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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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Turull-Mallofré A, García-Guerra CE, Mestre C, Vilaseca M, Pujol J, Aldaba M. Influence of power and the time of application of fogging lenses on accommodation. BIOMEDICAL OPTICS EXPRESS 2023; 14:5488-5498. [PMID: 37854562 PMCID: PMC10581808 DOI: 10.1364/boe.486442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 06/15/2023] [Accepted: 06/28/2023] [Indexed: 10/20/2023]
Abstract
Fogging is a non-invasive technique based on the use of positive spherical power lenses to relax accommodation during refraction that is commonly used as an alternative to cycloplegic drugs. Although the mechanism of the fogging technique has been described, some aspects of its methodology remain unclear. The main purpose of this work was to determine which lens power and time of application are more suitable for achieving a successful relaxation of accommodation by analyzing the changes in accommodation when fogging lenses of different powers were placed in front of the participants' eye for a certain timespan. The results of this analysis showed, in general, that low-power lenses and timespans of less than half a minute provided the highest relaxation of accommodation. However, high inter-subject variability was found in the two variables (power and time).
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Affiliation(s)
- Aina Turull-Mallofré
- Centre for Sensors, Instruments and Systems Development, Universitat Politècnica de Catalunya, Rambla Sant Nebridi 10, Terrassa, 08222, Spain
| | - Carlos E. García-Guerra
- Centre for Sensors, Instruments and Systems Development, Universitat Politècnica de Catalunya, Rambla Sant Nebridi 10, Terrassa, 08222, Spain
| | - Clara Mestre
- Centre for Sensors, Instruments and Systems Development, Universitat Politècnica de Catalunya, Rambla Sant Nebridi 10, Terrassa, 08222, Spain
| | - Meritxell Vilaseca
- Centre for Sensors, Instruments and Systems Development, Universitat Politècnica de Catalunya, Rambla Sant Nebridi 10, Terrassa, 08222, Spain
| | - Jaume Pujol
- Centre for Sensors, Instruments and Systems Development, Universitat Politècnica de Catalunya, Rambla Sant Nebridi 10, Terrassa, 08222, Spain
| | - Mikel Aldaba
- Centre for Sensors, Instruments and Systems Development, Universitat Politècnica de Catalunya, Rambla Sant Nebridi 10, Terrassa, 08222, Spain
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20-20-20 Rule: Are These Numbers Justified? Optom Vis Sci 2023; 100:52-56. [PMID: 36473088 DOI: 10.1097/opx.0000000000001971] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
SIGNIFICANCE The use of digital devices has increased substantially in recent years across all age groups for both vocational and avocational purposes. There are a wide range of proposed therapeutic and management options for this condition, including optical, medical, and ergonomic interventions. PURPOSE Regular breaks are frequently recommended by clinicians to minimize digital eye strain. The so-called 20-20-20 rule, whereby individuals are advised to fixate on an object at least 20 feet (6 m) away for at least 20 seconds every 20 minutes is widely cited. Unfortunately, there is relatively little peer-reviewed evidence to support this rule. The aim of this investigation was to determine whether scheduled breaks are effective in reducing the adverse effects of digital device usage. METHODS The study was carried out on 30 young subjects who performed a 40-minute, cognitively demanding reading task from a tablet computer. The task required them to read random words and to identify which ones began with a specific letter chosen by the experimenter. The task was undertaken on four separate occasions, with 20-second breaks being allowed every 5, 10, 20, or 40 minutes (i.e., no break), respectively. Both before and after each trial, subjects completed a questionnaire regarding ocular and visual symptoms experienced during the session. In addition, both reading speed and task accuracy were quantified during each trial. RESULTS A significant increase in post-task symptoms (with respective to the pre-task value) was observed for all four trials ( P < .001). However, there was no significant effect of scheduled breaks on reported symptoms ( P = .70), reading speed ( P = .93), or task accuracy ( P = .55). CONCLUSIONS Although widely cited as a treatment option, these results do not support the proposal of using 20-second scheduled breaks as a therapeutic intervention for digital eye strain.
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Affiliation(s)
- W Neil Charman
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
E‐mail:
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Bharadwaj SR, Roy S, Satgunam P. Spasm of Near Reflex: Objective Assessment of the Near-Triad. Invest Ophthalmol Vis Sci 2021; 61:18. [PMID: 32663291 PMCID: PMC7425728 DOI: 10.1167/iovs.61.8.18] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Purpose To characterize binocular steady-state accommodation, pupil and convergence responses (near triad) in spasm of near reflex (SNR) before and after optical and pharmacological intervention. To identify the putative source of SNR in the neural control schema of accommodation-vergence interaction using controls-engineering modeling. Methods Near-triad of 15 patients with SNR (9 to 23 years) was recorded using an infrared photorefractor at 2m viewing distance for 120s during clinical presentation, after optical fogging intended to relieve spasm, with cycloplegia, post-cycloplegia and long-term follow-up visits. Data were also collected without cycloplegia in 15 age-matched controls. Schor (1999) model was used to computationally simulate accommodation and vergence responses of controls and SNR. Results Both eyes of SNR exhibited significant myopia and refraction fluctuations (<1.0Hz) during clinical presentation [median (25th to 75th IQR) refraction: −1.7D (−3.2 to −0.8D); root mean squared (RMS) deviation: 1.1D (0.5 to 1.5D)], relative to controls [0.8D (−0.03 to 1.4D); 0.2D (0.1 to 0.3D)] (p < 0.001). These decreased after optical fogging, largely eliminated with cycloplegia and partially re-appeared in the post-cycloplegia and follow-up visits. SNR responses could be modeled by increasing the gain and decay time of tonic accommodation, vis-à-vis, controls. Pupil and convergence responses in SNR were similar to controls at all visits (p > 0.1). Conclusions Exaggerated fluctuations of steady-state accommodation may be a signature feature of SNR, even while their pupil and convergence responses may remain unaffected. These fluctuations may arise from the tonic accommodation controller, the properties of which could be potentially altered after optical fogging to relieve the disorder.
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Wang D, Jin N, Pei RX, Zhao LQ, Du B, Liu GH, Wang XL, Wei RH, Li XR. Comparison between two autorefractor performances in large scale vision screening in Chinese school age children. Int J Ophthalmol 2020; 13:1660-1666. [PMID: 33078119 DOI: 10.18240/ijo.2020.10.22] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Accepted: 05/18/2020] [Indexed: 02/08/2023] Open
Abstract
AIM To evaluate the effectiveness of Grand Seiko Ref/Keratometer WAM-5500 compared to Topcon KR800 autorefractor in detecting refractive error in large scale vision screening for Chinese school age children with the WHO criteria. METHODS A total of 886 participants were enrolled with mean age of 9.49±1.88y from Tianjin, China. Spherical equivalent (SE) was obtained from un-cycloplegic autorefraction and cycloplegic autorefraction. Topcon KR 800 (Topcon) and Grand Seiko WAM-5500 (WAM) autorefractors were used. Bland-Altman Plot and regression were generated to compare their performance. The overall effectiveness of detecting early stage refractive error was analyzed with receiver operating characteristic (ROC) curves. RESULTS The mean SE was -0.98±1.81 diopter (D) and the prevalence of myopia was 48.9% defined by WHO criteria according to the result of cycloplegic autorefraction. The mean SE of un-cycloplegic autorefraction with Topcon and WAM were -1.21±1.65 and -1.20±1.68 D respectively. There was a strong linear agreement between result obtained from WAM and cycloplegic autorefraction with an R2 of 0.8318. Bland-Altman plot indicated a moderate agreement of cylinder values between the two methods. The sensitivity and specificity for detecting hyperopia were 90.52% and 83.51%; for detecting myopia were 95.60% and 90.24%; for detecting astigmatism were 79.40% and 90.21%; for detecting high myopia were 98.16% and 98.91% respectively. CONCLUSION These findings suggest that both Grand Seiko and Topcon autorefractor can be used in large-scale vision screening for detecting refractive error in Chinese population. Grand Seiko gives relatively better performance in detecting myopia, hyperopia, and high myopia for school age children.
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Affiliation(s)
- Di Wang
- Tianjin International Joint Research and Development Centre of Ophthalmology and Vision Science, Eye Institute and School of Optometry, Tianjin Medical University Eye Hospital, Tianjin 300384, China
| | - Nan Jin
- Tianjin International Joint Research and Development Centre of Ophthalmology and Vision Science, Eye Institute and School of Optometry, Tianjin Medical University Eye Hospital, Tianjin 300384, China
| | - Ru-Xia Pei
- Tianjin International Joint Research and Development Centre of Ophthalmology and Vision Science, Eye Institute and School of Optometry, Tianjin Medical University Eye Hospital, Tianjin 300384, China
| | - Li-Qiong Zhao
- Tianjin International Joint Research and Development Centre of Ophthalmology and Vision Science, Eye Institute and School of Optometry, Tianjin Medical University Eye Hospital, Tianjin 300384, China
| | - Bei Du
- Tianjin International Joint Research and Development Centre of Ophthalmology and Vision Science, Eye Institute and School of Optometry, Tianjin Medical University Eye Hospital, Tianjin 300384, China
| | - Gui-Hua Liu
- Tianjin International Joint Research and Development Centre of Ophthalmology and Vision Science, Eye Institute and School of Optometry, Tianjin Medical University Eye Hospital, Tianjin 300384, China
| | - Xi-Lian Wang
- Tianjin Beichen District Hospital of Traditional Chinese Medicine, Tianjin 300400, China
| | - Rui-Hua Wei
- Tianjin International Joint Research and Development Centre of Ophthalmology and Vision Science, Eye Institute and School of Optometry, Tianjin Medical University Eye Hospital, Tianjin 300384, China
| | - Xiao-Rong Li
- Tianjin International Joint Research and Development Centre of Ophthalmology and Vision Science, Eye Institute and School of Optometry, Tianjin Medical University Eye Hospital, Tianjin 300384, China
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Przekoracka-Krawczyk A, Michalak KP, Pyżalska P. Deficient vergence prism adaptation in subjects with decompensated heterophoria. PLoS One 2019; 14:e0211039. [PMID: 30657792 PMCID: PMC6338415 DOI: 10.1371/journal.pone.0211039] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2018] [Accepted: 01/07/2019] [Indexed: 11/26/2022] Open
Abstract
Vergence prism adaptability was evaluated in subjects with high symptomatic and asymptomatic heterophoria and compared to individuals with a heterophoria within normal range (the control group). A computer haploscope was used to measure phoria values and changes in the eye position after introducing 6 prism diopters base out in front of the right eye. Phoria values were measured with a nonius paradigm every minute for a period of 10 minutes during adaptation. The results showed that subjects with symptomatic heterophoria are characterized by a lower rate of prism adaptation and adapted to a smaller extent with respect to the control group. The group with high but asymptomatic heterophoria showed prolonged adaptation time but after several minutes of binocular viewing the subjects were able to adapt to the prism to a level similar to the control group. These findings suggest that an impairment in the slow vergence control system may be responsible for the inability to fully reduce vergence effort, which results in poor vergence ranges and asthenopic symptoms during prolonged viewing.
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Affiliation(s)
- Anna Przekoracka-Krawczyk
- Laboratory of Vision Science and Optometry, Faculty of Physics, Adam Mickiewicz University, Poznań, Poland
- Vision and Neuroscience Laboratory, NanoBioMedical Centre, Adam Mickiewicz University, Poznań, Poland
- * E-mail:
| | - Krzysztof Piotr Michalak
- Laboratory of Vision Science and Optometry, Faculty of Physics, Adam Mickiewicz University, Poznań, Poland
- Vision and Neuroscience Laboratory, NanoBioMedical Centre, Adam Mickiewicz University, Poznań, Poland
| | - Paulina Pyżalska
- Laboratory of Vision Science and Optometry, Faculty of Physics, Adam Mickiewicz University, Poznań, Poland
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Abstract
PURPOSE Previous studies of dark focus have found evidence of a propinquity response, in which subjects accommodate to the perceived distance of their surroundings despite being in absolute darkness. Their distance perception in a lighted room allows a spatial representation to persist within the darkened room. This study sought to establish the significance and magnitude of the propinquity response in a large sample of young adults, and to determine whether the propinquity response can be predicted by a subject's initial dark focus in an unknown dark room. METHODS Dark focus was measured with a dynamic infrared optometer (Plusoptix PowerRef 3) in 30 young adult subjects, 26 of whom were naive to the testing room and its dimensions. Dark focus was then measured at varying dioptric wall distances of 0.25-4D. The subject viewed the lighted room before each measurement. For each individual, the dark focus was plotted as a function of dioptric wall distance. The slope of this function was used as a measure of the propinquity response. RESULTS The mean initial dark focus value was 1.05D (SD 1.04D) for the 26 naive subjects. The mean slope of the plot of dark focus as a function of dioptric wall distance was small (+0.097), yet highly statistically significant (P = .0002). The propinquity response function showed no statistically significant quadratic or cubic trends, and so may be considered linear. No statistically significant correlation was found between naive dark focus and propinquity response (r = +0.246, P = .226). CONCLUSIONS Propinquity seems to be a small but statistically significant factor in dark focus measurements. Though it is unlikely to contaminate tonic accommodation measurements in large samples under normal laboratory conditions, a minority of individuals exhibit large propinquity responses equal to that of proximal accommodation in lighted conditions.
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Mallen EAH, Gilmartin B, Wolffsohn JS, Tsujimura SI. Clinical evaluation of the Shin-Nippon SRW-5000 autorefractor in adults: an update. Ophthalmic Physiol Opt 2015; 35:622-7. [DOI: 10.1111/opo.12254] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
| | | | | | - Sei-ichi Tsujimura
- Faculty of Science and Engineering; Kagoshima University; Kagoshima Japan
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The usefulness of the Retinomax autorefractor for childhood screening validated against a Danish preterm cohort examined at the age of 4 years. Eye (Lond) 2015; 29:742-7. [PMID: 25853445 DOI: 10.1038/eye.2015.14] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Accepted: 01/07/2015] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND AND PURPOSE Refractometers have gained a foothold in childhood screening for ophthalmic disorders. Given the results of an ophthalmic follow-up of an extremely preterm Danish cohort, the results of the Retinomax autorefractor were further evaluated. MATERIALS AND METHODS A nationwide cohort of infants born before gestational age 28 weeks (n=178) and 56 term controls were examined at the age of 4 years. Refraction was given as the cycloplegic Retinomax value. For this study, we analysed the equipment's confidence value on the printout and equipment-induced myopization (as the difference between refraction measured before and after topical cyclopentholate 1%), both items hypothetical with a view to having identified factual ophthalmic deviations. RESULTS Thirty-two of 42 eyes with visual acuity ≤0.4 had high Retinomax confidence values (8-9); the Retinomax values were also high in 10 of 12 children with strabismus and lack of stereopsis. Low values (1-6) were recorded in 11 single eyes, 5 of which were normal (false positives). Three children already known to have low vision were unable to cooperate. The overall mean value for equipment-induced myopization was 1.9 D (range, 0-6.87 D). Myopization showed no correlation with visual acuity and corneal curvature, and a weak positive correlation with refractive value disappeared when the myopic outliers were excluded. CONCLUSIONS The hand-held Retinomax seemed to be reliable for assessing refraction in 4-year-old children, provided a cycloplegic agent is applied; if used alone, the Retinomax would have missed several cases of ophthalmic deviation during screening. Equipment-induced myopization was not indicative.
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Thiagarajan P, Ciuffreda KJ. Effect of oculomotor rehabilitation on accommodative responsivity in mild traumatic brain injury. ACTA ACUST UNITED AC 2015; 51:175-91. [PMID: 24933717 DOI: 10.1682/jrrd.2013.01.0027] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Revised: 08/15/2013] [Indexed: 11/05/2022]
Abstract
Accommodative dysfunction is a common oculomotor sequelae of mild traumatic brain injury (mTBI). This study evaluated a range of dynamic (objective) and static (subjective) measures of accommodation in 12 nonstrabismic individuals with mTBI and near vision-related symptoms before and after oculomotor training (OMT) and placebo (P) training (6 wk, two sessions per week, 3 h of training each). Following OMT, the dynamics of accommodation improved markedly. Clinically, there was a significant increase in the maximum accommodative amplitude both monocularly and binocularly. In addition, the near vision symptoms reduced along with improved visual attention. None of the measures were found to change significantly following P training. These results provide evidence for a significant positive effect of the accommodatively based OMT on accommodative responsivity. Such improvement is suggestive of oculomotor learning, demonstrating considerable residual brain-visual system plasticity in the adult compromised brain.
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Affiliation(s)
- Preethi Thiagarajan
- Retina Foundation of the Southwest, 9600 N Central Expy, Ste 200, Dallas, TX 75231.
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Abstract
AIM To determine whether the convergence accommodation to convergence (CA/C) ratio during divergence with base-in (BI) prisms is of a similar or different magnitude to that measured during convergence with base-out (BO) prisms. METHODS Eighteen participants with normal binocular single vision were recruited. The participants viewed a pseudo-Gaussian target, which consisted of a light emitting diode (LED) behind a diffusing screen at 40 cm. After 5 minutes of dark adaptation, the refractive status of the eye was measured without any prism using a Shin-Nippon SRW-5000 autorefractor. The participant held the selected prism (5Δ or 10Δ BO or BI, counterbalanced) in front of their right eye and obtained a single, fused image of the target while refractive measures were taken with each. A 30-second rest period was given between measurements. The mean age of the participants was 20.6±3.22 years. RESULTS The mean CA/C ratios for the 5Δ BO, 10Δ BO, 5Δ BI, and 10Δ BI were 0.108 (±0.074) D/Δ, 0.110 (±0.056) D/Δ, 0.100 (±0.090) D/Δ, and 0.089 (±0.055) D/Δ, respectively. A 2-factor repeated measures ANOVA found that the CA/C ratio did not significantly change with differing levels of prism-induced convergence and divergence (p=0.649). CONCLUSIONS Change in accommodation induced by manipulating vergence is similar whether convergence or divergence are induced. The CA/C ratio did not show any change with differing levels of prism-induced convergence and divergence.
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Affiliation(s)
- Joshua M Simmons
- Academic Unit of Ophthalmology and Orthoptics, Faculty of Medicine, Dentistry and Health, University of Sheffield , Beech Hill Road, Sheffield, S10 2RX , UK
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Effect of heterophoria type and myopia on accommodative and vergence responses during sustained near activity in children. Vision Res 2012; 57:9-17. [DOI: 10.1016/j.visres.2012.01.011] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 01/16/2012] [Accepted: 01/17/2012] [Indexed: 11/18/2022]
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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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Abstract
PURPOSE Visual discomfort is a common problem, and our previous research indicated that 17% of college students experience moderate to high levels of discomfort when reading or studying. There have been several visual factors associated with visual discomfort, and in this study, we focused on measuring the near-induced transient myopia response in a group of college students with significant visual discomfort. METHODS Visual discomfort was evaluated with a survey developed by Conlon et al. (Conlon et al., Visual Cogn 1999;6:637-663). Twelve college students with high visual discomfort (scoring 1 SD higher than the mean value) and 12 college students with low visual discomfort (scoring within 0.5 SD of the mean value) participated in the study. All students had 20/25 or better visual acuity, no strabismus, and no significant uncorrected refractive error. All refractive error and accommodative measurements were made with the WAM-5500 autorefractor. A pretask distance refraction at 6 m was taken for 60 s, and then the students read a story for 10 min at 20 cm. After reading the passage, the posttask distance refraction was measured for 2 min at 6 m. Values for the pre- and posttask measures were averaged in 10-s blocks of time. RESULTS A mixed analysis of variance comparing discomfort group by pre- and postnear work distance refraction showed a significant interaction (p = 0.05). Comparing the means of the pre- and posttask distance refraction indicated that the high discomfort group showed no change in refractive error, but the low discomfort group showed a myopic shift of 0.13 diopter. CONCLUSIONS A near-induced transient myopia response is not associated with high visual discomfort experienced by college students when reading or doing near work.
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Sreenivasan V, Bobier W, Irving E, Lakshminarayanan V. Effect of Vergence Adaptation on Convergence–Accommodation: Model Simulations. IEEE Trans Biomed Eng 2009; 56:2389-95. [DOI: 10.1109/tbme.2009.2025962] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Vedamurthy I, Harrison WW, Liu Y, Cox I, Schor CM. The influence of first near-spectacle reading correction on accommodation and its interaction with convergence. Invest Ophthalmol Vis Sci 2009; 50:4215-22. [PMID: 19264892 DOI: 10.1167/iovs.08-3021] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Accommodation and convergence can adapt to blur and disparity stimuli and to age-related changes in accommodative amplitude. Does this ability decline with age? The authors investigated short-term adaptation to first near-spectacle reading correction on the accommodative-stimulus response (ASR) function, accommodative amplitude (AA), AC/A, and CA/C ratios in a pre-presbyopic and an incipient presbyopic population and determined whether changes in these functions recovered after discontinuation of the use of near spectacles. METHODS Thirty subjects with normal vision participated; their ages ranged from 21 to 30 years (n = 15) and 38 to 44 years (n = 15). Oculomotor functions were measured before and after single-vision reading spectacles were worn for near tasks over a 2-month period and then 2 months after the use of near spectacles was discontinued. RESULTS The slope of the ASR function and the AC/A and CA/C ratios did not change significantly after near spectacles were worn. There was a hyperopic shift of the ASR function that significantly reduced the near point of accommodation (NPA) and lowered the far-point refraction. These changes were age invariant and did not recover after 2 months of discontinuation of near spectacle wear. CONCLUSIONS These results imply that the NPA may be enhanced normally by tonic bias of accommodation that elevates the entire ASR function and produces myopic refraction bias. When this bias relaxes after reading spectacles are worn, there is a hyperopic shift of the refractive state and a reduction of the NPA, specified from optical infinity.
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Affiliation(s)
- Indu Vedamurthy
- School of Optometry, University of California at Berkeley, Berkeley, California 94720, USA
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Cohen Y, Zadok D, Barkana Y, Shochat Z, Ashkenazi I, Avni I, Morad Y. Relationship between night myopia and night-time motor vehicle accidents. ACTA ACUST UNITED AC 2007; 85:367-70. [PMID: 17335516 DOI: 10.1111/j.1600-0420.2006.00875.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE To investigate the relationship between night myopia and the occurrence of night-time motor vehicle accidents in a group of professional drivers. METHODS We examined 136 professional drivers. Refraction was determined in full illumination (100 cd/m2) and after sitting in darkness for 5 mins. The change in refraction, indicative of night myopia, was correlated with the number of motor vehicle accidents in which each driver was involved (detailed in their personal files) and with the results of a visual complaints questionnaire. RESULTS The mean age of the study group was 21.0 years. Mean spherical refraction changed from + 0.11 dioptres (D) in light to -0.17 D after dark adaptation for 5 mins. Night myopia was found in 34 drivers (25%), at a mean of -1.2 D (range -0.75 D to -3.50 D). There was no statistically significant difference between these drivers and the rest of the group in the results of the visual complaints questionnaire, or in the number of accidents occurring during the day. However, drivers with a myopic shift > 0.75 D were involved in more accidents at night than the rest of the group (p = 0.044). CONCLUSIONS In this study population, drivers with night myopia of > 0.75 D were more likely to be involved in night-time accidents. This may imply that selected groups of drivers should be examined for night myopia.
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Affiliation(s)
- Yuval Cohen
- Department of Ophthalmology, Assaf Harofeh Medical Centre, Tel Aviv University, Zrifin, Israel
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Schor CM, Bharadwaj SR, Burns CD. Dynamic performance of accommodating intraocular lenses in a negative feedback control system: a simulation-based study. Comput Biol Med 2006; 37:1020-35. [PMID: 16730691 DOI: 10.1016/j.compbiomed.2006.03.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2006] [Revised: 03/21/2006] [Accepted: 03/30/2006] [Indexed: 11/21/2022]
Abstract
A dynamic model of ocular accommodation is used to simulate the stability and dynamic performance of accommodating intraocular lenses (A-IOLs) that replace the hardened natural ocular lens that is unable to change focus. Accommodation simulations of an older eye with A-IOL materials having biomechanical properties of a younger eye illustrate overshoots and oscillations resulting from decreased visco-elasticity of the A-IOL. Stable dynamics of an A-IOL are restored by adaptation of phasic and tonic neural-control properties of accommodation. Simulations indicate that neural control must be recalibrated to avoid unstable dynamic accommodation with A-IOLs. An interactive web-model of A-IOL illustrating these properties is available at http://schorlab.berkeley.edu.
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Affiliation(s)
- Clifton M Schor
- Vision Science group, School of Optometry, University of California at Berkeley, Berkeley, CA 94720-2020, USA.
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Day M, Strang NC, Seidel D, Gray LS, Mallen EAH. Refractive group differences in accommodation microfluctuations with changing accommodation stimulus. Ophthalmic Physiol Opt 2006; 26:88-96. [PMID: 16390487 DOI: 10.1111/j.1475-1313.2005.00347.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE Microfluctuations of accommodation are known to increase in magnitude with increasing accommodation stimulus. Reduced sensitivity to blur in myopic subjects could also lead to increases in the magnitude of the microfluctuations. The aim of this study is to examine the effect of variations in accommodation stimulus upon the microfluctuations in different refractive groups. METHODS Thirty-six subjects were divided into three groups depending upon their refractive error and age of onset of their myopia; 12 emmetropes (EMMs), 12 early onset myopes (EOMs) and 12 late-onset myopes (LOMs). Steady-state accommodation responses were recorded continuously for 2 min using the Shin-Nippon SRW-5000 autorefractor at a sampling rate of 52 Hz while viewing targets at accommodation stimuli levels of 0, 1, 2, 3 and 4 D in a Badal (+5 D) optical system. RESULTS The EMMs and EOMs showed systematic increases in the root mean square (r.m.s.) value of the microfluctuations with increasing accommodation stimulus. In contrast, no systematic variation with accommodation stimulus was found for the LOMs. Power spectrum analysis demonstrated that increases in the size of the microfluctuations were mediated by increases in the power of the low frequency components of the accommodation response. CONCLUSIONS The magnitude of the microfluctuations in the EMMs and EOMs may be influenced primarily by accommodation response-induced zonular relaxation effects or to changes in the physical properties of the accommodation plant with increasing accommodation response. The LOMs may have an increased baseline neural blur threshold, which appears to modulate the magnitude of the accommodative microfluctuations for low accommodation levels. At higher accommodation demands, the changes in the physical properties of the accommodation plant or the zonular relaxation effects appear to exceed the blur threshold, and the known association between microfluctuations and accommodation stimulus level is restored.
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Affiliation(s)
- Mhairi Day
- Department of Vision Sciences, Glasgow Caledonian University, UK
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21
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Bharadwaj SR, Schor CM. Dynamic control of ocular disaccommodation: first and second-order dynamics. Vision Res 2006; 46:1019-37. [PMID: 16045960 PMCID: PMC1578507 DOI: 10.1016/j.visres.2005.06.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2005] [Revised: 05/24/2005] [Accepted: 06/03/2005] [Indexed: 11/15/2022]
Abstract
Velocity and acceleration characteristics provide valuable information about dynamic control of accommodation. We investigated velocity and acceleration of disaccommodation (near-far focusing) from three starting positions. Peak velocity and peak acceleration of disaccommodation increased with the proximity of starting position however for a given starting position they were invariant of response magnitude. These results suggest that all disaccommodation responses are initiated towards a constant primary destination and are switched mid-flight to attain the desired final position. Large discrepancies between the primary destination and desired final position appear to produce overshoots and oscillations of small responses from proximal starting positions.
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Affiliation(s)
| | - Clifton M. Schor
- School of Optometry, University of California at Berkeley, Berkeley, CA 94720, USA
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22
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Bharadwaj SR, Schor CM. Initial destination of the disaccommodation step response. Vision Res 2006; 46:1959-72. [PMID: 16427109 DOI: 10.1016/j.visres.2005.11.029] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2005] [Revised: 11/14/2005] [Accepted: 11/24/2005] [Indexed: 10/25/2022]
Abstract
Peak velocity and peak acceleration of disaccommodation step responses remain invariant of response magnitude for a constant starting position and they increase linearly with proximity of starting position. This suggests that disaccommodation response is initiated towards an initial (default) destination and is switched mid-flight to attain the desired final destination. The dioptric location of initial destination was estimated from the x-intercept of regression of peak velocity on response starting position. The x-intercept correlated well with subject's cycloplegic refractive state and poorly with their dark focus of accommodation. Altering the dark focus by inducing fatigue in the accommodative system did not alter the x-intercept. These observations suggest that cycloplegic refractive state is a good behavioral correlate of initial destination of disaccommodation step responses.
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Rounsley KJ, McFadden SA. Limits of visual acuity in the frontal field of the rock pigeon (Columba livia). Perception 2005; 34:983-93. [PMID: 16178153 DOI: 10.1068/p5205] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The eye of the rock pigeon is typical of a granivorous lateral-eyed bird, in that it has both a laterally projecting central fovea and a second high-density cellular area in peripheral retina (area dorsalis) which projects to the binocular frontal field below the beak. Such a dual system is faced with potentially different optical restraints arising from central and peripheral vision. We asked whether the frontal axis can support high resolution vision from a refractive resting position (predicted to be 25-33 cm; Fitzke et al, 1985 Journal of Physiology 369 33-44) to some near point of accommodation. We measured the visual acuity on the frontal axis in five pigeons using an operant discrimination of high-contrast square-wave gratings at a series of distances from 7 to 80 cm from the eye. The peak average acuity was 11.04 cycles deg(-1), which occurred 10 cm from the eye. The average of the maximum acuity of each bird at 10 cm was 12.8 +/- 1.1 cycles deg(-1), a value equal to the Nyquist frequency calculated from the peak ganglion cell density of the area dorsalis. However, this maximum acuity was restricted to a narrow depth in space, located around 10 cm from the eye, and at greater distances fell exponentially such that acuity was 50% of its maximum at 35 cm and less than 1 cycle deg(-1) at 100 cm. We propose that the range of high-acuity vision is limited in the frontal field by either increased refractive power and/or inaccuracy in frontal accommodation, and is optimized for a preferred far point located 10 cm from the eye.
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Affiliation(s)
- Kevin J Rounsley
- School of Behavioural Sciences, Faculty of Science and IT, University of Newcastle, Newcastle, NSW 2308, Australia
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24
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Schmid KL, Hilmer KS, Lawrence RA, Loh SY, Morrish LJ, Brown B. The effect of common reductions in letter size and contrast on accommodation responses in young adult myopes and emmetropes. Optom Vis Sci 2005; 82:602-11. [PMID: 16044072 DOI: 10.1097/01.opx.0000171337.02376.60] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
PURPOSE Accommodation errors during reading and the subsequent near work-induced transient myopia (NITM) that occurs have been implicated in the development and progression of myopia. This study investigated the effects of two letter variables, size and contrast, on accommodation accuracy during the near task and on NITM and its subsequent decay. These were varied so as to mimic what might occur when students photocopy and reduce reading materials. METHODS Based on their refractive errors, young adult subjects (18-25 years) were classified into three groups: emmetropes (n = 19), stable myopes (n = 17), and progressing myopes (n = 17). Three print sizes (N4, N6, and N8) and two print contrasts (90% and 60%) were used to give six different reading targets. Targets were presented in random order at 25 cm (4 D demand) and the text read for comprehension for 3 minutes. For each target, accommodation accuracy and NITM and its decay were measured using the free space Shin-Nippon SRW-5000 autorefractor. RESULTS When data for all subjects were pooled, there was a significant effect of letter size (p = 0.030) but not contrast (p = 0.898) on accommodation accuracy; however, differences were small and unlikely to be clinically relevant. NITM (p = 0.033) and its decay (p = 0.012) also varied with letter size. NITM was greater and decay longer for larger letters. We found no effect of refractive error group on accommodation accuracy. In contrast, there was a significant difference in the magnitude of NITM and its decay for emmetropic and myopic subjects (although no effect of progression status); myopes had larger NITM values and longer decay times to baseline than emmetropes (NITM myopes: 0.37 +/- 0.14D vs. emmetropes: 0.19 +/- 0.17 D, p = 0.005; decay time myopes: 15.12 +/- 6.58 seconds vs. emmetropes 7.10 +/- 4.82 seconds, p = 0.0045). The differences in NITM and its decay between the two refractive groups were of similar magnitude for all six combinations of letter size and contrast. CONCLUSIONS Our data do not support the suggestion that common reductions in letter size or contrast of reading material (as might occur for photocopied reading materials) cause greater accommodation inaccuracy and greater near work-induced adaptation effects that would exacerbate myopia development in young adults.
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Affiliation(s)
- Katrina L Schmid
- Centre for Health Research, School of Optometry, Queensland University of Technology, Brisbane, Australia.
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25
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Chen JC, Schmid KL, Brown B, Edwards MH. The effect of a beta-adrenoceptor antagonist on accommodative adaptation in Hong Kong children. Curr Eye Res 2005; 30:179-88. [PMID: 15804743 DOI: 10.1080/02713680490908571] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
PURPOSE Increased susceptibility to nearwork-induced accommodative adaptation has been suggested as a risk factor for myopia development. We investigated whether accommodative adaptation may explain in part the high prevalence of myopia in Hong Kong children and examined the effect of beta-antagonism with topical timolol maleate on accommodative adaptation. METHODS Thirty children (10 emmetropes and 20 myopes) aged between 8 and 12 years were recruited. Tonic accommodation was measured before and after 5 min of video game-playing using an open-field Shin-Nippon autorefractor. Measurements were repeated 30 min after timolol instillation. RESULTS Children with progressing myopia demonstrated accommodative adaptation following the near task, whereas stable myopes showed counter-adaptive, hyperopic accommodative changes. Timolol increased the magnitude of accommodative adaptation in the stable myopes but had little effect on responses of the progressing myopes or emmetropes. CONCLUSIONS Neuropharmacological modulation of the accommodative system may have a possible etiological role in the progression of myopia.
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Affiliation(s)
- Jennifer C Chen
- Centre for Health Research, School of Optometry, Queensland University of Technology, Brisbane, Australia.
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26
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Rozhkova GI, Podugolnikova TA, Vasiljeva NN. Visual acuity in 5-7-year-old children: individual variability and dependence on observation distance. Ophthalmic Physiol Opt 2005; 25:66-80. [PMID: 15649185 DOI: 10.1111/j.1475-1313.2004.00263.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Accurate measurements of uncorrected binocular and monocular visual acuity were performed in 65 children aged 5-7 years at five viewing distances in the range 0.5-5.0 m by means of the test charts containing widely spaced E stimuli in four orientations. It was found that, in most children of this age, visual acuity (V) changed with test distance, as had been reported previously with older subjects. Visual acuity could be considered as practically independent of observation distance (Vmax-Vmin<or=0.2 decimal units) in <50% of children. The remaining children demonstrated evident distance dependence of visual acuity but the shape of the acuity-distance curve varied. The acuity-distance curve of most children peaked at an intermediate distance (1-2 m), the typical difference Vmax-Vmin being 0.4 decimal units. To explain the existence of an optimal observation distance in the majority of children, a number of developmental and environmental factors could be proposed that adjust the parameters of the visual system to the parameters of operational visual space and prevailing activity.
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Affiliation(s)
- Galina I Rozhkova
- Institute for Information Transmission Problems, Russian Academy of Sciences, Bolshoi Karetnyi per., 19, 127994 Moscow, Russia.
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27
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Kruger PB, Rucker FJ, Hu C, Rutman H, Schmidt NW, Roditis V. Accommodation with and without short-wavelength-sensitive cones and chromatic aberration. Vision Res 2004; 45:1265-74. [PMID: 15733959 DOI: 10.1016/j.visres.2004.11.017] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2004] [Revised: 11/08/2004] [Accepted: 11/15/2004] [Indexed: 11/28/2022]
Abstract
Accommodation was monitored while observers (23) viewed a square-wave grating (2.2 cycles/deg; 0.53 contrast) in a Badal optometer. The grating moved sinusoidally (0.2 Hz) to provide a stimulus between -1.00 D and -3.00 D during trials lasting 40.96 s. There were three illumination conditions: 1. Monochromatic 550 nm light to stimulate long-wavelength-sensitive cones (L-cones) and medium-wavelength-sensitive cones (M-cones) without chromatic aberration; 2. Monochromatic 550 nm light+420 nm light to stimulate long-, medium- and short-wavelength-sensitive cones (S-cones) with longitudinal chromatic aberration (LCA); 3. Monochromatic 550 nm light+420 nm light to stimulate L-, M- and S-cones viewed through an achromatizing lens. In the presence of LCA mean dynamic gain decreased (p=0.0003; ANOVA) and mean accommodation level was reduced (p=0.001; ANOVA). The reduction in gain and increased lag of accommodation in the presence of LCA could result from a blue-yellow chromatic signal or from a larger depth-of-focus.
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Affiliation(s)
- Philip B Kruger
- Schnurmacher Institute for Vision Research, State College of Optometry, State University of New York, 33 West 42nd Street, New York, NY 10036, USA.
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28
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Kruger PB, Stark LR, Nguyen HN. Small foveal targets for studies of accommodation and the Stiles–Crawford effect. Vision Res 2004; 44:2757-67. [PMID: 15342220 DOI: 10.1016/j.visres.2004.06.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2003] [Revised: 06/15/2004] [Indexed: 10/26/2022]
Abstract
The properties of small monochromatic targets as accommodative stimuli are not well understood. We used a dynamic optometer to record accommodation responses to monochromatic disc targets (1.0-27.3 min arc) and to a Maltese cross. Accommodation responded adequately to points as small as 13.6 min arc. The response to these small targets is relevant to the question of whether the Stiles-Crawford (SC) effect could provide a stimulus to accommodation. Previous studies have used pupil apodizing filters to neutralise the natural SC function and so determine how visual performance or accommodation is influenced by the SC effect. However, these filters cannot correct for known inhomogeneities in the SC function across the retina for extended targets. Therefore, we calculated the SC function inhomogeneities across the retinal image of a smaller 13.6-min arc target. Unfortunately, even this small target is too large to permit a homogenous SC function across its extent. Alternatives to the apodizing filter approach are discussed.
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Affiliation(s)
- Philip B Kruger
- Schnurmacher Institute for Vision Research, College of Optometry, State University of New York, 33 West 42 Street, New York, NY 10036, USA.
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Abstract
PURPOSE When the targets or the background in a display are different colors, longitudinal chromatic aberration ensures that there is no single correct accommodative response. The purpose of the present study was to determine whether the response becomes more variable when viewing certain multicolor displays. METHODS Accommodative responses of five young participants were measured with a dynamic infrared optometer while they viewed steady targets at a nominal stimulus level of 3 D. Target-on-background color combinations were black on white, black on blue, black on red, blue on red, red on blue, dark blue on red, and dark red on blue. RESULTS When compared with the standard black-on-white target, responses to targets with reduced spectral bandwidth were not significantly more variable. In most participants, responses to near-isoluminant targets (e.g., red on blue and blue on red) were not more variable than to the standard target. However, calculated confidence intervals cannot rule out moderate to large changes in variability near isoluminance. Responses to these multicolor targets tended to favor the blue focus. CONCLUSIONS In most individuals, viewing multichromatic targets does not increase significantly the variation in accommodative response as compared with broadband black-and-white targets.
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Affiliation(s)
- David A Atchison
- School of Optometry, Queensland University of Technology, Kelvin Grove, Queensland, Australia.
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30
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Ting PWK, Lam CSY, Edwards MH, Schmid KL. Prevalence of Myopia in a Group of Hong Kong Microscopists. Optom Vis Sci 2004; 81:88-93. [PMID: 15127927 DOI: 10.1097/00006324-200402000-00006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
PURPOSE To study the prevalence and magnitude of myopia in a group of Hong Kong Chinese microscopists and compare it with that observed in microscopists working in the United Kingdom. METHODS Forty-seven microscopists (36 women and 11 men) with a median age of 31 years and working in hospital laboratories throughout Hong Kong were recruited to the study. Information about past refractive corrections, microscopy work, and visual symptoms associated with microscope use were collected. All subjects had a comprehensive eye examination at The Hong Kong Polytechnic University Optometry Clinic, including measures of refractive error (both noncycloplegic and cycloplegic), binocular vision functions, and axial length. RESULTS The prevalence of myopia in this group of microscopists was 87%, the mean (+/- SD) refractive error was -4.45 +/- 3.03 D and mean axial length was 25.13 +/- 1.52 mm. No correlation was found between refractive error and years spent working as a microscopist or number of hours per day spent performing microscopy. Subjects reporting myopia progression (N = 22) did not differ from the refractively stable group (N = 19) in terms of their microscopy working history, working hours, tonic accommodation level, or near phoria. However, the AC/A ratio of the progressing group was significantly greater than that of the stable group (4.59 delta/D cf. 3.34 delta/D). CONCLUSION The myopia prevalence of Hong Kong Chinese microscopists was higher than that of microscopists in the United Kingdom (87% cf. 71%), as well as the Hong Kong general population (87% cf. 70%). The average amount of myopia was also higher in the Hong Kong Chinese microscopists than the Hong Kong general population (-4.45 D cf. -3.00 D). We have confirmed that the microscopy task may slightly exacerbate myopia development in Chinese people.
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Affiliation(s)
- Patrick W K Ting
- Centre for Myopia Research, Department of Optometry and Radiography, The Hong Kong Polytechnic University, Hong Kong.
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31
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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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Stark LR, Atchison DA. Effect of an intervening screen on accommodation to a distant object. Clin Exp Optom 1998; 81:119-130. [PMID: 12482261 DOI: 10.1111/j.1444-0938.1998.tb06730.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/26/1998] [Indexed: 11/27/2022] Open
Abstract
Background: An intervening screen has been suggested to induce an inward shift of accommodation when viewing a distant object. This is an example of the Mandelbaum effect. However, there have been no objective measures of the magnitude of this effect in this particular situation. Methods: Accommodation was recorded with an infra-red optometer, while subjects (n = 16) viewed a distant letter target with or without an intervening screen. Screens were placed near the individual dark focus distance or at 50 cm. In a second experiment the contrast of the distant target was varied and subjects (n = 5) viewed the target directly or through a screen placed near the individual dark focus distance. Results: In the main experiment, the Mandelbaum effect was not significantly different from zero and was less than 0.5 D in every subject. In addition, accommodation was not more variable when viewing through the screen. However, it may be that some subjects do demonstrate a Mandelbaum effect while others do not. The individual dark focus level did not predict susceptibility to the Mandelbaum effect for a screen at the dark focus. Subjects reported their perceptions of the tasks and some noted changes in the perceived distances of objects when viewing through a screen. In the second experiment, the Mandelbaum effect (< 0.6 D) did not vary with distant target contrast. Conclusions: When viewing a distant object through a screen there is a small (< 0.6 D) or negligible inward shift of accommodation.
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Affiliation(s)
- Lawrence R Stark
- Centre for Eye Research, School of Optometry, Queensland University of Technology, Queensland, Australia
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Hung GK. Sensitivity analysis of the stimulus-response function of a static nonlinear accommodation model. IEEE Trans Biomed Eng 1998; 45:335-41. [PMID: 9509749 DOI: 10.1109/10.661158] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The effect of parameter variation of a nonlinear static feedback control model of the accommodation system was investigated. Simulations of a MATLAB/SIMULINK model showed a nonlinear relationship between stimulus and response in which the response curve was above the 1:1 line in the region to the left of the crossover and below the 1:1 line in the region to the right of the crossover. At the crossover, the response curve exhibited an inflection that was constant and equal to the tonic accommodation value (ABIAS). Sensitivity analysis showed that increasing depth of focus (deadspace range between +/- DSP) increased the separation between the boundary lines of the deadspace region, with a larger separation associated with late-onset myopia and congenital nystagmus. Increasing accommodative controller gain (ACG) increased the slope of the function on either side of the deadspace, with lower ACG values corresponding to lower slopes that indicated an amblyopic deficit. Increasing ABIAS increased the accommodative level at the inflection region. In addition, the saturation level of the accommodative response decreased with increasing age, while the slope remained the same, which was consistent with the Hess-Gullstrand theory of presbyopia. The accuracy and relative simplicity of the model indicated that it could serve as a basis for further comprehensive investigation of the basic and clinical aspects of the accommodation system.
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Affiliation(s)
- G K Hung
- Department of Biomedical Engineering, Rutgers University, Piscataway, NJ 08854-8014, USA
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Abstract
The literature on nearwork-induced transient myopia (NITM) is reviewed, with NITM being defined as the short-term myopic far point shift immediately following a sustained near visual task. A majority of these investigations demonstrated the presence of NITM for a variety of test parameters, e.g., visual acuity, contrast sensitivity and far point. Overall, these studies reported relatively small myopic shifts, with a mean of approximately 0.40 D and a range from 0.12 to 1.30 D. The subsequent decay is characterized by an exponential function with a relatively short time course. While the precise etiology and implications of NITM remain unclear, speculations regarding its origin and relevance to clinical myopia are discussed. Studies that did not demonstrate NITM are also reviewed.
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Affiliation(s)
- E Ong
- SUNY/State College of Optometry, Department of Vision Sciences, New York City, USA
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