Objective To investigate the impact of text size and presentation speed of words on accommodative response in various simulated reading condition.Methods Twenty-four emmetropes were required to read Chinese novels presented by rapid serial visual presentation in one character on a computer screen at a distance of 33cm.Accommodative responses of the righteye were measured by using a Grand Seiko WV-500 autorefractor.Character sizes of 20 point and 9 point were presented in the speed from 50,100,150,200,and 250 to 300 characters/minute.Results Despite large inter-subject variability,the accommodative lag significantly decreased with increasing presenting speed(P=0.000).There were no significant differences of accommodative responses between the two character sizes(P0.466).Conclusions The decreased accommodative lag caused by the faster presenting speed,which may be linked to the reading and the myopia developing.
Key words:
Reading; Accommodative Response; RSVP; Myopia
Background Image clarity during near work is influenced by several factors,such as accommodative lag,pupil size and monochromatic aberrations.Since image clarity during extended reading at near distance has been cited as a possible inducement of myopia in childhood and a possible difference between myopic and emmetropic people throughout life,it is important to examine these factors in myopic and emmetropic myopic juvenile during reading at near distance. Objective The aim of this study was to investigate the relationships among wavefront aberrations,accommodative response and pupil size in early onset and progressive myopes eyes under the different reading status and explore the possible mechanism of the development of myopia as well. Methods Fiflyseven subjects aged from 12 to 16 years were enrolled and grouped as emmetropes,the onset of myopes and progressive myopes.Reading material were Chinese novels presented by rapid serial visual presentation at a distance of 25 cm. Accommodative response and pupil size were recorded by a Grand Seiko WV-500 autorefractor.The Image J software was used to calculate the pupil diameter.Wavefront aberrations were then measured with a WASCA wavefront analyzer. Results Aberrations and accommodative response showed large inter-subjeet variability.With accommodative stimulus of 4 diopter,the accommodative lag in the early-onset of myopes group and progressive myopes group were ( 1.72 ±0. 53) D and ( 1.74 ±0. 44) D, showing larger value in comparison with ( 0. 96 ±0. 55) D of emmetropes group( t＝4.25 ,t=4.47 ,P 0. 05). The mean value of pupil diameter, total RMS value, high-order RMS value, spherical aberration and coma were all significantly reduced with the stimulus varied from 0 D to 4 D( P 0. 05). Conclusion The early-onset of myopes and progressive myopes had larger accommodative lag. The lower sensitivity to defocus at near reading distance,inducing the larger accommodative lag and hyperopic defocus may be linked to the developing myopia.
Key words:
Myopia; Wavefront aberration ; Accommodative response ; Pupil size
The optometrist education system in the United States has a history of more than 100 years and has become a complete and mature system. It contains five parts: optometry admission test (OAT); a complete curriculum of optometry, including basic medical lectures, optometric theories and skills, large amount of clinical practices; the National Board Exam of Optometry (NBEO) which is mandatory for every licensed optometrist/practitioner, a one-year optional resident program; continue education in every year for renewing optometric licenses. We analyzed differents such as the enrollment requirements, the training time, the graduation requirements and the career perspective of the optometry education system between China and the United States were analyzed, we want to develop a optometrist training system with Chinese characteristics.
Key words:
Optometry; Optometrist; Medical education; The United States
Objective To investigate the differences in contrast visual acuity (CVA) under both bright and dark conditions in recent-onset myopic,progressive myopic and emmetropic teenagers; to investigate the correlation between CVA and wavefront aberration,together with pupil size; to study the possible mechanisms involved.Methods A cross-sectional trial design was used in this study.CVA was measured in 58 left eyes from 58 teenagers aged from 12 to 16 yeats.They were divided into 3 groups:emmetropes,18 subjects,with an average spherical equivalent refractive error (SER)of (0.00±0.20)D; recent onset myopes,21 subjects,with an average SER of (-1.03±0.33)D; and progressive myopes,19 subjects,with an average SER of (-2.67±0.77)D.All subjects underwent CVA testing with full spectacle correction under both bright and dark conditions with a Multi-Functional Visual Acuity Analyzer (MFVA-100).Pupil size and monochromatic wavefront aberration were measured with a real-time image recording system and a Hartmann-Shack wavefront aberrometer.Data were analyzed using paired samples t test,repeated measure variance analysis,one-way ANOVA and Pearson correlation.Results Myopes had a lower CVA than emmetropes.And recent-onset myopes had a lower CVA than progressive myopes and emmetropes (F=199.17,234.54,P＜0.01),especially under low contrasts (25％,10％) and dark conditions.Root mean square (RMS) values of total aberrations (C2-C7 without C20) and total higher-order aberrations (HOA),spherical aberration and coma increased significantly with a pupil in dark light [(0.205±0.108)μm,(0.101±0.057)pm,(0.028±0.039)μm and (0.066±0.056)μm] than with a pupil in bright light [(0.599±0.257)μm,(0.355±0.141)μm,(0.148±0.122)μm and (0.195±0.034)μm) (t=14.94,16.71,7.89,6.28,P＜0.05).There was no significant difference in the RMS values of HOA between emmetropes and myopes.Except for under bright and 100％ contrast conditions,CVA had significant negative correlation with HOA,no correlation was found between aberration,pupil and CVA for all the groups under bright or dark conditions.Conclusion The CVA in recent-onset myopic teenagers was lower than both progressive myopic and emmetropic teenagers,especially under dark conditions and low contrasts.So far there is not enough evidence to show that the decrease in CVA in recent-onset myopes is related to pupil size and the deterioration of retinal image quality causcd by wavefront aberrations.We assume that cortical factors may play the major role in this phenomenon.
Key words:
Contrast; Visual acuity; Aberration ; Pupil; Photic stimulation
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