Optometry - Journal of the American Optometric Association
Volume 81, Issue 9 , Pages 476-484, September 2010

An analysis of vision screening data from New York City public schools

  • Marie I. Bodack, O.D.

      Affiliations

    • Cincinnati Children's Hospital, Cincinnati, Ohio
    • Corresponding Author InformationCorresponding author: Marie I. Bodack, O.D., Cincinnati Children's Hospital, MLC 4008, 3333 Burnet Avenue, Cincinnati, Ohio 45229-3039.
    • ,
  • Ida Chung, O.D.

      Affiliations

    • State University of New York State College of Optometry, New York, New York
    • ,
  • Ira Krumholtz, O.D.

      Affiliations

    • State University of New York State College of Optometry, New York, New York

published online 09 July 2010.

Article Outline

Abstract 

Objective

This study compares different vision screening batteries and documents the failure rates of different vision tests in children who receive periodic vision screenings.

Methods

Vision screenings were conducted on 1,992 preschool through fifth grade children attending schools in lower socioeconomic areas in New York City. The screening battery incorporated visual acuity, retinoscopy, cover test, stereopsis, near point of convergence, ocular motility, accommodation, color vision, and ocular health.

Results

Slightly less than one third (30%) of the children screened failed the State University of New York (SUNY) battery and were referred for a comprehensive examination, of which 249 (41%) children actually passed distance visual acuities. The referral rate for distance visual acuity alone was 19%. The referral rate for the Modified Clinical Technique (MCT) was 22%. A greater percentage (33%) of the children in grades kindergarten through fifth were referred compared with the preschoolers (20%). Only a small percentage (8%) of the children wore corrective lenses at the time of testing. There was a significant increase in the prevalence of binocular vision problems found in children from grades kindergarten through 5.

Conclusions

Poor visual acuity and binocular vision problems exist in schoolchildren despite ongoing vision screenings. The results provide evidence for the necessity of periodic rescreening starting in kindergarten and the importance of screening for hyperopia and binocular vision problems in addition to distance visual acuities.

Keywords: Vision screening, Myopia, Hyperopia, Binocular problems, Children

 

A wide variety of vision screening programs exist for the detection of vision problems in children, with much emphasis on the detection of myopia, amblyopia, and strabismus.1, 2, 3, 4, 5, 6, 7 Documented referral rates for potential vision problems vary from 5% to 74%.6, 7, 8, 9, 10, 11, 12, 13, 14, 15 These studies differ in the age of the included patient sample, conditions screened, and the type and number of tests. In general, binocular function tests, other than those for the detection of strabismus, are rarely included in screening batteries. In some cases only 1 test, most commonly distance visual acuity, is used for a vision screening. It is expected that as more tests are included in a screening battery, there is a greater likelihood of the child's failing at least 1 test. All of these factors undoubtedly influence the referral rates and the vision problems documented.

Over the years, various screening batteries have been developed in an attempt to maximize correct referrals, minimize overreferrals, and identify children with a variety of visual problems. Two such batteries are the Modified Clinical Technique (MCT) and the New York State Optometric Association (NYSOA) Battery.

In the 1950s, the Orinda study developed the MCT screening battery to minimize screening over-referrals while still detecting children with significant eye problems. The MCT screening battery includes distance visual acuity, cover test, retinoscopy, and inspection of ocular health. It was found to be efficient and economical; however, its main disadvantage was that it required doctor assistance.6

In the 1980s, NYSOA developed a more extensive vision screening battery to help identify vision problems that relate to learning.7 The NYSOA battery was fairly extensive and included the following tests: distance and near visual acuities, plus lens hyperopia test, accommodative facility, near point of convergence, Keystone Telebinocular tests for fusion and color vision, stereopsis, King-Devick Test for saccades, and Winterhaven copy forms (for visual motor integration). It was found to identify 66% of children who had a vision problem, while missing 18%. The advantage of this battery was that it could be administered by lay screeners, and the disadvantage was that it was time consuming.

Referral rates for vision problems relate not only to the battery of tests used but also to the population screened. Studies have found that children residing in lower socioeconomic areas are more susceptible to poverty, malnourishment, and negative eye and visual health consequences than their peers in higher socioeconomic areas.16, 17, 18, 19 Only a small body of literature documents the referral rates of vision problems in lower socioeconomic groups. Six screening programs involving children in low-income areas indicate referral rates between 5% and 46%.8, 13, 15, 19, 20, 21 One study compared the failure rates for a vision screening performed on children from a higher socioeconomic area with children residing in a lower economic area and found a greater percentage of the latter failed, 38% versus 24%.8 Even more recently, Marshall et al.15 found that referral rates differ by socioeconomic status, with a mean referral rate of 9% in families with a median income of $60,000 to $79,999 and a mean referral rate of 15% in families with a median income less than $40,000. Another publication on the prevalence of eye and vision conditions in children provides some evidence that underprivileged children have more underdiagnosed and untreated conditions than children living in higher income families.19 A more recent study conducted in an underprivileged immigrant population found higher rates of astigmatism and myopia.22 Similarly, 1 study on children younger than 6 years of age found that amblyopia was more commonly found in Hispanic/Latino children than in black children.23

The purpose of this study is to document the failure rates on vision screening tests, including visual acuity, refractive error, and binocularity in preschool through fifth grade children attending schools located in lower socioeconomic areas of New York City. We report the failure rate by test, the trend of referrals for refractive versus binocular disorders by grade, the rate of eyeglass wear, and a comparison of results from the MCT and the State University of New York (SUNY) batteries. In addition, we discuss the relevance of select screening tests.

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Methods 

Subjects 

A total of 1,992 children were screened during the 1999 to 2002 academic years. The children screened attended preschool, predominantly Head Start programs, or grade school, kindergarten through grade 5. Head Start is a federally funded program that provides developmental and educational services for children from low-income families from birth to age 5.24 Many of the screenings were conducted in economically disadvantaged areas of New York City, with student bodies consisting largely of Hispanic and black children. Based on statistics from the 2002 to 2003 academic year, 82.3% to 99.6% of the students attending the schools screened were eligible for free or reduced price lunch based on family income.25 The ethnic composition of those schools for that time period was as follows: Asian, 0.9% to 2.2%; white, 0.2% to 3.5%; Hispanic, 20.7% to 62.5%; black, 31.8% to 77.9%.

Screening battery 

SUNY State College of Optometry developed a screening course as both a public service and an educational program. Since the school's inception, SUNY has received requests to perform vision screenings at New York City schools to assist with the city mandate for vision screenings. As such, the college developed a distinct vision screening course mandatory for all second-year students enrolled in the professional degree program. From an educational perspective, the course was designed to allow second-year interns to perform vision screenings, using techniques that they had learned during their first-year clinical training. Before being allowed to attend a screening, all students were required to attend a 3-hour orientation and pass a practical examination, demonstrating proficiency in the screening tests.

New York City public schools require vision screenings to be performed on all children. As part of enrollment in New York City Public Schools, parents give consent for vision and hearing screenings to be done. Each district in New York City requires vision screenings on all children, and consent forms are not required. The mandated New York City screening requirement consists of distance and near visual acuities, +2.00 hyperopia test, color vision testing, and stereopsis testing. Generally, the Department of Health would screen children in grades 1, 3, and 5 and all new entries to the school system, and the schools would be responsible for the other grades. Often, schools would request that SUNY help with the screenings.

In the early years of the screening program, SUNY doctors used the NYSOA battery, described previously. However, as the number of schools in which screenings were conducted increased, it was not practical to transport a Keystone telebinocular to different schools on a weekly basis. As a result, cover testing and other forms of color vision testing replaced the Keystone tests. (The screening battery has been referenced in prior publications.9, 11) The battery incorporates elements of both the MCT and the NYSOA batteries and consists of the following tests: brief history, distance and near visual acuities, +2.00 test for hyperopia, retinoscopy, cover test, stereopsis, color vision, near point of convergence, extraocular motilities, amplitude of accommodation, and direct ophthalmoscopy.

Although all screenings were scheduled for 3 hours, not all schools were efficient with organization. For example, in some cases, the room was scheduled for a class' use before the screening was finished, forcing the screening to be completed in less time than originally scheduled. As a result, in some instances, not all tests could be conducted on all children because of time constraints. Often, screenings were conducted only once at a school, which meant that if a child did not finish the screening, that child would not be able to be rescreened. In these cases when time was short, the attending doctor would make decisions for referrals based on the results of tests such as distance vision. In other words, if a child failed distance visual acuity testing, and retinoscopy showed myopia, the child would be referred regardless of the performance on the other tests. The mandatory tests for the students to complete were distance and near acuities, cover test, extraocular motilities, near point of convergence, color vision, and stereopsis. Of the remaining tests, the hyperopia test was performed on all kindergarten through fifth grade children, and retinoscopy was performed on all preschool children. Retinoscopy could be performed on older children if time permitted. History, ophthalmoscopy, and amplitude of accommodation were optional tests for all children. All tests were performed with glasses on if the child had glasses. The average time for a student to complete the screening was between 10 and 15 minutes.

Children were tested for distance visual acuity with the Snellen or Lea Symbol chart, depending on age and ability to respond. Near visual acuity was measured with the HOTV chart or the Allen Picture chart at 16”. Acuities were recorded in Snellen values. The +2.00 D hyperopia test was performed monocularly with the child viewing 2 lines above the line of best distance acuity. The child was asked if the letters could be read. If the child responded positively, the child was then asked to read the letters. An inability to clear the letters constituted a failure. For cover testing, an accommodative target was used for both distance and near fixation. At near, the child was to look at a 20/30 letter (if visual acuity was 20/20), or a letter one line above the best near acuity in that eye. Retinoscopy was performed in free space using skiascopic lenses with the child's fixation maintained at a distance target. The stereopsis test used in the screening was the Randot Stereopsis test (available from Bernell/ U.S.O. Care Equipment, Mishawak, Indiana), which requires the child to wear polarized glasses. Color vision was tested with either Ishihara or Color Vision Testing Made Easy color plates by Waggoner. If a child had previous color vision results on file, color vision was not retested.

The SUNY battery (see Table 1) incorporates elements of both the MCT and the NYSOA batteries, with many of the failure criteria taken directly from these batteries with 2 exceptions. One exception is that the failure criteria for the distance and near cover tests were changed to “any observable esophoria” from the failure criteria specified by the MCT (i.e., 5 and 6 prism diopters distance and near, respectively). The reason for this change is that the normal expected vergence posture is slightly exophoric.26 The other change was that the failure criterion for visual acuity for preschool children was modified to 20/50 or worse based on the Maternal and Child Health Bureau of the NEI Task Force on Vision Screening in Preschool Children.1 For color vision, failure is defined as defects consistent with the answer key provided by the test manufacturer. For motility testing, noncomitant eye movements or motility restrictions are considered abnormal.

Table 1. SUNY vision screening recording form
Blur distance or near, prior specs, burn, itch, tear, red, diplopia, HA, injury, LEE over 1 year ago or none
HistoryPassRefer
Distance VA with/without specs
OD20/30 20/25 20/2020/40 or worse∗
OS20/30 20/25 20/2020/40 or worse∗
Hyperopia (+2.00)Does not clearClears
Near VA with/without specs
OD20/30 20/25 20/2020/40 or worse∗
OS20/30 20/25 20/2020/40 or worse∗
Retinoscopy
Myopia<-0.50 D
Hyperopia<+1.50 D
Astigmatism<-1.00 D
Anisometropia<1.00 D
Cover test
TropiaNoneAny
HyperphoriaNoneAny
Esophoria distanceNoneAny
Esophoria nearNoneAny
Exophoria distance≤5^>5^
Exophoria near≤10^>10^
Color vision (Ishihara) OUNo defectDefect
Direct ophthalmoscopyNormalAbnormal
Stereo (shapes)MatchesUnable to match
Stereo (Wirt circles)#7 or better†#6 or worse
NPC≤ 4 inches> 4 inches
EOMsNormalAbnormal
Accommodative Amplitude
OD>15-(1/4 age)<15-(1/4 age)
OS> 15-(1/4 age)<15-(1/4 age)

D = diopters; O.D. = right eye; O.S. = left eye.

∗For preschoolers failure is 20/50 or worse.

†Passing for Stereopsis Wirt Circles is 40” or better.

The schools were given a copy of the screening results and parent letters. The parent letters also listed the results and stated whether a comprehensive examination was needed. The decision to refer for follow-up was based on failure of 1 or more screening tests on the screening battery and was up to the discretion of the attending optometrist. For example, discretion could be used for referral of only a failure on stereo vision, color vision, or motilities. Some of the children who failed the screening received follow-up care at the University Eye Center (UEC), the patient care facility of SUNY, or at one of SUNY's affiliated clinics. Either the nurse or clerical staff member was responsible for tracking follow-up care adherence. In schools with an eye clinic, the staff optometrist provided and monitored follow-up care.

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Results 

A total of 1,992 children were screened. Of the total screened, 601 (30%) were referred for a comprehensive eye examination. Seven children failed only color vision testing and were not counted as failures for the purpose of this study. Because not every child received every test in the battery, a breakdown of failures by specific test item is compared with the number of children who received the test (see Table 2). Of the 438 preschool children screened, 87 (20%) were referred. Of the 1,554 school-age children (kindergarten through grade 5) screened, 514 (33%) were referred. Of the 601 children referred in this study, 249 children (41%) actually passed distance visual acuity tests and were referred for other reasons.

Table 2. Percentage of children who failed each test item
TestNo. screenedNo. failedFailed (%)
Distance visual acuity (DVA)1,97438219
Near visual acuity (NVA)1,9441608
Hyperopia test1,5391097
Color vision1,79541∗2
Retinoscopy87724728
Myopia 31
Hyperopia 30
Astigmatism 14
Compound hyperopic astigmatism (CHA) 12
Compound myopic astigmatism (CMA) 8
Anisometropia 5
Cover test1,9241508
Strabismus 483
Phoria 1025
Stereopsis – Wirt circles1,75244525
Stereopsis – Randot shapes1,811975
Near point of convergence (NPC)1,8101156
Extraocular muscles1,428282
Amplitude of accommodation583478
Ocular health71041

∗Includes 7 children who only failed color vision testing. These children were not counted as fails for the purpose of data analysis.

One hundred sixty-three (8%) of all children screened were wearing spectacles at the time of the screening. If a child was wearing glasses at the time of the screening, all tests, including retinoscopy, were done over the glasses. With the glasses, 80 of the 163 children (49%) failed the screening: 65 children (81%) failed a test of visual acuity, 3 children (16%) failed for binocularity (and passed visual acuity), and 2 children (2.5%) failed for reported symptoms. Of the non–eyeglass-wearing children, 521 of 1,829 (28%) failed the screening. When comparing children who were wearing glasses with those who did not wear glasses, children who wore glasses were more likely to be referred than children who did not wear glasses. This difference was statistically significant (X2 = 1.33, P>0.01).

Forty-six children (2%) self-reported or teacher reported that they had glasses but were not wearing them at the time of the screening. They were labeled as noncompliant. Twenty-eight (61%) of the noncompliant children failed the screening. The percentage of children wearing, or who had a history of wearing, glasses, based on their teacher reports, ranged up to approximately 2% for preschoolers and increased to 9% for kindergarteners. This percentage remained stable at 9% for first and second graders, increased to 15% for third graders, and reached a high of 20% for fifth graders.

There were 97 preschool children in Head Start who had completed the entire battery: cover test, Randot and Wirt Stereopsis, near point of convergence, distance and near visual acuity, retinoscopy, and color vision testing. Of the 97 children, 24 (25%) were referred. The majority of children were referred for failure on Wirt circles and retinoscopy (see Table 3).

Table 3. Reasons for referral by grade for Head Start
Grade/ageNo. referred/total screened% ReferredNo. Dist VANo. Near VANo. CTNo. RandotNo. WirtNo. NPCNo. Ret
HS34/15271026803
HS414/5824841319216
HS56/24252011807
Total24/972511441035226

Note. Some children failed multiple tests.

HS = Head Start; CT = Cover test; NPC = Near point of convergence; Dist = distance.

In grades K through 5, 1,108 children had completed the entire battery: cover test, Randot and Wirt stereopsis, near point of convergence, distance and near visual acuity, hyperopia test, and color vision testing. Of the 1,108 children, 299 (27%) failed a test(s) in the battery and were referred (see Table 4) Failure rates for both distance visual acuity and Wirt stereopsis when compared with those of other tests were significant to the 0.01 level when compared to other tests. More than 40% of patients failed 2 or more binocular tests. The binocular failures were significant compared with those of the near test or hyperopia test.

Table 4. Reasons for referral by grade for grades K-5
GradeNo. referred/total screened% ReferredNo. Dist VANo. Near VANo. CTNo. RandotNo. WirtNo. NPCNo. Hyperopia
K20/952198462356
18/571442421333
287/299295521258832017
336/1262928413420121
486/3052857183314622722
562/22627461516104088
Total299/110827199 (18%)68 (6%)95 (9%)44 (4%)241
(21%)		75 (7%)57 (5%)

Note. Some children failed multiple tests; CT = Cover test; NPC = Near point of convergence; Dist = distance.

Chi-squared analysis showed that there was no significant difference between referral rates in the early grades (K to 1) and the upper grades (2 through 5). However, there was a significant increase in referral rates between the kindergarten and first graders and the second through fifth graders. (X2 = 1.45, P>0.01)

Because the Snellen or a picture chart acuity measurement is sometimes the only test performed at a vision screening, the percentage of children who would have failed the screening battery based only on Snellen acuity was found to be 16% (196 of 1,205) of the children who received all tests in the battery (see Table 5).

Table 5. DVA failures versus other refractive failures versus binocular-only failures by grade
GradeTotal referralsDVA failuresRefractive failuresBinocular failures
HS341 (25%)2 (50%)1 (25%)
HS4147 (50%)7 (50%)0
HS562 (33%)4 (67%)0
K209 (45%)6 (30%)5 (25%)
184 (50%)1 (13%)3 (37%)
28753 (61%)18 (21%)16 (18%)
33626 (72%)3 (8%)7 (19%)
48651 (59%)13 (15%)22 (26%)
56243 (69%)5 (8%)14 (23%)
Total323196 (61%)59 (18%)68 (21%)

HS = Head Start.

Of the 299 school-age children (grades K through 5) who had all tests completed and were referred, 137 children (46%) actually passed distance visual acuities and were referred for other reasons. Specifically, children who passed distance visual acuity but failed near visual acuity, plus lens hyperopia test, or retinoscopy were called failures for “refractive” tests. Forty-six children, or 15% of all referrals, fell into this category (see Table 5).

Similarly, failures by grade on tests of visual efficiency were analyzed. Excluded from this analysis were all nonstrabismics who failed a refractive test, as the binocular problem may be secondary to the refractive error. Referral rates for binocular reasons were 0% to 20% in the preschoolers, which was based on a small sample size. Overall binocular failure rate for preschoolers was 0.4%. For the elementary grades, the failure rate for binocular tests ranged from 18% to 37%. Overall, the failure rate for the older grades was 20%. Comparing the preschoolers with the children in kindergarten to grade 5, there was a significant difference in referral for failure on binocular tests (X2 = 2.34, P>0.02), indicating that children in older grades were more likely to be referred for binocular problems. However, there was not a clear, statistically significant difference among the individual grade levels of children referred for failing binocular tests (see Table 5).

Using only the MCT battery of tests, 22% (443 of 1,992) of all children screened would have failed the screening and been referred for further care. Because the MCT battery screens primarily for amblyopia and strabismus, conditions associated with visual efficiency may be missed. To further evaluate the ability of the MCT to detect children with potential visual efficiency (functional vision) problems, data were analyzed to determine what percentage of children with potential functional vision problems, as assessed by amplitude of accommodation, Wirt circles stereopsis, Randot Shapes stereopsis (RDS), extraocular motilities, near point of convergence, or near visual acuity, would not have been referred based on the MCT criterion alone. Slightly more than 8% (37 of 425) of the children who passed all MCT tests were referred for further care based on failure on any of the preceding tests. In other words, the MCT did not detect approximately 8.7% of children who may have a potential visual efficiency problem. There was a range from 3% (2 of 72) for Randot Shapes to a high of 19% (6 to 31) for amplitude of accommodation (see Table 6).

Table 6. Comparison of children who passed the MCT but referred for failure of a functional test (child may have failed more than 1 of these areas)
TestNo. failedNo. children referredNo. referred by MCTPercentage missed
Amplitude of accommodation47312519.4
Wirt circles4452051945.4
Randot shapes9772702.8
Extraocular motilities28191615.8
Near point of convergence115857511.8
Near visual acuity1601401335.0
Total8925525137.1

When comparing the ability of the MCT battery to identify potential visual efficiency problems with that of the SUNY battery, there was no significant difference in referral outcomes (X2 = 0.166, P = 0.1), despite the fact that the SUNY battery included tests for near visual acuity, near point of convergence, stereopsis, amplitude of accommodation, and motilities, tests not included in the MCT.

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Discussion 

The patient population in this study was made up of primarily Hispanic and black students in lower socioeconomic urban areas. The average referral rate of 31% (20% for preschool children and 34% for elementary school children) is consistent with referral rates from other studies also conducted in lower socioeconomic areas.8, 9, 10, 13, 20, 21, 22, 23, 27 One might expect a lower failure rate because many of these children were screened annually and should have been treated for visual acuity problems at the very least. However, prior reports on vision screenings show although children are identified by screenings to require further examination for potential vision problems, as low as 8% actually receive an eye examination.11 Minority children seem to be more at risk for not receiving follow-up care. A study conducted by pediatricians at the University of Michigan found that “non-Hispanic and nonblack children were 47% more likely than Hispanic children and 59% more likely than black children to have received eye care in the last year.”19 The author of the study suggested that cultural and social barriers, parent and teacher perceptions, and insurance issues contribute to the above disparity.

Acuity tests 

Distance visual acuity is still one of the most widely used vision screening tests, despite results from the MCT and NYSOA batteries that document that less than half of the children with clinically significant visual disorders were identified by distance visual acuity alone.6, 7 This study found that approximately 40% of school-age children who had all screening tests and who were referred for further care passed the distance visual acuity test. This was the case when looking at all children who were screened (41%) and looking only at the children who had all tests completed (46%). Had the screening consisted of distance visual acuity testing alone, only 19% of the children screened would have been referred for further care, as opposed to the 30% referred by the SUNY battery. Screening only for reduced distance visual acuities may miss those children with hyperopia, binocular disorders, or ocular health problems.

Given the discrepancy in failure rates based on age, perhaps distance visual acuity testing alone is not an adequate screening test for younger children. Objective measurements of refractive error may be more appropriate for younger children. One study found that 70% of preschool children who failed a screening using the MCT battery failed visual acuity, even though many of them did not have substantiated refractive errors, strabismus, or other signs of poor vision.14 Another study found that 95% of children who failed retinoscopy, compared with only 52% of children who failed distance visual acuity, were confirmed to have a visual problem on a comprehensive examination. These results suggest that an objective test (retinoscopy) is more sensitive than a subjective test (visual acuity).12 One possible reason for these disparities is that retinoscopy detects not only myopia but also clinically significant hyperopia and astigmatism, even in the presence of passing visual acuity. Furthermore, children may malinger because they do or do not want glasses, thereby invalidating the distance visual acuity results.

A child's ability to respond to acuity testing may also influence test results. The use of age-appropriate optotypes is important in the preschool age group. The Maternal and Child Health Bureau of the NEI Task Force on Vision Screening in Preschool Children recommend using the HOTV, Lea, or Tumbling E Test for a preschool child.1 The Tumbling E Test, which incorporates directionality, is often difficult for preschool children. One study reported that 46% of 3- to 4-year-olds were untestable with the Tumbling E test.28 The HOTV or the Lea Symbols are the charts of choice for testing visual acuity in preschoolers. The Lea Symbols consist of 4 optotypes: an apple, house, circle, and square. A matching card is available and can be used to allow children to respond by pointing. All 4 shapes blur equally when visual threshold is reached, an advantage over other picture charts.29 Several studies have found the Lea symbol chart results are similar to those of the HOTV chart, whereas others have found the crowded HOTV yields better results than the Lea symbols in terms of testability and repeatability in preschoolers.28, 29, 30, 31, 32 It is important to mention that in these SUNY screenings, Log-MAR charts were not used. The authors found, in prior screenings, that children have many difficulties with Log-Mar charts. Of the portable options available, the authors' personal preference is the Lea symbol spiral-bound book chart with matching symbols, which allows for flexibility in testing location because it does not have to be mounted on a wall and with 1 to 4 presentations on each card, allows easy isolation of symbols with an “L”-shaped occluder card.

Almost 50% of children tested with their corrective lenses failed the screening battery; the majority of failures (86%) were for distance visual acuity. The finding that children who were wearing glasses were more likely to be referred than children who did not wear glasses was statistically significant. Some of these failures could be because some refractive errors, specifically myopia, are progressive, and a new prescription was needed. The trend is for myopia to peak in the 12 to 17 age group.22 In other cases, a child may have failed for anisometropic amblyopia, for which no spectacle change may be warranted, but patching therapy may have been indicated. These percentages are troubling and merit further investigation to determine if the children who failed had been seen by an eye care provider in the prior year, or if it had been longer, indicating a possible compliance issue.

Two percent of children in this study who reported a history of eyeglass use were noncompliant with their glasses. Approximately 61% of those children failed the screening. It is possible that low myopes chose not to wear their prescribed glasses because of satisfaction with current vision. In other cases, peer pressure, self-perception, and nonacceptance of spectacle wear by parents, may have contributed to a child ’s spectacle wear noncompliance.33, 34, 35 The combination of the failure rate and history of noncompliance, support the need for rescreening children who have received previous eye care.

Visual efficiency tests 

Inefficiencies in the visual system are known to affect academic achievement.36, 37, 38, 39, 40 The prevalence of visual efficiency problems is 15% to 20%.41 Besides visual acuity and refractive error, accommodative and vergence processes contribute to visual efficiency. Accommodative and binocular dysfunctions can have a negative impact on learning, particularly as visual demand increases in higher grades when print is smaller and reading requirements are greater.42, 43 A recent study found that 72% of symptomatic primary school children had nonstrabismic accommodative and/or vergence dysfunctions.44 Prior studies found the incidence of functional visual problems related to accommodation and convergence increased with grade.10, 11 One such study found a 2:1 ratio of functional failures compared with acuity failures for children who passed a screening battery and then failed the same battery 2 years later.11 In the data analysis, children who failed both tests of visual acuity and binocularity were categorized as acuity failures only, which may have underestimated the true percentage of children with potential binocular problems.

In our study, 8.7% of the children referred by the SUNY battery would have passed the MCT battery. Thus, the MCT alone would have identified 91.3% of the children who were referred by the SUNY battery. Does this mean that perhaps the other tests in the SUNY battery, such as near visual acuities, accommodation, stereopsis, and color vision, are extraneous? It is possible that they are; however, further studies in this area are needed. Whether the 8.7% represents true underreferrals, or perhaps are overreferrals, cannot be determined, because comprehensive examination results to which the screening test results can be compared are not available.

Although the MCT includes cover test for evaluation of binocularity, this test may not be adequate to detect strabismus in preschoolers. The Vision in Preschoolers (VIP) Study found that only 73% of preschool children with a constant strabismus and 45% of preschool children with an intermittent strabismus were detected with a cover test performed by licensed eye care providers.45 Many would agree that it is difficult to perform accurate cover testing on some 3- to 5-year-olds. Thus Randot stereopsis could be used as an adjunctive test in the preschool population. Because Randot stereopsis is a test for bifoveation, constant strabismics and intermittent strabismics, who are not aligned during testing, would be expected to fail. Children with high refractive anisometropic amblyopia without strabismus could also fail. The Randot test also may have a high overreferral rate, as preschool children may have difficulties with test interpretation, i.e., a dot image may be more complex for a 3-year-old to interpret, or the child may not attend to the stimulus for a long enough time to appreciate the stereopsis.46

It is important to remember that vision screenings are not comprehensive examinations, and the optometrist has a choice to include certain tests depending on the specific conditions to be identified.

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Conclusions 

This study found that most children referred based on a vision screening failed for retinoscopy, stereopsis, and distance visual acuity. Regardless of grade, the largest percentage of failures was for refractive error, with results fairly equally divided between hyperopia and myopia. Screening only for distance visual acuities may miss approximately 40% of children with potential vision problems, including uncorrected hyperopia and binocular dysfunctions. This finding may be more significant in older children, as binocular vision problems have been found to be more prevalent in higher elementary grades than in preschoolers.

To adequately determine the true prevalence of binocular vision problems, tests for visual efficiency should be included as part of a comprehensive eye and vision examination. The findings from this study point to the need for the identification and treatment of those visual dysfunctions that have the potential to impact learning. In the absence of regular eye examinations, our recommendation is for school-age children to be rescreened at specific time intervals utilizing tests to detect decreased acuities, significant refractive errors, and problems with visual efficiency. Strabismus and amblyopia should be screened for at earlier ages, but because myopia is progressive and because potential binocular problems were more common in older grades, routine screenings during school years may identify children in whom these problems develop later. It is important that vision screening batteries reflect that as children age, their visual demands and refractive statuses change; therefore, these batteries should incorporate age-appropriate tests to evaluate visual acuity and visual efficiency.

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References 

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PII: S1529-1839(10)00276-9

doi:10.1016/j.optm.2010.05.006

Optometry - Journal of the American Optometric Association
Volume 81, Issue 9 , Pages 476-484, September 2010

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