Draft #2: October 14, 1999

 

 

OPTOMETRIC CLINICAL PRACTICE GUIDELINE

 

CARE OF THE PATIENT WITH LEARNING RELATED

VISION PROBLEMS

 

 

Reference Guide for Clinicians

 

 

Prepared by the American Optometric Association Consensus

Panel on Care of the Patient with Learning Related Vision Problems:

 

Ralph P. Garzia, O.D., Principal Author

Eric J. Borsting, O.D.

Steven B. Nicholson, O.D.

Leonard J. Press, O.D.

Mitchell Scheiman, O.D.

Harold A. Solan, O.D.

 

 

Reviewed by the AOA Clinical Practice Guidelines

Coordinating Committee:

John F. Amos, O.D., M.S., Chair

Thomas L. Lewis, O.D., Ph.D.

Stephen C. Miller, O.D.

 

 

Approved by the AOA Board of Trustees

 

 

© American Optometric Association

243 N. Lindbergh Blvd., St. Louis, MO 63141-7881

 

 

Printed in U.S.A

TABLE OF CONTENTS

 

INTRODUCTION

  1. STATEMENT OF THE PROBLEM
  1. General Considerations
    1. Effects
    2. Definition
    3. Encountered Problems
    4. Diagnosis
    5. Reading disabilities and Dyslexia
    6. Visual Efficiency Skills and Learning
    7. Visual Information Processing Skills and Learning
  1. Epidemiology
  2. Course
  3. Early Detection

II. CARE PROCESS

  1. General Considerations
  2. Case History
  3. Visual Efficiency Skills Evaluation
    1. Visual Acuity
    2. Refraction
    3. Oculomotor System
    4. Accommodation-Vergence Function
    5. Visual System Integrity

D. Visual Information Processing Evaluation

    1. General Considerations
    2. Visual Spatial Orientation Skills
      1. Bilateral Integration
      2. Laterality and Directionality
    1. Visual Analysis Skills
    2. a. Visual Discrimination

      b. Visual Figure-Ground

      c. Visual Closure

      d. Visual Memory and Visualization

      e. Visual-Motor Integration

      f. Eye-Hand Coordination

      g. Auditory-Visual Integration

    3. Visual-Verbal Integration

E. Assessment and Diagnosis

F. Management

G. Parent and Patient Education

H. Supplemental Testing

I. Magnocellular Pathway Deficit

III. CONCLUSION

IV. REFERENCES

V. APPENDIX

Joint Organizational Policy Statement on Vision, Learning and Dyslexia

ICD-9-CM Classification of Vision Related Learning Disabilities

Glossary

INTRODUCTION

Optometry has a long history of caring for individuals with learning problems.1-3 Parents, teachers, and therapists have sought diagnostic evaluation to determine if a vision problem could be a contributing factor to A learning problem. In addition, intervention strategies developed by optometry have become incorporated into conventional therapeutic approaches for these individuals. Doctors of Optometry function as members of a multidisciplinary team of health care practitioners and special education professionals in the comprehensive care of individuals with learning problems.4-5 The Joint Organizational Policy Statement on Vision, Learning and Dyslexia addresses these issues (see Appendix 1).6

This Optometric Clinical Practice Guideline on Care of the Patient with Learning Related Vision Problems describes appropriate evaluation methods and management strategies to reduce the risk of vision problems interfering in the learning process. It contains recommendations for timely diagnosis, intervention, and, when necessary, referral for consultation or treatment by another health care provider or the educational system. This Guideline will assist Doctors of Optometry in achieving the following goals:

system about the nature of learning related vision problems and the availability of treatment

I. STATEMENT OF THE PROBLEM

A. GENERAL CONSIDERATIONS

  1. Effects
  2. Learning problems are a public health issue of an increasingly significant proportion.7 They can decrease the quality of life for the individual, delay academic achievement, and reduce employment and earnings opportunities.8,9 Self-esteem and peer relationships can be negatively influenced.10-12 There is also the possibility for lasting effects on family function with stresses placed on community and family financial and service resources.13 Undetected and untreated vision problems are of great concern because they can interfere with the ability to perform to one's full learning potential.6 These are learning related vision problems.

  3. Definition
  4. Learning related vision problems are deficits in two broad visual skill levels: visual efficiency skills and visual information processing skills.14 Visual efficiency skills are the basic visual neurophysiological processes which include visual acuity (and refractive error), accommodation, vergence and ocular motility. Visual information processing skills involve higher brain functions including the non-motor aspects of visual perception and cognition, and their integration with motor, auditory, language, and attention systems.

  5. Encountered Problems
  6. Many different forms of learning problems are encountered in optometric practice, the most severe involve learning disabilities. In 1975 the Education for All Handicapped Children Act PL 94-142 defined learning disabilities as a disorder in one or more of the basic psychological processes involved in understanding or in using spoken or written language, which may manifest itself in an imperfect ability to listen, think, speak, read, write, spell, or do mathematical calculations. This definition has been incorporated into the 1990 Individuals with Disabilities Act (IDEA).

    Many individuals have mild or circumscribed learning problems that are not of sufficient magnitude to be classified formally as learning disabilities but nevertheless may have significant learning related vision problems.

    Learning disabilities are a heterogeneous group of disorders that result in significant difficulties in academic achievement. Learning problems can be in spoken language as delays, disorders, or discrepancies in listening and speaking (vocabulary/articulation); in written language as difficulties with reading, writing, or spelling; in mathematics as difficulties in performing math functions or comprehending basic concepts; and in reasoning with difficulties in organizing and integrating thoughts, and turning them into effective actions.15 Attention deficits with (ADHD) or without (ADD) hyperactivity disorder frequently share a comorbidity with learning disabilities.16-18 Other associated traits like impulsiveness, low frustration tolerance, and difficulties with social interactions and situations are also frequently seen.19,20

    There is not a singular clinical profile of an individual with learning disabilities and the definition does not identify or describe a specific individual with a specific problem.

    Nor is there a unitary deficit that accounts for all of the expressions of the disorder, despite many attempts to do so.

    Learning related vision problems are deficits in visual efficiency and visual information processing skills. Visual efficiency problems encountered are uncorrected refractive error, dysfunctions of accommodation and vergence control systems - and their interactions - and ocular motility. Accommodative and vergence dysfunctions can be primary deficits or secondary to uncorrected refractive error. Isolated visual efficiency deficits are relatively uncommon, with most patients presenting with multiple deficits. A comprehensive description of accommodative and vergence dysfunctions can be found in the Optometric Clinical Practice Guideline for Care of the Patient with Accommodative and Vergence Dysfunction.21 Visual information processing problems encountered are delays or deficits in visual spatial orientation, visual analysis -- which encompasses non-motor visual perception -- and visual integration skills.

  7. Diagnosis
  8. Learning disabilities are usually first suspected by a classroom teacher who observes persistent difficulties in some area of academic achievement. Formal diagnosis for learning disabilities is determined by each state and usually is made when a significant discrepancy exists between the potential for learning as defined by a test of intelligence and actual academic achievement. A 1.5 to 2 year discrepancy in the primary grades is usually considered significant. Diagnostic test batteries also include quantitative achievement tests in academic areas (e.g., reading, spelling), evaluation of expressive and receptive language function, and evaluation of sensory systems.22,23 It is commonly recommended that vision be evaluated to rule out potentially consequential deficits. Unfortunately, the definition of learning related vision problems is not universal among educators and other health professionals and is too frequently interpreted as visual acuity screening, measured at distance. Whereas distance visual acuity is relevant for such tasks as copying from the board, other aspects of vision involving efficiency and information processing are fundamental to reading, writing and other classroom and learning activities. Therefore, proper diagnosis of learning related vision problems requires a comprehensive evaluation of visual efficiency and visual information processing skills.

  9. Reading disability and dyslexia
  10. The majority of individuals with learning disabilities have reading disability as their primary deficit.24,25 The role of phonological processing deficits in the understanding of reading disability cannot be underestimated.26-29 These deficits are manifested in the failure to use or properly understand phonological information when processing written or oral language. This is seen in the inadequacy of phonemic awareness (synthesis, analysis, segmentation), the poor understanding of sound-symbol (or later grapheme-phoneme) correspondence rules, and the improper storage and retrieval of phonological information. There can also be difficulties with short and long term memory affecting comprehension.

    The use of the term dyslexia to describe some form of reading disability has been the subject of much discourse.30 Its use has ranged from the description of reading difficulties only associated with traumatic brain injury to a general synonym for all developmental reading disabilities. It is best understood as a neurocognitive deficit that is specifically related to the reading and spelling processes. There are two situations for which the term dyslexia now commonly applies. The first is when the reader has difficulty decoding words (i.e., single word identification) and encoding words (i.e., spelling).31 The second, and a frequent presentation in optometric practice, is when the reader makes a significant number of letter reversal errors, shows letter transpositions in words when reading or writing (e.g. sign - sing), and has left-right confusion.32-36

  11. Visual Efficiency Skills and Learning
  12. Visual efficiency skills are related to learning and the avenues for visual efficiency problems to impact learning potential are numerous.37-39 Eye discomfort may make it difficult to complete school tasks or homework assignments in a timely manner. Distraction or inattention may become secondary complications. An often overlooked effect is task avoidance. Serious asthenopia present during visual tasks can lead to less time on task, decreasing the opportunity for practice and learning, particularly in vocabulary development, comprehension, and reading mechanics. A harmful associative relationship between eye discomfort and the learning activity can develop, leading to disinterest and poor motivation for traditional learning activities. Blurred, diplopic, or distorted text can be expected to decrease word processing speed and efficiency, reducing reading rate, and compromising reading comprehension. There can also be decreased attention allocation for information processing, as attentional capacity is diverted to manage the visual efficiency problem at the expense of on-going processing required for learning. The proliferation of computer assisted instruction in the school setting, notwithstanding the dramatic increase in home computer use, has created an even greater demand for suitable visual efficiency skills.

  13. Visual Information Processing Skills and Learning

The importance of visual information processing skills for learning is self-evident.40-42 Visual information processing skills provide the capacity to organize, structure and interpret visual stimuli, giving meaning to what is seen. Veridical visual information processing leads to perceptual constancy, creating a stable and predictable visual environment. These are important attributes for every learning situation.40-42 Visual information processing skills considered separately and collectively are related to learning ability and contribute to the total variance in reading achievement.42-54 Individuals with learning problems can present with distinct visual information processing deficits.

B. EPIDEMIOLOGY

Estimates of the prevalence of learning problems among school-aged children range from 2-10 percent depending on the nature of the diagnostic process and the definitions applied by individual school districts.24,55,56 Nationally, approximately 5 percent of all children are diagnosed with learning disabilities, with an equal or greater number having milder learning problems. Learning disabilities account for nearly half of all children receiving special educational services. Of that number, as many as 75 percent have particular difficulties with reading. While it was previously thought that males were more affected than females, more recent evidence indicates an equal number of male and females are affected.57-59 Learning disabilities are both familial and heritable.60-62

Appraisals of the prevalence of learning related vision problems vary considerably, depending on the definitions, sample selection criteria, and the analytical methods used. At least 20 percent of individuals with learning disabilities have been found to have a prominent visual information processing problem.63-66 The prevalence of visual efficiency problems is thought to be in the 15-20 percent range.67-69 Accommodative dysfunctions have been reported to occur in 60 to 80 percent of individuals with vision efficiency problems, with accommodative insufficiency the most prevalent type.21 Convergence insufficiency is the most common vergence anomaly. 21

C. COURSE

Although some behaviors commonly associated with learning problems may occur before a child enters school, learning disabilities do not begin to be formally diagnosed until the end of kindergarten or during first grade because formal academic instruction begins at this time.

During the preschool years, failure to achieve developmental milestones may be the first indication or risk factor for the appearance of learning disabilities. Delays in gross and fine motor development, receptive and/or expressive language, particularly phonological processing, and visual information processing may be the antecedents to learning problems. The purpose of early screening and intervention programs is to identify children with developmental delays who may be at significant risk for learning problems.

With early diagnosis and appropriate and comprehensive intervention, the prognosis is good in a majority of cases. Symptoms of learning disabilities rarely disappear entirely and frequently persist into adult life.70-72

Sustained near work is a significant risk factor for the development of visual efficiency problems. Once developed, visual efficiency problems persist for extended periods of time, although their clinical presentation may change during periods of remission and exacerbation. This will be dependent on prevailing intrinsic and extrinsic influences.

Early academic instruction places a relatively greater demand on visual information processing skills. There is an emphasis on recognition, matching and recall. Periods of sustained near work are infrequent, with visual stimuli (i.e. letters, words) relatively large and spaced apart. Visual efficiency rises in relative significance later as reading demands increase, with the need for grade appropriate reading rate with comprehension, over more extended periods of time, with smaller and more closely spaced text.

Visual information processing deficits are usually considered developmental in nature. With maturation and experience there will be increases in performance, but the rate of progression of skill development continues to lag.

D. EARLY DETECTION

There is inconclusive evidence that learning related vision problems can be prevented to any substantial degree; the emphasis, therefore, has been on early detection. It is recommended that vision examinations be scheduled at 6 months, 3 years and at school entrance.73 At this time parents should complete a developmental questionnaire. If there is a history of developmental delay, a screening test like the Denver Developmental Screening Test can be performed. If visual information processing problems are suspected, a more extensive evaluation is necessary for the early identification of children at risk for the development of learning related vision problems.

Most school districts now conduct some form of developmental screening prior to school entrance. These tend not to explore visual information processing development as extensively as is needed. The majority of school vision screenings test only distance visual acuity and are woefully inadequate in detecting most learning related vision problems. Thorough eye and vision examinations during the preschool years and consistently throughout school continue to be the most effective approach to early detection of visual efficiency and information processing problems.

  1. CARE PROCESS
  1. GENERAL CONSIDERATIONS

Care of the patient with learning related vision problems involves a case history, an examination of visual efficiency skills, visual information processing ability and visual pathway integrity. The Optometric Clinical Practice Guideline for the Pediatric Eye and Vision Examination should be consulted for additional information.73

  1. CASE HISTORY

The case history is the initial component of the care process and an important part of making an appropriate diagnosis.74 A collection of demographic data usually precedes and supplements the history taking. A questionnaire completed by the parent or caregiver can facilitate the history process. Special attention is directed to developmental milestones and academic performance. Questions should be constructed to define the specific nature of the learning and vision problems and used as a guide for the subsequent testing sequence. Information obtained directly from teachers or therapists can be helpful.

Language delays are commonly found in individuals with learning problems. As a result, sufficiently detailed descriptions of learning or visual symptoms obtained directly from the patient may be lacking. This could result in an underestimation of the severity of the symptoms and should not be the exclusive source of such information.

A comprehensive patient history for learning related vision problems may include:

Chief concern or complaint

Patient visual history

Patient medical history

Exploration of risk factors: perinatal events, childhood illnesses

Developmental history

Gross motor, fine motor, language and personal-social milestones

Family history

Visual, medical and academic / educational

Academic/educational history

Previous assessments and interventions

Current assessment, interventions and placement

Occupational / physical therapy

Speech and language

Learning disability

Remedial reading

Behavioral

Current achievement levels

Reading, spelling, mathematics, writing

Academic / educationally related medical history

Pediatric

Neurological

Audiological

Medications

C. VISUAL EFFICIENCY SKILLS EVALUATION

Visual efficiency problems are related to learning achievement. An analysis of the literature on the subject indicates that refractive error, in particular hyperopia and significant anisometropia, accommodative and vergence dysfunctions, and eye movement disorders are associated with learning problems.75-85 Therefore, a thorough clinical investigation for the presence of these conditions in the individual with learning problems is important.

Other binocular vision disorders like constant strabismus and amblyopia, while extremely important functional vision disorders to diagnose and treat early, have not been found to be associated with learning problems.

Some patients with visual information processing deficiencies, particularly with discrimination and memory, may have difficulty making reliable responses during subjective testing. The practitioner may have to make necessary compensations or use alternative testing procedures to obtain relevant information. Reliance on objective findings for clinical decision making may be necessary.

  1. Visual Acuity

Assessment of visual acuity in patients with learning related vision problems should be measured monocularly and binocularly at distance and near point. Patients with sufficient verbal communication and alphabet knowledge can be tested using a Snellen chart. If difficulties are encountered, an assessment of visual acuity may include the following procedures:

  1. Refraction

The measurement of refractive error should include:

Because of the importance of detecting hyperopia - particularly latent hyperopia - proper fogging technique should be maintained during retinoscopy and subjective refraction. A cycloplegic refraction may be indicated if convergence excess or accommodative insufficiency is diagnosed.

  1. Oculomotor System

Oculomotor skills are typically evaluated by chairside tests of fixation stability, saccadic and smooth pursuit eye movements.86,87 In addition to investigating extraocular muscle function for patients with learning related vision problems, a qualitative analysis of oculomotor skills is also necessary. Deficiencies in oculomotor skills have been associated with learning problems.86-92 Although all learning tasks require sequences of fixation-saccade-fixation, it is also important to test pursuit eye movements. For one reason pursuits are vital for ball skills, sports related activities, and locomotion. For another, it has been proposed that an important part of the neurological control process for smooth pursuit eye movements is through the magnocellular pathway which has been shown to be deficient in individuals with reading disabilities.93-99

The following standardized observational rating systems have been developed:

For smooth pursuit testing, both of these systems involve tracking a target moving in a circle. Evaluation of performance is by gain (eye velocity in relation to target velocity) and the number of catch-up saccades to reacquire the target.

Both systems investigate predictive saccades between two fixed targets positioned centrally, equidistant from the midline. Hypometric inaccuracies are commonly found in individuals with poor saccadic eye movement control. Oculomotor deficiencies are frequently accompanied by excessive head and body movements (motor overflow). The clinical signs and symptoms of oculomotor deficiencies can be found in Table 1.

Table 1. Signs and Symptoms of Oculomotor Dysfunction

Assessment tools are available for a more quantitative evaluation of saccadic eye movements, albeit indirectly. These tests simulate reading using a rapid number naming strategy. In general, numbers are placed in horizontal spatial arrays to be read in a left-to-right and top-down fashion as occurs in normal reading. The time to complete the task and the number of errors are the clinical variables. Presumably, slower and/or error prone performance would be an indicator of poor saccadic eye movement control. These tests are norm referenced for patient grade in school and age, with a clear developmental course of skill improvement. The following are available:

Unfortunately naming tasks confound the issue between eye movement skill and naming speed because both are required to complete the test successfully. However, the DEM incorporates a subtest of naming speed for the parceling out of eye movement skill for a more specific clinical diagnosis, and for this reason it is the preferred application.

Infrared eye monitoring systems that directly measure eye movements during reading are also available (e.g. Visagraph II). Although these do not measure saccade dynamics (accuracy, latency) or main sequence, they can provide data on the number of fixations required to read a text sample, along with fixation duration, number of regressions and reading rate.

  1. Accommodation - Vergence Function

Evaluation of accommodation and vergence amplitude, facility, accuracy, consistency, and sustainability is a necessity and may include the following procedures:

The evaluation of accommodation and vergence should include assessment of both the range and facility of response. The ability to make rapid changes in accommodative and vergence response is important for school-related tasks (e.g., copying from the blackboard or note taking). Facility testing also probes sustainability of the response, important for extended near point activities (e.g., reading). The clinical signs and symptoms of accommodative and vergence dysfunctions can be found in Table 2.104 The Optometric Clinical Practice Guideline for Care of the Patient with Accommodative and Vergence Dysfunction can be referred to for more detailed assessment information.21

 

Table 2. Signs and Symptoms of Accommodative - Vergence Dysfunctions

  1. Visual System Integrity

An assessment of visual system integrity should include:

The standard testing methodology for the evaluation of visual system integrity can be used in patients with learning related vision problems. The slit lamp biomicroscope can be used to evaluate the anterior segment and binocular indirect ophthalmoscopy to evaluate the posterior segment.

D. VISUAL INFORMATION PROCESSING EVALUATION

1. General Considerations

Visual information processing skills to be tested are visual spatial orientation skills, visual analysis skills, including auditory-visual integration, visual-motor integration skills,105 and visual-verbal integration skills.105,106 When available, the use of norm referenced tests is preferred.107 Testing should be conducted uniformly according to the test instructions, including exact directions and methodology. Specified rule-based scoring procedures should be followed. Qualitative insights from observing the test taker's behavior can be important supplementary information for diagnosis and management. Attention to the task, the ability to understand the instructional set, cognitive style, problem solving ability, frustration tolerance, and excessive motor activity are some of the behaviors worthy of observation.

Testing should be conducted in a relatively quiet environment without interruption. Individuals with attention deficits may require rest periods between tests or multiple testing sessions. One or more tests in each category are recommended.

  1. Visual Spatial Orientation Skills

Visual spatial orientation skills involve the ability to understand directional concepts, both internally and projected into external visual space. It is the awareness of one's own position in space relative to other objects, as well as the location of objects relative to each other. It also includes body knowledge and control, and bimanual integration. These skills are important for balance and coordinated body movements, navigation in the environment, following spatial directions, and understanding the orientation of alphanumeric symbols. The clinical signs and symptoms of visual spatial orientation skill deficiencies can be found in Table 3.

Visual spatial orientation skills are frequently subdivided into bilateral integration, laterality, and directionality. Bilateral integration is the awareness and use of the extremities, both separately and simultaneously in unilateral and bilateral combinations. Laterality is the internal representation and sensory awareness of both sides of one's own body. Directionality is the ability to understand and identify right and left directions in external visual space, including orientational specificity of written language symbols.

Table 3. Signs and Symptoms of Visual Spatial Orientation Skill Deficiency

Visual spatial orientation skills can be evaluated by the following:

 

  1. Bilateral Integration

Body knowledge and control requires the conversion of a tactile stimulus into a motor response -- moving the extremities in response to touch -- while standing. Chalkboard circles require the simultaneous production of large circles with each hand on a large chalkboard, both symmetrically and reciprocally. These are both criterion references tests, scored by observing performance and comparing it to an age related criterion.

  1. Laterality and Directionality

The Piaget Right-Left Awareness Test is criterion referenced. It requires a response to verbal instruction to move a named extremity, and the placement of objects to the right or left of another object. The Reversals Frequency Test and the Jordan are both norm referenced and require the recognition of correctly oriented letters and numbers. The Reversals Frequency test has an execution subtest that evaluates the frequency of reversal errors that occur when writing letters and numbers from dictation.

  1. Visual Analysis Skills

Visual analysis skills have been commonly referred to as visual perception, which is an active process for locating, selecting, extracting, analyzing, recalling and manipulating relevant information in the visual environment. They represent one of the core skills for letter and number recognition, sight word vocabulary, and mathematical concepts. Visual analysis skills have traditionally been divided into several subcategories: visual discrimination, visual figure-ground perception, visual closure, visual memory and visualization. The clinical signs and symptoms of visual analysis skill deficiencies can be found in Table 4.

 

Table 4. Signs and Symptoms of Visual Analysis Skill Deficiency

a. Visual Discrimination

Visual discrimination is the awareness of the distinctive features of objects and written language symbols, including shape, orientation, and size. Visual figure-ground perception is the ability to select and process an object or a specific feature of an object from among a background of competitive stimuli. Visual closure is the capacity to accurately identify an object with an incomplete amount of its details and features available for analysis and processing. Visual memory is the ability to recognize or recall previously presented visual stimuli, either individually, grouped, or in a specific sequence.

Visual discrimination tests involve a match-to-sample paradigm, with the match sometimes involving variations in stimulus size or orientation. Visual discrimination may be tested with the following:

b. Visual Figure-Ground

These tests involve a match-to-sample paradigm, requiring the detection of the test stimulus embedded in a confusing background, or from among other superimposed stimuli.

Visual figure-ground may be tested with the following:

c. Visual Closure

These tests involve a match-to-sample paradigm, requiring the identification of the target stimulus from among incomplete forms. Visual closure may be tested with the following:

d. Visual Memory and Visualization

Visual memory is considered in two aspects: visual sequential memory and visual spatial memory. Visual sequential memory requires the recall of an exact sequence of letters, numbers symbols, or objects. Visual spatial memory requires the recall of the spatial location of a previously seem stimulus and the ability to identify or reproduce a previously seen stimulus. Visualization requires the ability to mentally manipulate visual images.

Visual memory may be tested with the following:

Visualization may be tested with the following:

The Spatial Relations test requires that a sample of a geometric segment of a square be completed by matching one of the possible responses that would complete the square. The correct response may not be in the proper orientation to complete the square and must be mentally rotated.

e. Visual-Motor Integration

 

Visual-motor integration or visually guided motor responses is the ability to integrate visual information processing with fine motor movements and translate abstract visual information into an equivalent fine motor activity, typically of the hand in copying and writing. Visual-motor integration involves three individual processes: the visual analysis of the stimulus, fine-motor control (or eye-hand coordination), and visual conceptualization which includes the integration process itself. Deficits in any one of these processes will influence the overall result. Testing eye-hand coordination is therefore important for a differential diagnosis. For example, if visual analysis and eye-hand coordination skills are in the normal range but performance in visual-motor integration is deficient, then the difficulties lie in the integration processing phase. The clinical signs and symptoms of visual-motor integration skill deficiency can be found in Table 5.

 

Table 5. Signs and Symptoms of Visual-Motor Skill Deficiency

Visual-motor integration is usually tested by requiring the copying of progressively complex geometric forms. The Wold Sentence Copy test is an exception in that it tests speed and accuracy in copying a sentence, a comparable activity to desktop copying tasks in the classroom. Visual-motor integration may be tested with the following:

f. Eye-Hand Coordination

Eye-hand coordination may be tested with the following:

The Grooved Pegboard involves the integration of tactile, visual and fine motor skills requiring manipulative dexterity. The task is to insert slotted pegs into a pegboard with holes with randomly rotated slots. As a timed test, it differentiates accuracy from automatic processing. The Eye Hand Coordination subtest requires an accurately drawn line within narrow channels, both straight and curved.

g. Auditory-Visual integration

Auditory-visual integration is the ability to match a chain of auditory stimuli (usually sounds) to a correct visual representation of that stimulus chain. This requires remembering the sequence and spacing of sounds and then integrating that information with the visual modality. This can also be viewed as a temporal-to-spatial association or integration task. Auditory-visual integration is an important skill for establishing the proper association of sounds with visual symbols, such as is required for learning letters and words. The clinical signs and symptoms of auditory-visual integration deficiency can be found in Table 6.

Table 6. Signs and Symptoms of Auditory-Visual Integration Deficiencies

difficulty with sound-symbol associations

difficulty with spelling

slow reading

Auditory-visual integration may be tested with the following:

The Auditory-Visual Integration Test requires that the examiner taps out a series of sounds with time delays placed between sound clusters. The task involves selecting the proper visual representation (dots) of the sequence of sounds and delays from choices printed on cards.

  1. Visual-Verbal Integration

Visual-verbal integration involves the rapid retrieval of a verbal label for a visually presented stimulus.108 This integration is also dependent on rapid visual processing of the stimulus. Visual-verbal integration skills are required for efficient reading, particularly speed of word identification. The visual and expressive language processes required for rapid naming of objects or alphanumeric characters are quite similar to those required for the identification and recognition of single words. Slow naming may be a reflection of the phonological processing deficiencies common among individuals with learning problems or a deficit in a separate cognitive process.108-113 Rapid automatized naming has predictive power for later word identification ability but not reading comprehension.113

This skill is usually tested by requiring the rapid naming of arrays of visually presented objects or numbers. The clinical signs and symptoms of visual-verbal integration skill deficiency can be found in Table 7.

Visual-verbal integration may be tested with the following:

Table 7. Signs and Symptoms of Visual-Verbal Integration Deficiencies

Difficulty learning the alphabet (letter identification)

Difficulty with spelling

Faculty sight word vocabulary (word recognition)

Slow reading

The vertical subtest of the Developmental Eye Movement Test (DEM) requires the rapid naming of numbers presented in four vertical columns of 20 numbers each. The Rapid Automatized Naming task requires the naming, as rapidly as possible presented items on a chart (colors, lower case letters, numbers, common objects). Each chart contains five rows of 10 stimuli. The Boston Naming Test is a confrontation naming task in which line drawings of familiar objects are to be named. It is not an automatized naming task, but this test allows for an indication of knowledge of the items.

E. ASSESSMENT AND DIAGNOSIS

All of the obtained data should be evaluated to establish one or more clinical diagnoses and develop a management plan. An examination of the case history, clinical signs and symptoms, testing results and behavioral observations, and a review of previous reports and present levels of care is necessary to accomplish this. Low test scores should be referenced to the expected signs and symptoms of that deficiency.

In the analysis of the obtained visual efficiency skills performance data, it is necessary to examine all of the data collectively by a standard clinical protocol rather than relying on a singular finding to arrive at a diagnosis. The Optometric Clinical Practice Guideline for Care of the Patient with Accommodative and Vergence Dysfunction can be consulted for lists and descriptions of common accommodative and vergence dysfunctions and methods of data analysis.21

For visual information processing testing the use of z (or standard) scores is recommended. This is the deviation of a specific test score from the mean expressed in standard deviation units. It allows the expression of any score as a percentile rank by referring it to a standard normal distribution. A test result with a z-score of 1.5 below the mean (percentile rank = 6.68) should definitely be considered anomalous and is clinically significant. Scores falling between 1.0 and 1.5 standard deviations below the mean should be considered suspicious and may be clinically relevant dependent on the overall clinical picture, the nature and type of the learning problem, and the level of overall cognitive function. Parents and schools systems often prefer the expression of performance as an age or grade equivalent or percentile rank. This allows the direct comparison to expected performance levels. It is important to relate visual information processing test results to the current level of cognitive function measured by IQ tests like the Weschler Intelligence Scale for Children (WISC-R). With low-average IQ, overall performance in visual information processing in this same range may not be indicative of a problem, but rather the expected level of performance.

F. MANAGEMENT

The goal of the management of learning related vision problems is to prepare the individual to take full advantage of the opportunities for learning. Optometric intervention is directed at improving visual function to its appropriate level117 and has been shown to be efficacious.21,82,118-125 It does not replace conventional educational programming but is a necessary complementary intervention to maximize the learning environment and the effectiveness of pedagogy. In most situations, optometric intervention for learning related vision problems is done in conjunction with other professionals involved in the management of the learning problem from an educational or medical perspective. Interdisciplinary communication, consultation and referral is vital for the most effective management of the individual with learning problems.

The management of learning related vision problems should be directed at the identification and treatment of a specific visual deficit. Expectations should be the reduction or elimination of the signs and symptoms that are associated with the particular visual deficit. The goals of intervention should be specific and not indefinite (e.g., to improve school performance) but problem oriented.

Learning related vision problems are usually managed in a progressive sequence. Treatment begins with consideration of refractive status. Careful attention should be paid to the correction of hyperopia and anisometropia because of their known association with learning problems. Even small amounts can be problematic.

Next, visual efficiency skill deficits should be treated aggressively with lenses, prisms, and vision therapy. The Optometric Clinical Practice Guideline for Care of the Patient with Accommodative and Vergence Dysfunction can be referred to for more detailed management recommendations.21 The specific goal for the treatment of visual efficiency skill deficits is an enhancement of the range, latency, accuracy, facility and sustainability of accommodative and vergence responses. At the conclusion of therapy, oculomotor skills should be more accurate with a lower incidence of accompanying head and body movement.

Correction of refractive error and treatment of visual efficiency dysfunctions can result in improved visual information processing skills.82 Nevertheless, the treatment of vision information processing deficits usually requires vision therapy. Therapy can begin concurrently with the later stages of visual efficiency therapy. If deficits in visual efficiency skills are minor, information processing therapy can begin at the outset. The approach is typically hierarchical, beginning with visual spatial orientation, then visual analysis and finally visual-motor integration. The goals of visual information processing therapy can be found in Table 7. Developing intrinsic motivation so that the patient becomes aware of increasing mastery of the skill being acquired is an important part of the therapy program.

Vision therapy is usually conducted with a combination of office based and home therapy. One-two office visits/week for 12-24 weeks may be required for uncomplicated cases. Each office therapy session usually begins with a review of the assigned home vision therapy. This should include a demonstration of the procedures and an indication of compliance. Home vision therapy can be 4-5 days/week for 20-30 minutes each time. Home vision therapy is an important adjunct to office based therapy for overall success. Home therapy provides continuity of care, with opportunities for practice and additional experience, may reduce the number of office visits required, and reduces the potential for regression. Many vision therapy techniques and procedures are available to address visual information processing problems.126 Several compilations can be consulted.117,127-132 In addition, several computer therapy programs are now available.

After this initial period of therapy, a re-evaluation should be performed using the same visual information processing tests that had been employed previously, with an exploration of improvements in clinical signs and symptoms. An improvement of test performance of z 1.5 should be expected to be considered statistically significant.116 If necessary, additional therapy may be indicated if clinical signs and symptoms -- although improved -- persist to some degree. If sufficient progress has been made, and the major therapeutic goals for visual information processing skill enhancement and reduction in clinical signs and symptoms have been achieved, a home based maintenance program is recommended. This can include practicing a few procedures 2-3 times / week for 10-15 minutes each time for a 3 month period.

 

Table 7. Goals for Vision Information Processing Therapy

 

 

In some cases referral to another health care professional or the educational system may be indicated when underlying neurological problems, cognitive deficits or emotional disorders are suspected. Occupational or physical therapy may be complimentary to optometric vision therapy when severe deficiencies are noted.

G. PARENT AND PATIENT EDUCATION

Discussion and communication with the parents or caregivers should occur at the end of the examination to review the examination outcomes. This should begin with a review of the chief complaint. An explanation of the nature of the vision problem and its relationship to the presenting signs and symptoms is necessary. The management plan and prognosis should be considered. Communication with other education professionals about the diagnosis, proposed management plan and expected outcomes should be initiated. This should lead to a coordinated care effort with classroom teachers, special education teachers, and other therapists. The importance of continuing eye care should be discussed with parents or caregivers. Other education and health care professionals should be educated about the nature of the learning related vision problems present and their relationship to the extant learning difficulties.

H. SUPPLEMENTAL TESTING

There have been many attempts to subtype learning (reading) problems into homogeneous groups of individuals by identifying similarities in their performance profiles. This reasoning is related to neurocognitive models which assume that significant differences in auditory and visual processing abilities can account for different forms of learning problems. One popular approach is the achievement classification model which is based on performance in word recognition and spelling tasks. Standardized tests that are available include:

Both of these tests identify the reading problem from a reading recognition task with graded word lists of regular and nonregular words. A reading grade level is obtained from this task. Based on this reading performance, an individualized list of spelling words is selected from the sight-word vocabulary and from those that are not. An analysis of the types of spelling errors made is used to subtype the reading problem into dyseidetic, dysphonetic, or mixed type. The dyseidetic subtype is characterized by visual information processing deficits, including visual memory and visualization. These individuals have a limited sight word vocabulary and have an over-reliance on phonetic decoding strategies that interfere with efficient reading. The dysphonetic subtype is characterized by poor understanding and application of phonetic decoding rules. Visual information processing is relatively intact. However, importantly, this subtype has been associated with magnocellular visual pathway deficits.134

I. MAGNOCELLULAR PATHWAY DEFICIT

It has recently been shown that a deficient magnocellular pathway is associated with reading disabilities. There are several convergent lines of psychophysical, electrophysiological and anatomical evidence to support this conclusion.93-99,134-140 Compared to normal readers it has been found that in the population of disabled readers: visible persistence is prolonged for stimuli of low spatial frequency; contrast sensitivity is lower at low spatial frequencies; flicker sensitivity is reduced; temporal resolution and integration is poorer; the time course and strength of metacontrast masking functions are anomalous; and the effects of flicker masking are reduced. More recently it has been found that disabled readers are less sensitive to the detection of motion with reduced MRI responses to moving stimuli, and have abnormalities in reflexive, stimulus-induced visual attention.

A magnocellular pathway deficit could produce the perception of overlapping text or illusory text movement, disrupt the proper timing and accuracy of saccadic eye movements, the proper spatial and temporal disposition of visual attention, and the temporal order of visual processing of words. At the present time there are no standard clinical tests to evaluate magnocellular function that are readily available to most clinicians. The most promising are contrast sensitivity measures, visual evoked potentials using low contrast low spatial frequency stimuli, and motion detection paradigms.

III. CONCLUSION

Learning related vision problems are a collection of deficits in visual efficiency and visual information processing skills that have the potential to interfere with the ability to perform to one's full learning potential. These deficits may cause clinical signs and symptoms that range from asthenopia and blurred vision to skipping words and losing place when reading to delayed learning of the alphabet and difficulty reading and spelling. Vision related learning problems have a relatively high prevalence rate in the population. They respond favorably to the appropriate use of lenses, prisms, and vision therapy, either individually or in combination. Vision therapy is usually conducted with a combination of office based and home therapy.

It is essential that the diagnosis of learning related vision problem be accurate and thorough. It is likewise essential to discuss the diagnosis with parents and the patient, communicate with other professionals as required, and develop a management plan. Optometric intervention should be coordinated with other educational and health professionals in their management of the associated learning problem to establish the maximum opportunity for improvement.

 

 

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GLOSSARY

Accommodation is the ability to focus clearly on objects at various distances.

Auditory-visual integration is the ability to match a sequence of auditory stimuli to a correct visual representation of that stimulus sequence.

Bilateral integration is the awareness and use of the extremities, both separately and simultaneously in unilateral and bilateral combinations.

Directionality is the ability to understand and identify right and left directions in external visual space.

Dyslexia is a neurocognitive deficit that is specifically related to the reading and spelling processes.

Graphemes are the visual structure or representations of words.

Laterality is the internal representation and sensory awareness of both sides of one’s own body.

Learning disabilities are disorders in one or more of the basic psychological processes involved in understanding language, spoken or written, and includes the unexpected difficulties in learning in individuals who otherwise possess the intelligence, experience and opportunity considered for normal achievement.

Magnocellular pathway represents a processing pathway from the retina, through the lateral geniculate nucleus to visual cortex that is characterized by fast temporal and low spatial resolution and high motion sensitivity.

Oculomotor system refers to two types of eye movements, smooth pursuit and saccades, in addition to fixation maintenance.

Phonemes are the sounds that make up words.

Phonological processing refers to the rules associated with the sounds of the language. It includes the comparison of the beginning, middle and ending sounds of words, rhyme detection, sound vocalization and blending, among other skills.

Vergence is the disjunctive movement of the eyes in which the visual axes more toward each other of away from each other.

Vision related learning problems are deficits in visual efficiency skills and visual information processing skills that effect learning.

Vision therapy is a sequence of activities individually prescribed and monitored to develop efficient visual skills and processing.

Visual closure is the capacity to accurately identify an object with an incomplete amount of its details available for analysis.

Visual discrimination is the awareness of the distinctive features of objects and written language symbols.

Visual efficiency skills are the basic neurophysiological processes that include visual acuity, refractive error, accommodation, vergence and ocular motility.

Visual figure-ground perception is the ability to select an object or a specific feature of an object from among a background of competing stimuli.

Visual information processing skills are higher order functions including visual perception and cognition, and their integration with motor, language, and attention systems.

Visualization is the ability to mentally manipulate a visual image.

Visual memory is the ability to recognize or recall previously presented visual stimuli.

Visual-motor integration is the ability to integrate visual information with fine motor movements.

Visual spatial orientation involves the ability to understand directional concepts, both internally and projected into external visual space.

Visual-verbal integration is the rapid retrieval of a verbal label for a visually presented stimulus.