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[Reflex therapy, massage, and manual therapy in the treatment of progressive myopia in children and adolescents].

The paper describes the methods and results of multimodality treatment for progressive myopia in children and adolescents, by applying acupuncture, massage, and manual therapy. Thirty-three patients aged 7 to 17 years who had progressive myopia of 0.5 to 10.8 diopters were treated by an original procedure as repeated courses. Their follow-up lasted 2 years. A beneficial therapeutic effect as increases in uncorrected and subcorrected visual acuity, ocular accommodation reserves, and myopia regression rates was observed in 64% of the patients. Two-year myopia stabilization was achieved in 45% of cases. There were neither complications nor side effects. The possible mechanism of the remedial effect of the procedure is discussed in the paper.

Accommodation, Ocular↗
PubMed1983

The effect of phenylephrine hydrochloride on the resting point of accommodation.

Previous models for ocular accommodation have suggested a dual sympathetic/parasympathetic innervation to the ciliary muscle. Such models would predict that sympathomimetic drugs should change the resting point or dark focus of accommodation. The effect of an alpha-adrenergic agonist (10% phenylephrine hydrochloride) on accommodation was examined; the results show a decrease in the near point of accommodation, without a change in the resting point of accommodation. These results suggest that the accommodative state of the eye is not the result of a simple balance between sympathetic and parasympathetic innervation as proposed by previous models of accommodation.

Accommodation, Ocular↗
PubMed2002

Changes of ocular aberration with accommodation.

PURPOSE: To study the effect of accommodation on ocular aberrations. DESIGN: Observational case series. METHODS: The ocular aberrations in 33 eyes of 33 young adults were measured with a Hartmann-Shack wavefront aberrometer before and during 3 diopters of accommodation. RESULTS: The root mean square values of wavefront error did not change for a 4-mm and a 6-mm zone; however, spherical aberration changed significantly toward negativity for both the 4-mm zone (P <.001) and 6-mm zone (P =.022). CONCLUSIONS: During accommodation, the significant change in spherical aberration occurs without a change of image quality. Therefore, for customized aberration, it may not be advantageous to eliminate the physiologic spherical aberration for far vision.

Accommodation, Ocular↗
PubMed1992

Steady-state accommodation and ocular biometry in late-onset myopia.

The steady-state accommodative responses of emmetropes and late-onset myopes was measured for an array of numbers located at -1, -3 and -5 dioptres using an objective infra-red optometer. Responses were compared for passive (reading numbers) and active (adding numbers) conditions. For the passive condition, the late-onset myopes showed a significantly lower accommodative response than the emmetropic group. No significant differences were found between the two groups for the active condition. Ocular biometric characteristics were also measured in emmetropes, late-onset myopes and early-onset myopes using keratometry and ultrasonography. No significant differences in corneal curvature, anterior chamber depth and crystalline lens thickness were found between the groups. Late-onset myopes exhibited significantly deeper vitreous chambers than emmetropes, which more than accounted for the difference in refractive error between the two refractive groups. We conclude that, while significant differences exist in the accommodative responses of late-onset myopes and emmetropes, late-onset myopia is due predominantly to elongation of the vitreous chamber.

Accommodation, Ocular↗
PubMed2000

An area for vergence eye movement in primate frontal cortex.

To view objects at different distances, humans rely on vergence eye movements to appropriately converge or diverge the eyes and on ocular accommodation to focus the object. Despite the importance of these coordinated eye movements (the 'near response') very little is known about the role of the cerebral cortex in their control. As near-response neurons exist within the nucleus reticularis tegmenti pontis, which receives input from the frontal eye field region of frontal cortex, and this cortical region is known to be involved in saccadic and smooth-pursuit eye movements, we propose that a nearby region might play a role in vergence and ocular accommodation. Here we provide evidence from rhesus monkeys that a region of frontal cortex located immediately anterior to the saccade-related frontal eye field region is involved in vergence and ocular accommodation, and in the sensorimotor transformations required for these eye movements. We conclude that the macaque frontal cortex is involved in the control of all voluntary eye movements, and suggest that the definition of the frontal eye fields should be expanded to include this region.

Accommodation, Ocular↗
PubMed2002

Effect of beta-adrenoceptor antagonists on autonomic control of ciliary smooth muscle.

PURPOSE: Pharmacological intervention with peripheral sympathetic transmission at ciliary smooth muscle neuro-receptor junctions has been used against a background of controlled parasympathetic activity to investigate the characteristics of autonomic control of ocular accommodation. METHODS: A continuously recording infra-red optometer was used to measure accommodation on a group of five visually normal emmetropic subjects under open- and closed-loop conditions. A double-blind protocol between saline, timolol and betaxolol was used to differentiate between the localised action on ciliary smooth muscle and effects induced by changes in stimulus conditions. Data were collected before and 45 min following the instillation of saline, timolol or betaxolol. Open-loop post-task decay was investigated following 3 min sustained near fixation of a stimulus placed 3 D above the subject's pre-task tonic accommodation level. Closed-loop dynamic responses were recorded for each treatment condition while subjects viewed sinusoidally (0.05-0.6 Hz) or stepwise vergence-modulated targets over a 2 D range (2-4 D). RESULTS: Open-loop data demonstrate a rapid post-task regression to pre-task tonic accommodation levels for saline and betaxolol control conditions. A slow positive post-task shift was induced by timolol indicating that sympathetic inhibition contributes to accommodative adaptation during sustained near vision. Closed-loop accommodation responses to temporally modulated sinusoidal stimuli showed characteristic features for both saline and betaxolol control conditions. Timolol induced a reduced gain for low- and mid-temporal frequencies (< 0.3 Hz) but did not affect the response at higher temporal frequencies. Response times to stepwise stimuli increased following the instillation of timolol for the near-to-far fixation condition compared with the controls and was related to the period of sustained prior fixation. CONCLUSIONS: Modulation of accommodation under open- and closed-loop conditions by a non-selective beta-blocker is consistent with the temporal and inhibitory features of sympathetic innervation to ciliary smooth muscle. Although parasympathetic innervation predominates there is evidence to support a role for sympathetic innervation in the control of ocular accommodation.

Accommodation, Ocular↗
PubMed1996

The role of cerebro-ponto-cerebellar pathways in the control of vergence eye movements.

Single-unit recording and anatomical techniques have been used in Rhesus monkeys to investigate the central pathways involved in the neural control of vergence and ocular accommodation. Anatomical studies have revealed connections between the midbrain near-response region and the posterior interposed (IP) and fastigial nuclei of the cerebellum. Single-unit recording studies in the IP of alert, trained monkeys identified cells with activity that increased with increases in the amplitude of divergence and far accommodation, i.e. the far-response. Microstimulation at the site of these neurons often produced a far-response. Single-unit recording from a precerebellar nucleus, the nucleus reticularis tegmenti pontis (NRTP), identified some cells with activity that linearly increased with increases in the amplitude of the near-response, and some with activity that linearly increased with increases in the amplitude of the far-response. Microstimulation at the site of these near- or far-response neurons often produced changes in vergence angle and accommodation. Single-unit recording studies in the region of the frontal eye fields identified cells in the prearcuate cortex with activity that is modulated by either the near- or far-response. These results suggest that regions of the prearcuate cortex, the NRTP and the IP form part of a cerebro-ponto-cerebellar pathway modulating or controlling vergence and ocular accommodation.

Accommodation, Ocular↗
PubMed2002

Neural mechanisms for the control of vergence eye movements.

Our recent studies in non-human primates have identified and characterized cerebro-ponto-cerebellar pathways involved in the control of vergence eye movements. Specifically, within the deep cerebellar nuclei and nucleus reticularis tegmenti pontis, we have identified neurons that are related to either the near response (convergence and increased ocular accommodation) or the far response (divergence and decreased ocular accommodation). In addition, within the prearcuate region (area 8a), we have characterized neurons related not only to either the far response or the near response, but also to the sensorimotor transformations underlying these eye movements. Because the vergence-related prearcuate region abuts the frontal eye fields, we suggest that the extent of the frontal eye fields be expanded to include this region. We further suggest that with inclusion of this vergence-related region, the frontal eye fields are important for all voluntary eye movements.

Animals↗
PubMed1987

Presbyopia: an animal model and experimental approaches for the study of the mechanism of accommodation and ocular ageing.

During the last hundred years, observations on normal and a few aniridic human eyes, together with population studies on the age-dependent decline in accommodative amplitude, resulted in the formulation of theories of human accommodation, and led to the concept that presbyopia is an inevitable consequence of ageing. However, such studies failed to substantiate these theories and concepts or to reveal the fundamental mechanisms of accommodation and its age-dependent loss. Detailed understanding of these mechanisms and the environmental, dietary, and behavioural factors that may influence the development of presbyopia will require controlled studies and, in some cases, invasive experimental manipulations that can only be achieved through the use of an animal model. This paper reviews some of the evidence indicating that the rhesus monkey is a highly suitable primary animal model for such studies, as well as for studies on other aspects of ocular ageing, and reviews some of the techniques and experimental approaches that have already been adapted or developed for such studies.

Accommodation, Ocular↗
PubMed1993

A biometric study of ocular changes during accommodation.

We performed a biometric study that used A-mode ultrasonography on 106 subjects during ocular accommodation. The subjects were divided into two groups; group 1 included 76 subjects and group 2 included 30 subjects. In group 1, we measured the anterior chamber depth, lens thickness, and axial length in the right eye while the left eye, wearing corrective spectacles, focused at distances of 6 m, 33 cm, and 33 cm with an additional correction of +3.0 diopters to offset any accommodative effect. In group 2, we measured the anterior chamber depth, lens thickness, and axial length in the right eye while the left eye focused at distances of 6 m, 33 cm, and 12.5 cm. Similar to the left eyes in group 1, the left eyes in group 2 wore corrective spectacles during all procedures. During accommodation, decreased anterior chamber depth and thickening of the lens were noted in all cases. In group 1, axial length significantly increased an average of 0.06 +/- 0.01 mm (P < .0005) while the left eye focused at a distance of 33 cm. There were no significant changes with the additional +3.0 diopters (P < .05). In group 2, axial length significantly increased an average of 0.05 +/- 0.01 mm (P < .0005) when the left eye focused at a distance of 33 cm, and there was further significant elongation of 0.05 +/- 0.01 mm when the left eye focused at a distance of 12.5 cm. Collectively, these results suggest that axial length increases along with changes in the lens and anterior chamber depth during ocular accommodation.

Accommodation, Ocular↗
PubMed1977

Deep ocular socket reconstruction.

A technique to reconstruct totally contracted sockets forms spacious, deep ocular fornices to accommodate ocular prostheses. Fixation of the midperiphery of mucous-membrane-lined, custommade conformers to the superior and inferior orbital rims secures the posterior periphery of the conformer deep in the orbit. The method restores the normal anatomy of the ocular fornices that not only extends to the orbital rims but also penetrates deeply into the orbit along its roof and floor. The procedure contrasts with conventional, frequently unsuccessful methods of socket reconstruction that form fornices only to the superior and inferior orbital rims without extending posteriorly into the orbit. Using this technique, we reconstructed deep, spacious sockets in five patients with serious socket contracture, allowing the patients to retain cosmetically acceptable artificial eyes. The principles advocated apply to all contracted sockets.

Adolescent↗
PubMed1990

Refractive state, ocular anatomy, and accommodative range of the sea otter (Enhydra lutris).

Sea otters are carnivorous, amphibious mammals that are active both above and under water. Accordingly, it might be expected that their eyes are adapted for both aerial and aqueous vision. We examined the anatomy and physiological optics of the sea otter eye with a view towards describing and explaining its amphibious visual characteristics. We employed photokeratoscopy to measure the refractive power of the sea otter cornea, which we found to be 59 D. Using video dynamic photorefraction, we found that sea otters can focus targets clearly both in air and water, relying on accommodation to compensate for the refractive loss of their corneas upon immersion in water. Our anatomical investigations revealed that the anterior epithelium of the cornea is extensively developed, as is the iris musculature, meridional ciliary muscle, and the corneoscleral venous plexus. The first feature is most likely an adaptation to the salinity of the marine environment. We believe the latter features are part of a novel, well-developed lenticular accommodative mechanism.

Accommodation, Ocular↗
PubMed1999

Does over-accomodation occur when using aircraft head-up displays?

BACKGROUND: Whether over-accommodation is caused by the use of head-up displays is still under debate. Most prior experimentation has involved cognitively demanding tasks, which are known to affect the accommodation response. The simulations have often been unrealistic and involved short working distances. HYPOTHESIS: Over-accommodation is caused not by the presence of a head-up display per se, but rather by the cognitive demand of the task. METHODS: The effect of increasing the task cognitive load and the use of forward looking infra-red imagery (FLIR) on the ocular accommodative response and task performance was assessed with a realistic head-up display assisted flying task. FLIR increases cognitive load due to its poor resolution and the need for interpretation of the images. RESULTS: Over-accommodation was found to be small in magnitude (0.17+/-0.03D; range -0.02-0.45D) occurring only with cognitively demanding tasks and with forward looking infrared imagery. Response times to detect tanks in the outside world scene were slower with increased cognitive load and forward looking infra-red imagery, along with a reduced detection rate, decreased accuracy of tracking tanks in the outside world and poorer control of the head-up display pitch ladder. When discrimination was added to detection in an outside world task, decisions were delayed until they could be accurately made, rather than performance degraded. CONCLUSION: The use of a virtual head-up display in a simulated aircraft environment did not adversely affect ocular accommodation. However, increased cognitive demand or FLIR imagery caused significant inward shifts of accommodation.

Accommodation, Ocular↗
PubMed1979

The Mandelbaum effect: evidence for an accommodative bias toward intermediate viewing distances.

Previous research has shown that ocular accommodation tends to correspond to an intermediate distance, the dark focus, in the absence of effective stimulation. The present experiments measured accommodative responses in the presence of two adequate, monocular stimuli superimposed optically at different distances. In Experiment I, observers attempted to maintain a matrix of letters in clear focus as a superimposed mesh screen was varied in distance. In experiment II, observers were instructed to focus the "easier" of two similar grating patterns that were presented over a range of distances with a constant separation of two diopters. The results of both experiments showed an accomodative response bias toward target distances near the observers' dark focus of accommodation. The implications of these findings for the theoretical resting state of accomodation and for practical problems of visual performance are discussed.

Accommodation, Ocular↗
PubMed1998

Neurons in the posterior interposed nucleus of the cerebellum related to vergence and accommodation. I. Steady-state characteristics.

The present study used single-unit recording and electrical microstimulation techniques in alert, trained rhesus monkeys to examine the involvement of the posterior interposed nucleus (IP) of the cerebellum in vergence and accommodative eye movements. Neurons related to vergence and ocular accommodation were encountered within a circumscribed region of the IP and their activity during changes in viewing distance was characterized. The activity of these neurons increased with decreases in vergence angle and accommodation (the far-response) but none showed changes in activity during changes in conjugate eye position and we therefore term them "far-response neurons." Far-response neurons were found within a restricted region of the IP that extended approximately 1 mm rostrocaudally and mediolaterally and 2 mm dorsal to the fourth ventricle. Microstimulation of this far-response region of the IP with low currents (<30 microA) often elicited divergence and accommodation for far. The behavior of 37 IP far-response neurons was examined during normal binocular viewing, during monocular viewing (blur cue alone), and during binocular viewing with accommodation open-loop (disparity cue alone). The activity of all cells was modulated under all three conditions. However, the change in activity of some of these neurons was significantly different under these three viewing conditions. The behavior of 70 IP far-response neurons was compared during normal binocular viewing and during viewing in which the accommodative response was significantly dissociated from the vergence response. The data from these two conditions was pooled and multiple regression analyses for each neuron generated two coefficients expressing the activity of the neuron relative to the vergence and to accommodative response respectively. On the basis of these coefficients, the overall activity of the neurons were classified as follows: 34 positively correlated with divergence, 11 positively correlated with far accommodation, 14 positively correlated with divergence and far accommodation, 9 positively correlated with divergence and accommodation, and 2 positively correlated with convergence and far accommodation. The results of this study demonstrate the involvement of a specific region of the posterior interposed nucleus of the cerebellum in vergence and accommodation. IP far-response neurons are active for vergence and accommodation irrespective of whether or not these eye movements are elicited by blur or disparity cues. The data in the present study strongly suggest that this cerebellar region is a far-response region that is involved in vergence as well as accommodative eye movements.

Accommodation, Ocular↗
PubMed2002

Are there age differences in the accommodative response curve between 3 and 14 years of age?

The monocular ocular accommodative responses of 118 emmetropic children, aged from 3 to 14 years, were measured at five different stimulus distances (0, 1, 2, 3, 4 D) from the principal plane of the eye with a Canon Autoref R-1. The change in the accommodative response curve in emmetropic children between 3 and 14 years old was found to be negligible.

Accommodation, Ocular↗