimation of hyperopia and underestimation of myopia. In Bland-Altman analysis of SSSE and cycloplegic retinoscopy spherical equivalent (CRSE) the mean difference was −0.30 D in children; this was an overestimation of myopia and underestimation of hyperopia. In regression analysis the relationship between SSSE and DRSE was poor in adults (R2 = 0.50) and good in children (R2 = 0.92). Cubic regression model for Spot versus cycloretinoscopy in children was: CRSE = 0.34 + 0.85 SSSE − 0.01 SSSE2 + 0.006 SSSE3. It was 87% accurate. Sensitivity and specificity of Spot in detecting amblyopia risk factors (2013 American Association for Pediatric Ophthalmology and Strabismus [AAPOS] criteria) was 93.3% and 96.9% respectively. Sensitivity of Spot screener in detection of amblyopia was 72%.ConclusionsPhotoscreener has 87% accuracy in refraction in children. Its value could be used for subjective correction tests.Translational RelevancePhotoscreening could complement traditional retinoscopy to address refractive error in children in a resource-limited facility region.

Effectiveness of the GoCheck Kids Vision Screener in Detecting Amblyopia Risk Factors

The GoCheck Kids smartphone photoscreening app (Gobiquity Mobile Health, Scottsdale, Arizona, USA), introduced in 2014, is marketed to pediatricians with little published validation. We wished to evaluate the GoCheck Kids Screener for accuracy in detecting amblyopia risk factors (ARF) using 2013 American Association for Pediatric Ophthalmology and Strabismus guidelines. Validity assessment. Children 6months to 6 years of age presenting from October 2016 to August 2017 were included. Children were screened with the GoCheck preloaded Nokia Lumia 1020, software version 4.6 with image processing version R4d, prior to undergoing a comprehensive eye examination by a pediatric ophthalmologist masked to the screener results. Determination of the presence of age-specific ARF was made based upon the examination and compared with the GoCheck recommendation. A total of 206 children were included (average age 43months). When compared to examination, GoCheck had a sensitivity of 76.0% and specificity of 67.2% in detecting ARF. Positive predictive value was 57.0% and negative predictive value 83.0%. The screener results of 13 children were changed from "no risk factors" to "risk factors identified" based on the GoCheck remote review process. Four images remained "not gradable" and screening was unsuccessful in 3 children. In our high-risk population, this version of the Gocheck Kids smartphone app was useful in identifying ARF in children who are often not able to cooperate with visual acuity testing. This study informs pediatricians about the efficacy of this new screener as they make decisions about how to best detect vision problems in young children.

Refractive Status and Amblyopia Risk Factors in Chinese Children with Autism Spectrum Disorder.

Amblyopia risk factors in children with autism spectrum disorders (ASD) are usually hard to detect in early childhood due to poor cooperation and has not been reported in the Chinese population. We screened 168 Chinese children with ASD, aged between 3 and 8years, and 264 age-matched neurotypical children with Spot photoscreener and basic ophthalmologic examinations. Children with ASD were found to have normal refractive status but significantly higher incidence of strabismus (16.1%), compared with control children (1.5%) (p < 0.01). Most of the cases of strabismus found in children with ASD were classified as esodeviation. Strabismus in children with ASD should be considered more seriously as an amblyopia risk factor by ophthalmologists and other healthcare professionals.

Nasolacrimal duct obstruction: Does it really increase the risk of amblyopia in children?

Purpose:To report the prevalence of amblyopia risk factors in children with congenital nasolacrimal duct obstruction.Methods:A retrospective review of records of children with the diagnosis of congenital nasolacrimal duct obstruction (NLDO), who underwent probing from January 2009 to October 2011, was done. All of them underwent a complete ophthalmic evaluation including cycloplegic refraction and strabismus evaluation before probing.Results:A total of 142 children were included in this study. The mean age at presentation was 22.38 months (sample standard deviation (SSD) – 15.88). Amblyopia risk factors were defined according to two sets of guidelines: The American Association for Pediatric Ophthalmology and Strabismus (AAPOS) referral criteria guidelines and the new AAPOS Vision Screening Committee guidelines. Twenty-eight (20%) children were found to have some form of amblyopia risk factor based on the referral criteria prescribed by AAPOS. However, on applying modified guidelines described by Donahue et al., to analyze the same cohort, 21 children were found to have amblyogenic risk factors. Of these 28 children, 13 had significant astigmatism (>1.50 D), 8 children had hypermetropia (>3.50 D), and six children had anisometropia (>1.50 D). One child had significant cataract (media opacity >1 mm). None of the children in this series had either myopia or strabismus.Conclusion:Prevalence of amblyopia risk factor was found to be 20% in our study based on the older guidelines; however, it reduces to 14.78% by applying the modified guidelines. Despite this reduction, importance of a comprehensive ophthalmic examination including cycloplegic refraction in all children presenting with NLDO cannot be overstated. A close follow-up of these children is also essential to prevent the development of amblyopia.

Performance of the Plusoptix A09 photoscreener in detecting amblyopia risk factors in Chinese children attending an eye clinic.

PurposeTo assess the accuracy of the Plusoptix A09 photoscreener in detecting amblyopia risk factors in children and determine referral criteria when using Plusoptix A09 for a large-scale vision screening.MethodsPediatric patients attending our eye clinic underwent a comprehensive ophthalmic examination that included photorefraction, orthoptic examination, anterior segment assessment, fundus examination and cycloplegic retinoscopy. The measurements were collected for statistical analyses.ResultsOne hundred and seventy-eight children (mean age ± SD: 6.2±2.4 years, range: 2.2 to 14.1 years) were included in the study. The mean spherical equivalent (SE) obtained using Plusoptix A09 (PSE) was 0.57 D lower than that obtained from cycloplegic retinoscopy (CRSE) (P = 0.00). However, there was no statistically significant difference of Jackson cross cylinder J0 and J45 between Plusoptix A09 (PJ) and cycloplegic retinoscopy (CRJ) (P = 0.14, P = 0.26). The relationship of SE obtained from Plusoptix A09 and SE obtained from cycloplegic retinoscopy was presented as the equation: CRSE = 0.358 + 0.776 PSE + 0.064 PSE 2 + 0.011 PSE 3. Based on the Receiver Operating Characteristic (ROC) curve, the Plusoptix A09 had an overall sensitivity of 94.9% and specificity of 67.5% for detecting refractive amblyopia risk factors. The sensitivity and specificity of the Plusoptix A09 for detection of strabismus were 40.7% and 98.3%, respectively; detection of amblyopia and/or strabismus was 84.7% and 63.2%, respectively.ConclusionsThe Plusoptix A09 photoscreener underestimated hyperopia and overestimated myopia according to SE when compared with cycloplegic retinoscopy. The accuracy of the Plusoptix A09 in detecting amblyopia risk factors in children could be improved by the regression equation and optimized criteria for refractive amblyopia risk factors developed in the present study. Moreover, the Plusoptix A09 photoscreener is not suitable for a large-scale strabismus screening when it is applied solely.

The prevalence of amblyogenic factors in children with persistent congenital nasolacrimal duct obstruction.

To evaluate the prevalence of amblyopia risk factors in children that underwent probing for persistent congenital nasolacrimal duct obstruction (CNLDO). The medical records of children with CNLDO (after 1 year of age) that underwent probing were reviewed. Amblyopia risk factors, based on the American Association for Pediatric Ophthalmology and Strabismus referral criteria in 2013, were sought in the patientsʹ records before probing. The proportion of the patients with anisometropia >1.5 diopters (D) was separately calculated. In unilateral cases of CNLDO, sphere, astigmatism, and spherical equivalent of the eyes with CNLDO were compared with contralateral eyes in order to assess the effect of CNLDO on refractive error. In the follow-up examinations, the success of the probing or the need for additional procedures (Crawford intubation, Monoka intubation, or dacryocystorhinostomy) was evaluated. The prevalence of anisometropia between 'successful probing' and 'failed probing' groups was compared. A total of 433 cases were included in the study. 41 cases (9.46 %) had amblyopia risk factors. Twenty-four cases (5.5 %) had anisometropia >1.5 D (spherical or cylindrical). In unilateral cases of CNLDO, the sphere and spherical equivalent of the eyes with CNLDO were significantly greater than those of the contralateral eyes (p < 0.001 for both). Thirty-nine patients (9 %) required other interventions due to failure of probing (failed probing group). There were significantly more anisometropia prevalence in this group, compared with the successful probing group, at the initial examination (p = 0.03). The findings of greater prevalence of anisometropia >1.5 D (compared with the prevalence in the general population) and significantly greater sphere and spherical equivalents in the eye with CNLDO (compared with contralateral eye) in unilateral cases with CNLDO, suggested some relationships between anisometropia and long-term untreated CNLDO. The finding of more anisometropia in failed probing cases may support the theory of structural abnormality as an explanation for the possible relationship between congenital nasolacrimal duct obstruction and anisometropia.

Performance of the Spot vision screener for the detection of amblyopia risk factors in children

To compare the accuracy of the Spot photoscreener (Pediavision Holdings LLC Lake Mary, FL) in detecting amblyopia risk factors in children to the 2003 and 2013 referral criteria of the American Association for Pediatric Ophthalmology and Strabismus (AAPOS). The medical records of children 1-6 years of age who underwent vision screening at a single clinic from February 2012 through May 2012 were retrospectively reviewed. Participants were screened with the Spot photoscreener on the same day as a pediatric ophthalmology examination. Visual acuity examination, ocular alignment testing, and cycloplegic refraction were performed that day or within the preceding 6 months for all included subjects by one pediatric ophthalmologist. Sensitivity and specificity of the Spot photoscreening results were compared to the 2003 and to the recently revised 2013 AAPOS referral criteria. A total of 151 children were included. The Spot had a sensitivity of 80% and specificity of 74%. With the revised 2013 AAPOS referral criteria, the sensitivity was 87% and specificity was 74%. The Spot is a fully portable, automated tool for the detection of amblyopia risk factors in children. In this study cohort it was found to reliably detect amblyopia risk in children when compared to the 2003 and 2013 AAPOS referral criteria.

Incidence of amblyopia risk factors in children with nasolacrimal duct obstruction

Previously published research suggested that children with nasolacrimal duct obstruction and amblyopia risk factors on initial examination often develop clinical amblyopia. The present study reports the incidence of clinical amblyopia in children presenting with nasolacrimal duct obstruction but no amblyopia risk factors.

The plusoptiX S08 photoscreener as a vision screening tool for children with autism

Children with autism and related disorders reportedly have an increased prevalence (40%) of ocular disorders, and comprehensive eye examinations by a pediatric ophthalmologist are recommended. Examinations can be very time consuming, expensive, and stressful for the child. A photoscreener such as the plusoptiX S08 may be a cost-effective, time-saving, and less invasive method for testing patients with autism. The purpose of this study was to determine the efficacy of photoscreening with the plusoptiX S08 in detecting amblyopia risk factors in children with autism. Photoscreening and complete ophthalmologic examinations were performed on 43 children with autism. Prevalence, sensitivity, specificity, positive predictive value, and negative predictive value were calculated using ophthalmologic examination as the gold standard. The gold standard examination used American Association for Pediatric Ophthalmology and Strabismus Vision Screening Committee guidelines for the definition of amblyopia risk factors. The plusoptiX S08 referred 29 (67%) of 43 children. On examination, 16 patients (37%) had amblyopia risk factors. The plusoptiX S08 had a sensitivity of 94% (95% CI, 0.68-0.99). The specificity was 48% (95% CI, 0.29-0.68), the positive predictive value was 52% (95% CI, 0.33-0.70), and the negative predictive value was 93% (95% CI, 0.64-0.99). The plusoptiX S08 is sensitive but less specific at detecting treatable ocular conditions in children with autism. The majority of children with autism and amblyopia risk factors were detected on screening; however, about half of all referrals had no amblyopia risk factors. The plusoptiX S08 reduced the need for a full examination in one-third of the children screened.

Comparison of the iScreen and the MTI photoscreeners for the detection of amblyopia risk factors in children

The iScreen and Medical Technology and Innovations, Inc, (MTI) photoscreeners objectively screen for amblyopia risk factors in children. The MTI photoscreener has been extensively validated as a device that objectively screens for amblyopia risk factors in children, but limited availability of the instant film it uses may soon render it obsolete. More recently the iScreen photoscreener has been introduced. This device captures images digitally and transmits them electronically to be interpreted. We compared the newer iScreen's ability to detect amblyopia risk factors in children with the established MTI photoscreener. The medical records of consecutive subjects screened by both the iScreen and MTI photoscreeners on the same day were retrospectively reviewed. The iScreen images were analyzed by the device's central interpretation center; MTI images were analyzed by an expert masked examiner using the delta crescent method. Referrals by both instruments were compared to the results of cycloplegic examination as per the American Association for Pediatric Ophthalmology and Strabismus 2003 referral criteria. A total of 169 children were included in the study. Of these, 107 (63%) were found to have amblyopia risk factors. The iScreen was found to have an accuracy rate of 81%, sensitivity of 87%, and specificity of 76%. The MTI was found to have an accuracy rate of 81%, sensitivity of 81%, and specificity of 81%. The iScreen and MTI performed similarly in detecting amblyopia risk factors when compared to a comprehensive pediatric ophthalmology examination.

Performance of the plusoptiX A08 photoscreener for the detection of amblyopia risk factors in children 0 to 5 in central Iowa

Performance of the plusoptiX A08 photoscreener for the detection of amblyopia risk factors in children 0 to 5 in central Iowa