A Cost-Benefit Analysis of Vision Screening Methods for Preschoolers and School-Age Children

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1 A Cost-Benefit Analysis of Vision Screening Methods for Preschoolers and School-Age Children Vijay N. Joish, BPharm, MS, Daniel C. Malone, PhD, and Joseph M. Miller, MPH, MD Introduction: The purpose of this study was to determine costs and benefits of visual acuity screening (VAS) or photoscreening (PS) in children. Methods: A societal-perspective, decision-analytic model compared VAS and PS conducted in three age groups: children 6 to 18 months, 3 to 4 years, and 7 to 8 years old. Literature estimates of sensitivity, specificity, and prevalence were used. Cost estimates and referral rates for surgical treatment were derived from a managed care database and the United States Social Security Administration. Results: All the benefit-to-cost ratios exceeded 1.0, meaning that all screening programs studied had benefits that exceeded the cost of screening. The total net benefit was highest for PS in children of 3 to 4 years of age ($19,412) and the least for VAS in children 7 to 8 years of age ($15,179). The benefit-to-cost ratio was highest for the VAS in children 3 to 4 years of age ($162) and least for PS in infants 6 to 18 month old ($140). Sensitivity of the PS instrument and VAS charts were the most influential variables in determining the most cost-beneficial program. Conclusions: Based on the best available data, the net benefit of PS in 3 to 4 year old preschool children is greater than VAS in children 7 to 8 years of age, PS in toddlers, and VAS in children 3 to 4 years of age. (J AAPOS 2003;7: ) E ye disorders are the forth most common disability in the United States and represent the most prevalent reason for handicapping children. 1 Without early intervention and treatment, affected children may suffer permanent vision damage. Important vision disorders in children include cataracts, strabismus, refractive error, astigmatism, and ocular disease. Strabismus, unequal refractive errors, and cataracts may lead to amblyopia. 2 Testing vision function early in life enables treatment when it is most effective. Amblyopia can be treatable if caught early. 3 Treatment options involve wearing glasses, patching the eye, eye drops (atropine), Bangerter occlusion foils, or optical blurring with lenses. Children who receive early treatment often will enjoy a lifetime of good vision. However, if treatment is not started early, vision damage may be permanent and may even lead to blindness. 3,4 Amblyopia and amblyogenic risk factors, afflicting approximately 3 to 5% of all American children, 5 8 are one From the Department of Pharmacy Practice and Sciences, College of Pharmacy, The University of Anzona, Tucson, Arizona Funded by an educational grant from Research to Prevent Blindness, Inc. Submitted March 5, Revisions accepted April 18, Reprint requests: Daniel C. Malone, PhD Department of Pharmacy Practice and Sciences, PO Box , College of Pharmacy, The University of Arizona, Tucson, AZ Copyright 2003 by the American Association for Pediatric Ophthalmology and Strabismus /2003/$ doi: /s (03) of the leading causes of monocular blindness. In appropriate cases, amblyopia is reversible by therapeutic measures. The United States Preventive Services Task Force, the American Academy of Pediatrics, and the American Association for Pediatric Ophthalmology and Strabismus recommend screening all children between 3 and 4 years of age for amblyopia and strabismus. 9 Screening infants to detect amblyopia and amblyogenic risk factors may detect strabismus, refractive errors, and media opacities earlier, thus facilitating diagnosis and treatment of amblyopia. Consensus does not exist regarding the best screening test. 10 Both the United States Preventive Services Task Force 11 and the American Academy of Pediatrics 12 recommend screening all children between 3 and 4 years of age for amblyopia and strabismus. Current approaches include preliterate eye charts, photorefraction, and tests of stereoacuity. The two most common screening procedures are screening with eye charts or using the Medical Technology Inc, (Riviera Beach, FL) photoscreener (MTIPS). At present, screening with eye charts, (henceforth referred to as visual acuity screening or VAS) remains the most widely used method for preschool screening. 10 The VAS method assesses visual acuity at a distance of 3 m using a full-sized Lea Symbols, HOTV Chart in an illuminated cabinet or the illiterate E game. Allen cards are useful for children age 2.5 to 3 years of age, and the HOTV chart and E game are useful for children 3 to 5 years of age. 3 A vision problem is present when the acuity is worse than 20/40 in either eye or when a two-line difference between eyes exist. 13 The MTIPS is a relatively Journal of AAPOS August

2 284 Joish, Malone, and Miller Journal of AAPOS Volume 7Number 4 August 2003 FIG 1. Photoscreening in 6 to 18 month-old children plus revisual acuity screening decision pathway. (A similar model was used for photoscreening in 6 to 18 month-old children plus rephotoscreening) Referred, The referred pathway is repeated. new eccentric photoscreener being marketed as a device for the detection of amblyogenic factors in preverbal children. The stated advantage of photoscreening over conventional screening techniques is the ease with which it could be used in often difficult-to-test individuals and the provision of photographs that serve as quantifiable objective measures. 14 The purpose of this study was (1) to determine the costs and benefits of a vision-screening program for children of different age groups and (2) to recommend the most costbeneficial screening program from a societal perspective. METHODS AND MATERIALS A decision-analytic model was developed based on information from the literature and claims data from a managed care database. The study perspective adopted was that of the society. The societal perspective incorporates both direct medical care costs and indirect costs such as those associated with lost or decreased productivity. This study compared economic outcomes of vision screening between two groups of preschoolers, 6 to 18 months old and 3 to 4 years old, and one group of school-age children 7 to 8 years old. Only the MTIPS and VAS were evaluated as the method of screening. The probability of a positive test result was based on an expected percentage of children from the population being a screened and referred to an ophthalmologist for further confirmation. Referral rates were derived from the literature and were based on criteria specific to each screening procedure. The outcome variable was net benefits. Assumptions for treatment for each age group are provided below. Six to 18 Months Group Six to 18 month-old children were assumed to be screened using the MTIPS. Children with positive test results were either referred to a specialist (ophthalmologist) or scheduled to be rescreened (VAS or photoscreen) when they were 3 to 4 years old. Specialists referrals were reevaluated and classified as true positive or true negative. Children with true-positives test results were treated using either nonsurgical or surgical methods. Infants with negative initial screening tests were assumed to be rescreened once they reached 3 to 4 years of age. Figure 1 illustrates the decision pathway for this group. Three to Four Years Group The analytic model examined both MTIPS and VAS as the primary method to screen 3 to 4 year-old children. Children with confirmed positive test results were assumed to be referred to a specialist or scheduled to be rescreened 1 year later. It was assumed that specialists would confirm the disease status as either true positive or true negative. Children who tested positive were assumed to be given nonsurgical or surgical treatment to correct their vision disorder. The individuals who tested negative were assumed not to be rescreened.

3 Journal of AAPOS Volume 7Number 4 August 2003 Joish, Malone, and Miller 285 Seven to Eight Years Group In this school-age group, subjects who tested positive in the first visual screening examination were assumed to receive direct medical treatment (surgical or nonsurgical) depending on whether or not the condition was treatable. If the condition was not treatable, the individual was assumed to have a permanent disability. Because complete monocular vision loss caused by amblyopia at school age is rare, a probability of.001 was assumed. 15 This probability estimate is our estimate of the rate of monocular vision loss to 20/200 or worse caused by undetected amblyopia arising in childhood, which could have been avoided if treated earlier. Subjects who tested negative did not receive any treatment or further screenings. Determination of Branch Probabilities Failure and pass rates of screening techniques are a function of the validity (or accuracy) of the screening techniques. Two indicators of the accuracy of a screening measure are sensitivity and specificity. Sensitivity is the probability that an individual will screen positive given that they have the disease being tested. Specificity is the probability that an individual will screen negative given that the disease is not present. Two more useful measures of a test s screening accuracy are positive predictive value (PPV) and negative predictive value (NPV). PPV is the likelihood that a person will have the disease given a positive screening test. NPV is the likelihood that a person will not have the disease given a negative test result. Sensitivity and specificity are unaffected by differences in the prevalence of disease between groups. 16 However, this is not the case for PPV and NPV. As the prevalence of a disease decreases, PPV decreases and NPV increases. A review of the literature was undertaken to identify studies that evaluated (1) the validity of either of the two screening techniques and (2) the prevalence of amblyopia. The following electronic abstracts were used to conduct the search: PubMed, MEDLINE, and International Pharmaceutical Abstracts (IPA). Weighted probability values for each screening method were determined by using individual study sample size as weights. Probabilities for PPV (or true positive) and NPV (or true negative) were obtained by using the following formula: p(true Positive) (prevalence) (sensitivity) [(prevalence) (sensitivity)] [(1 prevalence) (1 specificity)] p(true Negative) (1 prevalence) (specificity). [(1 prevalence)(specificity)] [(prevalence)(1 sensitivity)] Total net benefit of a screening program was calculated using the following formula: Total Net Benefits Benefits (measured in dollars) Costs (measured in dollars) Probability ranges for true positives and true negatives were obtained by varying sensitivity and specificity of each screening method within the appropriate study groups, respectively. Because all infants were rescreened later when they were 3 or 4 years old, the negative predictive value of the photoscreener was assumed to be 100%. Referral rates for the 6 to 18 months and 3 years MTIPS groups were obtained from Donahue et al, 20 ; the 3 years VAS group from Newman et al 17 and Wasserman et al 18 and the 7 to 8 years group from Preslan et al. 19 All referral rates were varied from 1 to 100% around their respective base case values in the sensitivity analyses. The probability of surgical treatment was determined from the managed care database, the method for which is described later in greater detail. It was assumed that all amblyopic children (true positives) were treated. Determination of Prevalence Estimates Prevalence estimates of amblyogenic conditions were obtained from the literature. The more accurate a screening technique, the closer the observed prevalence is to the true underlying prevalence of the condition. Because of lack of sufficient data on the true prevalence (ie, confirmed case) of amblyogenic conditions in the specified age groups, the predicted prevalence estimates obtained from the literature were used in the analysis. Determination of Program Costs Because the perspective of the analysis was that of the society, both direct and indirect costs were included. The costs for this analysis came from the literature, healthcare maintenance organizations claims database, and United States Social Security Administration (SSA). Permanent disability arising from amblyopia is usually monocular. An indirect method to compute an economic value of monocular blindness was undertaken. This estimate was varied across a large range (discussed in a later section) and thus confidence should be placed on the order, rather than the magnitude, of results. The cost estimate for MTIPS was obtained from a cost-analysis study conducted by Donahue et al. 20 The authors conducted a statewide preschool vision-screening program using the MTIPS and screened a total of 15,059 children age 6 to 47 months. For the 1997 to 1998 fiscal year, the investigators calculated a total cost of $211,851, which included costs for film, cameras, supplies, salary, and research. The startup cost for a photoscreening program per preschool child was therefore assumed to be $14. Once a program such as this one has been established and one-time fixed expenditures have occurred, the calculated

4 286 Joish, Malone, and Miller Journal of AAPOS Volume 7Number 4 August 2003 marginal cost for each additional child screened was estimated to be $4. This marginal cost was assumed to be the cost of MTIPS screening in the analysis. Startup costs for VAS were assumed to be negligible. Marginal cost per child for VAS was assumed to be $2. Costs for an ophthalmologic visit (referral visit) and related costs for treatment (surgical and nonsurgical) were estimated using a health maintenance organization (HMO) claims database. Claims for patients 10 years of age or younger (n 1811) in 1999 were used to estimate screening costs. The claims of interest were determined using International Classification of Diseases, Ninth Revision (ICD-9) 21 and Current Procedural Terminology (CPT) codes. Claims were first sorted by age and predetermined CPTcodes, and ICD-9 codes were linked to calculate the referral service, surgical, and nonsurgical costs. Because of the small sample size, nonsurgical costs were averaged across all ages. The same set of claims (n 1811) was also used to determine the probability of undergoing surgical treatment. Determination of Benefits Permanent disability was assumed to result from a loss of vision in one eye because of untreated or undetected amblyopia. This study assumed that when childhood amblyopia is undetected or left untreated, permanent loss of vision in one eye (ie, visual acuity of 20/200 or less in the amblyopic eye and 20/20 in the better eye) would occur at age 10 years. Average United States life expectancy at age 10 was determined using data from 1997 United States National Vital Statistics. 22 The estimated cost to society for legal blindness (ie, visual acuity of 20/200 or less in the better eye) was first calculated using the disability payment made by the SSA for a blind person (child or adult) and the average United States life expectancy. Lifetime disability payment was discounted to the present value using the annuity factor and a discount rate of 5%. To determine cost of monocular blindness, the whole person impairment (WPI) index, which has also been used by other researchers to determine the economic cost of impaired vision, 23,24 was used. WPI is a percentage ranging from 0 to 100, where 0% represents no impairment and 95 to 100% represents a state approaching death. Complete vision loss in one eye represents a 25% impairment of the visual system and a value of 24% on the WPI index. 25 Complete vision loss in both eyes represents 100% impairment of the visual system and a value of 85% on the WPI index. Vision loss due to amblyopia may range from decreased vision that can be corrected by wearing glasses to complete vision loss (ie, visual acuity of 20/200 or less in the amblyopic eye). Visual acuity of 20/200 or less in the amblyopic eye corresponds to 20% impairment of the visual system and a value of 19% on the WPI index. Thus, the cost of vision loss caused by amblyopia was determined by the formula below: Cost of Monocular Blindness (M): M Cost of legal blindness The above cost was used as the benefit for early screening. Additionally, cost of partial vision loss was also determined for four other vision impairments discussed later in the Results section. Sensitivity Analyses Sensitivity analyses should not be confused by the sensitivity of a screening test. A sensitivity analysis is an analytical technique used to determine if the use of alternative but plausible estimates, assumptions, or predictions change the results of the analysis. Sensitivity of a screening test, on the other hand, is a validity measure of the screening test and is the probability of testing positive if the disease is truly present. One-way sensitivity analyses were performed to test the assumptions of the decision-analytic model. Influential parameters were determined using tornado diagrams. Referral rates and three sensitivity measures for the screening programs were varied. Variables were changed until the most favorable screening choice equaled that of the other screening program. The value of the parameter at the break-even point was the limit of robustness for that parameter. The ranges used in the sensitivity analysis were the minimum and maximum values observed in the literature. RESULTS Validity measures (sensitivity and specificity) for the 9,20, MTIPS were obtained from 11 published articles. VAS sensitivity and specificity were obtained from 7 published articles. 18, Table 1 summarizes probability values for screening tests, referral rates, and surgical treatment. Probability that a school-age child would have loss of vision in both eyes caused by delay in vision screening was assumed to be.0085 and was varied between.00 and.09. When MTIPS was the screening technique used, predicted prevalence of amblyogenic conditions among the 6 to 18 months and 3 years groups were 25.29% and 18.11%, respectively. 26 Predicted prevalence was determined to be 7.78% for 3 year-old preschoolers when VAS was the method of screening and was calculated (and weighted) from 5 published reports. 9,17,35,39,40 Prevalence of amblyogenic conditions was assumed to be 5% in the school-age children in accordance with the review of the literature. 41 Cost estimates used in this study are shown in Table 2. The SSA monthly payment for a blind person who has not been previously employed was $1, This represents an annual disability payment of $15,600. Using the annuity factor and a 5% discount rate, the lifetime disability payment for legal blindness was $300,129. Costs of complete vision loss from untreated amblyopia was $67,088/

5 Journal of AAPOS Volume 7Number 4 August 2003 Joish, Malone, and Miller 287 TABLE 1. Model probabilities* Probability measure %Six- to 18- month MTIPS (range) %Three-year MTIPS (range) %Three-year VAS (range) %Seven- to 9-year VAS (range) Probability of TP (sensitivity of 74.8 ( ) 74.8 ( ) 68.4 ( ) 68.4 ( ) the screening test) Probability of Trp (PPV value of 61.4 ( ) 51.1 ( ) 44.5 ( ) 33.3 ( ) the screening test) Probability of TrN (NPV of the NA 98.1 ( ) 97.2 ( ) 98.2 ( ) screening test) Referral rate 8.1 ( ) 6.1 ( ) 24.6 ( ) 10.4 ( ) Probability of surgical treatment 14.0 ( ) 14.0 ( ) 14.0 ( ) 14.0 ( ) Probability of condition being treatable NA NA NA 99.9 ( ) *Values (in percentages) given are for the base-case, and those in parentheses are range values used in the sensitivity analyses. Values change as prevalence of the disease or validity of the screening measures change. TP, test positive; TrP, true positive; TrN, true negative; PPV, positive predictive value; NPV, negative predictive value; NA, not applicable (assumed to 1); MTIPS, Medical Technology Inc photoscreening technique; VAS visual acuity screening technique. TABLE 2. Cost estimates Unit cost per patient Six- to 18-months group (range) Three-year group (range) Seven- to 8- years group (range) Initial/follow-up screening Visual acuity screening $2 (1 10) $2 (1 10) $2 (1 10) Photoscreening $4 (1 20) $4 (1 20) $4 (1 20) Startup cost for $14 (0 30) $14 (0 30) $14 (0 30) photoscreening program Ophthalmologic visit $48 (11 90) $43 (9 77) $51 (15 86) Surgical treatment $1992 ( ) $2026 (0 4057) $1842 (0 4458) Nonsurgical treatment $23 (0 85) $23 (0 85) $23 (0 85) TABLE 3. Cost of vision loss to society caused by amblyopia Visual acuity Better eye % Vision Loss Impairment of Amblyopic visual system eye (%) Impairment of WPI (%) Cost of vision loss to society* ($) 20/ $67,088 20/ $38,840 20/ $21,186 20/ $14,124 20/ $0 *Cost of vision loss to society cost of legal blindness WPI $300,129 WPI/0.85. Baseline value used in the decision tree. WPI, whole person impairment. child screened. This cost was then varied at various vision impairment levels (Table 3). The costs and consequences of the five vision screening programs are shown in Table 4. The total net benefit (benefits costs) was highest for the 3 to 4 years group photoscreening program ($19,412) and the lowest for the school-age VAS program ($15,179). The photoscreening program for 6 to 18 month-old infants, followed by rescreening with PS ($17,889) and VAS ($16,960), ranked second and third, respectively. All the benefit-to-cost ratios exceeded 1.0. The benefit-to-cost ratio was highest ($162) for VAS children 3 to 4 years of age and the lowest for PS of 6 to 18 month-old infants ($140). The VAS program for 7 to 8 year-old children ranked second (S153), and the PS program for 3 to 4 year old children ranked third ($146) followed by PS of 6 to 18 month-old infants ($141). Table 5 shows the effect on net benefits when input parameters were varied in a one-way sensitivity analysis. When referral rate for the 6 to 18 months PS group was increased from 8.1% to 16.7%, the 6 to 18 month PS groups with rephotoscreening had net benefits higher than did the 3 to 4 years PS group; when increased beyond 71.3%, repeated VAS had net benefits higher than the 3 to 4 years PS group. When sensitivity, i.e, probability of a child testing positive, of the MTIPS was slightly decreased

6 288 Joish, Malone, and Miller Journal of AAPOS Volume 7Number 4 August 2003 TABLE 4. Net benefits and benefit-to-cost ratios for five vision screening programs for children at baseline estimates Economic outcomes Six to 18 months group photoscreening revision screening Six to 18 months group photoscreening rephotoscreening Three to four years group vision screening Three to four years group photoscreening Seven to 8 years group vision screening Total expected costs ($) Total expected benefits ($) 17,082 18,017 15,534 19,546 15,279 Net expected benefits ($) 16,960 17,889 15,438 19,412 15,179 Benefit-to-cost ratio TABLE 5. Results from one-way sensitivity analyses* Input parameter Six to 18 months group photoscreening revision screening Six to 18 months group photoscreening rephotoscreening Three to four years group vision screening Seven to 8 years group vision screening Referral rates (%) PS 6 to 18 months (8.1) ND ND VAS 3 years (24.6) 65.2 ND ND ND Sensitivity of the screening technique PS 3 years (74.8) ND ND VAS 3 years (68.4) 75.0 ND ND ND VAS 7 to 8 years (68.4) ND ND ND 87.4 PPValue PS 3 years (56.5) 44.7% ND ND ND Cost of monocular blindness ($) (67,088) ND ND 636 ND *The results show threshold points at which the net benefits (benefits costs) equal that of the 3- to 4-years PS group. Values shown in this column (in parentheses) are base values used in the decision-analytic model at which the 3-years group photoscreening program is dominant, ie, has the greatest net benefit and benefit-to-cost ratio. PS, photoscreening; VAS, visual acuity screening; PPV, positive predictive value (function of specificity) ND, not dominant (ie, does not produce equal or higher net benefits than the 3-years group photoscreening program) when input parameter is varied between the predetermined range. from its baseline value of 74.6% to 71.3%, the 6 to 18 months PS group with rephotoscreening had higher net benefits. Similarly, when sensitivity of VAS was increased from 68.4% to 74.9%, the 3 to 4 years VAS group had higher benefits; when increased beyond 87.4% the 7 to 8 years VAS group had higher net benefits. The 6 to 18 months group with revision screening had the greatest net benefits when the PPV of the 3 to 4 years PS group was decreased from its baseline value of 56.5% to 44.7%. Similar one-way sensitivity analyses were performed for benefit-to-cost ratios as the output. None of the benefitto-cost ratios exceeded that of the 3 to 4-years VAS program after varying all parameters, one at a time, within the predetermined range. When the probability of a child suffering from untreatable amblyopia was varied from 0.1 to 0.0%, the final order of the results remained robust. The cost of monocular blindness to society caused by amblyopia was varied across a wide range from baseline value to $0. Across such a wide range, the 3 to 4 years PS group had the greatest benefit until the threshold lifetime cost of $636/child. Below this value, the 3 to 4 years VAS group had the greatest net benefit. DISCUSSION The net benefit to society was greatest when vision screening was performed in preschool-age children compared with school-age children. We found that the benefit-tocost ratios for all screening programs were greater than 1.0, meaning all screening programs were beneficial. The net benefit for the 3 to 4 years PS program was the greatest ($19,412), and screening of the 7 to 8 years VAS group was the lowest ($15,179). The only other known study 43 calculated cost-effectiveness ratio of orthoptic screening for amblyopia in kindergarten-age children (ie, 3 years old). The number of newly diagnosed cases of amblyopia, amblyogenic nonobvious strabismus, and amblyogenic refractive errors was used as the measure of effectiveness. The cost-effectiveness ratio was 727 Euro ($714)/case detected. The investigators considered only costs and effects that occurred up to the clinical end point diagnosis. Vision screening programs such as the ones described in this study incur costs in exchange for a decrease in morbidity complications (eg, loss of vision) and sometimes mortality. Because literature is lacking regarding the economic cost of monocular blindness, an indirect approach was used. Two measures (in which the researchers had the least confidence), the cost of monocular blindness, and probability of a condition being untreatable were varied from baseline to zero. It was assumed that within such a wide range, the actual cost of monocular blindness to society and the probability of a child having an untreatable amblyopia would be captured. The baseline monocular blindness cost of $67,088/child was decreased to $0/child and was evaluated in sensitivity analyses. Even in such a

7 Journal of AAPOS Volume 7Number 4 August 2003 Joish, Malone, and Miller 289 wide range, the 7 to 8 years VAS group never had net benefits greater than did the 3 to 4 years photoscreening group. This study did not consider a number of disadvantages to monocular blindness. Thus, the economic estimate of monocular blindness may not be an overestimate after all. Some of the disadvantages of monocular blindness are as follows: The absence of binocular vision or stereopsis precludes certain occupations such as aviation and police professions. 4 Approximately 0.175% of amblyopes lose their better eye during their working career, thus becoming visually disabled or blind. 44 Tommila et al 7 showed that patients with one amblyopic eye had a higher chance of becoming blind than did the general population. In these patients, vision loss in the good eye usually resulted from accidental trauma, most commonly at work. Furthermore, cataracts being one of the most important causes of severe deprivation amblyopia 3 was not taken into account in the analysis. Another assumption implicit in our study was that of participation and compliance of children in the screening program. For participation, children must be present at the school on the day of the examination, and parents must have consented to the examination. Participation rates and compliance with the provider s care were assumed to be 100% in this study. This study found the greatest benefit in the 3 to 4 years photoscreening group. The 3 to 4 year-old group is generally a verbal group of children who are capable of performing illiterate VAS. However, many of the photoscreening reports from which this study derived the sensitivity and specificity values were performed using preschool children up to 5 years old. 20,26 28 Because vision screening in children up to 5 years old was performed using a photoscreener, this study estimated the costs and benefits of photoscreening in a verbal 3 to 4 years group. Not all diseases are suitable candidates for screening. For a disease to be appropriate for screening, (1) treatment given before symptoms develop should be more beneficial in terms of decreasing reducing morbidity or mortality than that given after they develop, (2) the prevalence of preclinical disease should be high among the population screened, and (3) the expenditure of resources on screening must be justifiable in terms of eliminating or ameliorating adverse health consequences. 45 Former issues regarding the benefits of early screening of amblyopia in children have been adequately addressed in the literature. The purpose of this study was to estimate and to determine if early vision screening in children was cost-beneficial. The assumptions and estimates used in the decision analyses were rigorously tested using one-way sensitivity analyses by varying each influential parameter within its plausible range. Therefore, confidence should be placed on the order, rather than the magnitude of the results obtained in this study. Based on the results of this study, we recommend that early vision screening in preschoolage children is cost-beneficial to the society. This study examines only certain economic benefits of screening children for amblyopia. We did not attempt to value poor versus good eyesight because data were lacking. Improving eyesight is likely to have many positive benefits, including increased educational and job performance, social function, and quality of life. CONCLUSION In conclusion, amblyopia is a common cause of unilateral visual impairment and is the third most frequent cause of unilateral blindness. 46 The greatest net benefit was obtained when the screening strategy was to use photoscreening in 3- to 4-year-old preschoolers. References 1. Ciner EB, Dobson V, Schmidt PP, Allen D, Cyert L, Maguire M, et al. A survey of vision screening policy of preschool children in the United States. Surv Ophthalmol 1999;43: Abrahamsson M, Fabian G, Andersson AK, Sjostrand J. A longitudinal study of a population based sample of astigmatic children. I. Refraction and amblyopia. Acta Ophthalmol (Copenh) 1990;68: Magramm I. Amblyopia: etiology, detection, and treatment. Pediatr Rev 1992;13: Mulvihill A, Bowell R, Lanigan B, O Keefe M. Uniocular childhood blindness: a prospective study. J Pediatr Ophthalmol Strabismus 1997;34: Rahi JS, Sripathi S, Gilbert CE, Foster A. Childhood blindness in India: causes in 1318 blind school students in nine states. 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