title: A new specialized visual acuity chart for amblyopic children aged 3-5 years old: development and its clinical applications.
abstract: OBJECTIVE
  To introduce a new specialized visual acuity chart for amblyopic children aged 3-5 years old and its clinical applications.
  
  
  METHODS
  The new visual acuity chart and notations were designed based on Weber-Fechner law. The optotypes were red against a white background and were specially shaped four basic geometric symbols: circle, square, triangle, and cross. A regular geometric progression of the optotype sizes and distribution was employed to arrange in 14 lines. The progression rate of the optotype size between two lines was 1.2589 and the testing distance was 3m. Visual acuity score could be recorded as logMAR notation or decimal notation. Age-stratified diagnostic criteria for amblyopia established by consensus statement on diagnosis of amblyopia (2011) among members of the Strabismus and Pediatric Ophthalmology Group, Ophthalmology Society, Chinese Medical Association (SPOGOSCMA) were illustrated in the new visual acuity chart.
  
  
  RESULTS
  When assessing visual acuity in children aged 3-5 years old, this new visual acuity chart that consists of four symmetrical shapes (triangle, square, cross, and circle) overcame an inability to recognize the letters of the alphabet and difficulties in designating the direction of black abstract symbols such as the tumbling 'E' or Landolt 'C', which the subjects were prone to lose interest in. The visual acuity score may be recorded in different notations: decimal acuity and logMAR. These two notations can be easily converted each other in the new eye chart. The measurements of this new chart not only showed a significant correlation and a good consistency with the international standard logarithmic visual acuity chart (r=0.932, P<0.01), but also indicated a high test-retest reliability (89% of retest scores were within 0.1logMAR units of the initial test score).
  
  
  CONCLUSIONS
  The results of this study support the validity and reliability of distance visual acuity measurements using the new eye chart in children aged 3 to 5 years over a wide range of visual acuities, and the new eye chart is great for early detection of amblyopia. It can be applied in various clinical settings.
authors.affiliation: Biomedical Engineering Institute of Xi'an Jiaotong University, Xi'an 710049, Shaanxi Province, China.
authors.forename: Yang-Qing
authors.initials: YQ
authors.lastname: Huang
authors.affiliation: Yijishan Hospital of Wannan Medical College, Wuhu 241001, Anhui Province, China.
authors.forename: He
authors.initials: H
authors.lastname: Huang
authors.affiliation: Department of Ophthalmology, the Second People's Hospital of Anqing, Anqing 246004, Anhui Province, China.
authors.forename: Rong-Zhi
authors.initials: RZ
authors.lastname: Huang
keywords: Weber-Fechner law; amblyopic children; international standard logarithmic visual acuity chart