Objective:To investigate if the dynamic optotype is comparable with conventional logarithm of the minimum angle of resolution (LogMAR) optotype.Methods:This is a cross-sectional study investigating visual acuity measurement with two methods.The study lasted for 6 months from May to November 2017.One hundred and fifty subjects (150 right eyes) with age (58.7±14.3) years were recruited in the Optometry Clinics of the School of Optometry, The Hong Kong Polytechnic University.Habitual distance visual acuity of each eye was measured with a 3-meter LogMAR E chart and a Dyop ? acuity chart displayed on a monitor placed at 6 meters, respectively.Subjects were asked to comment on the Dyop ? system regarding the overall speed and ease of understanding the test using a 5-point Likert scale.The agreement between the two charts was assessed.This study was approved by an Ethics Committee of The Hong Kong Polytechnic University (No.HSEARS20170215006) in accordance with the Declaration of Helsinki, and written information consent was obtained from all the subjects prior to any ocular examination. Results:The mean difference between the LogMAR E chart and Dyop ? system was (0.05±0.07) LogMAR units, and the 95% limits of agreement was -0.09 to 0.19.The intra-class correlation coefficient of the two methods was 0.957.In general, 70% (105/150) of the subjects considered the Dyop ? system fast and 81% (121/150) easy to understand. Conclusions:Visual acuity measured by the Dyop ? system is comparable to the traditional LogMAR E chart.

Objective To analyze the causes of visual impaired and explore the visual improvement with aids,application effects and problems.Methods A series of cases study was adopted.Seven hundred and ninetyseven patients with visual impairment were selected from January 2012 to December 2016 in Tianjin Medical University Eye Hospital.The etiological analysis,visual function evaluation and visual aids fitting were performed for 797 patients with visual impairment.After 6 months,400 patients were randomly selected for follow-up,and application effects,daily use time and the reasons for abandon were evaluated and analyzed.This study followed the Helsinki declaration and was approved by Ethic Committee of the Tianjin Medical University Eye Hospital.Results The causes for top three in 797 visual impairment patients were high myopia,congenital eye diseases and diabetic retinopathy respectively.With distant optical visual aids,distance vision of the patients was significantly improved.Thereinto,66.3％ patients used visual aids occasionally every day.The overall effective rate of visual aids fitting was 86.92％,the efficiency of electronic visual aids is obviously higher than that of other near optical visual aids,and the use effect evaluation of electronic aids is also the best.It is found that poor vision,inconvenient use and inability to use are common influencing factors,among which poor vision is the main reason.Conclusions High myopia has become the leading cause of visual impairment.Professional visual aids fitting can greatly improve residual vision and effectiveness of visual aids.During the process of application,most of the patients usually don't use the devices for longer duration due to severe eye diseases.Once visual aids meet the patients' visual demands in a certain,they work effectively.