Biomedical subjects

Sherry L Fawcett

Publications and source records attributed to Sherry L Fawcett.

14 recordsLinked to original sources

PubMed2005

Testing distance stereoacuity with the Frisby-Davis 2 (FD2) test.

PURPOSE: To develop a presentation protocol for the new Frisby-Davis 2 (FD2) distance stereoacuity test. DESIGN: Prospective data collection. METHODS: Stereoacuity was tested monocularly and binocularly in 95 patients with a variety of strabismic and nonstrabismic conditions, using the FD2, employing a modified staircase procedure. The Preschool Randot Stereoacuity test and the near Frisby test were used to determine whether a patient was stereoblind. RESULTS: Under monocular conditions, 35 (37%) of 95 patients passed at least the largest disparity of the FD2 indicating a problem with monocular cues. The binocular protocol was then modified to include a monocular test phase. Using the new protocol, if a patient could achieve the same stereoacuity under monocular and binocular conditions, they were deemed to have no stereopsis. Testing 28 additional stereoblind patients using the new modified protocol revealed no false positives. CONCLUSION: The FD2 stereotest is a useful measure of distance stereoacuity, provided the presentation protocol accounts for monocular cues.

Adolescent↗

PubMed2005

Measurement of stereoacuity outcomes at ages 1 to 24 months: Randot Stereocards.

PURPOSE: The aim of the present study was to develop a simple, quick, and portable random dot stereoacuity test for measurement of binocular sensory outcomes during the first 24 months of life. METHODS: Vertical bar random dot vectographs were adapted for presentation in a "Teller Acuity Card" format, called the "Randot Stereocards." A forced-choice preferential looking protocol was used. Study participants included 386 healthy, term infants and children (normative cohort; age range: 1 month to 8 years) and 280 patients with common pediatric ophthalmic disorders (patient cohort; age range: 5 months to 9 years). RESULTS: Overall, the success rate for test completion in the normative cohort was 91.3%. By 4 months of age, normal infants' mean stereoacuity was about 600'' and, by 6 months, 200''. Mean stereoacuity further improved to about 100'' by 12 months and 70'' by 18 months. Normative results were similar to published data obtained with laboratory-based stereoacuity tests. Randot Stereocard data from normal children aged 2 to 6 years were similar to published normative data for the Preschool Randot Stereoacuity Test. In the patient cohort, concordance between the Randot Stereocards and the Preschool Randot Test was 87%; concordance between the Randot Stereocards and the Randot Test was 84%. CONCLUSION: The Randot Stereocards provide a simple, reliable, and valid method of obtaining a quantitative assessment of binocular vision in children up to 24 months of age for use in clinical trials and in clinical management.

Child↗

PubMed2005

An evaluation of the agreement between contour-based circles and random dot-based near stereoacuity tests.

INTRODUCTION: Monocular cues are present in the contour-based Titmus and Randot circles stereoacuity tests frequently giving rise to false-positive results in patients with abnormal stereoacuity. Stereoacuity derived using these 2 test types was compared to evaluate whether discrepancies between these tests were limited to the coarse/nil end of the stereoacuity spectrum or whether they were apparent across a wider range of possible stereoacuity scores, including levels of stereopsis equated with macular fusion. METHODS: Fifty-four normal volunteers and 91 patients with a history of anomalous binocular vision by a variety of conditions (eg, strabismus, monovision, or unilateral eye disease) participated. In each participant, stereoacuity was measured using the Titmus(c) circles, the Randot(c) (version 2) circles, and the Preschool Randot(c) Stereoacuity test. RESULTS: In patients with a history of anomalous binocular vision, better stereoacuity scores were acquired using the circles tests than the random dot-based Preschool Randot Stereoacuity test (Friedman repeated-measures analysis of variance on ranks, Chi-square = 99.3, P < 0.001; Student-Newman-Keuls Method, P < 0.05). Among patients with known binocular vision anomalies, stereoacuity score disagreement was evident across the entire range of measurable stereoacuity. CONCLUSIONS: Stereoacuity score discrepancies between the circles tests and the random dot based tests frequently cross categories (eg, fine vs. moderate or coarse stereopsis). Disagreement between the test types may reflect different underlying mechanisms by the different types of tests or confounding nonstereoscopic binocular cues in the Titmus and Randot circles test.

Adolescent↗

PubMed2005

The critical period for susceptibility of human stereopsis.

PURPOSE: To define the critical period for susceptibility of human stereopsis to an anomalous binocular visual experience. METHODS: Random dot stereoacuity was measured in 152 children with a history of onset of either infantile or accommodative strabismus before 5 years of age. In each of these populations and in the combined population, the critical periods for susceptibility of stereopsis are described using four-parameter developmental weighting functions. RESULTS: In children with infantile strabismus, the critical period for susceptibility of stereopsis begins at 2.4 months and peaks at 4.3 months. In children with accommodative esotropia, the critical period for susceptibility of stereopsis begins at 10.8 months and peaks at 20 months. When the data are combined across the two populations, the critical period begins soon after birth and peaks sharply at 3.5 months but shows continued susceptibility to at least 4.6 years. CONCLUSIONS: An anomalous binocular visual experience during early infancy severely disrupts stereopsis, yet the critical period for susceptibility of stereopsis extends through late infancy and early childhood and continues to at least 4.6 years of age.

Accommodation, Ocular↗

PubMed2005

Risk factors for accommodative esotropia among hypermetropic children.

PURPOSE: Identification of risk factors for accommodative esotropia may help to determine which children with hyperopia may benefit from early spectacle correction or preventive therapy. METHODS: Participants in the family history study were 95 consecutive patients, aged 18 to 60 months, with accommodative esotropia. Participants in the binocular sensory function study were a subgroup of 41 children enrolled in the family history study within 1 month of onset, while the esodeviation was still intermittent. Participants in the hypermetropia study were 345 consecutive patients, ages 12 months to 8 years, with refractive error of +2.00 D or greater and no esodeviation before age 12 months. RESULTS: In the family history study, 23% of children with accommodative esotropia had an affected first-degree relative, and 91% had at least one affected relative. In the binocular sensory function study, random-dot stereoacuity was abnormal in 41% of children, whereas an abnormal motion VEP, Worth 4-dot, or positive 4-PD base-out prism responses were present in 4% or less of the children. In the hypermetropia study, patients with a mean spherical equivalent of < +3.00 D and significant anisometropia had a 7.8-fold increased risk for accommodative esotropia over nonanisometropic patients. CONCLUSIONS: A positive family history, subnormal random-dot stereopsis, and hypermetropic anisometropia each pose a significant risk for the development of accommodative esotropia. Assessment of these risk factors in conjunction with refractive screening should help to identify those children who are most likely to benefit from early spectacle correction or preventive treatment.

Accommodation, Ocular↗

PubMed2004

Development of an instrument to assess vision-related quality of life in young children.

PURPOSE: Quality of life (QOL) instruments are increasingly utilized in ophthalmological research. Measuring vision-related QOL in young children is complicated by constantly evolving abilities related to normal growth and development. Our aim was to develop vision-related QOL instruments for children in different age ranges <==7 years, and to provide initial validation of these instruments. DESIGN: Cross-sectional study. METHODS SETTING: Multicenter. PATIENTS: 773 pediatric patients (age <==7 years) with a wide range of ophthalmological diagnoses. PROCEDURE: Questionnaire. A 61-item prototype instrument with a wide variety of items was applied to 403 consecutive patients. The usefulness of items was evaluated as a function of age in order to derive two age-group specific instruments and to find the age limit dividing the age groups. Thus, age-specific versions of a Children's Visual Function Questionnaire (CVFQ) were defined for ages <3 years and >/=3 years, and applied to a convenience sample of patients. OUTCOME: Subscale scores. Factor analysis helped identify underlying dimensions of the data, and corresponding subscales were defined. Validation was provided by examining the internal consistency reliability and by exploring the associations between scores and clinical characteristics. RESULTS: Subscales for General health, General vision, Competence, Personality, Family impact, and Treatment were defined, with internal consistency reliabilities ranging from 0.60 to 0.86. The association between subscales scores and age was weak, whereas strong correlations were found with the level of visual impairment and type of visual diagnosis. CONCLUSION: The CVFQ assesses the impact of visual impairment on children and their families, and is expected to become a useful tool for the pediatric vision research community.

Child↗

PubMed2004

Factors influencing stereoacuity outcomes in adults with acquired strabismus.

PURPOSE: Functional improvements of binocular vision after strabismus surgery in adults are common but not well understood. In a prospective study, factors associated with stereoacuity outcome in patients with strabismus acquired following binocular vision maturation were investigated. DESIGN: Prospective data collection. METHODS: Twenty-three patients aged 14 to 85 years with acquired strabismus were enrolled. Random dot stereoacuity was quantified using a battery of tests including the Randot Preschool Stereoacuity test, the Randot (version 2) shapes test, and the Randot Butterfly test. RESULTS: Ninety-six percent of patients achieved measurable stereoacuity following successful eye realignment. Better median stereoacuity is achieved in patients with the following characteristics: < or =12 months of constant strabismus (60 vs 400 seconds of arc with >12 months' strabismus, P < .001); a presurgical capacity for fine to moderate stereopsis (60 vs 400 seconds of arc with coarse or no measurable stereopsis, P < .005); a presurgical capacity for macular fusion (60 vs 400 seconds of arc with no measurable macular fusion capacity, P < .001); and postsurgical orthotropia (100 seconds of arc) or intermittent orthotropia (100 seconds of arc vs 2000 seconds of arc with 5 to 8 prism diopters (PD) of postsurgical residual strabismus, P < .05). CONCLUSION: Surgical correction of acquired strabismus is associated with recovery of stereopsis. Factors associated with stereoacuity outcomes include duration of strabismus and presurgical binocular vision capacity. A postsurgical correction of orthotropia or intermittent orthotropia supports better stereoacuity than a larger residual angle of strabismus subtending up to 8 PD of deviation.

Adolescent↗

PubMed2004

Predictive factors underlying the restoration of macular binocular vision in adults with acquired strabismus.

PURPOSE: To investigate whether macular binocular vision can be permanently lost following acquired strabismus and to identify predictive factors underlying its restoration. SUBJECTS AND METHODS: Twenty-three patients with strabismus acquired after binocular vision maturation were enrolled. Factors studied included duration of eye misalignment, age at treatment, pre-surgical strabismus type, pre-surgical diplopia, and pre-surgical capacity for binocularity. The restoration of macular binocular vision was evaluated between 1 and 3 years following successful eye re-alignment and was defined as 60 seconds of arc stereopsis or better on the Titmus circles and/or the Preschool Randot Stereoacuity test. RESULTS: Sixteen of 23 (70%) or 7/23 (30%) of patients achieved macular binocular vision following successful surgical eye realignment using the Titmus circles versus the Preschool Randot Stereoacuity test. Patients with < or =12 months constant eye misalignment were more likely to achieve macular binocular vision following treatment than patients with >12 months constant eye misalignment. CONCLUSIONS: Macular binocular vision continues to be susceptible to permanent loss in adult patients. Factors that are predictive of the restoration of macular binocular vision include duration of constant eye misalignment and the pre-surgical capacity for binocularity.

Adolescent↗

PubMed2003

Risk factors for abnormal binocular vision after successful alignment of accommodative esotropia.

PURPOSE: The purpose of this study was to identify clinical factors associated with abnormal binocular vision outcomes among children with accommodative esotropia (ET) whose eyes were successfully realigned with spectacles only or with spectacles and surgery. METHODS: The participants were 69 children with accommodative ET who were followed up prospectively from the time of diagnosis. Clinical factors examined in this study included high accommodative convergence-to-accommodation (AC/A) relationship, high hyperopia, anisometropia, age of onset, and duration of eye misalignment. Binocular vision was assessed using measures of stereopsis, fusional vergence, sensory foveal fusion, and motion visual-evoked potential (mVEP). RESULTS: Children with a high AC/A relationship are 2.2 times more likely to have an absence of fusional vergence than are children with a normal AC/A relationship. Children having a duration of constant eye misalignment >/= 4 months before being successfully treated are 4.6 times more likely to have abnormal stereopsis, 33 times more likely to have no stereopsis, 37 times more likely to have an absence of fusional vergence, 31 times more likely to have an absence of sensory foveal fusion, and 17 times more likely to have an asymmetric mVEP response than children with a duration of constant ET diagnosed at 0 to 3 months. CONCLUSIONS: Following successful eye alignment, as many as 75% of patients with accommodative ET had anomalous binocular vision. A high AC/A relationship poses a significant risk for abnormal fusional vergence only. A constant eye misalignment lasting >/= 4 months poses a significant risk for anomalous binocular vision on all measures studied.

Accommodation, Ocular↗

PubMed2003

Validity of the Titmus and Randot circles tasks in children with known binocular vision disorders.

PURPOSE: The Titmus and Randot (version 2) circles tests contain monocular form cues that may enable patients with binocular vision disorders to pass without any measurable stereopsis. The purpose of this study was to evaluate the validity of the Randot and Titmus circles tests for quantifying stereoacuity in children with known binocular vision disorders. METHODS: Participants included 170 consecutive children with diverse binocular sensory function ranging from fine to no measurable stereopsis. Stereoacuity was measured using the Randot circles, the Titmus circles, and the Randot Preschool Stereoacuity tests. RESULTS: Discrepancies between stereoacuity scores derived using either the Titmus or Randot circles tests and the Randot Preschool Stereoacuity test increased as a function of random-dot stereoacuity. Stereoacuity scores derived using the circles tests showed good agreement with random-dot stereoacuity when stereoacuity was 2.2 log seconds of arc (160 seconds of arc) or better, but they progressively overestimated stereoacuity for poorer random-dot stereoacuity scores. CONCLUSION: When measuring stereoacuity using either the Titmus or Randot circles tests in patients with known binocular vision disorders, stereoacuity scores > 2.2 log seconds of arc should be interpreted with caution because it is above this level of stereoacuity that the monocular form cues of each of the tests may invalidate the results.

Child↗

PubMed2003

Visual function in breast-fed term infants weaned to formula with or without long-chain polyunsaturates at 4 to 6 months: a randomized clinical trial.

OBJECTIVE: Breast-fed infants receive docosahexaenoic acid (DHA) and arachidonic acid (ARA) in their diet. Upon weaning, infants lose this dietary source of long-chain polyunsaturates because many commercial formulas do not contain these important constituents for neural membrane biogenesis. We evaluated the benefits of postweaning dietary supplementation of DHA + ARA on visual maturation. STUDY DESIGN: Healthy term infants (n = 61) were breast-fed to 4 to 6 months, then were randomly assigned to commercial formula or formula supplemented with DHA (0.36%) + ARA (0.72%). Measurements of red blood cell (RBC) fatty acids, visually evoked potential (VEP) acuity, and stereoacuity were done before and after weaning. RESULTS: At 1 year of age, RBC-DHA in the commercial formula-fed group was reduced by 50% from the weaning level, whereas there was a 24% increase in the DHA + ARA-supplemented group. The primary outcome measure, VEP acuity, was significantly more mature in supplemented infants at 1 year of age. Elevated RBC-DHA levels were associated with more mature VEP acuity. There were no significant diet-related differences in stereoacuity. CONCLUSIONS: These data extend through the first year of life the critical period in which a dietary supply of DHA and ARA can contribute in optimizing visual development in term infants.

Arachidonic Acid↗

PubMed2002

Risk factors for the development of accommodative esotropia following treatment for infantile esotropia.

PURPOSE: One aim of the study was to determine whether accommodative esotropia after surgical alignment in infantile esotropia occurs because a pre-existing accommodative component is unmasked at the time of surgery or whether it occurs as a sequela of infantile esotropia. A second aim of the present study was to examine risk factors for accommodative esotropia after surgery for infantile esotropia. METHODS: A total of 80 consecutive patients who were enrolled in a prospective study of infantile esotropia had been followed for more than 4 years and had achieved orthoposition were included. Twelve potential risk factors were examined: age at onset, initial esodeviation, initial refractive error, age at alignment, delay in alignment, presurgical glasses, amblyopia, additional surgical procedures, unstable alignment, increase in hypermetropia, peripheral fusion, and stereopsis. Mantel-Haenszel odds ratios were computed for each factor and were corrected to relative risks. RESULTS: Overall, 48 of 80 children (60%) developed accommodative esotropia at a mean age of 33 months. Increasing hypermetropia, delay in alignment, and poor stereopsis posed significant risks for accommodative esotropia. The remaining 9 factors were not associated with increased risk for accommodative esotropia. CONCLUSIONS: Accommodative esotropia is unlikely to be a pre-existing condition in most cases because the mean age of onset was 23 months postoperative and the prevalence of preoperative hypermetropia greater than +3.00 D was low. Both delay in alignment and stereopsis risk factors may reflect compromised binocular sensory status that allows accommodative esotropia to occur at low to moderate levels of hypermetropia. Identification of children treated for infantile esotropia who are at risk for accommodative esotropia may allow for prevention or early treatment.

Accommodation, Ocular↗

PubMed2002

Preschool Worth 4-Shape test: testability, reliability, and validity.

PURPOSE: The Worth 4-Dot is used to assess binocular fusion, but it is difficult to use with young children. We modified the Worth 4-Dot by replacing the circles with shapes while maintaining the same color configuration. The purpose of this study was to determine the testability, reliability, and validity of the Worth 4-Shape test. METHODS: Subjects aged 2 to 8 years and 4 patients aged over 8 years with best-corrected visual acuity of 20/40 or greater (n = 131 patients, n = 123 normals) attempted test and retest at 35 cm and 3m using the Worth 4-Shape and Worth 4-Dot. To provide a gold standard, medical history, bifoveal fixation, and stereoacuity were reviewed. RESULTS: Testability of the Worth 4-Shape was significantly higher than the Worth 4-Dot both in children aged less than 4 years (95.9% vs 79.5% at 35 cm, P <.001; 79.5% vs 55.1% at 3 m, P <.001) and older than 4 years (98.5% vs 88.6% at 35 cm, P <.001; 90.9% vs 82.4% at 3m, P =.04). Test-retest analysis found comparable concordance for the Worth 4-Shape and Worth 4-Dot tests (P >.3). The sensitivity and specificity of the Worth 4-Shape (92%, 97%) and Worth 4-Dot (90%, 94%) were comparable. Between-test analysis found 96% agreement between both tests at 35 cm and 97% agreement at 3m. CONCLUSIONS: The success rate for the Worth 4-Shape is higher than the Worth 4-Dot, especially in children aged less than 4 years, and has equivalent accuracy. The Worth 4-Shape test-retest reliability is high supporting its validity for use with young children.

Child↗

PubMed2002

A randomized controlled trial of long-chain polyunsaturated fatty acid supplementation of formula in term infants after weaning at 6 wk of age.

BACKGROUND: The critical period during which the dietary supply of long-chain polyunsaturated fatty acids (LCPs) may influence the maturation of cortical function in term infants is unknown. OBJECTIVE: The aim of the present study was to determine the relative importance for maturation of the visual cortex of the dietary supply of LCPs during the first 6 wk of life compared with that during weeks 7-52. DESIGN: A randomized controlled clinical trial of LCP supplementation in 65 healthy term infants who were weaned from breast-feeding at 6 wk of age was conducted to determine whether the dietary supply of LCPs after weaning influenced the maturation of visual acuity and stereoacuity. RESULTS: Despite a dietary supply of LCPs from breast milk during the first 6 wk of life, infants who were weaned to formula that did not provide LCPs had significantly poorer visual acuity at 17, 26, and 52 wk of age and significantly poorer stereoacuity at 17 wk of age than did infants who were weaned to LCP-supplemented formula. Better acuity and stereoacuity at 17 wk was correlated with higher concentrations of docosahexaenoic acid in plasma. Better acuity at 52 wk was correlated with higher concentrations of docosahexaenoic acid in plasma and red blood cells. No significant effects of diet on growth were found. CONCLUSION: The results suggest that the critical period during which the dietary supply of LCPs can influence the maturation of cortical function extends beyond 6 wk of age.

Age Factors↗