Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “ACCOMMODATION, OCULAR”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 973 records · Page 54Linked to original sources
PubMed2005

Visual accommodation in vertebrates: mechanisms, physiological response and stimuli.

The mechanism and stimulation of the accommodative reflex in vertebrate eyes are reviewed. Except for lampreys, accommodation is brought about by intraocular muscles that mediate either a displacement or deformation of the lens, a change of the corneal radius of curvature or a combination of these mechanisms. Elasmobranchs have little accommodation and are emmetropic in water rather than hyperopic as commonly stated. Accommodation in teleosts and amphibians is well understood and achieved by lens displacement. The accommodative mechanism of amniotes is of considerable diversity and reflects different lifestyles rather than phylogenetical relationships. In all amniotes, the ciliary muscle never has a direct impact on the lens. It relaxes the tension applied to the lens by zonular fibers and/or ligaments. In birds and reptiles the ciliary muscle is usually split into two parts, of which the anterior portion changes the corneal radius of curvature. The deformation of the lens is generally achieved either by its own elasticity (humans, probably other mammals and sauropsids) or by the force of circular muscle fibers in the iris (reptiles, birds, aquatic mammals). In the second part of the paper, some of the current hypotheses about the accommodative stimulus are reviewed together with physiological response characteristics.

Accommodation, Ocular↗
PubMed2002

The effect of incipient presbyopia on the correspondence between accommodation and vergence.

PURPOSE: To investigate the accommodation-convergence relationship during the incipient phase of presbyopia. The study aimed to differentiate between the current theories of presbyopia and to explore the mechanisms by which the oculomotor system compensates for the change in the accommodation-convergence relationship contingent on a declining amplitude of accommodation. METHODS: Using a Canon R-1 open-view autorefractor and a haploscope device, measurements were made of the stimulus and response accommodative convergence/accommodation ratios and the convergence accommodation/convergence ratio of 28 subjects aged 35-45 years at the commencement of the study. Amplitude of accommodation was assessed using a push-down technique. The measurements were repeated at 4-monthly intervals over a 2-year period. RESULTS: The results showed that with the decline in the amplitude of accommodation there is an increase in the accommodative convergence response per unit of accommodative response and a decrease in the convergence accommodation response per unit of convergence. CONCLUSIONS: The results of this study fail to support the Hess-Gullstrand theory of presbyopia in that the ciliary muscle effort required to produce a unit change in accommodation increases, rather than stays constant, with age. Data show that the near vision response is limited to the maximum vergence response that can be tolerated and, despite being within the amplitude of accommodation, a stimulus may still appear blurred because the vergence component determines the proportion of available accommodation utilised during near vision.

Accommodation, Ocular↗
PubMed2002

Monitoring accommodative ciliary muscle function using three-dimensional ultrasound.

BACKGROUND: Our objective was to develop a three-dimensional high-resolution ultrasonic imaging technique to be utilized for in-vivo characterization of the ciliary body and the posterior iris. The benefit of this imaging in enhancing the quantification of the configurational changes in the ciliary body during accommodation is demonstrated. METHODS: Sequential ultrasound biomicroscopic images of the ciliary body region were obtained with a computer-controlled scanning device designed for use with a standard ultrasound biomicroscope for 3D imaging. Custom-made software allows online data collection, data analysis and 3D reconstruction in conjunction with commercially available VoxelView software. RESULTS: The three-dimensional presentation allows a close approximation of the ciliary muscle inside the ciliary body in vivo. We are able to distinguish and to analyze the changes in the muscle contour in different accommodation states. During accommodation a shift in the ciliary muscle center of gravity in a range of 0.04-0.26 mm (mean 0.13+/-0.06 mm) in the direction of the lens equator, with an interindividual variation and a small decrease with age, was observed. CONCLUSIONS: High-resolution ultrasound is a well established technique for in-vivo investigation of the anterior segment. Three-dimensional ultrasound biomicroscopy allows an assessment of the individual ciliary muscle activity in consideration of the ciliary processes. In combination with a contour analysis tool we improved the muscle contour determination during different accommodation states. The investigation showed an activity of the ciliary muscle in young volunteers as well as those of presbyopic age.

Accommodation, Ocular↗
PubMed2004

Influence of viewing distance on vertical strabismus.

BACKGROUND: Vertical strabismus can be modulated by the viewing distance. We report on 19 patients with this disorder. METHODS: The following squint angles were measured by the alternate prism and cover test at a viewing distance of 5 m. At 0.3 m, measurements were taken with and without an addition of 3.0 D to the corrected refraction. Cases of a dissociated vertical deviation were excluded. Fifteen patients underwent surgery. They were reexamined 3 months later. RESULTS: At a viewing distance of 5 m, the vertical deviation ranged from 0 degrees to 16 degrees (median 7 degrees ). At 0.3 m, the deviation increased by 2 degrees -15 degrees (median 7 degrees ) in 15 patients and decreased by 3.5 degrees -8 degrees (median 4.5 degrees ) in 4 patients. Eleven patients had a strabismus sursoadductorius and one had a strabismus deorsoadductorius. Eye muscle surgery reduced both the vertical deviation for distance fixation to 0 degrees -14 degrees (median 2 degrees ) and the difference between the deviations for distance and proximal fixation to 1 degrees -6 degrees (median 3 degrees ). CONCLUSIONS: In certain cases, vertical strabismus can be modulated by convergence and accommodation. This condition is frequently associated with an incomitance of the vertical deviation in side gaze. The baseline deviation can be reduced by appropriate eye muscle surgery. In cases of vertical accommodative vergence, bifocal glasses can be helpful.

Accommodation, Ocular↗
PubMed2004

Accommodation after Nd: YAG capsulotomy in patients with accommodative posterior chamber lens 1CU.

PURPOSE: After initial encouraging results with the accommodative 1CU posterior chamber lens (PCIOL), we investigated the rate, the postoperative time point of posterior capsular opacification (PCO) necessitating YAG capsulotomy and the accommodative range after Nd: YAG capsulotomy in patients with 1CU-PCIOL. PATIENTS AND METHODS: This prospective clinical study included 65 patients who underwent phacoemulsification and implantation of the accommodative 1CU-PCIOL with postoperative follow-up from 3 to 24 months. Postoperative examination was performed 3, 6 and 12 months after surgery, then before and 6 weeks after Nd: YAG capsulotomy. Measurements included: the best corrected distance visual acuity, distance refraction, near visual acuity (Birkhauser charts in 35 cm) obtained with best distance correction, accommodative range measured by subjective near point with an accodommometer and defocusing with a visual acuity fall to 0.4. RESULTS: Both best corrected distance visual acuity (1.1+/-0.1) and near visual acuity with best distance correction (0.4+/-0.1) remained stable over the follow-up period until 12 months postoperatively. The accommodative range determined by near point was stable (mean 2.0+/-0.5 D). Also, the defocusing range remained stable over 12 months (1.8+/-0.4 D). A clinically relevant posterior capsule opacification with a significant decrease of visual acuity (0.4+/-0.2) and a need for Nd: YAG capsulotomy was diagnosed in 12 patients between 15 and 22 (mean 20+/-4, median 20) months postoperatively. All capsulotomies were performed without complication. Six weeks after capsulotomy, best corrected distance visual acuity was improved (1.1+/-0.1), near visual acuity with best distance correction was 0.4+/-0.1 and the accommodative range determined by near point was 1.95+/-0.6 D and by defocusing was 1.88+/-0.47 D. Six weeks after capsulotomy, measurements of the accommodative range did not show any statistical difference to the 12-month results before the occurrence of PCO (P>0.5). CONCLUSIONS: A clinically relevant PCO with a significant decrease of visual acuity necessitating Nd: YAG capsulotomy occurred mainly after 15 postoperative months in patients with 1CU. Our results indicate that Nd: YAG capsulotomy may not affect the accommodation ability of the 1CU. Nevertheless, long-term studies are needed to further analyze the accommodative properties.

Accommodation, Ocular↗
PubMed2005

Changes of the accommodative amplitude and the anterior chamber depth after implantation of an accommodative intraocular lens.

BACKGROUND: Modern cataract surgery is interested in recovery of the accommodative power. This investigation aimed at determining pseudophakic accommodation in subjects implanted with the accommodative Human Optics 1 CU intraocular lens after drug-induced ciliary muscle stimulation by measuring the objective refraction and the changes in anterior chamber depth in comparison with a PMMA intraocular lens with rigid haptics. METHODS: The studied sample involved 30 eyes of 30 patients undergoing cataract surgery due to age-related cataract. Patients were between 50 and 77 years of age (67.71 +/- 8.0). No randomization was performed. The 1 CU accommodative intraocular lens and the PMMA intraocular lens were implanted in 15 eyes of patients with an expected visual acuity of at least 0.7. Objective refraction under pilocarpine-stimulated ciliary muscle contraction was determined with a Hartinger coincidence refractometer. The anterior chamber depth was measured with Jäger's Haag-Streit slit-lamp attachment. The accommodative amplitude and the anterior chamber flattening were calculated from the measured values. RESULTS: Twelve weeks after surgery the average accommodative amplitude in eyes with a 1 CU intraocular lens calculated from the refractive change under drug-induced stimulation was 0.48 +/- 0.36 D (with a maximum of 1.25 D). The measured change of anterior chamber depth under drug-induced stimulation was 0.3 +/- 0.32 mm (at a maximum of 0.9 mm). In the reference group with PMMA lenses, the mean accommodative amplitude derived from the refractive changes under drug-induced stimulation was 0.34 +/- 0.27 D (at a maximum of 0.85 D). The measured change in anterior chamber depth under drug-induced stimulation was 0.18 +/- 0.09 mm (at a maximum of 0.31 mm). No statistically significant differences were found between the two groups of lenses concerning change in anterior chamber depth and accommodative amplitude. CONCLUSIONS: This investigations indicate a mean anterior 1 CU shift of only 0.32 mm and a maximum of 0.9 mm. The accommodative amplitudes measured with the Hartinger coincidence refractometer (mean value 0.47 D) correspond to these values. Similar conclusions may be drawn from existing investigative results of the reference group, which are on the same order of magnitude as those of the 1 CU group. Objective accommodation measurements are needed to evaluate commercially available accommodative intraocular lenses in a scientifically satisfactory manner. Objectively measurable parameters include changes of the anterior chamber depth as well as refraction, as determined for instance by coincidence refractometry and streak retinoscopy. Future studies should also consider the IOL properties, astigmatism, and pupillary diameter. This is the only way to identify pseudoaccommodation and a decisive factor for further development of accommodative artificial lenses.

Accommodation, Ocular↗
PubMed2005

Accuracy of a new photo-refractometer in young and adult patients.

BACKGROUND: Photorefraction can be carried out in both eyes simultaneously from a distance and is therefore suitable for examination of children. This study evaluated the accuracy of a commercially available photo-refractometer (Power Refractor, Plusoptix, Erlangen, Germany) and investigated whether the working distance relaxes the accommodation sufficiently without cycloplegia. METHODS: Photo-refractometer readings were compared to cycloplegic retinoscopy. Because of the limited working range the group of patients consisted of low and moderate ametropic eyes within a spherical power of -7.0 to +5.0 D. One hundred and ninety-two eyes from 104 patients (2-81 years) were photo-refracted under cycloplegia. A subgroup of 83 eyes from 46 patients was additionally refracted without cycloplegia. RESULTS: Under cycloplegia, the Power Refractor measured the spherical equivalent slightly below that of cycloplegic retinoscopy (too much minus). The mean difference in spherical equivalent was -0.12+/-0.91 D (SD). The mean difference of cylindrical power was -0.17+/-0.73 D. The mean weighted axis difference was 0.61+/-0.71 D which is comparable to an axis deviation of 18 degrees at a cylinder power of 1.00 D. Without cycloplegia, the mean difference of the spherical equivalent was -0.73+/-1.25 D. The mean difference of cylindrical power was -0.20+/-0.65 D. The mean weighted axis difference was 0.44+/-0.58 D which is comparable to an axis deviation of 13 degrees at a cylinder power of 1.00 D. CONCLUSIONS: Without cycloplegia, the spherical equivalent of the Power Refractor tends to be underestimated due to uncontrolled accommodation, especially in children. Cycloplegia improves the accuracy in evaluating the spherical equivalent, but decreases the accuracy of cylinder power and axis.

Accommodation, Ocular↗
PubMed2005

An objective technique to measure the depth-of-focus in free space.

BACKGROUND: Determining the depth-of-focus (DOF) objectively in free space is important, as this provides information regarding the range of clear vision under more natural viewing conditions in which target blur, size, and proximal information, as well as other monocular depth cues, are present. METHODS: The DOF was assessed objectively in free space in young adults [n=20, ages 24.9+/-3.1years: myopes (n=14), emmetropes (n=5), hyperope (n=1)] by monitoring accommodation continuously using the commercially available Power Refractor II (PR II) under monocular viewing conditions. A high-contrast target ( approximately 83%) subtending a mean visual angle of 2.3 deg was placed on an optical bench at 25 cm (4 D) along the line-of-sight of the viewing right eye and was displaced slowly ( approximately 0.1-0.15 D/s) proximally and distally. This target provided blur, size, and proximal information, and other depth cues, as normally found in free space. The first consistent change in steady-state accommodative baseline level reflected one edge of the DOF. The mean dioptric difference between these distal and proximal endpoints was averaged, and this represented the total objective DOF. RESULTS: The group mean total objective DOF (n=20) was +/-0.61+/-0.09 D, with a range from +/-0.46 D to +/-0.81 D. Repeatability was excellent. CONCLUSION: A technique was developed and tested to measure the DOF in free space objectively. Further development of this technique will allow the assessment of blur perception under more complex natural viewing conditions simulating the everyday environment.

Accommodation, Ocular↗
PubMed2005

Eye preference within the context of binocular functions.

BACKGROUND: Eye preference refers to an asymmetric use of the two eyes, but it does not imply a unitary asymmetry between the eyes. Many different methods are used to assess eye preference, including eyedness questionnaires and sighting tasks that require binocular and monocular alignment of a target through a hole in the middle of a card or funnel. The results of these coarse accounts of eye preference are useful as a first screening, but do not allow for graded quantification of the manifested asymmetry in binocular vision. Moreover, they often concern only a rather selective range of binocular functions. The aim of the present study was to further differentiate eye preference within the context of other binocular functions as measured in standard optometric tests, and to validate their relation to questionnaire data of eyedness. METHODS: Conventional accounts of eye preference (German adaptation of Coren's questionnaire and a sighting task) were compared with various optometric tests of binocular function within a sample of 103 subjects. Examination included visual acuity and accommodation in each eye, stereoscopic prevalence, suppression due to binocular rivalry, fixation disparity (Mallett test). RESULTS: Sighting dominance was leftward in 32% and rightward in 68% of the cases and was highly correlated (Kendall's tau(b)=0.70) with eyedness. Further significant associations were restricted to stereoscopic prevalence which correlated with sighting dominance (tau(b)=0.55), eyedness (tau(b)=0.50), and rivalry dominance (tau(b)=0.28). CONCLUSION: Eye preference seems to be essentially reflected by eyedness, sighting dominance, and stereoscopic prevalence, but largely unrelated to fixation disparity, accommodation, and visual acuity.

Accommodation, Ocular↗
PubMed2006

Accommodating intraocular lenses: a critical review of present and future concepts.

BACKGROUND: Significant efforts have been made to develop lens implants or refilling procedures that restore accommodation. Even with monofocal implants, apparent or pseudoaccommodation may provide the patient with substantial though varying spectacle independence. True pseudophakic accommodation with a change of overall refractive power of the eye may be induced either by an anterior shift or a change in curvature of the lens optic. MATERIALS AND METHODS: Passive-shift lenses were designed to move forward under ciliary muscle contraction. This is the only accommodative lens type currently marketed (43E/S by Morcher; 1CU by HumanOptics; AT-45 by Eyeonics). The working principle relies on various hypothetical assumptions regarding the mechanism of natural accommodation. Dual-optic lenses were designed to increase the dioptric impact of optic shift. They consist of a mobile front optic and a stationary rear optic which are interconnected with spring-type haptics. With active-shift lens systems the driving force is provided by repulsing mini-magnets. Lens refilling procedures replace the lens content by an elastic material and provide accommodation by an increase of surface curvature. RESULTS: Findings with passive-shift lenses have been contradictory. While uncorrected reading vision results were initially reported to be favorable with the 1CU, and excellent with the AT-45 lens, distant-corrected near vision did not exceed that with standard monofocal lenses in later studies. Mean axial shift from laser interferometric measurements under stimulation with pilocarpine showed a moderate anterior shift with the 1CU, while the AT-45 paradoxically exhibited a small posterior shift. With the 1CU, the shift-induced accommodative effect was calculated to be less than +0.5 D in most cases, while +1 D was achieved in a single case only. Ranges and standard deviations were very large in relation to the mean values. Under physiological near-point stimulation, however, no shift was seen at all. Prevention of capsule fibrosis by extensive capsule polishing did not enhance the functional performance. Dual optic lenses are under clinical investigation and are reported to provide a significant amount of accommodation. However, possible long-term formation of interlenticular opacifications remains to be excluded. Regarding magnet-driven active-shift lens systems, initial clinical experience has been promising. Prevention of fibrotic capsular contraction is crucial, and it has been effectively counteracted with a special capsular tension ring, or lens fixation technique, together with capsule polishing. Lens refilling has been extensively studied in the laboratory and in primates. Though it offers great potential for fully restoring accommodation, a variety of problems must be solved, such as achieving emmetropia in the relaxed state, adequate response to ciliary muscle contraction, satisfying image quality over the entire range of accommodation and sustained functioning. The key problem, however, is again after-cataract prevention. CONCLUSIONS: As opposed to psychophysical evaluation techniques, laser interferometry measures what shift lenses are designed to provide: axial shift on accommodative effort. While under pilocarpine some movement was recorded, no movement at all was found under near-point stimulation with any of the lenses currently marketed. In contrast, magnetic-driven active-shift lens systems carry the potential of sufficiently topping up apparent accommodation to provide for clinically useful accommodation while using conventional lens designs with proven after-cataract performance. Dual optic implants significantly increase the impact of axial optic shift. The main potential problem, however, is delayed formation of interlenticular regenerates. Lens refilling procedures offer the potential of fully restoring accommodation due to the great impact of increase in surface curvature on refractive lens power. However, various problems remain to be solved before clinical use can be envisaged, above all, again, after-cataract prevention. The concept of passive single-optic shift lenses has failed. Concomitant poor capsular bag performance makes these lenses an unacceptable trade-off. Magnet-assisted systems potentially combine clinically useful accommodation with satisfactory after-cataract performance. Dual optic lenses theoretically offer substantial accommodative potential but may allow for interlenticular after-cataract formation. Lens refilling procedures have the greatest potential for fully restoring natural accommodation, but will again require years of extensive laboratory and animal investigations before they may function in the human eye.

Accommodation, Ocular↗
PubMed2006

Evidence for frequent divergence impairment in French dyslexic children: deficit of convergence relaxation or of divergence per se?

AIM: There is a controversy as to whether dyslexic children present visuo-motor disabilities such as vergence and accommodative problems assessed with orthoptic tests. The purpose of this study is to re-examine this issue in a large population of children. METHODS: Extensive orthoptic evaluation was made in 57 dyslexic and 46 non-dyslexic ("normal") age-matched children. Convergence and divergence capacities were evaluated at two distances (30 cm and 400 cm). RESULTS: Binocular vision measured with stereo-acuity tests was normal in dyslexics. In contrast, the near point of convergence was significantly more remote in dyslexics; most importantly, divergence at both far and near distance was significantly more reduced in dyslexics (median value 4 pD and 10 pD, respectively, at far and near) than in "normals" (median value 6 pD and 12 pD, at far and near). CONCLUSION: The existence of the divergence deficit at far distance indicates the presence of deficit of divergence per se, independently from convergence and accommodation relaxation. This result is novel and corroborated by physiological studies indicating distinct control of convergence and divergence, both at the cortical and subcortical premotor level. We conclude that vergence deficits are frequently present in dyslexics, and that dyslexics should be re-educated; training should address distinctively convergence and divergence subsystems.

Accommodation, Ocular↗
PubMed1999

In vivo imaging of the human zonular apparatus with high-resolution ultrasound biomicroscopy.

BACKGROUND: To investigate the potential of high-resolution ultrasound biomicroscopy (UBM) for studying the zonular apparatus of human beings in vivo. METHODS: Using transducer frequencies of 34 MHz and 50 MHz, criteria were developed to identify transcorneal and transscleral sections that allowed reproducible identification of the different fiber groups of the zonular architecture. For that purpose, 10 volunteers between the ages of 14 and 41 years underwent high-resolution ultrasound biomicroscopy under conditions of consensual far- and near-accommodation. The online video recordings of the respective UBM investigations were afterwards analyzed image by image. Good visibility of zonular fibers was obtained when the ultrasound wave propagation comprised an angle close to 90 degrees with the fiber orientation and when the oscillations of the UBM scan had a strict radial orientation towards the limbus and avoided, simultaneously, the ciliary processes. RESULTS: In all the volunteers, high-resolution ultrasound biomicroscopy imaged the zonular fiber groups known from histology. In addition, it detected fibers that do not follow the course of the inner ciliary body surface but take a direct route from the ora serrata to the lens. It also demonstrated that fibers that seem to change direction at crossings with other fibers. Under conditions of near-accommodation, the zonular fibers showed signs of relaxation. CONCLUSIONS: High-resolution ultrasound biomicroscopy seems well suited for in vivo investigations of the zonular apparatus and of accommodation in man. The results support the fundamental features of the Helmholtz theory on accommodation.

Accommodation, Ocular↗
PubMed2003

Can tonic accommodation predict surgical performance?

BACKGROUND: Pilots undergo many visual tests for both selection and assessment, and we know that there are many similarities between pilots and surgeons. Hence, it would not be unreasonable to bring similar visual tests into surgery. Tonic accommodation (TA) is a stable parameter that is adopted by the eye in the absence of any stimulation. Over recent years, surgery has undergone change from traditional open surgery to minimally invasive procedures, bringing many advantages. However, not every surgeon has the ability to perform under conditions where the operative field is represented on a flat monitor. METHOD: We determined the TA values in medical students and then correlated this with their performance on a virtual reality surgical simulator. RESULTS: We found that TA values predicted the number of errors made with the dominant hand, accounting for 27% of the variance. CONCLUSION: The data suggest that TA may play a role in the individual differences that are noted when surgeons perform laparoscopic surgery. Further studies are needed to evaluate the exact role of TA in surgical performance.

Accommodation, Ocular↗
PubMed2004

Three-dimensional analysis of dentist's eye movements.

We measured the eye movements of a dentist while a pediatric patient walked toward a dental chair. Bilateral eye movements were measured and analyzed three-dimensionally based on the angle of convergence. The frequency of fixation points registered in each test ranged from 2 to 11, with an average of 6.6. No significant differences were observed when the experiments were grouped according to the age of the observed child. In 13 out of 74 experiments, the calculated distances between the observer and the fixation points corresponded to the actual distances. According to the patterns of where the fixation points occurred, 13 experiments had an "inside-outside" pattern and 61 had an "outside-only" pattern. None of the experiments had an "inside-only" pattern. The "outside-only" group was further subclassified into 50 "behind-only" patterns, 5 "in front-only" patterns, and 6 "in-front-and-behind" patterns. As far as depth perception is concerned, the angle of convergence determined by the eye movements would rarely correspond to the actual distance between the observer and the fixation point.

Accommodation, Ocular↗
PubMedDate not supplied

Effects of an eyeglass-free 3-D display on the human visual system.

PURPOSE: To investigate the effect on the human visual system of viewing 3-dimensional (3-D) computer graphics (CG) images with an eyeglass-free rear-cross-lenticular-type 3-D display. METHODS: Positive accommodation velocity (GRAD) during the accommodative step response was measured in ten healthy young adults before and after they viewed CG images. Although the distance between the viewer and the 3-D display was 600 mm, the apparent distance between the viewer and the virtual object was varied (515, 600, and 722 mm) by changing the visual disparity. RESULTS: A significant slowdown of average GRAD was observed by 60 min after a 30-min 3-D viewing of 3-D CG images [P<0.05, analysis of variance (ANOVA)] but not after a 30-min viewing of the CG images on a 2-D display or after a 15-min 3-D viewing. When the virtual object was at 722 mm, a significant slowdown of average GRAD was observed only at 30 min after the 30-min 3-D viewing (P<0.05, ANOVA). When the virtual object was at 515 mm, a significant slowdown of average GRAD was observed at 30 and 60 min after the 3-D viewing (P<0.05, ANOVA). CONCLUSIONS: The effect on the human visual system of 3-D viewing of 3-D CG images depends on both the duration of the viewing and the apparent distance between the viewer and the virtual objects.

Accommodation, Ocular↗
PubMedDate not supplied

Near reflex substituting for acquired horizontal gaze palsy: a case report.

BACKGROUND: Some patients with acquired horizontal gaze palsy overcome the adduction palsy by utilizing convergence. This substitution phenomenon is very rare. We report a patient with horizontal gaze palsy who was able to use convergence to compensate for the lack of adduction in the left eye. CASE: The patient was a 31-year-old woman with an arteriovenous malformation in the fourth ventricle. She suffered right gaze palsy and right abducens palsy after tumor surgery and radiation therapy. OBSERVATIONS: Three years after the vascular accident, she was found to be able to adduct the left eye, in association with the adduction of the right eye. At the same time, constriction of both pupils and globe retraction of the left eye were observed. When she shifted the gaze direction of her left eye from left to right, an 11 and 8 diopter increase of myopia in the right and left eyes, respectively, was confirmed by objective refractometry. CONCLUSIONS: The existence of convergence substituting for adduction in this patient with horizontal gaze palsy was confirmed by refraction change in addition to pupillary change.

Abducens Nerve↗
PubMedDate not supplied

Myopia control trial with progressive addition lenses in Japanese schoolchildren: baseline measures of refraction, accommodation, and heterophoria.

PURPOSE: To describe baseline measures of refraction, accommodation, and heterophoria in Japanese schoolchildren enrolled in a randomized clinical trial that examines whether progressive addition lenses slow myopic progression compared with single-focus lenses. METHODS: Ninety-five children with myopia between -1.25 and -6.00 D spherical equivalent were recruited. Their ages ranged from 6 to 12 years; 46% were girls. The main outcome measure for the trial was progression of myopia determined by cycloplegic (0.5% tropicamide) autorefraction. Accommodative lags and heterophoria were also evaluated. RESULTS: Because data were similar in both eyes, they are reported for the right eye only. The mean (+/-SD) cycloplegic autorefraction (spherical equivalent) was -3.22 +/- 1.22 D. The cycloplegic subjective refraction was larger (less myopic) than the noncycloplegic subjective refraction by 0.25 +/- 0.22 D. The mean distance prescription was larger (undercorrection) than the mean cycloplegic autorefraction by 0.74 +/- 0.37 D. The mean accommodative lag for a 4.74 D target was 2.05 +/- 0.98 D. Near-point esophoria was found in 29 (31%) of the children when their refractive errors were fully corrected with glasses. CONCLUSIONS: The measurements reported herein will serve as a basis for assessing changes that occur over a 3-year follow-up period. Compared with the baseline measurements in the Correction of Myopia Evaluation Trial, clear differences were observed in the mean cycloplegic autorefraction and distance prescriptions. The accommodation and heterophoria data showed characteristics similar to those recently reported in myopic children abroad.

Accommodation, Ocular↗