A review of non-strabismic accommodative-vergence anomalies in school-age children. Part 1: Vergence anomalies

Comfortable reading and the performance of near point activities involve efficient accommodative and vergence systems. However, accommodative and vergence anomalies are associated with various symptoms that impair efficient near point tasks. Although several studies investigated accommodative-vergence anomalies in school-age populations, their findings were diverse owing to differences in diagnostic techniques and the criteria used to define the variables. The aim of this paper is to derive prevalence and distribution estimates of vergence anomalies in school-age children and address variations in the study methods and findings. Despite variations in the study methods and findings, accommodativevergence anomalies were common in school-age populations. Variations and limitations of previous studies are discussed and recommendations for improving future studies are suggested.

Related papers:

title: Referral recommendations for binocular function and/or developmental perceptual deficiencies.
abstract: The complexity of the area of binocular function and perceptual development has resulted in the necessity of intraprofessional referrals. We have divided this specialty into systems. These include the accommodative, vergence, ocular motor, sensory and perceptual systems. In each system we have provided symptoms and clinical findings, which can be utilized for tentative diagnostic purposes. It is incumbent on those practitioners whose interests do not lie in this area to be sufficiently knowledgeable relative to both the patient's difficulty, and to the referral source who might best serve the patient's needs.

title: Specific reading disability (dyslexia): what have we learned in the past four decades?
abstract: We summarize some of the most important findings from research evaluating the hypothesized causes of specific reading disability ('dyslexia') over the past four decades. After outlining components of reading ability, we discuss manifest causes of reading difficulties, in terms of deficiencies in component reading skills that might lead to such difficulties. The evidence suggests that inadequate facility in word identification due, in most cases, to more basic deficits in alphabetic coding is the basic cause of difficulties in learning to read. We next discuss hypothesized deficiencies in reading-related cognitive abilities as underlying causes of deficiencies in component reading skills. The evidence in these areas suggests that, in most cases, phonological skills deficiencies associated with phonological coding deficits are the probable causes of the disorder rather than visual, semantic, or syntactic deficits, although reading difficulties in some children may be associated with general language deficits. Hypothesized deficits in general learning abilities (e.g., attention, association learning, cross-modal transfer etc.) and low-level sensory deficits have weak validity as causal factors in specific reading disability. These inferences are, by and large, supported by research evaluating the biological foundations of dyslexia. Finally, evidence is presented in support of the idea that many poor readers are impaired because of inadequate instruction or other experiential factors. This does not mean that biological factors are not relevant, because the brain and environment interact to produce the neural networks that support reading acquisition. We conclude with a discussion of the clinical implications of the research findings, focusing on the need for enhanced instruction.

title: Visual and sensory-motor functioning in the classroom: a preliminary report of ergonomic demands.
abstract: : Observations were made in 11 4th and 5th grade classrooms of the specific ergonomic conditions including physical space, lighting conditions, and academic task demands placed on the students. The data indicate remarkable homogeneity, including the findings that light levels were consistently lowest in the front of the classroom, and that more than 50 percent of the students' time involved near task demands. Observations of behavioral compliance with the task demands will be discussed. We conclude that classroom ergonomic conditions require extensive near work and students with ocular motor dysfunctions may have difficulty meeting the behavioral expectations of the classroom. Implications for future research will be discussed.

title: Validity of the VERA visual skills screening.
abstract: Most school vision screenings test only visual acuity. There is a need for a valid, easily administered test that screens for a wider variety of learning-related vision problems. Visual Efficiency RAting (VERA) is a software program designed for schools to detect both routine vision problems and visual skill problems. The purpose of this study was to compare the VERA visual skills screening with the optometric assessment of binocular, accommodative, and ocular motor skills.



One hundred fifty-four children from grades 3 through 5 were evaluated using the VERA visual skills screening, a clinical battery of visual skills testing, the Convergence Insufficiency Symptom Survey, and 2 reading tests.



The sensitivity of VERA in detecting visual skills problems was 45%, and the specificity was 83%. Sensitivity increased to 64% and specificity to 100% in smaller groups of children when overlays of symptoms, classroom behaviors, and reading skills were included.



VERA has fairly good sensitivity and very good specificity in detecting visual skills problems. Given that the majority of visual skill deficits currently go undetected, VERA can be considered a reasonably effective method of in-school visual skills screening.

title: The Relationship between Convergence Insufficiency and ADHD
abstract: Children being evaluated for attention deficit hyperactivity disorder (ADHD) often have an eye exam as part of their evaluation. The symptoms of convergence insufficiency (CI) can make it difficult for a student to concentrate on extended reading and overlap with those of ADHD.  A retrospective review of 266 patients with CI presenting to an academic pediatric ophthalmology practice was performed. All patients included were diagnosed with CI by one author (DBG) and evaluated for the diagnosis of ADHD. A computerized review was also performed looking at the converse incidence of CI in patients carrying the diagnosis of ADHD.  We reviewed 266 charts of patients with CI. Twenty-six patients (9.8%) were diagnosed with ADHD at some time in their clinical course. Of the patients with ADHD and CI, 20 (76.9%) were on medication for ADHD at the time of diagnosis for CI while 6 (23.1%) were either not on medication or the medication was discontinued several months before the diagnosis of CI. The review of computer records showed a 15.9% incidence of CI in the ADHD population.  We report an apparent three-fold greater incidence of ADHD among patients with CI when compared with the incidence of ADHD in the general US population (1.8–3.3%) (12). We also note a seeming three-fold greater incidence of CI in the ADHD population. This may simply represent an association and not be a causative relationship. Until further studies are performed, however, patients diagnosed with ADHD should be evaluated to identify the small subset that may have CI – a condition that responds well to treatment at home.

title: Measuring ADHD behaviors in children with symptomatic accommodative dysfunction or convergence insufficiency: a preliminary study.
abstract: Accommodative dysfunction and convergence insufficiency (CI) are common pediatric vision problems that have been associated with an increase in frequency and severity of vision-specific symptoms that affect children when doing schoolwork. However, the relationship between accommodative dysfunction and CI and other learning problems, such as attention deficit hyperactivity disorder (ADHD), are not well understood. The purpose of this study was to evaluate the frequency of ADHD behaviors in school-aged children with symptomatic accommodative dysfunction or CI.



Children 8 to 15 years of age with symptomatic accommodative dysfunction or CI were recruited from the teaching clinic at the Southern California College of Optometry. Children with learning disabilities or ADHD were excluded. One parent of each child completed the Conners Parent Rating Scale-Revised Short Form (CPRS-R:S). The children's scores on the CPRS-R:S were compared with the normative sample.



Twenty-four children (9 boys and 15 girls) participated in the study with a mean age of 10.93 years (SD = 1.75). On the CPRS-R:S, cognitive problem/inattention, hyperactivity, and ADHD index were significantly different from normative values (p < or = .001 for all tests).



The results from this preliminary study suggest that school-aged children with symptomatic accommodative dysfunction or CI have a higher frequency of behaviors related to school performance and attention as measured by the CPRS-R:S.

title: Clinical management of binocular vision : heterophoric, accommodative, and eye movement disorders
abstract: Part I: DIAGNOSIS AND GENERAL TREATMENT APPROACH Ch.  Diagnostic Testing Ch. 2: Case Analysis and Classification Ch. 3: General Treatment Modalities, Guidelines, and Prognosis Ch. 4: Primary Care of Binocular Vision, Accommodative and Eye Movement Disorders Part II: VISION THERAPY PROCEDURES AND INSTRUMENTATION Ch.  Introduction and General Concepts Ch. 6: Fusional Vergence, Voluntary Convergence, and Antisuppression Procedures Ch. 7: Accommodative Techniques Ch. 8: Ocular Motility Procedures Part III: MANAGEMENT Ch. 9: Low AC/A Conditions: Convergence Insufficiency and Divergence Insufficiency Ch.  High AC/A Conditions: Convergence Excess and Divergence Excess Ch.  Fusional Vergence Dysfunction, Basic Esophoria, and Basic Exophoria Ch.  Accommodative Dysfunction Ch.  Eye Movement Disorders Ch.  Cyclovertical Heterophoria Ch. 15: Fixation Disparity Part IV: ADVANCED DIAGNOSTIC AND MANAGEMENT ISSUES Ch.  Interactions Between Accommodation and Vergence Ch.  Refractive Amblyopia Ch. 18: Nystagmus Ch. 19: Aniseikonia Ch. 20: Binocular and Accommodative Problems Associated with Computer Use Ch.  Binocular and Accommodative Problems Associated with Acquired Brain Injury Ch.  Binocular and Accommodative Problems Associated with Learning Problems Ch.  Development and Management of Refractive Error: A Binocular Vision-Based Model Ch.  Binocular Vision Problems Associated with Refractive Surgery Part V: VISION THERAPY AND OPTOMETRIC PRACTICE Ch. 25: Patient and Practice Management Issues in Vision Therapy APPENDICES Index

title: Visual function and ocular features in children and adolescents with attention deficit hyperactivity disorder, with and without treatment with stimulants
abstract: investigate visual function and ocular features in children with attention deficit hyperactivity disorder (AD/HD) and establish whether treatment with stimulants is reflected in functioning of the visual system.MethodsDetailed ophthalmologic evaluations without and with stimulants were performed in 42 children (37 boys) with AD/HD, mean age 12 years, and compared with a reference group (ref; n=50; mean age 11.9 years; 44 boys). For a comparison between two groups, Mann–Whitney's U-test was used for ordered and continuous variables; for dichotomous variables, Fisher's exact test was used. For paired comparison (with and without treatment), sign test was used.ResultsIn all, 83% had visual acuity of >0.8 (<0.1 logMAR) without treatment, 90% with stimulants (ref 98%; P=0.032 and n.s., respectively). Heterophoria was found in 29% without, and in 27% with, stimulants (ref 10%; P=0.038 and n.s., respectively) and subnormal stereovision (>60 s of arc) in 26% (ref 6%; P=0.016) without stimulants, and in 27%, with (P=0.014). Abnormal convergence (>6 cm or absent) was noted in 24% (ref 6%; P=0.031) without treatment and in 17%, with (n.s.). Astigmatism (≥1.0 D) was observed in 24% (ref 6%; P=0.03), and signs of visuoperceptual problems in 21% (ref 2%; P=0.007). We found smaller optic discs (n=8/38) and neuroretinal rim areas (n=7/38) (P<0.0001) and decreased tortuosity of retinal arteries (n=6/34) (P=0.0002) than that of controls.ConclusionsChildren with AD/HD had a high frequency of ophthalmologic findings, which were not significantly improved with stimulants. They presented subtle morphological changes of the optic nerve and retinal vasculature, indicating an early disturbance of the development of these structures.

title: VISUAL DISORDERS MISDIAGNOSED AS ADHD CASE STUDIES AND LITERATURE REVIEW
abstract: Attention Deficit/Hyperactivity Disorder (ADHD) is one of the most studied, and most controversial, of the mental health disorders seen in children. Three cases are presented which were, in hindsight, clearly misdiagnosed as ADHD when in fact the individuals had easily treatable visual dysfunctions. ADHD is often misdiagnosed and misunderstood by parents, teachers, eye care professionals, family practitioners, and pediatricians. In fact, some mental health professionals still disagree about the diagnostic criteria for this disorder, especially in young adults. However, almost all agree it is a legitimate disorder that, when diagnosed and managed with a rigorous approach, can be effectively treated. A complete visual evaluation by an eye care professional trained in the thorough testing and diagnosis of eye movements, accommodation, and binocular fusion is one critical step toward avoiding misdiagnosis.

title: Binocular anomalies and reading problems.
abstract: This paper reviews and evaluates the research literature on the relationship of binocular anomalies to reading problems. The weight of the evidence supports a positive relationship between certain binocular anomalies and reading problems. The evidence is positive for exophoria at near, fusional vergence reserves, aniseikonia, anisometropia, convergence insufficiency, and fixation disparity. There is some weak positive evidence for esophoria at near and mixed evidence for stereopsis. The evidence on lateral phorias at distance is negative.

title: Binocular function in school children with reading difficulties
abstract: IntroductionPrior findings suggest that poor readers tend to have poor binocular vision skills, but data on the binocular abilities of children with poor reading skills are lacking. Our aim was to characterize distance and near horizontal heterophoria, distance and near horizontal fusional vergence ranges, accommodative convergence/accommodation (AC/A) ratio, near point of convergence, and stereopsis in poor-reading school-age children without dyslexia selected from a non-clinical population.MethodsWe conducted a cross-sectional study on 87 poor readers and 32 control children (all 8-13 years of age) in grades three to six recruited from eleven elementary schools in Madrid, Spain. With best spectacle correction in each subject, distance and near horizontal heterophoria measurements were obtained using the von Graefe technique, distance and near horizontal fusional vergence ranges were obtained using Risley rotary prisms, the AC/A ratio was measured using the gradient method, near point of convergence (NPC) was evaluated by the standard push-up technique using a transilluminator, and stereoacuity was tested with the Randot stereotest.ResultsMean distance base-in break and base-in recovery values were nearly 2 Δ lower (p < 0.01) in the poor readers than those recorded in the control group. However, mean distance base-out vergences (blur, break and recovery), mean distance and near horizontal heterophoria, mean near horizontal fusional vergence ranges, mean AC/A ratio, mean near point of convergence (NPC), and mean stereoacuity did not differ significantly between the poor readers and controls.ConclusionsThis study provides information on the binocular ability of children with poor reading skills but without dyslexia. Our findings suggest reduced distance base-in break and base-in recovery, such that distance fusional vergence ranges should always be assessed in children who complain of reading difficulties.

title: Designing clinical research
abstract: BASIC INGREDIENTS Getting Started: The Anatomy and Physiology of Clinical Research Stephen B. Hulley, Thomas B. Newman, and Steven R. Cummings Conceiving the Research Question Steven R. Cummings, Warren S. Browner, and Stephen B. Hulley Choosing the Study Subjects: Specification, Sampling, and Recruitment Stephen B. Hulley, Thomas B. Newman, and Steven R. Cummings Planning the Measurements: Precision and Accuracy Stephen B. Hulley and Steven R. Cummings Getting Ready to Estimate Sample Size: Hypotheses and Underlying Principles Warren S. Browner, Thomas B. Newman, and Stephen B. Hulley Estimating Sample Size and Power: Applications and Examples Warren S. Browner, Thomas B. Newman, and Stephen B. Hulley STUDY DESIGNS Designing an Observational Study: Cohort Studies Steven R. Cummings, Thomas B. Newman, and Stephen B. Hulley Designing an Observational Study: Cross-sectional and Case-control Studies Thomas B. Newman, Warren S. Browner, Steven R. Cummings, and Stephen B. Hulley Enhancing Causal Inference in Observational Studies Thomas B. Newman, Warren S. Browner, and Stephen B. Hulley Designing a Randomized Blinded Trial Steven R. Cummings, Deborah Grady, and Stephen B. Hulley Alternative Trial Designs and Implementation Issues Deborah Grady, Steven R. Cummings, and Stephen B. Hulley Designing Studies of Medical Tests Thomas B. Newman, Warren S. Browner, and Steven R. Cummings Research Using Existing Databases: Secondary Data Analysis, Ancillary Studies, and Systematic Reviews Deborah Grady and Norman Hearst IMPLEMENTATION Addressing Ethical Issues Bernard Lo Designing Questionnaires and Interviews Steven R. Cummings and Stephen B. Hulley Data Management Michael A. Kohn Implementing the Study: Pretesting, Quality Control, and Protocol Revisions Stephen B. Hulley and Steven R. Cummings Community and International Studies Norman Hearst and Thomas Novotny Writing and Funding a Research Proposal Steven R. Cummings and Stephen B. Hulley Chapter Exercises

title: Prevalence of vision and ocular disease conditions in a clinical pediatric population.
abstract: The purpose of this study was to fill a significant void in the ophthalmic literature by performing a large scale, comprehensive, prospective study of the prevalence of vision disorders and ocular pathology in a clinical pediatric population using well-defined diagnostic criteria.



A prospective study was performed on 2,023 consecutive patients between the ages of 6 months and 18 years presenting for an initial comprehensive examination at the Eye Institute of The Pennsylvania College of Optometry. There were 373 subjects between 6 months and 5 years, 11 months of age, and 1,650 subjects between 6 years and 18 years of age.



The most important finding from this study is that other than refractive anomalies, the most common conditions optometrists are likely to encounter in a pediatric population are binocular vision and accommodative disorders. The prevalence of accommodative and binocular (strabismic and non-strabismic) vision disorders is 9.7 times greater than the prevalence of ocular disease in children 6 months to 5 years of age, and 8.5 times greater than the prevalence of ocular disease in children 6 to 18 years of age.



The data from this study has great significance for clinicians, optometric educational institutions, health care planners, and administrators. This data suggests that other than refractive anomalies, the most prevalent conditions in the clinical pediatric population are binocular and accommodative disorders. Clinicians should use a minimum data base that includes assessments of accommodation and binocular vision that will allow them to detect conditions with the highest prevalence.

title: Convergence insufficiency-a major review.
abstract: Convergence insufficiency is a common binocular vision disorder affecting approximately 5% of the population in the United States. It is often associated with a host of symptoms that occur when doing near work, such as reading and computer viewing. This article reviews the existing literature on convergence insufficiency including etiology, diagnosis, sensorimotor findings, and management.

title: Clinical Procedures in Optometry
abstract: This comprehensive, heavily illustrated practical text uses a primary care focus to delineate both general patient assessment and specialty aspects of care for the practicing optometrist. Step-by-step guidelines are presented in a consistent outline format for each procedure included, along with many useful charts and tables

title: Frequency of Convergence Insufficiency in Optometry Clinic Settings
abstract: To estimate the frequency of convergence insufficiency (CI) and its related characteristics among 8- to 12-year-old children randomly selected from 2 optometry clinic populations.  Clinic records of 620 children were randomly selected and reviewed according to a standard protocol, using a systematic sampling method based on the total number of 8- to 12-year-old children seen over a 1-year period at 2 optometry clinics. Records were reviewed for demographic and clinical data. Data on CI-related symptoms were obtained at one of the sites. Records that met the eligibility criteria of: good visual acuity (20/30 or better in both eyes); minimal refractive error (–0.50 to +1.00 D and ≤1.00 D of astigmatism in either eye, and ≤1.00 D of anisometropia); and no strabismus were evaluated for Cl-related characteristics. Eligible children were classified according to the direction of their near heterophoria and the number of the following clinical signs present: (1) exophoria at near ≥4δ than at far; (2) insufficient fusional convergence [i.e., failing Sheard's criterion or minimum normative positive fusional vergence (PFV) of 12 A base-out (BO) blur/15 A BO break]; and (3) receded nearpoint of convergence (NPC) of ≥7.5 cm break or ≥10.5 cm recovery. Children were then classified as: no Cl (nonexophoric at near or <4 δ difference between far and near); low suspect (exophoric at near and 1 sign); high suspect (exophoric at near and 2 signs); or definite Cl (exophoric at near and 3 signs).  Sixty-seven percent (415/620) of the records met the eligibility criteria and had complete data on phoria, NPC, and PFV. The age (mean ±SD) of the study population was 10.2 ±1.2 years. Ethnicity data were available for 85% of those eligible; the ethnic distribution was 36% African American, 29% Caucasian, 19% Hispanic, and 1% Asian. About one-half of the 415 children were classified as either low suspect (33%); high suspect (12%); or definite Cl (6%). Clinically significant Cl (high suspect and definite categories) was identified in 17.6% of the children. The percentage of children rated as symptomatic increased with the number of Cl-related clinical signs present.  These findings suggest a high frequency of Cl in optometry clinic populations and a potential correlation between patient symptoms and the number of Cl signs present.

title: Validity and Reliability of the Revised Convergence Insufficiency Symptom Survey in Children Aged 9 to 18 Years
abstract: To assess the validity and reliability of the Convergence Insufficiency Symptom Survey (CISS) in children aged 9 to 18 years. The CISS is the primary outcome measure for a pilot study evaluating two different treatments for convergence insufficiency (CI).  Children with CI were given the CISS twice to assess reliability. CISS scores for the first administration were also compared with scores from children with normal binocular vision to assess the validity of the CISS.  Forty-seven children with CI and 56 children with normal binocular vision participated in the study. Reliability was assessed using intraclass correlation and 95% limits of agreement for the children with CI. For children with CI, the intraclass correlation was 0.77 (95% confidence interval, 0.613 to 0.873), and the 95% limits of agreement were −10.2 to +12.1. The mean (±SD) CISS score was 30.8 ± 8.4 for the children with CI and 8.4 ± 6.4 for the children with normal binocular vision. These means were significantly different (p < 0.0001). Good discrimination (sensitivity, 96%; specificity, 88%) was obtained using a score of ≥16.  Children with CI showed a significantly higher CISS symptom score than children with normal binocular vision. The results of the study indicate that the CISS is a valid and reliable instrument to use as an outcome measure for children aged 9 to 18 who are enrolled in clinical research concerning CI.

title: Association of symptoms and convergence and accommodative insufficiency in school-age children.
abstract: The purpose of this article was to investigate the association between convergence insufficiency (CI) and accommodative insufficiency (AI) and symptoms in a group of school-aged children.



Children ages 8 to 15 years were recruited from two public and 2 private elementary schools in Southern California. The CI Symptom Survey (CISS) was administered to all children before a Modified Clinical Technique vision screening. Children with normal visual acuity, minimal uncorrected refractive error, and no strabismus were tested for CI and Al.



Four hundred sixty nine children were initially screened and 392 participated in testing for CI and AI. Fifty-five percent of the children (218) were classified as having normal binocular vision (NBV), 4.6% (18) had three signs of CI, 12.7% (50) had two signs of CI, 10.5% (41) were classified as AI (with no signs of CI), and 16.6% (65) were classified as other. The symptom score was 3.78 for the NBV group, 4.6 for the two-sign CI group, 6.67 for the three-sign CI group, and 6.37 for the Al group. The three-sign CI and the Al groups scored significantly higher than the NBV group on the CISS (p < or = 0.001).



CI and AI are common conditions in school-age children and are associated with increased symptoms.

title: Accommodative Insufficiency Is the Primary Source of Symptoms in Children Diagnosed With Convergence Insufficiency
abstract: Accommodative insufficiency (AI) and convergence insufficiency (CI) have been associated with similar symptomology and frequently present at the same time. The severity of symptomology in CI has been linked to the severity of the CI, suggesting a dose-dependent relationship. However, with increasing severity of CI also comes increased comorbidity of AI. AI alone has been shown to cause significant symptomology. We hypothesize that AI drives the symptoms in CI with a comorbid AI condition (CIwAI) and that it is the increased coincidence of AI, rather than increased severity of CI, which causes additional symptomology.  Elementary school children (n = 299) participated in a vision screening that included tests for CI and AI and the CISS-V15 symptom survey. They were categorized into four groups:1) normal binocular vision (NBV); 2) AI-only; 3) CI-only; and 4) CIwAI. One hundred seventy elementary school children fell into the categories of interest.  Pairwise comparison of the group means on the symptom survey showed: 1) children with AI-only (mean = 19.7, p = 0.006) and children with CIwAI (mean = 22.8, p = 0.001) had significantly higher symptom scores than children with NBV (mean = 10.3); and 2) children with CI-only (mean = 12.9, p = 0.54) had a similar symptom score to children with NBV. Using a two-factor analysis of variance (AI and CI), the AI effect was significant (AI mean = 21.56; no AI mean = 11.56, p < 0.001), whereas neither the CI effect (p = 0.16) nor the CI by AI interaction effect (p = 0.66) were significant.  CI is a separate and unique clinical condition and can occur without a comorbid AI condition, our CI-only group. Past reports of high symptom scores for children with CI are the result of the presence of AI, a common comorbid condition. When AI is factored out, and children with CI only are evaluated, they are not significantly more symptomatic than children with NBV.

title: Characteristics of convergence insufficiency.
abstract: Convergence insufficiency (CI) is a well-known syndrome of binocular visual dysfunction. In a review of 58 papers, considerable variation was noted in the criteria used to define the condition. Symptoms and decreased positive fusional vergences (both at the nearpoint) were the only criteria named in more than one-half of the studies. An extended nearpoint of convergence (NPC) and increased exophoria at near were criteria in about one-third of the papers. Examination of data in the reviewed papers shows that although considerable variability was noted, the distance exodeviation, distance negative vergences, visual acuity, refraction, and stereopsis were about the same as population norms. Positive vergences, negative vergence at near, and NPC were somewhat less than population norms. Vergences relative to Sheard's criterion, the near exophoria, accommodative amplitude, and the AC/A ratio were consistently below those derived from population norms. This considerable variation may largely be a result of different criteria used for diagnosis, subpopulations within the data, and other confounding factors.

title: Development of Phoria in Children
abstract: Although the prevalence of phoria in adults is well documented, data are scarce on phoria in children. We present results using modified clinical technique vision screening and data from the Orinda Longitudinal Study of Myopia on a large, population-based sample of nonstrabismic children to document the prevalence of phoria with age.  We collected cross-sectional (N=1495) and longitudinal (N=469) data. Phoria data were collected by cover tests administered by one observer who subjectively classified phoria as orthophoria, esophoria, or exophoria in 2 δ steps.  Ninety-seven percent of the children were orthophoric at distance, and there were no significant changes with age. Near phoria showed a more normal distribution, with a 10.8% decrease in the prevalence of exophoria (from 31.8 to 21.0%) and a 5.5% increase in the prevalence of esophoria (from 6.7 to 12.2%) between kindergarten and fifth grade.  Children are typically orthophoric or exophoric at near, but convergent shifts occur with age.

title: Prevalence of heterophoria and associations with refractive error, heterotropia and ethnicity in Australian school children
abstract: To establish the prevalence of heterophoria and its association with refractive error and ethnicity in a population-based study of Australian schoolchildren.  The Sydney Myopia Study is a stratified, random cluster (school-based) sample of 4093 students (examined: 2003–2005). Two samples aged 6 (n=1692) and 12 years (n=2289) without heterotropia were included. Prevalent heterophoria was assessed using cover un-cover and prism bar alternate cover testing at 33 cm and 6 m distance fixation. Cycloplegic autorefraction (1% cyclopentolate) was performed. Significant refractive error was defined as ≤−0.50SE and ≥+2.00SE.  Exophoria was highly prevalent at near fixation (age 6: 58.3%, age 12: 52.2%). Orthophoria predominated at distance fixation (age 6: 85.4%, age 12: 90.9%). Hyperopia was associated with esophoria at near (age 6: OR 1.7, 95% CI 1.1 to 2.8, age 12: OR 2.9, CI 1.1 to 2.8) and distance fixation (age 6: OR 9.7, CI 3.5 to 26, age 12: 9.6 OR, CI 4.2 to 22). Myopia was associated with exophoria at near (OR 2.1, CI 1.5 to 2.7) and distance fixation (OR 3.1, CI 2.1 to 4.4) for 12-year-old children only. Exophoria was more frequent in children of East Asian than European Caucasian origins, even after adjusting for refraction; at near (age 6: OR 1.4, CI 1.0 to 2.0, age 12: OR 1.4, CI 1.0 to 1.9) and distance (age 12: OR 1.7, CI 1.1 to 2.7).  Contrary to other studies, exophoria, not orthophoria, was predominant for near. Exophoria was more prevalent in children of East Asian origin. Longitudinal studies are needed to establish if incident heterotropia is preceded by heterophoria.

title: Portsea Modified Clinical Technique: Results from an Expanded Optometric Screening Protocol for Children
abstract: The results from screening 5,597 Australian school children using the Portsea Modified Clinical Technique (PMCT) are presented. The new protocol provides information about visual acuity, refractive status, strabismus, heterophoria, ocular motility, convergence, accommodative facility, fusional vergence facility, stereopsis, colour vision and ocular health. 
 
 
 
Population statistics have been determined for refraction, heterophoria, convergence insufficiency, accommodative infacility and vergence infacility. 
 
 
 
The screening results are compared to those from previous studies where possible.

title: Referral rates for a functional vision screening among a large cosmopolitan sample of Australian children
abstract: The aim of this study was to investigate the incidence of functional vision problems in a large unselected cosmopolitan population of primary school‐age children and to investigate whether constant clinical criteria for functional vision problems would be implemented by the practitioners involved in the screening. Refractive errors, near point of convergence, stereopsis, strabismus, heterophoria and accommodative facility were assessed for 2697 children (3–12 years) of varying racial backgrounds living in Australia. The spherical component of the refractive error ranged from −7.75 to +9.50 D (mean +0.54 D, ±0.79) with a distribution skewed towards hypermetropia; astigmatism ranged from 0 to 4.25 D (mean −0.16 D, ±0.35). There was a trend towards less hypermetropia and slightly more astigmatism with age. Mean near point of convergence was 5.4 ± 2.9 cm, heterophoria at far and near was 0.12 ± 1.58Δ exophoria and 1.05 ± 2.53Δ exophoria, respectively, 0.55% of children exhibited vertical phoria at near >0.5Δ, accommodative facility ranged from 0 to 24 cycles per minute (cpm) (mean 11.2 cpm, ±3.7), stereopsis varied from 20 to 800 s (′′) of arc with 50% of children having 40′′ or better. The prevalence of strabismus was particularly low (0.3%).

title: Strabismus and Binocular Functions in a Sample of Swedish Children Aged 4–15 Years
abstract: To investigate strabismus, head posture, nystagmus, stereoacuity, ocular motility, near point of convergence (NPC) and accommodative convergence to accommodation ratio (AC/A) in a sample of Swedish children.  A prospective cross-sectional study was carried out on 143 children, 4–15 years of age.  Heterotropia was found in five children (3.5%), four with esotropia and one with exotropia. One child with esotropia had a slight overaction of both inferior oblique muscles. Heterophoria was found in 37 children (26%) at near and/or distance fixation and it was four times more common at near than at distance. In 29 children, heterophoria was found at one distance only and orthophoria at the other. Orthophoria at both near and distance fixation was noted in 101 children (70.5%). The near point of convergence was ≤6 cm in 97% of the children and 97% had stereoacuity of 60″ or better. In the whole group, the median AC/A ratio calculated with the heterophoria method was 5.6/1 prism diopters/diopters (PD/D) and with the gradient method, 1.3/1 PD/D. No anomalous head postures or nystagmus were observed and all children had normal versions.  In this study, 143 well-defined children were investigated with a battery of accurately described tests, commonly used in clinical practice. These results are in agreement with those of other studies examining one or few variables in larger populations and the authors therefore conclude that their results may be used for comparisons with different patient groups.

title: Asthenopia in Schoolchildren, Orthoptic and Ophthalmological 
Findings and Treatment
abstract: The aim of this study was to describe the orthoptic and ophthalmological findings in schoolchildren with asthenopia, to correlate them with asthenopic symptoms and to evaluate the effect of treatment. One hundred and twenty schoolchildren, aged 6–16 years, were included in the study. They were all referred by school nurses, for asthenopic symptoms. An orthoptic and ophthalmological assessment was performed. The main diagnoses were accommodative insufficiency, convergence insufficiency, refractive errors, and latent strabismus. Reading glasses could help 98% of the schoolchildren with reduced accommodation, and 94% of the children with refractive errors and heterophorias were helped with appropriate spherical, cylindrical and prism correction. Convergence exercise reduced the symptoms in all patients with convergence insufficiency. Ninety-three percent of all 120 schoolchildren were symptom free 3–6 month after treatment had started. By an orthoptic and ophthalmological examination abnormalities in schoolchildren with asthenopia related to visual problems can be identified. Most of the children were relieved from their symptoms by giving adequate glasses, convergence exercises and surgery.

title: Orthoptic Findings and Asthenopia in a Population of Swedish Schoolchildren Aged 6 to 16 Years
abstract: To determine the prevalence of refractive errors and binocular disorders in relation to asthenopia in a representative population of Swedish schoolchildren.  The study population included 216 schoolchildren, 60 in grade 1 (age 6–7 years), 96 in grade 4 (10–12 years) and 60 in grade 8 (14–16 years). Asthenopia was evaluated by questionnaire. Visual acuity was tested for distance and near, uncorrected and with the best subjective refraction. Refraction in cycloplegia and an orthoptic assessment was performed.  Asthenopia was reported in 23.1% of schoolchildren; all but two of these schoolchildren had an abnormal eye examination. Asthenopia was related to uncorrected visual acuity ≤ 0.65 (13.9%*) and myopia (8.8%*). No significant correlation could be found to accommodative or convergence insufficiency.  Asthenopia was significantly associated with uncorrected visual acuity ≤ 0.65 and with myopia (spherical equivalent −0.50 D or less) among Swedish schoolchildren.

title: Relationship between accommodative and vergence dysfunctions and academic achievement for primary school children
abstract: The purpose of this study was to investigate the prevalence and types of non‐strabismic accommodative and/or vergence dysfunctions in primary school children, and to determine the relationship of these dysfunctions to academic achievement. A total of 1031 parents and their children aged 9–13 years responded to the College of Optometrists in Vision Development Quality of Life (COVD‐QOL) questionnaire. Of these, 258 children whose visual symptom scores were ≥20 were identified for further evaluation. Comprehensive eye and vision examinations were provided to the children who met the eligibility criteria (114 of 258): eligible symptomatic children were those without amblyopia, strabismus, ocular and systemic pathology, and contact lens wear. Children were also excluded if they had visual acuity poorer than 20/25 in either eye or vertical phoria >1 prism diopter. The results showed that 82 of 114 (71.9%) of criteria‐eligible symptomatic primary school children had non‐strabismic accommodative and/or vergence dysfunctions. In addition, a significant relationship was found between these dysfunctions and academic scores in every academic area (reading, mathematics, social science and science) in the total sample. Therefore, accommodative and vergence functions should be tested for all school children who have visual symptoms and/or academic difficulties. Additional study is needed to determine if improvements of accommodative and vergence functions also improve academic achievement.

title: The Relationship Between Convergence Insufficiency and School Achievement
abstract: Schoolchildren (735) between the ages of 7 and 14 were examined for convergence ability. Nine percent had an objective near point of convergence of more than 10 cm and 10% had a subjective near point of convergence of more than 10 cm. The recovery point was greater than 15 cm for 9% of the subjects when measured objectively and 12% subjectively. The sample was analyzed with regard to age, sex, and IQ. There was no significant difference between children who showed convergence insufficiency and those who did not with regard to school results in their mother tongue and in their grade point average.

title: Accommodation and vergence status among the 3rd and 4th graders in a mainstream school in Gauteng
abstract: The data presented in this paper is obtained from the study on the prevalence of visual deficien-cies in mainstream and learning disabled schools which revealed no difference in the prevalence of visual deficiencies in both schools. One of the objectives of this study was to determine the visual status of each learner in each of the two groups (mainstream and learning disabled). The findings of the study revealed that both groups presented with different visual deficiencies including accommodation, vergence deficiencies and poor ocular motilities which can contribute towards influencing the children’s learning skills negatively. The visual profile on the accommodative and vergence systems of the children from the mainstream school is further analysed in this paper to determine the prevalence of deficiencies in the 8-13 year-olds, and to support inclusion of the evaluation of these visual skills in the school vision screening protocol.  One hundred and twelve (112) children had an expanded vision screening, with eighty (80) from the mainstream school in Johannesburg aged 8-13 years. The expanded vision screeningincluded the measurement of visual acuity (Snellen Acuity), refractive error (static retinoscopy), accommodation (accuracy, facility and amplitude), evaluation of the vergence system (accuracy, facility and amplitude) and ocular motilities (direct ob-servation). Of the 80 children from the mainstream school, only 73 children’s results were consideredlearning performance of children, especially those of school-going-age. The study therefore supports the expanded vision screening of all school-going-children in South Africa to include visual efficiency skills (accommodation and vergence systems) for appropriate and early identification of the barriers and seven subjects were excluded due to their poor responses to the tests.Kolmogorov-Smirnov test was utilized to assess the normality of distribution of accommodative and vergence status of children from the mainstream school in Gauteng. Depending on the outcome of the normality, the T-test was used to analyse the data. The distribution of accommodative and vergence status (amplitudes and facilities) were found to be different from the normal distribution due to p-values found to be less than 0.05.  The results indicated that 12.3% had poor accommodation facility, 10% had poor accommodation amplitude, 17% had poor convergence amplitude and 21.9% had poor vergence facility. The prevalence of poor vergence facility was found to be 21.9%, higher than all the visual efficiency skills evaluated. However, the co-existence of both accommodative and vergence dysfunctions was not found, since subjects presented with either accommodative (isolated) or vergence (isolated) dysfunctions.  The results considered were for tests performed subjectively, and therefore that could have led to the identified statistical outliers (due to inconsistent responses) in the analysis of data for the prevalence of poor accommodative (12.3%) and vergence (21.9%) facility. The prevalence of accommodative and vergence dysfunctions although low in some instances is a concern. There is definitely a need for early identification of visual deficiencies that can impact negatively on the to learning. (S Afr Optom 2012 71(1) 22-31)

title: Convergence insufficiency and its current treatment
abstract: and controversy has existed concerning the management of convergence insufficiency. Only recently there have been significant scientific studies published that compare the effectiveness of the commonly prescribed treatments. This paper reviews the most recent research and literature on convergence insufficiency and its treatment.  The first large-scale placebo-controlled, randomized clinical trials to study the various treatments of convergence insufficiency have recently been published. Current research compares the effectiveness of base-in prism glasses, pencil push-ups, and vision therapy in reducing the signs and symptoms of convergence insufficiency and suggests that orthoptic therapy is the most efficacious treatment for convergence insufficiency.  Intensive orthoptic therapy is the treatment of choice for convergence insufficiency. Pencil push-ups and use of accommodative targets have a role in the treatment of convergence insufficiency when used as part of a more intensive orthoptic program. Base-in prism glasses should be reserved for reduction of symptoms in the presbyopic population.

title: Comparison of near fusional vergence ranges with rotary prisms and with prism bars.
abstract: Common methods for determination of fusional vergence ranges make use of rotary prisms in the phoropter or prism bars out of the phoropter. This study compared near fusional vergence ranges with rotary prisms with those with prism bars.



Fifty young adults served as subjects. Odd-numbered subjects had rotary prism vergences performed before prism bar vergences. For even-numbered subjects, prism bar vergences were done first. Base-in (BI) vergences were done before base-out (BO) vergences with both rotary prisms and prism bars. A coefficient of agreement was calculated by multiplying the standard deviation of the individual subject differences between rotary prisms and prism bars by 1.96, to approximate the range within which the 2 tests would agree 95% of the time.



The lowest coefficient of agreement was 7.3Δ for the BI recovery. The others were high, ranging from 15.4Δ for the BO recovery to 19.5Δ for the BO break.



Fusional vergence ranges determined by prism bars out of the phoropter cannot be used interchangeably with those determined by phoropter rotary prisms for the purpose of follow-up on individual patients or for the purpose of comparison with norms.

title: REPEATABILITY AND VARIABILITY OF NEAR VERGENCE RANGES
abstract: The purpose of the following experiment was to assess weekly the repeatability of near vergence ranges in free-space (FS) and in the phoroptor (P) over a 10 week period. Three experienced adult subjects were tested. Near vergence ranges were obtained once a week for 10 consecutive weeks. The base-out (BO) and base-in (BI) blur, break, and recovery points were performed sequentially, as in clinical practice; measured three times and averaged. The BO and BI near vergence mean values and their variability in both the FS and P test conditions revealed relatively consistent and repeatable v alues o ver t ime. Intrasession variability, both within and across test sessions, was low. Differences were also noted when comparing response variability for FS versus P and for BI versus BO. Variability both within and across test sessions was generally consistently less than previously reported. This suggests that the mean values are relatively stable at independent sessions under careful test conditions. In this experienced group, the vergence values may approximate the optimal performance that can then be used for clinical comparison.

title: Research on the Relationship between Reading and Vision—What Does it Mean?
abstract: Clinicians and teachers who want to pragmatically utilize research that has sought to relate various aspects of visual functioning to reading are often confused by conflicting findings. This article reviews and interprets some of the literature that has investigated the relationships between refractive status and reading and between binocular status and reading. These bodies of investigation are presented as being representative of studies that have explored the relationships between other visual entities and reading both in terms of basic research design and apparent inconclusiveness. The point is made that a major contributory factor to the general inability of the research to more definitively relate vision to reading has not been faulty design or statistical treatment but rather the way most researchers have chosen to characterize the visual process. Recommendations are made for more meaningful future research.

title: Effect of heterophoria type and myopia on accommodative and vergence responses during sustained near activity in children
abstract: The influence of phoria-type and myopia on changes to vergence and accommodation during prolonged near-task was examined in 53 children. Participants were classified into phoria and refractive categories based on near phoria and cycloplegic refraction respectively. Measures of near phoria, binocular (BA) and monocular accommodation (MA) were obtained before and during a 20 min task when children binocularly fixated a high-contrast target at 33 cm through best corrective lenses. Vergence adaptation and accommodative adaptation were quantified using changes to near phoria and tonic accommodation respectively. The direction and magnitude of vergence adaptation was modified by the phoria-type (p<0.001). Emmetropic exophores displayed convergent (less exo than baseline) adaptation while esophores showed divergent shifts (less eso than baseline) in phoria upon prolonged fixation. Myopic children also followed a similar pattern but showed greater divergent (or less convergent) shift (p<0.001) in vergence adaptation for all phoria categories compared to emmetropes. Phoria-type also influenced the pattern of BA vs. MA (p<0.001) such that exophores showed BA>MA while esophores showed MA>BA in both refractive groups. Accommodative adaptation was higher in myopes (p=0.010) but did not demonstrate a significant effect of phoria (p=0.4). The influence of phoria-type on vergence adaptation and the pattern of BA vs. MA relates primarily to the varying fusional vergence demands created by the direction of phoria. The greater divergent (or less convergent) shift in vergence adaptation seen in myopes (compared to emmetropes) could be attributed to their higher accommodative adaptation. Nevertheless, the adaptive patterns observed in myopic children do not appear to explain their high response AV/A ratios identified as a risk factor for myopia development.

title: Critically Reviewing the Ophthalmic Literature
abstract: In the current era, where optometry's scope and very definition are evolving, the practitioner's ability to evaluate critically the profession's clinical and basic science literature is crucial. This paper reviews the components of a scientific paper both in theory and by specific example. Emphasis is placed on reading the literature without accepting it at face value, including the description of the study designs frequently encountered in clinical research, the features of a study design that make it appropriate or inappropriate to answer the central hypothesis, and a brief introduction to the common pitfalls of routinely used statistical analysis.

title: Research Design Explained
abstract: 1. Psychology, Science, and You. 2. Ethics and Validity. 3. Generating and Refining Research Hypotheses. 4. Reading and Evaluating Research. 5. Measuring and Manipulating Variables: Reliability and Validity. 6. Beyond Reliability and Validity: The Best Measure for Your Study. 7.  The Simple Experiment. 11. Expanding the Simple Experiment: The Multiple-Group Experiment. 12. Expanding the Experiment: Factorial Designs. 13. Matched Pairs, Within-Subjects, and Mixed Designs. 14. Single-n Designs and Quasi-Experiments. 15. Putting It All Together: Writing Research Proposals and Reports.

title: The Chicago Guide to Writing about Numbers
abstract: Earning praise from scientists, journalists, faculty, and students, The Chicago Guide to Writing about Numbers has helped thousands of writers communicate data clearly and effectively. Its publication offered a much - needed bridge between good quantitative analysis and clear expository writing, using straight forward principles and efficient prose. With this new edition, Jane E. Miller draws on a decade of additional experience and research, expanding her advice on reaching everyday audiences and further integrating non-print formats. Miller opens by introducing a set of basic principles for writing about numbers, then presents a toolkit of techniques that can be applied to prose, tables, charts, and presentations. Throughout, she emphasizes flexibility, showing writers that different approaches work for different kinds of data and different types of audiences. The second edition adds a chapter on writing about numbers for lay audiences, explaining how to avoid overwhelming readers with jargon. Also new is an appendix comparing the contents and formats of speeches, research posters, and papers, to teach writers how to create all three without starting each from scratch. An expanded companion website includes new resources such as slide shows and podcasts that illustrate the concepts and techniques, along with an updated study guide of problem sets and course extensions. This continues to be the only book that brings together all the tasks that go into writing about numbers in one volume. Field-tested with students and professionals alike, this holistic book is the go - to guide for everyone who writes or speaks about numbers.