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Davies LN, Biswas S, Bullimore M, Cruickshank F, Estevez JJ, Khanal S, Kollbaum P, Marcotte-Collard R, Montani G, Plainis S, Richdale K, Simard P, Wolffsohn JS. BCLA CLEAR presbyopia: Mechanism and optics. Cont Lens Anterior Eye 2024:102185. [PMID: 38796331 DOI: 10.1016/j.clae.2024.102185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2024]
Abstract
With over a billion adults worldwide currently affected, presbyopia remains a ubiquitous, global problem. Despite over a century of study, the precise mechanism of ocular accommodation and presbyopia progression remains a topic of debate. Accordingly, this narrative review outlines the lenticular and extralenticular components of accommodation together with the impact of age on the accommodative apparatus, neural control of accommodation, models of accommodation, the impact of presbyopia on retinal image quality, and both historic and contemporary theories of presbyopia.
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Affiliation(s)
- Leon N Davies
- School of Optometry, College of Health and Life Sciences, Aston University, Birmingham, UK.
| | - Sayantan Biswas
- School of Optometry, College of Health and Life Sciences, Aston University, Birmingham, UK
| | | | - Fiona Cruickshank
- Division of Pharmacy and Optometry, School of Health Sciences, Faculty of Biology, Medicine and Health, University of Manchester, UK
| | - Jose J Estevez
- Caring Futures Institute, College of Nursing and Health Sciences, Optometry and Vision Science, Flinders University, Adelaide, Australia; Flinders Centre for Ophthalmology, Eye and Vision Research, Department of Ophthalmology, Flinders University, Adelaide, Australia
| | - Safal Khanal
- Department of Optometry and Vision Science, The University of Alabama at Birmingham, USA
| | | | | | | | - Sotiris Plainis
- Laboratory of Optics and Vision, School of Medicine, University of Crete, Greece
| | | | - Patrick Simard
- School of Optometry, Universite de Montreal, Montreal, Quebec, Canada
| | - James S Wolffsohn
- School of Optometry, College of Health and Life Sciences, Aston University, Birmingham, UK
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Modrzejewska M, Durajczyk M. The Relationship between Selected Parameters and the Occurrence of Premyopia in a Group of 1155 Children Aged 8 in Northwestern Poland. J Clin Med 2024; 13:1977. [PMID: 38610742 PMCID: PMC11012722 DOI: 10.3390/jcm13071977] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Revised: 03/17/2024] [Accepted: 03/26/2024] [Indexed: 04/14/2024] Open
Abstract
Background: Determination of the number of pupils at risk of developing pre-myopia and selected ophthalmic parameters in a group of 1155 children aged 8. Material: Ophthalmic examinations were performed in Polish 8-year-old, /1518 individuals/; 1155 of whom presented complete data for analysis. There was a total of 554 (47.9%) girls and 602 (52.1%) boys. Examination of the anterior and posterior segment of the eye, evaluation of accommodation, convergence, heterophoria, alignment of the eyeball, muscular balance with ocular mobility in 9 directions of gaze, and spatial vision were tested. Refraction was obtained under cycloplegia. Refractions (spherical equivalent, SE). were categorized as pre-myopia (-0.50 D-+0.75 D), myopia (≤-0.5 D), emmetropia (>-0.5 D to ≤+0.5 D), mildly hyperopia (>+0.5 D to ≤+2.0 D) and hyperopia (>+2.0 D). Data analysis was performed using Statistica 13.5 software: chi-squared, Pearson's, t-Student, and U Mann-Whitney tests. p-values of <0.05 were considered statistically significant. Results: Pre-myopia was diagnosed in as many as 704 subjects (60.9%) with a similar frequency among both girls-328 (46.6%)-and boys with 376 (53.4%). Conclusions: Current data indicates that the growing group of myopic individuals in many industrialized countries is the sixth most common cause of blindness. Further research is crucial to understand the factors underlying accommodative and binocular mechanisms for myopia development and progression and to make recommendations for targeted interventions to slow the progression of myopia in a group of early school children.
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Redondo B, Vera J, Molina R, Davies LN, Jiménez R. Accommodative dynamics and attention: the influence of manipulating attentional capacity on accommodative lag and variability. Ophthalmic Physiol Opt 2020; 40:510-518. [DOI: 10.1111/opo.12690] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 03/27/2020] [Accepted: 03/31/2020] [Indexed: 01/31/2023]
Affiliation(s)
| | - Jesús Vera
- Department of Optics University of Granada Granada Spain
| | - Rubén Molina
- Department of Optics University of Granada Granada Spain
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Redondo B, Vera J, Carreño--Rodríguez C, Molina-Romero R, Jiménez R. Acute Effects of Caffeine on Dynamic Accommodative Response and Pupil Size: A Placebo-controlled, Double-blind, Balanced Crossover Study. Curr Eye Res 2020; 45:1074-1081. [DOI: 10.1080/02713683.2020.1725060] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Beatriz Redondo
- Department of Optics, Faculty of Sciences, University of Granada, Granada, Spain
| | - Jesús Vera
- Department of Optics, Faculty of Sciences, University of Granada, Granada, Spain
| | | | - Rubén Molina-Romero
- Department of Optics, Faculty of Sciences, University of Granada, Granada, Spain
| | - Raimundo Jiménez
- Department of Optics, Faculty of Sciences, University of Granada, Granada, Spain
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Objective User Visual Experience Evaluation When Working with Virtual Pixel-Based 3D System and Real Voxel-Based 3D System. PHOTONICS 2019. [DOI: 10.3390/photonics6040106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Volumetric display shows promising implications for healthcare related applications as an innovative technology that creates real three-dimensional (3D) image by illuminating points in three-dimensional space to generate volumetric images without image separation. We used eccentric photorefractometry to objectively study ocular performance in a practical environment by evaluating near work-induced refraction shift, accommodative microfluctuations, and pupil size for 38 young adults after viewing anaglyph, and volumetric 3D content for prolonged time. The results of our study demonstrate that participants who performed relative depth estimation task on volumetric 3D content were less likely to experience task-induced myopic refraction shift. For both 3D content types, we observed pupil constriction, that is possibly related to visual fatigue. For anaglyph 3D pupil constriction, onset was observed significantly sooner, compared to volumetric 3D. Overall, sustained work with 3D content, and small disparities or the fully eliminated possibility of accommodation-vergence conflict, not only minimizes near work-induced myopic shift, but also provide beneficial accommodation relaxation that was demonstrated in this study as hypermetropic shift for nearly half of participants.
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Hynes NJ, Cufflin MP, Hampson KM, Mallen EAH. Cognitive Demand and Accommodative Microfluctuations. Vision (Basel) 2018; 2:vision2030036. [PMID: 31735899 PMCID: PMC6836075 DOI: 10.3390/vision2030036] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 08/31/2018] [Accepted: 09/04/2018] [Indexed: 12/29/2022] Open
Abstract
Previous studies have shown cognition to have an influence on accommodation. Temporal variation in the accommodative response occurs during the fixation on a stationary target. This constantly shifting response has been called accommodative micro-fluctuations (AMFs). The aim of this study is to determine the effects of increasing task cognitive demand on the ocular accommodation response. AMFs for 12 myopes and 12 emmetropes were measured under three conditions of varying cognitive demand and comprising reading of numbers (Num), simple arithmetic (SA), and complex arithmetic (CA). Fast Fourier transforms were used to analyze the different frequency band components of the AMFs. Other aspects of AMFs including root mean square accommodation values and chaos analysis was applied. A repeated measures ANOVA revealed a significant main effect of cognition in the mean power of the high frequency component (HFC) (F2,44 = 10.03, p < 0.005). Pairwise analyses revealed that these differences exist between SA and CA tasks (p < 0.005) and the Num and CA (p < 0.005) tasks with the HFC power being the highest for the CA condition. It appears that the difficulty of a task does affect active accommodation but to a lesser extent than other factors affecting accommodation.
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Affiliation(s)
- Niall J. Hynes
- School of Optometry & Vision Science, University of Bradford, Bradford BD7 1DP, UK
- Correspondence:
| | - Matthew P. Cufflin
- School of Optometry & Vision Science, University of Bradford, Bradford BD7 1DP, UK
| | - Karen M. Hampson
- Department of Engineering Science, University of Oxford, Oxford OX1 3PJ, UK
| | - Edward A. H. Mallen
- School of Optometry & Vision Science, University of Bradford, Bradford BD7 1DP, UK
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Publications: Bernard Gilmartin. Ophthalmic Physiol Opt 2011; 31:430-5. [PMID: 21831074 DOI: 10.1111/j.1475-1313.2011.00865.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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The effect of proximity on open-loop accommodation responses measured with pinholes. Ophthalmic Physiol Opt 2010; 30:365-70. [DOI: 10.1111/j.1475-1313.2010.00728.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Vision and the hypothalamus. ACTA ACUST UNITED AC 2010; 81:100-15. [DOI: 10.1016/j.optm.2009.07.016] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2008] [Revised: 06/04/2009] [Accepted: 07/13/2009] [Indexed: 01/01/2023]
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van Alphen GW. Emmetropization in the primate eye. CIBA FOUNDATION SYMPOSIUM 2007; 155:115-20; discussion 120-5. [PMID: 2128476 DOI: 10.1002/9780470514023.ch7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A theory to explain the mechanism of emmetropization of the human eye is reviewed and updated. The theory is probably also valid for the primate eye. It is proposed that the ciliary muscle-choroid layer behaves like a solid sheet of smooth muscle, so that it is able to resist part of the intraocular pressure and to regulate scleral stretch in the growing eye. It is suggested that the autonomic nervous system and stress play a role in the development of ametropia and that interference with the cortical-subcortical control of the ciliary muscle may prevent emmetropization.
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Affiliation(s)
- G W van Alphen
- The Netherlands Ophthalmic Research Institute, Amsterdam, Zuidoost
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Chen JC, Schmid KL, Brown B. The autonomic control of accommodation and implications for human myopia development: a review. Ophthalmic Physiol Opt 2003; 23:401-22. [PMID: 12950887 DOI: 10.1046/j.1475-1313.2003.00135.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Prolonged nearwork has long been associated with myopia development, however, there is no well described linking mechanism. One theory suggests that if accommodation accuracy during nearwork is not maintained, the defocused retinal image leads to myopia development. Here we review the findings of research aimed at determining whether the autonomic inputs to the ciliary smooth muscle are involved in this type of environmental myopia. We examine whether an autonomic imbalance could be a precursor to axial elongation and the resulting myopia. Accommodation responses, such as tonic accommodation and nearwork-induced accommodative adaptation, as a function of refractive error, are described in relation to an autonomic imbalance model. The collective results of this research point to anomalous accommodation responses, possibly as a result of underlying anomalous autonomic input to the ciliary muscle, being involved in myopia development and progression.
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Affiliation(s)
- Jennifer C Chen
- Centre for Eye Research, School of Optometry, Queensland University of Technology, Victoria Park Road, Kelvin Grove, Brisbane QLD 4059, Australia.
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12
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Abstract
PURPOSE Accommodation and vergence both appear to be influenced by multiple nonsensory factors. "Effort-to-see" is one of these factors. This study was designed to assess the extent to which effort-to-see affects accommodation and vergence. METHOD Nine volunteers participated in this study. Stimuli were chosen to stimulate selectively either accommodation or vergence. Accommodation and vergence responses were measured while observers viewed each stimulus with the instruction of "concentrate" or "space-out." RESULTS Both oculomotor adjustments were accurate when observers "concentrated," but regressed toward the resting posture during identical stimulus conditions when observers spaced-out. Interesting, individual differences in oculomotor behavior were apparent. CONCLUSION This study demonstrates that higher-level attentional factors play an important role in accommodation and vergence for active exploration of the three-dimensional environment.
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Affiliation(s)
- Ellie L Francis
- Division of Ophthalmology, Children's Hospital of Philadelphia, Philadelphia, PA, USA
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Andre JT, Owens DA. Predicting optimal accommodative performance from measures of the dark focus of accommodation. HUMAN FACTORS 1999; 41:139-145. [PMID: 10354810 DOI: 10.1518/001872099779577309] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Leibowitz and his colleagues found that accommodation rests at an intermediate distance that shows wide interindividual variation. They proposed that this intermediate dark focus is useful for correcting anomalous refractive errors, but this proposal was later questioned when different measurement techniques yielded discrepant dark focus values. The present study measured dark focus under two levels of visual attentiveness: (a) when performing an open-loop, active viewing task (aDF); and (b) when looking passively into darkness (pDF). These dark focus measures were then compared with an optimal accommodation distance that was derived from accommodative response functions in bright and dim luminance. The aDF measures were found to be more myopic (nearer) than the pDF measures and highly correlated with the optical accommodation distance. No significant relationship was found between pDF and optical accommodation distance. These findings confirm that measures of dark focus are affected by nonoptical aspects of the measurement technique; they also suggest that techniques that demand visual attention (aDF) yield dark focus values that are more useful for optimizing accommodation and potentially reducing fatigue in difficult situations.
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Affiliation(s)
- J T Andre
- Franklin & Marshall College, Lancaster, Pennsylvania 17604-3003, USA
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Abstract
In the absence of an adequate visual stimulus, accommodation adopts an intermediate position of approximately 1 D. Since this position was believed to reflect the level of tonic innervation to the ciliary muscle, this response has been termed tonic accommodation (TA). Part I of this review will consider various aspects of this parameter, including its reference to closed-loop accommodative function and autonomic physiology. In addition, both the methods of measurement and appropriate terminology for this function will be discussed. It is concluded that the response, which becomes apparent under so-called 'stimulus-free' conditions, in fact probably represents an aggregate response resulting from multiple, non-optical stimuli. Thus the designation tonic accommodation may not be appropriate, since it fails to describe accurately the heterogeneous composition of the stimulus-free accommodative response. An associated paper (to be published as part II of this review) will examine accommodative adaptation and both clinical aspects of TA and adaptation of TA.
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Affiliation(s)
- M Rosenfield
- Department of Vision Sciences, State University of New York/State College of Optometry, NY 10010
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15
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Iwasaki T. Effects of a visual task with cognitive demand on dynamic and steady-state accommodation. Ophthalmic Physiol Opt 1993; 13:285-90. [PMID: 8265169 DOI: 10.1111/j.1475-1313.1993.tb00470.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Dynamic accommodative response before and after, and steady-state accommodation during, a visual task were measured using an infrared optometer to investigate the effects of psychological stress on accommodative facility. Increase in the post-task dynamic accommodation response time (for a near-to-far condition) was greater for a group of subjects given a mental task at a higher presentation speed. In addition the steady-state accommodation showed an inward shift under a closed-loop condition which was enhanced when computation time was decreased. However, an inward shift was not evident when the performance level of subjects increased following training. The relationship between psychological stress, cognitive demand and accommodative function is discussed.
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Affiliation(s)
- T Iwasaki
- Department of Ophthalmology, University of Occupational and Environmental Health, Japan
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16
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Winn B, Gilmartin B, Mortimer LC, Edwards NR. The effect of mental effort on open- and closed-loop accommodation. Ophthalmic Physiol Opt 1991. [DOI: 10.1111/j.1475-1313.1991.tb00234.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Abstract
We tested whether near retinoscopy, a noncycloplegic retinoscopic technique, was applicable to the optic correction of patients with accommodative esodeviations. We performed a study in 17 patients with accommodative esotropia to compare the refractive values obtained by near retinoscopy and by cycloplegia, as measured by two examiners. The interobserver variability was the same for the two techniques for the refractive values of the horizontal and vertical meridia and spherical equivalent. For the astigmatism, there was greater variability for near retinoscopy. The correlation between the two methods was good, but the variability of the differences was high. We recommend that near retinoscopy should be employed only as a noninvasive method for screening refractive errors in children.
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Affiliation(s)
- A A Velasco Cruz
- Department of Ophthalmology and Otorhinolaryngology, School of Medicine, University of São Paulo, Brazil
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Bullimore MA, Gilmartin B. The measurement of adaptation of tonic accommodation under two open-loop conditions. Ophthalmic Physiol Opt 1989; 9:72-5. [PMID: 2594383 DOI: 10.1111/j.1475-1313.1989.tb00810.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Pre- and post-task tonic accommodation (TA) was measured using an objective infra-red optometer under two open-loop conditions: a darkroom and a bright empty-field (60 cd m-2). The task was of 10 minutes' duration and was located at -1, -3 and -5 D. Post-task TA was measured immediately after the task and over a period of 90 s. Mean data for the group of 10 young men subjects showed that the open-loop condition adopted had no significant influence on the post-task regression patterns of TA towards pre-task values. Three subjects did, however, show significantly more sustained increases in post-task TA for the bright-field condition; one markedly so. Conversely, two subjects showed more pronounced post-task shifts for the darkroom condition.
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Affiliation(s)
- M A Bullimore
- Department of Vision Sciences, Aston University, Birmingham, UK
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Amerson TL, Mershon DH. Time-of-day variations in oculomotor function: I. Tonic accommodation and tonic vergence. Ophthalmic Physiol Opt 1988; 8:415-22. [PMID: 3253633 DOI: 10.1111/j.1475-1313.1988.tb01178.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Time-of-day variations were studied both in tonic accommodation and in tonic vergence. Thirty-six male volunteers were measured once in the morning and at one other time on the same day. The mean baseline value of tonic accommodation was 2.02 D. Time-of-day variations were found, with a late evening measure being +0.6 D greater than the morning value. No independent time-of-day fluctuations were found in tonic vergence. Post-hoc analysis, however, showed that tonic vergence tended to shift in the same direction as an individual's tonic accommodation during the afternoon. During the evening, tonic vergences tended to shift oppositely to tonic accommodation.
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Affiliation(s)
- T L Amerson
- North Carolina State University, Raleigh 27695
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Abstract
Three subjective techniques for measuring accommodation (polarized vernier optometer, laser optometer, and a hand optometer based on the vernier principle) were used to measure subjects' dark focus while they performed a short-term mental arithmetic task. Compared with the initial values measured without the arithmetic task, significant changes in dark focus occurred when the task was performed. The effects depended on the initial dark focus of the subjects: in far-dark-focus subjects, inward shifts were generally observed; in near-dark-focus subjects, the dark focus shifted in different directions when different measuring techniques were used. The individual changes in dark focus due to the mental task were reproducible when the mean dark focus of the group shifted inward and when the same technique for measuring accommodation was used. The results have implications for the interpretation of dark focus shifts that are found following prolonged visual work at close distances, e.g. at visual display terminals.
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Bullimore MA, Gilmartin B. The accommodative response, refractive error and mental effort: 1. The sympathetic nervous system. Doc Ophthalmol 1988; 69:385-97. [PMID: 3203603 DOI: 10.1007/bf00162751] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The accommodative response of 12 emmetropic subjects 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. The imposition of mental effort induced a significant increase in mean response for the -1 D stimulus, a response equivalent to the passive condition at -3 D and a reduction in response at -5 D. Mental effort induced similar responses for the -1 D and -3 D locations when sympathetic innervation to the ciliary muscle was blocked with the beta-receptor antagonist timolol maleate. Responses for the -5 D location were, however, significantly increased. It is proposed that sympathetic inhibition can modify the effect of mental effort on near accommodative responses.
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Affiliation(s)
- M A Bullimore
- Department of Vision Sciences, Aston University, Birmingham, UK
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Zetterström C. Effects of adrenergic drugs on accommodation and distant refraction in daylight and darkness. A laseroptometric study. Acta Ophthalmol 1988; 66:58-64. [PMID: 2896425 DOI: 10.1111/j.1755-3768.1988.tb08535.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Near point accommodation was measured using a RAF near point rule, and distant refraction in daylight and darkness were determined using a laseroptometer in a double-blind cross-over study on 10 healthy test subjects (19-31 years). Determinations were made before and 40 min after topical instillations of 3 X 10 microliters 10% phenylephrine, 0.5% thymoxamine, 1% adrenaline, 3% isoproterenol, 0.5% timolol and 0.5% betaxolol. Combinations of 3 X 10 microliters 0.5% thymoxamine + 10% phenylephrine, 0.5% timolol + 1% adrenaline and 0.5% betaxolol + 3% isoproterenol were also administered. The near point of accommodation decreased 0.8 +/- 0.3 diopter after instillations of the alpha 1 adrenoceptor agonist phenylephrine, while an increase of 0.6 +/- 0.2 diopter was determined after administration of the alpha adrenoceptor antagonist thymoxamine. Thymoxamine plus phenylephrine did not alter the pretreatment values. Beta adrenoceptor stimulation by isoproterenol or beta adrenoceptor inhibition by timolol or betaxolol had no effect on the near point accommodation. The difference between distant refraction in daylight and darkness, that is low-luminance myopia, amounted to -1.25 +/- 0.1 diopter. Phenylephrine caused a myopic shift in distant refraction in daylight and darkness of 0.32 +/- 0.1 and 0.9 +/- 0.2 diopter, respectively. This effect was due to the mydriatic action of phenylephrine.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- C Zetterström
- Department of Ophthalmology, University Hospital of Uppsala, Sweden
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Abstract
To measure the accommodative state of the eye in a stimulus free condition, the so called dark focus, a simple optometer was constructed based on the principle of the polarized vernier optometer originally proposed by Moses (1971). Data obtained with this hand optometer were compared with those of two other subjective techniques, the polarized vernier optometer and the laser optometer, we were found to be similar. The advantage of this hand optometer is that it is a convenient device that allows one to measure the dark focus within minutes, under normal room lighting.
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