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Biomedical subjects

V Dobson

Publications and source records attributed to V Dobson.

14 recordsLinked to original sources
PubMed1992

The correlation of visual function with posterior retinal structure in severe retinopathy of prematurity. Cryotherapy for Retinopathy of Prematurity Cooperative Group.

The Multicenter Trial of Cryotherapy for Retinopathy of Prematurity previously reported reduced incidence of both poor structural and functional outcomes after cryotherapy. We compared the results in 304 eyes of patients in the randomized portion of the trial in whom both structural and functional assessments were performed 12 months after randomization. Two hundred fifty-five eyes (83.9%) had concordant outcomes: 153 eyes had favorable structural and functional outcomes and 102 eyes had unfavorable structural and functional outcomes. Twenty-nine eyes (9.5%) had discordant outcomes: 20 eyes had favorable structural and unfavorable functional outcomes and nine eyes had unfavorable structural and favorable functional outcomes. The small number of discordant outcomes could generally be accounted for by three factors: (1) retinal abnormalities beyond those considered in the photographic grading system (12 eyes), (2) nonretinal visual pathway disease (five eyes), or (3) false-positive and false-negative results in the measurement systems used to evaluate structure and function (five eyes). In 20 eyes (6.6%), photographs could not be graded or the visual acuity was untestable. We conclude that the appearance of the posterior pole of the eye correlates well with grating acuity in the 12-month-old infant with a history of severe retinopathy of prematurity.

Cryosurgery↗
PubMed1992

Development of myopia in infants with birth weights less than 1251 grams. The Cryotherapy for Retinopathy of Prematurity Cooperative Group.

The authors report on the incidence of myopia in a large group of premature infants with birth weights of less than 1251 g followed as part of the multicenter study of Cryotherapy for Retinopathy of Prematurity. None of the eyes reported here underwent cryotherapy. Eyes were refracted using cycloplegic retinoscopy at 3 months (n = 2916), 12 months (n = 2626), and 24 months (n = 961 at 5 of the 23 centers) after term. Myopia was observed in approximately 20% of the children at each test age. The percentage of high myopia (greater than or equal to 5 diopters) doubled from 2% to 4.6% between 3 and 12 months and remained stable thereafter. Lower birth weight and increasing severity of retinopathy of prematurity (ROP) were strong predictors of myopia and high myopia. In addition, anisometropia, astigmatism, and the presence of posterior pole residua from ROP also were associated with a higher incidence of myopia and high myopia.

Anisometropia↗
PubMed1992

Grating acuity and visual field development of infants with bronchopulmonary dysplasia.

The grating acuity and visual fields were assessed of 48 infants with bronchopulmonary dysplasia (BPD) who had no periventricular leukomalacia or grade III or IV intraventricular hemorrhage, and no stage 3 or greater retinopathy of prematurity. Infants were tested at four, eight, 11, 17 and 24 months corrected age, and their results were compared with those of 81 healthy preterm infants and 54 with hyaline membrane disease (HMD) that did not result in BPD. The BPD group showed no significant difference in acuity development compared with the healthy preterm and HMD groups. Infants with BPD had significantly smaller visual fields than either control group at 11 months; visual field development was similar for all groups at all other test ages. The authors conclude that infants with BPD who have no significant ocular or neurological complications show normal grating acuity and visual field development during the first two years of life.

Bronchopulmonary Dysplasia↗
PubMed1992

Preferential looking--clinical lessons.

Preferential looking-based tests of acuity have been available for over a decade. The authors discuss their use in clinical practice, particularly in three groups in whom acuity could not be quantified by traditional means: normal infants, and young children who are either mentally retarded, or who have visual disorders. Preferential looking (PL) testing has increased our understanding of the natural history of visual pathway disorders and has revealed certain patterns of acuity development. Early acuity development may be normal, delayed, or stationary, while in later infancy and childhood the following abnormal patterns have been identified: asymptotic, parallel, catch-up, or regressing. While this information has introduced a degree of complexity hitherto unknown which, if misunderstood, can lead to test misinterpretation, it offers the clinician invaluable information to improve patient care, and may also offer clues to the fundamental mechanisms of visual development.

Child, Preschool↗
PubMed1979

Infant vision testing by a behavioral method.

A behavioral method of screening binocular infant vision called forced choice preferential looking (FPL) has been developed. Clinical trials of the FPL test for young infants are reported here. The test aids nonspecialized personnel in early identification of bilateral ocular abnormalities and anomalies of binocular cooperation (strabismus). It is not possible to screen for monocular eye disease or amblyopia with this test. Modifications of the FPL test may offer new ways of assessing other aspects of visual function early in life.

Age Factors↗
PubMed1978

A behavioral method for efficient screening of visual acuity in young infants. I. Preliminary laboratory development.

A technique for rapid behavioral screening of grating acuity in infants 1 to 4 months of age is described. The approach, called forced-choice preferential looking (FPL), depends upon the fact that normal infants will stare fixedly at acuity gratings with stripe widths above a rather abrupt cutoff width. The present task is to find the minimum stripe width, termed the diagnostic stripe width, to which infants with normal visual acuity will readily respond. The expectation is that infants with below-normal acuity will not be able to respond to diagnostic stripes so defined. To assess the feasibility of such a test procedure and define preliminary diagnostic stripe widths for infants 4, 8, 12, and 16 weeks of age, 76 presumptively normal infants were tested in the laboratory with a 40-trial FPL procedure. Sixty-nine infants (91%) completed the test procedure. For each age group, a preliminary estimate of the diagnostic stripe width was found. The group performance was uniformly high for the stripe widths designated as diagnostic and fell off sharply for finer stripes, confirming the feasibility of the approach.

Age Factors↗
PubMed1978

A behavioral method for efficient screening of visual acuity in young infants. II. Clinical application.

Visual performance in 130 infants was assessed in a clinical setting with the forced-choice preferential looking (FPL) method described by Dobson et al.5 Over 90% of infants completed testing. Testing usually required less than 10 min. One group of infants tested also underwent complete ophthalmic examination. The second, larger group was screened with handlight examinations and FPL testing; any abnormalities detected were evaluated by full ophthalmic examination. Results so far indicate that the FPL test accurately identifies babies with binocular visual problems and that, when coupled with a handlight examination, it provides efficient screening for ocular problems in infants 0 through 16 weeks of age (postterm).

Age Factors↗
PubMed1976

Pattern reversal visually evoked potentials in infants.

Visually evoked potentials (VEP) were recorded from infants two to six months of age using a checkerboard pattern reversal stimulus. By six months, infants produced the largest amplitude VEP to checks subtending visual angles of 7.5 or 15 minutes of arc, as do adults with 20/20 acuity. This finding indicates that by six months an infant's sensory capacity for a visual acuity of 20/20 is established.

Adult↗
PubMed1975

Long-term effect of phototherapy on visual function.

Computer-averaged electroretinogram records were used to examine scotopic retinal functioning of a group of 4-year-old children who were treated for neonatal hyperbilirubinemia by exposure to at least 42 consecutive hours of continuous phototherapy. Dark adaptation functions of the children were similar to those previously found for control subjects, suggesting that no permanent damage to rod function had been incurred during exposure. Statistical analysis showed no significant differences in the final electroretinographic amplitudes of light-treated and control subjects. Ophthalmologic and neurologic examinations were also negative.

Birth Weight↗
PubMed1975

Pattern learning and the control of behaviour by all-inhibitory neural network hierarchies.

An all-inhibitory network which learns by selective disconnection of synapses is described. This is similar to an 'associative net'; however, it is simpler in that its neurons do not need to perform arithmetical operations, and the net does not require additional threshold modulating neurons in order to cope with input patterns which are incomplete, or of differing sizes. This fundamental simplicity permits a greater variety and density of connections. These can multiply the capacity of the nets to learn complex sequences of patterns without being saturated. An "all-connected" net is described which has the holograph-like capacity to reconstruct the whole of an input pattern from part patterns without involving delays or threshold devices. All of these inhibitory nets can construct themselves by means of simple random growth processes, without incurring any loss of learning capacity of holographic properties. Similarly, synapses can be allowed to potentiate with use, so that reaction times are progressively reduced by practice, without any reduction in the quality of the performance. Inhibitory connections between arrays can give patterns in one array control over the allocation of channels in which lower arrays store learned information. A description is given of a model, decentralised, inhibitory hierarchy consisting of inter-connected arrays which can learn to execute goal-directed TOTE-type programs of behaviour by means of a simple 'putting-through' procedure.

Axons↗