Biomedical subjects

E E Birch

Publications and source records attributed to E E Birch.

15 recordsLinked to original sources

PubMed1992

Probability summation of acuity in the human infant.

Raw data from two studies of monocular and binocular acuity development were used to determine whether a binocular acuity advantage as a function of age is predicted by probability summation and whether these predictions accurately describe the course of binocular acuity development. Two decision rules for the combination of the outputs of right eye and left eye "channels" were evaluated, the decision-threshold rule and the integration rule. Both decision rules predicted a binocular acuity advantage for infants and children aged 0-60 months. However, both rules failed to adequately describe the normal course of monocular and binocular acuity development. No binocular acuity advantage was found prior to 6 months of age while, after 6 months of age, binocular acuity was superior to monocular acuity by 0.12 log unit (0.4 octave). The absence of binocular acuity superiority prior to 6 months of age is consistent with suggestions by other authors that the immature human visual system combines information from the two eyes nonselectively.

Aging↗

PubMed1992

Extracting thresholds from noisy psychophysical data.

Psychophysical studies with infants or with patients often are unable to use pilot data, training, or large numbers of trials. To evaluate threshold estimates under these conditions, computer simulations of experiments with small numbers of trials were performed by using psychometric functions based on a model of two types of noise: stimulus-related noise (affecting slope) and extraneous noise (affecting upper asymptote). Threshold estimates were biased and imprecise when extraneous noise was high, as were the estimates of extraneous noise. Strategies were developed for rejecting data sets as too noisy for unbiased and precise threshold estimation; these strategies were most successful when extraneous noise was low for most of the data sets. An analysis of 1,026 data sets from visual function tests of infants and toddlers showed that extraneous noise is often considerable, that experimental paradigms can be developed that minimize extraneous noise, and that data analysis that does not consider the effects of extraneous noise may underestimate test-retest reliability and overestimate interocular differences.

Attention↗

PubMed1992

Retinal development in very-low-birth-weight infants fed diets differing in omega-3 fatty acids.

Full-field electroretinograms (ERGs) were obtained from very-low-birth-weight (VLBW) neonates to determine whether omega-3 (omega-3) fatty acids are essential for normal human retinal development. Eighty-one infants born at 30.4 (standard deviation, +/- 1.5) wk gestation were, within 10 d of birth, either enrolled to receive mother's milk (naturally containing both omega-6 and omega-3 essential fatty acids) or randomized to receive one of the infant formulas. Corn oil-based Formula A contained mainly linoleic acid (18:2 omega-6) and was low in all omega-3 fatty acids. Soy oil-based Formula B contained ample alpha-linolenic acid (18:3 omega-3) but no long-chain omega-3. Formula C, supplemented with both alpha-linolenic acid and marine oils, was comparable to human milk in long-chain omega-3. Full-field ERGs were obtained in the special care nursery from infants aged 36 and 57 wk postconception. Ten healthy preterm infants born at 35 wk gestation were tested at 36 wk postconception. Significant differences were found among groups in rod ERG function. Post hoc comparisons showed that infants fed Formula A had significantly higher rod thresholds than infants receiving long-chain omega-3 (human milk, Formula C, and intrauterine). Infants receiving Formula B had intermediate thresholds that were significantly higher than those of infants receiving intrauterine nutrition. Analysis of the leading edge of the a-wave showed that b-wave differences originated at the photoreceptor level. Differences were not present in infants at 57 wk postconception. No significant differences among groups were found in cone b-waves at 36 or 57 wk postconception. Oscillatory potentials had significantly longer implicit times at 57 wk postconception in infants fed Formula A than in infants receiving human milk. These findings suggest that retinal function varies with the dietary supply of omega-3 fatty acids in VLBW infants.

Breast Feeding↗

PubMed1992

Dietary essential fatty acid supply and visual acuity development.

The influence of dietary omega-3 fatty acid supply on visual acuity development was evaluated in very low birth weight (VLBW) infants using visual-evoked potential (VEP) and forced-choice preferential-looking (FPL) procedures at 36 and 57 wk postconception. The VLBW infants born at 27-33 wk postconception were randomized to one of three diet groups: corn oil, which provided solely linoleic acid; soy oil, which provided linoleic and alpha-linolenic acids; or soy/marine oil; which was similar to the soy oil formula but also provided preformed long chain omega-3 fatty acids. The VLBW infants in the soy/marine oil group had higher omega-3 levels in erythrocyte membranes and better VEP and FPL acuities at 36 and 57 wk than infants in the corn oil group. The soy oil group had intermediate omega-3 levels in erythrocyte membranes and significantly poorer VEP acuity at 57 wk compared with the soy/marine oil group. Only the soy/marine oil group had acuities comparable to the "gold standards" of VLBW infants fed human milk and preterm infants who were born and tested at 35-36 wk postconception. In addition, VEP and FPL acuity were poorer in a nonrandomized group of formula-fed full-term infants than in breast-fed full-term infants. The results suggest that dietary omega-3 fatty acid supply may play an important role in early human visual development.

Breast Feeding↗

PubMed1992

Office probing of congenital nasolacrimal duct obstruction.

We report the results of office nasolacrimal duct probing under topical anesthesia in 2369 eyes with symptomatic nasolacrimal duct obstruction. The overall success rate for cure by initial probing was 92%. In patients less than 9 months old, a 94% cure rate was achieved with one probing; in patients 9 months and older, the rate decreased to 84%. The decrease in success rate after 9 months was statistically significant (P less than .00001 by chi-square analysis). A majority of 180 parents of these patients surveyed said they were happy with the office procedure and preferred having the probing performed to resolve symptoms, even though they realized that the symptoms most probably would resolve by 1 year of age without it. We conclude that office probing for congenital nasolacrimal duct obstruction is a safe and effective method for treatment of symptomatic nasolacrimal duct obstruction, allowing the cost and risk of general anesthesia as well as the cost and inconvenience of prolonged medical management to be avoided.

Age Factors↗

PubMed1991

Forced-choice preferential looking acuity of children with cortical visual impairment.

Forced-choice preferential-looking acuity estimates from cortically visually impaired (CVI) infants and children were compared with three measures of visual function. Mean acuity deficit varied with fixation, tracking and visual impairment. Acuity deficit correlated with centile score for sensorimotor skills, but not for gross motor skills. The results suggest that these estimates provide information about the CVI child's ability to use vision in everyday life. Correlations were found between initial acuity deficits and acuity deficits measured from three months to six years later. Forced-choice preferential-looking acuity estimates may be useful for evaluating treatment response and establishing guidelines for educational materials for these infants and children.

Blindness↗

PubMed1991

Visual outcome in infants with cicatricial retinopathy of prematurity.

Monocular grating acuities of preterm infants with retinopathy of prematurity (ROP) were measured using a forced-choice preferential-looking (FPL) procedure. Eyes were independently graded by a retinal specialist and/or pediatric ophthalmologist and assigned to anatomic outcome categories on the basis of cicatricial residua of ROP. Eyes assigned to the normal/regressed and peripheral retinal changes categories (n = 120) had normal posterior poles. The authors found that grating acuities in this group were slightly lower than those of age-matched healthy full-term infants, even when infants with amblyogenic or neurologic conditions were eliminated from the analysis. Grating acuity of eyes assigned to the macular ectopia, macular fold, partial detachment, or total detachment outcome categories (n = 60) had abnormal posterior poles, and grating acuity of these eyes was significantly related to anatomic outcome category (P less than 0.001). Follow-up data from subsets of eyes at 6 months, 12 months, or 2-5 yr after the initial acuity test suggest that early FPL acuity tests may be predictive of long-term functional outcome (r = 0.75-0.87).

Follow-Up Studies↗

PubMed1990

Infant spatiotemporal vision: dependence of spatial contrast sensitivity on temporal frequency.

Effects of temporal frequency on infant spatial contrast sensitivity were studied with forced-choice preferential looking, using localized 1.0 and 0.35 c/deg grating patches. Between 4 and 8 months, contrast sensitivity at 1.0 c/deg increased significantly at 8-17 Hz but showed little change at 2-4 Hz, so temporal tuning became increasingly bandpass with age. At 4 months, temporal tuning was lowpass at 1.0 c/deg and bandpass at 0.35 c/deg. Control data on adults indicate that the differences between the infant and adult data cannot be accounted for solely by reduced photoreceptor density and quantal catch, and suggest developmental changes in tuning and/or relative sensitivities of spatiotemporal mechanisms.

Adult↗

PubMed1990

Effect of dietary omega-3 fatty acids on retinal function of very-low-birth-weight neonates.

Retinal function was assessed by electroretinogram in 32 neonates randomly assigned to formulas of different omega-3 fatty acid content and in 10 infants fed human milk. All neonates had a birth weight of 1000-1500 g and were fed study diets from d 10 to 45 or discharge. Group A received formula containing predominantly 18:2 omega-6. Group B received a balanced mix of 18:2 omega-6 and 18:3 omega-3. Group C was given a formula containing both essential fatty acids and supplemented with marine oil to provide 22:6 omega-3 content similar to that of human milk. The fatty acid composition of plasma and red blood cell (RBC) lipids were similar for all groups on entry but marked diet-induced differences were found after feeding the study diets. Group C was comparable to the human milk-fed group, but group A had lower 22:6 omega-3 and omega-3 long-chain polyunsaturated fatty acids (LCPUFA) in plasma and RBC membranes. Cone function was not affected by dietary essential fatty acids. Rod electroretinogram thresholds were significantly higher for group A relative to the human milk-fed group and group C and significantly correlated with RBC omega-3 LCPUFA (r = -0.63, p less than 0.0001); 44% of the variance could be explained by RBC and plasma omega-3 LCPUFA content.(ABSTRACT TRUNCATED AT 250 WORDS)

Double-Blind Method↗

PubMed1990

Amblyopia and the pediatrician.

Amblyopia is one of the most common and significant eye ailments in children. It is classified into organic and functional; functional is further divided into classifications of deprivation, strabismic, and refractive. Early diagnosis and treatment are of paramount importance. Diagnostic techniques are age-related. Treatment consists of eliminating associated defects, properly focusing the image on the retina (glasses or contact lens), and patching the good eye to force the child to use the amblyopic eye. Treatment may only be effective within the first 2 or 3 months of life for some conditions and later in childhood for other conditions. Amblyopia can recur up to age 9. The pediatrician has the heavy responsibility of recognizing amblyopia at an early enough age to allow for effective treatment. Nationwide there are many pediatric ophthalmologists available to institute this early, effective treatment. With this teamwork, we can help eliminate the most common cause of visual impairment in the pediatric patient.

Aging↗

PubMed1990

Prospective assessment of acuity and stereopsis in amblyopic infantile esotropes following early surgery.

Sensory and motor status were evaluated prospectively in a group of 84 infantile esotropes with fixation preference. Treatment consisted of part-time occlusion therapy, spectacles for bilateral hyperopia of 3.0 diopters or more and bimedial rectus recession. Successful occlusion therapy was associated with both a decrease in fixation preference and a "trade-off" in grating acuities of preferred and nonpreferred eyes. Three patients responded to occlusion therapy and spectacles alone; the remaining patients were treated surgically before their first birthday. Adequate alignment was achieved in over 75% of patients. During a mean follow-up of 28 months, 31 patients required further surgery to maintain horizontal and/or vertical alignment. Following occlusion therapy and surgery, acuity development proceeded normally. Postoperatively, approximately 35% of patients had at least gross stereopsis with random dot stereograms.

Amblyopia↗

PubMed1979

Monocular light exclusion for a period of days reduces directional sensitivity of the human retina.

Single eyes of young adult observers were occluded for as long as 10 days. Directional sensitivity of the retina (the Stiles-Crawford effect of the first kind) under photopic conditions was dramatically reduced at every retinal location tested in all subjects. The maximum effect was observed within 3 to 5 days, and recovery took place at approximately the same rate after termination of patching.

Humans↗

PubMed1979

The effects of duration and luminance on binocular depth mixture.

Two stimuli in the same binocular direction, one in front and the other an equal disparity behind a fixation point, are perceived at one depth. This depth is between that corresponding to the two stimulus disparities and varies continuously from one stimulus to the other as a function of the ratio of their luminances. When either duration or absolute luminance is increased, perceived depth changes toward the midpoint of the two disparities.

Adult↗

PubMed1979

Effect of uniocular occlusion on selected visual functions.

Uniocular occlusion (dark patching) of adults for a period of days produces marked reduction in the directional sensitivity of the eye (Stiles-Crawford effect). The effect reaches a maximum 3 to 5 days after the onset of patching. Recovery occurs in a comparable period. The second eye is not affected, and a simple light diffuser fails to produce the same effect. Coupled with alteration in directional sensitivity are an overall increase in sensitivity and modest resolution and perceived colour changes. These findings, with other research, suggest that directional sensitivity is at least partially mediated by light and that orientation of photoreceptors is an active process.

Adult↗

PubMedDate not supplied

VEP acuity, FPL acuity, and visual behavior of visually impaired children.

Forced-choice preferential-looking (FPL) and pattern-visual-evoked potential (VEP) acuity tests were conducted with 42 children with bilateral moderate to severe visual impairment (age, 4 months to 9 years). Within this group of children, FPL acuity testing was more successful than VEP acuity testing (98% versus 64%). Mean FPL acuity was better than mean VEP acuity (20/155 vs 20/290, P less than .002). For the children who completed both FPL and VEP acuity tests, an acuity difference score (FPL minus VEP) was derived, and compared to difference scores based on normative data. Significant differences were found between visually impaired (VI) and control difference scores (P less than .001). Difference scores of VI were larger than and opposite in sign to the control scores. Rating scores of visual behaviors supported the concurrent validity of the FPL acuities (P = .01), but not the VEP acuities.

Child↗