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R G Boothe

Publications and source records attributed to R G Boothe.

51 records · Page 3Linked to original sources
PubMed1982

Meridional variations in acuity and CSF's in monkeys (Macaca nemestrina) reared with externally applied astigmatism.

Infant macaque monkeys have been raised under such conditions that all visual experience was obtained while looking through a cylindrical lens. When tested at older ages, these monkeys were found to have meridional differences in acuity and contrast sensitivity. The direction of the differences were predictable on the basis of the defocus produced by the rearing condition. The data support the theory, previously suggested on the basis of clinical and correlational studies, that astigmatism is a major cause factor in the occurrence of meridional amblyopia.

Accommodation, Ocular↗
PubMed1982

Anisometropic amblyopia in Macaca nemestrina monkeys produced by atropinization of one eye during development.

Two macaque monkeys were reared with daily administration of the cycloplegic drug, atropine, to one eye until 8 months after birth. Behavioral testing of contrast sensitivity functions in the atropinized eyes during the rearing period demonstrated that this rearing procedure caused the treated eyes to be chronically defocused. Measurement at the age of 6 or 8 months of contrast sensitivity while optically correcting the defocus demonstrated that an amblyopia had developed in the treated eyes. Furthermore, the relative magnitude of the amblyopia across spatial frequencies was similar to the relative magnitude of the defocus. Subsequently testing at 1 year of age demonstrated that the deficits persisted for several months after termination of the defocus rearing. This rearing procedure appears to provide a reasonable primate model with which to study anisometropic amblyopia in monkeys.

Age Factors↗
PubMed1981

Naturally occurring strabismus in monkeys (Macaca nemestrina).

Seven naturally strabismic monkeys (Macaca nemestrina) was identified. Five of these monkeys were examined by ophthalmologists. No ophthalmoscopically obvious cause for the squint was found in any case. Of those five animals, two were tested behaviorally on visual responsiveness and visual acuity. The acuity of both eyes of both monkeys was somewhat poorer than normal. In addition, an amblyopia of 0.8 octaves was found for one monkey and 0.6 octaves for the others. The existence of naturally strabismic monkeys supports the utility of the macaque as an animal model for studying strabismus and amblyopia.

Amblyopia↗
PubMed1980

Development of contrast sensitivity in infant Macaca nemestrina monkeys.

During an infant monkey's first 28 postnatal weeks, the visual contrast sensitivity function develops its characteristic adult form. Contrast sensitivity is depressed relative to that of the adult for all spatial frequencies during the early postnatal weeks. Absolute sensitivity to frequencies below 5 cycles per degree approaches adult levels by 20 weeks after birth, whereas sensitivity to fine spatial detail continues to develop through 28 weeks. The results imply that the development of primate spatial vision is more complex than just an improvement in the ability to resolve acuity gratings.

Animals↗
PubMed1980

The time course for the development of strabismic amblyopia in infant monkeys (Macaca nemestrina).

The time course for the development of acuity was followed in two experimentally esotropic infant monkeys (Macaca nemestrina). Surgical esotropia was produced at 6 days postnatal. Acuity values for both eyes of both infant monkeys were found to be normal through 4 weeks postoperative. After this period of delay, amblyopia began to emerge. The deviated eyes showed poorer acuity than the nondeviated eyes at every subsequent age tested. These data support a developmental hypothesis for the emergence of strabismic amblyopia.

Age Factors↗
PubMed1979

A quantitative investigation of spine and dendrite development of neurons in visual cortex (area 17) of Macaca nemestrina monkeys.

In a previous Golgi study (Lund et al., '77) which examined the development of the macaque monkey striate cortex (area 17) it was observed that the dendrites of neurons within the visual cortex show a marked increase in the number of spines on their surface during the first eight weeks of postnatal life. The qualitative observation was also made that all neurons then showed a marked decrease in spine numbers by the time the animal was adult. Since these spines are known to be sites of synaptic contact, changes in their numbers may reflect changes in synapse populations on these neurons. This study examines quantitatively spine frequency and total dendritic development of Golgi impregnated neurons in monkeys ranging in age from 145 days gestation to adult. Four cell types were studied: spiny stellate neurons from laminae IVCalpha and IVCbeta and pyramidal neurons with soma in either lamina IIIB or upper lamina VI. After consideration of possible sources of variation in spine numbers several conclusions are made: (1) Dendritic spine development appears to be a tightly controlled process both in terms of actual numbers of spines on a neuron at any one age and in the rate of change of spine frequency. (2) The neurons populations examined all show a gradual increase in spine numbers up to eight weeks of age. (3) At least two different trends are found in spine population maturation after the eight week point: (A)-the spine population may remain constant at the eight week level for same period of time or (B)-there may be a rapid decline in spine numbers following the eight week peak. (4) There is a suggestion that those neurons associated with direct input, or early stages in the relays, from the parvocellular geniculate laminae show trend B, while those associated with magnocellular input, or later order combined relays within the cortex, show trend A. (5) Different parts of a single pyramidal neuron dendrite may show either trend A or trend B, depending on the lamina location of the dendritic segment considered. (6) All neurons show spine population decreases between nine months of age and adult (5-7 years) suggesting continuing long term maturational changes.

Animals↗
PubMed1977

Development of neurons in the visual cortex (area 17) of the monkey (Macaca nemestrina): a Golgi study from fetal day 127 to postnatal maturity.

The morphological maturation of several varieties of neurons of cortical area 17 have been followed in Golgi Rapid preparations from Macaque monkeys ranging in age from fetal day 127 to maturity. A developmental sequence common to all varieties of neuron is described. Maturation occurs at the same rate at all cortical depths and appears to relate to the size of the neuron rather than to factors such as generation time, arrival at a final laminar position or cell type. The characteristic laminar patterns of cell type distribution and the specific axonal and dendritic arborisations seen in the adult are generated in the earliest stages of growth and do not occur as the result of elimination from a wider, less precise, distribution. During the period from birth to postnatal week 8 a marked increase in the numbers of dendritic spines is seen in all varieties of neuron including those which will be spine-free in the adult. Following this period an equally marked reduction in spine numbers occurs, initially rapid but continuing at a slower rate even nine months postnatally. Possible relationships between these postnatal dendritic spine changes and the extreme sensitivity of the system to visual input during the early postnatal weeks are discussed.

Animals↗
PubMedDate not supplied

Maturation of binocular luminance interaction in normal young and adult rhesus monkeys.

PURPOSE: Our aim was to answer three questions 1) Do adult rhesus monkeys have binocular luminance interactions (BLIs) similar to those found in adult humans? 2) Is BLI in very young rhesus monkeys functionally mature? 3) If not, how does it change with age? METHODS: We recorded visually evoked potentials (VEPs) in response to sinusoidally modulated uniform fields. The fields were presented dichoptically by varying the relative temporal phase between the two eyes. Monkeys varied in age from 5.6 weeks to 5.25 years. RESULTS: VEPs were Fourier analyzed and the relative second harmonic amplitudes were taken as the response measure. The second harmonic amplitudes in adult monkeys had an asymmetrical 'V-shaped' function as interocular phase difference (IPD) varied from 0 degrees to 180 degrees, as had been observed previously in adult humans [1]. The youngest monkeys exhibited a symmetrical pattern which became more asymmetrical at older ages and was adult like by about 19 weeks. Asymmetry magnitude and log age correlated 0.97 (p < 0.05) in the monkeys younger than 19 weeks. CONCLUSIONS: The adult rhesus data are consistent with a model derived from humans which involves two types binocular luminance processing. One combines monocular responses nonlinearly (MNL) and a second combines monocular responses linearly followed by a binocular nonlinearity (MLBNL). These two processes have been associated with the parvocellular (P-) and magnocellular (M-) streams. Within this framework, the data from the youngest monkeys indicate that BLI in the P-stream is relatively less mature at birth than that in the M-stream and develops reaching functional maturity on these measures by around 19 weeks.

Adult↗
PubMedDate not supplied

Optical and neural factors limiting acuity development: evidence obtained from a monkey model.

Infants have much poorer acuity than adults. Recent experiments with infant monkeys indicate that this poor acuity cannot be explained on the basis of optics (quality of the retinal image) or sampling frequency (inter-receptor spacing). On the other hand, the poor acuity is not just a reflection of immature cognitive or motor development. Rather, the development of adult acuity levels appears to depend on maturation of neural elements in the early stages of the visual system.

Adult↗
PubMedDate not supplied

Frequency of naturally occurring strabismus in monkeys.

A colony of Macaca nemestrina monkeys was screened for naturally occurring strabismus. Thirteen cases of naturally occurring strabismus were documented, 12 esotropes and one exotrope. The characteristics of the strabismus in these monkeys were similar to those of human clinical cases. Four of the affected monkeys showed interocular differences in grating acuity. We estimated the incidence of strabismus in the monkey colony to be 4%.

Animals↗
PubMedDate not supplied

Studies of strabismus and amblyopia in infant monkeys.

Longitudinal studies of grating acuity have been conducted with strabismic infant monkeys. Representative data from several different monkey models of strabismus are presented. Acuity in the fixating eyes of these monkeys developed to adult levels similarly to acuity development in normal infant monkeys. Acuity in the non-fixating eyes often lagged behind, and in some cases never reached normal levels, resulting in a permanent amblyopia.

Age Factors↗
PubMedDate not supplied

Multifocal versus monofocal correction of neonatal monocular aphakia.

We compared the efficacy of monofocal and multifocal intraocular lenses (IOLs) as a means of optically rehabilitating eyes with monocular congenital cataracts using a primate model. A congenital cataract was simulated in the right eye of 20 monkeys from birth to 2 weeks of age with an opalescent contact lens. A lensectomy was then performed and a monofocal IOL was implanted in 11 eyes and a multifocal IOL in 9 eyes. Any residual refractive error was then corrected with an extended-wear contact lens. The fellow eyes were then randomized to no treatment or 70% occlusion therapy. Grating acuity was assessed using forced-choice preferential looking with Teller acuity cards at regular intervals. At 32 weeks of age, the pseudophakic eyes were mildly amblyopic, but the grating acuities were not significantly different between the pseudophakic eyes with multifocal versus monofocal IOLs or between subjects who had received occlusion therapy versus no treatment of the fellow eye. We conclude that at least through 32 weeks of age, multifocal and monofocal IOLs are of similar efficacy and occlusion therapy may be less important to prevent amblyopia from developing in pseudophakic eyes compared to contact-lens corrected aphakic eyes.

Amblyopia↗
PubMedDate not supplied

Latent fixation nystagmus and nasotemporal asymmetries of motion visually evoked potentials in naturally strabismic primate.

PURPOSE: To determine whether macaque monkeys who had onset of natural, alternating esotropia in early infancy have the eye movement abnormalities and motion visually evoked potential (VEP) abnormalities observed in human infantile esotropes. METHODS: Recordings were obtained of horizontal pursuit eye movements and fixation nystagmus under conditions of monocular viewing. Motion VEPs in response to horizontal motion were recorded with the animals sedated to reduce the possibility of eye movement artifact. RESULTS: The strabismic monkeys had a naso-temporal asymmetry of horizontal pursuit favoring nasally directed motion when viewing with either eye. When fixating stationary targets, latent nystagmus was apparent; the eyes drifted conjugately and the slow phase of the nystagmus was always nasally directed with respect to the fixating eye. Motion VEPs were characterized by a strong horizontal asymmetry with the directional bias inverted approximately 180 deg in the two eyes. These eye movement and motion VEP asymmetries were not observed in a normal macaque. CONCLUSIONS: Macaque monkeys who have infantile esotropia possess asymmetries of horizontal pursuit and motion VEPs like those documented in strabismic humans. Macaques with infantile esotropia appear to be an appropriate animal model for study of neural mechanisms in strabismus.

Animals↗